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Sample records for multiwavelength blazar analysis

  1. Multiwavelength Observations of Blazars

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita

    2007-01-01

    The last decade has seen formidable progress in our understanding of blazar jets, thanks to the advent of several higher-sensitivity observatories. I will review the status of the art for blazar jets focusing especially on the latest multiwavelength campaigns.

  2. Multiwavelength Blazar Studies

    NASA Technical Reports Server (NTRS)

    Kafatos, Menas

    1997-01-01

    The present report concerns the following projects 'High energy emission from hot accretion disks from active galactic nuclei'; 'OSSE spectral timing and monitoring observations of Cygnus X- 1'; 'OSSE observations of blazars'; and 'Search for correlated time variations of bright EGRET blazars'. The most favored model for the central engine inAGNs is the supermassive black hole hypothesis (Rees 1978). The observed luminosities range from approx. 10 logical and 44-45 erg /s for objects such as Mk 421 and Seyferts to as much as approx. 10logical and 47 for powerful QSOs such as 3C 273 and 3C 279, a large fraction of the observed bolometric luminosity being, in all likelihood, beamed. As such, these objects are strong X-ray emitters (cf. Makino et al. 1987) and often undergo gamma-ray flaring detected at the EGRET range (Hartman et al. 1992) and in the case of one of two known nearby BL Lacs, Mk 421, at TeV energies as well (Punch et al. 1992, Macomb et al. 1995). Previous campaigns emphasizing radio through X-ray and even gamma-ray observations have generally found that the multiwavelength spectrum is adequately fit by a standard synchrotron self-Compton (SSC-cf. Jones et al. 1974) model of a relativistic jet (e.g. Makino et al. 1987 and Macomb et al. 1995 for the BL Lac object Mk 421) or inhomogeneous relativistic jet (Mufson et al 1990). It also was examined the gamma-gamma transperency constraints inblazars.

  3. Blazar Demographics Using Multiwavelength Data

    NASA Astrophysics Data System (ADS)

    Mao, Peiyuan; Massaro, F.; Urry, C. Megan

    2016-01-01

    Blazars are ideal laboratories to study relativistic jets in AGN, which are thought to be an important channel for feeding energy into galaxies and clusters. We present multi-wavelength SEDs of 2214 blazars with known redshifts, based on the Roma-BZCAT data across 12 frequency bands ranging from radio to gamma-ray. We confirm the anti-correlation between radio luminosity and synchrotron peak frequency, (part of what defines the "blazar sequence"), although with greater scatter than seen previously in studies of far fewer blazars. We describe an empirical estimator of luminosities in those 12 frequency bands using only the radio luminosity at 1.4 GHz and the redshift as inputs. Using this estimator, we study the demographics of blazars by comparing Monte-Carlo simulations to blazar surveys at several different frequencies and flux limits. We recover the observed evolutionary parameter for both low-frequency peaked (V/Vmax≈0.6) and high-frequency peaked (V/Vmax≈0.4) blazars, proving that selection effects cause the high-frequency-peaked sources to appear to anti-evolve even though the same underlying evolution was assumed in the simulation. We also show that the if instead we randomly assign fluxes independent of radio luminosity, the simulated blazar samples disagree strongly with the observed ones. These simulations confirm that luminosity and SED shape must indeed be linked in a physical blazar sequence.

  4. Multiwavelength analysis of the TeV Blazar RGB J0152+017

    SciTech Connect

    Kaufmann, S.; Hauser, M.; Herzog, J.; Wagner, S.; Gerard, L.; Giebels, B.; Nedbal, D.

    2008-12-24

    VHE gamma-ray emission was discovered from the high-frequency-peaked BL Lac object RGB J0152+017 in November 2007. The instantaneously triggered multiwavelength observations with the X-ray satellites Swift and RXTE, the optical telescope ATOM and the radio telescope Nancay provided the first simultaneous SED for RGB J0152+017. While these and further observations with H.E.S.S. gives no indication for variability, the follow-up observations until January 2008 with Swift (X-ray and UV-optical telescope) and ATOM (optical) show flux variations on time scales of {approx}10 days with different variability patterns. This non-monotonically flux variation of the simultaneous multiwavelength observations lead to the conclusion that the shape of the synchrotron spectrum changes.

  5. Multiwavelength Spectral Studies Of Fermi-LAT Blazars

    NASA Astrophysics Data System (ADS)

    Joshi, Manasvita; Marscher, A.; Jorstad, S.; Agudo, I.; Larionov, V.; Aller, M.; Gurwell, M.; Lähteenmäki, A.

    2011-01-01

    We present multiwavelength spectral analyses of several Fermi-LAT selected blazars that are part of the Boston University multiwaveband polarization monitoring program. The data for the objects of this study have been compiled from observations with Fermi, RXTE, the VLBA, and various ground-based optical telescopes starting in August 2008. We simulate the dynamic spectral energy distributions (SEDs) within the framework of a multi-zone time-dependent leptonic jet model for blazars, with radiation feedback, in the internal shock scenario. We discuss the intrinsic parameter differences present between the various blazar subclasses of our sample set and the interplay between synchrotron and inverse Compton radiation processes responsible for producing the resultant SEDs. This research was supported in part by NASA through Fermi grants NNX10AO59G, NNX08AV65G, and NNX08AV61G and ADP grant NNX08AJ64G, and by NSF grant AST-0907893.

  6. Multiwavelength Spectral Studies Of Fermi-lat Blazars

    NASA Astrophysics Data System (ADS)

    Joshi, Manasvita; Marscher, A.; Jorstad, S.; Boettcher, M.; Agudo, I.; Larionov, V.; Aller, M.; Gurwell, M.; Lahteenmaki, A.

    2011-09-01

    We present multiwavelength spectral analyses of two Fermi-LAT blazars, OJ 287 and 3C 279, that are part of the Boston University multiwaveband polarization monitoring program. The data have been compiled from observations with Fermi, RXTE, the VLBA, and various ground-based optical and radio telescopes. We simulate the dynamic spectral energy distributions (SEDs) within the framework of a multi-slice, time-dependent leptonic jet model for blazars, with radiation feedback, in the internal shock scenario. We use the physical jet parameters obtained from the VLBA monitoring to guide our modeling efforts. We discuss the role of intrinsic parameters and the interplay between synchrotron and inverse Compton radiation processes responsible for producing the resultant SEDs. This research was supported in part by NASA through Fermi grants NNX10AO59G, NNX08AV65G, and NNX08AV61G and ADP grant NNX08AJ64G, and by NSF grant AST-0907893.

  7. Multiwavelength Probes of Relativistic Shock Environs in Blazar Jets

    NASA Astrophysics Data System (ADS)

    Baring, Matthew G.; Boettcher, M.; Summerlin, E. J.

    2013-04-01

    Diffusive shock acceleration (DSA) at relativistic shocks is likely to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud AGN. An important recent development for blazar science is the ability of Fermi-LAT data to pin down the power-law index of the high energy portion of emission in these sources, and therefore also the index of the underlying non-thermal particle population. This diagnostic potential was not possible prior to Fermi launch, when gamma-ray information was dominated by the highly-absorbed TeV band. This paper highlights how multiwavelength spectra including X-ray band and Fermi data can be used to probe diffusive acceleration in relativistic, oblique, MHD shocks in blazars. The spectral index of the nonthermal particle distributions resulting from Monte Carlo simulations of DSA, and the fraction of thermal particles accelerated to non-thermal energies, depend sensitively on the particles' mean free path scale, and also on the shock magnetic field obliquity. We investigate self-consistently the radiative (synchrotron + Compton) signatures of the resulting thermal and nonthermal particle distributions. Important constraints on the frequency of particle scattering and the level of field turbulence are identified for blazars such as Mrk 501 and the Bl Lac object AO 0235+164. The possible interpretation that turbulence levels decline with remoteness from the shock, and a significant role for non-gyroresonant diffusion, are discussed.

  8. A Multiwavelength Study of Three Hybrid Blazars

    NASA Astrophysics Data System (ADS)

    Stanley, E. C.; Kharb, P.; Lister, M. L.; Marshall, H. L.; O'Dea, C.; Baum, S.

    2015-07-01

    We present multiwavelength imaging observations of PKS 1045-188, 8C 1849+670, and PKS 2216-038, three radio-loud active galactic nuclei from the MOJAVE-Chandra Sample that straddle the Fanaroff-Riley (FR) boundary between low- and high-power jets. These hybrid sources provide an excellent opportunity to study jet emission mechanisms and the influence of the external environment. We used archival VLA observations, and new Hubble and Chandra observations to identify and study the spectral properties of five knots in PKS 1045-188, two knots in 8C 1849+670, and three knots in PKS 2216-038. For the seven X-ray visible knots, we constructed and fit the broadband spectra using synchrotron and inverse Compton/cosmic microwave background (IC/CMB) emission models. In all cases, we found that the lack of detected optical emission ruled out the X-ray emission from the same electron population that produces radio emission. All three sources have high total extended radio power, similar to that of FR II sources. We find this is in good agreement with previously studied hybrid sources, where high-power hybrid sources emit X-rays via IC/CMB and the low-power hybrid sources emit X-rays via synchrotron emission. This supports the idea that it is total radio power rather than FR morphology that determines the X-ray emission mechanism. We found no significant asymmetries in the diffuse X-ray emission surrounding the host galaxies. Sources PKS 1045-188 and 8C 1849+670 show significant differences in their radio and X-ray termination points, which may result from the deceleration of highly relativistic bulk motion.

  9. Long-Term Multiwavelength Studies of High-Redshift Blazar 0836+710

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Akyuz, A.; Donato, D.; Perkins, J. S.; Larsson, S.; Sokolovsky, K.; Fuhrmann, L.; Kurtanidze, O.

    2012-01-01

    Following gamma-ray flaring activity of high-redshift (z=2.218) blazar 0836+710 in 2011, we have assembled a long-term multiwavelength study of this object. Although this source is monitored regularly by radio telescopes and the Fermi Large Area Telescope, its coverage at other wavelengths is limited. The optical flux appears generally correlated with the gamma-ray flux, while little variability has been seen at X-ray energies. The gamma-ray/radio correlation is complex compared to some other blazars. As for many blazars, the largest variability is seen at gamma-ray wavelengths.

  10. Multiwavelength behaviour of the blazar OJ 248 from radio to γ-rays

    NASA Astrophysics Data System (ADS)

    Carnerero, M. I.; Raiteri, C. M.; Villata, M.; Acosta-Pulido, J. A.; D'Ammando, F.; Smith, P. S.; Larionov, V. M.; Agudo, I.; Arévalo, M. J.; Arkharov, A. A.; Bach, U.; Bachev, R.; Benítez, E.; Blinov, D. A.; Bozhilov, V.; Buemi, C. S.; Bueno Bueno, A.; Carosati, D.; Casadio, C.; Chen, W. P.; Damljanovic, G.; Paola, A. Di; Efimova, N. V.; Ehgamberdiev, Sh. A.; Giroletti, M.; Gómez, J. L.; González-Morales, P. A.; Grinon-Marin, A. B.; Grishina, T. S.; Gurwell, M. A.; Hiriart, D.; Hsiao, H. Y.; Ibryamov, S.; Jorstad, S. G.; Joshi, M.; Kopatskaya, E. N.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Larionova, E. G.; Larionova, L. V.; Lázaro, C.; Leto, P.; Lin, C. S.; Lin, H. C.; Manilla-Robles, A. I.; Marscher, A. P.; McHardy, I. M.; Metodieva, Y.; Mirzaqulov, D. O.; Mokrushina, A. A.; Molina, S. N.; Morozova, D. A.; Nikolashvili, M. G.; Orienti, M.; Ovcharov, E.; Panwar, N.; Pastor Yabar, A.; Puerto Giménez, I.; Ramakrishnan, V.; Richter, G. M.; Rossini, M.; Sigua, L. A.; Strigachev, A.; Taylor, B.; Tornikoski, M.; Trigilio, C.; Troitskaya, Yu. V.; Troitsky, I. S.; Umana, G.; Valcheva, A.; Velasco, S.; Vince, O.; Wehrle, A. E.; Wiesemeyer, H.

    2015-07-01

    We present an analysis of the multiwavelength behaviour of the blazar OJ 248 at z = 0.939 in the period 2006-2013. We use low-energy data (optical, near-infrared, and radio) obtained by 21 observatories participating in the Gamma-Ray Large Area Space Telescope (GLAST)-AGILE Support Program of the Whole Earth Blazar Telescope, as well as data from the Swift (optical-UV and X-rays) and Fermi (γ-rays) satellites, to study flux and spectral variability and correlations among emissions in different bands. We take into account the effect of absorption by the Damped Lyman α intervening system at z = 0.525. Two major outbursts were observed in 2006-2007 and in 2012-2013 at optical and near-IR wavelengths, while in the high-frequency radio light curves prominent radio outbursts are visible peaking at the end of 2010 and beginning of 2013, revealing a complex radio-optical correlation. Cross-correlation analysis suggests a delay of the optical variations after the γ-ray ones of about a month, which is a peculiar behaviour in blazars. We also analyse optical polarimetric and spectroscopic data. The average polarization percentage P is less than 3 per cent, but it reaches ˜19 per cent during the early stage of the 2012-2013 outburst. A vague correlation of P with brightness is observed. There is no preferred electric vector polarization angle and during the outburst the linear polarization vector shows wide rotations in both directions, suggesting a complex behaviour/structure of the jet and possible turbulence. The analysis of 140 optical spectra acquired at the Steward Observatory reveals a strong Mg II broad emission line with an essentially stable flux of 6.2 × 10- 15 erg cm- 2 s- 1 and a full width at half-maximum of 2053 km s- 1.

  11. A correlative multi-wavelength study of blazars

    NASA Technical Reports Server (NTRS)

    Shrader, Chris R.

    1995-01-01

    This report describes the final results of work performed by the P.I. on this task. The scientific focus of this program was the broad-band spectroscopic study of the subclass of quasi-stellar objects known as 'Blazars' using primarily, data obtained with Compton Gamma-Ray Observatory (CGRO) and the International Ultraviolet Explorer (IUE), and ground-based optical and radio observatories.

  12. Multiwavelength Search for Correlated Time Variations in the Brightest EGRET Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.

    1994-01-01

    We have found that the emission in the blazar jets is highly stratified, as evidenced by time delays between the peaks of the flares at different wavebands. This fits well with the predictions of the jet models. Not all of the blazars have yet been observed long enough with the VLBA to determine the motions of their components. However, for those 39 blazars for which this analysis is possible as of August 1997, the apparent superluminal speeds are very high, ranging from about 10 to 35c (for a Hubble constant of 65 km/s Mpc. If this trend holds for the remainder of the sample (to be determined after the results of observations in July 1997 are analyzed along with those from previous epochs), the implication is that the EGRET-detected blazars have stronger relativistic beaming than does the general radio-bright blazar population.

  13. Multiwavelength Observations of the Gamma-ray Blazars Detected by AGILE

    NASA Astrophysics Data System (ADS)

    D'Ammando, F.; Vercellone, S.; Donnarumma, I.; Pacciani, L.; Pucella, G.; Tavani, M.; Vittorini, V.; Bulgarelli, A.; Chen, A. W.; Giuliani, A.; Longo, F.; AGILE Team

    2011-02-01

    Since its launch in April 2007, the AGILE satellite detected with the Gamma-Ray Imaging Detector several blazars in high γ-ray activity: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae and Mrk 421. Thanks to the rapid dissemination of our alerts, we were able to obtain multiwavelength ToO data from other observatories such as Spitzer, Swift, RXTE, Suzaku, INTEGRAL, MAGIC, VERITAS, as well as radio-to-optical coverage by means of the GASP Project of the WEBT and the REM Telescope. This large multifrequency coverage gave us the opportunity to study truly simultaneous spectral energy distributions of these sources from radio to γ-ray energy bands and to investigate the different mechanisms responsible for their emission. We present an overview of the AGILE results on these γ-ray blazars and the relative multifrequency data.

  14. Multiwavelength Probes of the Environs of Relativistic Shocks in Blazar Jets

    NASA Astrophysics Data System (ADS)

    Baring, Matthew G.; Böttcher, Markus; Summerlin, Errol J.

    2014-03-01

    Diffusive shock acceleration (DSA) at relativistic shocks is likely to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud AGN. An important recent development for blazar science is the ability of Fermi-LAT data to pin down the power-law index of the high energy portion of emission in these sources, and therefore also the index of the underlying non-thermal particle population. This diagnostic potential was not possible prior to Fermi launch, when gamma-ray information was dominated by the highly-absorbed TeV band. This paper highlights how multiwavelength spectra including X-ray band and Fermi data can be used to probe diffusive acceleration in relativistic, oblique, MHD shocks in blazar jets. The spectral index of the non-thermal particle distributions resulting from Monte Carlo simulations of DSA, and the fraction of thermal particles accelerated to non-thermal energies, depend sensitively on the particles' mean free path scale, and also on the magnetic field obliquity to the shock normal. We investigate self-consistently the radiative synchrotron/Compton signatures of the resulting thermal and non-thermal particle distributions. Important constraints on the frequency of particle scattering and the level of field turbulence are identified for the blazar AO 0235+164. The possible interpretation that turbulence levels decline with remoteness from jet shocks, and a significant role for non-gyroresonant diffusion, are discussed.

  15. MULTIWAVELENGTH OBSERVATIONS OF THE GAMMA-RAY BLAZAR PKS 0528+134 IN QUIESCENCE

    SciTech Connect

    Palma, N. I.; Boettcher, M.; Li, Y.; De la Calle, I.; Agudo, I.; Jorstad, S. G.; Joshi, M.; Aller, M.; Aller, H.; Bach, U.; BenItez, E.; Buemi, C. S.; Leto, P.; Escande, L.; Gurwell, M. A.; Heidt, J.; Hiriart, D.; Laehteenmaeki, A.; Larionov, V. M. E-mail: marscher@bu.edu E-mail: jlgomez@iaa.es

    2011-07-01

    We present multiwavelength observations of the ultraluminous blazar-type radio loud quasar PKS 0528+134 in quiescence during the period 2009 July-December. Four Target-of-Opportunity observations with the XMM-Newton satellite in the 0.2-10 keV range were supplemented with optical observations at the MDM Observatory, radio and optical data from the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope and the Very Long Baseline Array, additional X-ray data from the Rossi X-ray Timing Explorer (2-10 keV) and from Suzaku (0.5-10 keV) as well as {gamma}-ray data from the Fermi Large Area Telescope in the 100 MeV-200 GeV range. In addition, publicly available data from the SMARTS blazar monitoring program and the University of Arizona/Steward Observatory Fermi Support program were included in our analysis. We found no evidence of significant flux or spectral variability in {gamma}-rays and most radio bands. However, significant flux variability on a timescale of several hours was found in the optical regime, accompanied by a weak trend of spectral softening with increasing flux. We suggest that this might be the signature of a contribution of unbeamed emission, possibly from the accretion disk, at the blue end of the optical spectrum. The optical flux is weakly polarized with rapid variations of the degree and direction of polarization, while the polarization of the 43 GHz radio core remains steady, perpendicular to the jet direction. Optical spectropolarimetry of the object in the quiescent state suggests a trend of increasing degree of polarization with increasing wavelength, providing additional evidence for an unpolarized emission component, possibly thermal emission from the accretion disk, contributing toward the blue end of the optical spectrum. Over an extended period of several months, PKS 0528+134 shows moderate (amplitude {approx}< 50%) flux variability in the X-rays and most radio frequencies on {approx}1-2 week timescales. We constructed four

  16. Wide-Range Multiwavelength Observations of Northern TeV Blazars With MAGIC / HESS, Suzaku And KVA

    SciTech Connect

    Hayashida, M.; Rugamer, S.; Mazin, D.; Firpo, R.; Mannheim, K.; Tavecchio, F.; Teshima, M.; Horns, D.; Costamante, L.; Schwarzburg, S.; Wagner, S.; Takahashi, T.; Kataoka, J.; Madejski, G.; Sato, R.; Ushio, M.; /JAXA, Sagamihara

    2007-11-14

    We have conducted multiwavelength observations of several northern TeV blazars employing the ground-based {gamma}-ray observatories MAGIC and HESS, the optical KVA telescope, and the Suzaku X-ray satellite. The data taken in 2006 establish measurements of the contemporaneous spectral energy distributions of the rapidly variable blazar emission over a wide range of frequencies. Results allow us to test leptonic and hadronic emission and particle acceleration models which predict different correlations between the optical, X-ray, and very high energy {gamma}-ray emissions. In this presentation, we report on the highlights of the results of these observations.

  17. MAGIC long-term study of the distant TeV blazar PKS 1424+240 in a multiwavelength context

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hayashida, M.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nishijima, K.; Nowak, N.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Preziuso, S.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saggion, A.; Saito, T.; Saito, K.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Cutini, S.; Gasparrini, D.; Furniss, A.; Hovatta, T.; Kangas, T.; Kankare, E.; Kotilainen, J.; Lister, M.; Lähteenmäki, A.; Max-Moerbeck, W.; Pavlidou, V.; Readhead, A.; Richards, J.

    2014-07-01

    Aims: We present a study of the very high-energy (VHE; E> 100 GeV) γ-ray emission of the blazar PKS 1424+240 observed with the MAGIC telescopes. The primary aim of this paper is the multiwavelength spectral characterization and modeling of this blazar, which is made particularly interesting by the recent discovery of a lower limit of its redshift of z ≥ 0.6 and makes it a promising candidate to be the most distant VHE source. Methods: The source has been observed with the MAGIC telescopes in VHE γ rays for a total observation time of ~33.6 h from 2009 to 2011. A detailed analysis of its γ-ray spectrum and time evolution has been carried out. Moreover, we have collected and analyzed simultaneous and quasi-simultaneous multiwavelength data. Results: The source was marginally detected in VHE γ rays during 2009 and 2010, and later, the detection was confirmed during an optical outburst in 2011. The combined significance of the stacked sample is ~7.2σ. The differential spectra measured during the different campaigns can be described by steep power laws with the indices ranging from 3.5 ± 1.2 to 5.0 ± 1.7. The MAGIC spectra corrected for the absorption due to the extragalactic background light connect smoothly, within systematic errors, with the mean spectrum in 2009-2011 observed at lower energies by the Fermi-LAT. The absorption-corrected MAGIC spectrum is flat with no apparent turn down up to 400 GeV. The multiwavelength light curve shows increasing flux in radio and optical bands that could point to a common origin from the same region of the jet. The large separation between the two peaks of the constructed non-simultaneous spectral energy distribution also requires an extremely high Doppler factor if an one zone synchrotron self-Compton model is applied. We find that a two-component synchrotron self-Compton model describes the spectral energy distribution of the source well, if the source is located at z ~ 0.6. Appendix is available in electronic form at

  18. Fourier analysis of blazar variability

    SciTech Connect

    Finke, Justin D.; Becker, Peter A.

    2014-08-10

    Blazars display strong variability on multiple timescales and in multiple radiation bands. Their variability is often characterized by power spectral densities (PSDs) and time lags plotted as functions of the Fourier frequency. We develop a new theoretical model based on the analysis of the electron transport (continuity) equation, carried out in the Fourier domain. The continuity equation includes electron cooling and escape, and a derivation of the emission properties includes light travel time effects associated with a radiating blob in a relativistic jet. The model successfully reproduces the general shapes of the observed PSDs and predicts specific PSD and time lag behaviors associated with variability in the synchrotron, synchrotron self-Compton, and external Compton emission components, from submillimeter to γ-rays. We discuss applications to BL Lacertae objects and to flat-spectrum radio quasars (FSRQs), where there are hints that some of the predicted features have already been observed. We also find that FSRQs should have steeper γ-ray PSD power-law indices than BL Lac objects at Fourier frequencies ≲ 10{sup –4} Hz, in qualitative agreement with previously reported observations by the Fermi Large Area Telescope.

  19. Multiwavelength Evidence for Quasi-periodic Modulation in the Gamma-Ray Blazar PG 1553+113

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Albert, A.; Atwood, W. B.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Becerra Gonzalez, J.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bloom, E. D.; Bonino, R.; Bottacini, E.; Bregeon, J.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caputo, R.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Chekhtman, A.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Conrad, J.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Di Venere, L.; D´nguez, A.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fuhrmann, L.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Godfrey, G.; Green, D.; Grenier, I. A.; Grove, J. E.; Guiriec, S.; Harding, A. K.; Hays, E.; Hewitt, J. W.; Hill, A. B.; Horan, D.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kamae, T.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Manfreda, A.; Max-Moerbeck, W.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Michelson, P. F.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nuss, E.; Ohno, M.; Ohsugi, T.; Ojha, R.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Pearson, T. J.; Perkins, J. S.; Perri, M.; Pesce-Rollins, M.; Petrosian, V.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Schulz, A.; Sgrò, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Suson, D. J.; Takahashi, H.; Thayer, J. B.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Troja, E.; Uchiyama, Y.; Vianello, G.; Wood, K. S.; Wood, M.; Zimmer, S.; Berdyugin, A.; Corbet, R. H. D.; Hovatta, T.; Lindfors, E.; Nilsson, K.; Reinthal, R.; Sillanpää, A.; Stamerra, A.; Takalo, L. O.; Valtonen, M. J.

    2015-11-01

    We report for the first time a γ-ray and multiwavelength nearly periodic oscillation in an active galactic nucleus. Using the Fermi Large Area Telescope we have discovered an apparent quasi-periodicity in the γ-ray flux (E > 100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The marginal significance of the 2.18 ± 0.08 year period γ-ray cycle is strengthened by correlated oscillations observed in radio and optical fluxes, through data collected in the Owens Valley Radio Observatory, Tuorla, Katzman Automatic Imaging Telescope, and Catalina Sky Survey monitoring programs and Swift-UVOT. The optical cycle appearing in ˜10 years of data has a similar period, while the 15 GHz oscillation is less regular than seen in the other bands. Further long-term multiwavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.

  20. The TANAMI Multiwavelength Program: Dynamic spectral energy distributions of southern blazars

    NASA Astrophysics Data System (ADS)

    Krauß, F.; Wilms, J.; Kadler, M.; Ojha, R.; Schulz, R.; Trüstedt, J.; Edwards, P. G.; Stevens, J.; Ros, E.; Baumgartner, W.; Beuchert, T.; Blanchard, J.; Buson, S.; Carpenter, B.; Dauser, T.; Falkner, S.; Gehrels, N.; Gräfe, C.; Gulyaev, S.; Hase, H.; Horiuchi, S.; Kreikenbohm, A.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Lovell, J. E. J.; Müller, C.; Natusch, T.; Nesci, R.; Pursimo, T.; Phillips, C.; Plötz, C.; Quick, J.; Tzioumis, A. K.; Weston, S.

    2016-06-01

    Context. Simultaneous broadband spectral and temporal studies of blazars are an important tool for investigating active galactic nuclei (AGN) jet physics. Aims: We study the spectral evolution between quiescent and flaring periods of 22 radio-loud AGN through multiepoch, quasi-simultaneous broadband spectra. For many of these sources these are the first broadband studies. Methods: We use a Bayesian block analysis of Fermi/LAT light curves to determine time ranges of constant flux for constructing quasi-simultaneous spectral energy distributions (SEDs). The shapes of the resulting 81 SEDs are described by two logarithmic parabolas and a blackbody spectrum where needed. Results: The peak frequencies and luminosities agree well with the blazar sequence for low states with higher luminosity implying lower peak frequencies. This is not true for sources in high states. The γ-ray photon index in Fermi/LAT correlates with the synchrotron peak frequency in low and intermediate states. No correlation is present in high states. The black hole mass cannot be determined from the SEDs. Surprisingly, the thermal excess often found in FSRQs at optical/UV wavelengths can be described by blackbody emission and not an accretion disk spectrum. Conclusions: The so-called harder-when-brighter trend, typically seen in X-ray spectra of flaring blazars, is visible in the blazar sequence. Our results for low and intermediate states, as well as the Compton dominance, are in agreement with previous results. Black hole mass estimates using recently published parameters are in agreement with some of the more direct measurements. For two sources, estimates disagree by more than four orders of magnitude, possibly owing to boosting effects. The shapes of the thermal excess seen predominantly in flat spectrum radio quasars are inconsistent with a direct accretion disk origin. Tables of the fluxes are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or

  1. MULTIWAVELENGTH OBSERVATIONS OF THE PREVIOUSLY UNIDENTIFIED BLAZAR RX J0648.7+1516

    SciTech Connect

    Aliu, E.; Errando, M.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Boettcher, M.; Bradbury, S. M.; Cannon, A.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Cui, W.; Feng, Q.; Decerprit, G.; Duke, C.; Falcone, A. E-mail: miki@ucolick.org; Collaboration: VERITAS Collaboration; and others

    2011-12-01

    We report on the VERITAS discovery of very high energy (VHE) gamma-ray emission above 200 GeV from the high-frequency-peaked BL Lac (HBL) object RX J0648.7+1516 (GB J0648+1516), associated with 1FGL J0648.8+1516. The photon spectrum above 200 GeV is fitted by a power law dN/dE = F{sub 0}(E/E{sub 0}){sup -{Gamma}} with a photon index {Gamma} of 4.4 {+-} 0.8{sub stat} {+-} 0.3{sub syst} and a flux normalization F{sub 0} of (2.3 {+-} 0.5{sub stat} {+-} 1.2{sub sys}) Multiplication-Sign 10{sup -11} TeV{sup -1} cm{sup -2} s{sup -1} with E{sub 0} = 300 GeV. No VHE variability is detected during VERITAS observations of RX J0648.7+1516 between 2010 March 4 and April 15. Following the VHE discovery, the optical identification and spectroscopic redshift were obtained using the Shane 3 m Telescope at the Lick Observatory, showing the unidentified object to be a BL Lac type with a redshift of z = 0.179. Broadband multiwavelength observations contemporaneous with the VERITAS exposure period can be used to subclassify the blazar as an HBL object, including data from the MDM observatory, Swift-UVOT, and X-Ray Telescope, and continuous monitoring at photon energies above 1 GeV from the Fermi Large Area Telescope (LAT). We find that in the absence of undetected, high-energy rapid variability, the one-zone synchrotron self-Compton (SSC) model overproduces the high-energy gamma-ray emission measured by the Fermi-LAT over 2.3 years. The spectral energy distribution can be parameterized satisfactorily with an external-Compton or lepto-hadronic model, which have two and six additional free parameters, respectively, compared to the one-zone SSC model.

  2. A review of the multiwavelength studies on the blazars detected by AGILE

    NASA Astrophysics Data System (ADS)

    Donnarumma, Immacolata; AGILE Team

    2012-03-01

    We report on the main results on gamma-ray blazars as obtained by AGILE during 4 years in orbit. AGILE detected several flaring blazars, mostly FSRQs, which were studied from radio to TeV energy bands thanks to the rapid dissemination of our alerts. In particular, we carried out several multifrequency campaigns resulted from the synergy with other observatories such as GASP-WEBT (GLAST-AGILE Support Programme of the Whole Earth Blazar Telescope network), REM, Spitzer, Swift, RXTE, XMM-Newton, Suzaku, INTEGRAL, MAGIC, VERITAS. Temporal and SED variabilities were studied in details thanks to the large set of simultaneous data. The most relevant properties of our sample of blazars will be presented with a particular emphasis on the spectral thermal components, time lags, spectral trends (in X-rays and gamma-rays), jet geometry and acceleration mechanism at the inner portion of the jet itself.

  3. MULTI-WAVELENGTH OBSERVATIONS OF BLAZAR AO 0235+164 IN THE 2008-2009 FLARING STATE

    SciTech Connect

    Ackermann, M.; Ajello, M.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bottacini, E.; Buehler, R.; Cameron, R. A.; Ballet, J.; Casandjian, J. M.; Bastieri, D.; Buson, S.; Bellazzini, R.; Bregeon, J.; Bonamente, E.; Brigida, M.; Bruel, P.; Caraveo, P. A. E-mail: madejski@slac.stanford.edu E-mail: silvia.raino@ba.infn.it E-mail: knalew@colorado.edu; Collaboration: Fermi-LAT Collaboration; GASP-WEBT consortium; F-GAMMA; Iram-PdBI; Kanata; RXTE; SMARTS; Swift-XRT; and others

    2012-06-01

    The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to {gamma}-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the {gamma}-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R{sub g}. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.

  4. Multi-wavelength Observations of Blazar AO 0235+164 in the 2008-2009 Flaring State

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Blandford, R. D.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bottacini, E.; Bregeon, J.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Cutini, S.; D'Ammando, F.; de Palma, F.; Dermer, C. D.; Silva, E. do Couto e.; Drell, P. S.; Drlica-Wagner, A.; Dubois, R.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Focke, W. B.; Fortin, P.; Fuhrmann, L.; Fukazawa, Y.; Fusco, P.; Gargano, F.; Gasparrini, D.; Gehrels, N.; Germani, S.; Giglietto, N.; Giommi, P.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Larsson, S.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Naumann-Godo, M.; Nishino, S.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Pelassa, V.; Pesce-Rollins, M.; Pierbattista, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Rastawicki, D.; Razzano, M.; Readhead, A.; Reimer, A.; Reimer, O.; Reyes, L. C.; Richards, J. L.; Sbarra, C.; Sgrò, C.; Siskind, E. J.; Spandre, G.; Spinelli, P.; Szostek, A.; Takahashi, H.; Tanaka, T.; Thayer, J. G.; Thayer, J. B.; Thompson, D. J.; Tinivella, M.; Torres, D. F.; Tosti, G.; Troja, E.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vianello, G.; Vitale, V.; Waite, A. P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Zimmer, S.; Fermi-LAT Collaboration; Moderski, R.; Nalewajko, K.; Sikora, M.; Villata, M.; Raiteri, C. M.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Benítez, E.; Berdyugin, A.; Blinov, D. A.; Boettcher, M.; Bravo Calle, O. J. A.; Buemi, C. S.; Carosati, D.; Chen, W. P.; Diltz, C.; Di Paola, A.; Dolci, M.; Efimova, N. V.; Forné, E.; Gurwell, M. A.; Heidt, J.; Hiriart, D.; Jordan, B.; Kimeridze, G.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kurtanidze, O. M.; Lähteenmäki, A.; Larionova, E. G.; Larionova, L. V.; Larionov, V. M.; Leto, P.; Lindfors, E.; Lin, H. C.; Morozova, D. A.; Nikolashvili, M. G.; Nilsson, K.; Oksman, M.; Roustazadeh, P.; Sievers, A.; Sigua, L. A.; Sillanpää, A.; Takahashi, T.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Troitsky, I. S.; Umana, G.; GASP-WEBT Consortium; Angelakis, E.; Krichbaum, T. P.; Nestoras, I.; Riquelme, D.; F-GAMMA; Krips, M.; Trippe, S.; Iram-PdBI; Arai, A.; Kawabata, K. S.; Sakimoto, K.; Sasada, M.; Sato, S.; Uemura, M.; Yamanaka, M.; Yoshida, M.; Kanata; Belloni, T.; Tagliaferri, G.; RXTE; Bonning, E. W.; Isler, J.; Urry, C. M.; SMARTS; Hoversten, E.; Falcone, A.; Pagani, C.; Stroh, M.; (Swift-XRT

    2012-06-01

    The blazar AO 0235+164 (z = 0.94) has been one of the most active objects observed by Fermi Large Area Telescope (LAT) since its launch in Summer 2008. In addition to the continuous coverage by Fermi, contemporaneous observations were carried out from the radio to γ-ray bands between 2008 September and 2009 February. In this paper, we summarize the rich multi-wavelength data collected during the campaign (including F-GAMMA, GASP-WEBT, Kanata, OVRO, RXTE, SMARTS, Swift, and other instruments), examine the cross-correlation between the light curves measured in the different energy bands, and interpret the resulting spectral energy distributions in the context of well-known blazar emission models. We find that the γ-ray activity is well correlated with a series of near-IR/optical flares, accompanied by an increase in the optical polarization degree. On the other hand, the X-ray light curve shows a distinct 20 day high state of unusually soft spectrum, which does not match the extrapolation of the optical/UV synchrotron spectrum. We tentatively interpret this feature as the bulk Compton emission by cold electrons contained in the jet, which requires an accretion disk corona with an effective covering factor of 19% at a distance of 100 R g. We model the broadband spectra with a leptonic model with external radiation dominated by the infrared emission from the dusty torus.

  5. Multiwavelength variability properties of Fermi blazar S5 0716+714

    SciTech Connect

    Liao, N. H.; Bai, J. M.; Liu, H. T.; Li, F.; Weng, S. S.; Chen, Liang E-mail: baijinming@ynao.ac.cn

    2014-03-10

    S5 0716+714 is a typical BL Lacertae object. In this paper we present the analysis and results of long-term simultaneous observations in the radio, near-infrared, optical, X-ray, and γ-ray bands, together with our own photometric observations for this source. The light curves show that the variability amplitudes in γ-ray and optical bands are larger than those in the hard X-ray and radio bands and that the spectral energy distribution (SED) peaks move to shorter wavelengths when the source becomes brighter, which is similar to other blazars, i.e., more variable at wavelengths shorter than the SED peak frequencies. Analysis shows that the characteristic variability timescales in the 14.5 GHz, the optical, the X-ray, and the γ-ray bands are comparable to each other. The variations of the hard X-ray and 14.5 GHz emissions are correlated with zero lag, and so are the V band and γ-ray variations, which are consistent with the leptonic models. Coincidences of γ-ray and optical flares with a dramatic change of the optical polarization are detected. Hadronic models do not have the same natural explanation for these observations as the leptonic models. A strong optical flare correlating a γ-ray flare whose peak flux is lower than the average flux is detected. The leptonic model can explain this variability phenomenon through simultaneous SED modeling. Different leptonic models are distinguished by average SED modeling. The synchrotron plus synchrotron self-Compton (SSC) model is ruled out because of the extreme input parameters. Scattering of external seed photons, such as the hot-dust or broad-line region emission, and the SSC process are probably both needed to explain the γ-ray emission of S5 0716+714.

  6. Multiwavelength Observations of Strong Flares from the TeV Blazar 1ES 1959+650

    NASA Technical Reports Server (NTRS)

    Krawczynski, H.; Hughes, S. B.; Horan, D.; Aharonian, F.; Aller, M. F.; Aller, H.; Boltwood, P.; Buckley, J.; Coppi, P.; Fossati, G.

    2004-01-01

    Following the detection of strong TeV gamma ray flares from the BL Lac object 1 ES 1959+650 with the Whipple 10 m Cerenkov telescope on 2002 May 16 and 17, we performed intensive target of opportunity radio, optical, X-ray, and TeV ?ray observations from 2002 May 18 to August 14. Observations with the X-ray telescope RossiX-Ray Timing Explorer and the Whipple and HEGRA gamma-ray telescopes revealed several strong flares, enabling us to sensitively test the X-ray--gamma-ray flux correlation properties. Although the X-ray and gamma-ray fluxes seemed to be correlated in general, we found an orphan gamma-ray flare that was not accompanied by an X-ray flare. While we detected optical flux variability with the Boltwood and Abastumani observatories, the data did not give evidence for a correlation of the optical flux variability with the observed X-ray and 7-ray flares. Within statistical errors of about 0.03 Jy at 14.5 GHz and 0.05 Jy at 4.8 GHz, the radio fluxes measured with the University of Michigan Radio Astronomy Observatory stayed constant throughout the campaign; the mean values agreed well with the values measured on 2002 May 7 and June 7 at 4.9 and 15 GHz with the Very Large Array and at 4.8 GHz with archival flux measurements. After describing in detail the radio, optical, X-ray and gamma-ray light curves, and spectral energy distributions (SEDs), we present initial modeling of the SED with a simple synchrotron self- Compton model. With the addition of another TeV blazar with good broadband data, we consider the set of all TeV blazars, to begin to look for a connection of the jet properties to the properties of the central accreting black hole thought to drive the jet. Remarkably, the temporal and special X-ray and gamma-ray emission characteristics of TeV blazars are very similar, even though the mass estimates of their central black holes differ by up to 1 order of magnitude.

  7. Multi-Epoch Multiwavelength Spectra and Models for Blazar 3C 279

    NASA Technical Reports Server (NTRS)

    Hartman, R. C.; Boettcher, M.; Aldering, G.; Aller, H.; Aller, M.; Backman, D. E.; Balonek, T. J.; Bertsch, D. L.; Bloom, S. D.; Bock, H.; White, Nicholas E. (Technical Monitor)

    2001-01-01

    Of the blazars detected by EGRET in GeV gamma-rays, 3C 279 is not only the best-observed by EGRET, but also one of the best-monitored at lower frequencies. We have assembled eleven spectra, from GHz radio through GeV gamma-rays, from the time intervals of EGRET observations. Although some of the data have appeared in previous publications, most are new, including data taken during the high states in early 1999 and early 2000. All of the spectra show substantial gamma-ray contribution to the total luminosity of the object; in a high state, the gamma-ray luminosity dominates over that at all other frequencies by a factor of more than 10. There is no clear pattern of time correlation; different bands do not always rise and fall together, even in the optical, X-ray, and gamma-ray bands. The spectra are modeled using a leptonic jet, with combined synchrotron self-Compton + external Compton gamma-ray production. Spectral variability of 3C 279 is consistent with variations of the bulk Lorentz factor of the jet, accompanied by changes in the spectral shape of the electron distribution. Our modeling results are consistent with the UV spectrum of 3C 279 being dominated by accretion disk radiation during times of low gamma-ray intensity.

  8. Multiwavelength observations of the blazar 1ES 1011+496 in Spring 2008

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; de Almeida, U. Barres; Barrio, J. A.; González, J. Becerra; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Oña Wilhelmi, E.; Mendez, C. Delgado; Pierro, F. Di; Prester, D. Dominis; Dorner, D.; Doro, M.; Einecke, S.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; López, R. J. García; Garczarczyk, M.; Terrats, D. Garrido; Gaug, M.; Giammaria, P.; (Eisenacher), D. Glawion; Godinović, N.; Muñoz, A. González; Guberman, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; Barbera, A. La; Lelas, D.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Rosillo, M. Nievas; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Moroni, P. G. Prada; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Garcia, J. Rodriguez; Rügamer, S.; Saito, T.; Satalecka, K.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; Lucarelli, F.; Pittori, C.; Vercellone, S.; Berdyugin, A.; Carini, M. T.; Lähteenmäki, A.; Pasanen, M.; Pease, A.; Sainio, J.; Tornikoski, M.; Walters, R.

    2016-07-01

    The BL Lac object 1ES 1011+496 was discovered at very high energy (VHE, E > 100GeV) γ-rays by Major Atmospheric Gamma-ray Imaging Cherenkov (MAGIC) in Spring 2007. Before that the source was little studied in different wavelengths. Therefore, a multiwavelength (MWL) campaign was organized in Spring 2008. Along MAGIC, the MWL campaign included the Metsähovi Radio Observatory, Bell and Kungliga Vetenskapsakademien (KVA) optical telescopes and the Swift and AGILE satellites. MAGIC observations span from 2008 March to May for a total of 27.9 h, of which 19.4 h remained after quality cuts. The light curve showed no significant variability yielding an integral flux above 200 GeV of (1.3 ± 0.3) × 10-11 photons cm-2 s-1. The differential VHE spectrum could be described with a power-law function with a spectral index of 3.3 ± 0.4. Both results were similar to those obtained during the discovery. Swift X-ray Telescope observations revealed an X-ray flare, characterized by a harder-when-brighter trend, as is typical for high synchrotron peak BL Lac objects (HBL). Strong optical variability was found during the campaign, but no conclusion on the connection between the optical and VHE γ-ray bands could be drawn. The contemporaneous spectral energy distribution shows a synchrotron-dominated source, unlike concluded in previous work based on non-simultaneous data, and is well described by a standard one-zone synchrotron self-Compton model. We also performed a study on the source classification. While the optical and X-ray data taken during our campaign show typical characteristics of an HBL, we suggest, based on archival data, that 1ES 1011+496 is actually a borderline case between intermediate and high synchrotron peak frequency BL Lac objects.

  9. The Brightest Gamma-Ray Flaring Blazar in the Sky: AGILE and Multi-wavelength Observations of 3C 454.3 During 2010 November

    NASA Astrophysics Data System (ADS)

    Vercellone, S.; Striani, E.; Vittorini, V.; Donnarumma, I.; Pacciani, L.; Pucella, G.; Tavani, M.; Raiteri, C. M.; Villata, M.; Romano, P.; Fiocchi, M.; Bazzano, A.; Bianchin, V.; Ferrigno, C.; Maraschi, L.; Pian, E.; Türler, M.; Ubertini, P.; Bulgarelli, A.; Chen, A. W.; Giuliani, A.; Longo, F.; Barbiellini, G.; Cardillo, M.; Cattaneo, P. W.; Del Monte, E.; Evangelista, Y.; Feroci, M.; Ferrari, A.; Fuschino, F.; Gianotti, F.; Giusti, M.; Lazzarotto, F.; Pellizzoni, A.; Piano, G.; Pilia, M.; Rapisarda, M.; Rappoldi, A.; Sabatini, S.; Soffitta, P.; Trifoglio, M.; Trois, A.; Giommi, P.; Lucarelli, F.; Pittori, C.; Santolamazza, P.; Verrecchia, F.; Agudo, I.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Bach, U.; Berdyugin, A.; Borman, G. A.; Chigladze, R.; Efimov, Yu. S.; Efimova, N. V.; Gómez, J. L.; Gurwell, M. A.; McHardy, I. M.; Joshi, M.; Kimeridze, G. N.; Krajci, T.; Kurtanidze, O. M.; Kurtanidze, S. O.; Larionov, V. M.; Lindfors, E.; Molina, S. N.; Morozova, D. A.; Nazarov, S. V.; Nikolashvili, M. G.; Nilsson, K.; Pasanen, M.; Reinthal, R.; Ros, J. A.; Sadun, A. C.; Sakamoto, T.; Sallum, S.; Sergeev, S. G.; Schwartz, R. D.; Sigua, L. A.; Sillanpää, A.; Sokolovsky, K. V.; Strelnitski, V.; Takalo, L.; Taylor, B.; Walker, G.

    2011-08-01

    Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one γ-ray flare per year, becoming the most active γ-ray blazar in the sky. We present for the first time the multi-wavelength AGILE, Swift, INTEGRAL, and GASP-WEBT data collected in order to explain the extraordinary γ-ray flare of 3C 454.3 which occurred in 2010 November. On 2010 November 20 (MJD 55520), 3C 454.3 reached a peak flux (E >100 MeV) of Fp γ = (6.8 ± 1.0) × 10-5 photons cm-2 s-1 on a timescale of about 12 hr, more than a factor of six higher than the flux of the brightest steady γ-ray source, the Vela pulsar, and more than a factor of three brighter than its previous super-flare on 2009 December 2-3. The multi-wavelength data make possible a thorough study of the present event: the comparison with the previous outbursts indicates a close similarity to the one that occurred in 2009. By comparing the broadband emission before, during, and after the γ-ray flare, we find that the radio, optical, and X-ray emission varies within a factor of 2-3, whereas the γ-ray flux by a factor of 10. This remarkable behavior is modeled by an external Compton component driven by a substantial local enhancement of soft seed photons.

  10. THE BRIGHTEST GAMMA-RAY FLARING BLAZAR IN THE SKY: AGILE AND MULTI-WAVELENGTH OBSERVATIONS OF 3C 454.3 DURING 2010 NOVEMBER

    SciTech Connect

    Vercellone, S.; Romano, P.; Vittorini, V.; Donnarumma, I.; Pacciani, L.; Fiocchi, M.; Bazzano, A.; Ubertini, P.; Raiteri, C. M.; Villata, M.; Bianchin, V.; Bulgarelli, A.; Maraschi, L.; Pian, E.; Chen, A. W.

    2011-08-01

    Since 2005, the blazar 3C 454.3 has shown remarkable flaring activity at all frequencies, and during the last four years it has exhibited more than one {gamma}-ray flare per year, becoming the most active {gamma}-ray blazar in the sky. We present for the first time the multi-wavelength AGILE, Swift, INTEGRAL, and GASP-WEBT data collected in order to explain the extraordinary {gamma}-ray flare of 3C 454.3 which occurred in 2010 November. On 2010 November 20 (MJD 55520), 3C 454.3 reached a peak flux (E >100 MeV) of F{sup p}{sub {gamma}} = (6.8 {+-} 1.0) x 10{sup -5} photons cm{sup -2} s{sup -1} on a timescale of about 12 hr, more than a factor of six higher than the flux of the brightest steady {gamma}-ray source, the Vela pulsar, and more than a factor of three brighter than its previous super-flare on 2009 December 2-3. The multi-wavelength data make possible a thorough study of the present event: the comparison with the previous outbursts indicates a close similarity to the one that occurred in 2009. By comparing the broadband emission before, during, and after the {gamma}-ray flare, we find that the radio, optical, and X-ray emission varies within a factor of 2-3, whereas the {gamma}-ray flux by a factor of 10. This remarkable behavior is modeled by an external Compton component driven by a substantial local enhancement of soft seed photons.

  11. A three-year multi-wavelength study of the very-high-energy γ-ray blazar 1ES 0229+200

    SciTech Connect

    Aliu, E.; Archambault, S.; Arlen, T.; Aune, T.; Behera, B.; Chen, X.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Bouvier, A.; Byrum, K.; Ciupik, L.; Connolly, M. P.; Cui, W.; Duke, C.; Dumm, J. E-mail: jeremy.s.perkins@nasa.gov; and others

    2014-02-10

    The high-frequency-peaked BL Lacertae object 1ES 0229+200 is a relatively distant (z = 0.1396), hard-spectrum (Γ ∼ 2.5), very-high-energy (VHE; E > 100 GeV) emitting γ-ray blazar. VHE measurements of this active galactic nucleus have been used to place constraints on the intensity of the extragalactic background light and the intergalactic magnetic field (IGMF). A multi-wavelength study of this object centered around VHE observations by Very Energetic Radiation Imaging Telescope Array System (VERITAS) is presented. This study obtained, over a period of three years, an 11.7 standard deviation detection and an average integral flux F(E > 300 GeV) = (23.3 ± 2.8{sub stat} ± 5.8{sub sys}) × 10{sup –9} photons m{sup –2} s{sup –1}, or 1.7% of the Crab Nebula's flux (assuming the Crab Nebula spectrum measured by H.E.S.S). Supporting observations from Swift and RXTE are analyzed. The Swift observations are combined with previously published Fermi observations and the VHE measurements to produce an overall spectral energy distribution which is then modeled assuming one-zone synchrotron-self-Compton emission. The χ{sup 2} probability of the TeV flux being constant is 1.6%. This, when considered in combination with measured variability in the X-ray band, and the demonstrated variability of many TeV blazars, suggests that the use of blazars such as 1ES 0229+200 for IGMF studies may not be straightforward and challenges models that attribute hard TeV spectra to secondary γ-ray production along the line of sight.

  12. Simultaneous Multi-Wavelength Observations of the TeV Blazar Mrk 421 during February March, 2003: X-Ray and NIR Correlated Variability

    NASA Astrophysics Data System (ADS)

    Gupta, Alok C.; Acharya, B. S.; Bose, Debanjan; Chitnis, Varsha R.; Fan, Jun-Hui

    2008-08-01

    We report the result of simultaneous multi-wavelength observations of the TeV blazar Mrk 421 during February March 2003. We observed Mrk 421 using the Pachmarhi Array of Cerenkov Telescopes (PACT) of Tata Institute of Fundamental Research at Pachmarhi, India. Other simultaneous data were taken from the literature and public data archives. We have analyzed the high quality X-ray (2 20 keV) observations from the NASA Rossi X-Ray Timing Explorer (RXTE). We obtained a possible correlated variability between X-ray and J band (1.25 μ) near infrared (NIR) wavelength. This is the first case of X-ray and NIR correlated variability in Mrk 421 or any high energy peaked (HBL) blazar. The correlated variability reported here indicates a similar origin for the NIR and X-ray emissions. The emission is not affected much by the environment of the surrounding medium of the central engine of Mrk 421. The observations are consistent with the shock-in-jet model for the emissions.

  13. Time Series Analysis of the Blazar OJ 287

    NASA Astrophysics Data System (ADS)

    Gamel, Ellen; Ryle, W. T.; Carini, M. T.

    2013-06-01

    Blazars are a subset of active galactic nuclei (AGN) where the light is viewed along the jet of radiation produced by the central supermassive black hole. These very luminous objects vary in brightness and are associated with the cores of distant galaxies. The blazar, OJ 287, has been monitored and its brightness tracked over time. From these light curves the relationship between the characteristic “break frequency” and black hole mass can be determined through the use of power density spectra. In order to obtain a well-sampled light curve, this blazar will be observed at a wide range of timescales. Long time scales will be obtained using archived light curves from published literature. Medium time scales were obtained through a combination of data provided by Western Kentucky University and data collected at The Bank of Kentucky Observatory. Short time scales were achieved via a single night of observation at the 72” Perkins Telescope at Lowell Observatory in Flagstaff, AZ. Using time series analysis, we present a revised mass estimate for the super massive black hole of OJ 287. This object is of particular interest because it may harbor a binary black hole at its center.

  14. Time-Resolved Spectral Analysis of Blazar 0716+714

    NASA Astrophysics Data System (ADS)

    Diaz, Rosamaria; Harp, Gerald

    2016-01-01

    As electromagnetic (EM) waves from sources such as blazars travel through the intergalactic medium (IGM), they are slowed by electrons; a phenomenon called dispersion delay [2]. We study the propagation effects in emissions of EM waves from blazar source BL 0716+714 by estimating the average electron density, or dispersion measure (DM), of the IGM on a line of sight to the blazar. Measuring the variations in these effects with time allow us to understand the properties of the intervening material. Toward this goal we analyzed months of archived observations of BL 0716+714 taken by the Allen Telescope Array (ATA). The ATA's correlator produces cross-power vs. frequency spectra for every baseline (distance between a pair of antennas) in ten-second intervals. To reduce this immense load of data we used a technique based on interferometry called bispectrum, which does not depend on complicated array calibration and simplifies our work. The bispectrum multiplies baselines, three at a time, so that they form a closed loop, then the cube root of spectra are averaged [1]. This technique is independent of phase errors associated with any individual antenna and has a better SNR ratio than simply taking the average of all the baselines. We developed a numerical analysis program that takes in archived blazar files containing correlation data, computes the bispectrum, and outputs FITS images for each day of observations. The results show that our observations do not have sufficient sensitivity to reveal blazar variations in the frequency ranges that were studied. It is suggested that future observations at higher frequencies and/or with another telescope having greater sensitivity would reveal the time/frequency dependence of emission structure that would allow measurements of electron content. This work shows that but bispectrum is a useful tool for rapid characterization of interferometer data that does not require interferometer caclibration which could introduce artifacts

  15. Oscillation signature from multi-wavelength analysis on solar chromosphere

    SciTech Connect

    Mumpuni, Emanuel Sungging; Herdiwijaya, Dhani; Djamal, Mitra

    2014-03-24

    In this work, we investigate how the solar chromosphere responds to the photospheric dynamics by using tomography study, implementing multiwavelength analysis observations obtained from Dutch Open Telescope. By using high resolution, high-quality, simultaneous image sequences of multi-wavelength data, we try to obtain the oscillation signature that might play important role on chromospheric dynamic by using H-alpha (Hα) as primary diagnostic tool.

  16. MULTIWAVELENGTH VARIABILITY OF THE BLAZARS Mrk 421 AND 3C 454.3 IN THE HIGH STATE

    SciTech Connect

    Gaur, Haritma; Gupta, Alok C.; Wiita, Paul J.

    2012-01-15

    We report the results of photometric observations of the blazars Mrk 421 and 3C 454.3 designed to search for intraday variability (IDV) and short-term variability (STV). Optical photometric observations were spread over 18 nights for Mrk 421 and 7 nights for 3C 454.3 during our observing run in 2009-2010 at the 1.04 m telescope at Aryabhatta Research Institute of Observational Sciences, India. Genuine IDV is found for the source 3C 454.3 but not for Mrk 421. Genuine STV is found for both sources. Mrk 421 was revealed by the Monitor of All-sky X-ray Image (MAXI) X-ray detector on the International Space Station to be in an exceptionally high flux state in 2010 January-February. We performed a correlation between the X-ray and optical bands to search for time delays and found a weak correlation with higher frequencies leading the lower frequencies by about 10 days. The blazar 3C 454.3 was found to be in a high flux state in 2009 November-December. We performed correlations in optical observations made at three telescopes, along with X-ray data from the MAXI camera and public release {gamma}-ray data from the Fermi space telescope. We found strong correlations between the {gamma}-ray and optical bands at a time lag of about four days, but the X-ray flux is not correlated with either. We briefly discuss the possible reasons for the time delays between these bands within the framework of existing models for X-ray and {gamma}-ray emission mechanisms.

  17. Test of Models of the Cosmic Infrared Background with Multiwavelength Observations of the Blazar 1ES 1218+30.4 in 2009

    NASA Astrophysics Data System (ADS)

    Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Bird, R.; Böttcher, M.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Ciupik, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Dumm, J.; Errando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Garson, A., III.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gusbar, C.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Kaaret, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Lamerato, A.; Lang, M. J.; Li, K.; Madhavan, A. S.; Maier, G.; Majumdar, P.; McArthur, S.; McCann, A.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Orr, M.; Otte, A. N.; Park, N.; Perkins, J. S.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Roustazadeh, P.; Saxon, D. B.; Sembroski, G. H.; Şentürk, G. D.; Skole, C.; Staszak, D.; Telezhinsky, I.; Tešić, G.; Theiling, M.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Weinstein, A.; Welsing, R.; Williams, D. A.; Zitzer, B.

    2014-06-01

    We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and γ-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, >100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum—the first with simultaneous X-ray and VHE γ-ray energy spectra—is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via γVHE + γEBL → e + e - pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.

  18. Test of models of the cosmic infrared background with multiwavelength observations of the blazar 1ES 1218+30.4 in 2009

    SciTech Connect

    Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Bird, R.; Collins-Hughes, E.; Böttcher, M.; Bouvier, A.; Ciupik, L.; Connolly, M. P.; Cui, W.; Feng, Q.; Dumm, J.; Errando, M.; Falcone, A.; Federici, S.; and others

    2014-06-20

    We present the results of a multi-wavelength campaign targeting the blazar 1ES 1218+30.4 with observations with the 1.3 m McGraw-Hill optical telescope, the Rossi X-ray Timing Explorer (RXTE), the Fermi Gamma-Ray Space Telescope, and the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The RXTE and VERITAS observations were spread over a 13 day period and revealed clear evidence for flux variability, and a strong X-ray and γ-ray flare on 2009 February 26 (MJD 54888). The campaign delivered a well-sampled broadband energy spectrum with simultaneous RXTE and VERITAS very high energy (VHE, >100 GeV) observations, as well as contemporaneous optical and Fermi observations. The 1ES 1218+30.4 broadband energy spectrum—the first with simultaneous X-ray and VHE γ-ray energy spectra—is of particular interest as the source is located at a high cosmological redshift for a VHE source (z = 0.182), leading to strong absorption of VHE gamma rays by photons from the optical/infrared extragalactic background light (EBL) via γ{sub VHE} + γ{sub EBL} → e {sup +} e {sup –} pair-creation processes. We model the data with a one-zone synchrotron self-Compton (SSC) emission model and with the extragalactic absorption predicted by several recent EBL models. We find that the observations are consistent with the SSC scenario and all the EBL models considered in this work. We discuss observational and theoretical avenues to improve on the EBL constraints.

  19. A Multi-wavelength Polarimetric Study of the Blazar CTA 102 during a Gamma-Ray Flare in 2012

    NASA Astrophysics Data System (ADS)

    Casadio, Carolina; Gómez, José L.; Jorstad, Svetlana G.; Marscher, Alan P.; Larionov, Valeri M.; Smith, Paul S.; Gurwell, Mark A.; Lähteenmäki, Anne; Agudo, Iván; Molina, Sol N.; Bala, Vishal; Joshi, Manasvita; Taylor, Brian; Williamson, Karen E.; Arkharov, Arkady A.; Blinov, Dmitry A.; Borman, George A.; Di Paola, Andrea; Grishina, Tatiana S.; Hagen-Thorn, Vladimir A.; Itoh, Ryosuke; Kopatskaya, Evgenia N.; Larionova, Elena G.; Larionova, Liudmila V.; Morozova, Daria A.; Rastorgueva-Foi, Elizaveta; Sergeev, Sergey G.; Tornikoski, Merja; Troitsky, Ivan S.; Thum, Clemens; Wiesemeyer, Helmut

    2015-11-01

    We perform a multi-wavelength polarimetric study of the quasar CTA 102 during an extraordinarily bright γ-ray outburst detected by the Fermi Large Area Telescope in 2012 September-October when the source reached a flux of F>100 MeV = 5.2 ± 0.4 × 10-6 photons cm-2 s-1. At the same time, the source displayed an unprecedented optical and near-infrared (near-IR) outburst. We study the evolution of the parsec-scale jet with ultra-high angular resolution through a sequence of 80 total and polarized intensity Very Long Baseline Array images at 43 GHz, covering the observing period from 2007 June to 2014 June. We find that the γ-ray outburst is coincident with flares at all the other frequencies and is related to the passage of a new superluminal knot through the radio core. The powerful γ-ray emission is associated with a change in direction of the jet, which became oriented more closely to our line of sight (θ ˜ 1.°2) during the ejection of the knot and the γ-ray outburst. During the flare, the optical polarized emission displays intra-day variability and a clear clockwise rotation of electric vector position angles (EVPAs), which we associate with the path followed by the knot as it moves along helical magnetic field lines, although a random walk of the EVPA caused by a turbulent magnetic field cannot be ruled out. We locate the γ-ray outburst a short distance downstream of the radio core, parsecs from the black hole. This suggests that synchrotron self-Compton scattering of NIR to ultraviolet photons is the probable mechanism for the γ-ray production.

  20. VizieR Online Data Catalog: Dynamic SEDs of southern blazars - DSSB (Krauss+, 2016)

    NASA Astrophysics Data System (ADS)

    Krauss, F.; Wilms, J.; Kadler, M.; Ojha, R.; Schulz, R.; Trustedt, J.; Edwards, P. G.; Stevens, J.; Ros, E.; Baumgartner, W.; Beuchert, T.; Blanchard, J.; Buson, S.; Carpenter, B.; Dauser, T.; Falkner, S.; Gehrels, N.; Grafe, C.; Gulyaev, S.; Hase, H.; Horiuchi, S.; Kreikenbohm, A.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Lovell, J. E. J.; Muller, C.; Natusch, T.; Nesci, R.; Pursimo, T.; Phillips, C.; Plotz, C.; Quick, J.; Tzioumis, A. K.; Weston, S.

    2016-05-01

    The Dynamic SEDs of southern blazars catalog is based on a TANAMI multiwavelength project that has been monitoring a sample of 22 radio-loud blazars of the southern sky from radio to gamma-ray wavelengths. (4 data files).

  1. Statistical Analysis of the Long Baseline Variability Properties of a Large Gamma-Ray Selected Blazar AGN Sample

    NASA Astrophysics Data System (ADS)

    Shrader, Chris R.

    2013-06-01

    The Fermi Gamma-Ray Space Telescope has cataloged over 1800 gamma-ray (>100 MeV) point sources of which more than 1100 are identified with AGN. These AGN, and a large number of unidentified high-latitude objects of which a large fraction are also likely AGN, are predominantly representative of the radio-loud “blazar” subclass. The emission from these objects is well known to be beaming dominated and is almost always variable, often exhibiting high-amplitude flaring. To date there have been numerous studies of individual objects including multi-wavelength campaigns in some cases including parsec-scale radio jet morphological study. Collectively, this has led to new insight in to our understanding of the blazar phenomena and jet propagation in general. However, there remains a dearth of information on the collective variability characteristics of the population as a statistical ensemble. What, for example, are the distributions of flare amplitudes, durations, temporal profiles and recurrence histories among the gamma-ray blazar subclasses? Given the unprecedented sky coverage of Fermi - the full sky is observed approximately every two orbits leading to an approximate one part in 6 monitoring duty cycle for any point on the sky - we have begun to explore this issue. A light curve database compiled and maintained (weekly) by the Fermi Science Support Center contains flux histories for every source in the Fermi 2FGL catalog. In this contribution, we present our analysis of the statistical properties of the high-latitude component of this light curve database.

  2. Analysis of Blazar-flares -A Selfconsistent SSC Model

    NASA Astrophysics Data System (ADS)

    Matthias Weidinger, M. Sc.; Spanier, Felix

    While the jet as the orgigin of the very high energy (VHE) emission from blazars is beyond doubt, the microphysical processes, the composition as well as typical physical parameters such as the size or location of the emitting region within the jet are still a matter of debate. To probe these, outbursts of blazars seem to be a good tool, since they are timing events hence affecting e.g. the spatial extent of the emitting region but also typical timescales for the jet's microphysics. When it comes to high peaked BL Lac objects, a subclass of mostly nearby blazars, the self-compton ansatz is very sucessfull in modelling the spectral energy distribution (SED). Here a fully sef-consistent etxtension to the SSC model with diffusive shock acceleration is presented, which is used to model the variable VHE lightcurves of PKS 2155-304 and 1 ES 1218+30.4 observed by H.E.S.S. in 2006 and VERITAS in 2009 respectively. Additionally the time resolved SEDs of these blazars are accessible via the model which are not by direct observations due to the sensitivity of air-cherenkov telescopes. This allows for further studies of the observed time-integrated SEDs during the flares which again is very important for the interpretation of the shape of SEDs.

  3. ANTARES constrains a blazar origin of two IceCube PeV neutrino events

    NASA Astrophysics Data System (ADS)

    ANTARES Collaboration; Adrián-Martínez, S.; Albert, A.; André, M.; Anton, G.; Ardid, M.; Aubert, J.-J.; Baret, B.; Barrios, J.; Basa, S.; Bertin, V.; Biagi, S.; Bogazzi, C.; Bormuth, R.; Bou-Cabo, M.; Bouwhuis, M. C.; Bruijn, R.; Brunner, J.; Busto, J.; Capone, A.; Caramete, L.; Carr, J.; Chiarusi, T.; Circella, M.; Coniglione, R.; Costantini, H.; Coyle, P.; Creusot, A.; De Rosa, G.; Dekeyser, I.; Deschamps, A.; De Bonis, G.; Distefano, C.; Donzaud, C.; Dornic, D.; Dorosti, Q.; Drouhin, D.; Dumas, A.; Eberl, T.; Enzenhöfer, A.; Escoffier, S.; Fehn, K.; Felis, I.; Fermani, P.; Folger, F.; Fusco, L. A.; Galatà, S.; Gay, P.; Geißelsöder, S.; Geyer, K.; Giordano, V.; Gleixner, A.; Gómez-González, J. P.; Gracia-Ruiz, R.; Graf, K.; van Haren, H.; Heijboer, A. J.; Hello, Y.; Hernández-Rey, J. J.; Herrero, A.; Hößl, J.; Hofestädt, J.; Hugon, C.; James, C. W.; de Jong, M.; Kalekin, O.; Katz, U.; Kießling, D.; Kooijman, P.; Kouchner, A.; Kulikovskiy, V.; Lahmann, R.; Lattuada, D.; Lefèvre, D.; Leonora, E.; Loehner, H.; Loucatos, S.; Mangano, S.; Marcelin, M.; Margiotta, A.; Martínez-Mora, J. A.; Martini, S.; Mathieu, A.; Michael, T.; Migliozzi, P.; Neff, M.; Nezri, E.; Palioselitis, D.; Păvălaş, G. E.; Perrina, C.; Piattelli, P.; Popa, V.; Pradier, T.; Racca, C.; Riccobene, G.; Richter, R.; Roensch, K.; Rostovtsev, A.; Saldaña, M.; Samtleben, D. F. E.; Sánchez-Losa, A.; Sanguineti, M.; Sapienza, P.; Schmid, J.; Schnabel, J.; Schulte, S.; Schüssler, F.; Seitz, T.; Sieger, C.; Spies, A.; Spurio, M.; Steijger, J. J. M.; Stolarczyk, Th.; Taiuti, M.; Tamburini, C.; Tayalati, Y.; Trovato, A.; Tselengidou, M.; Tönnis, C.; Vallage, B.; Vallée, C.; Van Elewyck, V.; Visser, E.; Vivolo, D.; Wagner, S.; de Wolf, E.; Yepes, H.; Zornoza, J. D.; Zúñiga, J.; TANAMI Collaboration; Krauß, F.; Kadler, M.; Mannheim, K.; Schulz, R.; Trüstedt, J.; Wilms, J.; Ojha, R.; Ros, E.; Baumgartner, W.; Beuchert, T.; Blanchard, J.; Bürkel, C.; Carpenter, B.; Edwards, P. G.; Eisenacher Glawion, D.; Elsässer, D.; Fritsch, U.; Gehrels, N.; Gräfe, C.; Großberger, C.; Hase, H.; Horiuchi, S.; Kappes, A.; Kreikenbohm, A.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Litzinger, E.; Lovell, J. E. J.; Müller, C.; Phillips, C.; Plötz, C.; Quick, J.; Steinbring, T.; Stevens, J.; Thompson, D. J.; Tzioumis, A. K.

    2015-04-01

    Context. The source(s) of the neutrino excess reported by the IceCube Collaboration is unknown. The TANAMI Collaboration recently reported on the multiwavelength emission of six bright, variable blazars which are positionally coincident with two of the most energetic IceCube events. Objects like these are prime candidates to be the source of the highest-energy cosmic rays, and thus of associated neutrino emission. Aims: We present an analysis of neutrino emission from the six blazars using observations with the ANTARES neutrino telescope. Methods: The standard methods of the ANTARES candidate list search are applied to six years of data to search for an excess of muons - and hence their neutrino progenitors - from the directions of the six blazars described by the TANAMI Collaboration, and which are possibly associated with two IceCube events. Monte Carlo simulations of the detector response to both signal and background particle fluxes are used to estimate the sensitivity of this analysis for different possible source neutrino spectra. A maximum-likelihood approach, using the reconstructed energies and arrival directions of through-going muons, is used to identify events with properties consistent with a blazar origin. Results: Both blazars predicted to be the most neutrino-bright in the TANAMI sample (1653-329 and 1714-336) have a signal flux fitted by the likelihood analysis corresponding to approximately one event. This observation is consistent with the blazar-origin hypothesis of the IceCube event IC 14 for a broad range of blazar spectra, although an atmospheric origin cannot be excluded. No ANTARES events are observed from any of the other four blazars, including the three associated with IceCube event IC20. This excludes at a 90% confidence level the possibility that this event was produced by these blazars unless the neutrino spectrum is flatter than -2.4. Figures 2, 3 and Appendix A are available in electronic form at http://www.aanda.org

  4. Multi-wavelength analysis from tomography study on solar chromosphere

    SciTech Connect

    Mumpuni, Emanuel Sungging; Herdiwijaya, Dhani; Djamal, Mitra

    2015-04-16

    The Sun as the most important star for scientific laboratory in astrophysics as well as encompassing all living aspect on Earth, still holds scientific mystery. As the established model that the Sun’s energy fueled by the nuclear reaction, along with transport process to the typical Solar surface on around 6000-K temperature, many aspects still left as an open questions, such as how the chromosphere responded to the photospheric dynamics. In this preliminary work, we try to analyze the Solar chromosphere respond to the Photospheric dynamics using tomography study implementing multi-wavelength analysis observation obtained from Dutch Open Telescope. Using the Hydrogen-alpha Doppler signal as the primary diagnostic tool, we try to investigate the inter-relation between the magnetic and gas pressure dynamics that occur in the chromosphere.

  5. Multi-wavelength analysis of Ellerman Bomb Light Curves

    NASA Astrophysics Data System (ADS)

    Herlender, M.; Berlicki, A.

    We present the results of a multi-wavelength photometric analysis of Ellerman Bomb (EB) observations obtained from the Dutch Open Telescope. In our data we have found 6 EBs located in the super-penumbra of the main spot in the active region NOAA 10781. We present light curves of EB observed in the Hα line centre and wing +0.7 Å, in the Ca II H line centre and wing~+2.35 Å, in the G-band and in the TRACE 1600 Å filter. We have shown that EBs were visible in the G-band and moreover, there was a good correlation between the light curves in the G-band and in the Hα line wings. We also found quasi-periodic oscillations of EBs brightness in the G-band, CaII H line and TRACE 1600 Å filter.

  6. Computing the period of light variability in blazar objects using the periodogram spectral analysis method

    NASA Astrophysics Data System (ADS)

    Tang, J.; Zhang, X.; Wu, L.

    2007-10-01

    The periodogram spectral analysis method for equally spaced data is discussed and the method is tested with modeling signals. The effectiveness of the periodogram spectral analysis is confirmed by applications in noise series. The method has been applied to analyze the period of the Blazar 3C 279,3C 345 and BL Lac Objects OJ 287,ON 231.Their periods are 7.14yr, 10.00yr, 11.76 yr and 6.80yr, which are consistent with other documents in Jurkevich method. The results are satisfying. The obtained periods are helpful to understand physical mechanisms of Blazars. The paper analyzes the influence of window function. Moreover, their advantages and disadvantages are discussed for the practical applications. The application results also indicate that in comparison to other traditional prediction methods, the prediction method used in this paper has a higher prediction accuracy. Thus it has theoretical meaning and practical value for the period of light variation prediction.

  7. Discovery of VHE γ-rays from the blazar 1ES 1215+303 with the MAGIC telescopes and simultaneous multi-wavelength observations

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Alvarez, E. A.; Antonelli, L. A.; Antoranz, P.; Ansoldi, S.; Asensio, M.; Backes, M.; Barres de Almeida, U.; Barrio, J. A.; Bastieri, D.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnoli, G.; Borla Tridon, D.; Bretz, T.; Cañellas, A.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Cea del Pozo, E.; De Lotto, B.; Delgado Mendez, C.; Diago Ortega, A.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Eisenacher, D.; Elsaesser, D.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Häfner, D.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Huber, B.; Jankowski, F.; Jogler, T.; Kadenius, V.; Kellermann, H.; Klepser, S.; Krähenbühl, T.; Krause, J.; La Barbera, A.; Lelas, D.; Leonardo, E.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Makariev, M.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Mariotti, M.; Martínez, M.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moldón, J.; Moralejo, A.; Munar-Adrover, P.; Niedzwiecki, A.; Nieto, D.; Nilsson, K.; Nowak, N.; Orito, R.; Paiano, S.; Paneque, D.; Paoletti, R.; Pardo, S.; Paredes, J. M.; Partini, S.; Perez-Torres, M. A.; Persic, M.; Pilia, M.; Pochon, J.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puerto Gimenez, I.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, A.; Steinke, B.; Storz, J.; Strah, N.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zabalza, V.; Zandanel, F.; Zanin, R.; Berdyugin, A.; Buson, S.; Järvelä, E.; Larsson, S.; Lähteenmäki, A.; Tammi, J.

    2012-08-01

    Context. We present the discovery of very high energy (VHE, E > 100 GeV) γ-ray emission from the BL Lac object 1ES 1215+303 by the MAGIC telescopes and simultaneous multi-wavelength data in a broad energy range from radio to γ-rays. Aims: We study the VHE γ-ray emission from 1ES 1215+303 and its relation to the emissions in other wavelengths. Methods: Triggered by an optical outburst, MAGIC observed the source in 2011 January - February for 20.3 h. The target was monitored in the optical R-band by the KVA telescope that also performed optical polarization measurements. We triggered target of opportunity observations with the Swift satellite and obtained simultaneous and quasi-simultaneous data from the Fermi Large Area Telescope and from the Metsähovi radio telescope. We also present the analysis of older MAGIC data taken in 2010. Results: The MAGIC observations of 1ES 1215+303 carried out in 2011 January - February resulted in the first detection of the source at VHE with a statistical significance of 9.4σ. Simultaneously, the source was observed in a high optical and X-ray state. In 2010 the source was observed in a lower state in optical, X-ray, and VHE, while the GeV γ-ray flux and the radio flux were comparable in 2010 and 2011. The spectral energy distribution obtained with the 2011 data can be modeled with a simple one zone SSC model, but it requires extreme values for the Doppler factor or the electron energy distribution.

  8. Multi-wavelength analysis of young pulsars: an overview.

    NASA Astrophysics Data System (ADS)

    Maritz, J. M.; Meintjes, P. J.; Buchner, S. J.

    Young pulsars emit a broad spectrum of radiation that range from radio to gamma ray energies. These pulsars are considered as rotation powered pulsars that spin rapidly and are strongly magnetized. Following the discovery of pulsars nearly four decades ago, the population of known pulsars already reached a number of roughly two thousand. This known population of pulsars includes both millisecond and normal pulsars that were discovered by several telescopes. We analyze both HartRAO radio data and Fermi gamma ray data of the Vela pulsar. We also explore a proposed method of probing the electron column density of the instellar gas through analyzing the gamma ray diffuse data associated with the Fermi two-year observation. This paper serves as an overview of gamma ray and radio timing analysis of bright young pulsars with respect to the use of open source timing analysis tools (Tempo2, Psrchive, Enrico and the Fermi tools). We reason that the multi-wavelength picture of pulsars can help clarify questions regarding the origin of pulsed radiation emission mechanisms in several energy bands, but that radio observations will prove adequate for timing noise analysis, given the accurate and long radio data sets. The process of identifying gravitational waves in timing data, rests on gaining a deeper insight into the timing noise phenomena.

  9. Variability studies in blazar jets with SF analysis: caveats and problems

    NASA Astrophysics Data System (ADS)

    Emmanoulopoulos, Dimitrios; McHardy, Ian M.; Uttley, Phil

    2011-02-01

    Blazars are radio-loud active galactic nuclei (AGN) dominated by relativistic jets seen at small angles to the line-of-sight. They exhibit dramatic flux variations across the electromagnetic spectrum. The fastest variations are observed in the X-ray and γ-ray bands on time-scales of hours or even minutes. Currently, a substantial part of the blazar literature has been based on the study of these temporal variations through the use of structure function (SF) analysis, the results of which are believed to put great constrains on the jet-physics. The SF is often invoked in the framework of shot-noise models to determine the temporal properties of individual shots within the jet as well as their geometrical sizes. We argue, that for blazar variability studies, the SF-results are sometimes erroneously interpreted leading to misconceptions about the actual source properties. Based on extensive simulations we caution that spurious breaks will appear in the SFs of almost all light-curves, even though these light-curves may contain no intrinsic characteristic time-scale. Finally, it is also commonly thought that SFs are immune to the sampling problems, such as data-gaps, which affects the estimators of the underlying power spectra density function such as the periodogram. However, we show that SFs are also troubled by gaps which can induce artefacts.

  10. Multi-wavelength Investigation of the Variability of the Blazars PKS 1510-089, PKS 1514-241, PKS 1622-297, and PKS 2155-304

    NASA Astrophysics Data System (ADS)

    McFarland, J. P.; Miller, H. R.

    2003-12-01

    The 4 southern sky blazars, PKS 1510-089, PKS 1514-241, PKS 1622-297, and PKS 2155-304, were monitored for approximately 6 months in 6 wavebands (B, V, R, J, H, K) every three days. These data were obtained via the SMARTS consortium on the 1.3m telescope at Cerro Tololo Interamerican Observatory. We present this data as a function of time and waveband. These variations place severe limits on the size of the emitting region, and provide constraints for the physical processes responsible for these variations. JPM is a SMARTS Fellow and JPM and HRM are grateful for support of a grant from the Research Corporation and the PEGA-RPE program at Georgia State University.

  11. The X-Ray Spectra of Blazars: Analysis of the Complete EXOSAT Archive: Erratum

    NASA Astrophysics Data System (ADS)

    Sambruna, Rita M.; Barr, Paul; Giommi, Paolo; Maraschi, Laura; Tagliaferri, Gianpiero; Treves, Aldo

    1995-07-01

    In the paper "The X-Ray Spectra of Blazars: Analysis of the Complete EXOSAT Archive" by Rita M. Sambruna, Paul Barr, Paolo Giommi, Laura Maraschi, Gianpiero Tagliaferri, and Aldo Treves (ApJS, 95,371 [1994]), the section regarding the object PKS 1510-08 (Section 4.4.14) contains an erroneous quotation. K. P. Singh, A.R. Rao, and M.N. Vahia (ApJ, 365,455 [1990]) in fact detected: emission line only in the 1984 data, and not in the 1985 spectrum, as stated.

  12. Swift multi-wavelength observations of the high-redshift Blazar S5 0836+710 (4C 71.07)

    NASA Astrophysics Data System (ADS)

    Vercellone, Stefano; Romano, Patrizia; Raiteri, Claudia Maria; Acosta Pulido, Jose; Villata, Massimo; Carnerero Martin, Maria Isabel

    2016-04-01

    We present the preliminary results of a year-long Swift monitoring campaign of the high-redshift (z=2.172) flat-spectrum radio quasar (FSRQ) S5 0836+710 (4C 71.07). The campaign, based on one observation per month, 5 ks each observation, for 12 months, allowed us to investigate the synchrotron and nuclear emission contributions to the optical-UV frequency range of its spectral energy distribution and the X-ray spectral variations along a baseline of a year. We obtained a high-accuracy determination of UVOT magnitudes, an X-ray photon index with an uncertainty of the order of 5%, and well-sampled light curves both in the optical-UV and X-ray energy bands to study their possible modulations and correlations. Our study allowed us to exploit the unique Swift capabilities in terms of both simultaneous energy coverage and schedule flexibility. The Swift monitoring campaign was supported by observations by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) Collaboration, which provided radio, near-infrared, and optical photometric data as well as optical polarimetry. Moreover, a spectroscopic monitoring was obtained at the William Herschel Telescope (WHT) and the Nordic Optical Telescope (NOT). All these observations will allow us to obtain a comprehensive picture of the jet as well as of the nuclear source emission.

  13. Multiwavelength Examination of the COS B Field 2CG 075+00 Yields a Blazar Identification for 3EG J2016+3657

    NASA Technical Reports Server (NTRS)

    Mukherjee, R.; Gotthelf, E. V.; Halpern, Jules P.; Tavani, M.; Oliversen, Ronald (Technical Monitor)

    2001-01-01

    We present a high-energy study of the intriguing COS B gamma-ray field, 2CG 075+00, in order to search for possible counterparts. New EGRET data show that the COS B emission probably corresponds to two localized gamma-ray sources, 3EG J2016+3657 and 3EG J2021+3716. Spectral fits to these EGRET sources, assuming a power-law model, yield photon indices of approx. 2 for each object. We examine archival ROSAT and ASCA X-ray data that overlap both EGRET error boxes and find several point sources in the region to a flux limit of approximately 6.5 x 10(exp -13) ergs/sq cm s. We conclude that the most probable candidate for 3EG J2016+3657 is the compact, variable, flat-spectrum radio and millimeter source B2013+370 (G74.87+1.22), which has blazar like properties. The other source, 3EG J2021+3716, remains unidentified.

  14. A Comprehensive Statistical Description of Radio-through-Gamma-Ray Spectral Energy Distributions of All Known Blazars

    NASA Astrophysics Data System (ADS)

    Mao, Peiyuan; Urry, C. Megan; Massaro, Francesco; Paggi, Alessandro; Cauteruccio, Joe; Künzel, Soren R.

    2016-06-01

    We combined multi-wavelength data for blazars from the Roma-BZCAT catalog and analyzed hundreds of X-ray spectra. We present the fluxes and spectral energy distributions (SEDs), in 12 frequency bands from radio to γ-rays, for a final sample of 2214 blazars. Using a model-independent statistical approach, we looked for systematic trends in the SEDs; the most significant trends involved the radio luminosities and X-ray spectral indices of the blazars. We used a principal component analysis (PCA) to determine the basis vectors of the blazar SEDs and, in order to maximize the size of the sample, imputed missing fluxes using the K-nearest neighbors method. Using more than an order of magnitude more data than was available when Fossati et al. first reported trends of SED shape with blazar luminosity, we confirmed the anti-correlation between radio luminosity and synchrotron peak frequency, although with greater scatter than was seen in the smaller sample. The same trend can be seen between bolometric luminosity and synchrotron peak frequency. Finally, we used all of the available blazar data to determine an empirical SED description that depends only on the radio luminosity at 1.4 GHz and the redshift. We verified that this statistically significant relation was not a result of the luminosity–luminosity correlations that are natural in flux-limited samples (i.e., where the correlation is actually caused by the redshift rather than the luminosity).

  15. Analysis of the cumulative neutrino flux from Fermi LAT blazar populations using 3 years of IceCube data

    NASA Astrophysics Data System (ADS)

    Glüsenkamp, Thorsten

    2016-07-01

    The recent discovery of a diffuse neutrino flux up to PeV energies raises the question of which populations of astrophysical sources contribute to this diffuse signal. One extragalactic candidate source population to produce high-energy neutrinos are Blazars. We present results from a likelihood analysis searching for cumulative neutrino emission from Blazar populations selected with the 2nd Fermi LAT AGN catalogue (2LAC) using an IceCube data set that has been optimized for the detection of individual sources. In contrast to previous searches with IceCube, the investigated populations contain up to hundreds of sources, the biggest one being the entire Blazar sample measured by the Fermi-LAT. No significant neutrino signal was found from any of these populations. Some implications of this non-observation for the origin of the observed PeV diffuse signal will be discussed.

  16. Recent Highlights in the X-ray Study of Blazars (Invited Talk)

    NASA Astrophysics Data System (ADS)

    Pian, E.

    2003-07-01

    Blazars exhibit flux and spectral variations of largest amplitude at the highest frequencies. Therefore, monitoring their variability at X- and gamma-rays is the most effective tool to peer into the mighty powerhouse of these sources. High energy observations of the brightest blazars with the latest generation of satellites have allowed a detailed study of their behavior and have critically improved our understanding of the physics of blazar jets. I will review some of the recent results of blazar multiwavelength monitoring with emphasis on the X-ray campaigns accomplished with BeppoSAX and I will describe some of the future programs for blazar investigation from space, particularly with INTEGRAL.

  17. Does the Blazar Gamma-ray Spectrum Harden with Increasing Flux? - Analysis of Nine Years of EGRET Data

    NASA Technical Reports Server (NTRS)

    Nandikotkur, Giridhar; Jahoda, Keith M.; Hartman, R. C.; Mukherjee, R.; Sreekumar, P.; Boettcher, M.

    2007-01-01

    The Energetic Gamma Ray Experiment Telescope (EGRET) on the Compton Gamma Ray Observatory (CGRO) discovered gamma-ray emission from more than 67 blazars during its nine-year lifetime. We conducted an exhaustive search of the EGRET archives and selected all the blazars that were observed multiple times and were bright enough to enable a spectral analysis using standard powerlaw models. The sample consists of 18 flat-spectrum radio quasars (FSRQs), 6 low-frequency-peaked BL Lacs (LBLs) and 2 high-frequency-peaked BL Lacs (HBLs). We do not detect any clear pattern in'the variation of spectral index with flux. Some of the blazars do not show any statistical evidence for spectral variability. The spectrum hardens with increasing flux in a few cases. There is also evidence for a flux-hardness anticorrelation at lo\\v fluxes in five blazars. The well observed blazars (3C 279,3C 273, PKS 0528-i-134, PKS 1622-297, PKS 0208- 512) do not show any overall trend in the long-term spectral dependence on flux, but the sample shows a mixture of hard and soft states. We observed spectral hysteresis at weekly timescales in all the three FSRQs for which data from flares lasting for 3 approx. 4 weeks were available. All three sources show a counterclockwise rotation despite the widely different flux profiles. Hysteresis in the spectral index vs. flux space has never been observed in FSRQs in gamma-rays at weekly timescales. itre analyze the observed spectral behavior in the context of various inverse-Compton mechanisms believed to be responsible for emission in the EGRET energy range. Our analysis uses the EGRET skymaps that were regenerated to include the changes in performance during the mission.

  18. IDENTIFICATION OF NEW GAMMA-RAY BLAZAR CANDIDATES WITH MULTIFREQUENCY ARCHIVAL OBSERVATIONS

    SciTech Connect

    Cowperthwaite, Philip S.; Massaro, F.; D'Abrusco, R.; Paggi, A.; Smith, Howard A.; Tosti, G.

    2013-11-01

    Blazars are a highly variable, radio-loud subclass of active galactic nuclei. In order to better understand such objects we must be able to easily identify candidate blazars from the growing population of unidentified sources. Working toward this goal, we attempt to identify new gamma-ray blazar candidates from a sample of 102 previously unidentified sources. These sources are selected from The Astronomer's Telegram and the literature on the basis of non-periodic variability and multi-wavelength behavior. We then attempt to associate these objects to an IR counterpart in the Wide-field Infrared Survey Explorer all-sky survey. We are able to identify 16 candidate sources whose IR colors are consistent with those of the blazar population. Of those, 13 sources have IR colors indicative of being gamma-ray emitting blazar candidates. These sources all possess archival multi-wavelength observations that support their blazar-like nature.

  19. Identification of New Gamma-Ray Blazar Candidates with Multifrequency Archival Observations

    NASA Astrophysics Data System (ADS)

    Cowperthwaite, Philip S.; Massaro, F.; D'Abrusco, R.; Paggi, A.; Tosti, G.; Smith, Howard A.

    2013-11-01

    Blazars are a highly variable, radio-loud subclass of active galactic nuclei. In order to better understand such objects we must be able to easily identify candidate blazars from the growing population of unidentified sources. Working toward this goal, we attempt to identify new gamma-ray blazar candidates from a sample of 102 previously unidentified sources. These sources are selected from The Astronomer's Telegram and the literature on the basis of non-periodic variability and multi-wavelength behavior. We then attempt to associate these objects to an IR counterpart in the Wide-field Infrared Survey Explorer all-sky survey. We are able to identify 16 candidate sources whose IR colors are consistent with those of the blazar population. Of those, 13 sources have IR colors indicative of being gamma-ray emitting blazar candidates. These sources all possess archival multi-wavelength observations that support their blazar-like nature.

  20. Fast optical brightening of the blazar 3C 454.3 (2251+158)

    NASA Astrophysics Data System (ADS)

    Mirzaqulov, D. O.; Ehgamberdiev, Sh. A.; Villata, M.; Raiteri, C. M.

    2013-09-01

    With reference to ATel #5411, the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports on the recent observation of a strong optical brightening of the gamma-loud quasar 3C 454.3. This is one of the 28 blazars for which the GASP performs a long-term, multiwavelength monitoring.

  1. GLAST Large Area Telescope Multiwavelength Planning

    SciTech Connect

    Reimer, O.; Michelson, P.F.; Cameron, R.A.; Digel, S.W.; Thompson, D.J.; Wood, K.S.

    2007-01-03

    Gamma-ray astrophysics depends in many ways on multiwavelength studies. The Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory. Some of the high-priority multiwavelength needs include: (1) availability of contemporaneous radio and X-ray timing of pulsars; (2) expansion of blazar catalogs, including redshift measurements; (3) improved observations of molecular clouds, especially at high galactic latitudes; (4) simultaneous broad-band blazar monitoring; (5) characterization of gamma-ray transients, including gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for reliable and effective sources identification and characterization. Several of these activities are needed to be in place before launch.

  2. GLAST Large Area Telescope Multiwavelength Planning

    NASA Technical Reports Server (NTRS)

    Reimer, O.; Michelson, P. F.; Cameron, R. A.; Digel, S. W.; Thompson, D. J.; Wood, K. S.

    2007-01-01

    Gamma-ray astrophysics depends in many ways on multiwavelength studies. The Gamma-ray Large Area Space Telescope (GLAST) Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory. Some of the high-priority multiwavelength needs include: (1) availability of contemporaneous radio and X-ray timing of pulsars; (2) expansion of blazar catalogs, including redshift measurements; (3) improved observations of molecular clouds, especially at high galactic latitudes; (4) simultaneous broad-spectrum blazar monitoring; (5) characterization of gamma-ray transients, including gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for reliable and effective sources identification and characterization. Several of these activities are needed to be in place before launch.

  3. First hard X-ray observations of the blazar S5 0716+714 with NuSTAR during a multiwavelength campaign

    NASA Astrophysics Data System (ADS)

    Wierzcholska, A.; Siejkowski, H.

    2016-05-01

    We report the results of a multifrequency campaign targeting S5 0716+714 in the flaring state of the source observed in 2015 January and February. The observations have been performed using the following instruments: Fermi/Large Area Telescope (LAT), Nuclear Spectroscopic Telescope Array, X-ray Telescope and Ultraviolet/Optical Telescope. The elevated flux level was visible in all frequencies and the outburst consists of five sub-flares. In this paper, we focus on the analysis of the X-ray observations both in the soft and hard regimes for data collected with NuSTAR and Swift/XRT. This is the first time, when hard X-ray observations of the source collected with NuSTAR are reported. The studies reveal both low- and high-energy components clearly visible in the energy band, with the break energy of 8 keV, which is the highest break energy ever reported for S5 0716+714. The second part of this work is concentrated on multifrequency observations collected during the flaring activity period. The variability patterns recorded during the period are characterized using a fractional variability amplitude and description of the flare profiles. The correlation studies reveal strong and significant relation between the optical, ultraviolet and γ-ray observations, and no time lag is found for any of the studied relations.

  4. Constraining blazar physics with polarization signatures

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Boettcher, Markus; Li, Hui

    2016-01-01

    Blazars are active galactic nuclei whose jets are directed very close to our line of sight. They emit nonthermal-dominated emission from radio to gamma-rays, with the radio to optical emissions known to be polarized. Both radiation and polarization signatures can be strongly variable. Observations have shown that sometimes strong multiwavelength flares are accompanied by drastic polarization variations, indicating active participation of the magnetic field during flares. We have developed a 3D multi-zone time-dependent polarization-dependent radiation transfer code, which enables us to study the spectral and polarization signatures of blazar flares simultaneously. By combining this code with a Fokker-Planck nonthermal particle evolution scheme, we are able to derive simultaneous fits to time-dependent spectra, multiwavelength light curves, and time-dependent optical polarization signatures of a well-known multiwavelength flare with 180 degree polarization angle swing of the blazar 3C279. Our work shows that with detailed consideration of light travel time effects, the apparently symmetric time-dependent radiation and polarization signatures can be naturally explained by a straight, helically symmetric jet pervaded by a helical magnetic field, without the need of any asymmetric structures. Also our model suggests that the excess in the nonthermal particles during flares can originate from magnetic reconnection events, initiated by a shock propagating through the emission region. Additionally, the magnetic field should generally revert to its initial topology after the flare. We conclude that such shock-initiated magnetic reconnection event in an emission environment with relatively strong magnetic energy can be the driver of multiwavelength flares with polarization angle swings. Future statistics on such observations will constrain general features of such events, while magneto-hydrodynamic simulations will provide physical scenarios for the magnetic field evolution

  5. Broad band spectral energy distribution studies of Fermi bright blazars

    NASA Astrophysics Data System (ADS)

    Monte, C.; Giommi, P.; Cavazzuti, E.; Gasparrini, D.; Rainò, S.; Fuhrmann, L.; Angelakis, E.; Villata, M.; Raiteri, C. M.; Perri, M.; Richards, J.

    2011-02-01

    The Fermi Gamma-ray Space Telescope was successfully launched on June 11, 2008 and has already opened a new era for gamma-ray astronomy. The Large Area Telescope (LAT), the main instrument on board Fermi, presents a significant improvement in sensitivity over its predecessor EGRET, due to its large field of view and effective area, combined with its excellent timing capabilities. The preliminary results of the Spectral Energy Distribution Analysis performed on a sample of bright blazars are presented. For this study, the data from the first three months of data collection of Fermi have been used. The analysis is extended down to radio, mm, near-IR, optical, UV and X-ray bands and up to TeV energies based on unprecedented sample of simultaneous multi-wavelength observations by GASP-WEBT.

  6. Kepler light-curve analysis of the blazar W2R 1926+42

    NASA Astrophysics Data System (ADS)

    Mohan, P.; Gupta, Alok C.; Bachev, Rumen; Strigachev, Anton

    2016-02-01

    We study the long term Kepler light curve of the blazar W2R 1926+42 (˜1.6 yr) which indicates a variety of variability properties during different intervals of observation. The normalized excess variance, Fvar ranges from 1.8 per cent in the quiescent phase and 43.3 per cent in the outburst phase. We find no significant deviation from linearity in the Fvar-flux relation. Time series analysis is conducted using the Fourier power spectrum and the wavelet analysis methods to study the power spectral density (PSD) shape, infer characteristic time-scales and statistically significant quasi-periodic oscillations (QPOs). A bending power law with an associated time-scale of T_B = 6.2^{+6.4}_{-3.1} hours is inferred in the PSD analysis. We obtain a black hole mass of M• = (1.5-5.9) × 107 M⊙ for the first time using Fvar and the bend time-scale for this source. From a mean outburst lifetime of days, we infer a distance from the jet base r ≤ 1.75 pc indicating that the outburst originates due to a shock. A possible QPO peaked at 9.1 d and lasting 3.4 cycles is inferred from the wavelet analysis. Assuming that the QPO is a true feature, r = (152-378)GM•/c2 and supported by the other timing analysis products such as a weighted mean PSD slope of -1.5 ± 0.2 from the PSD analysis, we argue that the observed variability and the weak and short duration QPO could be due to jet based processes including orbital features in a relativistic helical jet and others such as shocks and turbulence.

  7. Constraining Emission Models of Luminous Blazar Sources

    SciTech Connect

    Sikora, Marek; Stawarz, Lukasz; Moderski, Rafal; Nalewajko, Krzysztof; Madejski, Greg; /KIPAC, Menlo Park /SLAC

    2009-10-30

    Many luminous blazars which are associated with quasar-type active galactic nuclei display broad-band spectra characterized by a large luminosity ratio of their high-energy ({gamma}-ray) and low-energy (synchrotron) spectral components. This large ratio, reaching values up to 100, challenges the standard synchrotron self-Compton models by means of substantial departures from the minimum power condition. Luminous blazars have also typically very hard X-ray spectra, and those in turn seem to challenge hadronic scenarios for the high energy blazar emission. As shown in this paper, no such problems are faced by the models which involve Comptonization of radiation provided by a broad-line-region, or dusty molecular torus. The lack or weakness of bulk Compton and Klein-Nishina features indicated by the presently available data favors production of {gamma}-rays via up-scattering of infrared photons from hot dust. This implies that the blazar emission zone is located at parsec-scale distances from the nucleus, and as such is possibly associated with the extended, quasi-stationary reconfinement shocks formed in relativistic outflows. This scenario predicts characteristic timescales for flux changes in luminous blazars to be days/weeks, consistent with the variability patterns observed in such systems at infrared, optical and {gamma}-ray frequencies. We also propose that the parsec-scale blazar activity can be occasionally accompanied by dissipative events taking place at sub-parsec distances and powered by internal shocks and/or reconnection of magnetic fields. These could account for the multiwavelength intra-day flares occasionally observed in powerful blazars sources.

  8. Observations of WIBRaLS Blazars with K2

    NASA Astrophysics Data System (ADS)

    Carini, Michael T.; Brown, Rebecca

    2016-01-01

    We report on the recent results of our ongoing program to characterize the rapid variability of a sample of IR and optically bright blazars with K2. The K2 mission, through its superb photometric precision and its ability to continuously sample light curves on timescales of minutes to months is providing unrivaled information on blazar variability. In its previous incarnation as the Kepler mission, only a few blazars were present in its field of view. Nevertheless, Kepler's observations of blazars uncovered rich and complicated variability down to the most rapid timescales it could sample and indicated a need for more roboust time-series analysis techniques. Our K2 sample of IR and optically bright blazars will be a unique set of blazars with light curves sampled on timescales not possible with ground based observatories. We present our recent blazar results from the K2 mission and discuss the analysis challenges they pose.

  9. GLAST Large Area Telescope Multiwavelength Planning

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Cameron, R. A.; Digel, S. W.; Wood, K. S.

    2006-01-01

    Because gamma-ray astrophysics depends in many ways on multiwavelength studies, the GLAST Large Area Telescope (LAT) Collaboration has started multiwavelength planning well before the scheduled 2007 launch of the observatory. Some of the high-priority needs include: (1) radio and X-ray timing of pulsars; (2) expansion of blazar catalogs, including redshift measurements (3) improved observations of molecular clouds, especially at high galactic latitudes; (4) simultaneous broad-spectrum blazar flare measurements; (5) characterization of gamma-ray transients, including gamma ray bursts; (6) radio, optical, X-ray and TeV counterpart searches for unidentified gamma-ray sources. Work on the first three of these activities is needed before launch. The GLAST Large Area Telescope is an international effort, with U.S. funding provided by the Department of Energy and NASA.

  10. Multidimensional analysis of nanoparticles with highly disperse properties using multiwavelength analytical ultracentrifugation.

    PubMed

    Walter, Johannes; Löhr, Konrad; Karabudak, Engin; Reis, Wieland; Mikhael, Jules; Peukert, Wolfgang; Wohlleben, Wendel; Cölfen, Helmut

    2014-09-23

    The worldwide trend in nanoparticle technology toward increasing complexity must be directly linked to more advanced characterization methods of size, shape and related properties, applicable to many different particle systems in science and technology. Available techniques for nanoparticle characterization are predominantly focused on size characterization. However, simultaneous size and shape characterization is still an unresolved major challenge. We demonstrate that analytical ultracentrifugation with a multiwavelength detector is a powerful technique to address multidimensional nanoparticle analysis. Using a high performance optical setup and data acquisition software, information on size, shape anisotropy and optical properties were accessible in one single experiment with unmatched accuracy and resolution. A dynamic rotor speed gradient allowed us to investigate broad distributions on a short time scale and differentiate between gold nanorod species including the precise evaluation of aggregate formation. We report how to distinguish between different species of single-wall carbon nanotubes in just one experiment using the wavelength-dependent sedimentation coefficient distribution without the necessity of time-consuming purification methods. Furthermore, CdTe nanoparticles of different size and optical properties were investigated in a single experiment providing important information on structure-property relations. Thus, multidimensional information on size, density, shape and optical properties of nanoparticulate systems becomes accessible by means of analytical ultracentrifugation equipped with multiwavelength detection. PMID:25130765

  11. Optical spectroscopic observations of blazars and γ-ray blazar candidates in the Sloan digital sky survey data release nine

    SciTech Connect

    Massaro, F.; Masetti, N.; D'Abrusco, R.; Paggi, A.; Funk, S.

    2014-10-01

    We present an analysis of the optical spectra available in the Sloan Digital Sky Survey data release nine (SDSS DR9) for the blazars listed in the ROMA-BZCAT and for the γ-ray blazar candidates selected according to their IR colors. First, we adopt a statistical approach based on Monte Carlo simulations to find the optical counterparts of the blazars listed in the ROMA-BZCAT catalog. Then, we crossmatched the SDSS spectroscopic catalog with our selected samples of blazars and γ-ray blazar candidates, searching for those with optical spectra available to classify our blazar-like sources and, whenever possible, to confirm their redshifts. Our main objectives are to determine the classification of uncertain blazars listed in the ROMA-BZCAT and to discover new gamma-ray blazars. For the ROMA-BZCAT sources, we investigated a sample of 84 blazars, confirming the classification for 20 of them and obtaining 18 new redshift estimates. For the γ-ray blazars, indicated as potential counterparts of unassociated Fermi sources or with uncertain nature, we established the blazar-like nature of 8 out of the 27 sources analyzed and confirmed 14 classifications.

  12. Blazar Observations with the MAGIC Telescope

    NASA Astrophysics Data System (ADS)

    Kneiske, T. M.; Mannheim, K.

    The MAGIC Telescope will be able to detect gamma gay sources down to energies of 30GeV. Therefore a large number of sources will be seen, especially blazars. 30 GeV is also the upper energy limit of EGRET. Therefore it is possible to extrapolate a spectrum of an EGRET source without a complicated model. We make first predictions about the detectability of EGRET blazars calculating the minimum observation time for the MAGIC Telescope. Blazars are often located at high redshifts and their spectra should show some cut-offs at high energies due to pair production processes with low energy background photons. We developed a background radiation model using recent results of optical to infrared data and included this absorption effect in our calculation about the observability. We found that the shape of the spectrum and the intergalactic absorption does not make a big difference for a simple detection of the source. The observation time is only dependent on the flux near the energy threshold of the telescope (30 GeV) and the zenith angle of the blazar. The results are showing that MAGIC will be able to detect more than 50% of the EGRET sources even at high redshift and therefore it will be a good tool for multi-wavelength campaigns.

  13. BLAZAR SPECTRAL PROPERTIES AT 74 MHz

    SciTech Connect

    Massaro, F.; Funk, S.; Giroletti, M.; Paggi, A.; D'Abrusco, R.; Tosti, G.

    2013-10-01

    Blazars are the most extreme class of active galactic nuclei. Despite a previous investigation at 102 MHz for a small sample of BL Lac objects and our recent analysis of blazars detected in the Westerbork Northern Sky Survey, a systematic study of the blazar spectral properties at frequencies below 100 MHz has been never carried out. In this paper, we present the first analysis of the radio spectral behavior of blazars based on the recent Very Large Array Low-frequency Sky Survey (VLSS) at 74 MHz. We search for blazar counterparts in the VLSS catalog, confirming that they are detected at 74 MHz. We then show that blazars present radio-flat spectra (i.e., radio spectral indices of ∼0.5) when evaluated, which also about an order of magnitude in frequency lower than previous analyses. Finally, we discuss the implications of our findings in the context of the blazars-radio galaxies connection since the low-frequency radio data provide a new diagnostic tool to verify the expectations of the unification scenario for radio-loud active galaxies.

  14. The X-ray spectra of blazars: Analysis of the complete EXOSAT archive

    NASA Technical Reports Server (NTRS)

    Sambruna, Rita M.; Barr, Paul; Giommi, Paolo; Maraschi, Laura; Tagliaferri, Gianpiero; Treves, Aldo

    1994-01-01

    We analyzed the 0.1-10 keV spectra of 26 blazars (21 BL Lac objects and 5 highly polarized quasars), on the basis of 93 exposures taken from the EXOSAT archives. Fits were performed first with a single power-law model. Indications are found that better fits can be obtained with models where the slope steepens at higher energies. We therefore considered a broken power law and found that in a large fraction of the spectra the fit is significantly improved. Fits with a power law + oxygen edge at 0.6 keV are also explored.

  15. A bright near-IR state of the blazar 4C 38.41 (1633+382) observed by the GASP

    NASA Astrophysics Data System (ADS)

    Carnerero, M. I.; Raiteri, C. M.; Villata, M.; Acosta-Pulido, J. A.; Velasco, S.; Gonzalez-Morales, Pedro A.

    2013-07-01

    The flat-spectrum radio quasar 4C 38.41 (1633+382) is one of the 28 blazars for which the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) performs a long-term, multiwavelength monitoring.

  16. Spectral variability studies and acceleration scenarios in jets of blazars

    NASA Astrophysics Data System (ADS)

    Joshi, Manasvita

    2009-06-01

    This work focuses on the study of spectral energy distributions (SEDs) and the spectral variability patterns of blazars, especially BL Lac objects. It also investigates the dominant mode of particle acceleration in the jets of blazars. The first part of the work describes the BL Lac object 3C 66A, which was the target of an intensive multiwavelength campaign in 2003/2004. During the campaign, flux measurements from radio to X-ray frequencies and upper limits in the very high energy (VHE) g-ray regime were obtained. A time-dependent leptonic jet model has been used to obtain a detailed description of the physical processes in 3C 66A. This successful model results in the reproduction of the observed spectral energy distribution (SED) and the optical variability pattern. The model also predicts an intrinsic cutoff value for the VHE g-ray emission and the possibility of the object being observed by MAGIC, Fermi, and other future missions. The second part of the work uses the internal shock model to explore the particle acceleration scenarios and the subsequent production of radiation via synchrotron and synchrotron self-Compton processes at sub-pc scales of a relativistic jet. A code has been developed to simulate the acceleration mechanism and to calculate the resulting spectrum after accounting for the inhomogeneity in the photon density throughout the acceleration region by dividing the region into multiple zones and considering the subsequent time- dependent radiation transfer within the zone and in between zones. An extensive study to understand the effects of varying shock and radiative parameters on the SED and spectral lightcurves of a generic blazar source has been carried out to aid in future theoretical analysis of such sources. This dissertation also includes a brief description of the observations conducted with the 1.3 m McGraw-Hill telescope of the MDM observatory at Kitt Peak, Arizona. The observations were carried out as a part of an ongoing long- term

  17. Fourier Analysis of Blazar Variability: Klein-Nishina Effects and the Jet Scattering Environment

    NASA Astrophysics Data System (ADS)

    Finke, Justin D.; Becker, Peter A.

    2015-08-01

    The strong variability of blazars can be characterized by power spectral densities (PSDs) and Fourier frequency-dependent time lags. In previous work, we created a new theoretical formalism for describing the PSDs and time lags produced via a combination of stochastic particle injection and emission via the synchrotron, synchrotron self-Compton, and external Compton (EC) processes. This formalism used the Thomson cross section and simple δ-function approximations to model the synchrotron and Compton emissivities. Here we expand upon this work, using the full Compton cross section and detailed and accurate emissivities. Our results indicate good agreement between the PSDs computed using the δ-function approximations and those computed using the accurate expressions, provided the observed photons are produced primarily by electrons with energies exceeding the lower limit of the injected particle population. Breaks are found in the PSDs at frequencies corresponding to the cooling timescales of the electrons primarily responsible for the observed emission, and the associated time lags are related to the difference in electron cooling timescales between the two energy channels, as expected. If the electron cooling timescales can be determined from the observed time lags and/or the observed EC PSDs, then one could in principle use the method developed here to determine the energy of the external seed photon source for EC, which is an important unsolved problem in blazar physics.

  18. The Blazar 3C 66A in 2003-2004: hadronic versus leptonic model fits

    SciTech Connect

    Reimer, A.

    2008-12-24

    The low-frequency peaked BL Lac object 3C 66A was the subject of an extensive multi-wavelength campaign from July 2003 till April 2004, which included quasi-simultaneous observations at optical, X-rays and very high energy gamma-rays. Here we apply the hadronic Synchrotron-Proton Blazar (SPB) model to the observed spectral energy distribution time-averaged over a flaring state, and compare the resulting model fits to those obtained from the application of the leptonic Synchrotron-Self-Compton (SSC) model. The results are used to identify diagnostic key predictions of the two blazar models for future multi-wavelength observations.

  19. Synchrotron polarization in blazars

    SciTech Connect

    Zhang, Haocheng; Böttcher, Markus; Chen, Xuhui

    2014-07-01

    We present a detailed analysis of time- and energy-dependent synchrotron polarization signatures in a shock-in-jet model for γ-ray blazars. Our calculations employ a full three-dimensional radiation transfer code, assuming a helical magnetic field throughout the jet. The code considers synchrotron emission from an ordered magnetic field, and takes into account all light-travel-time and other relevant geometric effects, while the relevant synchrotron self-Compton and external Compton effects are handled with the two-dimensional Monte-Carlo/Fokker-Planck (MCFP) code. We consider several possible mechanisms through which a relativistic shock propagating through the jet may affect the jet plasma to produce a synchrotron and high-energy flare. Most plausibly, the shock is expected to lead to a compression of the magnetic field, increasing the toroidal field component and thereby changing the direction of the magnetic field in the region affected by the shock. We find that such a scenario leads to correlated synchrotron + synchrotron-self-Compton flaring, associated with substantial variability in the synchrotron polarization percentage and position angle. Most importantly, this scenario naturally explains large polarization angle rotations by ≳ 180°, as observed in connection with γ-ray flares in several blazars, without the need for bent or helical jet trajectories or other nonaxisymmetric jet features.

  20. Synchrotron Polarization in Blazars

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus

    2014-07-01

    We present a detailed analysis of time- and energy-dependent synchrotron polarization signatures in a shock-in-jet model for γ-ray blazars. Our calculations employ a full three-dimensional radiation transfer code, assuming a helical magnetic field throughout the jet. The code considers synchrotron emission from an ordered magnetic field, and takes into account all light-travel-time and other relevant geometric effects, while the relevant synchrotron self-Compton and external Compton effects are handled with the two-dimensional Monte-Carlo/Fokker-Planck (MCFP) code. We consider several possible mechanisms through which a relativistic shock propagating through the jet may affect the jet plasma to produce a synchrotron and high-energy flare. Most plausibly, the shock is expected to lead to a compression of the magnetic field, increasing the toroidal field component and thereby changing the direction of the magnetic field in the region affected by the shock. We find that such a scenario leads to correlated synchrotron + synchrotron-self-Compton flaring, associated with substantial variability in the synchrotron polarization percentage and position angle. Most importantly, this scenario naturally explains large polarization angle rotations by >~ 180°, as observed in connection with γ-ray flares in several blazars, without the need for bent or helical jet trajectories or other nonaxisymmetric jet features.

  1. Broadband Observations of High Redshift Blazars

    NASA Astrophysics Data System (ADS)

    Paliya, Vaidehi S.; Parker, M. L.; Fabian, A. C.; Stalin, C. S.

    2016-07-01

    We present a multi-wavelength study of four high redshift blazars, S5 0014+81 (z = 3.37), CGRaBS J0225+1846 (z = 2.69), BZQ J1430+4205 (z = 4.72), and 3FGL J1656.2‑3303 (z = 2.40) using quasi-simultaneous data from the Swift, Nuclear Spectroscopic Telescope Array (NuSTAR) and the Fermi-Large Area Telescope (LAT) and also archival XMM-Newton observations. Other than 3FGL J1656.2‑3303, none of the sources were known as γ-ray emitters, and our analysis of ∼7.5 yr of LAT data reveals the first time detection of statistically significant γ-ray emission from CGRaBS J0225+1846. We generate the broadband spectral energy distributions (SED) of all the objects, centering at the epoch of NuSTAR observations and reproduce them using a one-zone leptonic emission model. The optical‑UV emission in all the objects can be explained by radiation from the accretion disk, whereas the X-ray to γ-ray windows of the SEDs are found to be dominated by inverse Compton scattering off the broad line region photons. All of them host black holes that are billions of solar masses. Comparing the accretion disk luminosity and the jet power of these sources with a large sample of blazars, we find them to occupy a high disk luminosity–jet power regime. We also investigate the X-ray spectral properties of the sources in detail with a major focus on studying the causes of soft X-ray deficit, a feature generally seen in high redshift radio-loud quasars. We summarize that this feature could be explained based on the intrinsic curvature in the jet emission rather than being due to the external effects predicted in earlier studies, such as host galaxy and/or warm absorption.

  2. Polarization swings reveal magnetic energy dissipation in blazars

    SciTech Connect

    Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; Guo, Fan; Li, Hui

    2015-04-30

    The polarization signatures of blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, large (≳ 180°) polarization angle swings are observed. We suggest that such phenomena can be interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability, and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change in its polarization signatures. This unprecedented combination of spectral, variability, and polarization information in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic-field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.

  3. Triggered Observations of a new VHE Gamma-ray Blazar

    NASA Astrophysics Data System (ADS)

    Boettcher, Markus

    2011-10-01

    We propose triggered observations of a new VHE blazar. Observations will be triggered following the detection of a flaring state by VERITAS. Simultaneous radio, near-IR, and optical coverage by the GLAST-AGILE Support Program (GASP) will be arranged, and we will include Fermi MeV -- GeV gamma-ray data. The proposed campaign aims at the study of new TeV blazars with data to allow meaningful studies of their broadband spectral and variability properties, and ultimately understand the mechanisms of particle acceleration and emission of radiation in TeV blazars. This proposal follows the same strategy as a predecessor proposal in AO-6 which was triggered and led to a highly successful multiwavelength campaign on W~Comae in June 2008.

  4. Polarization swings reveal magnetic energy dissipation in blazars

    DOE PAGESBeta

    Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; Guo, Fan; Li, Hui

    2015-04-30

    The polarization signatures of blazar emissions are known to be highly variable. In addition to small fluctuations of the polarization angle around a mean value, large (≳ 180°) polarization angle swings are observed. We suggest that such phenomena can be interpreted as arising from light-travel-time effects within an underlying axisymmetric emission region. We present the first simultaneous fitting of the multi-wavelength spectrum, variability, and time-dependent polarization features of a correlated optical and gamma-ray flaring event of the prominent blazar 3C279, which was accompanied by a drastic change in its polarization signatures. This unprecedented combination of spectral, variability, and polarization informationmore » in a coherent physical model allows us to place stringent constraints on the particle acceleration and magnetic-field topology in the relativistic jet of a blazar, strongly favoring a scenario in which magnetic energy dissipation is the primary driver of the flare event.« less

  5. Simultaneous analysis of hydrodynamic and optical properties using analytical ultracentrifugation equipped with multiwavelength detection.

    PubMed

    Walter, Johannes; Sherwood, Peter J; Lin, Wei; Segets, Doris; Stafford, Walter F; Peukert, Wolfgang

    2015-03-17

    Analytical ultracentrifugation (AUC) has proven to be a powerful tool for the study of particle size distributions, particle shapes, and interactions with high accuracy and unrevealed resolution. In this work we show how the analysis of sedimentation velocity data from the AUC equipped with a multiwavelength detector (MWL) can be used to gain an even deeper understanding of colloidal and macromolecular mixtures. New data evaluation routines have been integrated in the software SEDANAL to allow for the handling of MWL data. This opens up a variety of new possibilities because spectroscopic information becomes available for individual components in mixtures at the same time using MWL-AUC. For systems of known optical properties information on the hydrodynamic properties of the individual components in a mixture becomes accessible. For the first time, the determination of individual extinction spectra of components in mixtures is demonstrated via MWL evaluation of sedimentation velocity data. In our paper we first provide the informational background for the data analysis and expose the accessible parameters of our methodology. We further demonstrate the data evaluation by means of simulated data. Finally, we give two examples which are highly relevant in the field of nanotechnology using colored silica and gold nanoparticles of different size and extinction properties. PMID:25679871

  6. Multiwavelength Analysis of a Moving Type-IV Radio Burst on 4th March 2012

    NASA Astrophysics Data System (ADS)

    Veluchamy, V.; Chen, Y.; Feng, S.; Du, G.; Song, H.; Kong, X.

    2015-12-01

    We performed a multiwavelength analysis of a moving Type-IV radio burst on 4th march 2012. The Type-IV radio burst is observed between 10:39 - 11:00 UT in the frequency range of 300 - 20 MHz. From the radio heliographic observation, the radio source of the type-IV burst is traced and their sky plane speed is estimated as ~ 370 km/s. A plasmoid structure is ejected during the impulsive phase of the flare, at the same time of the type-IV burst and the structure is clearly observed at SDO/AIA 131 Å channel. From this, we find that the radio source moves with the plasmoid. The high brightness temperature profile in the range of 108 - 109 K and the moderate polarization between -50 - 30 % supports the plasma emission mechanism. Further the differential emission measure (DEM) analysis will be carried out and their results will be presented to provide more evidence of the emission mechanism.

  7. The Arecibo Methanol Maser Galactic Plane Survey. II. Statistical and Multiwavelength Counterpart Analysis

    NASA Astrophysics Data System (ADS)

    Pandian, Jagadheep D.; Goldsmith, Paul F.

    2007-11-01

    We present an analysis of the properties of the 6.7 GHz methanol maser sample detected in the Arecibo Methanol Maser Galactic Plane Survey. The distribution of the masers in the Galaxy, and statistics of their multiwavelength counterparts is consistent with the hypothesis of 6.7 GHz maser emission being associated with massive young stellar objects. Using the detection statistics of our survey, we estimate the minimum number of methanol masers in the Galaxy to be 1275. The l-v diagram of the sample shows the tangent point of the Carina-Sagittarius spiral arm to be around 49.6°, and suggests the occurrence of massive star formation along the extension of the Crux-Scutum arm. A Gaussian component analysis of the maser spectra shows the mean line width to be 0.38 km s-1, which is more than a factor of 2 larger than what has been reported in the literature. We also find no evidence that faint methanol masers have different properties than their bright counterparts.

  8. Analysis of the activity of the blazar BL Lacertae over the period 1998-2011

    NASA Astrophysics Data System (ADS)

    Strigunov, K. S.; Zhovtan, A. V.

    2016-07-01

    In 1998-2011 the blazar (active galactic nucleus) BL Lacertae was observed at Crimean Astrophysical Observatory (CrAO) with the second-generation GT-48 Cherenkov telescope at energies >1 TeV with a total significance of 11.8σ. More than 20 flares and a fourfold change in yearly mean fluxes (>1 TeV) were recorded. The optical ( B band) data obtained at CrAO and the TeV data are shown to correlate in some time intervals. The optical data are also compared with the X-ray RXTE/ASM (2-10 keV) data. In addition, the data from GT-48 are compared with the gamma-ray fluxes recorded by the Fermi LAT space telescope (0.1-300 GeV). The 2009 flare at TeV and Fermi energies has been studied. As a result, it has been found that as the activity rises the increase in flux at high energies exceeds its increase at low energies. This conclusion may be related to the conversion mechanism of particle acceleration. This is consistent with the results of studies for a similar object, 1ES 1426+428.

  9. AGILE confirmation of enhanced gamma-ray activity from the Blazar 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Lucarelli, F.; Pittori, C.; Verrecchia, F.; Bulgarelli, A.; Fioretti, V.; Zoli, A.; Piano, G.; Munar-Adrover, P.; Tavani, M.; Donnarumma, I.; Vercellone, S.; Striani, E.; Cardillo, M.; Gianotti, F.; Trifoglio, M.; Giuliani, A.; Mereghetti, S.; Caraveo, P.; Perotti, F.; Chen, A.; Argan, A.; Costa, E.; Del Monte, E.; Evangelista, Y.; Feroci, M.; Lazzarotto, F.; Lapshov, I.; Pacciani, L.; Soffitta, P.; Sabatini, S.; Vittorini, V.; Pucella, G.; Rapisarda, M.; Di Cocco, G.; Fuschino, F.; Galli, M.; Labanti, C.; Marisaldi, M.; Pellizzoni, A.; Pilia, M.; Trois, A.; Barbiellini, G.; Vallazza, E.; Longo, F.; Morselli, A.; Picozza, P.; Prest, M.; Lipari, P.; Zanello, D.; Cattaneo, P. W.; Rappoldi, A.; Colafrancesco, S.; Parmiggiani, N.; Ferrari, A.; Antonelli, A.; Giommi, P.; Salotti, L.; Valentini, G.; D'Amico, F.

    2016-06-01

    Following ATel #9148, reporting multi-wavelength activity from the BL Lac type blazar 1ES 1959+650, AGILE also detects increased gamma-ray emission above 100 MeV from a position compatible with this BL Lac source.

  10. Studying Gamma-Ray Blazars With the GLAST-LAT

    SciTech Connect

    Lott, B.; Carson, J.; Madejski, G.; Ciprini, S.; Dermer, C.D.; Giommi, P.; Lonjou, V.; Reimer, A.; /Stanford U., HEPL /KIPAC, Menlo Park

    2007-11-13

    Thanks to its sensitivity (4 10{sup -9} ph (E> 100 MeV) cm{sup -2} s{sup -1} for one year of observation), the GLAST LAT should detect many more (over a thousand) gamma-ray blazars than currently known. This large blazar sample will enable detailed population studies to be carried out. Moreover, the LAT large field-of-view combined with the scanning mode will provide a very uniform exposure over the sky, allowing a constant monitoring of several tens of blazars and flare alerts to be issued. This poster presents the LAT performance relevant to blazar studies, more particularly related to timing and spectral properties. Major specific issues regarding the blazar phenomenon that the LAT data should shed light on thanks to these capabilities will be discussed, as well as the different approaches foreseen to address them. The associated data required in other bands, to be collected in contemporaneous/simultaneous multiwavelength campaigns are mentioned as well.

  11. Multiwavelength anomalous diffraction analysis at the M absorption edges of uranium

    PubMed Central

    Liu, Yee; Ogata, Craig M.; Hendrickson, Wayne A.

    2001-01-01

    The multiwavelength anomalous diffraction (MAD) method for phase evaluation is now widely used in macromolecular crystallography. Successful MAD structure determinations have been carried out at the K or L absorption edges of a variety of elements. In this study, we investigate the anomalous scattering properties of uranium at its MIV (3.326 Å) and MV (3.490 Å) edge. Fluorescence spectra showed remarkably strong anomalous scattering at these edges (f′ = −70e, f′′ = 80e at the MIV edge and f′ = −90e, f′′ = 105e at the MV edge), many times higher than from any anomalous scatterers used previously for MAD phasing. However, the large scattering angles and high absorption at the low energies of these edges present some difficulties not found in typical crystallographic studies. We conducted test experiments at the MIV edge with crystals of porcine elastase derivatized with uranyl nitrate. A four-wavelength MAD data set complete to 3.2-Å Bragg spacings was collected from a single small frozen crystal. Analysis of the data yielded satisfactory phase information (average difference of 0ϕT − 0ϕA for replicated determinations is 32°) and produced an interpretable electron-density map. Our results demonstrate that it is practical to measure macromolecular diffraction data at these edges with current instrumentation and that phase information of good accuracy can be extracted from such experiments. We show that such experiments have potential for the phasing of very large macromolecular assemblages. PMID:11526210

  12. Blazars: Artist Conception

    NASA Video Gallery

    What astronomers once thought were two blazar families may in fact be one, as shown in this artist's concept. Energy stored in the black hole during its salad days of intense accretion may later be...

  13. VERITAS Blazar Observations - Recent Results

    SciTech Connect

    Cogan, Peter

    2008-12-24

    We present the discovery of very high energy (VHE) gamma-ray emission from the high-frequency-peaked BL Lac object 1ES 0806+524 (z = 0.138) and the intermediate-frequency-peaked BL Lac object W Comae (z = 0.102) with VERITAS. VHE emission was discovered from these objects during the 2007/2008 observing campaign, with a strong outburst from W Comae detected in mid-March, lasting a few days. Quasi-simultaneous spectral energy distributions are presented, incorporating optical (AAVSO), and X-ray (Swift/RXTE) observations. We also present the energy spectrum of the distant BL Lac (z = 0.182) 1ES 1218+304 which was detected by VERITAS during the 2006/2007 observing campaign. The energy spectrum is discussed in the context of different models of absorption from the diffuse extragalactic background radiation. We present multiwavelength observations of the blazar Markarian 421 (z = 0.03), including a strong flare initially detected by the Whipple 10 m gamma-ray telescope. Finally we present a broadband spectral energy distribution for 1ES 2344+514 (z = 0.044) which is successfully fit using a one zone synchrotron self-Compton model.

  14. Long-Term Optical Photopolarimetric Monitoring of Blazars at San Pedro Mártir

    NASA Astrophysics Data System (ADS)

    Benítez, E.; Heidt, J.; Hiriart, D.; Agudo, I.; Cabrera, J. I.; Dultzin, D.; González, M. M.; López, J. M.; Mújica, R.; Nilsson, K.; Sacahui, R.; Sorcia, M.

    2011-10-01

    Variability of optical polarized light has result to be a powerful tool for studying Blazars, since it enable us to determine the strength and orientation of magnetic field associated with the relativistic jet. Also, polarized light is a valuable way of testing the location of the γ-ray emission, although the physical mechanisms responsible of its production remain unclear. Most importantly, since multi-wavelength campaigns typically concentrate on sources during highly active states, the characteristic polarimetric properties of Blazars in the pre-and post outbursts states are less known. Thus, we have started a dedicated monitoring program of Blazars from the GASP sample at San Pedro Mártir, in order to study their polarimetric variability properties. In this work we want to show the current status of the program presenting some preliminary results on the optical-polarimetric and γ-ray variability observed with Fermi-LAT on the blazar PKS 1510-089.

  15. BVRI Standard Stars Near Selected Very High Energy Blazars

    NASA Astrophysics Data System (ADS)

    Pace, Cameron; Pearson, R.; Moody, J. W.; Joner, M. D.

    2010-01-01

    The nature of blazar variability is a test of the standard model of Active Galactic Nuclei (AGN). To be useful, measurements of blazar intensity must be compared to standard stars that have been tied into a standard photometric system. To aid the long-term study of blazars, we have measured BVRI magnitudes for six to eight comparison stars near the eight northern Very High Energy (VHE) blazars published by Horan & Weekes (2008). Our magnitudes have been tied into the standard stars published by Landolt (2009). The stars we have measured bracket the expected range of magnitudes between active and inactive phases of the blazars. Preliminary analysis of our results indicates an RMS error better than 0.02 magnitudes in all bands. Our measurements of comparison stars generally agree very well with previously published values. We are grateful to Brigham Young University and the National Science Foundation for their financial support.

  16. RoboPol: Unveiling the Physics of Blazar Jets from Skinakas

    NASA Astrophysics Data System (ADS)

    Pavlidou, V.

    2016-06-01

    Blazars are powered by relativistic jets and radiate exclusively through extreme, nonthermal particle interactions, energized by accretion onto supermassive black holes. Despite intensive observational and theoretical efforts over the last four decades, the details of blazar astrophysics remain elusive. The launch of NASA's Fermi Gammaray Space Telescope in 2008 provided an unprecedented opportunity for the systematic study of blazar jets and has prompted large-scale blazar monitoring efforts across wavelengths. In such a multi-wavelength campaign, a novel effect was discovered: fast changes in the optical polarization during gamma-ray flares. Optical emission from blazars is significantly polarized and the polarization probes the magnetic field structure in the jet. For this reason, such polarization rotations reveal important information about the evolution of disturbances responsible for blazar flares. The RoboPol program for the polarimetric monitoring of statistically complete samples of blazars was developed in 2013 to systematically study this class of events. RoboPol is a collaboration between the University of Crete, Caltech, the Max-Planck Institute for Radio Astronomy, the Inter-University Centre for Astronomy and Astrophysics in India, and the Nicolaus Copernicus University in Poland. Using a novel polarimeter operating at the 1.3m telescope of the Skinakas Observatory in Crete, it has succeeded in its 3 years of operation in taking optopolarimetric rotations of blazars from novelty status to a well-studied phenomenon that can be used to answer long-standing questions in our theoretical understanding of jets. We review the RoboPol program and its most important results in the classification of the optopolarimetric properties of blazars, the statistical properties of polarization rotations, and their relation to gamma-ray activity in blazar jets.

  17. GLAST Large Area Telescope Multiwavelength Opportunities

    NASA Technical Reports Server (NTRS)

    Thompson, David

    2008-01-01

    The Gamma-ray Large Area Space Telescope (GLAST) is scheduled for launch this year. Because the GLAST Large Area Telescope (LAT) has a huge field of view and the GLAST Observatory will be operated in scanning mode, it will survey the entire sky daily. The GLAST Mission and the LAT Collaboration invite cooperative efforts from theorists and observers at all wavelengths to help optimize the science. Possible topics include: (1) Blazars: These Active Galactic Nuclei are expected to be a major source class for LAT. Identifying new blazars, monitoring their variability, and joining programs to carry out planned or Target of Opportunity multiwavelength campaigns will all be important activities. The study of AGN gamma-ray jets can help link the accretion processes close to the black hole with the large-scale interaction of the AGN with its environment. (2) Unidentified Gamma-ray Sources: Modeling of possible gamma-ray sources is important to establish testable hypotheses. New gamma-ray sources need first to be identified with known objects by position, spectrum, or time variability, and then multiwavelength studies can be used to explore the astrophysical implications of high-energy radiation from these sources. The LAT team is committed to releasing a preliminary source list about six months after the start of science operations.

  18. Non stationary pair model in blazar

    NASA Astrophysics Data System (ADS)

    Marcowith, Alexandre; Henri, Gilles; Renaud, Nicolas

    2001-09-01

    This article shortly present an improved version of pair models for X and gamma-ray emission from blazar jets. The radiations are generated through external and synchrotron Inverse Compton mechanisms in the vicinity of a super-massive black hole by an ultra-relativistic electron-positron pair plasma pervading a non-relativistic electron-proton jet (two-flow model). Non stationary solutions are found by solving simultaneously pair creation/annihilation, soft photon absorption and particle acceleration processes along the jet. The power supply necessary to re-accelerate particles is not treated in a self-consistent procedure but parametrised. Pair creation opacity effects can lead to interesting variability effects depending on the X-ray emission regimes. Multi-wavelength observations by INTEGRAL will provide tests for the model, and also for the matter content and variability mechanisms in compact sources.

  19. Simultaneous multi-wavelength phase-shifting interferometry based on principal component analysis with a color CMOS

    NASA Astrophysics Data System (ADS)

    Fan, Jingping; Lu, Xiaoxu; Xu, Xiaofei; Zhong, Liyun

    2016-05-01

    From a sequence of simultaneous multi-wavelength phase-shifting interferograms (SMWPSIs) recorded by a color CMOS, a principal component analysis (PCA) based multi-wavelength interferometry (MWI) is proposed. First, a sequence of SMWPSIs with unknown phase shifts are recorded with a single-chip color CMOS camera. Subsequently, the wrapped phases of single-wavelength are retrieved with the PCA algorithm. Finally, the unambiguous phase of the extended synthetic wavelength is achieved by the subtraction between the wrapped phases of single-wavelength. In addition, to eliminate the additional phase introduced by the microscope and intensity crosstalk among three-color channels, a two-step phase compensation method with and without the measured object in the experimental system is employed. Compared with conventional single-wavelength phase-shifting interferometry, due to no requirements for phase shifts calibration and the phase unwrapping operation, the actual unambiguous phase of the measured object can be achieved with the proposed PCA-based MWI method conveniently. Both numerical simulations and experimental results demonstrate that the proposed PCA-based MWI method can enlarge not only the measuring range, but also no amplification of noise level.

  20. Swift Multi-wavelength Observing Campaigns: Strategies and Outcomes

    NASA Technical Reports Server (NTRS)

    Krimm, Hans A.

    2007-01-01

    The Swift gamma-ray burst explorer has been operating since December 2004 as both a gamma-ray burst (GRB) monitor and telescope and a multi-wavelength observatory, covering the energy range from V band and near UV to hard X rays above 150 keV. It is designed to rapidly repoint to observe newly discovered GRBs, and this maneuverability, combined with an easily changed observing program, allows Swift to also be an effective multiwavelength observatory for non-GRB targets, both as targets of opportunity and pre-planned multi-wavelength observing campaigns. Blazars are particularly attractive targets for coordinated campaigns with TeV experiments since many blazars are bright in both the hard X-ray and TeV energy ranges. Successful coordinated campaigns have included observations of 3C454.3 during its 2005 outburst. The latest Swift funding cycles allow for non- GRB related observations to be proposed. The Burst Alert Telescope on Swift also serves as a hard X-ray monitor with a public web page that includes light curves for over 400 X-ray sources and is used to alert the astronomical community about increased activity from both known and newly discovered sources. This presentation mill include Swift capabilities, strategies and policies for coordinated multi-wavelength observations as well as discussion of the potential outcomes of such campaigns.

  1. Internal dynamics of the radio-halo cluster A2219: A multi-wavelength analysis

    NASA Astrophysics Data System (ADS)

    Boschin, W.; Girardi, M.; Barrena, R.; Biviano, A.; Feretti, L.; Ramella, M.

    2004-03-01

    We present the results of the dynamical analysis of the rich, hot, and X-ray very luminous galaxy cluster A2219, containing a powerful diffuse radio-halo. Our analysis is based on new redshift data for 27 galaxies in the cluster region, measured from spectra obtained at the TNG, with the addition of other 105 galaxies recovered from reduction of CFHT archive data in a cluster region of ˜5 arcmin radius (˜ 0.8 h-1 Mpc ; at the cluster distance) centered on the cD galaxy. The investigation of the dynamical status is also performed using X-ray data stored in the Chandra archive. Further, valuable information comes from other bands - optical photometric, infrared, and radio data - which are analyzed and/or discussed, too. We find that A2219 appears as a peak in the velocity space at z=0.225, and select 113 cluster members. We compute a high value for the line-of-sight velocity dispersion, σv= 1438+109-86 km s-1, consistent with the high average X-ray temperature of 10.3 keV. If dynamical equilibrium is assumed, the virial theorem leads to M˜2.8× 1015 M⊙ ;sun for the global mass within the virial region. However, further investigation based on both optical and X-ray data shows significant signs of a young dynamical status. In fact, we find strong evidence for the elongation of the cluster in the SE-NW direction coupled with a significant velocity gradient, as well as for the presence of substructure both in optical data and X-ray data. Moreover, we point out the presence of several active galaxies. We discuss the results of our multi-wavelength investigation suggesting a complex merging scenario where the main, original structure is subject to an ongoing merger with a few clumps aligned in a filament in the foreground oriented in an oblique direction with respect to the line-of-sight. Our conclusion supports the view of the connection between extended radio emission and merging phenomena in galaxy clusters. Based on observations made on the island of La Palma

  2. The 'Crazy Diamond' (and other blazars)

    SciTech Connect

    Vercellone, S.; Giuliani, A.

    2009-04-08

    During the first year of observations, AGILE detected several blazars at high significance: 3 C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3 C 273, MKN 421, and W Comae. We obtained long-term coverage of the Crazy Diamond 3 C 454.3, for more than 100 days at energies above 100 MeV. 3 C 273 was the first blazar detected simultaneously by the AGILE gamma-ray imaging detector and by its hard X-ray monitor. S5 0716+714, an intermediate BL Lac object, exhibited a very fast and intense gamma-ray transient event during an optical high-state phase, while MKN 421 and W Comae where detected during an AGILE target of opportunity (ToO) repointing. Thanks to the rapid dissemination of our alerts, we were able to obtain multi-wavelength ToO data from other observatories such as Spitzer, Swift, INTEGRAL, RXTE, Suzaku, MAGIC, VERITAS, as well as optical coverage by means of the WEBT Consortium and REM.

  3. SMARTScience Tools: Interacting With Blazar Data In The Web Browser

    NASA Astrophysics Data System (ADS)

    Hasan, Imran; Isler, Jedidah; Urry, C. Megan; MacPherson, Emily; Buxton, Michelle; Bailyn, Charles D.; Coppi, Paolo S.

    2014-08-01

    The Yale-SMARTS blazar group has accumulated 6 years of optical-IR photometry of more than 70 blazars, mostly bright enough in gamma-rays to be detected with Fermi. Observations were done with the ANDICAM instrument on the SMARTS 1.3 m telescope at the Cerro Tololo Inter-American Observatory. As a result of this long-term, multiwavelength monitoring, we have produced a calibrated, publicly available data set (see www.astro.yale.edu/smarts/glast/home.php), which we have used to find that (i) optical-IR and gamma-ray light curves are well correlated, supporting inverse-Compton models for gamma-ray production (Bonning et al. 2009, 2012), (ii) at their brightest, blazar jets can contribute significantly to the photoionization of the broad-emission-line region, indicating that gamma-rays are produced within 0.1 pc of the black hole in at least some cases (Isler et al. 2014), and (iii) optical-IR and gamma-ray flares are symmetric, implying the time scales are dominated by light-travel-time effects rather than acceleration or cooling (Chatterjee et al. 2012). The volume of data and diversity of projects for which it is used calls out for an efficient means of visualization. To this end, we have developed a suite of visualization tools called SMARTScience Tools, which allow users to interact dynamically with our dataset. The SMARTScience Tools is publicly available via our webpage and can be used to customize multiwavelength light curves and color magnitude diagrams quickly and intuitively. Users can choose specific bands to construct plots, and the plots include features such as band-by-band panning, dynamic zooming, and direct mouse interaction with individual data points. Human and machine readable tables of the plotted data can be directly printed for the user's convenience and for further independent study. The SMARTScience Tools significantly improves the public’s ability to interact with the Yale-SMARTS 6-year data base of blazar photometry, and should make

  4. Performance analysis of incoherent multi-wavelength OCDMA systems under the impact of four-wave mixing.

    PubMed

    Dang, Ngoc T; Pham, Anh T

    2010-05-10

    In this paper, we comprehensively analyze the impact of four wave mixing (FWM) on the performance of incoherent multi-wavelength optical code-division multiple-access (MW-OCDMA) systems. We also consider many other interferences and noises, including multiple access interference, optical beating interference, and receiver noise, in the analysis. From the numerical results, we can find the power ranges of different MW-OCDMA systems, in which the impact of FWM is dominant and consequently results in an increase in the bit-error rate of the systems. We also find that the impact of FWM becomes more severe when the frequency spacing is small and/or dispersion-shifted fiber is used. In addition, we quantitatively discuss the impact of FWM on the number of supportable users and power penalty in the MW-OCDMA systems. PMID:20588844

  5. Computing the Light Periods of Blazars with the Periodogram Spectral Analysis Method

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Zhang, Xiong; Wu, Lin

    2008-04-01

    The periodogram spectral analysis method applicable to equallyspaced time series is discussed, and the method is tested first with a simulated data series. It is confirmed that this method is effective for noisy series. Then, applying this method to the analysis of the light periods of the quasars 3C 279 and 3C 345 as well as the BL Lac objects OJ 287 and ON 231, we obtain their light periods to be 7.14 yr, 10.00 yr, 11.76 yr and 6.80 yr, respectively. These results obtained by periodogram spectral analysis are consistent with those obtained by the Jurkevich method in the literature. We have analyzed the effects of different window functions, and commented on their correct selection in practical applications.

  6. The GTN-AAVSO Blazar Program

    NASA Astrophysics Data System (ADS)

    Cominsky, L. R.; Spear, G. G.; Graves, T.; Slater, G.; Price, A.

    2004-08-01

    The GLAST Telescope Network (GTN) is a collaboration among students, teachers, amateur astronomers, small college observatories, and professional astronomers who will obtain observations of base-line activity levels and follow-up observations for bright blazars, one of the key science objectives for NASA's Gamma-ray Large Area Space Telescope (GLAST) mission. A key partner in the GTN is the American Association of Variable Star Observers (AAVSO, a non-profit international scientific and educational organization that has considerable experience with handling, processing, and displaying large amounts of data and with coordinating observers from every corner of the globe. The GTN-AAVSO blazar program will recommend observing sequences, and provide advice and mentoring for observing techniques and data reduction. The program will archive magnitude estimates using the AAVSO database system and lightcurve generator, as well as CCD images of blazar fields. The program will also employ the online image archiving system developed by the GTN. Images of blazar fields will be available for subsequent analysis by contributors to the program, and by the GLAST science team for mission planning and follow-up studies. We will present examples of the AAVSO lightcurve generator, examples of the GTN image archive system, plus examples of the data we are currently accumulating. The GTN-AAVSO collaboration is partially funded by the NASA's GLAST Education and Public Outreach Program.

  7. VERITAS and multiwavelength observations of the BL Lacertae object 1ES 1741+196

    NASA Astrophysics Data System (ADS)

    Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; Christiansen, J. L.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dickinson, H. J.; Dumm, J.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Flinders, A.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Huetten, M.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Brien, S.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Park, N.; Pelassa, V.; Petrashyk, A.; Petry, D.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Ratliff, G.; Reyes, L. C.; Reynolds, P. T.; Reynolds, K.; Richards, G. T.; Roache, E.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; Zitzer, B.

    2016-07-01

    We present results from multiwavelength observations of the BL Lacertae object 1ES 1741 + 196, including results in the very high energy γ-ray regime using the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The VERITAS time-averaged spectrum, measured above 180 GeV, is well modelled by a power law with a spectral index of 2.7 ± 0.7stat ± 0.2syst. The integral flux above 180 GeV is (3.9 ± 0.8stat ± 1.0syst) × 10-8 m-2 s-1, corresponding to 1.6 per cent of the Crab nebula flux on average. The multiwavelength spectral energy distribution of the source suggests that 1ES 1741+196 is an extreme-high-frequency-peaked BL Lacertae object. The observations analysed in this paper extend over a period of six years, during which time no strong flares were observed in any band. This analysis is therefore one of the few characterizations of a blazar in a non-flaring state.

  8. Multiwavelength Observations of Mrk 501 in 2008

    SciTech Connect

    Kranich, D.; Paneque, D.; Cesarini, A.; Falcone, A.; Giroletti, M.; Hoversten, E.; Hovatta, T.; Kovalev, Y.Y.; Lahteenmaki, A.; Nieppola, E.; Pagani, C.; Pichel, A.; Satalecka, K.; Scargle, J.; Steele, D.; Tavecchio, F.; Tescaro, D.; Tornikoski, M.; Villata, M.; /Turin Observ.

    2010-08-25

    The well-studied VHE (E > 100 GeV) blazar Mrk 501 was observed between March and May 2008 as part of an extensive multiwavelength observation campaign including radio, optical, X-ray and VHE gamma-ray instruments. Mrk 501 was in a low state of activity during the campaign, with a low VHE flux of about 20% the Crab Nebula flux. Nevertheless, significant flux variations could be observed in X-rays as well as {gamma}-rays. Overall Mrk 501 showed increased variability when going from radio to {gamma}-ray energies. The broadband spectral energy distribution during the two different emission states of the campaign was well described by a homogeneous one-zone synchrotron self-Compton model. The high emission state was satisfactorily modeled by increasing the amount of high energy electrons with respect to the low emission state. This parameterization is consistent with the energy-dependent variability trend observed during the campaign.

  9. A multiwavelength analysis of planetary nebulae in the Large Magellanic Cloud

    NASA Astrophysics Data System (ADS)

    Reid, Warren A.

    2014-03-01

    This paper examines, compares and plots optical, near- and mid-infrared (MIR) photometric data for 605 planetary nebulae (PNe) in the Large Magellanic Cloud (LMC). With the aid of multiwavelength surveys such as the Spitzer legacy programme Surveying the Agents of a Galaxy's Evolution, the Two Micron All Sky Survey and the Magellanic Cloud Photometric Survey, plots have been constructed to expose the relative contributions from molecular hydrogen, polycyclic aromatic hydrocarbons, forbidden emission lines, warm dust continuum and stellar emission at various bands. Besides identifying trends, these plots have helped to reveal PN mimics including six previously known PNe in the outer LMC which are re-classified as other object types. Together with continuing follow-up optical observations, the data have enabled a substantial reduction in the number of PNe previously tagged as `likely' and `possible'. The total number of LMC PNe is adjusted to 715 but with a greater degree of confidence in regard to classification. In each colour-colour plot, the more highly evolved LMC PNe are highlighted for comparison with younger, brighter PNe. The faintest and most evolved PNe typically cluster in areas of colour-colour space occupied by ordinary stars. Possible reasons for the wide disparity in infrared colour-colour ratios, such as evolution and dust composition, are presented for evaluation. A correlation is found between the optical luminosity of PNe, emission-line ratios and the MIR dust luminosity at various bands. Luminosity functions using the four Infrared Array Camera and Multiband Imaging Photometer of Spitzer (MIPS) [24] bands are directly compared, revealing an increasing accumulation of PNe within the brightest two magnitudes at longer wavelengths. A correlation is also found between the MIPS [24] band and the [O III] 5007 and Hβ fluxes.

  10. Jet and accretion power in the most powerful Fermi blazars

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Tavecchio, F.; Ghirlanda, G.

    2009-11-01

    Among the blazars detected by the Fermi satellite, we have selected the 23 blazars that in the 3months of survey had an average γ-ray luminosity above 1048ergs-1. For 17 out of the 23 sources we found and analysed X-ray and optical-ultraviolet data taken by the Swift satellite. With these data, implemented by archival and not simultaneous data, we construct the spectral energy distributions, and interpreted them with a simple one-zone, leptonic, synchrotron and inverse Compton model. When possible, we also compare different high-energy states of single sources, like 0528+134 and 3C454.3, for which multiple good sets of multiwavelength data are available. In our powerful blazars the high energy emission always dominates the electromagnetic output, and the relatively low level of the synchrotron radiation often does not hide the accretion disc emission. We can then constrain the black hole mass and the disc luminosity. Both are large (i.e. masses equal or greater than 109M solar and disc luminosities above 10 per cent of Eddington). By modelling the non-thermal continuum we derive the power that the jet carries in the form of bulk motion of particles and fields. On average, the jet power is found to be slightly larger than the disc luminosity, and proportional to the mass accretion rate.

  11. Probing Turbulence and Acceleration at Relativistic Shocks in Blazar Jets

    NASA Astrophysics Data System (ADS)

    Baring, Matthew G.; Boettcher, Markus; Summerlin, Errol J.

    2016-04-01

    Acceleration at relativistic shocks is likely to be important in various astrophysical jet sources, including blazars and other radio-loud active galaxies. An important recent development for blazar science is the ability of Fermi-LAT data to pin down the power-law index of the high energy portion of emission in these sources, and therefore also the index of the underlying non-thermal particle population. This paper highlights how multiwavelength spectra including X-ray band and Fermi data can be used to probe diffusive acceleration in relativistic, oblique, MHD shocks in blazar jets. The spectral index of the non-thermal particle distributions resulting from Monte Carlo simulations of shock acceleration, and the fraction of thermal particles accelerated to non-thermal energies, depend sensitively on the particles' mean free path scale, and also on the mean magnetic field obliquity to the shock normal. We investigate the radiative synchrotron/Compton signatures of thermal and non-thermal particle distributions generated from the acceleration simulations. Important constraints on the frequency of particle scattering and the level of field turbulence are identified for the jet sources Mrk 501, AO 0235+164 and Bl Lacertae. Results suggest the interpretation that turbulence levels decline with remoteness from jet shocks, with a significant role for non-gyroresonant diffusion.

  12. The effect of Brown Carbon on thermal-optical analysis: a correction based on optical multi-wavelength analysis

    NASA Astrophysics Data System (ADS)

    Dario, Massabò; Lorenzo, Caponi; Chiara, Bove Maria; Paolo, Prati

    2016-04-01

    Carbonaceous aerosol (CA) has an important impact on air quality, human health and climate change. Total Carbon (TC) is generally divided in organic carbon (OC) and elemental carbon (EC) (although a minor fraction of carbonate carbon (CC) may be present). This classification is based on their thermo-optical properties: while EC is strongly light absorbing, OC is generally transparent in the visible range except for some particular compounds. In fact, another fraction of light-absorbing organic carbon exists which is not black and is generally called brown carbon (BrC) (Andreae and Gelencsér, 2006). We recently introduced a new method to apportion the absorption coefficient (babs) of carbonaceous atmospheric aerosols starting from multi-wavelength optical analysis (Massabò et al., 2015). This analysis is performed by the MWAA, an instrument developed at the Physics Department of University of Genoa (Massabò et al., 2013) able to measure the aerosol absorption coefficient at 5 different wavelengths ranging from UV to IR. The method is based on the information gathered at these five different wavelengths, in a renewed and upgraded version of the approach usually referred to as Aethalometer model (Sandradewi et al., 2008). The resulting optical apportionment provides the quantification of EC and, with some assumptions, also of OC coming from fossil fuels and wood burning. Thermal-optical methods are presently the most widespread approach to OC/EC speciation. Despite their popularity, there is still a disagreement among the results, especially for what concerns EC as different thermal protocols can be used. In fact, the pyrolysis occurring during the analysis can heavily affect OC/EC separation, depending on PM composition in addition to the used protocol. Furthermore, the presence in the sample of BrC can shift the split point since it is light absorbing also @ 635nm, the typical laser wavelength used in this technique (Chen et al., 2015). We present here the

  13. The nature of transition blazars

    SciTech Connect

    Ruan, J. J.; Anderson, S. F.; Plotkin, R. M.; Brandt, W. N.; Schneider, D. P.; Burnett, T. H.; Myers, A. D.

    2014-12-10

    Blazars are classically divided into the BL Lacertae (BLL) and flat-spectrum radio quasar (FSRQ) subclasses, corresponding to radiatively inefficient and efficient accretion regimes, respectively, largely based on the equivalent width (EW) of their optical broad emission lines (BELs). However, EW-based classification criteria are not physically motivated, and a few blazars have previously transitioned' from one subclass to the other. We present the first systematic search for these transition blazars in a sample of 602 unique pairs of repeat spectra of 354 blazars in the Sloan Digital Sky Survey, finding six clear cases. These transition blazars have bolometric Eddington ratios of ∼0.3 and low-frequency synchrotron peaks, and are thus FSRQ-like. We show that the strong EW variability (up to an unprecedented factor of >60) is due to swamping of the BELs from variability in jet continuum emission, which is stronger in amplitude and shorter in timescale than typical blazars. Although these transition blazars appear to switch between FSRQ and BLL according to the phenomenologically based EW scheme, we show that they are most likely rare cases of FSRQs with radiatively efficient accretion flows and especially strongly beamed jets. These results have implications for the decrease of the apparent BLL population at high redshifts, and may lend credence to claims of a negative BLL redshift evolution.

  14. RoboPol: blazar astrophysics from Skinakas with a unique optical

    NASA Astrophysics Data System (ADS)

    Pavlidou, V.

    2013-09-01

    Blazars are the most active galaxies known. They are powered by relativistic jets of matter speeding towards us almost head-on at the speed of light, radiating exclusively through extreme, non-thermal particle interactions, energized by accretion onto supermassive black holes. Despite intensive observational and theoretical efforts over the last four decades, the details of blazar astrophysics remain elusive. The launch of NASA's Fermi Gamma-ray Space Telescope in 2008 has provided an unprecedented opportunity for the systematic study of blazar jets and has prompted large-scale blazar monitoring efforts across wavelengths. In such a multi-wavelength campaign, a novel effect was discovered: fast changes in the optical polarization during gamma-ray flares. Such events probe the magnetic field structure in the jet and the evolution of disturbances responsible for blazar flares. Their systematic study can answer long-standing questions in our theoretical understanding of jets; however, until recently, optical polarimetry programs in operation were not adequate to find and follow similar events with the efficiency and time-resolution needed. RoboPol is a massive program of optical polarimetric monitoring of over 100 blazars, using an innovative, specially-designed and built polarimeter mounted on the 1.3 m telescope at Skinakas Observatory, a dynamical observing schedule, and a large amount of dedicated telescope time. The program is a collaboration between the University of Crete and the Foundation for Research and Technology - Hellas in Greece, the Max-Planck Institute for Radioastronomy in Germany, Caltech in the US, the Nicolaus Copernicus University in Poland, and the Inter-University Centre for Astronomy and Astrophysics in India. The instrument was successfully commissioned in March of 2013 and has been taking data since. In this talk we will review the RoboPol program, its potential for discovery in blazar astrophysics, and we will present results from its first

  15. AGN Winds and Blazar Phenomenology

    NASA Technical Reports Server (NTRS)

    Kazanas, Demos

    2012-01-01

    The launch of {\\em Fermi} produced a significant number of AGN detections to allow statistical treatment of their properties. One of the first such systematics was the "Blazar Divide" in FSRQs and BL Lacs according to their gamma-ray spectral index and luminosity. Further data accumulation indicated this separation to be less clear than thought before. An MHD wind model which can model successfully the Seyfert X-ray absorber properties provides the vestiges of an account of the observed blazar classification. We propose to employ this model to model in detail the broad band blazar spectra and their statistical properties in terms of the physical parameters of these MHD winds.

  16. TIME SERIES ANALYSIS OF GAMMA-RAY BLAZARS AND IMPLICATIONS FOR THE CENTRAL BLACK-HOLE MASS

    SciTech Connect

    Nakagawa, Kenji; Mori, Masaki

    2013-08-20

    Radiation from the blazar class of active galactic nuclei (AGNs) exhibits fast time variability which is usually ascribed to instabilities in the emission region near the central supermassive black hole. The variability time scale is generally faster in higher energy region, and data recently provided by the Fermi Gamma-ray Space Telescope in the GeV energy band enable a detailed study of the temporal behavior of AGN. Due to its wide field-of-view in the scanning mode, most sky regions are observed for several hours per day and daily light curves of many AGNs have been accumulated for more than 4 yr. In this paper we investigate the time variability of 15 well-detected AGNs by studying the normalized power spectrum density of their light curves in the GeV energy band. One source, 3C 454.3, shows a specific time scale of 6.8 Multiplication-Sign 10{sup 5} s, and this value suggests, assuming the internal shock model, a mass for the central black hole of (10{sup 8}-10{sup 10}) M{sub Sun} which is consistent with other estimates. It also indicates the typical time interval of ejected blobs is (7-70) times the light crossing time of the Schwarzschild radius.

  17. Time Series Analysis of Gamma-Ray Blazars and Implications for the Central Black-hole Mass

    NASA Astrophysics Data System (ADS)

    Nakagawa, Kenji; Mori, Masaki

    2013-08-01

    Radiation from the blazar class of active galactic nuclei (AGNs) exhibits fast time variability which is usually ascribed to instabilities in the emission region near the central supermassive black hole. The variability time scale is generally faster in higher energy region, and data recently provided by the Fermi Gamma-ray Space Telescope in the GeV energy band enable a detailed study of the temporal behavior of AGN. Due to its wide field-of-view in the scanning mode, most sky regions are observed for several hours per day and daily light curves of many AGNs have been accumulated for more than 4 yr. In this paper we investigate the time variability of 15 well-detected AGNs by studying the normalized power spectrum density of their light curves in the GeV energy band. One source, 3C 454.3, shows a specific time scale of 6.8 × 105 s, and this value suggests, assuming the internal shock model, a mass for the central black hole of (108-1010) M ⊙ which is consistent with other estimates. It also indicates the typical time interval of ejected blobs is (7-70) times the light crossing time of the Schwarzschild radius.

  18. The GTN-AAVSO Blazar Program

    NASA Astrophysics Data System (ADS)

    Spear, G. G.; Mattei, J. A.; Price, A.; Graves, T.; Borders, T.; Slater, G.; Cominsky, L. R.

    2002-12-01

    The GLAST Telescope Network (GTN) is a collaboration among observers and small observatories who will obtain observations of base-line activity levels and follow-up observations for bright blazars. These AGNs have their jets pointed directly toward us, and are one of the key science objectives for NASA's Gamma-ray Large Area Space Telescope (GLAST) mission. Funded by the GLAST Education and Public Outreach Program, the GTN consists of students, teachers, amateur astronomers, small college observatories, and professional astronomers. The American Association of Variable Star Observers (AAVSO) is a non-profit international scientific and educational organization of thousands of advanced amateur and professional astronomers interested in stars or star-like objects that change in brightness. With millions of variable star observations dating back more than 90 years, the AAVSO has unique experience with handling, processing, and displaying large amounts of data and with coordinating observers from every corner of the globe. The GTN-AAVSO blazar program will recommend observing programs, and provide advice and mentoring for observing techniques and data reduction. The program will archive magnitude estimates and measurements of blazars, as well as CCD images of blazar fields. The GTN-AAVSO program will employ the AAVSO database system and lightcurve generator (http://www.aavso.org/adata/curvegenerator.shtml) to archive magnitude estimates. The magnitudes will either be visual estimates or CCD measurements. Magnitudes are submitted online, and will be immediately available to the public for use in planning observing programs and estimating current activity levels. The GTN-AAVSO program will also employ the online image archiving system developed by the GTN. Images of blazar fields will be available for subsequent analysis by contributors to the program, and by the GLAST science team for mission planning and follow-up studies. We will present examples of the AAVSO

  19. Monitoring of Bright Blazars with MAGIC in the 2007/2008 Season

    SciTech Connect

    Satalecka, Konstancja; Bernardini, Elisa; Majumdar, Pratik; Hsu, Ching-Cheng; Galante, Nicola; Goebel, Florian; Wagner, Robert; Bonnoli, Giacomo; Stamerra, Antonio; Lindfors, Elina

    2009-04-08

    Because of the short duty-cycles and observation-time constraints, studies of bright TeV (E>100 GeV) blazars are mostly restricted to flaring episodes or rather short (days to few weeks) multiwavelength campaigns. At the same time, long-term studies of these objects are essential to gain a more complete understanding of the blazar phenomenon and to constrain theoretical models concerning jet physics. Only unbiased long-term studies are adequate for the determination of flaring state probabilities and for estimating the statistical significance of possible correlations between TeV flaring states and other wavebands or observables, such as neutrino events. Regular observations also provide triggers for multiwavelength ToO observations originating from the TeV waveband. These are particularly needed to identify and study orphan TeV flares, i.e. flares without counterparts in other wavebands. In 2007/8 the MAGIC telescope has monitored three TeV blazars on a regular basis: Mrk 501, Mrk 421, and 1ES 1959+650. We present preliminary results of these observations including the measured light curves and a correlation study for VHE {gamma}-rays and X-rays and VHE {gamma}-rays and optical R-band for Mrk 421.

  20. Analysis of complex samples using a portable multi-wavelength light emitting diode (LED) fluorescence spectrometer

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Spectroscopic analysis of chemically complex samples often requires an increase n the dimensionality of the measured response surface. This often involves the measurement of emitted light intensities as functions of both wavelengths of excitation and emission resulting in the generation of an excita...

  1. Multi-wavelength optical measurement to enhance thermal/optical analysis for carbonaceous aerosol

    NASA Astrophysics Data System (ADS)

    Chen, L.-W. A.; Chow, J. C.; Wang, X. L.; Robles, J. A.; Sumlin, B.; Lowenthal, D. H.; Zimmermann, R.; Watson, J. G.

    2014-09-01

    A thermal/optical carbon analyzer equipped with seven-wavelength light source/detector (405-980 nm) for monitoring spectral reflectance (R) and transmittance (T) of filter samples allows "thermal spectral analysis (TSA)" and wavelength (λ)-dependent organic carbon (OC)-elemental carbon (EC) measurements. Optical sensing is calibrated with transfer standards traceable to absolute R and T measurements and adjusted for loading effects to determine spectral light absorption (as absorption optical depth [τa, λ]) using diesel exhaust samples as a reference. Tests on ambient and source samples show OC and EC concentrations equivalent to those from conventional carbon analysis when based on the same wavelength (~635 nm) for pyrolysis adjustment. TSA provides additional information that evaluates black carbon (BC) and brown carbon (BrC) contributions and their optical properties in the near-IR to the near-UV parts of the solar spectrum. The enhanced carbon analyzer can add value to current aerosol monitoring programs and provide insight into more accurate OC and EC measurements for climate, visibility, or health studies.

  2. Multi-wavelength optical measurement to enhance thermal/optical analysis for carbonaceous aerosol

    NASA Astrophysics Data System (ADS)

    Chen, L.-W. A.; Chow, J. C.; Wang, X. L.; Robles, J. A.; Sumlin, B. J.; Lowenthal, D. H.; Zimmermann, R.; Watson, J. G.

    2015-01-01

    A thermal/optical carbon analyzer equipped with seven-wavelength light source/detector (405-980 nm) for monitoring spectral reflectance (R) and transmittance (T) of filter samples allowed "thermal spectral analysis (TSA)" and wavelength (λ)-dependent organic-carbon (OC)-elemental-carbon (EC) measurements. Optical sensing was calibrated with transfer standards traceable to absolute R and T measurements, adjusted for loading effects to report spectral light absorption (as absorption optical depth (τa, λ)), and verified using diesel exhaust samples. Tests on ambient and source samples show OC and EC concentrations equivalent to those from conventional carbon analysis when based on the same wavelength (~ 635 nm) for pyrolysis adjustment. TSA provides additional information that evaluates black-carbon (BC) and brown-carbon (BrC) contributions and their optical properties in the near infrared to the near ultraviolet parts of the solar spectrum. The enhanced carbon analyzer can add value to current aerosol monitoring programs and provide insight into more accurate OC and EC measurements for climate, visibility, or health studies.

  3. A multi-wavelength scattered light analysis of the dust grain population in the GG Tau circumbinary ring

    SciTech Connect

    Duchene, G; McCabe, C; Ghez, A; Macintosh, B

    2004-02-04

    We present the first 3.8 {micro}m image of the dusty ring surrounding the young binary system GG Tau, obtained with the W. M. Keck II 10m telescope's adaptive optics system. THis is the longest wavelength at which the ring has been detected in scattered light so far, allowing a multi-wavelength analysis of the scattering proiperties of the dust grains present in this protoplanetary disk in combination with previous, shorter wavelengths, HST images. We find that the scattering phase function of the dust grains in the disk is only weakly dependent on the wavelength. This is inconsistent with dust models inferred from observations of the interstellar medium or dense molecular clouds. In particular, the strongly forward-throwing scattering phase function observed at 3.8 {micro}m implies a significant increase in the population of large ({approx}> 1 {micro}m) grains, which provides direct evidence for grain growth in the ring. However, the grain size distribution required to match the 3.8 {micro}m image of the ring is incompatible with its published 1 {micro}m polarization map, implying that the dust population is not uniform throughout the ring. We also show that our 3.8 {micro}m image of the ring is incompatible with its published 1 {micro}m polarization map, implying that the dust population is not uniform throughout the ring. We also show that our 3.8 {micro}m scattered light image probes a deeper layer of the ring than previous shorter wavelength images, as demonstrated by a shift in the location of the inner edge of the disk's scattered light distribution between 1 and 3.8 {micro}m. We therefore propose a stratified structure for the ring in which the surface layers, located {approx} 50 AU above the ring midplane, contain dust grains that are very similar to those found in dense molecular clouds, while the region of the ring located {approx} 25 AU from the midplane contains significantly larger grains. This stratified structure is likely the result of vertical

  4. MHD-based modeling of radiation and polarization signatures of blazar emission

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Li, Hui; Boettcher, Markus

    2016-04-01

    Observations have shown that sometimes strong multiwavelength flares are accompanied by drastic polarization variations, indicating active participation of magnetic fields during flares. We have developed a 3D numerical tool set of magnetohydrodynamics, Fokker-Planck particle evolution, and polarization-dependent radiation transfer codes. This allows us to study the snap-shot spectra, multiwavelength light curves, and time-dependent optical polarization signatures self-consistently. We have made a simultaneous fit of a multiwavelength flare with 180 degree polarization angle swing of the blazar 3C279 reported by Abdo et al. 2010. Our work has shown that this event requires an increase in the nonthermal particles, a decrease in the magnetic field strength, and a change in the magnetic field structure. We conclude that this event is likely due to a shock-initiated magnetic reconnection in an emission environment with relatively strong magnetic energy. We have performed magnetrohydrodynamic simulations to support this statement. Our simulations have found that the blazar emission region may be strongly magnetized. In this situation, polarization angle swings are likely to be correlated with strong gamma-ray flares.

  5. 3D fingerprint analysis using transmission-mode multi-wavelength digital holographic topography

    NASA Astrophysics Data System (ADS)

    Abeywickrema, Ujitha; Banerjee, Partha; Kota, Akash; Lakhtakia, Akhlesh; Swiontek, Stephen E.

    2016-03-01

    The analysis of fingerprints is important for biometric identification. Two-wavelength digital holographic interferometry is used to study the topography of various types of fingerprints. This topography depends on several conditions such as the temperature, time of the day, and the proportions of eccrine and sebaceous sweat. With two-wavelength holographic interferometry, surface information can be measured with a better accuracy compared to single-wavelength phase-retrieving techniques. Latent fingerprints on transparent glass, a forensically relevant substrate are first developed by the deposition of 50-1000-nm-thick columnar thin films, and then analyzed using the transmission-mode two-wavelength digital holographic technique. In this technique, a tunable Argon-ion laser (457.9 nm to 514.5 nm) is used and holograms are recorded on a CCD camera sequentially for several sets of two wavelengths. Then the phase is reconstructed for each wavelength, and the phase difference which corresponds to the synthetic wavelength (4 μm to 48 μm) is calculated. Finally, the topography is obtained by applying proper phase-unwrapping techniques to the phase difference. Interferometric setups that utilize light reflected from the surface of interest have several disadvantages such as the effect of multiple reflections as well as the effects of the tilt of the object and its shadow (for the Mach-Zehnder configuration). To overcome these drawbacks, digital holograms of fingerprints in a transmission geometry are used. An approximately in-line geometry employing a slightly tilted reference beam to facilitate separation of various diffraction orders during holographic reconstruction is employed.

  6. Gamma-ray blazars: The view from AGILE

    NASA Astrophysics Data System (ADS)

    D'Ammando, F.; Bulgarelli, A.; Chen, A. W.; Donnarumma, I.; Giuliani, A.; Longo, F.; Pacciani, L.; Pucella, G.; Striani, E.; Tavani, M.; Vercellone, S.; Vittorini, V.; Covino, S.; Krimm, H. A.; Raiteri, C. M.; Romano, P.; Villata, M.

    2011-07-01

    During the first 3 years of operation the Gamma-Ray Imaging Detector onboard the AGILE satellite detected several blazars in a high γ-ray activity: 3C 279, 3C 454.3, PKS 1510-089, S5 0716+714, 3C 273, W Comae, Mrk 421, PKS 0537-441 and 4C +21.35. Thanks to the rapid dissemination of our alerts, we were able to obtain multiwavelength data from other observatories such as Spitzer, Swift, RXTE, Suzaku, INTEGRAL, MAGIC, VERITAS, and ARGO as well as radio-to-optical coverage by means of the GASP Project of the WEBT and the REM Telescope. This large multifrequency coverage gave us the opportunity to study the variability correlations between the emission at different frequencies and to obtain simultaneous Spectral Energy Distributions of these sources from radio to γ-ray energy bands, investigating the different mechanisms responsible for their emission and uncovering in some cases a more complex behavior with respect to the standard models. We present a review of the most interesting AGILE results on these γ-ray blazars and their multifrequency data.

  7. TANAMI blazars in the IceCube PeV-neutrino fields

    NASA Astrophysics Data System (ADS)

    Krauß, F.; Kadler, M.; Mannheim, K.; Schulz, R.; Trüstedt, J.; Wilms, J.; Ojha, R.; Ros, E.; Anton, G.; Baumgartner, W.; Beuchert, T.; Blanchard, J.; Bürkel, C.; Carpenter, B.; Eberl, T.; Edwards, P. G.; Eisenacher, D.; Elsässer, D.; Fehn, K.; Fritsch, U.; Gehrels, N.; Gräfe, C.; Großberger, C.; Hase, H.; Horiuchi, S.; James, C.; Kappes, A.; Katz, U.; Kreikenbohm, A.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Litzinger, E.; Lovell, J. E. J.; Müller, C.; Phillips, C.; Plötz, C.; Quick, J.; Steinbring, T.; Stevens, J.; Thompson, D. J.; Tzioumis, A. K.

    2014-06-01

    The IceCube Collaboration has announced the discovery of a neutrino flux in excess of the atmospheric background. Owing to the steeply falling atmospheric background spectrum, events at PeV energies most likely have an extraterrestrial origin. We present the multiwavelength properties of the six radio-brightest blazars that are positionally coincident with these events using contemporaneous data of the TANAMI blazar sample, including high-resolution images and spectral energy distributions. Assuming the X-ray to γ-ray emission originates in the photoproduction of pions by accelerated protons, the integrated predicted neutrino luminosity of these sources is high enough to explain the two detected PeV events. Tables 1-3 are available in electronic form at http://www.aanda.org

  8. Near-IR brightening of the blazar CTA 102 (2230+114) observed by the GASP

    NASA Astrophysics Data System (ADS)

    Carnerero, M. I.; Acosta-Pulido, J. A.; Arevalo, M. J.; Bueno, A.; Gonzalez, A. I.; Puerto-Gimenez, I.; Raiteri, C. M.; Villata, M.; GASP Collaboration

    2012-06-01

    The GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reports on the recent observation of a strong near-IR brightening of the gamma-loud quasar CTA 102. This is one of the 28 blazars for which the GASP performs a long-term, multiwavelength monitoring. Observations performed at the Teide Observatory on 2012 June 5.2 UT revealed J = 14.02 +/- 0.02, H = 13.19 +/- 0.02, and Ks = 12.36 +/- 0.02, compared to J = 15.42 +/- 0.04, H = 14.99 +/- 0.04, and Ks = 14.30 +/- 0.06 measured on 2011 December 5.9 UT.

  9. AGILE detection of extreme γ-ray activity from the blazar PKS 1510-089 during March 2009. Multifrequency analysis

    NASA Astrophysics Data System (ADS)

    D'Ammando, F.; Raiteri, C. M.; Villata, M.; Romano, P.; Pucella, G.; Krimm, H. A.; Covino, S.; Orienti, M.; Giovannini, G.; Vercellone, S.; Pian, E.; Donnarumma, I.; Vittorini, V.; Tavani, M.; Argan, A.; Barbiellini, G.; Boffelli, F.; Bulgarelli, A.; Caraveo, P.; Cattaneo, P. W.; Chen, A. W.; Cocco, V.; Costa, E.; Del Monte, E.; de Paris, G.; Di Cocco, G.; Evangelista, Y.; Feroci, M.; Ferrari, A.; Fiorini, M.; Froysland, T.; Frutti, M.; Fuschino, F.; Galli, M.; Gianotti, F.; Giuliani, A.; Labanti, C.; Lapshov, I.; Lazzarotto, F.; Lipari, P.; Longo, F.; Marisaldi, M.; Mereghetti, S.; Morselli, A.; Pacciani, L.; Pellizzoni, A.; Perotti, F.; Piano, G.; Picozza, P.; Pilia, M.; Porrovecchio, G.; Prest, M.; Rapisarda, M.; Rappoldi, A.; Rubini, A.; Sabatini, S.; Soffitta, P.; Striani, E.; Trifoglio, M.; Trois, A.; Vallazza, E.; Zambra, A.; Zanello, D.; Agudo, I.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Bach, U.; Benitez, E.; Berdyugin, A.; Blinov, D. A.; Buemi, C. S.; Chen, W. P.; di Paola, A.; Dolci, M.; Forné, E.; Fuhrmann, L.; Gómez, J. L.; Gurwell, M. A.; Jordan, B.; Jorstad, S. G.; Heidt, J.; Hiriart, D.; Hovatta, T.; Hsiao, H. Y.; Kimeridze, G.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kurtanidze, O. M.; Kurtanidze, S. O.; Larionov, V. M.; Lähteenmäki, A.; Leto, P.; Lindfors, E.; Marscher, A. P.; McBreen, B.; McHardy, I. M.; Morozova, D. A.; Nilsson, K.; Pasanen, M.; Roca-Sogorb, M.; Sillanpää, A.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Troitsky, I. S.; Umana, G.; Antonelli, L. A.; Colafrancesco, S.; Pittori, C.; Santolamazza, P.; Verrecchia, F.; Giommi, P.; Salotti, L.

    2011-05-01

    We report on the extreme γ-ray activity from the flat spectrum radio quasar (FSRQ) PKS 1510-089 observed by the AGILE satellite in March 2009. In the same period a radio-to-optical monitoring of the source was provided by the GASP-WEBT and REM facilities. In the radio band we made use also of multi-epoch 15-GHz Very Long Baseline Array data from the MOJAVE Program to get information on the parsec-scale structure. Moreover, several Swift target of opportunity observations were triggered, adding important information on the source behaviour from optical/UV to hard X-rays. We paid particular attention to the calibration of the Swift/UVOT data to make it suitable to the blazars spectra. Simultaneous observations from radio to γ rays allowed us to study in detail the correlation among the emission variability at differentfrequencies and to investigate the mechanisms at work during this high activity state of the source. In the period 9-30 March 2009, AGILE detected γ-ray emission from PKS 1510-089 at a significance level of 21.5-σ with an average flux over the entire period of (311 ± 21) × 10-8 photons cm-2 s-1 for photon energies above 100 MeV, and a peak level of (702 ± 131) × 10-8 photons cm-2 s-1 on daily integration. The activity detected in γ rays occurred during a period of increasing activity from near-infrared to UV, as monitored by GASP-WEBT, REM and Swift/UVOT. A flaring episode on 26-27 March 2009 was detected from near-IR to UV, suggesting that a single mechanism is responsible for the flux enhancement observed at the end of March. By contrast, Swift/XRT observations seem to show no clear correlation of the X-ray fluxes with the optical and γ-ray ones. However, the X-ray observations show a harder photon index (Γx ≃ 1.3-1.6) with respect to most FSRQs and a hint of harder-when-brighter behaviour, indicating the possible presence of a second emission component at soft X-ray energies. Moreover, the broad band spectrum from radio-to-UV confirmed

  10. Blazars at Low Radio Frequencies

    NASA Astrophysics Data System (ADS)

    Trüstedt, J.; Kadler, M.; Brüggen, M.; Falcke, H.; Heald, G.; McKean, J.; Mueller, C.; Ros, E.; Schulz, R.; Wilms, J.

    We explore the low radio-frequency properties of the MOJAVE 1 blazar sample using the LOFAR Multi-Frequency Snapshot Sky Survey (MSSS). We find the characteristically flat blazar spectrum to extend down to the LOFAR bands, demonstrating that the emission at these low radio frequencies is still dominated by relativistically beamed emission. As most sources remain unresolved at the MSSS angular resolution, we are reimaging these data using LOFAR baselines beyond the standard MSSS uv-range resulting in an angular resolution of ~24 arcsec. We present first LOFAR images of MOJAVE sources from this project.

  11. HERSCHEL PACS AND SPIRE OBSERVATIONS OF BLAZAR PKS 1510-089: A CASE FOR TWO BLAZAR ZONES

    SciTech Connect

    Nalewajko, Krzysztof; Sikora, Marek; Madejski, Greg M.; Szostek, Anna; Szczerba, Ryszard; Kidger, Mark R.; Lorente, Rosario

    2012-11-20

    We present the results of observations of blazar PKS 1510-089 with the Herschel Space Observatory PACS and SPIRE instruments, together with multiwavelength data from Fermi/LAT, Swift, SMARTS, and Submillimeter Array. The source was found in a quiet state, and its far-infrared spectrum is consistent with a power law with a spectral index of {alpha} {approx_equal} 0.7. Our Herschel observations were preceded by two 'orphan' gamma-ray flares. The near-infrared data reveal the high-energy cutoff in the main synchrotron component, which cannot be associated with the main gamma-ray component in a one-zone leptonic model. This is because in such a model the luminosity ratio of the external-Compton (EC) and synchrotron components is tightly related to the frequency ratio of these components, and in this particular case an unrealistically high energy density of the external radiation would be implied. Therefore, we consider a well-constrained two-zone blazar model to interpret the entire data set. In this framework, the observed infrared emission is associated with the synchrotron component produced in the hot-dust region at the supra-parsec scale, while the gamma-ray emission is associated with the EC component produced in the broad-line region at the sub-parsec scale. In addition, the optical/UV emission is associated with the accretion disk thermal emission, with the accretion disk corona likely contributing to the X-ray emission.

  12. The Blazar's Divide and the Properties of Fermi Blazars

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.

    2010-10-01

    The LAT instrument, onboard the Fermi satellite, in its first three months of operation detected more than 100 blazars at more than the 10σ level. This is already a great improvement with respect to its predecessor, the instrument EGRET onboard the Compton Gamma Ray Observatory. Observationally, the new detections follow and confirm the so-called blazar sequence, relating the bolometric observed non-thermal luminosity to the overall shape of the spectral energy distribution. We have studied the general physical properties of all these bright Fermi blazars, and found that their jets are matter dominated, carrying a large total power that correlates with the luminosity of their accretion disks. We suggest that the division of blazars into the two subclasses of broad line emitting objects (Flat Spectrum Radio Quasars) and line-less BL Lacs is a consequence of a rather drastic change of the accretion mode, becoming radiatively inefficient below a critical value of the accretion rate, corresponding to a disk luminosity of ˜1 per cent of the Eddington one. The reduction of the ionizing photons below this limit implies that the broad line clouds, even if present, cannot produce significant broad lines, and the object becomes a BL Lac.

  13. THE SPECTRAL INDEX PROPERTIES OF FERMI BLAZARS

    SciTech Connect

    Fan, J. H.; Yang, J. H.; Yuan, Y. H.; Wang, J.; Gao, Y.

    2012-12-20

    In this paper, a sample of 451 blazars (193 flat spectrum radio quasars (FSRQs), 258 BL Lacertae objects) with corresponding X-ray and Fermi {gamma}-ray data is compiled to investigate the correlation both between the X-ray spectral index and the {gamma}-ray spectral index and between the spectral index and the luminosity, and to compare the spectral indexes {alpha}{sub X}, {alpha}{sub {gamma}}, {alpha}{sub X{gamma}}, and {alpha}{sub {gamma}X{gamma}} for different subclasses. We also investigated the correlation between the X-ray and the {gamma}-ray luminosity. The following results have been obtained. Our analysis indicates that an anti-correlation exists between the X-ray and the {gamma}-ray spectral indexes for the whole sample. However, when we considered the subclasses of blazars (FSRQs, the low-peaked BL Lacertae objects (LBLs) and the high-peaked BL Lacertae objects (HBLs)) separately, there is not a clear relationship for each subclass. Based on the Fermi-detected sources, we can say that the HBLs are different from FSRQs, while the LBLs are similar to FSRQs.

  14. Probes of the Inner Jets of Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.

    1996-01-01

    I review models for the 'inner jet" in blazars, the section that connects the central engine with the radio jet. I discuss how the structure and physics of the inner jet can he explored using millimeter-wave VLBI as well as multiwaveband observations of blazars. Flares at radio to gamma-ray frequencies should exhibit time delays at different wavebands that can test models for both the high-energy emission mechanisms and the nature of the inner jet in blazars.

  15. Spectacular variability of gamma-ray emission in blazar 3C279 during the large outburst in June 2015

    NASA Astrophysics Data System (ADS)

    Madejski, Grzegorz Maria; Hayashida, Masaaki; Asano, Katsuaki; Thompson, David John; Nalewajko, Krzysztof; Sikora, Marek; Fermi-LAT Team

    2016-01-01

    The Flat Spectrum Radio Quasar 3C 279 has been one of the brightest gamma-ray blazars in the sky. In Dec. 2013, April 2014, and June 2015 it showed powerful outbursts with the gamma-ray flux higher than 1x10^{-5} ph/cm^2/s (above 100 MeV). The December 2013 outburst showed an unusually hard power-law gamma-ray spectrum (index~1.7), and an asymmetric light curve profile with a few-hour time scale variability. The outburst in June 2015 was extreme, revealing a record-breaking integral flux above 100 MeV of 4x10^{-5} ph/cm^2/s, more than an order of magnitude higher than the average gamma-ray flux of the Crab. At the same time, the X-ray flux also showed the highest level of soft X-ray flux ever measured by Swift-XRT. The high flux prompted a Fermi-LAT ToO pointing observation. The increase of exposure and the very high flux state of the source allowed us to resolve the gamma-ray flux on a sub-orbital time scales. Our analysis of the LAT data revealed variability on time scales of tens of minutes. In this contribution, we will present the observational results of those outbursts from 3C279 together with multi-wavelength observations, with a focus on detailed analysis of the 2015 June outburst.

  16. Optical Observations Of Fermi LAT Monitored Blazars

    NASA Astrophysics Data System (ADS)

    Cook, Kyle; Carini, M. T.

    2009-01-01

    For the past 8 years the Bell Observatory at Western Kentucky University has been conducting R band monitoring of the variability of approximately 50 Blazars. A subset of these objects are being routinely observed with the LAT instrument on-board the Fermi Space Telescope. Adding the Robotically Controlled Telescope (RCT) at Kitt Peak National Observatory and observations with the AZT-11 telescope at the Crimean Astrophysical Observatory (CRAO), we are intensively monitoring the Blazars on the Lat monitoring list. We present the results of our long term monitoring of the LAT monitored Blazars, as well as the recent contemporaneous optical R band observations we have obtained of the LAT Blazars.

  17. The jets-accretion relation, mass-luminosity relation in Fermi blazars

    NASA Astrophysics Data System (ADS)

    Yu, Xiaoling; Zhang, Xiong; Zhang, Haojing; Xiong, Dingrong; Li, Bijun; Cha, Yongjuan; Chen, Yongyun; Huang, Xia; Wang, Yuwei

    2015-05-01

    A sample of 111 Fermi blazars each with a well-established radio core luminosity, broad-line luminosity, bolometric luminosity and black hole mass has been compiled from the literatures. We present a significant correlation between radio core and broad-line emission luminosities that supports a close link between accretion processes and relativistic jets. Analysis reveals a relationship of which is consistant with theoretical predicted coefficient and supports that blazar jets are powered by energy extraction from a rapidly spinning Kerr black hole through the magnetic field provided by the accretion disk. Through studying the correlation between the intrinsic bolometric luminosity and the black hole mass, we find a relationship of which supports mass-luminosity relation for Fermi blazars derived in this work is a powerlaw relation similar to that for main-sequence stars. Finally, EVOLUTIONARY SEQUENCE OF BLAZARS is discussed.

  18. 5-day photo-polarimetric WEBT Campaign on Blazar S5 0716+714 - a Study of Microvariabiltiy in Blazar

    NASA Astrophysics Data System (ADS)

    Bhatta, Gopal; Ostrwoski, Michal; Stawarz, Lukasz; Zola, Staszek; Jableka, Damian; Bachev, R.; Benitez, Erika; Dhalla, Sarah M.; Cason, Andy; Carosati, Daniele; Damljanovic, Goran; Frasca, A.; Hu, Shao Ming; Jorstad, Svetlana G.; Kurtanidze, O.; Larionov, Valeri; Leto, Giuseppe; Marscher, Alan P.; Moody, Joseph; Ohlert, Johhanes; Rizzi, Nicola; Sadun, Alberto C.; Sasada, Mahito; Sergeev, Sergey; Strigachev, Anton; Vince, Oliver; Webb, James Raymond; Whole Earth Blazar Telescope

    2015-01-01

    A whole earth blazar telescope (WEBT) campaign on blazar S5 0716+714 was organized to simultaneously monitor the source in multiple photo-polarimetric filters as a study of the nature of microvariability in blazar. The campaign, starting on March 2nd 2014, lasted for five consecutive days resulting in a rich data set- flux in B,V,R,I and near IR filters, and polarization degree (PD) and position angle (PA) in mainly R filter. Such a rich information provides with an unique opportunity to look deep into the localized emission regions in the jet of the blazar. During the campaign, the source remained active with 0.93 duty cycle and went through an oscillation of 0.3 magnitudes along with 5% change in PD and 50 degrees swing in PA. For 6.19 hrs the activity suddenly stopped in all the filters resulting in a plateau around 14 magnitudes in R filter light curve and then brightens by 0.14 mag in 2.96 hr time. We employed time series analysis in search of possible quasi-periodic oscillations and found some of the significant timescales present in the light curve which could reflect on the physical processes in the turbulent jet environment. In the color-magnitude analysis, we looked for 'bluer-when-brighter' trend widely claimed to be found in some of the blazars including the source. Although we found some of such incidences, they could not claimed to be persistent through out the campaign period. Similarly, no clear trend of correlation between flux and PD, and flux and PA could be established. A modeling of the mini-flares lasting few hours as stochastic synchrotron pulses on top of relative stable back ground emission and that incorporates simultaneous the change of color, PA and PD is underway.

  19. The TeV blazar Markarian 421 at the highest spatial resolution

    NASA Astrophysics Data System (ADS)

    Blasi, M. G.; Lico, R.; Giroletti, M.; Orienti, M.; Giovannini, G.; Cotton, W.; Edwards, P. G.; Fuhrmann, L.; Krichbaum, T. P.; Kovalev, Y. Y.; Jorstad, S.; Marscher, A.; Kino, M.; Paneque, D.; Perez-Torres, M. A.; Piner, B. G.; Sokolovsky, K. V.

    2013-11-01

    Context. High-resolution radio observations allow us to directly image the innermost region of active galactic nuclei. The Very Long Baseline Array (VLBA) data analyzed in this paper were obtained during a multiwavelength (MWL) campaign, carried out in 2011, from radio to very high energy gamma rays, on the TeV blazar Markarian 421 (Mrk 421). Aims: Our aim was to obtain information on the jet structure in Mrk 421 during the MWL campaign at the highest possible angular resolution and with high temporal frequency observations, in order to compare structural and flux density evolution with higher energy variations. Methods: We consider data obtained with the VLBA at 43 GHz through two sets of observations: one is part of a dedicated multi-frequency monitoring campaign, in which we observed Mrk 421 once a month from January to December 2011 at three frequencies; the other is extracted from the Boston University monitoring program, which observes 34 blazars at 43 GHz about once per month. We model-fit the data in the visibility plane, study the proper motion of jet components, the light curve, and the spectral index of the jet features. We compare the radio data with optical light curves obtained at the Steward Observatory, considering also the optical polarization information. Results: Mrk 421 has a bright nucleus and a one-sided jet extending towards the north-west for a few parsecs. The model-fits show that brightness distribution is well described using 6-7 circular Gaussian components, four of which are reliably identified at all epochs; all components are effectively stationary except for component D, at ~0.4 mas from the core, whose motion is, however, subluminal. Analysis of the light curve shows two different states, with the source being brighter and more variable in the first half of 2011 than in the second half. The highest flux density is reached in February. A comparison with the optical data reveals an increase of the V magnitude and of the fractional

  20. Reliability and uncertainty in the estimation of pKa by least squares nonlinear regression analysis of multiwavelength spectrophotometric pH titration data.

    PubMed

    Meloun, Milan; Syrový, Tomás; Bordovská, Sylva; Vrána, Ales

    2007-02-01

    When drugs are poorly soluble then, instead of the potentiometric determination of dissociation constants, pH-spectrophotometric titration can be used along with nonlinear regression of the absorbance response surface data. Generally, regression models are extremely useful for extracting the essential features from a multiwavelength set of data. Regression diagnostics represent procedures for examining the regression triplet (data, model, method) in order to check (a) the data quality for a proposed model; (b) the model quality for a given set of data; and (c) that all of the assumptions used for least squares hold. In the interactive, PC-assisted diagnosis of data, models and estimation methods, the examination of data quality involves the detection of influential points, outliers and high leverages, that cause many problems when regression fitting the absorbance response hyperplane. All graphically oriented techniques are suitable for the rapid estimation of influential points. The reliability of the dissociation constants for the acid drug silybin may be proven with goodness-of-fit tests of the multiwavelength spectrophotometric pH-titration data. The uncertainty in the measurement of the pK (a) of a weak acid obtained by the least squares nonlinear regression analysis of absorption spectra is calculated. The procedure takes into account the drift in pH measurement, the drift in spectral measurement, and all of the drifts in analytical operations, as well as the relative importance of each source of uncertainty. The most important source of uncertainty in the experimental set-up for the example is the uncertainty in the pH measurement. The influences of various sources of uncertainty on the accuracy and precision are discussed using the example of the mixed dissociation constants of silybin, obtained using the SQUAD(84) and SPECFIT/32 regression programs. PMID:17216158

  1. Contemporaneous Multiwaveband Observations of Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Bloom, Steven D.; Zhang, Yun Fei; Gear, Walter K.

    1994-01-01

    We have observed a number of blazars at wavebands ranging from radio to gamma-ray. We find bright gamma-ray emission to be associated with strong synchrotron flares observed at lower frequencies. The x-ray flux and entire radio spectrum of 4C 39.25 have each increased in strength by 30% over a 2-year period, in agreement with the prediction of the bent relativistic jet model.

  2. Constraining the particle spectrum in blazar jets: importance of the hard X-ray spectrum

    NASA Astrophysics Data System (ADS)

    Sinha, Atreyee; Sahayanathan, Sunder; Chitnis, Varsha

    2016-07-01

    Measurement of the spectral curvature in blazar jets can throw light on the underlying particle spectral distribution, and hence, the acceleration and diffusion processes at play. With the advent of NuSTAR and ASTROSAT, and the upcoming ASTRO-H, this curvature can now be measured accurately across the broadband X-ray energies. We will discuss results from our recent works on two HBLs, Mkn421 (Sinha et al, A&A 2015) and 1ES1011+496 (Sinha et al, ApJ submitted), and show how simultaneous measurement at hard and soft X-ray energies can be crucial in understanding the underlying particle spectrum. Detection of lognormality in blazars is beginning to hint at strong disk-jet connections. India's recently launched multiwavelength satellite, the ASTROSAT will provide simultaneous time resolved data between 0.2-80keV, along with measurements at Optical-UV energies. We will discuss prospects from ASTROSAT for studying jet triggering mechanisms in blazars.

  3. A Continuum Framework of the Long-Term Optical/Near-Infrared Color Variability of Blazars

    NASA Astrophysics Data System (ADS)

    Isler, Jedidah; Urry, C. Megan; Bailyn, Charles D.; Coppi, Paolo S.; Hasan, Imran; MacPherson, Emily; Buxton, Michelle

    2016-01-01

    We have undertaken a 7-year, multiwavelength program to observe a sample of blazars in various Fermi gamma-ray states, using the Small and Medium Aperture Research Telescope System (SMARTS) 1.3m + ANDICAM instrument in Cerro Tololo, Chile. We present near-daily optical and infrared (OIR) color variability diagrams of these sources and compare the OIR flux and color to the Fermi gamma-ray flux on similar cadence. We then analyze the color variability properties on short and long timescales, as compared to the length of an average gamma-ray flare, to better constrain the physical mechanisms responsible for the variability properties that we observe. By monitoring several activity states, we avoid the selection effects that previous studies have encountered when only observing blazars during flaring states. From this long-term observational data, we develop a schematic representation of the possible color variability behaviors in blazars and how it is related to the thermal disk and non-thermal jet contributions in both Flat Spectrum Radio Quasars and BL Lac objects.

  4. Multiwavelength analysis for interferometric (sub-)mm observations of protoplanetary disks. Radial constraints on the dust properties and the disk structure

    NASA Astrophysics Data System (ADS)

    Tazzari, M.; Testi, L.; Ercolano, B.; Natta, A.; Isella, A.; Chandler, C. J.; Pérez, L. M.; Andrews, S.; Wilner, D. J.; Ricci, L.; Henning, T.; Linz, H.; Kwon, W.; Corder, S. A.; Dullemond, C. P.; Carpenter, J. M.; Sargent, A. I.; Mundy, L.; Storm, S.; Calvet, N.; Greaves, J. A.; Lazio, J.; Deller, A. T.

    2016-04-01

    Context. The growth of dust grains from sub-μm to mm and cm sizes is the first step towards the formation of planetesimals. Theoretical models of grain growth predict that dust properties change as a function of disk radius, mass, age, and other physical conditions. High angular resolution observations at several (sub-)mm wavelengths constitute the ideal tool with which to directly probe the bulk of dust grains and to investigate the radial distribution of their properties. Aims: We lay down the methodology for a multiwavelength analysis of (sub-)mm and cm continuum interferometric observations to self-consistently constrain the disk structure and the radial variation of the dust properties. The computational architecture is massively parallel and highly modular. Methods: The analysis is based on the simultaneous fit in the uv-plane of observations at several wavelengths with a model for the disk thermal emission and for the dust opacity. The observed flux density at the different wavelengths is fitted by posing constraints on the disk structure and on the radial variation of the grain size distribution. Results: We apply the analysis to observations of three protoplanetary disks (AS 209, FT Tau, DR Tau) for which a combination of spatially resolved observations in the range ~0.88 mm to ~10 mm is available from SMA, CARMA, and VLA. In these disks we find evidence of a decrease in the maximum dust grain size, amax, with radius. We derive large amax values up to 1 cm in the inner disk 15 AU ≤ R ≤ 30 AU and smaller grains with amax ~ 1 mm in the outer disk (R ≳ 80 AU). Our analysis of the AS 209 protoplanetary disk confirms previous literature results showing amax decreasing with radius. Conclusions: Theoretical studies of planetary formation through grain growth are plagued by the lack of direct information on the radial distribution of the dust grain size. In this paper we develop a multiwavelength analysis that will allow this missing quantity to be

  5. Correlation between -ray flux density and redshift for Fermi blazars

    NASA Astrophysics Data System (ADS)

    Xiao, Hu-Bing; Pei, Zhi-Yuan; Xie, Hong-Jing; Hao, Jing-Meng; Yang, Jiang-He; Yuan, Yu-Hai; Liu, Yi; Fan, Jun-Hui

    2015-09-01

    Blazars are strong -ray emitters, the -ray emissions are likely strongly beamed, therefore, one should use the intrinsic (de-beamed) emissions to investigate its emission nature. In this work, we compiled a sample of Fermi blazars with available beaming Doppler factors, , to investigate the correlation between -ray flux density, , and redshift, . The analysis shows that there is no correlation between and for the observed -ray flux density, but there is a clear strong correlation between the intrinsic flux densities, and . We also discussed the relationship of -ray luminosity and short time scale for the observed data and the intrinsic data. Our analysis suggests that the intrinsic -ray flux density obeys the flux density and redshift relation, and the jet in -rays maybe a continuous case. The intrinsic luminosity and the short time scales obey the Elliot and Shapiro relation and Abramowicz and Nobili relation as well.

  6. Multiwavelength observations of Mrk 501 in 2008

    SciTech Connect

    Aleksic, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Gonzalez, Becerra; Bednarek, W.; Zitzer, B.

    2015-01-01

    Context. Blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 GeV, hereafter VHE). Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. However, most of the γ-ray studies performed on Mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available γ-ray instrumentation was easier toperform. Aims. Our goal is to characterize the source γ-ray emission in detail, together with the radio-to-X-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity. Methods. We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE γ-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. This provided extensive energy and temporal coverage of Mrk 501 throughout the entire campaign. Results. Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%–20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the X-ray and VHE fluxes. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density. Conclusions. The one-zone SSC model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the MW campaign. This agrees with

  7. High Energy Polarization of Blazars: Detection Prospects

    NASA Astrophysics Data System (ADS)

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  8. HIGH ENERGY POLARIZATION OF BLAZARS: DETECTION PROSPECTS

    SciTech Connect

    Chakraborty, N.; Pavlidou, V.; Fields, B. D.

    2015-01-01

    Emission from blazar jets in the ultraviolet, optical, and infrared is polarized. If these low-energy photons were inverse-Compton scattered, the upscattered high-energy photons retain a fraction of the polarization. Current and future X-ray and gamma-ray polarimeters such as INTEGRAL-SPI, PoGOLITE, X-Calibur, Gamma-Ray Burst Polarimeter, GEMS-like missions, ASTRO-H, and POLARIX have the potential to discover polarized X-rays and gamma-rays from blazar jets for the first time. Detection of such polarization will open a qualitatively new window into high-energy blazar emission; actual measurements of polarization degree and angle will quantitatively test theories of jet emission mechanisms. We examine the detection prospects of blazars by these polarimetry missions using examples of 3C 279, PKS 1510-089, and 3C 454.3, bright sources with relatively high degrees of low-energy polarization. We conclude that while balloon polarimeters will be challenged to detect blazars within reasonable observational times (with X-Calibur offering the most promising prospects), space-based missions should detect the brightest blazars for polarization fractions down to a few percent. Typical flaring activity of blazars could boost the overall number of polarimetric detections by nearly a factor of five to six purely accounting for flux increase of the brightest of the comprehensive, all-sky, Fermi-LAT blazar distribution. The instantaneous increase in the number of detections is approximately a factor of two, assuming a duty cycle of 20% for every source. The detectability of particular blazars may be reduced if variations in the flux and polarization fraction are anticorrelated. Simultaneous use of variability and polarization trends could guide the selection of blazars for high-energy polarimetric observations.

  9. Multi-wavelength holographic profilometry

    NASA Astrophysics Data System (ADS)

    Barbosa, E. A.; Gesualdi, M. R.; Muramatsu, M.

    2006-01-01

    A novel method for surface profilometry by holography is presented. We used a diode laser emitting at many wavelengths simultaneously as the light source and a Bi 12TiO 20 (BTO) crystal as the holographic medium in single exposure processes. The employ of multi-wavelength, large free spectral range (FSR) lasers leads to holographic images covered of interference fringes corresponding to the contour lines of the studied surface. In order to obtain the relief of the studied surface, the fringe analysis was performed by the phase stepping technique (PST) and the phase unwrapping was carried out by the Cellular-automata method. We analysed the relief of a tilted flat metallic bar and a tooth prosthesis.

  10. Testing the blazar sequence with the least luminous BL Lacertae objects

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Capetti, A.

    2016-03-01

    In a previous paper, we proposed a new method to select low-power BL Lacs (LPBLs) based on mid-infrared emission and flux contrast through the Ca II spectral break; that study led to the selection of a complete sample formed by 34 LPBLs with 0.05 analysis of the median LPBL SED confirms disagreement with the blazar sequence at low radio luminosities. Furthermore, if we limit the sample to the LBLs subsample, we find that their median SED shape is essentially indistinguishable from that of the most luminous BL Lacs. We conclude that the observed radio power is not the main driving parameter of the multiwavelength properties of BL Lacs.

  11. Simultaneous Radio to (Sub-) Mm-Monitoring of Variability and Spectral Shape Evolution of Potential GLAST Blazars

    SciTech Connect

    Fuhrmann, L.; Zensus, J.A.; Krichbaum, T.P.; Angelakis, E.; Readhead, A.C.S.; /Caltech

    2011-11-29

    The Large Area Telescope (LAT) instrument onboard GLAST offers a tremendous opportunity for future blazar studies. In order to fully benefit from its capabilities and to maximize the scientific return from the LAT, it is of great importance to conduct dedicated multi-frequency monitoring campaigns that will result comprehensive observations. Consequently, we initiated an effort to conduct a GLAST-dedicated, quasi-simultaneous, broad-band flux-density (and polarization) monitoring of potential GLAST blazars with the Effelsberg and OVRO radio telescopes (11 cm to 7mm wavelength). Here, we present a short overview of these activities which will complement the multi-wavelengths activities of the GLAST/LAT collaboration towards the 'low-energy' radio bands. Further we will give a brief outlook including the extension of this coordinated campaign towards higher frequencies and future scientific aims.

  12. Properties of Blazar Jets Defined by an Economy of Power

    NASA Astrophysics Data System (ADS)

    Petropoulou, Maria; Dermer, Charles D.

    2016-07-01

    The absolute power of a relativistic black hole jet includes the power in the magnetic field, the leptons, the hadrons, and the radiated photons. A power analysis of a relativistic radio/γ-ray blazar jet leads to bifurcated leptonic synchrotron-Compton (LSC) and leptohadronic synchrotron (LHS) solutions that minimize the total jet power. Higher Doppler factors with increasing peak synchrotron frequency are implied in the LSC model. Strong magnetic fields {B}\\prime ≳ 100 {{G}} are found for the LHS model with variability times ≲ {10}3 {{s}}, in accord with highly magnetized, reconnection-driven jet models. Proton synchrotron models of ≳ 100 {GeV} blazar radiation can have sub-Eddington absolute jet powers, but models of dominant GeV radiation in flat spectrum radio quasars require excessive power.

  13. The Colorado IUE active galaxy survey. I - Blazars

    NASA Technical Reports Server (NTRS)

    Edelson, Rick; Pike, Gregory F.; Saken, Jon M.; Kinney, Anne; Shull, J. M.

    1992-01-01

    This paper presents consistently reduced UV continuum flux densities amd spectra indices derived from all 499 usable archived IUE observations of blazars made through mid-1991. The extraction of 1D spectra and the measurement of spectral parameters are discussed. A detailed error analysis is presented, including a discussion of the difference in the calibration between the IUE long- and short-wavelength cameras. The resulting data are presented in tabular and graphical form and are available by electronic mail as well. These results will be most useful for variability studies, but can also be used to characterize the broad-band energy distributions and to compare blazar properties with those of other AGN. This is the first in a series of papers, in which extracted spectral parameters will be published for the over 4500 spectra of AGN in the IUE archives.

  14. STACEE observations of Markarian 421 above 100 GeV and a new method for high-energy spectral analysis

    NASA Astrophysics Data System (ADS)

    Carson, Jennifer Elaine

    Markarian 421 is a nearby (z =0.03) blazar that is actively studied to constrain both physical blazar models and models of the extragalactic background light. The Solar Tower Atmospheric Cherenkov Effect Experiment (STACEE), a wavefront- sampling detector sensitive to ~ 100 GeV gamma rays, detected Mkn 421 during a multiwavelength campaign in early 2004. This thesis covers the 2004 STACEE observations of Mkn 421 and their analysis. The goal of the project was to measure the gamma-ray spectrum of Mkn 421; such a spectral result would be STACEE's first and one of the first from any detector in STACEE's energy range. Achieving this goal required the development of a new method for reconstructing gamma-ray energies from the STACEE data. The reconstruction method is described in detail, and the resulting spectrum is presented. Finally, the implications of the results for understanding high-energy emission mechanisms in AGN are discussed.

  15. Analysis of air-mass modification over Poland and Romania by means of multiwavelength lidars - a case study 19-21/07/2014

    NASA Astrophysics Data System (ADS)

    Costa-Surós, Montserrat; Stachlewska, Iwona S.; Nicolae, Doina; Nemuc, Anca; Janicka, Lucja; Markowicz, Krzysztof M.; Belegante, Livio; Talianu, Camelia; Heese, Birgit; Engelmann, Ronny

    2015-04-01

    A case study of air-mass modification over Poland and Romania, assessing the role of the Carpathian Mountains, during 19-21/07/2014 is analyzed. The study is based mainly on measurements taken by two multiwavelength Raman lidars at two different sites: the Radiative Transfer Laboratory (RT-Lab) at the Faculty of Physics of the University of Warsaw in Warsaw (Poland) and at the RADO site of the National Institute of R&D in Optoelectronics in Magurele (Romania). These data were complemented with meteorological data collected at two other sites: SolarAOT in Strzyżów (Poland) - equipped also with AERONET photometer and CHM15k ceilometer, and in Cluj (Romania). The RADO site, with its 7-wavelength aerosol-Raman-depolarization lidar (RALi) is integrated into EARLINET network. The RT-Lab site, with its 8-wavelength aerosol-Raman-depolarization (PollyXT-type) lidar, started the procedure to join in EARLINET last year. Moreover, RT-Lab and SolarAOT sites are part of the Poland AOD network. The analysis is focused on evaluating both multi-wavelength lidar data sets in order to search for similarities and differences in the vertical profiles describing the atmospheric layers above the two stations. Accordingly to GDAS Hysplit 4-days backward trajectory ending up in Magurele at 0.5, 1.5 and 3 km an air-mass from western Europe entered Poland from the north-west on 19/07/2014, descended on the following day over the Poland AOD station in Strzyżów, followed by Cluj and end up at Magurele on 21/07/2014. As the four stations are located along a north-west to south-east line the objective was to evaluate the aerosol properties of the air flow transported over Poland and further to Romania. At both sites, backscatter profiles at 355, 532 and 1064nm, extinction profiles at 355 and 532nm, and depolarization profiles at 532nm and 355nm, show distinctly layered structure in the atmosphere. Along with these we used data from stations in Strzyżów and Cluj as well as information

  16. Multifrequency Catalogue of Blazars - 5th Edition

    NASA Astrophysics Data System (ADS)

    Massaro, E.; Maselli, A.; Leto, C.; Marchegiani, P.; Perri, M.; Giommi, P.; Piranomonte, S.

    2014-12-01

    The 5th Edition of the Multifrequency Catalogue of Blazars is one of the most complete lists of Active Galactic Nuclei whose emission properties are recognised as typical of blazars. It includes the list of sources and an essential compilation of multifrequency data from radio to gamma rays. The source list for the entire sky is also available online at the ASDC web site (http://www.asdc.asi.it/bzcat/) where it is frequently updated to add new blazars and to improve the database.

  17. Probes of the inner jets of blazars.

    PubMed Central

    Marscher, A P

    1995-01-01

    I review models for the "inner jet" in blazars, the section that connects the central engine with the radio jet. I discuss how the structure and physics of the inner jet can be explored using millimeter-wave VLBI (very-long-baseline radio interferometry) as well as multiwaveband observations of blazars. Flares at radio to gamma-ray frequencies should exhibit time delays at different wavebands that can test models for both the high-energy emission mechanisms and the nature of the inner jet in blazars. PMID:11607614

  18. High spatial resolution VAULT H-Lyα observations and multiwavelength analysis of an active region filament

    NASA Astrophysics Data System (ADS)

    Vial, J.-C.; Olivier, K.; Philippon, A. A.; Vourlidas, A.; Yurchyshyn, V.

    2012-05-01

    Context. The search for the fine structure of prominences has received considerable new attention thanks to the Swedish Solar Telescope (SST) Hα pictures that provide an unsurpassed spatial resolution. Recently, it has been shown that the filaments' coronal environment, at least for quiescent filaments, is perturbed by either cool absorbing material (in the EUV) or an "emissivity blocking" (actually a lack of transition region and coronal material). Aims: The aim is to assess the fine structure in an active region filament and to determine the nature of the EUV absorption or lack of emission phenomena, using the very optically thick line H-Lyα, formed at a temperature higher than Hα. Methods: We performed a multiwavelength study where high-resolution imaging in the H-Lyα line (VAULT) was analysed and compared with observations of an active region filament in Hα (BBSO) and EUV lines (EIT and TRACE). Results: As for the SST data, small-scale structures were detected at a typical scale of about one to two arcseconds with, for some cuts, an indication of fine scales down to 0.4 arcsec in the optically thick H-Lyα line. The filament intensity relative to the intensity of the (active) region it is embedded in is about 0.2 in H-Lyα. This ratio (Lymanα ratio intensity or "LRI") is the lowest value compared to other lines, e.g. Hα. The filament environment was also investigated and evidence of an UV extension was found. The comparison of spatial cuts in different lines across the filament shows evidence of strong absorption, and consequently of cool plasma on one side of the filament, but not on the other (that side is obscured by the filament itself). Conclusions: The absence of very fine structure in H-Lyα compared to Hα is explained by the formation temperature of the H-Lyα line (~20 000 K), where the transition regions of the thin threads begin to merge. From the detection of H-Lyα absorption on the observable side of the filament side, we derive the

  19. Dynamic range multiwavelength particle characterization using analytical ultracentrifugation.

    PubMed

    Walter, Johannes; Peukert, Wolfgang

    2016-04-14

    We demonstrate how a sophisticated data analysis methodology enables us to perform multiwavelength evaluations of dynamic rotor speed gradient experiments obtained by analytical ultracentrifugation equipped with a multiwavelength detector. Our data evaluation tool HDR-MULTIFIT allows for the accurate analysis of sedimentation coefficient distributions which can be converted to particle size distributions. By means of multiwavelength evaluation, species dependent extinction spectra can be determined even for complex mixtures. Moreover, optical and hydrodynamic properties can be correlated for spherical particles of known optical properties applying multiwavelength evaluation and Mie's theory leading to a significant increase in the dynamic range of the experiment. We provide the theoretical background about the operation principle of our methodology and compare the performance of the multiwavelength analysis to the conventional single wavelength analysis as it is applied in turbidity analysis. We validate our technique using NIST traceable reference particles and show that our technique is universally applicable to materials of known and unknown optical properties, thus clearly extending the possibilities of particle analysis. PMID:26837517

  20. Dynamic range multiwavelength particle characterization using analytical ultracentrifugation

    NASA Astrophysics Data System (ADS)

    Walter, Johannes; Peukert, Wolfgang

    2016-03-01

    We demonstrate how a sophisticated data analysis methodology enables us to perform multiwavelength evaluations of dynamic rotor speed gradient experiments obtained by analytical ultracentrifugation equipped with a multiwavelength detector. Our data evaluation tool HDR-MULTIFIT allows for the accurate analysis of sedimentation coefficient distributions which can be converted to particle size distributions. By means of multiwavelength evaluation, species dependent extinction spectra can be determined even for complex mixtures. Moreover, optical and hydrodynamic properties can be correlated for spherical particles of known optical properties applying multiwavelength evaluation and Mie's theory leading to a significant increase in the dynamic range of the experiment. We provide the theoretical background about the operation principle of our methodology and compare the performance of the multiwavelength analysis to the conventional single wavelength analysis as it is applied in turbidity analysis. We validate our technique using NIST traceable reference particles and show that our technique is universally applicable to materials of known and unknown optical properties, thus clearly extending the possibilities of particle analysis.

  1. Pair Cascades in Blazars and Radio Galaxies

    NASA Astrophysics Data System (ADS)

    Roustazadeh Sheikhyousefi, Parisa

    2012-05-01

    variability of several blazars. Analysis of the variability time scales of the light curve con

  2. A Coordinated X-Ray and Optical Campaign of the Nearest Massive Eclipsing Binary, δ Orionis Aa. IV. A Multiwavelength, Non-LTE Spectroscopic Analysis

    NASA Astrophysics Data System (ADS)

    Shenar, T.; Oskinova, L.; Hamann, W.-R.; Corcoran, M. F.; Moffat, A. F. J.; Pablo, H.; Richardson, N. D.; Waldron, W. L.; Huenemoerder, D. P.; Maíz Apellániz, J.; Nichols, J. S.; Todt, H.; Nazé, Y.; Hoffman, J. L.; Pollock, A. M. T.; Negueruela, I.

    2015-08-01

    Eclipsing systems of massive stars allow one to explore the properties of their components in great detail. We perform a multi-wavelength, non-LTE analysis of the three components of the massive multiple system δ Ori A, focusing on the fundamental stellar properties, stellar winds, and X-ray characteristics of the system. The primary’s distance-independent parameters turn out to be characteristic for its spectral type (O9.5 II), but usage of the Hipparcos parallax yields surprisingly low values for the mass, radius, and luminosity. Consistent values follow only if δ Ori lies at about twice the Hipparcos distance, in the vicinity of the σ-Orionis cluster. The primary and tertiary dominate the spectrum and leave the secondary only marginally detectable. We estimate the V-band magnitude difference between primary and secondary to be {{Δ }}V≈ 2\\buildrel{{m}}\\over{.} 8. The inferred parameters suggest that the secondary is an early B-type dwarf (≈B1 V), while the tertiary is an early B-type subgiant (≈B0 IV). We find evidence for rapid turbulent velocities (∼200 km s‑1) and wind inhomogeneities, partially optically thick, in the primary’s wind. The bulk of the X-ray emission likely emerges from the primary’s stellar wind ({log}{L}{{X}}/{L}{Bol}≈ -6.85), initiating close to the stellar surface at {R}0∼ 1.1 {R}*. Accounting for clumping, the mass-loss rate of the primary is found to be {log}\\dot{M}≈ -6.4 ({M}ȯ {{yr}}-1), which agrees with hydrodynamic predictions, and provides a consistent picture along the X-ray, UV, optical, and radio spectral domains.

  3. UV-TO-FIR ANALYSIS OF SPITZER/IRAC SOURCES IN THE EXTENDED GROTH STRIP. I. MULTI-WAVELENGTH PHOTOMETRY AND SPECTRAL ENERGY DISTRIBUTIONS

    SciTech Connect

    Barro, Guillermo; Perez-Gonzalez, P. G.; Gallego, J.; Villar, V.; Zamorano, J.; Ashby, M. L. N.; Kajisawa, M.; Yamada, T.; Miyazaki, S.

    2011-03-15

    We present an IRAC 3.6+4.5 {mu}m selected catalog in the Extended Groth Strip (EGS) containing photometry from the ultraviolet to the far-infrared and stellar parameters derived from the analysis of the multi-wavelength data. In this paper, we describe the method used to build coherent spectral energy distributions (SEDs) for all the sources. In a forthcoming companion paper, we analyze those SEDs to obtain robust estimations of stellar parameters such as photometric redshifts, stellar masses, and star formation rates. The catalog comprises 76,936 sources with [3.6] {<=} 23.75 mag (85% completeness level of the IRAC survey in the EGS) over 0.48 deg{sup 2}. For approximately 16% of this sample, we are able to deconvolve the IRAC data to obtain robust fluxes for the multiple counterparts found in ground-based optical images. Typically, the SEDs of the IRAC sources in our catalog count with more than 15 photometric data points, spanning from the ultraviolet wavelengths probed by GALEX to the far-infrared observed by Spitzer, and going through ground- and space-based optical and near-infrared data taken with 2-8 m class telescopes. Approximately 95% and 90% of all IRAC sources are detected in the deepest optical and near-infrared bands. These fractions are reduced to 85% and 70% for S/N > 5 detections in each band. Only 10% of the sources in the catalog have optical spectroscopy and redshift estimations. Almost 20% and 2% of the sources are detected by MIPS at 24 and 70 {mu}m, respectively. We also cross-correlate our catalog with public X-ray and radio catalogs. Finally, we present the Rainbow Navigator public Web interface utility, designed to browse all the data products resulting from this work, including images, spectra, photometry, and stellar parameters.

  4. Fermi large area telescope observations of blazar 3C 279 occultations by the sun

    SciTech Connect

    Barbiellini, G.; Bastieri, D.; Buson, S.; Bechtol, K.; Blandford, R. D.; Borgland, A. W.; Buehler, R.; Cameron, R. A.; Chiang, J.; Bellazzini, R.; Bregeon, J.; Bruel, P.; Caraveo, P. A.; Cavazzuti, E.; Ciprini, S.; Cecchi, C.; Chaves, R. C. G.; Cheung, C. C. E-mail: phdmitry@stanford.edu; and others

    2014-04-01

    Observations of occultations of bright γ-ray sources by the Sun may reveal predicted pair halos around blazars and/or new physics, such as, e.g., hypothetical light dark matter particles—axions. We use Fermi Gamma-Ray Space Telescope (Fermi) data to analyze four occultations of blazar 3C 279 by the Sun on October 8 each year from 2008 to 2011. A combined analysis of the observations of these occultations allows a point-like source at the position of 3C 279 to be detected with significance of ≈3σ, but does not reveal any significant excess over the flux expected from the quiescent Sun. The likelihood ratio test rules out complete transparency of the Sun to the blazar γ-ray emission at a 3σ confidence level.

  5. GAMMA-RAY OBSERVATIONAL PROPERTIES OF TeV-DETECTED BLAZARS

    SciTech Connect

    Sentuerk, G. D.; Errando, M.; Mukherjee, R.; Boettcher, M.

    2013-02-20

    The synergy between the Fermi-LAT and ground-based Cherenkov telescope arrays gives us the opportunity for the first time to characterize the high-energy emission from blazars over 5 decades in energy, from 100 MeV to 10 TeV. In this study, we perform a Fermi-LAT spectral analysis for TeV-detected blazars and combine it with archival TeV data. We examine the observational properties in the {gamma}-ray band of our sample of TeV-detected blazars and compare the results with X-ray and GeV-selected populations. The spectral energy distributions (SEDs) that result from combining Fermi-LAT and ground-based spectra are studied in detail. Simple parameterizations such as a power-law function do not always reproduce the high-energy SEDs, where spectral features that could indicate intrinsic absorption are observed.

  6. Multi-frequency, multi-messenger astrophysics with Swift. The case of blazars

    NASA Astrophysics Data System (ADS)

    Giommi, Paolo

    2015-09-01

    During its first 10 years of orbital operations Swift dedicated approximately 11% of its observing time to blazars, carrying out more than 12,000 observations of ∼1600 different objects, for a total exposure time of over 25 million seconds. In this paper I briefly discuss the impact that Swift is having on blazar multi-frequency and time-domain astrophysics, as well as how it is contributing to the opening of the era of multi-messenger astronomy. Finally, I present some preliminary results from a systematic analysis of a very large number of Swift XRT observations of blazars. All the "science ready" data products that are being generated by this project will be publicly released. Specifically, deconvolved X-ray spectra and best fit spectral parameters will be available through the ASDC "SED builder" tool ("https://tools.asdc.asi.it/SED")

  7. Radio core dominance of Fermi blazars

    NASA Astrophysics Data System (ADS)

    Pei, Zhi-Yuan; Fan, Jun-Hui; Liu, Yi; Yuan, Yi-Hai; Cai, Wei; Xiao, Hu-Bing; Lin, Chao; Yang, Jiang-He

    2016-07-01

    During the first 4 years of mission, Fermi/LAT detected 1444 blazars (3FGL) (Ackermann et al. in Astrophys. J. 810:14, 2015). Fermi/LAT observations of blazars indicate that Fermi blazars are luminous and strongly variable with variability time scales, for some cases, as short as hours. Those observations suggest a strong beaming effect in Fermi/LAT blazars. In the present work, we will investigate the beaming effect in Fermi/LAT blazars using a core-dominance parameter, R = S_{core}/ S_{ext.}, where S_{core} is the core emission, while S_{ext.} is the extended emission. We compiled 1335 blazars with available core-dominance parameter, out of which 169 blazars have γ-ray emission (from 3FGL). We compared the core-dominance parameters, log R, between the 169 Fermi-detected blazars (FDBs) and the rest non-Fermi-detected blazars (non-FDBs), and we found that the averaged values are < log Rrangle = 0.99±0.87 for FDBs and < log Rrangle = -0.62±1.15 for the non-FDBs. A K-S test shows that the probability for the two distributions of FDBs and non-FDBs to come from the same parent distribution is near zero (P =9.12×10^{-52}). Secondly, we also investigated the variability index (V.I.) in the γ-ray band for FDBs, and we found V.I.=(0.12 ±0.07) log R+(2.25±0.10), suggesting that a source with larger log R has larger V.I. value. Thirdly, we compared the mean values of radio spectral index for FDBs and non-FDBs, and we obtained < α_{radio}rangle =0.06±0.35 for FDBs and < α_{radio}rangle =0.57±0.46 for non-FDBs. If γ-rays are composed of two components like radio emission (core and extended components), then we can expect a correlation between log R and the γ-ray spectral index. When we used the radio core-dominance parameter, log R, to investigate the relationship, we found that the spectral index for the core component is α_{γ}|_{core} = 1.11 (a photon spectral index of α_{γ}^{ph}|_{core} = 2.11) and that for the extended component is α_{γ}|_{ext.} = 0

  8. Pushing the Limits: High Redshift Fermi-LAT Blazars

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh; Gasparrini, Dario; Lott, Benoit; Cutini, Sara; Fermi-LAT Collaboration

    2016-01-01

    High-redshift blazars detected by the Fermi Large Area Telescope (LAT) are of great astrophysical import as they are extreme objects whose energetics remain a mystery. Such blazars are intrinsically interesting since they inform us about the evolution of gamma-ray blazars and are, by definition, some of the more luminous blazars in the LAT sample. They are also an excellent tool to study the EBL and thus the gamma-ray horizon. We present the latest high redshift blazar detections in the LAT and discuss some of their implications.

  9. Multiwavelength observations of Mrk 501 in 2008

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadamek, A.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nowak, N.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Preziuso, S.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Rügamer, S.; Saggion, A.; Saito, T.; Saito, K.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Behera, B.; Beilicke, M.; Benbow, W.; Berger, K.; Bird, R.; Bouvier, A.; Bugaev, B.; Cerruti, M.; Chen, X.; Ciupik, L.; Collins-Hughes, E.; Cui, W.; Duke, C.; Dumm, J.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fortson, L.; Furniss, A.; Galante, N.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Johnson, C. A.; Kaaret, P.; Kertzman, M.; Kieda, D.; Krawczynski, H.; Lang, M. J.; Madhavan, A. S.; Maier, G.; Majumdar, P.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Pichel, A.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Rajotte, J.; Ratliff, G.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Sembroski, G. H.; Shahinyan, K.; Sheidaei, F.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Theiling, M.; Tyler, J.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Weekes, T. C.; Welsing, R.; Williams, D. A.; Zajczyk, A.; Zitzer, B.; VERITAS Collaboration; Villata, M.; Raiteri, C. M.; Ajello, M.; Perri, M.; Aller, H. D.; Aller, M. F.; Larionov, V. M.; Efimova, N. V.; Konstantinova, T. S.; Kopatskaya, E. N.; Chen, W. P.; Koptelova, E.; Hsiao, H. Y.; Kurtanidze, O. M.; Nikolashvili, M. G.; Kimeridze, G. N.; Jordan, B.; Leto, P.; Buemi, C. S.; Trigilio, C.; Umana, G.; Lähteenmäki, A.; Nieppola, E.; Tornikoski, M.; Sainio, J.; Kadenius, V.; Giroletti, M.; Cesarini, A.; Fuhrmann, L.; Kovalev, Yu. A.; Kovalev, Y. Y.

    2015-01-01

    Context. Blazars are variable sources on various timescales over a broad energy range spanning from radio to very high energy (>100 GeV, hereafter VHE). Mrk 501 is one of the brightest blazars at TeV energies and has been extensively studied since its first VHE detection in 1996. However, most of the γ-ray studies performed on Mrk 501 during the past years relate to flaring activity, when the source detection and characterization with the available γ-ray instrumentation was easier toperform. Aims: Our goal is to characterize the source γ-ray emission in detail, together with the radio-to-X-ray emission, during the non-flaring (low) activity, which is less often studied than the occasional flaring (high) activity. Methods: We organized a multiwavelength (MW) campaign on Mrk 501 between March and May 2008. This multi-instrument effort included the most sensitive VHE γ-ray instruments in the northern hemisphere, namely the imaging atmospheric Cherenkov telescopes MAGIC and VERITAS, as well as Swift, RXTE, the F-GAMMA, GASP-WEBT, and other collaborations and instruments. This provided extensive energy and temporal coverage of Mrk 501 throughout the entire campaign. Results: Mrk 501 was found to be in a low state of activity during the campaign, with a VHE flux in the range of 10%-20% of the Crab nebula flux. Nevertheless, significant flux variations were detected with various instruments, with a trend of increasing variability with energy and a tentative correlation between the X-ray and VHE fluxes. The broadband spectral energy distribution during the two different emission states of the campaign can be adequately described within the homogeneous one-zone synchrotron self-Compton model, with the (slightly) higher state described by an increase in the electron number density. Conclusions: The one-zone SSC model can adequately describe the broadband spectral energy distribution of the source during the two months covered by the MW campaign. This agrees with previous

  10. The Multiwavelength Milky Way Project

    NASA Astrophysics Data System (ADS)

    Brown, B. A.; Leisawitz, D.; Boyd, P. T.; Digel, S. W.; Friedlander, J.; Kessel, R. L.; Smale, A. P.

    2000-12-01

    We describe an ongoing effort to communicate what is known about the Milky Way, and how our understanding of the Galaxy has advanced in recent decades with observations across the electromagnetic spectrum. Our aim is to help students, educators, and the general public understand the structure of the Milky Way, and our location within it. Inspired by the warm reception to our Multiwavelength Milky Way poster (26,000 copies distributed; requested by people in over 50 countries) we created several related products and a new version of the poster. The updated poster contains ten Galactic plane maps and a legend that points out prominent features and objects. The Multiwavelength Milky Way web site at http://adc.gsfc.nasa.gov/mw provides an image browsing capability, links to data files and journal articles, lesson plans and suggested activities for teachers, and a poster order form. We created a slide set comprised of multiwavelength all-sky maps and a ``Multiwavelength Milky Way'' image corresponding to the poster. The Galactic plane maps featured on the poster raise questions in the minds of many non-astronomers: ``Where are we in this picture?'' and ``How do we know what we know?'' To help answer these questions we developed a realistic three-dimensional model of the Milky Way and used state-of-the-art animation techniques to create a 28-minute video called The Milky Way's Invisible Light. The viewer is taken on a tour of the Galaxy that ends at the Sun's location, from which the 3-D model is shown to resemble the Galactic plane surveys depicted on the Multiwavelength Milky Way poster. The video can be ordered on the web at http://space.gsfc.nasa.gov/astro/education/mw_film or from the ASP catalog. The Multiwavelength Milky Way project is sponsored by the Astrophysics Data Facility at NASA's Goddard Space Flight Center.

  11. Brown carbon and thermal-optical analysis: A correction based on optical multi-wavelength apportionment of atmospheric aerosols

    NASA Astrophysics Data System (ADS)

    Massabò, D.; Caponi, L.; Bove, M. C.; Prati, P.

    2016-01-01

    Thermo-optical analysis is widely adopted for the quantitative determination of total, TC, organic, OC and elemental, EC, Carbon in aerosol samples collected on quartz fibre filters. Nevertheless, the methodology presents several issues in particular about the artefacts related to the formation of pyrolytic carbon. It is usually neglected the uncertainty due to the possible presence of brown carbon (BrC) in the sample under analysis, i.e. the optically active fraction of OC produced by biomass burning and with characteristics intermediate between OC and EC. We introduce here a novel correction to the standard thermo-optical protocol based on the determination of the fraction of the sample absorbance due to the (possible) presence of BrC. This is achievable thanks to the coupled use of the Multi Wavelength Absorbance Analyser (MWAA) of the University of Genoa and a standard Sunset Inc. EC/OC analyser. Our correction provides a firmer OC/EC separation as well as an operative quantification of the BrC mass. The methodology has been validated against independent determination of the levoglucosan content in the same filters sent to the Sunset analysis. Corrections up to 23% in the OC and EC values, determined via the standard and new thermo-optical analysis, have been found in a set of PM10 (i.e. Particulate Matter with aerodynamic diameter less than 10 μm) samples collected wintertime at a mountain site in Northern Italy.

  12. Simultaneous Multiwavelength Observations of PKS 2155-304

    NASA Astrophysics Data System (ADS)

    Osterman, M. A.; Miller, H. R.; Marshall, K.; Ryle, W. T.; Aller, H.; Aller, M.; Wagner, S.

    2005-12-01

    The TeV blazar PKS 2155-304 was the subject of an intensive two week optical and infrared observing campaign in August 2004 at the CTIO 0.9m telescope. During this time, simultaneous X-ray data from RXTE was also obtained. Over the course of these observations, two large flares occurred at these wavelengths. In the weeks following the CTIO campaign, more flux increases were observed at X-ray, optical, and radio wavelengths. We present an analysis of the relative sizes, shapes, and time delays of the various flares in order to constrain various models for blazar physics (e.g. shock in jet, accelerating or decelerating jet) assuming a synchrotron self-Compton model for the production of X-ray and higher energy emission. MAO, HRM, KM, and WTR are supported in part by the Program for Extragalactic Astronomy's Research Program Enhancement funds from GSU.

  13. Plasma properties from the multi-wavelength analysis of the November 1st 2003 CME/shock event

    PubMed Central

    Benna, Carlo; Mancuso, Salvatore; Giordano, Silvio; Gioannini, Lorenzo

    2012-01-01

    The analysis of the spectral properties and dynamic evolution of a CME/shock event observed on November 1st 2003 in white-light by the LASCO coronagraph and in the ultraviolet by the UVCS instrument operating aboard SOHO, has been performed to compute the properties of some important plasma parameters in the middle corona below about 2R⊙. Simultaneous observations obtained with the MLSO/Mk4 white-light coronagraph, providing both the early evolution of the CME expansion in the corona and the pre-shock electron density profile along the CME front, were also used to study this event. By combining the above information with the analysis of the metric type II radio emission detected by ground-based radio spectrographs, we finally derive estimates of the values of the local Alfvén speed and magnetic field strength in the solar corona. PMID:25685432

  14. Monitoring Ly-Alpha Emission From the Blazar 3C 279

    NASA Technical Reports Server (NTRS)

    Koratkar, Anuradha; Pian, Elena; Urry, C. Megan; Pesce, Joseph E.

    1998-01-01

    The blazar 3C 279 is well studied and shows frequent large continuum flares from radio to gamma-ray wavelengths. There have been a number of multiwavelength observations of 3C 279, and hence there are extensive ultraviolet data for this object available in the UV archives. In this paper we present Ly-alpha emission line measurements for 3C 279 using all the archival IUE SWP spectra from 1988 to 1996 and all archival Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) G190H spectra from 1992 to 1996. Individual archival IUE spectra of 3C 279 show weak Ly-alpha emission at approximately 1868 A (z = 0.536), which is easily seen in the co-added data. The Ly-alpha emission is observed in all the HST/FOS spectra. The strength of Ly-alpha is nearly constant (approximately 5 x 10(exp -14) erg/sq cm.s), while the 1750 A continuum varies by a factor of approximately 50, from approximately 0.6 to 31.6 x 10(exp -15) ergs/sq cm.s.A. The behavior of the Ly-alpha emission line flux and continuum flux is similar to that of the only other well observed blazar, 3C 273, which shows constant line flux while the continuum varies by a factor of approximately 3. This near-constancy of emission-line flux in the two best-studied blazars suggests that the highly variable beamed continuum is not a significant source of photoionization for the gas. Some other source, such as thermal emission from an accretion disk, must be providing a significant fraction of the photoionizing flux in these objects. The large amplitude variability seen at gamma-ray energies must be due to changes in the energetic electrons in the jet rather than changes in the external photon field.

  15. The connection between the 15 GHz radio and gamma-ray emission in blazars

    NASA Astrophysics Data System (ADS)

    Max-Moerbeck, W.; Richards, J. L.; Hovatta, T.; Pavlidou, V.; Pearson, T. J.; Readhead, A. C. S.; King, O. G.; Reeves, R.

    2015-03-01

    Since mid-2007 we have carried out a dedicated long-term monitoring programme at 15 GHz using the Owens Valley Radio Observatory 40 meter telescope (OVRO 40m). One of the main goals of this programme is to study the relation between the radio and gamma-ray emission in blazars and to use it as a tool to locate the site of high energy emission. Using this large sample of objects we are able to characterize the radio variability, and study the significance of correlations between the radio and gamma-ray bands. We find that the radio variability of many sources can be described using a simple power law power spectral density, and that when taking into account the red-noise characteristics of the light curves, cases with significant correlation are rare. We note that while significant correlations are found in few individual objects, radio variations are most often delayed with respect to the gamma-ray variations. This suggests that the gamma-ray emission originates upstream of the radio emission. Because strong flares in most known gamma-ray-loud blazars are infrequent, longer light curves are required to settle the issue of the strength of radio-gamma cross-correlations and establish confidently possible delays between the two. For this reason continuous multiwavelength monitoring over a longer time period is essential for statistical tests of jet emission models.

  16. Discovery of a GeV Blazar Shining Through the Galactic Plane

    SciTech Connect

    Vandenbroucke, J.; Buehler, R.; Ajello, M.; Bechtol, K.; Bellini, A.; Bolte, M.; Cheung, C.C.; Civano, F.; Donato, D.; Fuhrmann, L.; Funk, S.; Healey, S.E.; Hill, A.B.; Knigge, C.; Madejski, G.M.; Romani, R.W.; Santander-Garcia, M.; Shaw, M.S.; Steeghs, D.; Torres, M.A.P.; Van Etten, A.; /Stanford U., HEPL /KIPAC, Menlo Park /SLAC /Texas U., Astron. Dept.

    2011-08-11

    The Fermi Large Area Telescope (LAT) discovered a new gamma-ray source near the Galactic plane, Fermi J0109+6134, when it flared brightly in 2010 February. The low Galactic latitude (b = -1.2{sup o}) indicated that the source could be located within the Galaxy, which motivated rapid multi-wavelength follow-up including radio, optical, and X-ray observations. We report the results of analyzing all 19 months of LAT data for the source, and of X-ray observations with both Swift and the Chandra X-ray Observatory. We determined the source redshift, z = 0.783, using a Keck LRIS observation. Finally, we compiled a broadband spectral energy distribution (SED) from both historical and new observations contemporaneous with the 2010 February flare. The redshift, SED, optical line width, X-ray obsorption, and multi-band variability indicate that this new Gev source is a blazar seen through the Galactic plane. Because several of the optical emission lines have equivalent width > 5 {angstrom}, this blazar belongs in the flat-spectrum radio quasar category.

  17. Relativistic Beaming Effect in Fermi Blazars

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Bastieri, D.; Yang, J. H.; Liu, Y.; Wu, D. X.; Li, S. H.

    2014-09-01

    The most identified sources observed by Fermi/LAT are blazars, based on which we can investigate the emission mechanisms and beaming effect in the γ-ray bands for blazars. Here, we used the compiled around 450 Fermi blazars with the available X-ray observations to estimate their Doppler factors and compared them with the integral γ-ray luminosity in the range of 1-100 GeV. It is interesting that the integral γ-ray luminosity is closely correlated with the estimated Doppler factor, for the whole sample. When the dependence of the correlation between them and the X-ray luminosity is removed, the correlation is still strong, which suggests that the γ-ray emissions are strongly beamed.

  18. Q0906+6930: Highest Redshift Blazar

    SciTech Connect

    Romani, R

    2004-06-25

    The authors report the discovery of a radio-loud flat-spectrum QSO at z = 5.47 with properties similar to those of the EGRET {gamma}-ray blazars. This source is the brightest radio QSO at z > 5, with a pc-scale radio jet and a black hole mass estimate {approx}> 10{sup 10} M{sub {circle_dot}}. It appears to be the most distant blazar discovered to date. High energy observations of this source can provide powerful probes of the background radiation in the early universe.

  19. GRB 130427A AND SN 2013cq: A MULTI-WAVELENGTH ANALYSIS OF AN INDUCED GRAVITATIONAL COLLAPSE EVENT

    SciTech Connect

    Ruffini, R.; Wang, Y.; Enderli, M.; Muccino, M.; Kovacevic, M.; Bianco, C. L.; Pisani, G. B.; Rueda, J. A.; Penacchioni, A. V.

    2015-01-01

    We performed a data analysis of the observations by the Swift, NuStar, and Fermi satellites in order to probe the induced gravitational collapse (IGC) paradigm for gamma-ray bursts (GRBs) associated with supernovae (SNe) in the terra incognita of GRB 130427A. We compare our data analysis with those in the literature. We have verified that GRB 130427A conforms to the IGC paradigm by examining the power law behavior of the luminosity in the early 10{sup 4} s of the XRT observations. This has led to the identification of the four different episodes of the binary driven hypernovae (BdHNe) and to the prediction, on 2013 May 2, of the occurrence of SN 2013cq, which was also observed in the optical band on 2013 May 13. The exceptional quality of the data has allowed the identification of novel features in Episode 3 including: (1) the confirmation and the extension of the existence of the recently discovered nested structure in the late X-ray luminosity in GRB 130427A, as well as the identification of a spiky structure at 10{sup 2} s in the cosmological rest-frame of the source; (2) a power law emission of the GeV luminosity light curve and its onset at the end of Episode 2; and (3) different Lorentz Γ factors for the emitting regions of the X-ray and GeV emissions in this Episode 3. These results make it possible to test the details of the physical and astrophysical regimes at work in the BdHNe: (1) a newly born neutron star and the supernova ejecta, originating in Episode 1; (2) a newly formed black hole originating in Episode 2; and (3) the possible interaction among these components, observable in the standard features of Episode 3.

  20. GRB 130427A and SN 2013cq: A Multi-wavelength Analysis of An Induced Gravitational Collapse Event

    NASA Astrophysics Data System (ADS)

    Ruffini, R.; Wang, Y.; Enderli, M.; Muccino, M.; Kovacevic, M.; Bianco, C. L.; Penacchioni, A. V.; Pisani, G. B.; Rueda, J. A.

    2015-01-01

    We performed a data analysis of the observations by the Swift, NuStar, and Fermi satellites in order to probe the induced gravitational collapse (IGC) paradigm for gamma-ray bursts (GRBs) associated with supernovae (SNe) in the terra incognita of GRB 130427A. We compare our data analysis with those in the literature. We have verified that GRB 130427A conforms to the IGC paradigm by examining the power law behavior of the luminosity in the early 104 s of the XRT observations. This has led to the identification of the four different episodes of the binary driven hypernovae (BdHNe) and to the prediction, on 2013 May 2, of the occurrence of SN 2013cq, which was also observed in the optical band on 2013 May 13. The exceptional quality of the data has allowed the identification of novel features in Episode 3 including: (1) the confirmation and the extension of the existence of the recently discovered nested structure in the late X-ray luminosity in GRB 130427A, as well as the identification of a spiky structure at 102 s in the cosmological rest-frame of the source; (2) a power law emission of the GeV luminosity light curve and its onset at the end of Episode 2; and (3) different Lorentz Γ factors for the emitting regions of the X-ray and GeV emissions in this Episode 3. These results make it possible to test the details of the physical and astrophysical regimes at work in the BdHNe: (1) a newly born neutron star and the supernova ejecta, originating in Episode 1; (2) a newly formed black hole originating in Episode 2; and (3) the possible interaction among these components, observable in the standard features of Episode 3.

  1. TIME DELAY AND ACCRETION DISK SIZE MEASUREMENTS IN THE LENSED QUASAR SBS 0909+532 FROM MULTIWAVELENGTH MICROLENSING ANALYSIS

    SciTech Connect

    Hainline, Laura J.; Morgan, Christopher W.; MacLeod, Chelsea L.; Landaal, Zachary D.; Kochanek, C. S.; Harris, Hugh C.; Tilleman, Trudy; Goicoechea, L. J.; Shalyapin, V. N.

    2013-09-01

    We present three complete seasons and two half-seasons of Sloan Digital Sky Survey (SDSS) r-band photometry of the gravitationally lensed quasar SBS 0909+532 from the U.S. Naval Observatory, as well as two seasons each of SDSS g-band and r-band monitoring from the Liverpool Robotic Telescope. Using Monte Carlo simulations to simultaneously measure the system's time delay and model the r-band microlensing variability, we confirm and significantly refine the precision of the system's time delay to {Delta}t{sub AB} = 50{sub -4}{sup +2} days, where the stated uncertainties represent the bounds of the formal 1{sigma} confidence interval. There may be a conflict between the time delay measurement and a lens consisting of a single galaxy. While models based on the Hubble Space Telescope astrometry and a relatively compact stellar distribution can reproduce the observed delay, the models have somewhat less dark matter than we would typically expect. We also carry out a joint analysis of the microlensing variability in the r and g bands to constrain the size of the quasar's continuum source at these wavelengths, obtaining log {l_brace}(r{sub s,r}/cm)[cos i/0.5]{sup 1/2}{r_brace} = 15.3 {+-} 0.3 and log {l_brace}(r{sub s,g}/cm)[cos i/0.5]{sup 1/2}{r_brace} = 14.8 {+-} 0.9, respectively. Our current results do not formally constrain the temperature profile of the accretion disk but are consistent with the expectations of standard thin disk theory.

  2. Tracking a CME from Cradle to Grave: A Multi-wavelength Analysis of the February 6-7, 1997 Event

    NASA Astrophysics Data System (ADS)

    Gopalswamy, N.; Kundu, M. R.; Hanaoka, Y.; Kosugi, T.; Hudson, H.; Nitta, N.; Thompson, B.; Gurman, J.; Plunkett, S.; Howard, R.; Burkepile, J.

    1997-05-01

    The partially earth-directed coronal mass ejection (CME) event of 1997 February 6-7 originated from the southwest quadrant of the sun. The CME accelerated from 170 km/s to about 830 km/s when it reached a distance of 25 solar radii. The CME was an arcade eruption followed by bright prominence core structures. The prominence core was tracked continuously from the solar surface to the interplanetary medium by combining data from the Nobeyama radioheliograph (microwaves), Mauna Loa Solar Observatory (He 10830 { Angstroms}), SOHO/EIT (EUV) and SOHO/LASCO (white light). The CME was accompanied by an arcade formation, fully observed by the YOHKOH/SXT (soft X-rays) and SOHO/EIT (EUV). The X-ray and EUV observations suggest that the reconnection proceeded from the northwest end to the southeast end of a filament channel. In the SOHO/EIT images, the the feet of the soft X-ray arcade were observed as EUV ribbons. The CME event also caused a medium sized geomagnetic storm: The hourly equatorial Dst values attained storm level during 18:00-19:00 UT on February 09. This means the disturbance took about 2.25 days to reach the Earth. The first signatures of an IP shock was a pressure jump in the WIND data around 13:00 UT on Feb 09, 1997 which lasted for about 14 hours, followed by flux rope signatures. This CME event confirms a number of ideas about CMEs: The three part structure (frontal bright arcade, dark cavity and prominence core), disappearing filament, elongated arcade formation, and terrestrial effects. We make use of the excellent data coverage from the solar surface to the Earth to address a number of issues regarding the origin and propagation of the geoeffective solar disturbances. We benefited from discussions at the first SOHO-Yohkoh Coordinated Data Analysis Workshop, held March 3-7, 1997, at Goddard Space Flight Center.

  3. FERMI view of the TeV blazar Markarian 421

    SciTech Connect

    Paneque, D; Raino, S.; Chiang, J.; Mazziotta, M.N.; Tramacere, A.; /SLAC /KIPAC, Menlo Park /CIFS, Turin

    2010-08-26

    The high energy component of the TeV blazar Markarian 421 has been extensively studied since the beginning of the 90s, when the source was first detected at gamma-rays with EGRET and the Whipple Telescope, yet the source is still far from being understood. The high sensitivity, large dynamic range, and excellent time coverage of the Fermi Large Area Telescope (LAT), all representing significant advances over previous gamma-ray observations, will play a key role in the elucidation of the physical processes underlying the high energy emission of this blazar. In this presentation we show the results from almost 6 months (4 August 2008 to 20 January 2009) of observation with LAT. We report significant flux/spectral variability on a range of time scales from weeks to days, and an energy spectrum from 0.1 GeV to 300 GeV, overlapping with the energy ranges covered by the current generation of Cherenkov Telescopes. Results on the observations of the BLLac object Markarian 421 collected in the first months of operation of the Fermi satellite have been presented. Light curves on weekly and daily timescales have been shown, as well as the results of the spectral analysis in the energy range between 100 MeV and 300 GeV, covered for the first time by a satellite experiment overlapping the lower energy observations from Cherenkov telescopes on earth. These results are still preliminary and will be enriched and completed soon by a forthcoming publication. The results shown here demonstrate the great performance of Fermi-LAT to study the gamma-emission from Mrk421 (and blazars in general) over a large dynamic range and also on short timescales, which is expected to be of key importance for the study of the emission of the source in a coordinated way with other instruments covering other energy ranges.

  4. Upper Limits from Five Years of Blazar Observations with the VERITAS Cherenkov Telescopes

    NASA Astrophysics Data System (ADS)

    Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Biteau, J.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Chen, X.; Ciupik, L.; Connolly, M. P.; Cui, W.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Gyuk, G.; Hütten, M.; Håkansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kelley-Hoskins, N.; Kertzman, M.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Nguyen, T.; Nieto, D.; O’Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Park, N.; Perkins, J. S.; Pichel, A.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Vincent, S.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Williams, D. A.; Zitzer, B.; the VERITAS collaboration; Fumagalli, M.; Prochaska, J. X.

    2016-06-01

    Between the beginning of its full-scale scientific operations in 2007 and 2012, the VERITAS Cherenkov telescope array observed more than 130 blazars; of these, 26 were detected as very-high-energy (VHE; E > 100 GeV) γ-ray sources. In this work, we present the analysis results of a sample of 114 undetected objects. The observations constitute a total live-time of ∼570 hr. The sample includes several unidentified Fermi-Large Area Telescope (LAT) sources (located at high Galactic latitude) as well as all the sources from the second Fermi-LAT catalog that are contained within the field of view of the VERITAS observations. We have also performed optical spectroscopy measurements in order to estimate the redshift of some of these blazars that do not have spectroscopic distance estimates. We present new optical spectra from the Kast instrument on the Shane telescope at the Lick observatory for 18 blazars included in this work, which allowed for the successful measurement or constraint on the redshift of four of them. For each of the blazars included in our sample, we provide the flux upper limit in the VERITAS energy band. We also study the properties of the significance distributions and we present the result of a stacked analysis of the data set, which shows a 4σ excess.

  5. X-ray and gamma-ray polarization signatures of 3D multi-zone time-dependent hadronic model of blazar emission

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Diltz, Chris Scott; Boettcher, Markus

    2016-04-01

    The origin of the high-energy spectral component of blazar emission is still controversial. Polarization signatures can provide additional diagnostics on the leptonic and the hadronic models. We have developed a 3D multi-zone, time-dependent hadronic model based on Fokker-Planck equations. Coupled with a polarization-dependent radiation transfer code 3DPol, we derive the snap-shot spectral energy distributions and frequency-dependent polarization signatures, as well as multi-wavelength light curves and polarization variations. These findings can be confronted with future high-energy polarization observations to distinguish between the leptonic and the hadronic models.

  6. Coordinated Multiwavelength Observations of PKS 0528+134 in Quiescence

    NASA Astrophysics Data System (ADS)

    Boettcher, Markus; Palma, N.

    2011-01-01

    We report results of an intensive multiwavelength campaign on the prominent high-redshift (z = 2.06) gamma-ray bright blazar PKS 0528+134 in September - October 2009. The campaign was centered on four 30 ksec pointings with XMM-Newton, supplemented with ground-based optical (MDM, Perkins) and radio (UMRAO, Medicina, Metsaehovi, Noto, SMA) observations as well as long-term X-ray monitoring with RXTE and gamma-ray monitoring by Fermi. We find significant variability on 1 day time scales in the optical regime, accompanied by a weak redder-when-brighter trend. X-ray variability is found on longer ( 1 week) time scales, while the Fermi light curve shows no evidence for variability, neither in flux nor spectral index. We constructed four simultaneous spectral energy distributions, which can all be fit satisfactorily with a one-zone leptonic jet model. This work was supported by NASA through XMM-Newton Guest Observer Grant NNX09AV45G.

  7. Evidence for quasi-periodic modulation in the gamma-ray blazar PG 1553+113

    NASA Astrophysics Data System (ADS)

    Cutini, Sara; Ciprini, Stefano; Larsson, Stefan; Thompson, David John; Stamerra, Antonio; Fermi LAT Collaboration

    2016-01-01

    For the first time a gamma-ray and multiwavelength nearly-periodic oscillation in an active galactic nucleus is reported using the Fermi Large Area Telescope (LAT). A quasi-periodicity in the gamma-ray flux (E>100 MeV and E>1 GeV) is observed from the well-known GeV/TeV BL Lac object PG 1553+113 (Ackermann et al. submitted). The significance of the 2.18 +/- 0.08 year-period gamma-ray modulation, seen in 3.5 oscillation maxima observed, is supported by significant cross-correlated variations observed in radio and optical flux light curves, through data collected in the OVRO, Tuorla, KAIT, and CSS monitoring programs and Swift UVOT. The optical cycle, appearing in about 10 years of data, has a similar period, while the radio-band oscillation observed at 15 GHz is less regular and coherent. The available X-ray flux data obtained by Swift XRT appears also to be linearly correlated with the gamma-ray flux. Further long-term multi-wavelength monitoring of this blazar may discriminate among the possible explanations for this first evidence of periodicity.

  8. Multiwavelength Search and Studies of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2016-06-01

    Since 1950s, Byurakan Astrophysical Observatory (BAO) has always been one of the centres for surveys and studies of active galaxies. Here I review our search and studies of active galaxies during last 30 years using various wavelength ranges, as well as some recent related works. These projects since late 1980s were focused on multiwavelength search and studies of AGN and Starbursts (SB). 1103 blue stellar objects (BSOs) on the basis of their UV-excess were selected using Markarian Survey (First Byurakan Survey, FBS) plates and Markarian's criteria used for the galaxies. Among many blue stars, QSOs and Seyfert galaxies were found by follow-up observations. 1577 IRAS point sources were optically identified using FBS low-dispersion spectra and many AGN, SB and high-luminosity IR galaxies (LIRG/ULIRG) were discovered. 32 extremely high IR/opt flux ratio galaxies were studies with Spitzer. 2791 ROSAT FSC sources were optically identified using Hamburg Quasar Survey (HQS) low-dispersion spectra and many AGN were discovered by follow-up observations. Fine analysis of emission line spectra was carried out using spectral line decomposition software to establish true profiles and calculate physical parameters for the emitting regions, as well as to study the spectral variability of these objects. X-ray and radio selection criteria were used to find new AGN and variable objects for further studies. Multiwavelength approach allowed revealing many new AGN and SB and obtaining a number of interesting relations using their observational characteristics and physical properties.

  9. Radio variability and random walk noise properties of four blazars

    SciTech Connect

    Park, Jong-Ho; Trippe, Sascha E-mail: trippe@astro.snu.ac.kr

    2014-04-10

    We present the results of a time series analysis of the long-term radio light curves of four blazars: 3C 279, 3C 345, 3C 446, and BL Lacertae. We exploit the database of the University of Michigan Radio Astronomy Observatory monitoring program which provides densely sampled light curves spanning 32 years in time in three frequency bands located at 4.8, 8, and 14.5 GHz. Our sources show mostly flat or inverted (spectral indices –0.5 ≲ α ≲ 0) spectra, in agreement with optically thick emission. All light curves show strong variability on all timescales. Analyzing the time lags between the light curves from different frequency bands, we find that we can distinguish high-peaking flares and low-peaking flares in accordance with the classification of Valtaoja et al. The periodograms (temporal power spectra) of the observed light curves are consistent with random-walk power-law noise without any indication of (quasi-)periodic variability. The fact that all four sources studied are in agreement with being random-walk noise emitters at radio wavelengths suggests that such behavior is a general property of blazars.

  10. Optical flux behaviour of a sample of Fermi blazars

    NASA Astrophysics Data System (ADS)

    Marchesini, E. J.; Andruchow, I.; Cellone, S. A.; Combi, J. A.; Zibecchi, L.; Martí, J.; Romero, G. E.; Muñoz-Arjonilla, A. J.; Luque-Escamilla, P.; Sánchez-Sutil, J. R.

    2016-06-01

    Aims: We aim at investigating the time-behaviour of a sample of gamma-ray blazars. We present the results from a 13 month-long optical photometry monitoring campaign of the blazars PKS 0048-097, PKS 0754+100, [HB89] 0827+243, PKS 0851+202, PKS 1253-055, PKS 1510-089, PKS 1749+096, PKS 2230+114 and PKS 2251+158. Methods: We analyse the variability of each object, focusing on different time-scales (long term, short term, and microvariability), in an attempt to achieve a statistical comparison of the results. Results: After applying a geometric model to explain the variability results, we found that it is possible that a slight change in the direction of the jet generates the variations detected in some objects during this campaign. Differential photometry results used in the statistical analysis reported in Table 2 are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (http://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/591/A21

  11. Blazar Continuum Variability II: Entering the GLAST Era

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.

    2005-01-01

    Intense, highly-variable gamma-ray emission from blazars was a principal discovery made with EGRET on the Compton Gamma Ray Observatory. The EGRET data remain a valuable resource for modeling of blazar astrophysics and for planning of future gamma-ray missions such as AGILE and GLAST. This presentation will review a bit of history and summarize the EGRET blazar legacy, with emphasis on work done since the end of the Compton Observatory mission.

  12. SEARCHING FOR NEW {gamma}-RAY BLAZAR CANDIDATES IN THE THIRD PALERMO BAT HARD X-RAY CATALOG WITH WISE

    SciTech Connect

    Maselli, A.; Cusumano, G.; La Parola, V.; Segreto, A.; Massaro, F.; D'Abrusco, R.; Paggi, A.; Smith, Howard A.; Tosti, G.

    2013-06-01

    We searched for {gamma}-ray blazar candidates among the 382 unidentified hard X-ray sources of the third Palermo BAT Catalog (3PBC) obtained from the analysis of 66 months of Swift Burst Alert Telescope (BAT) survey data and listing 1586 sources. We adopted a recently developed association method based on the peculiar infrared colors that characterize the {gamma}-ray blazars included in the second catalog of active galactic nuclei detected by the Fermi Large Area Telescope. We used this method exploiting the data of the all-sky survey performed by the Wide-field Infrared Survey Explorer (WISE) to establish correspondences between unidentified 3PBC sources and WISE {gamma}-ray blazar candidates located within the BAT positional uncertainty region at a 99% confidence level. We obtained a preliminary list of candidates for which we analyzed all the available data in the Swift archive to complement the information in the literature and in the radio, infrared, and optical catalogs with the information on their optical-UV and soft X-ray emission. Requiring the presence of radio and soft X-ray counterparts consistent with the infrared positions of the selected WISE sources, as well as a blazar-like radio morphology, we finally obtained a list of 24 {gamma}-ray blazar candidates.

  13. Fast fiber-optic multi-wavelength pyrometer

    NASA Astrophysics Data System (ADS)

    Fu, Tairan; Tan, Peng; Pang, Chuanhe; Zhao, Huan; Shen, Yi

    2011-06-01

    A fast fiber-optic multi-wavelength pyrometer was developed for the ultraviolet-visible-near infrared spectra from 200 nm to 1700 nm using a CCD detector and an InGaAs detector. The pyrometer system conveniently and quickly provides the sufficient choices of multiple measurement wavelengths using optical diffraction, which avoids the use of narrow-band filters. Flexible optical fibers are used to transmit the radiation so the pyrometer can be used for temperature measurements in harsh environments. The setup and calibrations (wavelength calibration, nonlinearity calibration, and radiation response calibration) of this pyrometer system were described. Development of the multi-wavelength pyrometer involved optimization of the bandwidth and temperature discrimination of the multiple spectra data. The analysis results showed that the wavelength intervals, ΔλCCD = 30 nm and ΔλInGaAs = 50 nm, are the suitable choices as a tradeoff between the simple emissivity model assumption and the multiple signal discrimination. The temperature discrimination was also quantificationally evaluated for various wavelengths and temperatures. The measurement performance of the fiber-optic multi-wavelength pyrometer was partially verified through measurements with a high-temperature blackbody and actual hot metals. This multi-wavelength pyrometer can be used for remote high-temperature measurements.

  14. Blazars in the Fermi Era: The OVRO 40 m Telescope Monitoring Program

    NASA Astrophysics Data System (ADS)

    Richards, Joseph L.; Max-Moerbeck, Walter; Pavlidou, Vasiliki; King, Oliver G.; Pearson, Timothy J.; Readhead, Anthony C. S.; Reeves, Rodrigo; Shepherd, Martin C.; Stevenson, Matthew A.; Weintraub, Lawrence C.; Fuhrmann, Lars; Angelakis, Emmanouil; Zensus, J. Anton; Healey, Stephen E.; Romani, Roger W.; Shaw, Michael S.; Grainge, Keith; Birkinshaw, Mark; Lancaster, Katy; Worrall, Diana M.; Taylor, Gregory B.; Cotter, Garret; Bustos, Ricardo

    2011-06-01

    The Large Area Telescope (LAT) aboard the Fermi Gamma-ray Space Telescope provides an unprecedented opportunity to study gamma-ray blazars. To capitalize on this opportunity, beginning in late 2007, about a year before the start of LAT science operations, we began a large-scale, fast-cadence 15 GHz radio monitoring program with the 40 m telescope at the Owens Valley Radio Observatory. This program began with the 1158 northern (δ > -20°) sources from the Candidate Gamma-ray Blazar Survey and now encompasses over 1500 sources, each observed twice per week with about 4 mJy (minimum) and 3% (typical) uncertainty. Here, we describe this monitoring program and our methods, and present radio light curves from the first two years (2008 and 2009). As a first application, we combine these data with a novel measure of light curve variability amplitude, the intrinsic modulation index, through a likelihood analysis to examine the variability properties of subpopulations of our sample. We demonstrate that, with high significance (6σ), gamma-ray-loud blazars detected by the LAT during its first 11 months of operation vary with almost a factor of two greater amplitude than do the gamma-ray-quiet blazars in our sample. We also find a significant (3σ) difference between variability amplitude in BL Lacertae objects and flat-spectrum radio quasars (FSRQs), with the former exhibiting larger variability amplitudes. Finally, low-redshift (z < 1) FSRQs are found to vary more strongly than high-redshift FSRQs, with 3σ significance. These findings represent an important step toward understanding why some blazars emit gamma-rays while others, with apparently similar properties, remain silent.

  15. Coincidence of a high-fluence blazar outburst with a PeV-energy neutrino event

    NASA Astrophysics Data System (ADS)

    Kadler, M.; Krauß, F.; Mannheim, K.; Ojha, R.; Müller, C.; Schulz, R.; Anton, G.; Baumgartner, W.; Beuchert, T.; Buson, S.; Carpenter, B.; Eberl, T.; Edwards, P. G.; Eisenacher Glawion, D.; Elsässer, D.; Gehrels, N.; Gräfe, C.; Gulyaev, S.; Hase, H.; Horiuchi, S.; James, C. W.; Kappes, A.; Kappes, A.; Katz, U.; Kreikenbohm, A.; Kreter, M.; Kreykenbohm, I.; Langejahn, M.; Leiter, K.; Litzinger, E.; Longo, F.; Lovell, J. E. J.; McEnery, J.; Natusch, T.; Phillips, C.; Plötz, C.; Quick, J.; Ros, E.; Stecker, F. W.; Steinbring, T.; Stevens, J.; Thompson, D. J.; Trüstedt, J.; Tzioumis, A. K.; Weston, S.; Wilms, J.; Zensus, J. A.

    2016-08-01

    The astrophysical sources of the extraterrestrial, very high-energy neutrinos detected by the IceCube collaboration remain to be identified. Gamma-ray (γ-ray) blazars have been predicted to yield a cumulative neutrino signal exceeding the atmospheric background above energies of 100 TeV, assuming that both the neutrinos and the γ-ray photons are produced by accelerated protons in relativistic jets. As the background spectrum falls steeply with increasing energy, the individual events with the clearest signature of being of extraterrestrial origin are those at petaelectronvolt energies. Inside the large positional-uncertainty fields of the first two petaelectronvolt neutrinos detected by IceCube, the integrated emission of the blazar population has a sufficiently high electromagnetic flux to explain the detected IceCube events, but fluences of individual objects are too low to make an unambiguous source association. Here, we report that a major outburst of the blazar PKS B1424-418 occurred in temporal and positional coincidence with a third petaelectronvolt-energy neutrino event (HESE-35) detected by IceCube. On the basis of an analysis of the full sample of γ-ray blazars in the HESE-35 field, we show that the long-term average γ-ray emission of blazars as a class is in agreement with both the measured all-sky flux of petaelectronvolt neutrinos and the spectral slope of the IceCube signal. The outburst of PKS B1424-418 provides an energy output high enough to explain the observed petaelectronvolt event, suggestive of a direct physical association.

  16. Multiwavelength Observations of Markarian 421 During a TeV/X-Ray Flare

    NASA Technical Reports Server (NTRS)

    Bertsch, D. L.; Bruhweiler, F.; Macomb, D. J.; Cheng, K.-P.; Carter-Lewis, D. A.; Akerlof, C. W.; Aller, H. D.; Aller, M. F.; Buckley, J. H.; Cawley, M. F.

    1995-01-01

    A TeV flare from the BL Lac object Mrk 421 was detected in May of 1994 by the Whipple Observatory air Cherenkov experiment during which the flux above 250 GeV increased by nearly an order of magnitude over a 2-day period. Contemporaneous observations by ASCA showed the X-ray flux to be in a very high state. We present these results, combined with the first ever simultaneous or nearly simultaneous observations at GeV gamma-ray, UV, IR, mm, and radio energies for this nearest BL Lac object. While the GeV gamma-ray flux increased slightly, there is little evidence for variability comparable to that seen at TeV and X-ray energies. Other wavelengths show even less variability. This provides important constraints on the emission mechanisms at work. We present the multiwavelength spectrum of this gamma-ray blazar for both quiescent and flaring states and discuss the data in terms of current models of blazar emission.

  17. The evolutionary sequence of Fermi blazars

    NASA Astrophysics Data System (ADS)

    Cha, Yongjuan; Zhang, Haojing; Zhang, Xiong; Xiong, Dingrong; Li, Bijun; Dong, Xia; Li, Jin

    2014-02-01

    Using γ-ray data ( α γ , F γ ) detected by Fermi Large Area Telescope (LAT) and black hole mass which has been compiled from literatures for 116 Fermi blazars, we calculated intrinsic γ-ray luminosity, intrinsic bolometric luminosity, intrinsic Eddington ratio and studied the relationships between all above parameters and redshift, between α γ and L γ . Furthermore, we obtained the histograms of key parameters. Our results are the following: (1) The main reason for the evolutionary sequence of three subclasses (HBLs, LBLs, FSRQs) may be Eddington ratio rather than black hole mass; (2) FSRQs occupy in the earlier, high-luminosity, high Eddington ratio, violent phase of the galactic evolution sequence, while BL Lac objects occur in the low luminosity, low Eddington ratio, late phase of the galactic evolution sequence; (3) These results imply that the evolutionary track of Fermi blazars is FSRQs ⟶ LBLs ⟶ HBLs.

  18. Radio observations of a few selected blazars

    NASA Technical Reports Server (NTRS)

    Saikia, D. J.; Salter, C. J.; Neff, S. G.; Gower, A. C.; Sinha, R. P.

    1987-01-01

    The paper presents total-intensity and linear-polarization observations of four selected blazars, 0716+714, 0752+258, 1156+295 and 1400+162, with the VLA A-array, and MERLIN and EVN observations of 1400+162. The sources 0752+258 and 1400+162 which have nearly constant optical polarization, have well-defined double-lobed radio structure, with relatively weak radio cores, and are likely to be at large viewing angles. In addition, 0752+258 appears to be a twin-jet blazar. The position angle (PA) of the VLBI jet in 1400+162 is close to that of the arcsec-scale jet near the nucleus, as well as the optical and 2-cm core polarization PAs. The blazars 0716+714 and 1156+295, which exhibit strongly variable optical polarization, have a core-dominated radio structure and perhaps have their jet axes close to the line-of-sight. From polarization observations at 20, 18, 6, and 2 cm, it is found that the rotation measure of the radio core in 0716+714 is about -20 rad/sq m. It is suggested that low values of core rotation measure in core-dominated sources could be consistent with the relativistic beaming models.

  19. High-Frequency Observations of Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, A. P.; Marchenko-Jorstad, S. G.; Mattox, J. R.; Wehrle, A. E.; Aller, M. F.

    2000-01-01

    We report on the results of high-frequency VLBA observations of 42 gamma-ray bright blazars monitored at 22 and 43 GHz between 1993.9 and 1997.6. In 1997 the observations included polarization-sensitive imaging. The cores of gamma-ray blazars are only weakly polarized, with EVPAs (electric-vector position angles) usually within 40 deg of the local direction of the jet. The EVPAs of the jet components are usually within 20 deg of the local jet direction. The apparent speeds of the gamma-ray bright blazars are considerably faster than in the general population of bright compact radio sources. Two X-ray flares (observed with RXTE) of the quasar PKS 1510-089 appear to be related to radio flares, but with the radio leading the X-ray variations by about 2 weeks. This can be explained either by synchrotron self-Compton emission in a component whose variations are limited by light travel time or by the Mirror Compton model.

  20. Flaring Activity from S5 0836+71 (4C71.07): What Can We Learn with Limited Multiwavelength Coverage?

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.; Donato, D.; Akyuz, A.; Fuhrmann, L.; Sokolovsky, K.; Kurtanidze, O.

    2011-01-01

    After a long period of quiescence in gamma rays, blazar S5 0836+71 (4C71.07) flared in the Spring of 2011. We found only limited multiwavelength coverage of the source. An indication of correlated optical/gamma-ray variability is not surprising for a FSRQ like this one. Radio observations at high frequencies, however, had seen a flare in late 2010, with no apparent related gamma-ray activity. This case seems to differ from the traditional pattern of finding gamma-ray flares during times of rising radio emission.

  1. Multiwavelength and Statistical Research in Space Astrophysics

    NASA Technical Reports Server (NTRS)

    Feigelson, Eric D.

    1997-01-01

    The accomplishments in the following three research areas are summarized: multiwavelength study of active galactic nuclei; magnetic activity of young stellar objects; and statistical methodology for astronomical data analysis. The research is largely based on observations of the ROSAT and ASCA X-ray observatories, complemented by ground-based optical and radio studies. Major findings include: discovery of inverse Compton X-ray emission from radio galaxy lobes; creation of the largest and least biased available sample of BL Lac objects; characterization of X-ray and nonthermal radio emission from T Tauri stars; obtaining an improved census of young stars in a star forming region and modeling the star formation history and kinematics; discovery of X-ray emission from protostars; development of linear regression methods and codes for interpreting astronomical data; and organization of the first cross-disciplinary conferences for astronomers and statisticians.

  2. Multiwavelength pyrometry to correct for reflected radiation

    NASA Technical Reports Server (NTRS)

    Ng, Daniel L. P.

    1990-01-01

    Computer curve fitting is used in multiwavelength pyrometry to measure the temperature of a surface in the presence of reflected radiation by decomposing its radiation spectrum. Computer-simulated spectra (at a surface temperature of 1000 K; in the wavelength region 0.3 to 20 microns; with a reflected radiation-source temperature of 700 to 2500 K; and reflector emissivity from 0.1 to 0.9) were generated and decomposed. This method of pyrometry determined the surface temperatures under these conditions to within 5 percent. The practicability of the method was further demonstrated by the successful analysis of a related problem--decomposition of the real spectrum of an infrared source containing two emitters to determine their temperatures.

  3. The Spectral Index Distribution of EGRET Blazars: Prospects for GLAST

    SciTech Connect

    Venters, Tonia M.; Pavlidou, Vasiliki; /SLAC

    2011-11-29

    The intrinsic distribution of spectral indices in GeV energies of gamma-ray-loud blazars is a critical input in determining the spectral shape of the unresolved blazar contribution to the diffuse extragalactic gamma-ray background, as well as an important test of blazar emission theories. We present a maximum-likelihood method of determining the intrinsic spectral index distribution (ISID) of a population of {gamma}-ray emitters which accounts for error in measurement of individual spectral indices, and we apply it to EGRET blazars. We find that the most likely Gaussian ISID for EGRET blazars has a mean of 2.27 and a standard deviation of 0.20. We additionally find some indication that FSRQs and BL Lacs may have different ISIDs (with BL Lacs being harder). We also test for spectral index hardening associated with blazar variability for which we find no evidence. Finally, we produce simulated GLAST spectral index datasets and perform the same analyses. With improved statistics due to the much larger number of resolvable blazars, GLAST data will help us determine the ISIDs with much improved accuracy. Should any difference exist between the ISIDs of BL Lacs and FSRQs or between the ISIDs of blazars in the quiescent and flaring states, GLAST data will be adequate to separate these ISIDs at a significance better than 3{sigma}.

  4. Extreme blazars studied with Fermi-lat and Suzaku: 1ES 0347–121 and blazar candidate HESS J1943+213

    SciTech Connect

    Tanaka, Y. T.; Stawarz, Ł.; Finke, J.; Cheung, C. C.; Dermer, C. D.; Kataoka, J.; Bamba, A.; Dubus, G.; Fukazawa, Y.; Thompson, D. J.

    2014-06-01

    We report on our study of high-energy properties of two peculiar TeV emitters: the 'extreme blazar' 1ES 0347–121 and the 'extreme blazar candidate' HESS J1943+213 located near the Galactic plane. Both objects are characterized by quiescent synchrotron emission with flat spectra extending up to the hard X-ray range, and both were reported to be missing GeV counterparts in the Fermi Large Area Telescope (LAT) two-year Source Catalog. We analyze a 4.5 yr accumulation of the Fermi-LAT data, resulting in the detection of 1ES 0347–121 in the GeV band, as well as in improved upper limits for HESS J1943+213. We also present the analysis results of newly acquired Suzaku data for HESS J1943+213. The X-ray spectrum is well represented by a single power law extending up to 25 keV with photon index 2.00 ± 0.02 and a moderate absorption in excess of the Galactic value, which is in agreement with previous X-ray observations. No short-term X-ray variability was found over the 80 ks duration of the Suzaku exposure. Under the blazar hypothesis, we modeled the spectral energy distributions of 1ES 0347–121 and HESS J1943+213, and we derived constraints on the intergalactic magnetic field strength and source energetics. We conclude that although the classification of HESS J1943+213 has not yet been determined, the blazar hypothesis remains the most plausible option since, in particular, the broadband spectra of the two analyzed sources along with the source model parameters closely resemble each other, and the newly available Wide-field Infrared Survey Explorer and UKIRT Infrared Deep Sky Survey data for HESS J1943+213 are consistent with the presence of an elliptical host at the distance of approximately ∼600 Mpc.

  5. Extreme Blazars Studied with Fermi-LAT and Suzaku: 1ES 0347-121 and Blazar Candidate HESS J1943+213

    NASA Astrophysics Data System (ADS)

    Tanaka, Y. T.; Stawarz, Ł.; Finke, J.; Cheung, C. C.; Dermer, C. D.; Kataoka, J.; Bamba, A.; Dubus, G.; De Naurois, M.; Wagner, S. J.; Fukazawa, Y.; Thompson, D. J.

    2014-06-01

    We report on our study of high-energy properties of two peculiar TeV emitters: the "extreme blazar" 1ES 0347-121 and the "extreme blazar candidate" HESS J1943+213 located near the Galactic plane. Both objects are characterized by quiescent synchrotron emission with flat spectra extending up to the hard X-ray range, and both were reported to be missing GeV counterparts in the Fermi Large Area Telescope (LAT) two-year Source Catalog. We analyze a 4.5 yr accumulation of the Fermi-LAT data, resulting in the detection of 1ES 0347-121 in the GeV band, as well as in improved upper limits for HESS J1943+213. We also present the analysis results of newly acquired Suzaku data for HESS J1943+213. The X-ray spectrum is well represented by a single power law extending up to 25 keV with photon index 2.00 ± 0.02 and a moderate absorption in excess of the Galactic value, which is in agreement with previous X-ray observations. No short-term X-ray variability was found over the 80 ks duration of the Suzaku exposure. Under the blazar hypothesis, we modeled the spectral energy distributions of 1ES 0347-121 and HESS J1943+213, and we derived constraints on the intergalactic magnetic field strength and source energetics. We conclude that although the classification of HESS J1943+213 has not yet been determined, the blazar hypothesis remains the most plausible option since, in particular, the broadband spectra of the two analyzed sources along with the source model parameters closely resemble each other, and the newly available Wide-field Infrared Survey Explorer and UKIRT Infrared Deep Sky Survey data for HESS J1943+213 are consistent with the presence of an elliptical host at the distance of approximately ~600 Mpc.

  6. GeV Blazar flares several parsecs from the central engine. Who pays the seed photon bill?

    NASA Astrophysics Data System (ADS)

    Breiding, Peter; Georganopoulos, Markos; Meyer, Eileen

    2016-04-01

    In Blazars, multi-wavelength observations suggest that some GeV flares take place at the location of the mm VLBI core, several pc from the black hole. This location for the GeV emission requires a yet un-identified source of seed photons to be Inverse Compton scattered to GeV energies. Our model for these flares involves a fast spine and slow sheath configuration for the relativistic jet, where the mildly beamed sheath emission will illuminate with a large opening angle the outer regions of the Molecular Torus. The heated clouds will then radiate and their emission will be relativistically boosted in the spine frame where it can they be up-scattered to GeV energies. We argue, through analytical work and simulations, that this can be the seed photon source that produces the GeV flares.

  7. The unusual multiwavelength properties of the gamma-ray source PMN J1603-4904

    NASA Astrophysics Data System (ADS)

    Müller, Cornelia; Kadler, M.; Ojha, R.; Böck, M.; Krauß, F.; Taylor, G. B.; Wilms, J.; Blanchard, J.; Carpenter, B.; Dauser, T.; Dutka, M.; Edwards, P. G.; Gehrels, N.; Großberger, C.; Hase, H.; Horiuchi, S.; Kreikenbohm, A.; Lovell, J. E. J.; McConville, W.; Phillips, C.; Plötz, C.; Pursimo, T.; Quick, J.; Ros, E.; Schulz, R.; Stevens, J.; Tingay, S. J.; Trüstedt, J.; Tzioumis, A. K.; Zensus, J. A.

    2014-02-01

    Context. We investigate the nature and classification of PMN J1603-4904, a bright radio source close to the Galactic plane, which is associated with one of the brightest hard-spectrum γ-ray sources detected by Fermi/LAT. It has previously been classified as a low-peaked BL Lac object based on its broadband emission and the absence of optical emission lines. Optical measurements, however, suffer strongly from extinction and the absence of pronounced short-time γ-ray variability over years of monitoring is unusual for a blazar. Aims: In this paper, we are combining new and archival multiwavelength data of PMN J1603-4904 in order to reconsider the classification and nature of this unusual γ-ray source. Methods: For the first time, we study the radio morphology of PMN J1603-4904 at 8.4 GHz and 22.3 GHz, and its spectral properties on milliarcsecond scales, based on VLBI observations from the TANAMI program. We combine the resulting images with multiwavelength data in the radio, IR, optical/UV, X-ray, and γ-ray regimes. Results: PMN J1603-4904 shows a symmetric brightness distribution at 8.4 GHz on milliarcsecond scales, with the brightest, and most compact component in the center of the emission region. The morphology is reminiscent of a compact symmetric object (CSO). Such objects, thought to be young radio galaxies, have been predicted to produce γ-ray emission but have not been detected as a class by the Fermi γ-ray telescope so far. Sparse (u,v)-coverage at 22.3 GHz prevents an unambiguous modeling of the source morphology at this higher frequency. Moreover, infrared measurements reveal an excess in the spectral energy distribution (SED), which can be modeled with a blackbody with a temperature of about 1600 K, and which is usually not present in blazar SEDs. Conclusions: The TANAMI VLBI data and the shape of the broadband SED challenge the current blazar classification of one of the brightest γ-ray sources in the sky. PMN J1603-4904 seems to be either a

  8. The Effect of Blazar Spectral Breaks on the Blazar Contribution to the Extragalactic Gamma-Ray Background

    NASA Technical Reports Server (NTRS)

    Venters, Tonia M.; Pavlidou, Vasiliki

    2011-01-01

    The spectral shapes of the contributions of different classes of unresolved gamma-ray emitters can provide insight into their relative contributions to the extragalactic gamma-ray background (EGB) and the natures of their spectra at GeV energies, We calculate the spectral shapes of the contributions to the EGB arising from BL Lacertae type objects (BL Lacs) and flat-spectrum radio quasars (FSRQs) assuming blazar spectra can be described as broken power laws, We fit the resulting total blazar spectral shape to the Fermi Large Area Telescope measurements of the EGB, finding that the best-fit shape reproduces well the shape of the Fermi EGB for various break scenarios. We conclude that a scenario in which the contribution of blazars is dominant cannot be excluded on spectral grounds alone, even if spectral breaks are shown to be common among Fermi blazars. We also find that while the observation of a featureless (within uncertainties) power-law EGB spectrum by Fermi does not necessarily imply a single class of contributing unresolved sources with featureless individual spectra, such an observation and the collective spectra of the separate contributing populations determine the ratios of their contributions. As such, a comparison with studies including blazar gamma-ray luminosity functions could have profound implications for the blazar contribution to the EGB, blazar evolution, and blazar gamma-ray spectra and emission.

  9. Location and origin of gamma-rays in blazars

    NASA Astrophysics Data System (ADS)

    Rani, B.; Krichbaum, T. P.; Hodgson, J. A.; Zensus, J. A.

    2016-05-01

    One of the most intriguing and challenging quests of current astrophysics is to understand the physical conditions and processes responsible for production of high-energy particles, and emission of γ-rays. A combination of high-resolution Very Long Baseline Interferometry (VLBI) images with broadband flux variability measurements is a unique way to probe the emission mechanisms at the bases of jets. Our analysis of γ-ray flux variability observed by the Fermi-LAT (Large Area Telescope) along with the parsec-scale jet kinematics suggests that the γ-ray emission in blazar S5 0716+714 has a significant correlation with the mm-VLBI core flux and the orientation of jet outflow on parsec scales. These results indicate that the inner jet morphology has a tight connection with the observed γ-ray flares. An overview of our current understanding on high-energy radiation processes, their origin, and location is presented here.

  10. Multi-wavelength fluorescence tomography

    NASA Astrophysics Data System (ADS)

    Kwong, Tiffany C.; Lo, Pei-An; Cho, Jaedu; Nouizi, Farouk; Chiang, Huihua K.; Kim, Chang-Seok; Gulsen, Gultekin

    2016-03-01

    The strong scattering and absorption of light in biological tissue makes it challenging to model the propagation of light, especially in deep tissue. This is especially true in fluorescent tomography, which aims to recover the internal fluorescence source distribution from the measured light intensities on the surface of the tissue. The inherently ill-posed and underdetermined nature of the inverse problem along with strong tissue scattering makes Fluorescence Tomography (FT) extremely challenging. Previously, multispectral detection fluorescent tomography (FT) has been shown to improve the image quality of FT by incorporating the spectral filtering of biological tissue to provide depth information to overcome the inherent absorption and scattering limitations. We investigate whether multi-wavelength fluorescent tomography can be used to distinguish the signals from multiple fluorophores with overlapping fluorescence spectrums using a unique near-infrared (NIR) swept laser. In this work, a small feasibility study was performed to see whether multi-wavelength FT can be used to detect subtle shifts in the absorption spectrum due to differences in fluorophore microenvironment.

  11. DEEP BROADBAND OBSERVATIONS OF THE DISTANT GAMMA-RAY BLAZAR PKS 1424+240

    SciTech Connect

    Archambault, S.; Aune, T.; Behera, B.; Chen, X.; Federici, S.; Beilicke, M.; Bugaev, V.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Biteau, J.; Byrum, K.; Cardenzana, J. V; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; Errando, M.; Falcone, A.; Collaboration: VERITAS Collaboration; Fermi LAT Collaboration; and others

    2014-04-10

    We present deep VERITAS observations of the blazar PKS 1424+240, along with contemporaneous Fermi Large Area Telescope, Swift X-ray Telescope, and Swift UV Optical Telescope data between 2009 February 19 and 2013 June 8. This blazar resides at a redshift of z ≥ 0.6035, displaying a significantly attenuated gamma-ray flux above 100 GeV due to photon absorption via pair-production with the extragalactic background light. We present more than 100 hr of VERITAS observations over three years, a multiwavelength light curve, and the contemporaneous spectral energy distributions. The source shows a higher flux of (2.1 ± 0.3) × 10{sup –7} photons m{sup –2} s{sup –1} above 120 GeV in 2009 and 2011 as compared to the flux measured in 2013, corresponding to (1.02 ± 0.08) × 10{sup –7} photons m{sup –2} s{sup –1} above 120 GeV. The measured differential very high energy (VHE; E ≥ 100 GeV) spectral indices are Γ = 3.8 ± 0.3, 4.3 ± 0.6 and 4.5 ± 0.2 in 2009, 2011, and 2013, respectively. No significant spectral change across the observation epochs is detected. We find no evidence for variability at gamma-ray opacities of greater than τ = 2, where it is postulated that any variability would be small and occur on timescales longer than a year if hadronic cosmic-ray interactions with extragalactic photon fields provide a secondary VHE photon flux. The data cannot rule out such variability due to low statistics.

  12. Discovery of an Extreme MeV Blazar with the Swift Burst Alert Telescope

    NASA Technical Reports Server (NTRS)

    Sambruna, R. M.; Markwardt, C. B.; Mushotzky, R. F.; Tueller, J.; Hartman, R.; Brandt, W. N.; Schneider, D> P.; Falcone, A.; Cucchiara, A.; Aller, M. F.

    2006-01-01

    The Burst Alert Telescope (BAT) onboard Swift detected bright emission from 15-195 keV from the source SWIFT J0746.3+2548 (J0746 in the following), identified with the optically-faint (R approx. 19), z=2.979 quasar SDSS J074625.87+244901.2. Here we present Swift and multiwavelength observations of this source. The X-ray emission from J0746 is variable on timescales of hours to weeks in 0.5-8 keV and of a few months in 15-195 keV, but there is no accompanying spectral variability in the 0.5-8 keV band. There is a suggestion that the BAT spectrum, initially very hard (photon index Gamma approx. 0.7), steepened to Gamma approx. 1.3 in a few months, together with a decrease of the 15-195 keV flux by a factor approx. 2. The 0.5-8 keV continuum is well described by a power law with Gamma approx. 1.3, and spectral flattening below 1 keV. The latter can be described with a column density in excess of the Galactic value with intrinsic column density Nz(sub H) approx. 10(exp 22)/sq cm , or with a flatter power law, implying a sharp (Delta(Gamma) less than or approx. 1) break across 16 keV in the quasar's rest-frame. The Spectral Energy Distribution of J0746 is double-humped, with the first component peaking at IR wavelengths and the second component at MeV energies. These properties suggest that J0746 is a a blazar with high gamma-ray luminosity and low peak energy (MeV) stretching the blazar sequence to an extreme.

  13. Future Multiwavelength Studies with the Fermi Large Area Telescope

    NASA Technical Reports Server (NTRS)

    Thompson, David J.

    2011-01-01

    With two and a half years of experience, Fermi LAT contributions to multiwavelength studies have become an integral part of many astrophysical research projects. Future efforts will benefit from (1) Deeper LAT exposures} resulting in more sources; (2) More high-energy, high-angular resolution photons, giving better source locations and imaging; (3) Faster analysis of variability and announcements to the community; and (4) Longer time series for studies of variable source properties in comparison to other wavelengths.

  14. The Radio Variability of Gamma-Ray Blazars

    NASA Astrophysics Data System (ADS)

    Richards, Joseph

    2012-01-01

    Since late 2007, we have regularly monitored over 1100 systematically-selected blazars at 15 GHz using the Owens Valley Radio Observatory 40m radio telescope. The number of sources in the program has grown to nearly 1600, including all the active galactic nuclei associated with Fermi Large Area Telescope (LAT) gamma-ray point source detections north of our declination limit of -20°. Here, we describe the first 42 months of this program, including the automated data reduction pipeline and MySQL database system for storing the reduced data and intermediate data products. Using the "intrinsic modulation index," a maximum-likelihood method, we estimate the variability amplitudes for 1413 sources from their radio light curves and compare the properties of physically-defined subpopulations of the sample. We find that, among our preselected sample, gamma-ray-loud blazars detected by the LAT are significantly more variable at 15 GHz, attributable to a difference in variability between the gamma-ray-loud and gamma-ray-quiet flat spectrum radio quasars. The BL Lacertae objects in the samples do not show this division in variability amplitudes. In the first two years of our program, a 3σ-significant difference between variability amplitudes for sources at redshift z≥1 and for sources at z<1 was found. This difference is found no longer to be significant in the full 42-month data set, particularly after we apply an analysis method to account for the effect of cosmological time dilation. This work was supported in part by NASA grants NNX08AW31G and NNG06GG1G and NSF grant AST-0808050.

  15. The Radio Variability of Gamma-Ray Blazars

    NASA Astrophysics Data System (ADS)

    Richards, Joseph Lee

    2012-05-01

    Since late 2007, we have regularly monitored over 1100 systematically selected blazars at 15 GHz using the Owens Valley Radio Observatory 40 m radio telescope. The number of sources in the program has grown to nearly 1600, including all the active galactic nuclei associated with Fermi Large Area Telescope (LAT) gamma-ray point source detections north of our declination limit of -20°. Here, we describe the first 42 months of this program, including the design and implementation of an automated data reduction pipeline and a MySQL database system for storing the reduced data and intermediate data products. Using the "intrinsic modulation index," a maximum-likelihood method, we estimate the variability amplitudes for 1413 sources from their radio light curves and compare the properties of physically defined subpopulations of the sample. We find that, among our preselected sample, gamma-ray--loud blazars detected by the LAT are significantly more variable at 15 GHz, attributable to a difference in variability between the gamma-ray--loud and gamma-ray--quiet flat spectrum radio quasars. The BL Lacertae objects in the samples do not show this division in variability amplitudes. In the first two years of our program, a 3sigma-significant difference between variability amplitudes for sources at redshift z ≥ 1 and for sources at z < 1 was found. This difference is found no longer to be significant in the full 42-month data set, particularly after we apply an analysis method to account for the effect of cosmological time dilation.

  16. Multiwavelength metasurfaces through spatial multiplexing

    PubMed Central

    Arbabi, Ehsan; Arbabi, Amir; Kamali, Seyedeh Mahsa; Horie, Yu; Faraon, Andrei

    2016-01-01

    Metasurfaces are two-dimensional arrangements of optical scatterers rationally arranged to control optical wavefronts. Despite the significant advances made in wavefront engineering through metasurfaces, most of these devices are designed for and operate at a single wavelength. Here we show that spatial multiplexing schemes can be applied to increase the number of operation wavelengths. We use a high contrast dielectric transmittarray platform with amorphous silicon nano-posts to demonstrate polarization insensitive metasurface lenses with a numerical aperture of 0.46, that focus light at 915 and 1550 nm to the same focal distance. We investigate two different methods, one based on large scale segmentation and one on meta-atom interleaving, and compare their performances. An important feature of this method is its simple generalization to adding more wavelengths or new functionalities to a device. Therefore, it provides a relatively straightforward method for achieving multi-functional and multiwavelength metasurface devices. PMID:27597568

  17. Gamma Ray Pulsars: Multiwavelength Observations

    NASA Technical Reports Server (NTRS)

    Thompson, David J.

    2004-01-01

    High-energy gamma rays are a valuable tool for studying particle acceleration and radiation in the magnetospheres of energetic pulsars. The seven or more pulsars seen by instruments on the Compton Gamma Ray Observatory (CGRO) show that: the light curves usually have double-peak structures (suggesting a broad cone of emission); gamma rays are frequently the dominant component of the radiated power; and all the spectra show evidence of a high-energy turnover. For all the known gamma-ray pulsars, multiwavelength observations and theoretical models based on such observations offer the prospect of gaining a broad understanding of these rotating neutron stars. The Gamma-ray Large Area Space Telescope (GLAST), now in planning for a launch in 2006, will provide a major advance in sensitivity, energy range, and sky coverage.

  18. Multiwavelength metasurfaces through spatial multiplexing.

    PubMed

    Arbabi, Ehsan; Arbabi, Amir; Kamali, Seyedeh Mahsa; Horie, Yu; Faraon, Andrei

    2016-01-01

    Metasurfaces are two-dimensional arrangements of optical scatterers rationally arranged to control optical wavefronts. Despite the significant advances made in wavefront engineering through metasurfaces, most of these devices are designed for and operate at a single wavelength. Here we show that spatial multiplexing schemes can be applied to increase the number of operation wavelengths. We use a high contrast dielectric transmittarray platform with amorphous silicon nano-posts to demonstrate polarization insensitive metasurface lenses with a numerical aperture of 0.46, that focus light at 915 and 1550 nm to the same focal distance. We investigate two different methods, one based on large scale segmentation and one on meta-atom interleaving, and compare their performances. An important feature of this method is its simple generalization to adding more wavelengths or new functionalities to a device. Therefore, it provides a relatively straightforward method for achieving multi-functional and multiwavelength metasurface devices. PMID:27597568

  19. Multiwavelength studies of Markarian galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.; Abrahamyan, H. V.; Paronyan, G. M.; Harutyunyan, G. S.

    2013-10-01

    Markarian galaxies are the result of the First Byurakan Survey (FBS) conducted in 1965-1980 by B.E. Markarian et al. The sample consists of 1515 UV-excess galaxies containing many active galaxies, both AGN and starburst (SB) galaxies that are interesting from the point of view of galaxy evolution and multiwavelength studies. Several catalogs of Markarian galaxies have been published; however, multiwavelength (MW) data were not provided and matched for more efficient investigations. Moreover, SDSS spectra now give possibility for better classification by activity types, and we have accomplished fine classification obtaining new types and subtypes for most of the objects. We have cross-correlated the Markarian catalogue with all available large-area MW catalogues at various wavelengths, from X-ray to radio: ROSAT BSC and FSC, GALEX, APM, MAPS, USNO B1.0, GSC 2.3.2, SDSS, 2MASS PSC and ESC, WISE, AKARI-IRC, IRAS PSC, FSC, and SSSC, AKARI-FIS, GB6, NVSS, FIRST, SUMSS, WENSS, and 7C providing 35 photometric data-points, as well as the Digitized FBS (DFBS, http://byurakan.phys.uniroma1.it/) and Hamburg Quasar Survey (HQS) low-dispersion spectra. The Armenian Virtual Observatory (ArVO, http://www.aras.am/Arvo/arvo.htm) services have been used for cross-correlations and extraction of DFBS spectra; MW SEDs have been built using the IVOA tools, and MW classification has been accomplished. Diagrams with MW flux ratios have been built to reveal objects with extreme characteristics. The classifications have been matched with these flux ratios. A MW catalog of Markarian galaxies has been compiled.

  20. THE WISE BLAZAR-LIKE RADIO-LOUD SOURCES: AN ALL-SKY CATALOG OF CANDIDATE γ-RAY BLAZARS

    SciTech Connect

    D'Abrusco, R.; Paggi, A.; Smith, H. A.; Massaro, F.; Masetti, N.

    2014-11-01

    We present a catalog of radio-loud candidate γ-ray emitting blazars with WISE mid-infrared colors similar to the colors of confirmed γ-ray blazars. The catalog is assembled from WISE sources detected in all four WISE filters, with colors compatible with the three-dimensional locus of the WISE γ-ray emitting blazars, and which can be spatially cross-matched with radio sources from one of the three radio surveys: NVSS, FIRST, and/or SUMSS. Our initial WISE selection uses a slightly modified version of previously successful algorithms. We then select only the radio-loud sources using a measure of the radio-to-IR flux, the q {sub 22} parameter, which is analogous to the q {sub 24} parameter known in the literature but which instead uses the WISE band-four flux at 22 μm. Our final catalog contains 7855 sources classified as BL Lacs, FSRQs, or mixed candidate blazars; 1295 of these sources can be spatially re-associated as confirmed blazars. We describe the properties of the final catalog of WISE blazar-like radio-loud sources and consider possible contaminants. Finally, we discuss why this large catalog of candidate γ-ray emitting blazars represents a new and useful resource to address the problem of finding low-energy counterparts to currently unidentified high-energy sources.

  1. On the origin of the soft photons of the high synchrotron peaked blazar : PKS 1424+240

    NASA Astrophysics Data System (ADS)

    Kang, Shi-Ju; Zheng, Yong-Gang; Wu, Qingwen; Chen, Liang

    2016-06-01

    PKS 1424+240 is a distant very high energy gamma-ray BL Lac object with redshift z = 0.601. It was found that pure synchrotron self-Compton (SSC) process normally need extreme input parameters (e.g., very low magnetic field intensity and extraordinarily large Doppler factor) to explain its multi-wavelength spectral energy distributions (SEDs). To avoid the extreme model parameters, different models have been proposed (e.g., two-zone SSC model or lepto-hadronic model). In this work, we employ the traditional one-zone leptonic model after including a weak external Compton component to re-explore the simultaneous multi-wavelength SEDs of PKS 1424+240 in both high (2009) and low (2013) states. We find that the input parameters of magnetic field and Doppler factor are roughly consistent with those of other BL Lacs if a weak external photon field from either broad line region (BLR) or the dust torus. However, the required energy density of seed photons from BLR or torus is about 3 orders of magnitude less than that constrained in luminous quasars (e.g., flat-spectrum radio quasars, FSRQs). This result suggests that the BLR/torus in BL Lacs is much weaker than that of luminous FSRQs (but not fully disappear), and the inverse-Compton of external photons from BLR/torus may still play a role even in high synchrotron peaked blazars.

  2. Star Formation and AGN Activity in Galaxy Clusters from z=1-2: a Multi-Wavelength Analysis Featuring Herschel/PACS

    NASA Astrophysics Data System (ADS)

    Alberts, Stacey; Pope, Alexandra; Brodwin, Mark; Chung, Sun Mi; Cybulski, Ryan; Dey, Arjun; Eisenhardt, Peter R. M.; Galametz, Audrey; Gonzalez, Anthony H.; Jannuzi, Buell T.; Stanford, S. Adam; Snyder, Gregory F.; Stern, Daniel; Zeimann, Gregory R.

    2016-07-01

    We present a detailed, multi-wavelength study of star formation (SF) and active galactic nucleus (AGN) activity in 11 near-infrared (IR) selected, spectroscopically confirmed massive (≳1014 M ⊙) galaxy clusters at 1 < z < 1.75. Using new deep Herschel/PACS imaging, we characterize the optical to far-IR spectral energy distributions (SEDs) for IR-luminous cluster galaxies, finding that they can, on average, be well described by field galaxy templates. Identification and decomposition of AGNs through SED fittings allows us to include the contribution to cluster SF from AGN host galaxies. We quantify the star-forming fraction, dust-obscured SF rates (SFRs) and specific SFRs for cluster galaxies as a function of cluster-centric radius and redshift. In good agreement with previous studies, we find that SF in cluster galaxies at z ≳ 1.4 is largely consistent with field galaxies at similar epochs, indicating an era before significant quenching in the cluster cores (r < 0.5 Mpc). This is followed by a transition to lower SF activity as environmental quenching dominates by z ∼ 1. Enhanced SFRs are found in lower mass (10.1\\lt {log} {M}\\star /{M}ȯ \\lt 10.8) cluster galaxies. We find significant variation in SF from cluster to cluster within our uniformly selected sample, indicating that caution should be taken when evaluating individual clusters. We examine AGNs in clusters from z = 0.5–2, finding an excess AGN fraction at z ≳ 1, suggesting environmental triggering of AGNs during this epoch. We argue that our results—a transition from field-like to quenched SF, enhanced SF in lower mass galaxies in the cluster cores, and excess AGNs—are consistent with a co-evolution between SF and AGNs in clusters and an increased merger rate in massive halos at high redshift.

  3. Variability-Based Identifications of Blazar Candidates

    NASA Astrophysics Data System (ADS)

    Morton, Tim; Djorgovski, S.; Glikman, E.; Mahabal, A.; Nugent, P.

    2009-01-01

    We present initial results of a study exploring the feasibility of blazar identification by optical variability alone. Using multi-epoch data from the Palomar-Quest survey, supplemented by the data from the JPL NEAT team processed at the LBNL Nearby Supernova Factory, we investigate the optical variability in the fields of a sample of WMAP point sources, all of which we assume to be blazars. Most of these sources have previously reported radio counterparts. In 10 arcmin fields around each of these objects, we find that in about half the cases, these purported WMAP point source IDs are the most variable objects. We suggest that IDs with low variability may be mis-identifications, and propose several alternate IDs selected on the basis of higher variability, which will be targets for future spectroscopic study. We also present potential IDs for previously unidentified WMAP sources. Understanding the variability of high-frequency radio sources will be important for the interpretation of the cosmological CMBR measurements at high angular frequencies. Moreover, since the positional uncertainties of WMAP sources are similar to those expected for the Fermi Gamma-Ray Space Telescope, we conclude that optical variability selection will be a useful tool in correctly identifying optical counterparts to previously unknown Fermi point sources.

  4. Blazar Astronomy above 50 GeV

    NASA Astrophysics Data System (ADS)

    Smith, D. A.

    This contribution is dedicated to the memory of Chaman L. Bhat, an atmospheric Cherenkov pioneer and a leader of the Indian gamma-ray community, who died in a road accident on Mt. Abu on December 17, just after the workshop. While few blazars have been detected beyond EGRET energies, these extreme cases may be the ones that 'make or break' some models describing blazars in particular, and therefore AGNs in general. This paper first reviews the status of the various atmospheric Cherenkov gamma-ray telescopes. We then describe the most recent results from these instruments, paying particular attention to the recent detection of 1ES 1426+428 by the Whipple, CAT, and HEGRA imagers. We illustrate the dilemma of target selection using the example of W Com. We then discuss the consequences of the first measurements of Mrk 421 below 100 GeV by the solar heliostat arrays CELESTE and STACEE. This first foray into the energy range linking EGRET with the current imagers requires us to start using functional forms for the spectral energy distributions that are more physical than the simple power laws (or parabolas) used up to now to describe the imager or satellite results. We can hope that HESS, followed by MAGIC and VERITAS, as well as CELESTE and STACEE, will make this a recurring problem in 2002 and 2003.

  5. A New Relativistic Jet Model of Blazars

    NASA Astrophysics Data System (ADS)

    Webb, James; Benitez, Erika; Howard, Emily

    1998-11-01

    The subclass of Active galaxies called Blazars encompass the most intrinsically luminous and rapidly variable sources known to astrophysicists. Attempts to model these sources has largely been frustrated due in part to observational difficulties, but also due to the lack of theoretical models capable of explaining the different characteristics of the observed sources. Leading candidate models all incorporate a massive, rotating black hole which is accreting galactic material, with some of this material being ejected out the ratational axis of the hole in the form of relativistically expanding jets. These jets are thought to emit energy via the synchrotron process across the entire spectrum from radio frequences all the way through the GEV (sometimes TEV) gamma-ray frequencies. Attempts to model these sources with single relativistic jets has proven difficult. We present a new model which features concentric interacting jets that do a much better job of explaining the types of Blazars we observe. We also discuss ways of testing this new model against multifreuqency observations.

  6. X-RAY AND GAMMA-RAY POLARIZATION IN LEPTONIC AND HADRONIC JET MODELS OF BLAZARS

    SciTech Connect

    Zhang, H.; Boettcher, M.

    2013-09-01

    We present a theoretical analysis of the expected X-ray and {gamma}-ray polarization signatures resulting from synchrotron self-Compton emission in leptonic models compared to the polarization signatures from proton synchrotron and cascade synchrotron emission in hadronic models for blazars. Source parameters resulting from detailed spectral-energy-distribution modeling are used to calculate photon-energy-dependent upper limits on the degree of polarization, assuming a perfectly organized mono-directional magnetic field. In low-synchrotron-peaked blazars, hadronic models exhibit substantially higher maximum degrees of X-ray and gamma-ray polarization than leptonic models, which may be within reach of existing X-ray and {gamma}-ray polarimeters. In high-synchrotron-peaked blazars (with electron-synchrotron-dominated X-ray emission), leptonic and hadronic models predict the same degree of X-ray polarization but substantially higher maximum {gamma}-ray polarization in hadronic models than leptonic ones. These predictions are particularly relevant in view of the new generation of balloon-borne X-ray polarimeters (and possibly GEMS, if revived), and the ability of Fermi-LAT to measure {gamma}-ray polarization at <200 MeV. We suggest observational strategies combining optical, X-ray, and {gamma}-ray polarimetry to determine the degree of ordering of the magnetic field and to distinguish between leptonic and hadronic high-energy emissions.

  7. Multi-frequency, multi-messenger astrophysics with blazars at ASDC and BSDC

    NASA Astrophysics Data System (ADS)

    Giommi, Paolo

    2015-12-01

    In this contribution I discuss the impact that blazars are having on today's multi-frequency and time-domain astrophysics, as well as how they are contributing to the opening of the era of multi-messenger astronomy. In this context I report some preliminary results from a systematic spectral and timing analysis carried out at ASDC on a very large number of X-ray observations of blazars. I also describe some of the on-going activities dedicated to the set up a new research oriented data center within ICRANet, called the Brazilian Science Data Center or BSDC, capitalising on the extensive experience on scientific data management of the ASDC, on the theoretical astrophysics background of ICRANet, and on local specific expertise. Both the ASDC and BSDC are actively accumulating "science ready" data products on blazars, which will be made available through the ASDC "SED builder" tool (https://tools.asdc.asi.it/SED) and by means of interactive tables reachable at the web sites of both centers.

  8. MOJAVE: Monitoring of Jets in Active Galactic Nuclei with VLBA Experiments. VI. Kinematics Analysis of a Complete Sample of Blazar Jets

    NASA Astrophysics Data System (ADS)

    Lister, M. L.; Cohen, M. H.; Homan, D. C.; Kadler, M.; Kellermann, K. I.; Kovalev, Y. Y.; Ros, E.; Savolainen, T.; Zensus, J. A.

    2009-12-01

    We discuss the jet kinematics of a complete flux-density-limited sample of 135 radio-loud active galactic nuclei (AGNs) resulting from a 13 year program to investigate the structure and evolution of parsec-scale jet phenomena. Our analysis is based on new 2 cm Very Long Baseline Array (VLBA) images obtained between 2002 and 2007, but includes our previously published observations made at the same wavelength, and is supplemented by VLBA archive data. In all, we have used 2424 images spanning the years 1994-2007 to study and determine the motions of 526 separate jet features in 127 jets. The data quality and temporal coverage (a median of 15 epochs per source) of this complete AGN jet sample represent a significant advance over previous kinematics surveys. In all but five AGNs, the jets appear one-sided, most likely the result of differential Doppler boosting. In general, the observed motions are directed along the jet ridge line, outward from the optically thick core feature. We directly observe changes in speed and/or direction in one third of the well-sampled jet components in our survey. While there is some spread in the apparent speeds of separate features within an individual jet, the dispersion is about three times smaller than the overall dispersion of speeds among all jets. This supports the idea that there is a characteristic flow that describes each jet, which we have characterized by the fastest observed component speed. The observed maximum speed distribution is peaked at ~10c, with a tail that extends out to ~50c. This requires a distribution of intrinsic Lorentz factors in the parent population that range up to ~50. We also note the presence of some rare low-pattern speeds or even stationary features in otherwise rapidly flowing jets that may be the result of standing re-collimation shocks, and/or a complex geometry and highly favorable Doppler factor.

  9. A Multiwavelength View of Isolated Galaxies

    NASA Astrophysics Data System (ADS)

    Verdes-Montenegro, L.

    2014-03-01

    In the last few years interest in isolated galaxies has been renewed within a context regarding secular evolution. This adds to their value as a control sample for environmental studies of galaxies. This presentation will review important results from recent studies of isolated galaxies. I will emphasize work involving statistically significant samples of isolated galaxies culminating with refinement of the CIG in the AMIGA program. The AMIGA project (Analysis of the interstellar Medium of Isolated Galaxies, http://amiga.iaa.es) has identified a significant sample of the most isolated (Tcc(nearest-neighbor) ˜ 2-3Gyr) galaxies in the local Universe and revealed that they have different properties than galaxies in richer environments. Our analysis of a multiwavelength database includes quantification of degree of isolation, morphologies, as well as FIR and radio line/continuum properties. Properties usually regarded as susceptible to interaction enhancement show lower averages in AMIGA-lower than any galaxy sample yet identified. We find lower MIR/ FIR measures, low levels of radio continuum emission, no radio excess above the radio-FIR correlation, a small number of AGN, and lower molecular gas content. The late-type spiral majority in our sample show very small bulge/total ratios (largely < 0.1) and Sersic indices consistent with an absence of classical bulges. They have redder g-r colors and lower color dispersion for AMIGA subtypes and larger disks, and present the narrowest (Gaussian) distribution of HI profile asymmetries of any sample yet studied.

  10. Catching blazars in the act exlamation GLAST triggers for TeV observation of blazars

    SciTech Connect

    Behera, Bagmeet; Wagner, Stefan J.

    2008-12-24

    The double humped SED (Spectral Energy Distribution) of blazars, and their flaring phenomena can be explained by various leptonic and hadronic models. However, accurate modeling of the high frequency component and clear identification of the correct emission mechanism would require simultaneous measurements in both the MeV-GeV band and the TeV band. Due to the differences in the sensitivity and the field of view of the instruments required to do these measurements, it is essential to identify active states of blazars likely to be detected with TeV instruments.Using a reasonable intergalactic attenuation model, various extrapolations of the EGRET spectra, as a proxy for GLAST (Gamma-ray Large Area Space Telescope) measurements, are made into TeV energies for selecting EGRET blazars expected to be VHE-bright. Furthermore, estimates of the threshold fluxes at GLAST energies are provided, at which sources are expected to be detectable at TeV energies, with Cherenkov telescopes like HESS, MAGIC or VERITAS.

  11. Suzaku Observations of Extreme MeV Blazar Swift J0746.3+2548

    SciTech Connect

    Watanabe, Shin; Sato, Rie; Takahashi, Tadayuki; Kataoka, Jun; Madejski, Greg; Sikora, Marek; Tavecchio, Fabrizio; Sambruna, Rita; Romani, Roger; Edwards, Philip G.; Pursimo, Tapio

    2008-12-01

    We report the Suzaku observations of the high luminosity blazar SWIFT J0746.3+2548 (J0746) conducted in November 2005. This object, with z = 2.979, is the highest redshift source observed in the Suzaku Guaranteed Time Observer (GTO) period, is likely to show high gamma-ray flux peaking in the MeV range. As a result of the good photon statistics and high signal-to-noise ratio spectrum, the Suzaku observation clearly confirms that J0746 has an extremely hard spectrum in the energy range of 0.3-24 keV, which is well represented by a single power-law with a photon index of {Lambda}{sub ph} {approx_equal} 1.17 and Galactic absorption. The multiwavelength spectral energy distribution of J0746 shows two continuum components, and is well modeled assuming that the high-energy spectral component results from Comptonization of the broad-line region photons. In this paper we search for the bulk Compton spectral features predicted to be produced in the soft X-ray band by scattering external optical/UV photons by cold electrons in a relativistic jet. We discuss and provide constraints on the pair content resulting from the apparent absence of such features.

  12. 3C454.3 Revelas the Structure and Physics of its 'Blazar Zone'

    SciTech Connect

    Sikora, M.; Moderski, R.; Madejski, G.M.

    2007-11-28

    Recent multi-wavelength observations of 3C454.3, in particular during its giant outburst in 2005, put severe constraints on the location of the 'blazar zone', its dissipative nature, and high energy radiation mechanisms. As the optical, X-ray, and millimeter light-curves indicate, significant fraction of the jet energy must be released in the vicinity of the millimeter-photosphere, i.e. at distances where, due to the lateral expansion, the jet becomes transparent at millimeter wavelengths. We conclude that this region is located at {approx} 10 parsecs, the distance coinciding with the location of the hot dust region. This location is consistent with the high amplitude variations observed on {approx} 10 day time scale, provided the Lorentz factor of a jet is {Gamma}{sub j} {approx} 20. We argue that dissipation is driven by reconfinement shock and demonstrate that X-rays and {gamma}-rays are likely to be produced via inverse Compton scattering of near/mid IR photons emitted by the hot dust. We also infer that the largest gamma-to-synchrotron luminosity ratio ever recorded in this object - having taken place during its lowest luminosity states - can be simply due to weaker magnetic fields carried by a less powerful jet.

  13. Connection of Very High Energy Gamma-ray Flares in Blazars to Activity at Lower Frequencies

    NASA Astrophysics Data System (ADS)

    Marscher, Alan P.; Jorstad, Svetlana G.

    2016-04-01

    The author will briefly review the results of multi-wavelength observations of blazars that emit very high-energy (VHE) gamma rays. The VHE gamma-ray emission is generally episodic, including flares that are often very short-lived. While many of these flares have counterparts only at X-ray energies, or no counterparts at all, some events are seen also at optical wavelengths, and a number are associated with the passage of new superluminal knots passing through the core in mm-wave VLBA images. Two explanations for the short-term VHE flares in the relativistic jets are supersonic turbulence and ultra-fast plasma jets resulting from magnetic reconnections. Observations of frequency-dependent linear polarization during flares can potentially decide between these models. VLBA images can help to locate VHE events that are seen at millimeter wavelengths. In some cases, the flares take place near the parsec-scale core, while in others they occur closer to the black hole.This research is supported in part by NASA through Swift Guest Investigator grants NNX15AR45G and NNX15AR34G.

  14. Blazar AO 0235+164 brightens in optical

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Borman, G. A.; Jorstad, S. G.

    2014-08-01

    We perform optical photometric and polarimetric monitoring of selected gamma-ray blazars using 0.7-m AZT-8 telescope (Crimean Obs.,, Russia), LX-200 0.4-m telescope (St.Petersburg Univ., Russia) (see http://vo.astro.spbu.ru/program ) and 1.8-m Perkins telescope (Lowell Obs., AZ, USA) (http://www.bu.edu/blazars/VLBAproject.html ), partly in the frames of WEBT/GASP project.

  15. Time Delays of Blazar Flares Observed at Different Wavebands

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.

    2000-01-01

    Correlated variability at different frequencies can probe the structure and physics of the jet of a blazar on size scales much smaller than can be resolved by telescopes and interferometers. I discuss some observations of frequency dependent time lags and how these place constraints on models for the nonthermal emission in blazars. The time lags can be either positive (high frequency variations leading those at lower frequencies) or negative, while simultaneous flares are also possible.

  16. Mass, shape and thermal properties of Abell 1689 using a multiwavelength X-ray, lensing and Sunyaev-Zel'dovich analysis

    NASA Astrophysics Data System (ADS)

    Sereno, Mauro; Ettori, Stefano; Umetsu, Keiichi; Baldi, Alessandro

    2013-01-01

    Knowledge of the mass and concentration of galaxy clusters is crucial for an understanding of their formation and evolution. Unbiased estimates require an understanding of the shape and orientation of the halo as well as its equilibrium status. We propose a novel method to determine the intrinsic properties of galaxy clusters from a multiwavelength data set, spanning from X-ray spectroscopic and photometric data to gravitational lensing to the Sunyaev-Zel'dovich effect. The method relies on two non-informative geometrical assumptions: the distributions of total matter or gas are approximately ellipsoidal and co-aligned; they have different, constant axial ratios but share the same degree of triaxiality. Weak and strong lensing probe the features of the total mass distribution in the plane of the sky. X-ray data measure the size and orientation of the gas in the plane of the sky. Comparison with the Sunyaev-Zel'dovich amplitude fixes the elongation of the gas along the line of sight. These constraints are deprojected as a result of Bayesian inference. The mass distribution is described as a Navarro-Frenk-White halo with arbitrary orientation, and the gas density and temperature are modelled with parametric profiles. We have applied the method to Abell 1689. Independently of the priors, the cluster is massive, M200 = (1.3 ± 0.2) × 1015 M⊙, and overconcentrated, c200 = 8 ± 1, but it is still consistent with theoretical predictions. The total matter is triaxial (minor to major axial ratio ˜0.5 ± 0.1, exploiting priors from N-body simulations) with the major axis nearly orientated along the line of sight. The gas is rounder (minor to major axial ratio ˜0.6 ± 0.1) and deviates from hydrostatic equilibrium. The contribution of non-thermal pressure is ˜20-50 per cent in the inner regions, ≲ 300 kpc, and ˜25 ± 5 per cent at ˜1.5 Mpc. This picture of A1689 was obtained with a small number of assumptions and in a single framework, suitable for application to a

  17. A Multiwavelength Study of Tycho's Supernova Remnant

    NASA Astrophysics Data System (ADS)

    Petre, Robert

    The remnant of the supernova of 1572 A.D., now known as Tycho's Supernova Remnant (SNR), is one of the most well studied SNRs in existence, having been observed with telescopes from radio waves to gamma-rays. We propose a multi-wavelength study of this remnant, with particular focus on archival data in the infrared from Spitzer, WISE, and Herschel, and in gamma-rays from Fermi. The IR data is of extremely high-quality, and will allow us to answer or further constrain several mysteries regarding Tycho, known to be the remnant of a Type Ia supernova. Is the remnant a source of particle acceleration producing cosmic-rays in excess of 10^15 ev? What is the source of the gamma-ray emission seen at both GeV and TeV energies? What is the nature of the medium surrounding the remnant, into which it is currently expanding at over 4000 km/s? Has any dust formed in the iron-rich ejected material from the supernova? The answers to all of these questions will require a multi-wavelength approach, and we will supplement the IR and gamma-ray data here with archival X-ray data from both Chandra and XMM- Newton. In young SNRs like Tycho, IR and X-ray emission is inherently connected, since the hot ions and electrons that give rise to the thermal X-ray emission also heat (and destroy) dust grains in the post-shock gas. Infrared spectroscopy is a highly sensitive function of gas density, and provides a more powerful diagnostic tool for this parameter than X-rays alone do. This post-shock density is a crucial parameter for both particle acceleration and gamma-ray emission models, and the IR data will allow us to measure this density at any point in the remnant. We will explore the relationship between dust and gas in the immediate post-shock region. Because the blast wave is encountering the ambient Galactic ISM, this will provide strong constraints on the dust composition and dust-to-gas mass ratio in the general ISM. At all wavelengths, Tycho is a wealth of information, and by

  18. Multiwavelength Shack-Hartmann aberrometer

    NASA Astrophysics Data System (ADS)

    Jain, Prateek

    Measurement of higher order optical aberrations in the human eye has become important and common place now days, particularly in the advent of custom Lasik surgery and adaptive optics. The most widely used instrument in the industry and clinics is the Shack-Hartmann Aberrometer that utilizes the Shack-Hartmann sensor to measure the aberrations of the eye. The standard SH aberrometer is made of a chin rest and requires the subject to look at the target with one eye and measures the aberrations at an infrared wavelength which is generally 780 nm. This research work adds two improvements to the standard instrument. These two new SH aberrometers have been built and tested on Human subjects. The first modification is to make the aberrometer portable and unobtrusive so that it can be hand held and the subject is allowed to look at the target with both eyes. This instrument is called the Unobtrusive SH Aberrometer (USHA). The second modification is to measure the aberrations at three visible wavelengths spanning the visible spectrum so as to not only measure the aberrations over the visible spectrum but also measure the chromatic aberration. This instrument is called the Multiwavelength SH Aberrometer (MSHA). This instrument is probably a first of its kind, capable measuring the in vivo chromatic aberration in a single image.

  19. Multiwavelength pyrometry for nongray bodies

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1992-01-01

    A multiwavelength technique was developed and applied to measure the temperatures of nongray surfaces. The instruments required are a spectral radiometer, a dedicated auxiliary radiation source, and a computer. In general, three radiation spectra are recorded: (1) spectrum S sub 0 of the auxiliary radiation source; (2) spectrum S sub 1 of the surface-emitted radiation; and (3) spectrum S sub 2, the sum of the radiation of S sub 1 plus the reflected radiation due to the incidence of the auxiliary radiation source on the surface. Subtracting spectrum S sub 1 from spectrum Sub 2 yields the reflection spectrum resulting from the incidence radiation. From these spectra, a quantity z(lambda) is derived and is related to the reflectivity r(lambda) by r(lambda) = z(lambda)/f, where f is a constant. Spectrum S sub 1 is represented mathematically as the product of a wavelength-dependent emissivity obtained from Kirchhoff's law and a Planck function of temperature T. Application of two-variable (lambda and z), nonlinear, least-squares curve-fitting computer software to fit spectrum S sub 1 to this mathematical expression yielded the surface temperature. This technique also measured the spectral reflectivity and emissivity of the surface. Instrumentation necessary to extend measurement to elevated temperatures and in the presence of reflective interference is discussed.

  20. Multiwavelength Monitoring of the Enigmatic Narrow-Line Seyfert 1 PMN J0948 0022 in March-July 2009

    SciTech Connect

    Abdo, A.A.; Ackermann, M.; Ajello, M.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B.M.; Bechtol, K.; Bellazzini, R. Berenji, B.; Bloom, E.D.; Bonamente, E. Borgland, A.W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T.H.; Caliandro, G.A.; /more authors..

    2012-03-29

    Following the recent discovery of {gamma} rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to {gamma} rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to {gamma}-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the {gamma}-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation, and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.

  1. Multiwavelength Monitoring of the Enigmatic Narrow-Line Seyfert 1 PMN J0948+0022 in 2009 March-July

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Axelsson, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Bloom, E. D.; Bonamente, E.; Borgland, A. W.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Burnett, T. H.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Celotti, A.; Chekhtman, A.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Collmar, W.; Conrad, J.; Costamante, L.; Cutini, S.; de Angelis, A.; de Palma, F.; Silva, E. Do Couto e.; Drell, P. S.; Dumora, D.; Farnier, C.; Favuzzi, C.; Fegan, S. J.; Focke, W. B.; Fortin, P.; Foschini, L.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gehrels, N.; Germani, S.; Giglietto, N.; Giordano, F.; Giroletti, M.; Glanzman, T.; Godfrey, G.; Grenier, I. A.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hanabata, Y.; Hays, E.; Hughes, R. E.; Jackson, M. S.; Jóhannesson, G.; Johnson, A. S.; Johnson, W. N.; Kadler, M.; Kamae, T.; Katagiri, H.; Kataoka, J.; Kawai, N.; Kerr, M.; Knödlseder, J.; Kocian, M. L.; Kuss, M.; Lande, J.; Latronico, L.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Madejski, G. M.; Makeev, A.; Max-Moerbeck, W.; Mazziotta, M. N.; McConville, W.; McEnery, J. E.; McGlynn, S.; Meurer, C.; Michelson, P. F.; Mitthumsiri, W.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Nestoras, I.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Omodei, N.; Orlando, E.; Ormes, J. F.; Paneque, D.; Parent, D.; Pavlidou, V.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Readhead, A.; Reimer, O.; Reposeur, T.; Richards, J. L.; Rodriguez, A. Y.; Roth, M.; Ryde, F.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Saz Parkinson, P. M.; Scargle, J. D.; Sgrò, C.; Shaw, M. S.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Tagliaferri, G.; Tajima, H.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Tibolla, O.; Torres, D. F.; Tosti, G.; Tramacere, A.; Uchiyama, Y.; Usher, T. L.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Wehrle, A. E.; Winer, B. L.; Wood, K. S.; Ylinen, T.; Zensus, J. A.; Ziegler, M.; Fermi/LAT Collaboration; Angelakis, E.; Bailyn, C.; Bignall, H.; Blanchard, J.; Bonning, E. W.; Buxton, M.; Canterna, R.; Carramiñana, A.; Carrasco, L.; Colomer, F.; Doi, A.; Ghisellini, G.; Hauser, M.; Hong, X.; Isler, J.; Kino, M.; Kovalev, Y. Y.; Kovalev, Yu. A.; Krichbaum, T. P.; Kutyrev, A.; Lahteenmaki, A.; van Langevelde, H. J.; Lister, M. L.; Macomb, D.; Maraschi, L.; Marchili, N.; Nagai, H.; Paragi, Z.; Phillips, C.; Pushkarev, A. B.; Recillas, E.; Roming, P.; Sekido, M.; Stark, M. A.; Szomoru, A.; Tammi, J.; Tavecchio, F.; Tornikoski, M.; Tzioumis, A. K.; Urry, C. M.; Wagner, S.

    2009-12-01

    Following the recent discovery of γ rays from the radio-loud narrow-line Seyfert 1 galaxy PMN J0948+0022 (z = 0.5846), we started a multiwavelength campaign from radio to γ rays, which was carried out between the end of 2009 March and the beginning of July. The source displayed activity at all the observed wavelengths: a general decreasing trend from optical to γ-ray frequencies was followed by an increase of radio emission after less than two months from the peak of the γ-ray emission. The largest flux change, about a factor of about 4, occurred in the X-ray band. The smallest was at ultraviolet and near-infrared frequencies, where the rate of the detected photons dropped by a factor 1.6-1.9. At optical wavelengths, where the sampling rate was the highest, it was possible to observe day scale variability, with flux variations up to a factor of about 3. The behavior of PMN J0948+0022 observed in this campaign and the calculated power carried out by its jet in the form of protons, electrons, radiation, and magnetic field are quite similar to that of blazars, specifically of flat-spectrum radio quasars. These results confirm the idea that radio-loud narrow-line Seyfert 1 galaxies host relativistic jets with power similar to that of average blazars.

  2. The measurement of hemoglobin oxygen saturation using multiwavelength photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Deng, Zilin; Yang, Xiaoquan; Yu, Lejun; Gong, Hui

    2009-10-01

    Hemoglobin oxygen saturation (SO2) is one of the most critical functional parameters to the metabolism. In this paper, we mainly introduced some initial results of measuring blood oxygen using multi-wavelength photoacoustic microscopy (PAM). In phantom study, we demonstrate the photoacoustic signal amplitude increases linearly with the concentration of red or blue ink. Then the calculated concentration of red ink in double-ink mixtures with PAM has a 5% difference with the result measured with spectrophotometric analysis. In ex vivo experiment, the measured result exhibt 15% difference between the PAM and spectrophotometric analysis. Experiment results suggest that PAM could be used to determine the SO2 quantitatively.

  3. The measurement of hemoglobin oxygen saturation using multiwavelength photoacoustic microscopy

    NASA Astrophysics Data System (ADS)

    Deng, Zilin; Yang, Xiaoquan; Yu, Lejun; Gong, Hui

    2010-02-01

    Hemoglobin oxygen saturation (SO2) is one of the most critical functional parameters to the metabolism. In this paper, we mainly introduced some initial results of measuring blood oxygen using multi-wavelength photoacoustic microscopy (PAM). In phantom study, we demonstrate the photoacoustic signal amplitude increases linearly with the concentration of red or blue ink. Then the calculated concentration of red ink in double-ink mixtures with PAM has a 5% difference with the result measured with spectrophotometric analysis. In ex vivo experiment, the measured result exhibt 15% difference between the PAM and spectrophotometric analysis. Experiment results suggest that PAM could be used to determine the SO2 quantitatively.

  4. FORWARD: A toolset for multiwavelength coronal magnetometry

    NASA Astrophysics Data System (ADS)

    Gibson, Sarah; Kucera, Therese; White, Stephen; Dove, James; Fan, Yuhong; Forland, Blake; Rachmeler, Laurel; Downs, Cooper; Reeves, Katharine

    2016-03-01

    Determining the 3D coronal magnetic field is a critical, but extremely difficult problem to solve. Since different types of multiwavelength coronal data probe different aspects of the coronal magnetic field, ideally these data should be used together to validate and constrain specifications of that field. Such a task requires the ability to create observable quantities at a range of wavelengths from a distribution of magnetic field and associated plasma -- i.e., to perform forward calculations. In this paper we describe the capabilities of the FORWARD SolarSoft IDL package, a uniquely comprehensive toolset for coronal magnetometry. FORWARD is a community resource that may be used both to synthesize a broad range of coronal observables, and to access and compare synthetic observables to existing data. It enables forward fitting of specific observations, and helps to build intuition into how the physical properties of coronal magnetic structures translate to observable properties. FORWARD can also be used to generate synthetic test beds from MHD simulations in order to facilitate the development of coronal magnetometric inversion methods, and to prepare for the analysis of future large solar telescope data.

  5. FORWARD: A Toolset for Multiwavelength Coronal Magnetometry

    NASA Technical Reports Server (NTRS)

    Gibson, Sarah E.; Kucera, Therese A.; White, Stephen M.; Dove, James B.; Fan, Yuhong; Forland, Blake C.; Rachmeler, Laurel A.; Downs, Cooper; Reeves, Katharine K.

    2016-01-01

    Determining the 3D coronal magnetic field is a critical, but extremely difficult problem to solve. Since different types of multiwavelength coronal data probe different aspects of the coronal magnetic field, ideally these data should be used together to validate and constrain specifications of that field. Such a task requires the ability to create observable quantities at a range of wavelengths from a distribution of magnetic field and associated plasma i.e., to perform forward calculations. In this paper we describe the capabilities of the FORWARD SolarSoft IDL package, a uniquely comprehensive toolset for coronal magnetometry. FORWARD is a community resource that may be used both to synthesize a broad range of coronal observables, and to access and compare synthetic observables to existing data. It enables forward fitting of specific observations, and helps to build intuition into how the physical properties of coronal magnetic structures translate to observable properties. FORWARD can also be used to generate synthetic test beds from MHD simulations in order to facilitate the development of coronal magnetometric inversion methods, and to prepare for the analysis of future large solar telescope data.

  6. A sample of weak blazars at milli-arcsecond resolution

    NASA Astrophysics Data System (ADS)

    Mantovani, F.; Bondi, M.; Mack, K.-H.; Alef, W.; Ros, E.; Zensus, J. A.

    2015-05-01

    Aims: We started a follow-up investigation of the "Deep X-ray Radio Blazar Survey" objects with declination >-10 deg to better understand the blazar phenomenon. We undertook a survey with the European Very Long Baseline Interferometry Network at 5 GHz to make the first images of a complete sample of weak blazars, aiming at a follow-up comparison between high- and low-power samples of blazars. Methods: We observed 87 sources with the EVN at 5 GHz during the period October 2009 to May 2013. The observations were correlated at the Max-Planck-Institut für Radioastronomie and at the Joint Institute for VLBI in Europe. The correlator output was analysed using both the AIPS and DIFMAP software packages. Results: All of the sources observed were detected. Point-like sources are found in 39 cases on a milli-arcsecond scale, and 48 show core-jet structure. The total flux density distribution at 5 GHz has a median value ⟨ S ⟩ = 44+23-10 mJy. A total flux density ≤150 mJy is observed in 68 out of 87 sources. Their brightness temperature Tb ranges between 107 K and 1012 K. According to the spectral indices previously obtained with multi-frequency observations, 58 sources show a flat spectral index, and 29 sources show a steep spectrum or a spectrum peaking at a frequency around 1-2 GHz. Adding to the DXRBS objects we observed those already observed with ATCA in the Southern sky, we found that 14 blazars and a Steep Spectrum Radio Quasars, are associated to γ-ray emitters. Conclusions: We found that 56 sources can be considered blazars. We also detected 2 flat spectrum narrow line radio galaxies. About 50% of the blazars associated to a γ-ray object are BL Lacs, confirming that they are more likely detected among blazars γ-emitters. We confirm the correlation found between the source core flux density and the γ-ray photon fluxes down to fainter flux densities. We also found that weak blazars are also weaker γ-ray emitters compared to bright blazars. Twenty

  7. Very-high-energy blazars: A broad(band) perspective

    NASA Astrophysics Data System (ADS)

    Furniss, Amy Kathryn

    Very high energy (VHE; E ≥ 100 GeV) blazars are a type of active galaxy detected above 100 GeV with a jet pointed toward the observer. This work investigates VHE blazars through broadband observations, starting with a description of the VHE-discovery and time-independent modeling of the non-thermal emission from RX J0648.7+1516. Additionally, synchrotron self-Compton models are applied to six non-VHE blazars, with the VHE flux of each blazar being constrained by non-detection during observation by VERITAS. The general lack of physical measurements of model parameters is highlighted and a scheme of supplementary observations involving millimeter carbon monoxide (CO) luminosity and soft X-ray absorption measurements is explored for three VHE blazars. The limited sample supports a possible connection between the existence of CO in the vicinity of the blazar and additional soft X-ray absorption beyond what can be attributed to the Milky Way. RGB J0710+590 and W Comae both lack a significant level of CO and do not require additional absorption for the description of the soft X-ray emission as observed by Swift XRT. 1ES 1959+650, on the other hand, shows a significant level of CO in the vicinity of the blazar and requires additional absorption to describe the soft X-ray emission. The positive detection of CO in the vicinity of 1ES 1959+650 is used as motivation to apply a mirrored emission scenario to broadband variability data. Limits on the redshifts of the two VHE blazars 3C 66A and PKS 1424+240 are derived from HST/COS observations of intervening Lyman absorption. These observations show 3C 66A to reside at a redshift below the tentative z = 0.444 at 99.9% confidence and reveal PKS 1424+240 to be the most distant VHE-detected blazar thus far. The redshift information is paired with VERITAS and Fermi Large Area Telescope gamma-ray observations to probe the density of the extragalactic background light and correct the observed gamma-ray spectra to the intrinsically

  8. Using the Virtual Observatory: multi-instrument, multi-wavelength study of high-energy sources

    NASA Astrophysics Data System (ADS)

    Derrière, S.; Goosmann, R. W.; Bot, C.; Bonnarel, F.

    2014-12-01

    This paper presents a tutorial explaining the use of Virtual Observatory tools in high energy astrophysics. Most of the tools used in this paper were developed at the Strasbourg astronomical Data Center and we show how they can be applied to conduct a multi-instrument, multi-wavelength analysis of sources detected by the High Energy Stereoscopic System and the Fermi Large Area Telescope. The analysis involves queries of different data catalogs, selection and cross-correlation techniques on multi-waveband images, and the construction of high energy color-color plots and multi-wavelength spectra. The tutorial is publicly available on the website of the European Virtual Observatory project.

  9. Multiwavelength Monitoring of Active Galactic Nuclei

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.

    2001-01-01

    By intensive monitoring of AGN variability over a large range in wavelength, we can probe the structure and physics of active galactic nuclei on microarcsecond angular scales. For example, multi-wavelength variability data allow us (a) to establish causal relationships between variations in different wavebands, and thus determine which physical processes are primary and which spectral changes are induced by variations at other wavelengths, and (b) through reverberation mapping of the UV/optical emission lines, to determine the structure and kinematics of the line-emitting region, and thus accurately determine the central masses in AGNs. Multiwavelength monitoring is resource-intensive, and is difficult to implement with general-purpose facilities. As a result, virtually all programs undertaken to date have been either sparsely sampled, or short in duration, or both. The potentially high return on this type of investigation, however, argues for dedicated facilities for multiwavelength monitoring programs.

  10. Multi-wavelength observations of the narrow-line Seyfert 1 galaxy RX J2314.9+2243

    NASA Astrophysics Data System (ADS)

    Komossa, S.; Myserlis, I.; Fuhrmann, L.; Xu, D.; Grupe, D.; Fan, Z.; Yao, S.; Angelakis, E.; Karamanavis, V.; Zensus, J. A.; Yuan, W.

    2016-02-01

    Narrow-line Seyfert 1 (NLS1) galaxies are a sub-class of active galactic nuclei (AGN) with relatively low-mass black holes, accreting near the Eddington rate. A small fraction of them is radio-loud and harbors relativistic jets. As a class, these provide us with new insights into the cause(s) of radio-loudness, the blazar phenomenon at low black hole masses, and the operation of radio-mode feedback. The NLS1 galaxy RXJ2314.9+2243 is remarkable for its multi-wavelength properties. We present new radio observations taken at Effelsberg, and a summary of the recent results from our multi-wavelength study. RXJ2314.9+2243 is radio-loud, luminous in the infrared, has a flat X-ray spectrum and peculiar UV spectrum, and hosts an exceptionally broad and blueshifted [OIII]λ5007 emission line, indicating the presence of a strong outflow. RXJ2314.9+2243 likely represents an extreme case of AGN induced feedback in the local universe.

  11. Simultaneous Multiwavelength Monitoring of 3C66A

    NASA Technical Reports Server (NTRS)

    Boettcher, M.

    2004-01-01

    The radio-selected BL Lac object 3C66A was the target of an intensive multiwavelength campaign from Sept. 2003 through Feb. 2004. It was monitored by the Whole Earth Blazar Telescope (WEBT) collaboration, in tandem with 20 X-ray monitoring observations by the Rossi X-Ray Timing Explorer (RXTE), VHE gamma-ray observations by STACEE and VERITAS, and long-term monitoring at radio frequencies. In addition. 9 observations using the VLBA are being carried out during the campaign and throughout the year 2004 to follow possible structural changes of the source. 21 pointings with RXTE during the period Sept. 15 - Dec. 27, 2003. All collected data have been fully analyzed, and first results have already been published at the 8th HEAD Meeting in New Orleans, LA, in Sept. 2004, and will also be presented at the 205th AAS Meeting in San Diego, CA, in Jan. 2005. A first Journal paper, to be submitted to the Astrophysical Journal, is currently in preparation, and we plan to have it ready for submission in January 2005. A gradual brightening of the source over the course of the campaign was observed at all optical frequencies, culminating in a very bright flare at the end of January 2004. Optical light curves indicate intraday microvariability on time scales down to about 1.3 hours. No significant color-magnitude correlation for the entire data set was evident, but there is a slight indication of a gradual spectral softening in the optical over the entire duration of multi-day outbursts (in both the rising and decaying phase). The X-ray spectrum is consistent with a power-law with a photon spectral index of approx. 2.1, indicating that the RXTE energy band might be located right at the intersection of the synchrotron and the high-energy emission components. No significant flux or spectral variability at X-ray energies was detected, though there seems to be a trend of very modest brightening in tandem with the optical flux. The first 4 VLBA epochs indicate a rather smooth jet with

  12. Unidentified Gamma-Ray Sources: Hunting Gamma-Ray Blazars

    SciTech Connect

    Massaro, F.; D'Abrusco, R.; Tosti, G.; Ajello, M.; Gasparrini, A.Paggi.D.

    2012-04-02

    One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of the unidentified {gamma}-ray sources (UGSs). Despite the large improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one third of the Fermi-detected objects are still not associated to low energy counterparts. Recently, using the Wide-field Infrared Survey Explorer (WISE) survey, we discovered that blazars, the rarest class of Active Galactic Nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated to the UGS sample of the second Fermi {gamma}-ray catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated to {gamma}-ray sources in the 2FGL catalog.

  13. UNIDENTIFIED {gamma}-RAY SOURCES: HUNTING {gamma}-RAY BLAZARS

    SciTech Connect

    Massaro, F.; Ajello, M.; D'Abrusco, R.; Paggi, A.; Tosti, G.; Gasparrini, D.

    2012-06-10

    One of the main scientific objectives of the ongoing Fermi mission is unveiling the nature of unidentified {gamma}-ray sources (UGSs). Despite the major improvements of Fermi in the localization of {gamma}-ray sources with respect to the past {gamma}-ray missions, about one-third of the Fermi-detected objects are still not associated with low-energy counterparts. Recently, using the Wide-field Infrared Survey Explorer survey, we discovered that blazars, the rarest class of active galactic nuclei and the largest population of {gamma}-ray sources, can be recognized and separated from other extragalactic sources on the basis of their infrared (IR) colors. Based on this result, we designed an association method for the {gamma}-ray sources to recognize if there is a blazar candidate within the positional uncertainty region of a generic {gamma}-ray source. With this new IR diagnostic tool, we searched for {gamma}-ray blazar candidates associated with the UGS sample of the second Fermi {gamma}-ray LAT catalog (2FGL). We found that our method associates at least one {gamma}-ray blazar candidate as a counterpart to each of 156 out of 313 UGSs analyzed. These new low-energy candidates have the same IR properties as the blazars associated with {gamma}-ray sources in the 2FGL catalog.

  14. Multiwavelength studies of Saturn's rings

    NASA Astrophysics Data System (ADS)

    Spilker, L. J.; Deau, E.; Filacchione, G.; Morishima, R.; Hedman, M. M.; Nicholson, D.; Colwell, J. E.

    2013-12-01

    Modeling the changes in brightness, color, temperature and spectral parameters, significant progress can be made in understanding the character of Saturn's ring particles and their regoliths with changing viewing geometry. We are studying Saturn's rings over a wide range of wavelengths, from ultraviolet through the thermal infrared. Data from Cassini's Composite Infrared Spectrometer (CIRS), Visual and Infrared Mapping Spectrometer (VIMS), Imaging Science Subsystem (ISS) and Ultraviolet Imaging Spectrograph (UVIS) are jointly being studied using scans of the lit and unlit main rings (A, B, C and Cassini Division) at multiple geometries and solar elevations. Phase curves are also being generated for different ring regions. Using multi-wavelength data sets allows us to test different thermal models by combining effects of particle albedo, regolith grain size and surface roughness with thermal emissivity and inertia, and particle spin rate and spin axis orientation. With the high spatial resolution of the Cassini data it is now possible to analyze these effects at smaller spatial scales and characterize regions such as the C ring plateaus and ringlets, where albedo differences may be present. The CIRS temperature and ISS color variations are confined primarily to phase angle over a range of solar elevations with only small differences from changing spacecraft elevation. Color and temperature dependence with varying solar elevation angle are also observed. Brightness dependence with changing solar elevation angle and phase angle is observed with UVIS. VIMS observations show that IR water ice absorption band depths are a very weak function of phase angle, out to ~140 deg phase, suggesting that interparticle light scattering is relatively unimportant except at very high phase angles. These results imply that the individual properties of the ring particles may play a larger role than the collective properties of the rings, in particular at visible wavelengths. The

  15. Optical intraday variability studies of 10 low energy peaked blazars

    NASA Astrophysics Data System (ADS)

    Rani, Bindu; Gupta, Alok C.; Joshi, U. C.; Ganesh, S.; Wiita, Paul J.

    2011-05-01

    We have carried out optical (R band) intraday variability (IDV) monitoring of a sample of 10 bright low energy peaked blazars (LBLs). 40 photometric observations, of an average of ˜4 h each, were made between 2008 September and 2009 June using two telescopes in India. Measurements with good signal-to-noise ratios were typically obtained within 1-3 min, allowing the detection of weak, fast variations using N-star differential photometry. We employed both structure function and discrete correlation function analysis methods to estimate any dominant time-scales of variability and found that in most of the cases any such time-scales were longer than the duration of the observation. The calculated duty cycle of IDV in LBLs during our observing run is ˜52 per cent, which is low compared to many earlier studies; however, the relatively short periods for which each source was observed can probably explain this difference. We briefly discuss possible emission mechanisms for the observed variability.

  16. Blazars and gamma-ray cosmology: recent and prospective results

    NASA Astrophysics Data System (ADS)

    Biteau, Jonathan; Williams, David A.

    2016-01-01

    Blazars are dazzling gamma-ray beacons shedding light on some of the darkest mysteries of modern-day astroparticle physics. Some of these mysteries include the light content of the universe, including the UV-IR background, the emission of first stars and of organic molecules; large-scale magnetic fields and their potential primordial origin; spacetime structure, with the potential for Lorentz-invariance violations near the Planck scale; and the search for new interaction channels with photons, e.g. in the form of axion-like particles. These crucial scientific topics can be studied through the signatures of billion-year propagation of GeV-TeV gamma rays that reach Earth from astrophysical sources. We discuss how spectral imprints in data from ground-based and satellite experiments are beginning to answer some of the fundamental questions of gamma-ray cosmology. Recent results, obtained with increased datasets and advanced analysis techniques, are opening the path for future observatories. We examine the areas that remain to be explored, in particular by the proposed Cherenkov Telescope Array, CTA.

  17. Constraining the location of gamma-ray flares in luminous blazars

    SciTech Connect

    Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek

    2014-07-10

    Locating the gamma-ray emission sites in blazar jets is a long standing and highly controversial issue. We jointly investigate several constraints on the distance scale r and Lorentz factor Γ of the gamma-ray emitting regions in luminous blazars (primarily flat spectrum radio quasars). Working in the framework of one-zone external radiation Comptonization models, we perform a parameter space study for several representative cases of actual gamma-ray flares in their multiwavelength context. We find a particularly useful combination of three constraints: from an upper limit on the collimation parameter Γθ ≲ 1, from an upper limit on the synchrotron self-Compton (SSC) luminosity L{sub SSC} ≲ L{sub X}, and from an upper limit on the efficient cooling photon energy E{sub cool,obs} ≲ 100 MeV. These three constraints are particularly strong for sources with low accretion disk luminosity L{sub d}. The commonly used intrinsic pair-production opacity constraint on Γ is usually much weaker than the SSC constraint. The SSC and cooling constraints provide a robust lower limit on the collimation parameter Γθ ≳ 0.1-0.7. Typical values of r corresponding to moderate values of Γ ∼ 20 are in the range 0.1-1 pc, and are determined primarily by the observed variability timescale t{sub var,obs}. Alternative scenarios motivated by the observed gamma-ray/millimeter connection, in which gamma-ray flares of t{sub var,obs} ∼ a few days are located at r ∼ 10 pc, are in conflict with both the SSC and cooling constraints. Moreover, we use a simple light travel time argument to point out that the gamma-ray/millimeter connection does not provide a significant constraint on the location of gamma-ray flares. We argue that spine-sheath models of the jet structure do not offer a plausible alternative to external radiation fields at large distances; however, an extended broad-line region is an idea worth exploring. We propose that the most definite additional constraint could be

  18. Constraining the Location of Gamma-Ray Flares in Luminous Blazars

    NASA Astrophysics Data System (ADS)

    Nalewajko, Krzysztof; Begelman, Mitchell C.; Sikora, Marek

    2014-07-01

    Locating the gamma-ray emission sites in blazar jets is a long standing and highly controversial issue. We jointly investigate several constraints on the distance scale r and Lorentz factor Γ of the gamma-ray emitting regions in luminous blazars (primarily flat spectrum radio quasars). Working in the framework of one-zone external radiation Comptonization models, we perform a parameter space study for several representative cases of actual gamma-ray flares in their multiwavelength context. We find a particularly useful combination of three constraints: from an upper limit on the collimation parameter Γθ <~ 1, from an upper limit on the synchrotron self-Compton (SSC) luminosity L SSC <~ L X, and from an upper limit on the efficient cooling photon energy E cool, obs <~ 100 MeV. These three constraints are particularly strong for sources with low accretion disk luminosity L d. The commonly used intrinsic pair-production opacity constraint on Γ is usually much weaker than the SSC constraint. The SSC and cooling constraints provide a robust lower limit on the collimation parameter Γθ >~ 0.1-0.7. Typical values of r corresponding to moderate values of Γ ~ 20 are in the range 0.1-1 pc, and are determined primarily by the observed variability timescale t var, obs. Alternative scenarios motivated by the observed gamma-ray/millimeter connection, in which gamma-ray flares of t var, obs ~ a few days are located at r ~ 10 pc, are in conflict with both the SSC and cooling constraints. Moreover, we use a simple light travel time argument to point out that the gamma-ray/millimeter connection does not provide a significant constraint on the location of gamma-ray flares. We argue that spine-sheath models of the jet structure do not offer a plausible alternative to external radiation fields at large distances; however, an extended broad-line region is an idea worth exploring. We propose that the most definite additional constraint could be provided by determination of the

  19. Multiwaveband Variability of Blazars from Turbulent Plasma Passing through a Standing Shock: The Mother of Multi-zone Models

    NASA Astrophysics Data System (ADS)

    Marscher, Alan P.

    2011-09-01

    Multi-wavelength light curves of bright gamma-ray blazars (e.g., 3C 454.3) are compared with the model proposed by Marscher and Jorstad. In this scenario, much of the optical and high-energy radiation in a blazar is emitted near the 43 GHz core of the jet as seen in VLBA images, parsecs from the central engine. The main physical features are a turbulent ambient jet plasma that passes through a standing recollimation shock in the jet. The model allows for short time-scales of optical and gamma-ray variability by restricting the highest-energy electrons radiating at these frequencies to a small fraction of the turbulent cells, perhaps those with a particular orientation of the magnetic field relative to the shock front. Because of this, the volume filling factor at high frequencies is relatively low, while that of the electrons radiating below about 10 THz is near unity. Such a model is consistent with the (1) red-noise power spectra of flux variations, (2) shorter time-scales of variability at higher frequencies, (3) frequency dependence of polarization and its variability, and (4) breaks in the synchrotron spectrum by more than the radiative loss value of 0.5. Simulated light curves are generated by a numerical code that (as of May 2011) includes synchrotron radiation as well as inverse Compton scattering of seed photons from both a dust torus and a Mach disk at the jet axis. The latter source of seed photons produces more pronounced variability in gamma-ray than in optical light curves, as is often observed. More features are expected to be added to the code by the time of the presentation. This research is supported in part by NASA through Fermi grants NNX08AV65G and NNX10AO59G, and by NSF grant AST-0907893.

  20. Very High Energy γ-Rays from the Universe's Middle Age: Detection of the z = 0.940 Blazar PKS 1441+25 with MAGIC

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Chatterjee, A.; Clavero, R.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giammaria, P.; Godinović, N.; González Muñoz, A.; Guberman, D.; Hahn, A.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Hughes, G.; Idec, W.; Kodani, K.; Konno, Y.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Majumdar, P.; Makariev, M.; Mallot, K.; Maneva, G.; Manganaro, M.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Moretti, E.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Satalecka, K.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; MAGIC Collaboration; Ajello, M.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Becerra González, J.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bregeon, J.; Bruel, P.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Chiang, J.; Chiaro, G.; Ciprini, S.; D'Ammando, F.; de Palma, F.; Desiante, R.; Di Venere, L.; Domínguez, A.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Grenier, I. A.; Guiriec, S.; Hays, E.; Hewitt, J. W.; Jogler, T.; Kuss, M.; Larsson, S.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Maldera, S.; Mayer, M.; Mazziotta, M. N.; McEnery, J. E.; Mirabal, N.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Nuss, E.; Ojha, R.; Ohsugi, T.; Omodei, N.; Orlando, E.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Raino, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Sgro, C.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Tajima, H.; Takahashi, H.; Thayer, J. B.; Thompson, D. J.; Troja, E.; Wood, K. S.; Fermi-LAT Collaboration; Balokovic, M.; Berdyugin, A.; Carraminana, A.; Carrasco, L.; Chavushyan, V.; Fallah Ramazani, V.; Feige, M.; Haarto, S.; Haeusner, P.; Hovatta, T.; Kania, J.; Klamt, J.; Lähteenmäki, A.; Leon-Tavares, J.; Lorey, C.; Pacciani, L.; Porras, A.; Recillas, E.; Reinthal, R.; Tornikoski, M.; Wolfert, D.; Zottmann, N.

    2015-12-01

    The flat-spectrum radio quasar PKS 1441+25 at a redshift of z = 0.940 is detected between 40 and 250 GeV with a significance of 25.5σ using the MAGIC telescopes. Together with the gravitationally lensed blazar QSO B0218+357 (z = 0.944), PKS 1441+25 is the most distant very high energy (VHE) blazar detected to date. The observations were triggered by an outburst in 2015 April seen at GeV energies with the Large Area Telescope on board Fermi. Multi-wavelength observations suggest a subdivision of the high state into two distinct flux states. In the band covered by MAGIC, the variability timescale is estimated to be 6.4 ± 1.9 days. Modeling the broadband spectral energy distribution with an external Compton model, the location of the emitting region is understood as originating in the jet outside the broad-line region (BLR) during the period of high activity, while being partially within the BLR during the period of low (typical) activity. The observed VHE spectrum during the highest activity is used to probe the extragalactic background light at an unprecedented distance scale for ground-based gamma-ray astronomy.

  1. Polarization Properties of 24 Fermi-Detected Blazars

    NASA Astrophysics Data System (ADS)

    Linford, Justin; Taylor, G. B.; Schinzel, F. K.; Zavala, R. T.

    2013-01-01

    Gamma-ray emitting blazars have been shown to frequently have significant polarization at radio wavelengths. In early 2012, we obtained Very Long Baseline Array (VLBA) observations of 24 blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. These observations utilized the new 2 gigabit-per-second mode of the VLBA. We observed each source with full polarization at 8.4 GHz, 15 GHz, and 22 GHz with 256 MHz of total bandwidth per polarization. Our sample contains 14 flat-spectrum radio quasars (FSRQs) and 10 BL Lacertae objects (BL Lacs). We analyze the spectral index, rotation measure, and magnetic field structures of these 24 gamma-ray loud blazars.

  2. A spine-sheath model for strong-line blazars

    NASA Astrophysics Data System (ADS)

    Sikora, Marek; Rutkowski, Mieszko; Begelman, Mitchell C.

    2016-04-01

    We have developed a quasi-analytical model for the production of radiation in strong-line blazars, assuming a spine-sheath jet structure. The model allows us to study how the spine and sheath spectral components depend on parameters describing the geometrical and physical structure of `the blazar zone'. We show that typical broad-band spectra of strong-line blazars can be reproduced by assuming the magnetization parameter to be of order unity and reconnection to be the dominant dissipation mechanism. Furthermore, we demonstrate that the spine-sheath model can explain why γ-ray variations are often observed to have much larger amplitudes than the corresponding optical variations. The model is also less demanding of jet power than one-zone models, and can reproduce the basic features of extreme γ-ray events.

  3. A sample of Swift/SDSS faint blazars

    NASA Astrophysics Data System (ADS)

    Fraga, Bernardo; Giommi, Paolo; Turriziani, Sara

    2015-12-01

    We aim here to provide a complete sample of faint (fr ≳ 1 mJy, fx ≳ 10-15 erg cm-2 s-1) blazars and blazar candidates serendipitously discovered in deep Swift images centered on Gamma-ray bursts (GRBs). By stacking all available images, we obtain exposures ranging from 104 to more than a million seconds. Since GRBs are thought to explode randomly across the sky, this set of deep fields can be considered as an unbiased survey of ≈ 12 square degrees of extragalactic sky, with sensitivities reaching a few 10-15 erg cm-2 s-1 in the 0.5-2 keV band. We then derive the x-ray Log N Log S and show that, considering that our sample may be contaminated by sources other than blazars, we are in agreement with previous estimations based on data and simulations.

  4. XMM-Newton observations of blazars in outburst

    NASA Astrophysics Data System (ADS)

    Tagliaferri, Gianpiero

    2006-10-01

    We ask for 4 TOO observations of 50 ks each to observe 4 blazars, conditional to stringent and well defined triggering criteria based on 1) hard or soft X-ray brightening; or 2) TeV brightening; or GeV brightening or 3) optical brightening. With the XMM-Newton observations of blazars in flaring state we will investigate their X-ray spectra evolution over a timescale from minutes to hours. This will provide relevant information on the radiation mechanisms in extragalactic relativistic jets. XMM-Newton TOO prompted by Swift/BAT or INTEGRAL or GLAST or TeV telescope would provide for the first time X-ray observations of flaring blazars activated by very high energy triggers. We will coordinate these observations with a similar Integral program already active.

  5. An innovative blazar classification based on radio jet kinematics

    NASA Astrophysics Data System (ADS)

    Hervet, O.; Boisson, C.; Sol, H.

    2016-07-01

    Context. Blazars are usually classified following their synchrotron peak frequency (νF(ν) scale) as high, intermediate, low frequency peaked BL Lacs (HBLs, IBLs, LBLs), and flat spectrum radio quasars (FSRQs), or, according to their radio morphology at large scale, FR I or FR II. However, the diversity of blazars is such that these classes seem insufficient to chart the specific properties of each source. Aims: We propose to classify a wide sample of blazars following the kinematic features of their radio jets seen in very long baseline interferometry (VLBI). Methods: For this purpose we use public data from the MOJAVE collaboration in which we select a sample of blazars with known redshift and sufficient monitoring to constrain apparent velocities. We selected 161 blazars from a sample of 200 sources. We identify three distinct classes of VLBI jets depending on radio knot kinematics: class I with quasi-stationary knots, class II with knots in relativistic motion from the radio core, and class I/II, intermediate, showing quasi-stationary knots at the jet base and relativistic motions downstream. Results: A notable result is the good overlap of this kinematic classification with the usual spectral classification; class I corresponds to HBLs, class II to FSRQs, and class I/II to IBLs/LBLs. We deepen this study by characterizing the physical parameters of jets from VLBI radio data. Hence we focus on the singular case of the class I/II by the study of the blazar BL Lac itself. Finally we show how the interpretation that radio knots are recollimation shocks is fully appropriate to describe the characteristics of these three classes.

  6. Elevated Optical Luminosity for Gamma-ray Blazar BL Lacertae

    NASA Astrophysics Data System (ADS)

    Furniss, A.; Fumagalli, M.; Hogan, M.; Kaplan, K.; Prochaska, P. X.; Williams, D. A.

    2012-06-01

    We report on the increased optical luminosity of BL Lacertae (RA=22h02m43.29s, dec=42d16m39.98s), a low-frequency-peaked gamma-ray emitting blazar at a redshift of 0.068 (3EG J2202+4225, 2FGL J2202.8+4216). We have collected regular R-band exposures for BL Lacertae as part of a larger optical monitoring program of gamma-ray-bright blazars using the Super-LOTIS (Livermore Optical Transient Imaging System) robotic telescope at the Steward Observatory on Kitt Peak, near Tucson Arizona.

  7. Variability properties and masses of central black hole for blazars

    NASA Astrophysics Data System (ADS)

    Fan, Junhui

    2001-06-01

    In this paper, the compiled long-term optical and infrared measurements of some blazars are used to analyze the variation properties, and the optical data are used to search for periodicity evidence in the lightcurve by means of the Jurkevich technique and the discrete correlation function (DCF) method. The periods are found in the range of 1.5 to 19 years. The short time scales are used to estimate the central black hole masses which are found in the range of (3.8 - 130)×107Msolar for the gamma-ray loud blazars. Some discussions are presented.

  8. The γ-ray emission mechanism for Fermi Blazars

    NASA Astrophysics Data System (ADS)

    Yang, J. H.; Fan, J. H.; Hua, T. X.; Wu, D. X.

    2014-08-01

    Fermi Blazars are characterized mainly by the vast effect that relativistic beaming has on their emission spectra. Fermi-LAT has detected more than 1000 blazars which provide us with a good opportunity to study the emission mechanism. In this paper, adopted the Doppler factor δ γ determined in our previous paper, the γ-ray emission mechanism is discussed using the investigation of dependence of the γ-ray luminosity on the Doppler factor. Our discussions suggest that the γ-ray emission mechanism is SSC for BL Lacs.

  9. From the Blazar Sequence to the Blazar Envelope: Revisiting the Relativistic Jet Dichotomy in Radio-Loud AGN

    NASA Technical Reports Server (NTRS)

    Meyer, Eileen T.; Fossati, Giovanini; Georganopoulos, Markos; Lister, Matthew L.

    2012-01-01

    We revisit the concept of a blazar sequence that relates the synchrotron peak frequency (Vpeak) in blazars with synchrotron peak luminosity (Lpeak, in vLv) using a large sample of radio-loud AGN. We present observational evidence that the blazar sequence is formed from two populations in the synchrotron Vpeak - Lpeak plane, each forming an upper edge to an envelope of progressively misaligned blazars, and connecting to an adjacent group of radio galaxies having jets viewed at much larger angles to the line of sight. When binned by jet kinetic power (Lkin; as measured through a scaling relationship with extended radio power), we find that radio core dominance decreases with decreasing synchrotron Lpeak, revealing that sources in the envelope are generally more misaligned. We find population-based evidence of velocity gradients in jets at low kinetic powers (approximately 10(exp 42) - 10(exp 44.5) erg s(exp -1)), corresponding to FR I radio galaxies and most BL Lacs. These low jet power 'weak jet' sources, thought to exhibit radiatively inefficient accretion, are distinguished from the population of non-decelerating, low synchrotron-peaking (LSP) blazars and FR II radio galaxies ('strong' jets) which are thought to exhibit radiatively efficient accretion. The two-population interpretation explains the apparent contradiction of the existence of highly core-dominated, low-power blazars at both low and high synchrotron peak frequencies, and further implies that most intermediate synchrotron peak (ISP) sources are not intermediate in intrinsic jet power between LSP and high synchrotron-peaking (HSP) sources, but are more misaligned versions of HSP sources with similar jet powers.

  10. FROM THE BLAZAR SEQUENCE TO THE BLAZAR ENVELOPE: REVISITING THE RELATIVISTIC JET DICHOTOMY IN RADIO-LOUD ACTIVE GALACTIC NUCLEI

    SciTech Connect

    Meyer, Eileen T.; Fossati, Giovanni; Georganopoulos, Markos; Lister, Matthew L.

    2011-10-20

    We revisit the concept of a blazar sequence that relates the synchrotron peak frequency ({nu}{sub peak}) in blazars with synchrotron peak luminosity (L{sub peak}, in {nu}L{sub {nu}}) using a large sample of radio-loud active galactic nuclei. We present observational evidence that the blazar sequence is formed from two populations in the synchrotron {nu}{sub peak}-L{sub peak} plane, each forming an upper edge to an envelope of progressively misaligned blazars, and connecting to an adjacent group of radio galaxies having jets viewed at much larger angles to the line of sight. When binned by jet kinetic power (L{sub kin}; as measured through a scaling relationship with extended radio power), we find that radio core dominance decreases with decreasing synchrotron L{sub peak}, revealing that sources in the envelope are generally more misaligned. We find population-based evidence of velocity gradients in jets at low kinetic powers ({approx}10{sup 42}-10{sup 44.5} erg s{sup -1}), corresponding to Fanaroff-Riley (FR) I radio galaxies and most BL Lac objects. These low jet power 'weak-jet' sources, thought to exhibit radiatively inefficient accretion, are distinguished from the population of non-decelerating, low synchrotron-peaking (LSP) blazars and FR II radio galaxies ('strong' jets) which are thought to exhibit radiatively efficient accretion. The two-population interpretation explains the apparent contradiction of the existence of highly core-dominated, low-power blazars at both low and high synchrotron peak frequencies, and further implies that most intermediate synchrotron peak sources are not intermediate in intrinsic jet power between LSP and high synchrotron-peaking (HSP) sources, but are more misaligned versions of HSP sources with similar jet powers.

  11. Rapid optical variability of TeV blazars

    NASA Astrophysics Data System (ADS)

    Gopal-Krishna; Goyal, Arti; Joshi, S.; Karthick, Chrisphin; Sagar, R.; Wiita, Paul J.; Anupama, G. C.; Sahu, D. K.

    2011-09-01

    In this first systematic attempt to characterize the intranight optical variability (INOV) of TeV-detected blazars, we have monitored a well-defined set of nine TeV blazars on total 26 nights during 2004-10. In this R- or V-band-monitoring programme only one blazar was monitored per night and the minimum duration was close to 4 h, the average being 5.3 h per night. Using the CCD for strictly simultaneous photometry of the blazar and nearby reference stars (N-star photometry), an INOV detection threshold of ˜1-2 per cent was achieved in the densely sampled differential light curves derived from our data. We have further expanded the sample by including another 13 TeV blazars, taking advantage of the availability in the literature of INOV data, including those published earlier in our programme. The selection criteria for this set of 13 blazars conform to the basic criteria we had adopted for the first set of nine blazars we have monitored presently. This enlarged, well-defined representative sample of 22 TeV blazars, monitored on a total of 116 nights (including 55 nights newly reported here), has enabled us to arrive at the first estimate of the INOV duty cycle (DC) of TeV-detected blazars. Applying the conservative, but commonly employed, C-test, the INOV DC is found to be 59 per cent, which decreases to 47 per cent if only INOV fractional amplitudes (ψ) above 3 per cent are considered. These observations also permit, for the first time, a comparison of the INOV characteristics of the two major subclasses of TeV-detected BL Lac objects, namely low-peaked BL Lac objects (LBLs) and high-peaked BL Lac objects (HBLs), for which we find the INOV DCs to be ˜63 and 38 per cent, respectively. This demonstrates that the previously recognized INOV differential between LBLs and HBLs persists even when only their TeV-detected subsets are considered. Despite dense sampling, the intranight light curves of the 22 TeV blazars have not revealed even a single feature on time

  12. Unveiling the nature of two unidentified EGRET blazar candidates through spectroscopic observations

    NASA Astrophysics Data System (ADS)

    Nkundabakura, P.; Meintjes, P. J.

    2012-11-01

    Studies using the Energetic Gamma-Ray Experiment Telescope (EGRET) revealed that blazars [flat-spectrum radio quasars (FSRQs) and BL Lac objects] emit most of their luminosity in the high-energy gamma-ray (E > 100 MeV) range. From the 271 sources observed by EGRET, 131 are still unidentified. A systematic search is conducted to identify possible high-energy gamma-ray blazars among the unidentified EGRET population. Based upon multiwavelength emission properties, 13 extragalactic radio sources were selected in the EGRET error boxes for further investigation. From the above-mentioned sample, results of a multiwavelength follow-up of two EGRET sources, 3EG J0821-5814 and 3EG J0706-3837, are presented. These sources are associated with their radio counterparts PKS J0820-5705 and PMN J0710-3850, respectively. Spectroscopic observations utilizing the SOAR/Goodman spectrograph at the Cerro Tololo Inter-American Observatory in Chile reveal a spectrum of PKS J0820-5705 that corresponds to that of a radio-loud active galactic nucleus (FSRQ) with redshift z = 0.06 ± 0.01, while the visibility of wide and narrow emission lines in the spectrum of PMN J0710-3850 resembles that of a low-ionization nuclear emission-line region (LINER) or type 1 Seyfert galaxy at z = 0.129 ± 0.001. The observed Ca II K&H lines depression ratio at 4000 Å showed a shallow depression of 8.8 ± 2.5 per cent for PKS J0820-5705 and 80 ± 1 per cent for PMN J0710-3850, suggesting the presence of a strong non-thermal optical contribution in PKS J0820-5705, which clearly distinguishes its spectrum from that of a radio galaxy. The weaker optical non-thermal contribution for PMN J0710-3850 is in accordance with that expected of a LINER. For PMN J0710-3850 the line flux ratios [O III] λ5007/Hβ < 3 and [N II] λ6583/Hα > 0.6 which are in agreement with the expected ratios of LINERs. However, the absence of [O II] λ3727 implies an anomalously low [O II]/[O III] < 0.5 ratio for a LINER, and agrees more

  13. Science with the ASTRI mini-array for the Cherenkov Telescope Array: blazars and fundamental physics

    NASA Astrophysics Data System (ADS)

    Bonnoli, Giacomo; Tavecchio, Fabrizio; Giuliani, Andrea; Bigongiari, Ciro; Di Pierro, Federico; Stamerra, Antonio; Pareschi, Giovanni; Vercellone, Stefano; ASTRI Collaboration; CTA Consortium

    2016-05-01

    ASTRI (“Astronomia a Specchi con Tecnologia Replicante Italiana”) is a flagship project of the Italian Ministry of Research (MIUR), devoted to the realization, operation and scientific validation of an end-to-end prototype for the Small Size Telescope (SST) envisaged to become part of the Cherenkov Telescope Array (CTA). The ASTRI SST-2M telescope prototype is characterized by a dual mirror, Schwarzschild-Couder optical design and a compact camera based on silicon photo-multipliers. It will be sensitive to multi-TeV very high energy (VHE) gamma rays up to 100 TeV, with a PSF ~ 6’ and a wide (9.6°) unaberrated optical field of view. Right after validation of the design in single-dish observations at the Serra La Nave site (Sicily, Italy) during 2015, the ASTRI collaboration will be able to start deployment, at the final CTA southern site, of the ASTRI mini-array, proposed to constitute the very first CTA precursor. Counting 9 ASTRI SST-2M telescopes, the ASTRI mini-array will overtake current IACT systems in differential sensitivity above 5 TeV, thus allowing unprecedented observations of known and predicted bright TeV emitters in this band, including some extragalactic sources such as extreme high-peaked BL Lacs with hard spectra. We exploited the ASTRI scientific simulator ASTRIsim in order to understand the feasibility of observations tackling blazar and cosmic ray physics, including discrimination of hadronic and leptonic scenarios for the VHE emission from BL Lac relativistic jets and indirect measurements of the intergalactic magnetic field and of the extragalactic background light. We selected favorable targets, outlining observation modes, exposure times, multi-wavelength coverage needed and the results expected. Moreover, the perspectives for observation of effects due to the existence of axion-like particles or to Lorentz invariance violations have been investigated.

  14. Multiwavelength Study of Active Galaxies

    NASA Astrophysics Data System (ADS)

    Singh, Veeresh

    2010-08-01

    Seyfert galaxies are a subclass of active galaxies and are categorized as nearby, low luminosity, radio-quiet Active Galactic Nuclei (AGN) hosted in spiral or lenticular galaxies. Demographically, Seyfert galaxies may account for ~ 10% of the entire population of active galaxies in the nearby universe. Seyfert galaxies are classified mainly into two subclasses named as `type 1' and `type 2' Seyferts, based on the presence and absence of broad permitted emission lines in their optical spectra, respectively. Detection of broad permitted emission lines in some Seyfert type 2s observed in the polarized light laid the foundation of the Seyfert unification scheme, which hypothesizes that Seyfert type 1s and type 2s belong to the same parent population and appear different solely due to the differing orientations of the obscuring material having a torus-like geometry around the AGN (Antonucci and Miller 1985; Antonucci 1993). The primary objective of this thesis work is to examine the validity and limitations of the orientation and obscuration based Seyfert unification scheme using multiwavelength (mainly X-ray and radio) observations. The key issue in testing the Seyfert unification scheme has been acquiring a well defined rigorously selected Seyfert sample. I have argued that the Seyfert samples based on flux limited surveys at optical, IR, UV and X-ray are likely to be biased against obscured and faint sources. In order to test the predictions of Seyfert unification scheme I use a sample based on properties (i.e., cosmological redshift, [OIII] emission line luminosity, absolute bulge magnitude, absolute stellar magnitude of the host galaxy and the Hubble stage of the host galaxy) that are independent to the orientation of the obscuring torus, host galaxy and the AGN axis. Furthermore, two Seyfert subtypes of our sample have matched distributions in the orientation-independent properties and this ensures the intrinsic similarity between two Seyfert subtypes within the

  15. Multiwavelength Challenges in the Fermi Era

    NASA Technical Reports Server (NTRS)

    Thompson, D. J.

    2010-01-01

    The gamma-ray surveys of the sky by AGILE and the Fermi Gamma-ray Space Telescope offer both opportunities and challenges for multiwavelength and multi-messenger studies. Gamma-ray bursts, pulsars, binary sources, flaring Active Galactic Nuclei, and Galactic transient sources are all phenomena that can best be studied with a wide variety of instruments simultaneously or contemporaneously. From the gamma-ray side, a principal challenge is the latency from the time of an astrophysical event to the recognition of this event in the data. Obtaining quick and complete multiwavelength coverage of gamma-ray sources of interest can be difficult both in terms of logistics and in terms of generating scientific interest.

  16. Multi-Wavelength Observations of Supernova Remnants

    NASA Technical Reports Server (NTRS)

    Williams, B.

    2012-01-01

    Supernova remnants (SNRs) provide a laboratory for studying various astrophysical processes, including particle acceleration, thermal and non thermal emission processes across the spectrum, distribution of heavy elements, the physics of strong shock waves, and the progenitor systems and environments of supernovae. Long studied in radio and X-rays, the past decade has seen a dramatic increase in the detection and subsequent study of SNRs in the infrared and gamma-ray regimes. Understanding the evolution of SNRs and their interaction with the interstellar medium requires a multi-wavelength approach. I will review the various physical processes observed in SNRs and how these processes are intertwined. In particular, I will focus on X-ray and infrared observations, which probe two very different but intrinsically connected phases of the ISM: gas and dust. I will discuss results from multi-wavelength studies of several SNRs at various stages of evolution, including Kepler, RCW 86, and the Cygnus Loop.

  17. A Catalog of Candidate High-redshift Blazars for GLAST

    SciTech Connect

    Arias, Tersi M.; /SLAC /San Francisco State U.

    2006-09-27

    High-redshift blazars are promising candidates for detection by the Gamma-ray Large Area Space Telescope (GLAST). GLAST, expected to be launched in the Fall of 2007, is a high-energy gamma-ray observatory designed for making observations of celestial gamma-ray sources in the energy band extending from 10 MeV to more than 200 GeV. It is estimated that GLAST will find several thousand blazars. The motivations for measuring the gamma-ray emission from distant blazars include the study of the high-energy emission processes occurring in these sources and an indirect measurement of the extragalactic background light. In anticipation of the launch of GLAST we have compiled a catalog of candidate high-redshift blazars. The criteria for sources chosen for the catalog were: high radio emission, high redshift, and a flat radio spectrum. A preliminary list of 307 radio sources brighter than 70mJy with a redshift z {ge} 2.5 was acquired using data from the NASA Extragalactic Database. Flux measurements of each source were obtained at two or more radio frequencies from surveys and catalogs to calculate their radio spectral indices {alpha}. The sources with a flat-radio spectrum ({alpha} {le} 0.5) were selected for the catalog, and the final catalog includes about 200 sources.

  18. Long-term optical-infrared color variability of blazars

    NASA Astrophysics Data System (ADS)

    Zhang, Bing-Kai; Zhou, Xiao-Shan; Zhao, Xiao-Yun; Dai, Ben-Zhong

    2015-11-01

    The long-term optical and infrared color variability of blazars has been investigated with monitoring data from the Small and Moderate Aperture Research Telescope System (SMARTS). The sample in this study consists of 49 flat spectrum radio quasars (FSRQs) and 22 BL Lacertae objects (BL Lacs). The fractional variability amplitudes of each source have been calculated in both optical R band and infrared J band. Overall, the variability amplitudes of FSRQs are larger than those of BL Lacs. The results also suggest that the variability amplitude of most FSRQs is larger at a lower energy band (J band) than at a higher one (R band), but the variability amplitude of BL Lacs is larger at the higher energy band. Both types of blazars display color variation along with variability in brightness. However, they show different variation behaviors in general. In the whole data set, 35 FSRQs exhibit redder-when-brighter trends, and 11 FSRQs exhibit opposite trends; 11 BL Lacs follow bluer-when-brighter trends, and seven BL Lacs follow opposite trends. A detailed examination indicates that there are 10 blazars showing redder-when-brighter trends in their low state, and bluer-when-brighter or stable-when-brighter trends in their high state. Some more complicated color behaviors have also been detected in several blazars. The non-thermal jet emission and the thermal emission from the accretion disk are employed to explain the observed color behaviors.

  19. Extreme blazars as counterparts of IceCube astrophysical neutrinos

    NASA Astrophysics Data System (ADS)

    Padovani, P.; Resconi, E.; Giommi, P.; Arsioli, B.; Chang, Y. L.

    2016-04-01

    We explore the correlation of γ-ray emitting blazars with IceCube neutrinos by using three very recently completed, and independently built, catalogues and the latest neutrino lists. We introduce a new observable, namely the number of neutrino events with at least one γ-ray counterpart, Nν. In all three catalogues we consistently observe a positive fluctuation of Nν with respect to the mean random expectation at a significance level of 0.4-1.3 per cent. This applies only to extreme blazars, namely strong, very high energy γ-ray sources of the high energy peaked type, and implies a model-independent fraction of the current IceCube signal ˜10-20 per cent. An investigation of the hybrid photon - neutrino spectral energy distributions of the most likely candidates reveals a set of ≈5 such sources, which could be linked to the corresponding IceCube neutrinos. Other types of blazars, when testable, give null correlation results. Although we could not perform a similar correlation study for Galactic sources, we have also identified two (further) strong Galactic γ-ray sources as most probable counterparts of IceCube neutrinos through their hybrid spectral energy distributions. We have reasons to believe that our blazar results are not constrained by the γ-ray samples but by the neutrino statistics, which means that the detection of more astrophysical neutrinos could turn this first hint into a discovery.

  20. Long-term observations of the blazar BL Lacertae

    NASA Astrophysics Data System (ADS)

    Strigunov, K. S.; Zhovtan, A. V.

    In 1998-2011, the BL Lacertae blazar was active in various bands, including TeV energies. During the growth of activity in the gamma band, the spectrum of the object became flat, with the spectral index decreasing. This effect is associated with the conversion mechanism of particle acceleration in the BL Lacertae jet.

  1. Multiwavelength Astronomy Modules for High School Students

    NASA Astrophysics Data System (ADS)

    Thomas, Christie; Brazas, J.; Lane, S.; York, D. G.

    2014-01-01

    The University of Chicago Multiwavelength Astronomy modules are web-based lessons covering the history, science, tools, and impact of astronomy across the wavebands, from gamma ray to infrared. Each waveband includes four lessons addressing one aspect of its development. The lessons are narrated by a historical docent or practicing scientist who contributed to a scientific discovery or instrument design significant to astronomical progress. The process of building each lesson began with an interview conducted with the scientist, or the consultation of a memoir or oral history transcript for historical docents. The source was then excerpted to develop a lesson and supplemented by archival material from the University of Chicago Library and other archives; NASA media; and participant contributed photographs, light curves, and spectra. Practicing educators also participated in the lesson development and evaluation. In July 2013, the University of Chicago sponsored 9 teachers and 15 students to participate in a STEM education program designed to engage participants as co-learners as they used the Multiwavelength Astronomy lessons in conjunction with talks given by the participating scientists. Teachers also practiced implementation of the resources with students and designed authentic research activities that make use of NASA mission data, which were undertaken as mini-research projects by student teams during the course of the program. This poster will introduce the Multiwavelength Astronomy web modules; highlight educator experiences in their use with high school audiences; and analyze the module development process, framing the benefits to and contributions of each of the stakeholders including practicing astronomers in research and space centers, high school science educators, high school students, University libraries and archives, and the NASA Science Mission Directorate. The development of these resources, and the summer professional development workshops were

  2. Multi-Wavelength Study of Segue 3

    NASA Astrophysics Data System (ADS)

    Hughes, Joanne D.; Schiefelbein, Spencer; Le, Donna; Corrin, Olivia; Joudi, Hanah; Lacy, Brianna I.

    2016-06-01

    Segue 3 is a very faint and distant star cluster, first identfied as being [Fe/H]=-1.7 dex, but later reclassified as [Fe/H]=-0.8. We study the stellar population in Washington and SDSS filters, adding to VI-photometry in the literature. We show the importance of multi-wavelength coverage, careful filter-selection, and use of the sub-giant and lower red-giant branch populations, to break the age-metallicity degeneracy.

  3. The connection between the parsec-scale radio jet and γ-ray flares in the blazar 1156+295

    NASA Astrophysics Data System (ADS)

    Ramakrishnan, Venkatessh; León-Tavares, Jonathan; Rastorgueva-Foi, Elizaveta A.; Wiik, Kaj; Jorstad, Svetlana G.; Marscher, Alan P.; Tornikoski, Merja; Agudo, Iván; Lähteenmäki, Anne; Valtaoja, Esko; Aller, Margo F.; Blinov, Dmitry A.; Casadio, Carolina; Efimova, Natalia V.; Gurwell, Mark A.; Gómez, José L.; Hagen-Thorn, Vladimir A.; Joshi, Manasvita; Järvelä, Emilia; Konstantinova, Tatiana S.; Kopatskaya, Evgenia N.; Larionov, Valeri M.; Larionova, Elena G.; Larionova, Liudmilla V.; Lavonen, Niko; MacDonald, Nicholas R.; McHardy, Ian M.; Molina, Sol N.; Morozova, Daria A.; Nieppola, Elina; Tammi, Joni; Taylor, Brian W.; Troitsky, Ivan S.

    2014-12-01

    The blazar 1156+295 was active at γ-ray energies, exhibiting three prominent flares during the year 2010. Here, we present results using the combination of broad-band (X-ray through mm single-dish) monitoring data and radio-band imaging data at 43 GHz on the connection of γ-ray events to the ejections of superluminal components and other changes in the jet of 1156+295. The kinematics of the jet over the interval 2007.0-2012.5 using 43 GHz Very Long Baseline Array observations reveal the presence of four moving and one stationary component in the inner region of the blazar jet. The propagation of the third and fourth components in the jet corresponds closely in time to the active phase of the source in γ-rays. We briefly discuss the implications of the structural changes in the jet for the mechanism of γ-ray production during bright flares. To localize the γ-ray emission site in the blazar, we performed the correlation analysis between the 43 GHz radio core and the γ-ray light curve. The time lag obtained from the correlation constrains the γ-ray emitting region in the parsec-scale jet.

  4. A simplified view of blazars: the neutrino background

    NASA Astrophysics Data System (ADS)

    Padovani, P.; Petropoulou, M.; Giommi, P.; Resconi, E.

    2015-09-01

    Blazars have been suggested as possible neutrino sources long before the recent IceCube discovery of high-energy neutrinos. We re-examine this possibility within a new framework built upon the blazar simplified view and a self-consistent modelling of neutrino emission from individual sources. The former is a recently proposed paradigm that explains the diverse statistical properties of blazars adopting minimal assumptions on blazars' physical and geometrical properties. This view, tested through detailed Monte Carlo simulations, reproduces the main features of radio, X-ray, and γ-ray blazar surveys and also the extragalactic γ-ray background at energies ≳ 10 GeV. Here, we add a hadronic component for neutrino production and estimate the neutrino emission from BL Lacertae objects as a class, `calibrated' by fitting the spectral energy distributions of a preselected sample of such objects and their (putative) neutrino spectra. Unlike all previous papers on this topic, the neutrino background is then derived by summing up at a given energy the fluxes of each BL Lac in the simulation, all characterized by their own redshift, synchrotron peak energy, γ-ray flux, etc. Our main result is that BL Lacs as a class can explain the neutrino background seen by IceCube above ˜0.5 PeV while they only contribute ˜10 per cent at lower energies, leaving room to some other population(s)/physical mechanism. However, one cannot also exclude the possibility that individual BL Lacs still make a contribution at the ≈20 per cent level to the IceCube low-energy events. Our scenario makes specific predictions, which are testable in the next few years.

  5. CLUSTERING OF γ-RAY-SELECTED 2LAC FERMI BLAZARS

    SciTech Connect

    Allevato, V.; Finoguenov, A.; Cappelluti, N.

    2014-12-20

    We present the first measurement of the projected correlation function of 485 γ-ray-selected blazars, divided into 175 BL Lacertae (BL Lacs) and 310 flat-spectrum radio quasars (FSRQs) detected in the 2 year all-sky survey by the Fermi-Large Area Telescope. We find that Fermi BL Lacs and FSRQs reside in massive dark matter halos (DMHs) with log M{sub h} = 13.35{sub −0.14}{sup +0.20} and log M{sub h} = 13.40{sub −0.19}{sup +0.15} h {sup –1} M {sub ☉}, respectively, at low (z ∼ 0.4) and high (z ∼ 1.2) redshift. In terms of clustering properties, these results suggest that BL Lacs and FSRQs are similar objects residing in the same dense environment typical of galaxy groups, despite their different spectral energy distributions, power, and accretion rates. We find no difference in the typical bias and hosting halo mass between Fermi blazars and radio-loud active galactic nuclei (AGNs), supporting the unification scheme simply equating radio-loud objects with misaligned blazar counterparts. This similarity in terms of the typical environment they preferentially live in, suggests that blazars tend to occupy the center of DMHs, as already pointed out for radio-loud AGNs. This implies, in light of several projects looking for the γ-ray emission from DM annihilation in galaxy clusters, a strong contamination from blazars to the expected signal from DM annihilation.

  6. MULTI-WAVELENGTH OBSERVATIONS OF THE FLARING GAMMA-RAY BLAZAR 3C 66A IN 2008 OCTOBER

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Borgland, A. W.; Bouvier, A.; Buehler, R.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Bastieri, D.; Buson, S.; Bonamente, E.; Brigida, M.; Bruel, P.

    2011-01-01

    The BL Lacertae object 3C 66A was detected in a flaring state by the Fermi Large Area Telescope (LAT) and VERITAS in 2008 October. In addition to these gamma-ray observations, F-GAMMA, GASP-WEBT, PAIRITEL, MDM, ATOM, Swift, and Chandra provided radio to X-ray coverage. The available light curves show variability and, in particular, correlated flares are observed in the optical and Fermi-LAT gamma-ray band. The resulting spectral energy distribution can be well fitted using standard leptonic models with and without an external radiation field for inverse Compton scattering. It is found, however, that only the model with an external radiation field can accommodate the intra-night variability observed at optical wavelengths.

  7. Characterizing the environment of the blazars PG1553+113 and 3C66A from GEMINI-GMOS data in the i' and g' bands

    NASA Astrophysics Data System (ADS)

    Torres Zafra, T.; Scellone, S. A.; Andruchow, I.

    2014-10-01

    Blazars are active galactic nuclei (AGNs) which, because of their particular orientation with respect to the observer, are characterized by beamed electromagnetic emission from a relativistic jet. It is thus challenging to detect either continuum or line radiation from the nucleus or from the host galaxy; in many cases this prevents the measurement of a spectroscopic redshift. However, the analysis of their environments may give valuable information, considering that galaxies in the blazar's field could share physical and chemical properties with the host galaxy, besides having a similar redshift. We have thus undertaken a photometric study of the galaxies in the fields of the blazars PG1553+113 and 3C66A, based on g' and i' images taken with the GMOS instrument (multi-object spectrograph and camera) at Gemini North 8m telescope. Our goal is to look for concentrations of galaxies around both blazars in order to have a first knowledge of the general characteristics of their immediate environments.

  8. Spectral evolution of flaring blazars from numerical simulations

    NASA Astrophysics Data System (ADS)

    Fromm, C. M.; Perucho, M.; Mimica, P.; Ros, E.

    2016-04-01

    Context. High-resolution Very Long Baseline Interferometry (VLBI) observations of active galactic nuclei revealed traveling and stationary or quasi-stationary radio components in several blazar jets. The traveling radio components are, in general, interpreted as shock waves generated by pressure perturbations injected at the jet nozzle. The stationary features can be interpreted as recollimation shocks in nonpressure matched jets if they show a quasi-symmetric bump in the spectral index distribution. In some jets there may be interactions between the two kinds of shocks. These shock-shock interactions are observable with VLBI techniques and their signature should also be imprinted on the single-dish light curves. Aims: In this paper, we investigate the spectral evolution produced by the interaction between a recollimation shock with traveling shock waves to address the question of whether these interactions contribute to the observed flares and what their signature in both single-dish and VLBI observations looks like. Methods: We performed relativistic hydrodynamic simulations of overpressured and pressure-matched jets. To simulate the shock interaction we injected a perturbation at the jet nozzle once a steady state was reached. We computed the nonthermal emission, including adiabatic and synchotron losses, resulting from the simulation. Results: We show that the injection of perturbations in a jet can produce a bump in emission at GHz frequencies previous to the main flare, which is produced when the perturbation fills the jet in the observer's frame. The detailed analysis of our simulations and the nonthermal emission calculations show that interaction between a recollimation shock and traveling shock produce a typical and clear signature in both the single-dish light curves and in the VLBI observations: the flaring peaks are higher and delayed with respect to the evolution of a perturbation through a conical jet. This fact can allow us to detect such

  9. Optical-microphysical properties of Saharan dust aerosols and composition relationship using a multi-wavelength Raman lidar, in situ sensors and modelling: a case study analysis

    NASA Astrophysics Data System (ADS)

    Papayannis, A.; Mamouri, R. E.; Amiridis, V.; Remoundaki, E.; Tsaknakis, G.; Kokkalis, P.; Veselovskii, I.; Kolgotin, A.; Nenes, A.; Fountoukis, C.

    2012-05-01

    consistent with the retrieved refractive index values. Thus, the inferred chemical properties showed 12-40% of dust content, sulfate composition of 16-60%, and organic carbon content of 15-64%, indicating a possible mixing of dust with haze and smoke. PM10 concentrations levels, PM10 composition results and SEM-EDX (Scanning Electron Microscope-Energy Dispersive X-ray) analysis results on sizes and mineralogy of particles from samples during the Saharan dust transport event were used to evaluate the retrieval.

  10. VARIABILITY OF GAMMA-RAY EMISSION FROM BLAZARS ON BLACK HOLE TIMESCALES

    SciTech Connect

    Vovk, Ie.; Neronov, A.

    2013-04-20

    We investigate the variability properties of blazars in the GeV band using data from the Fermi/Large Area Telescope (LAT) telescope. We find that blazars exhibit variability down to the minimum timescale resolvable by Fermi; this variability is a function of the peak photon count rate in the LAT. This implies that the real minimum variability timescales for the majority of blazars are typically shorter than those resolvable by the LAT. We find that for several blazars these minimum variability timescales reach those associated with the blazar central engine, the supermassive black hole. At the same time, none of the blazars exhibits variability on a timescale shorter than the black hole horizon light-crossing time and/or the period of rotation around the last stable circular orbit. Based on this fact, we argue that the timing properties of the {gamma}-ray signal could be determined by the processes in the direct vicinity of the supermassive black hole.

  11. Cross-calibration of NuSTAR: A Multi-observatory Snapshot of Blazar 3C273

    NASA Astrophysics Data System (ADS)

    Balokovic, Mislav; Ballantyne, D. R.; Blandford, R. D.; Boggs, S. E.; Boydstun, K.; Brenneman, L.; Cappi, M.; Christensen, F.; Craig, W.; Elvis, M.; Fabian, A.; Fuerst, F.; Guainazzi, M.; Hailey, C. J.; Harrison, F.; Madejski, G. M.; Marinucci, A.; Matt, G.; Nandra, K.; Reynolds, C. S.; Stern, D.; Walton, D.; Zhang, W.; NuSTAR Team

    2013-01-01

    The Nuclear Spectroscopic Telescope Array (NuSTAR) is the first space-based observatory capable of focusing X-rays in the hard X-ray band between 3 and 79 keV. Following a successful launch in June 2012, NuSTAR performed a series of calibration observations, including an observation of the blazar 3C273. In this poster we present results of simultaneous observations of 3C273 by NuSTAR, XMM-Newton, Chandra, Suzaku, Swift and INTEGRAL taken primarily for cross-calibration and demonstrate the unique capability of NuSTAR to extend high sensitivity observations above 10 keV. We further complement this rich X-ray data set with nearly simultaneous multi-wavelength data spanning the radio, infrared, optical and gamma-ray bands in order to constrain the low-state spectral energy distribution of 3C273. We discuss both early science from 3C273 as well as the NuSTAR cross-calibration targets and plans.

  12. Broad-Band Continuum and Line Emission of the gamma-Ray Blazar PKS 0537-441

    NASA Technical Reports Server (NTRS)

    Pian, E.; Falomo, R.; Hartman, R. C.; Maraschi, L.; Tavecchio, F.; Tornikoski, M.; Treves, A.; Urry, C. M.; Ballo, L.; Mukherjee, R.; White, Nicholas E. (Technical Monitor)

    2002-01-01

    PKS 0537-441, a bright gamma ray emitting blazar was observed at radio, optical, UV and X-ray frequencies during various EGRET paintings, often quasi-simultaneously. In 1995 the object was found in an intense emission state at all wavelengths. BeppoSAX observations made in 1998, non-simultaneously with exposures at other frequencies, allow us to characterize precisely the spectral shape of the high energy blazer component, which we attribute to inverse Compton scatter in The optical-to-gamma-ray spectral energy distributions at the different epochs show that the gamma-ray luminosity dominates the barometric output. This, together with the presence of optical and UV line emission, suggests that, besides the synchrotron self-Compton mechanism, the Compton upscattering of photons external to the jet (e.g., in the broad line region) may have a significant role for high energy radiation. The multiwavelength variability can be reproduced by changes of the plasma bulk Lorentz factor. The spectrum secured by ICE in 1995 appears to be partially absorbed shortward of approximately 1700 Angstroms. However, this signature is not detected in the HST spectrum taker during a lower state of the source. The presence of intervening absorbers is not supported by optical imaging and spectroscopy of the field.

  13. The high-energy diffuse cosmic gamma-ray background radiation from blazars

    NASA Technical Reports Server (NTRS)

    Stecker, F. W.; Salamon, M. H.; Malkan, M. A.

    1993-01-01

    We predict the spectrum and flux of the high-energy diffuse cosmic gamma-ray background radiation produced by blazars. Our calculations are based on the Compton Observatory EGRET observations of high-energy gamma-rays from these objects, the Whipple observation of TeV gamma-rays from Mrk 421, and radio population studies of flat-spectrum radio sources. Our statistical analysis gives a result consistent with a linear correlation. We then use the radio luminosity function and redshift evolution to calculate the gamma-ray background. We find that blazars cannot account for the flux level or steep spectrum of the background observed by SAS 2 in the sub-GeV range, but could likely provide the dominant background component in the multi-GeV energy range and above. We predict a differential photon spectral index for this component of about 2 up to about 10 GeV. Above that energy, the spectrum should gradually steepen owing to pair production by interactions of the gamma-rays with intergalactic infrared photons. Using the calculations of this effect by Stecker et al. (1992), we estimate a spectral index of about 3.5 for energies above a TeV.

  14. Gamma-ray flares in blazars accompanied by synchrotron polarization angle swings

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Boettcher, Markus; Chen, Xuhui

    2014-08-01

    We present a detailed analysis of time- and energy-dependent synchrotron polarization signatures in a shock-in-jet model for gamma-ray blazars. Our calculations employ a full 3D radiation transfer code, considering synchrotron emission from a helical magnetic field, and taking into account all light-travel-time and other relevant geometric effects, while the relevant synchrotron self-Compton and external Compton effects are handled with a 2D Monte-Carlo/Fokker-Planck code. We find that a scenario in which a relativistic shock propagating through the jet leads to a compression of the magnetic field, increasing the toroidal field component, can lead to correlated synchrotron + SSC flaring, associated with substantial variability in the synchrotron polarization percentage and position angle (PA). Most importantly, this scenario naturally explains large PA rotations by ≥180 deg, as observed in connection with gamma-ray flares in several blazars, without the need for bent or helical jet trajectories or other non-axisymmetric jet features.

  15. Awakening of The High-Redshift Blazar CGRaBS J0809+5341

    NASA Astrophysics Data System (ADS)

    Paliya, Vaidehi S.; Parker, M. L.; Stalin, C. S.; Fabian, A. C.; Ramya, S.; Covino, S.; Tagliaferri, G.; Sahayanathan, S.; Ravikumar, C. D.

    2015-04-01

    CGRaBS J0809+5341, a high-redshift blazar at z = 2.144, underwent a giant optical outburst on 2014 April 19 when it brightened by ˜5 mag and reached an unfiltered apparent magnitude of 15.7 mag. This implies an absolute magnitude of -30.5 mag, making it one of the brightest quasars in the universe. This optical flaring triggered us to carry out observations during the decaying part of the flare covering a wide energy range using the Nuclear Spectroscopic Telescope Array, Swift, and ground-based optical facilities. For the first time, the source is detected in γ-rays by the Large Area Telescope on board the Fermi Gamma-Ray Space Telescope. A high optical polarization of ˜10% is also observed. Using the Sloan Digital Sky Survey spectrum, the accretion disk luminosity and black hole mass are estimated as 1.5 × 1045 erg s-1 and 108.4 M⊙, respectively. Using a single zone leptonic emission model, we reproduce the spectral energy distribution of the source during the flaring activity. This analysis suggests that the emission region is probably located outside the broad-line region, and the jet becomes radiatively efficient. We also show that the overall properties of CGRaBS J0809+5341 seem to not be in agreement with the general properties observed in high-redshift blazars up to now.

  16. VizieR Online Data Catalog: Multifrequency catalogue of blazars, Roma-BZCAT (Massaro+, 2009)

    NASA Astrophysics Data System (ADS)

    Massaro, E.; Giommi, P.; Leto, C.; Marchegiani, P.; Maselli, A.; Perri, M.; Piranomonte, S.; Sclavi, S.

    2013-08-01

    The Roma-BZCAT is structured in two parts. Part 1, at present the only one available on-line, contains the lists of blazars, which are classified in three main groups, according to their spectral properties. Each blazar is identified by a three-letter code, where the first two are BZ for blazar and the third one specifies the type, followed by the truncated equatorial coordinates (J2000). The codes are defined in the "Note (G1)" below. (2 data files).

  17. Multiwavelength Studies For Titan's Atmospheric Composition Analysis

    NASA Astrophysics Data System (ADS)

    Benilan, Yves; Sebbar, E. Es; Fray, N.; Gazeau, M.; Jolly, A.; Schwell, M.; Guillemin, J.

    2009-09-01

    Titan's atmosphere mainly made of nitrogen and methane is rich in organic molecules. Hydrocarbons are formed from the photolytic dissociation of CH4 and nitriles are created by dissociation of N2 followed by reactions with hydrocarbons. In order to understand the physicochemical mechanisms responsible for the evolution of Titan's atmosphere, photochemical models are built. The latter need constrains for vertical profiles of organic compounds from the high thermosphere down to the low stratosphere as well as photodissociation rates. Those profiles over the entire atmosphere can be retrieved from Cassini observations, in particular by limb sounding, coupling infrared and ultraviolet spectroscopy. However, in order to interpret those data obtained by the ultraviolet (UVIS) and infrared (CIRS) spectrometers on board Cassini's spacecraft, precise spectroscopic parameters and their dependence on temperature are needed. We will review the current knowledge in this field of planetary spectroscopy and point out the lack of spectroscopic parameters of already detected species, especially for radiative transfer calculations at low temperature. We will focus our talk on the Cyanogen molecule (C2N2) which has been observed in Titan atmosphere in the FIR domain around 230 cm-1. We will present the latest spectroscopic studies we have performed on this molecule. Those studies cover the entire spectrum from the mid- infrared and to the vacuum ultraviolet. Integrated band intensities have been determined for all bands in the infrared. In the ultraviolet domain, we have determined absolute cross sections from 350 down to 80 nm covering six orders of magnitude absorptions. We will also show how temperature can influence VUV absorption coefficients and the implications on the interpretation of UVIS observations.

  18. A Multiwavelength Investigation of Poor Clusters of Galaxies

    NASA Astrophysics Data System (ADS)

    Bliton, M.; Burns, J. O.; Voges, W.

    1999-12-01

    We present analysis of the X-ray, optical, and radio properties of a volume-limited sample of poor clusters of galaxies. Our poor cluster sample is composed of 339 groups in the redshift range 0.01-0.03, spanning the entire range of richness from very poor systems to Abell clusters. The multiwavelength properties of our sample were gathered from the ROSAT All-Sky Survey, the Palomar Digitized Sky Survey, and the Northern VLA Sky Survey. Properties discussed include X-ray luminosity, optical richness, spiral fraction, and radio fraction, among others. We also present a number of unique poor clusters that exhibit unexpected properties in the various wavelengths studied. This work was supported by NASA grant NAG5-6772 to M.B. & J.O.B.

  19. Blazar Jets Push Closer to Cosmic Speed Limit

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have discovered jets of plasma blasted from the cores of distant galaxies at speeds within one-tenth of one percent of the speed of light, placing these plasma jets among the fastest objects yet seen in the Universe. "This tells us that the physical processes at the cores of these galaxies, called blazars, are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California. Piner, who worked on the project with student Dipesh Bhattari, also of Whittier College, Philip Edwards of the Japan Aerospace Exploration Agency, and Dayton Jones of NASA's Jet Propulsion Laboratory, presented their findings to the American Astronomical Society's meeting in San Diego, California. According to Einstein's Special Theory of Relativity, no object with mass can be accelerated to the speed of light. To get even close to the speed of light requires enormous amounts of energy. "For example, to accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said, "and the blobs of plasma in these jets are at least as massive as a large planet". Blazars are active galactic nuclei -- energetic regions surrounding massive black holes at the centers of galaxies. Material being drawn into the black hole forms a spinning disk called an accretion disk. Powerful jets of charged particles are ejected at high speeds along the poles of accretion disks. When these jets happen to be aimed nearly toward the Earth, the objects are called blazars. Taking advantage of the extremely sharp radio "vision" of the continent-wide VLBA, the scientists tracked individual features in the jets of three blazars at distances from Earth ranging from 7.3 to 9 billion light-years. A Boston University team led by Svetlana Jorstad earlier had identified

  20. Blazar Jets Push Closer to Cosmic Speed Limit

    NASA Astrophysics Data System (ADS)

    2005-01-01

    Astronomers using the National Science Foundation's Very Long Baseline Array (VLBA) have discovered jets of plasma blasted from the cores of distant galaxies at speeds within one-tenth of one percent of the speed of light, placing these plasma jets among the fastest objects yet seen in the Universe. "This tells us that the physical processes at the cores of these galaxies, called blazars, are extremely energetic and are capable of propelling matter very close to the absolute cosmic speed limit," said Glenn Piner of Whittier College in Whittier, California. Piner, who worked on the project with student Dipesh Bhattari, also of Whittier College, Philip Edwards of the Japan Aerospace Exploration Agency, and Dayton Jones of NASA's Jet Propulsion Laboratory, presented their findings to the American Astronomical Society's meeting in San Diego, California. According to Einstein's Special Theory of Relativity, no object with mass can be accelerated to the speed of light. To get even close to the speed of light requires enormous amounts of energy. "For example, to accelerate a bowling ball to the speed newly measured in these blazars would require all the energy produced in the world for an entire week," Piner said, "and the blobs of plasma in these jets are at least as massive as a large planet". Blazars are active galactic nuclei -- energetic regions surrounding massive black holes at the centers of galaxies. Material being drawn into the black hole forms a spinning disk called an accretion disk. Powerful jets of charged particles are ejected at high speeds along the poles of accretion disks. When these jets happen to be aimed nearly toward the Earth, the objects are called blazars. Taking advantage of the extremely sharp radio "vision" of the continent-wide VLBA, the scientists tracked individual features in the jets of three blazars at distances from Earth ranging from 7.3 to 9 billion light-years. A Boston University team led by Svetlana Jorstad earlier had identified

  1. Multi-wavelength compressive computational ghost imaging

    NASA Astrophysics Data System (ADS)

    Welsh, Stephen S.; Edgar, Matthew P.; Jonathan, Phillip; Sun, Baoqing; Padgett, Miles J.

    2013-03-01

    The field of ghost imaging encompasses systems which can retrieve the spatial information of an object through correlated measurements of a projected light field, having spatial resolution, and the associated reflected or transmitted light intensity measured by a photodetector. By employing a digital light projector in a computational ghost imaging system with multiple spectrally filtered photodetectors we obtain high-quality multi-wavelength reconstructions of real macroscopic objects. We compare different reconstruction algorithms and reveal the use of compressive sensing techniques for achieving sub-Nyquist performance. Furthermore, we demonstrate the use of this technology in non-visible and fluorescence imaging applications.

  2. Long-Term Multiwaveband Monitoring of Selected Blazars (core Program)

    NASA Astrophysics Data System (ADS)

    The investigators request RXTE time to continue their long-term monitoring of the blazars 3C 279, PKS 1510-089, BL Lac, and 3C 273 2-3 times per week at radio, mm, IR, optical, X-ray, and, with the advent of GLAST, gamma-ray wavelengths. These, plus an added 5th object, CTA102, include blazars bright enough to detect strongly with RXTE and GLAST as well as to measure polarization on 7 mm VLBA images and at optical bands. By matching polarized features on VLBA images with variable polarization at optical bands and by associating X-ray and gamma-ray flares with similar events at these longer wavelengths, the investigators will locate where in the jet the emission occurs at all these wavebands. The relative timing of flares as a function of wavelength will overconstrain emission models.

  3. A BLAZAR-LIKE RADIO FLARE IN MRK 231

    SciTech Connect

    Reynolds, Cormac; Hurley-Walker, Natasha; Punsly, Brian; O'Dea, Christopher P. E-mail: brian.punsly@comdev-usa.com

    2013-10-20

    Radio monitoring of the broad absorption line quasar (BALQSO) Mrk 231 from 13.9 GHz to 17.6 GHz detected a strong flat spectrum flare. Even though BALQSOs are typically weak radio sources, the 17.6 GHz flux density doubled in ≈150 days, from ≈135 mJy to ≈270 mJy. It is demonstrated that the elapsed rise time in the quasar rest frame and the relative magnitude of the flare is typical of some of the stronger flares in blazars that are usually associated with the ejection of discrete components on parsec scales. The decay of a similar flare was found in a previous monitoring campaign at 22 GHz. We conclude that these flares are not rare. The implication is that Mrk 231 seems to be a quasar in which the physical mechanism that produces the broad absorption line wind is in tension with the emergence of a fledgling blazar.

  4. Quasi-periodicities at Year-like Timescales in Blazars

    NASA Astrophysics Data System (ADS)

    Sandrinelli, A.; Covino, S.; Dotti, M.; Treves, A.

    2016-03-01

    We searched for quasi-periodicities on year-like timescales in the light curves of six blazars in the optical—near-infrared bands and we made a comparison with the high energy emission. We obtained optical/NIR light curves from Rapid Eye Mounting photometry plus archival Small & Moderate Aperture Research Telescope System data and we accessed the Fermi light curves for the γ-ray data. The periodograms often show strong peaks in the optical and γ-ray bands, which in some cases may be inter-related. The significance of the revealed peaks is then discussed, taking into account that the noise is frequency dependent. Quasi-periodicities on a year-like timescale appear to occur often in blazars. No straightforward model describing these possible periodicities is yet available, but some plausible interpretations for the physical mechanisms causing periodic variabilities of these sources are examined.

  5. An ultraviolet atlas of quasar and blazar spectra

    NASA Technical Reports Server (NTRS)

    Kinney, A. L.; Bohlin, R. C.; Blades, J. C.; York, D. G.

    1991-01-01

    An atlas is presented which provides a uniformly extracted and calibrated set of over 1000 UV spectra of the highest possible SNR for quasars and blazars observed with the IUE. The spectra show that quasars and blazars vary more in the UV than in the optical, and show increasing variability toward shorter wavelengths. The low-redshift quasars have Ly-alpha emission lines dominated by strong, narrow components, while high-redshift quasars seem to lack such narrow components. Absorption by gas in the Galaxy is ubiquitous in strong interstellar lines of C II, O I, Si II, Mg II, and Fe II. Of special note is the detection of Fe II and Mg II absorption due to gas associated with NGC3067 in the quasar 3C 232. Over 20 percent of the combined quasar and Seyfert 1 sample show either associated absorption or absorption just shortward of the emission redshift.

  6. Prominent outburst of the blazar CTA 102 in 2012

    NASA Astrophysics Data System (ADS)

    Larionov, V. M.; Blinov, D. A.; Jorstad, S. G.; Marscher, A. P.; Villata, M.; Raiteri, C. M.; Agudo, I.; Smith, P. S.; Morozova, D. A.; Troitsky, I. S.; Clemens, D. P.

    2013-12-01

    After a few years of quiescence, the blazar CTA 102 underwent a large outburst in the fall of 2012. The flare has been tracked from γ-rays to near-infrared, including Fermi and Swift data as well as polarimetric data from several observatories. An intensive GASP-WEBT collaboration campaign in optical and NIR bands, with the addition of previously unpublished archival data, allows comparison of this outburst with the previous activity period of this blazar in the early 2000s. We find remarkable similarity between the optical and γ-ray behavior of CTA 102 during the outburst, without any time lag between the two light curves, indicating co-spatiality of the optical and γ-ray emission regions. A strong harder-when-brighter spectral dependence is seen both in γ-rays and optical. The polarimetric behavior of CTA 102 during the outburst conforms with a shock-in-jet interpretation.

  7. Frequency Stratification of the Nonthermal Emission in Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.

    2001-01-01

    Research supported by this grant involved theoretical investigations of the multifrequency nonthermal emission from the relativistic jets in blazars, which are quasars and related objects with highly variable brightness. In the initial stage of the project, one-dimensional, conical (i.e., spherical symmetry between the jet axis and surface is assumed) jet models were used to explain the multi-waveband spectra and variability of blazars. The results were applied to two flares observed in the object PKS 2155-304, leading to the conclusion that the distinct differences in the observed characteristics of the two flares can be explained with the same jet model if two different physical parameters (the magnetic field in the first flare and the efficiency of acceleration of electrons to high energies in the second) varied.

  8. The disk-jet connection of Fermi 2LAC blazars

    NASA Astrophysics Data System (ADS)

    Du, L. M.; Xie, Zh. H.; Yi, T. F.; Xue, R.; Xu, Y. B.; Liu, W. G.; Wang, X. H.

    2016-07-01

    In this article, an estimator of the radiative power for blazars is proposed and is used in the study of the link between the accretion disk power and jet power. The results lend support to the disk-jet symbiosis. Since the blazars are strongly beamed sources, our results suggest that the Doppler enhancement of the sources needs to be removed to obtain physically reasonable results in the disk-jet connection study. The results after de-beaming suggest that FSRQs are accreting in the radiatively efficient regime, while the BL Lac population shows a flatter dependence between jet power and disk power, possibly due to a mixture of sources in the radiatively efficient (the broad lined BL Lacs) and inefficient (the bulk of the BL Lac population) regimes.

  9. RELAXATION OF BLAZAR-INDUCED PAIR BEAMS IN COSMIC VOIDS

    SciTech Connect

    Miniati, Francesco; Elyiv, Andrii

    2013-06-10

    The stability properties of a low-density ultrarelativistic pair beam produced in the intergalactic medium (IGM) by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could considerably affect the thermal history of the IGM and structure formation. We use a Monte Carlo method to quantify the properties of the blazar-induced electromagnetic shower, in particular the bulk Lorentz factor and the angular spread of the pair beam generated by the shower, as a function of distance from the blazar itself. We then use linear and nonlinear kinetic theory to study the stability of the pair beam against the growth of electrostatic plasma waves, employing the Monte Carlo results for our quantitative estimates. We find that the fastest growing mode, like any perturbation mode with even a very modest component perpendicular to the beam direction, cannot be described in the reactive regime. Due to the effect of nonlinear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found to be significantly longer than the inverse Compton loss time. Finally, density inhomogeneities associated with cosmic structure induce loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the IGM are stable on timescales that are long compared with the electromagnetic cascades. There appears to be little or no effect of pair beams on the IGM.

  10. Seed Photon Fields of Blazars in the Internal Shock Scenario

    NASA Astrophysics Data System (ADS)

    Joshi, M.; Marscher, A. P.; Böttcher, M.

    2014-04-01

    We extend our approach of modeling spectral energy distribution (SED) and light curves of blazars to include external Compton (EC) emission due to inverse Compton scattering of an external anisotropic target radiation field. We describe the time-dependent impact of such seed photon fields on the evolution of multifrequency emission and spectral variability of blazars using a multi-zone time-dependent leptonic jet model, with radiation feedback, in the internal shock model scenario. We calculate accurate EC-scattered high-energy (HE) spectra produced by relativistic electrons throughout the Thomson and Klein-Nishina regimes. We explore the effects of varying the contribution of (1) a thermal Shakura-Sunyaev accretion disk, (2) a spherically symmetric shell of broad-line clouds, the broad-line region (BLR), and (3) a hot infrared emitting dusty torus (DT), on the resultant seed photon fields. We let the system evolve to beyond the BLR and within the DT and study the manifestation of the varying target photon fields on the simulated SED and light curves of a typical blazar. The calculations of broadband spectra include effects of γ-γ absorption as γ-rays propagate through the photon pool present inside the jet due to synchrotron and inverse Compton processes, but neglect γ-γ absorption by the BLR and DT photon fields outside the jet. Thus, our account of γ-γ absorption is a lower limit to this effect. Here, we focus on studying the impact of parameters relevant for EC processes on HE emission of blazars.

  11. Relaxation of Blazar-induced Pair Beams in Cosmic Voids

    NASA Astrophysics Data System (ADS)

    Miniati, Francesco; Elyiv, Andrii

    2013-06-01

    The stability properties of a low-density ultrarelativistic pair beam produced in the intergalactic medium (IGM) by multi-TeV gamma-ray photons from blazars are analyzed. The problem is relevant for probes of magnetic field in cosmic voids through gamma-ray observations. In addition, dissipation of such beams could considerably affect the thermal history of the IGM and structure formation. We use a Monte Carlo method to quantify the properties of the blazar-induced electromagnetic shower, in particular the bulk Lorentz factor and the angular spread of the pair beam generated by the shower, as a function of distance from the blazar itself. We then use linear and nonlinear kinetic theory to study the stability of the pair beam against the growth of electrostatic plasma waves, employing the Monte Carlo results for our quantitative estimates. We find that the fastest growing mode, like any perturbation mode with even a very modest component perpendicular to the beam direction, cannot be described in the reactive regime. Due to the effect of nonlinear Landau damping, which suppresses the growth of plasma oscillations, the beam relaxation timescale is found to be significantly longer than the inverse Compton loss time. Finally, density inhomogeneities associated with cosmic structure induce loss of resonance between the beam particles and plasma oscillations, strongly inhibiting their growth. We conclude that relativistic pair beams produced by blazars in the IGM are stable on timescales that are long compared with the electromagnetic cascades. There appears to be little or no effect of pair beams on the IGM.

  12. BLAZAR OPTICAL VARIABILITY IN THE PALOMAR-QUEST SURVEY

    SciTech Connect

    Bauer, Anne; Baltay, Charles; Coppi, Paolo; Ellman, Nancy; Jerke, Jonathan; Rabinowitz, David; Scalzo, Richard

    2009-07-10

    We study the ensemble optical variability of 276 flat-spectrum radio quasars (FSRQs) and 86 BL Lacs in the Palomar-QUEST Survey with the goal of searching for common fluctuation properties, examining the range of behavior across the sample, and characterizing the appearance of blazars in such a survey so that future work can more easily identify such objects. The survey, which covers 15,000 deg{sup 2} multiple times over 3.5 years, allows for the first ensemble blazar study of this scale. Variability amplitude distributions are shown for the FSRQ and BL Lac samples for numerous time lags, and also studied through structure function analyses. Individual blazars show a wide range of variability amplitudes, timescales, and duty cycles. Of the best-sampled objects, 35% are seen to vary by more than 0.4 mag; for these, the fraction of measurements contributing to the high-amplitude variability ranges constantly from about 5% to 80%. Blazar variability has some similarities to that of type I quasi-stellar objects (QSOs) but includes larger amplitude fluctuations on all timescales. FSRQ variability amplitudes are particularly similar to those of QSOs on timescales of several months, suggesting significant contributions from the accretion disk to the variable flux at these timescales. Optical variability amplitudes are correlated with the maximum apparent velocities of the radio jet for the subset of FSRQs with MOJAVE Very Long Baseline Array measurements, implying that the optically variable flux's strength is typically related to that of the radio emission. We also study CRATES radio-selected FSRQ candidates, which show similar variability characteristics to known FSRQs; this suggests a high purity for the CRATES sample.

  13. Seed photon fields of blazars in the internal shock scenario

    SciTech Connect

    Joshi, M.; Marscher, A. P.; Böttcher, M.

    2014-04-20

    We extend our approach of modeling spectral energy distribution (SED) and light curves of blazars to include external Compton (EC) emission due to inverse Compton scattering of an external anisotropic target radiation field. We describe the time-dependent impact of such seed photon fields on the evolution of multifrequency emission and spectral variability of blazars using a multi-zone time-dependent leptonic jet model, with radiation feedback, in the internal shock model scenario. We calculate accurate EC-scattered high-energy (HE) spectra produced by relativistic electrons throughout the Thomson and Klein-Nishina regimes. We explore the effects of varying the contribution of (1) a thermal Shakura-Sunyaev accretion disk, (2) a spherically symmetric shell of broad-line clouds, the broad-line region (BLR), and (3) a hot infrared emitting dusty torus (DT), on the resultant seed photon fields. We let the system evolve to beyond the BLR and within the DT and study the manifestation of the varying target photon fields on the simulated SED and light curves of a typical blazar. The calculations of broadband spectra include effects of γ-γ absorption as γ-rays propagate through the photon pool present inside the jet due to synchrotron and inverse Compton processes, but neglect γ-γ absorption by the BLR and DT photon fields outside the jet. Thus, our account of γ-γ absorption is a lower limit to this effect. Here, we focus on studying the impact of parameters relevant for EC processes on HE emission of blazars.

  14. Search for GeV γ-Ray Pair Halos Around Low Redshift Blazars.

    PubMed

    Chen, Wenlei; Buckley, James H; Ferrer, Francesc

    2015-11-20

    We report on the results of a search for γ-ray pair halos with a stacking analysis of low redshift blazars using data from the Fermi Large Area Telescope. For this analysis we used a number of a priori selection criteria, including the spatial and spectral properties of the Fermi sources. The angular distribution of ~1 GeV photons around 24 stacked isolated high-synchrotron-peaked BL Lacs with redshift z<0.5 shows an excess over that of pointlike sources. A frequentist test yields a p value of p~0.01 for the extended emission against the point-source hypothesis. A Bayesian estimation provides Bayes factors log_{10}B_{10}>2, consistent with expectations for pair halos produced in the intergalactic magnetic fields with strength B_{IGMF}~10^{-17}-10^{-15} G. PMID:26636838

  15. Blazar candidates beyond redshift 4 observed by Swift

    NASA Astrophysics Data System (ADS)

    Sbarrato, T.; Ghisellini, G.; Tagliaferri, G.; Foschini, L.; Nardini, M.; Tavecchio, F.; Gehrels, N.

    2015-01-01

    We have selected SDSS J222032.50+002537.5 and SDSS J142048.01+120545.9 as best blazar candidates out of a complete sample of extremely radio-loud quasars at z > 4, with highly massive black holes. We observed them and a third serendipitous candidate with similar features (PMN J2134-0419) in the X-rays with the Swift/XRT telescope, to confirm their blazar nature. We observed strong and hard X-ray fluxes (i.e. α_X ˜ ≪ap 0.6, where F(ν )∝ ν ^{-α_X} in the 0.3-10 keV observed energy range, ˜1-40 keV rest frame) in all three cases. This allowed us to classify our candidates as real blazars, being characterized by large Lorentz factors (˜13) and very small viewing angles (˜3°). All three sources have black hole masses exceeding 109 M⊙ and their classification provides intriguing constraints on supermassive black hole formation and evolution models. We confirm our earlier suggestion that there are different formation epochs of extremely massive black holes hosted in jetted (z ˜ 4) and non-jetted systems (z ˜ 2.5).

  16. ESTIMATION OF THE VISCOSITY PARAMETER IN ACCRETION DISKS OF BLAZARS

    SciTech Connect

    Xie, Z. H.; Ma, L.; Zhang, X.; Du, L. M.; Hao, J. M.; Yi, T. F.; Qiao, E. L.

    2009-12-20

    For an optical monitoring blazar sample set whose typical minimum variability timescale is about 1 hr, we estimate a mean value of the viscosity parameter in their accretion disk. We assume that optical variability on timescales of hours is caused by local instabilities in the inner accretion disk. Comparing the observed variability timescales to the thermal timescales of alpha-disk models, we could obtain constraints on the viscosity parameter (alpha) and the intrinsic Eddington ratio (L{sup in}/L{sub Edd}=m-dot), 0.104 <= alpha <= 0.337, and 0.0201 <= L {sup in}/L{sub Edd} <= 0.1646. These narrow ranges suggest that all these blazars are observed in a single state, and thus provide a new evidence for the unification of flat-spectrum radio quasars and BL Lacs into a single blazar population. The values of alpha we derive are consistent with the theoretical expectation alpha approx 0.1-0.3 of Narayan and Mcclintock for advection-dominated accretion flow and are also compatible with Pessah et al.'s predictions (alpha >= 0.1) by numerical simulations in which magnetohydrodynamic turbulence is driven by the saturated magnetorotational instability.

  17. M87 - a misaligned synchrotron-proton blazar?

    NASA Astrophysics Data System (ADS)

    Reimer, A.; Protheroe, R. J.; Donea, A.-C.

    2004-04-01

    The Fanaroff-Riley (FR) class 1 radio galaxy M87 is widely believed to be a misaligned blazar of BL Lac type. Its unresolved nuclear region is a strong non-thermal emitter of radio to X-ray photons that have been interpreted as synchrotron radiation. The recent detection of TeV-photons by the HEGRA-telescope array, if confirmed, would make it the first radio galaxy detected at TeV-energies. We discuss M87's core emission in the context of the hadronic Synchrotron-Proton Blazar model. By modeling M87's non-simultaneous spectral energy distribution we predict the peak power of the γ-ray component at ˜100 GeV at a flux level detectable for the new Cherenkov telescopes H.E.S.S., VERITAS and MAGIC. Thanks to M87's proximity TeV photon absorption in the cosmic background radiation field is negligible. This offers for the first time the opportunity to directly trace the intrinsic high energy cutoff of a TeV-emitting blazar-like object.

  18. The Ultraviolet Continua of Blazars: A Reconsideration of IUE Archives

    NASA Astrophysics Data System (ADS)

    Pian, E.; Treves, A.

    1993-10-01

    The IUE archive data on blazars are reconsidered. They refer to 47 objects, 24 radio-strong BL Lac objects, 15 radio-weak BL Lac objects, and eight optically violently variable quasars, increasing substantially the sample examined by Ghisellini et al. (1986). For each object a dereddened spectral slope is evaluated starting from the extraction of Kinney et al. (1991) and Edelson et al. (1992), and deriving the extinction from the hydrogen column density obtained through radio data. The 1200-3000 Å average spectral index is found to be α ≃ 1, with radio-strong BL Lac objects being steeper (αν ≃ 1.2) than radio-weak ones (αν ≃ 0.7). The behavior of blazars in the UV does not depart much from that of PG quasars for which the average spectral index is αν ≃ ≃ 0.8. Comparing with recent results of Falomo et al. (1993a) on the infrared-optical continuum of blazars we find no indication of a steepening in the 8 × 1013 -2 × 1015 Hz band, while the extrapolation to soft X-rays indicates at most a modest steepening.

  19. Multiwavelength Modeling of Nova Atmospheres

    NASA Technical Reports Server (NTRS)

    Hauschildt, P. H.; Starrfield, S.

    1997-01-01

    We have analyzed the early optically thick ultraviolet spectra of Nova OS And 1986 using a grid of spherically symmetric, non-LTE, line-blanketed, expanding model atmospheres and synthetic spectra with the following set of parameters: 5,000 less than or equal to T(sub model) less than or equal to 60,000K, solar abundances, (rho)(alpha) r(sup -3), v(sub max) = 2000 km/s, L = 6 x 10(exp 4) solar luminosity, and a statistical or microturbulent velocity of 50 km/s. We used the synthetic spectra to estimate the model parameters corresponding to the observed IUE spectra. The fits to the observations were then iteratively improved by changing the parameters of the model atmospheres, in particular T(sub model) and the abundances, to arrive at the best fits to the optically thick pseudo-continuum and the features found in the IUE spectra. The IUE spectra show two different optically thick subphases. The earliest spectra, taken a few days after maximum optical light, show a pseudo-continuum created by overlapping absorption lines. The later observations, taken approximately 3 weeks after maximum light, show the simultaneous presence of allowed, semi-forbidden, and forbidden lines in the observed spectra. Analysis of these phases indicate that OS And 86 had solar metallicities except for Mg which showed evidence of being underabundant by as much as a factor of 10. We determine a distance of 5.1 kpc to OS And 86 and derive a peak bolometric luminosity of approximately 5 x 10(exp 4) solar luminosity. The computed nova parameters provide insights into the physics of the early outburst and explain the spectra seen by IUE. Lastly, we find evidence in the later observations for large non-LTE effects of Fe II which, when included, lead to much better agreement with the observations.

  20. ATCA follow-up of blazar candidates in the H-ATLAS fields

    NASA Astrophysics Data System (ADS)

    Massardi, Marcella; Ricci, Roberto; de Zotti, Gianfranco; White, Glenn; Michalowski, Michal; Ivison, Rob; Baes, Maarten; Lapi, Andrea; Temi, Pasquale; Lopez-Caniego, Marcos; Herranz, Diego; Seymour, Nick; Gonzalez-Nuevo, Joaquin; Bonavera, Laura; Negrello, Mattia

    2012-04-01

    The Herschel-ATLAS (H-ATLAS) survey that is covering 550 sq.deg. in 5 bands from 100 to 500 micron, allows for the first time a flux limited selection of blazars at sub-mm wavelengths. This wavelength range is particularly interesting because it is where the most luminous blazars are expected to show the synchrotron peak. The peak frequency and luminosity carry key information on the blazar physics. However, blazars constitute a tiny fraction of H-ATLAS sources and therefore picking them up isn't easy. A criterion to efficiently select candidate blazars exploiting the roughly flat blazar continuum spectrum from radio to sub-mm wavelengths has been devised by Lopez-Caniego et al. (in prep.). Multifrequency radio follow-up is however a necessary step to assess the nature of candidates. We propose to complete the validation of candidates in the H-ATLAS equatorial fields (partly done during few hours of ATCA DDT allocated time and with Medicina radiotelescope observations) and to extend the investigation to the Southern (SGP) fields reconstructing the blazars SED between 1.1 and 40 GHz. This will provide the first statistically significant blazar sample selected at sub-mm wavelengths.

  1. Broadband radio jet emission and variability of γ-ray blazars

    NASA Astrophysics Data System (ADS)

    Nestoras, Ioannis

    2015-07-01

    AGN (Active Galactic Nuclei) and in particular their subclass blazars, are among the most energetic objects observed in the universe, featuring extreme phenomenological characteristics such as rapid broadband flux density and polarization variability, fast super--luminal motion, high degree of polarization and a broadband, double-humped spectral energy distribution (SED). The details of the emission processes and violent variability of blazars are still poorly understood. Variability studies give important clues about the size, structure, physics and dynamics of the emitting region making AGN/blazar monitoring programs of uttermost importance in providing the necessary constraints for understanding the origin of energy production. In this framework the F-gamma program was initiated, monitoring monthly 60 fermi detected AGN/blazars at 12 frequencies between 2.6 and 345GHz since 2007. For the thesis in hand observations and data analysis were performed within the realms of the F-gamma program, using the Effelsberg (EB) 100m and Pico Veleta (PV) 30m telescopes at 10 frequency bands ranging from 2.64 to 142GHz. The cm to short-mm variability/spectral characteristics are monitored for a sample of 59 sources for a period of five years enabling for the first time a detailed study of the observed flaring activity in both the light curve and spectral domains for such a large number of sources and such high cadence. Also the observing systems and methods are introduced as well as the data reduction techniques. The thesis at hand is structured as follows: Chapter 3 presents the reduction methods and post measurement corrections applied to the data such as pointing offsets, gain--elevation and sensitivity corrections as well as specific corrections applied for each of the Effelsberg and Pico Veleta observing systems respectively. Chapter 4 presents the analysis tools and methods that were used such as: variability characteristics, flare amplitudes with a new method for

  2. The Gamma-Ray Blazar Quest: state of the art and future perspectives

    NASA Astrophysics Data System (ADS)

    Massaro, Francesco; Alvarez Crespo, Nuria; D'Abrusco, Raffaele; Landoni, Marco; Masetti, Nicola; Ricci, Federica; Milisavljevic, Dan; Paggi, Alessandro; Smith, Howard Alan

    2016-04-01

    In 2011 we discovered that gamma-ray blazars detected by Fermi show extremely peculiar infrared colors. On the basis of this discovery we developed a procedure that allowed us to recognize gamma-ray blazar candidates within the sources associated in the Fermi catalogs with an uncertain classification. We also built a method to search for blazar-like sources as potential counterpart of the unidentified gamma-ray sources (UGSs). However, to confirm the real nature of the selected candidates, optical spectroscopy is necessary. Thus, we started an optical spectroscopic campaign to observe the selected gamma-ray blazar candidates and unveil their origin. In this work we present the state-of-art of our observational campaign that allowed us to discover previously unknown gamma-ray blazars and a review of the results achieved to date. Future perspectives of our observing strategy developed to ''resolve the gamma-ray sky`` having all Fermi objects associated will be also discussed.

  3. The Extragalactic Background Light Absorption Feature in the Blazar Component of the Extragalactic Gamma-ray Background

    NASA Astrophysics Data System (ADS)

    Venters, Tonia M.; Pavlidou, Vasiliki; Reyes, Luis C.

    2009-10-01

    High-energy photons from cosmological emitters suffer attenuation due to pair production interactions with the extragalactic background light (EBL). The collective emission of any high-energy emitting cosmological population will exhibit an absorption feature at the highest energies. We calculate this absorption feature in the collective emission of blazars for various models of the blazar gamma-ray luminosity function (GLF) and the EBL. We find that models of the blazar GLF that predict higher relative contributions of high-redshift blazars to the blazar collective spectrum result in emission that is more susceptible to attenuation by the EBL, and hence result in more prominent absorption features, allowing for better differentiation amongst EBL models. We thus demonstrate that observations of such an absorption feature will contain information regarding both the blazar GLF and the EBL, and we discuss tests for EBL models and the blazar GLF that will become possible with upcoming Fermi observations.

  4. Long-term Multiwavelength Observations of Polars

    NASA Astrophysics Data System (ADS)

    Santana, Joshua; Mason, Paul A.

    2016-06-01

    Polars are cataclysmic variables with the highest magnetic field strengths (10-250 MG). Matter is accreted after being funneled by the strong magnetic field of the white dwarf. We perform a meta-study of multi-wavelength data of polars. Many polars have been observed in surveys, such as SDSS, 2MASS, ROSAT, just to name a few. Some polars have now been detected by the JVLA, part of an expanding class of radio CVs. A large subset of polars have long-term optical light curves from CRTS and AAVSO. We suggest that the long term light curves of polars display a variety of signature behaviors and may be grouped accordingly. Additional characteristics such a binary period, magnetic field strengths, X-ray properties, and distance estimates are examined in context with long-term observations.

  5. Gx 13+1: a Multiwavelength Campaign

    NASA Astrophysics Data System (ADS)

    Smale, Alan

    Despite being one of the seven brightest persistent X-ray sources in the Galactic bulge, little is definitively known about GX13+1. Its spectral behavior appears to identify it as an atoll source, however the brightness of its IR counterpart (K=12), long candidate orbit period (19.5 hrs, based on our previous IR work), and radio emission indicate a giant companion and a system size and behavior more typical of a Z-source. (Other candidate periods of 1.4 dy, 3.6 dy, and 25/50 dy do nothing to dispel the mystery.) We propose a multiwavelength campaign of observations of GX13+1 using RXTE and the CTIO 1.5m to study possible correlated variability in the X-ray/IR bands, orbital variations and fast time variability, and perform a detailed spectral study of this enigmatic source.

  6. Evidence for Two Lognormal States in Multi-wavelength Flux Variation of FSRQ PKS 1510-089

    NASA Astrophysics Data System (ADS)

    Kushwaha, Pankaj; Chandra, Sunil; Misra, Ranjeev; Sahayanathan, S.; Singh, K. P.; Baliyan, K. S.

    2016-05-01

    We present a systematic characterization of multi-wavelength emission from blazar PKS 1510-089 using well-sampled data at near-infrared (NIR), optical, X-ray, and γ-ray energies. The resulting flux distributions, except at X-rays, show two distinct lognormal profiles corresponding to a high and a low flux level. The dispersions exhibit energy-dependent behavior except in the LAT γ-ray and optical B-band. During the low level flux states, it is higher toward the peak of the spectral energy distribution, with γ-ray being intrinsically more variable followed by IR and then optical, consistent with mainly being a result of varying bulk Lorentz factor. On the other hand, the dispersions during the high state are similar in all bands except the optical B-band, where thermal emission still dominates. The centers of distributions are a factor of ∼4 apart, consistent with anticipation from studies of extragalactic γ-ray background with the high state showing a relatively harder mean spectral index compared to the low state.

  7. MULTIWAVELENGTH TRANSMISSOMETER FOR MEASURING MASS CONCENTRATION OF PARTICULATE EMISSIONS

    EPA Science Inventory

    A multiwavelength transmissometer potentially capable of making near-real-time measurements of particulate mass concentration in industrial stacks was developed. A computer program is employed to interpret the transmissometer data and translate the results into mass concentration...

  8. Programmable select multiwavelength gigahertz Raman soliton pulse generation.

    PubMed

    Kato, Masao; Fujiura, Kazuo; Kurihara, Takashi

    2004-10-10

    The generation of programmable multiwavelength pulses based on the self-frequency shift of a Raman soliton is demonstrated. The approach produces tunable multiwavelength picosecond pulses. Only select multiwavelength signals with a tuning range of approximately 50 nm are generated with a repetition rate of 9.95 GHz at each wavelength channel. A bit error rate (BER) of better than 1 x 10(-9) was successfully obtained for all the measured multiwavelength Raman soliton pulses. Furthermore, it was found that the signal has an excellent relative intensity noise (RIN) of better than -135.5 dBc/Hz. The BER and RIN measurements show that the frequency-shifted Raman soliton pulses are promising for use in measurement systems, optical gating, signal processing, and wavelength routing optical packet networks with the ability to provide 1:1 communication and 1:N multicasting. PMID:15508605

  9. PKS 1502+106: A high-redshift Fermi blazar at extreme angular resolution. Structural dynamics with VLBI imaging up to 86 GHz

    NASA Astrophysics Data System (ADS)

    Karamanavis, V.; Fuhrmann, L.; Krichbaum, T. P.; Angelakis, E.; Hodgson, J.; Nestoras, I.; Myserlis, I.; Zensus, J. A.; Sievers, A.; Ciprini, S.

    2016-02-01

    Context. Blazars are among the most energetic objects in the Universe. In 2008 August, Fermi/LAT detected the blazar PKS 1502+106, which showed a rapid and strong γ-ray outburst followed by high and variable flux over the next months. This activity at high energies triggered an intensive multi-wavelength campaign that also covered the radio, optical, UV, and X-ray bands, indicating that the flare was accompanied by a simultaneous outburst at optical/UV/X-rays and a delayed outburst at radio bands. Aims: We explore the phenomenology and physical conditions within the ultra-relativistic jet of the γ-ray blazar PKS 1502+106. Additionally, we address the question of the spatial localization of the MeV/GeV-emitting region of the source. Methods: We used ultra-high angular resolution mm-VLBI observations at 43 and 86 GHz complemented by VLBI observations at 15 GHz. We also employed single-dish radio data from the F-GAMMA program at frequencies matching the VLBI monitoring. Results: PKS 1502+106 shows a compact core-jet morphology and fast superluminal motion with apparent speeds in the range 5-22 c. Estimating Doppler factors along the jet yields values of between ~7 up to ~50. This Doppler factor gradient implies an accelerating jet. The viewing angle towards the source differs between the inner and outer jet, with the former at θ ~ 3° and the latter at θ ~ 1°, after the jet bends towards the observer beyond 1 mas. The de-projected opening angle of the ultra-fast magnetically dominated jet is found to be (3.8 ± 0.5)°. A single jet component can be associated with the pronounced flare both at high energies and in radio bands. Finally, the γ-ray emission region is localized at ≤ 5.9 pc away from the jet base. Images as FITS files are only available at the CDS via anonymous ftp to http://cdsarc.u-strasbg.fr (ftp://130.79.128.5) or via http://cdsarc.u-strasbg.fr/viz-bin/qcat?J/A+A/586/A60

  10. X-RAY AND RADIO FOLLOW-UP OBSERVATIONS OF HIGH-REDSHIFT BLAZAR CANDIDATES IN THE FERMI-LAT UNASSOCIATED SOURCE POPULATION

    SciTech Connect

    Takahashi, Y.; Kataoka, J.; Nakamori, T.; Maeda, K.; Niinuma, K.; Honma, M.; Inoue, Y.; Totani, T.; Inoue, S.

    2013-08-10

    We report on the results of X-ray and radio follow-up observations of two GeV gamma-ray sources 2FGL J0923.5+1508 and 2FGL J1502.1+5548, selected as candidates for high-redshift blazars from unassociated sources in the Fermi Large Area Telescope Second Source Catalog. We utilize the Suzaku satellite and the VLBI Exploration of Radio Astrometry (VERA) telescopes for X-ray and radio observations, respectively. For 2FGL J0923.5+1508, a possible radio counterpart NVSS J092357+150518 is found at 1.4 GHz from an existing catalog, but we do not detect any X-ray emission from it and derive a flux upper limit F{sub 2-8{sub keV}} < 1.37 Multiplication-Sign 10{sup -14} erg cm{sup -2} s{sup -1}. Radio observations at 6.7 GHz also result in an upper limit of S{sub 6.7{sub GHz}} < 19 mJy, implying a steep radio spectrum that is not expected for a blazar. On the other hand, we detect X-rays from NVSS J150229+555204, the potential 1.4 GHz radio counterpart of 2FGL J1502.1+5548. The X-ray spectrum can be fitted with an absorbed power-law model with a photon index {gamma} = 1.8{sup +0.3}{sub -0.2} and the unabsorbed flux is F{sub 2-8{sub keV}} = 4.3{sup +1.1}{sub -1.0} Multiplication-Sign 10{sup -14} erg cm{sup -2} s{sup -1}. Moreover, we detect unresolved radio emission at 6.7 GHz with flux S{sub 6.7{sub GHz}} = 30.1 mJy, indicating a compact, flat-spectrum radio source. If NVSS J150229+555204 is indeed associated with 2FGL J1502.1+5548, then we find that its multiwavelength spectrum is consistent with a blazar at redshift z {approx} 3-4.

  11. The Spectral Energy Distribution of Fermi Bright Blazars

    NASA Technical Reports Server (NTRS)

    Abdo, A. A.; Ackermann, M.; Agudo, I.; Ajello, M.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Arkharov, A. A.; Axelsson, M.; Bach, U.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Baughman, B. M.; Bechtol, K.; Bellazzini, R.; Benitiez, E.; Berdyugin, A.; Gehrels, N.; Harding, A. K.; Hays, E.; Marshall, F.; Scargle, J. D.; Thompson, D. J.

    2010-01-01

    We have conducted a detailed investigation of the broadband spectral properties of the gamma-ray selected blazars of the Fermi LAT Bright AGN Sample (LBAS). By combining our accurately estimated Fermi gamma-ray spectra with Swift, radio, infra-red, optical, and other hard X-ray /gamma-ray data, collected within 3 months of the LBAS data taking period, we were able to assemble high-quality and quasi-simultaneous spectral energy distributions (SED) for 48 LBAS blazars. The SED of these gamma-ray sources is similar to that of blazars discovered at other wavelengths, clearly showing, in the usual log v-log v Fv representation, the typical broadband spectral signatures normally attributed to a combination of low-energy synchrotron radiation followed by inverse Compton emission of one or more components. We have used these SED to characterize the peak intensity of both the low- and the high-energy components. The results have been used to derive empirical relationships that estimate the position of the two peaks from the broadband colors (i.e., the radio to optical, alpha(sub ro) , and optical to X-ray, alpha(sub ox), spectral slopes) and from the gamma-ray spectral index. Our data show that the synchrotron peak frequency (v(sup S) (sub peak)) is positioned between 10(exp 12.5) and 10(exp 14) Hz in broad-lined flat spectrum radio quasars (FSRQs) and between 10(exp 13) and 10(exp 17) Hz in featureless BL Lacertae objects. We find that the gamma-ray spectral slope is strongly correlated with the synchrotron peak energy and with the X-ray spectral index, as expected at first order in synchrotron-inverse Compton scenarios. However, simple homogeneous, one-zone, synchrotron self-Compton (SSC) models cannot explain most of our SED, especially in the case of FSRQs and low energy peaked (LBL) BL Lacs. More complex models involving external Compton radiation or multiple SSC components are required to reproduce the overall SED and the observed spectral variability. While more than

  12. High-brightness switchable multiwavelength remote laser in air

    SciTech Connect

    Yao Jinping; Cheng Ya; Xu Zhizhan; Zeng Bin; Li Guihua; Chu Wei; Ni Jielei; Zhang Haisu; Xu Huailiang; Chin, See Leang

    2011-11-15

    We demonstrate a harmonic-seeded switchable multiwavelength laser in air driven by intense midinfrared femtosecond laser pulses, in which population inversion occurs at an ultrafast time scale (i.e., less than {approx}200 fs) owing to direct formation of excited molecular nitrogen ions by strong-field ionization of inner-valence electrons. The bright multiwavelength laser in air opens the perspective for remote detection of multiple pollutants based on nonlinear optical spectroscopy.

  13. Short-term VHE variability in blazars: PKS 2155-304

    NASA Astrophysics Data System (ADS)

    Rieger, F. M.; Volpe, F.

    2010-09-01

    Context. The γ-ray blazar PKS 2155-304 has attracted considerable attention because of its extreme TeV variability characteristics during an exceptional flaring period in 2006. Among the observed key findings are (i) a minimum variability timescale as short as ~200 s and (ii) highly variable TeV emission, which in the frequency interval [ 10-4 Hz, 10-2 Hz] can be described by a log-normal distribution and suggests an underlying multiplicative (and not additive) process. Aims: Simultaneously accounting for these findings appears difficult within conventional approaches. Following earlier suggestions for the TeV blazar Mkn 501, we explore a possible scenario where PKS 2155-304 is supposed to harbor a supermassive binary black hole system and where the observed TeV variability is dominated by emission from the less massive black hole. Methods: We analyze the constraints on the very high energy (VHE) source imposed by the observed variability characteristics and the integrated VHE luminosity output, and discuss its implications for a binary black hole system. Results: We show that for a secondary mass of mBH ~ 107 M⊙, fluctuations in the disk accretion rate that feed the jet could account for the observed red-noise type variability process down to frequencies of ~10-2 Hz. Jet curvature induced by orbital motion, on the other hand, could further relax constraints on the intrinsic jet speeds. Conclusions: Because a binary system can lead to different (yet not independent) periodicities in different energy bands, a longterm (quasi-) periodicity analysis could offer important insights into the real nature of the central engine of PKS 2155-304.

  14. Leptonic and Hadronic Modeling of Fermi-detected Blazars

    NASA Astrophysics Data System (ADS)

    Böttcher, M.; Reimer, A.; Sweeney, K.; Prakash, A.

    2013-05-01

    We describe new implementations of leptonic and hadronic models for the broadband emission from relativistic jets in active galactic nuclei in a temporary steady state. For the leptonic model, a temporary equilibrium between particle injection/acceleration, radiative cooling, and escape from a spherical emission region is evaluated, and the self-consistent radiative output is calculated. For the hadronic model, a temporary equilibrium between particle injection/acceleration, radiative and adiabatic cooling, and escape is evaluated for both primary electrons and protons. A new, semianalytical method to evaluate the radiative output from cascades initiated by internal γγ pair production is presented. We use our codes to fit snapshot spectral energy distributions (SEDs) of a representative set of Fermi-LAT-detected blazars. We find that the leptonic model provides acceptable fits to the SEDs of almost all blazars with parameters close to equipartition between the magnetic field and the relativistic electron population. However, the hard γ-ray spectrum of AO 0235+164, in contrast to the very steep IR-optical-UV continuum, poses a severe problem for the leptonic model. If charge neutrality in leptonic models is provided by cold protons, the kinetic energy carried by the jet should be dominated by protons. We find satisfactory representations of the snapshot SEDs of most blazars in our sample with the hadronic model presented here. However, in the case of two quasars the characteristic break at a few GeV energies cannot be well modeled. All of our hadronic model fits require powers in relativistic protons in the range Lp ~ 1047-1049 erg s-1.

  15. Multiwavelength videomicrofluorometry for multiparametric investigations of multidrug resistance

    NASA Astrophysics Data System (ADS)

    Rocchi, Emmanuelle; Salmon, Jean-Marie; Vigo, Jean; Viallet, Pierre M.

    1996-05-01

    A major problem in the cancer chemotherapy is the development of resistance to a whole range of drugs not only similar to the drugs used for resistance induction but also to some functionally and structurally unrelated. It's one of the multifactorial causes of failure of chemotherapy. Thus it appears essential to evaluate the multi-drug resistance (MDR) in living cells populations to: detect the MDR phenotype, to discriminate between resistant and sensitive cells, to identify mechanisms which are involved in the induction or the reversion of resistance and to study the cytotoxic process. Such a challenge implies the use of multiparametric approach that has been possible using a protocol involving microfluorometry connected to numerical image analysis on single living cells. This protocol relays on the correlation existing between the decreased intracellular accumulation of some fluorescent probes such as Hoechst 33342 (Ho342) and Rhodamine 123 (R123) in resistant cells. The simultaneous estimation of the fluorescence intensities of these probes has required the use of a third probe, the Nile Red, for cell contour delineation. The analysis of parameters related to Ho342 and R123 allows the discrimination of sensitive and resistant cells. So the multiparametric approach using multi-wavelength image analysis, which appears to be a powerful technique, has allowed us to show on human lymphoblastoid CCRF-CEM cells lines that the cytotoxic effects could be different depending on the cell resistance or on the cytotoxic drug used: Adriamycine, Vinblastine and the different cell behavior could be used for cell differentiation.

  16. Lorentz factor distribution of blazars from the optical Fundamental Plane of black hole activity

    NASA Astrophysics Data System (ADS)

    Saikia, Payaswini; Körding, Elmar; Falcke, Heino

    2016-09-01

    Blazar radiation is dominated by a relativistic jet which can be modelled at first approximation using just two intrinsic parameters - the Lorentz factor Γ and the viewing angle θ. Blazar jet observations are often beamed due to relativistic effects, complicating the understanding of these intrinsic properties. The most common way to estimate blazar Lorentz factors needs the estimation of apparent jet speeds and Doppler beaming factors. We present a new and independent method of constructing the blazar Lorentz factor distribution, using the optical Fundamental Plane of black hole activity. The optical Fundamental Plane is a plane stretched out by both the supermassive black holes and the X-ray binaries, in the 3D space provided by their [O III] line luminosity, radio luminosity and black hole mass. We use the intrinsic radio luminosity obtained from the optical Fundamental Plane to constrain the boosting parameters of the VLBA Imaging and Polarimetry Survey blazar sample. We find a blazar bulk Lorentz factor distribution in the form of a power law as N(Γ) ∝ Γ-2.1 ± 0.4 for the Γ range of 1-40. We also discuss the viewing angle distribution of the blazars and the dependence of our results on the input parameters.

  17. Doubling the Sample of Jet Speed Measurements for the TeV Blazars

    NASA Astrophysics Data System (ADS)

    Piner, B. Glenn; Tiet, V. C.; Edwards, P. G.

    2011-05-01

    We report on our observations of the parsec-scale radio jet structures of five blazars that have been detected by ground-based TeV gamma-ray telescopes. These five blazars all belong to the class of High-frequency peaked BL Lac objects (HBLs), which are the most common blazar type detected at the TeV energy range. Because of their relative faintness in the radio, these HBLs are not well represented in other radio blazar surveys. Our observations consist of five epochs of Very Long Baseline Array (VLBA) imaging from 2006 to 2009, of each of the five blazars 1ES 1101-232, Markarian 180, 1ES 1218+304, PG 1553+113, and H 2356-309, at frequencies from 5 to 22 GHz. Fundamental jet properties, including the apparent jet speeds, that can be measured from these multi-epoch series of VLBA images are presented and compared with other gamma-ray blazars. This study approximately doubles the number of TeV blazars with multi-epoch parsec-scale structural measurements. This work was supported by the National Science Foundation under Grant 0707523.

  18. Lorentz factor distribution of blazars from the optical Fundamental plane of black hole activity

    NASA Astrophysics Data System (ADS)

    Saikia, Payaswini; Körding, Elmar; Falcke, Heino

    2016-06-01

    Blazar radiation is dominated by a relativistic jet which can be modeled at first approximation using just two intrinsic parameters - the Lorentz factor Γ and the viewing angle θ. Blazar jet observations are often beamed due to relativistic effects, complicating the understanding of these intrinsic properties. The most common way to estimate blazar Lorentz factors needs the estimation of apparent jet speeds and Doppler beaming factors. We present a new and independent method of constructing the blazar Lorentz factor distribution, using the optical fundamental plane of black hole activity. The optical fundamental plane is a plane stretched out by both the supermassive black holes and the X-ray binaries, in the 3D space provided by their [OIII] line luminosity, radio luminosity and black hole mass. We use the intrinsic radio luminosity obtained from the optical fundamental plane to constrain the boosting parameters of the VLBA Imaging and Polarimetry Survey (VIPS) blazar sample. We find a blazar bulk Lorentz factor distribution in the form of a power law as N(Γ)∝Γ-2.1 ± 0.4 for the Γ range of 1 to 40. We also discuss the viewing angle distribution of the blazars and the dependence of our results on the input parameters.

  19. 15 GHz Radio Variability of Gamma-Ray Blazars

    NASA Astrophysics Data System (ADS)

    Richards, Joseph; Max-Moerbeck, W.; Pavlidou, V.; Pearson, T. J.; Readhead, A. C. S.; Stevenson, M. A.; King, O. G.; Reeves, R.; Angelakis, E.; Fuhrmann, L.; Zensus, J. A.; Healey, S. E.; Romani, R. W.; Shaw, M. S.; Grainge, K.; Taylor, G. B.; Cotter, G.

    2011-01-01

    Since 2007, the Owens Valley Radio Observatory (OVRO) 40 meter telescope has been engaged in an intensive fast-cadence gamma-ray blazar monitoring program, observing about 1500 objects twice per week. Using our intrinsic modulation index method and careful likelihood analyses, we find that gamma-ray loud objects associated with Fermi 1LAC sources in our sample demonstrate radio variability amplitudes significantly larger than do gamma-ray quiet objects. We also find significant differences in variability amplitude between flat spectrum radio quasars and BL Lacertae objects within our sample as well as possible evidence for cosmological evolution of variability amplitude.

  20. High-energy neutrinos from photomeson processes in blazars.

    PubMed

    Atoyan, A; Dermer, C D

    2001-11-26

    An important radiation field for photomeson neutrino production in blazars is shown to be the radiation field external to the jet. Assuming that protons are accelerated with the same power as electrons and injected with a -2 number spectrum, we predict that km(2) neutrino telescopes will > or similar to 1 neutrinos per year from flat spectrum radio quasars such as 3C 279. The escaping high-energy neutron and photon beams transport inner jet energy far from the black-hole engine, and could power synchrotron x-ray jets and FR II hot spots and lobes. PMID:11736392

  1. Infrared variability properties of the blazar 3C 279

    NASA Astrophysics Data System (ADS)

    Fan, J. H.

    1999-10-01

    The long-term (about 27 years) near-infrared K light curve is constructed from the published literature for the blazar 3C 279. The Jurkevich method is adopted to analyse the periodicity, and a strong 7.1+/-0.44yr period is found, suggesting that the next near-infrared outburst will occur in 2002/03. The correlation between colour index (spectral index) and magnitude is discussed, and a significant correlation between (J-H) and K is found with a correlation coefficient r=0.72 (p=2.0x10^-10), which is consistent with Brown et al.'s proposal.

  2. Photopolarimetry of Blazar 3C454.3 from MIRO

    NASA Astrophysics Data System (ADS)

    Baliyan, Ks; Ganesh, S.; Chandra, Sunil; Joshi, Uc

    2009-12-01

    The Blazar 3C 454.3 has been active in Gamma-rays, optical and X- rays since Sept. 2009 ( Atel #2181, #2200, #2201). Very recently, it has been reported to be flaring up in the optical, X-ray and gamma-ray energy regimes(ATel #2322; #2325; #2326; #2328; #2329; #2330; #2332). In Atel #2333, Sasada et al report optical behaviour of this source on Dec 1.9 with brightness (V=14.06+/-0.02 and degree of polarization 6.0+/-0.1% on the same epoch.

  3. M 87 as a misaligned synchrotron-proton blazar

    NASA Astrophysics Data System (ADS)

    Reimer, A.; Protheroe, R. J.; Donea, A.-C.

    2004-05-01

    The giant radio galaxy M 87 is usually classified as a Fanaroff-Riley class I source, suggesting that M 87 is a mis-aligned BL Lac object. Its unresolved nuclear region emits strong non-thermal emission from radio to X-rays which has been interpreted as synchrotron radiation. In an earlier paper we predicted M 87 as a source of detectable gamma ray emission in the context of the hadronic Synchrotron-Proton Blazar (SPB) model. The subsequent tentative detection of TeV energy photons by the HEGRA-telescope array would, if confirmed, make it the first radio galaxy to be detected at TeV-energies. We discuss the emission from the unresolved nuclear region of M 87 in the context of the SPB model, and give examples of possible model representations of its non-simultaneous spectral energy distribution. The low-energy component can be explained as synchrotron radiation by a primary relativistic electron population that is injected together with energetic protons into a highly magnetized emission region. We find that the γ-ray power output is dominated either by μ±/π± synchrotron or proton synchrotron radiation depending on whether the primary electron synchrotron component peaks at low or high energies, respectively. The predicted γ-ray luminosity peaks at ˜100 GeV at a level comparable to that of the low-energy hump, and this makes M 87 a promising candidate source for the newly-commissioned high-sensitivity low-threshold Cherenkov telescopes H.E.S.S., VERITAS, MAGIC and CANGAROO III. Because of its proximity, the high-energy spectrum of M 87 is unaffected by absorption in the cosmic infrared (IR) background radiation field, and could therefore serve as a template spectrum for the corresponding class of blazar if corrected for mis-alignment effects. This could significantly push efforts to constrain the cosmic IR radiation field through observation of more distant TeV-blazars, and could have a strong impact on blazar emission models. If M 87 is a mis-aligned BL

  4. HELP: The Herschel Extragalactic Legacy Project and The Coming of Age of Multi-wavelength Astrophysics

    NASA Astrophysics Data System (ADS)

    Vaccari, M.

    How did galaxies form and evolve? This is one of the most challenging questions in astronomy today. Answering it requires a careful combination of observational and theoretical work to reliably determine the observed properties of cosmic bodies over large portions of the distant Universe on the one hand, and accurately model the physical processes driving their evolution on the other. Most importantly, it requires bringing together disparate multi-wavelength and multi-resolution spectro-photometric datasets in an homogeneous and well-characterized manner so that they are suitable for a rigorous statistical analysis. The Herschel Extragalactic Legacy Project (HELP) funded by the EC FP7 SPACE program aims to achieve this goal by combining the expertise of optical, infrared and radio astronomers to provide a multi-wavelength database for the distant Universe as an accessible value-added resource for the astronomical community. It will do so by bringing together multi-wavelength datasets covering the 1,000 deg2 mapped by Herschel extragalactic surveys in an homogeneous and well-characterized manner, creating a joint lasting legacy from several ambitious sky surveys.

  5. The VHE gamma-ray spectra of several hard-spectrum blazars from long-term observations with the VERITAS telescope array

    NASA Astrophysics Data System (ADS)

    Madhavan, Arun

    2013-08-01

    Analysis is presented on VERITAS observations of the very high energy gamma-ray spectra of five high frequency peaked BL Lac objects over a range of redshifts. Each object has an unusually hard intrinsic GeV spectrum, and is expected to produce TeV gamma-ray emission into the optically- thick regime of the universe's diffuse extragalactic background light (EBL). Hard spectrum HBLs have recently emerged as an effective tool for measurement of the EBL spectrum, due to extinction of gamma-ray signals from blazars via the pair production interaction gamma-TeVgamma EBL → e+e -. The VERITAS collaboration has approved long term observations on several of these sources, with the specific intent of studying their spectra to probe for absorption features resulting from these interactions. An introduction to the field of particle astrophysics is presented, followed by an overview of the EBL and its relation to the evolution of the universe. The VERITAS gamma-ray telescope is described in detail, followed by a full overview of the analysis techniques used to derive gamma-ray spectra from VERITAS data. The analyses of the blazars themselves are presented, followed by a discussion of their application to further constraints of the EBL. Each blazar is de-absorbed with an assumed EBL spectrum. In each case the intrinsic TeV spectrum is consistent with lower-energy gamma-ray emission in the optically-thin regime of the EBL.

  6. RCT photometry and HCT spectroscopy of blazar candidates in the Kepler field of view

    NASA Astrophysics Data System (ADS)

    Carini, Michael T.; Goyal, A.; Jose, J.

    2014-01-01

    The results of photometric and spectroscopic monitoring of 9 blazar candidates in the Kepler field of view are presented. These sources were identified as blazar candidates based on their position in the so-called WISE blazar strip. Finding charts and comparison sequences were created using the NOMAD database. R band photometric monitoring was begun in spring 2013 with the Robotically Controlled Telescope(RCT), and spectroscopic observations of 7 of the sources were obtained with the Himalayan Chandra Telescope (HCT) in September, 2013. Light curves for all 9 sources and preliminary spectroscopic classifications for the 7 sources with spectra will be presented.

  7. On the origin of the soft photons of the high-synchrotron-peaked blazar PKS 1424+240

    NASA Astrophysics Data System (ADS)

    Kang, Shi-Ju; Zheng, Yong-Gang; Wu, Qingwen; Chen, Liang

    2016-09-01

    PKS 1424+240 is a distant very-high-energy gamma-ray BL Lac object with redshift z = 0.601. It has been found that models utilizing pure synchrotron self-Compton (SSC) processes normally need extreme input parameters (e.g. a very low magnetic field intensity and an extraordinarily high Doppler factor) to explain this particular object spectral energy distributions (SEDs). In order to avoid these extreme model parameters, various other models have been proposed (e.g. the two-zone SSC model or lepto-hadronic model). In this work, we employ the traditional one-zone leptonic model after including a weak external Compton component in order to explore the simultaneous multiwavelength SEDs of PKS 1424+240 in both the high (2009) and the low (2013) state. We find that the input parameters of the magnetic field and Doppler factor are roughly consistent with those of other BL Lacs if a weak external photon field from either the broad line region (BLR) or the dust torus is assumed. However, the required energy density of seed photons from the BLR or torus is about three orders of magnitude lower than that the energy density estimated from the observations in luminous quasars (e.g. flat-spectrum radio quasars, FSRQs). This result suggests that the BLR/torus in BL Lacs is much weaker than that of luminous FSRQs (but has not fully disappeared), and that the inverse-Compton process of external photons from the BLR/torus may still play a role even in high-synchrotron-peaked blazars.

  8. Blazars as Ultra-high-energy Cosmic-ray Sources: Implications for TeV Gamma-Ray Observations

    NASA Astrophysics Data System (ADS)

    Murase, Kohta; Dermer, Charles D.; Takami, Hajime; Migliori, Giulia

    2012-04-01

    The spectra of BL Lac objects and Fanaroff-Riley I radio galaxies are commonly explained by the one-zone leptonic synchrotron self-Compton (SSC) model. Spectral modeling of correlated multiwavelength data gives the comoving magnetic field strength, the bulk outflow Lorentz factor, and the emission region size. Assuming the validity of the SSC model, the Hillas condition shows that only in rare cases such sources accelerate protons to much above 1019 eV, so >~ 1020 eV ultra-high-energy cosmic rays (UHECRs) are likely to be heavy ions if powered by this type of radio-loud active galactic nuclei (AGNs). Survival of nuclei is shown to be possible in TeV BL Lacs and misaligned counterparts with weak photohadronic emissions. Another signature of hadronic production is intergalactic UHECR-induced cascade emission, which is an alternative explanation of the TeV spectra of some extreme non-variable blazars such as 1ES 0229+200 or 1ES 1101-232. We study this kind of cascade signal, taking into account effects of the structured extragalactic magnetic fields in which the sources should be embedded. We demonstrate the importance of cosmic-ray deflections on the γ-ray flux, and show that required absolute cosmic-ray luminosities are larger than the average UHECR luminosity inferred from UHECR observations and can even be comparable to the Eddington luminosity of supermassive black holes. Future TeV γ-ray observations using the Cerenkov Telescope Array and the High Altitude Water Cerenkov detector array can test for UHECR acceleration by observing >25 TeV photons from relatively low redshift sources such as 1ES 0229+200, and gsimTeV photons from more distant radio-loud AGNs.

  9. BLAZARS AS ULTRA-HIGH-ENERGY COSMIC-RAY SOURCES: IMPLICATIONS FOR TeV GAMMA-RAY OBSERVATIONS

    SciTech Connect

    Murase, Kohta; Dermer, Charles D.; Takami, Hajime; Migliori, Giulia

    2012-04-10

    The spectra of BL Lac objects and Fanaroff-Riley I radio galaxies are commonly explained by the one-zone leptonic synchrotron self-Compton (SSC) model. Spectral modeling of correlated multiwavelength data gives the comoving magnetic field strength, the bulk outflow Lorentz factor, and the emission region size. Assuming the validity of the SSC model, the Hillas condition shows that only in rare cases such sources accelerate protons to much above 10{sup 19} eV, so {approx}> 10{sup 20} eV ultra-high-energy cosmic rays (UHECRs) are likely to be heavy ions if powered by this type of radio-loud active galactic nuclei (AGNs). Survival of nuclei is shown to be possible in TeV BL Lacs and misaligned counterparts with weak photohadronic emissions. Another signature of hadronic production is intergalactic UHECR-induced cascade emission, which is an alternative explanation of the TeV spectra of some extreme non-variable blazars such as 1ES 0229+200 or 1ES 1101-232. We study this kind of cascade signal, taking into account effects of the structured extragalactic magnetic fields in which the sources should be embedded. We demonstrate the importance of cosmic-ray deflections on the {gamma}-ray flux, and show that required absolute cosmic-ray luminosities are larger than the average UHECR luminosity inferred from UHECR observations and can even be comparable to the Eddington luminosity of supermassive black holes. Future TeV {gamma}-ray observations using the Cerenkov Telescope Array and the High Altitude Water Cerenkov detector array can test for UHECR acceleration by observing >25 TeV photons from relatively low redshift sources such as 1ES 0229+200, and {approx}>TeV photons from more distant radio-loud AGNs.

  10. Multi-wavelength follow-up of ANTARES neutrino alerts

    NASA Astrophysics Data System (ADS)

    Mathieu, Aurore

    2015-10-01

    Transient sources are often associated with the most violent phenomena in the Universe, where the acceleration of hadrons may occur. Such sources include gamma-ray bursts (GRBs), active galactic nuclei (AGN) or core-collapse supernovae (CCSNe), and are promising candidates for the production of high energy cosmic rays and neutrinos. The ANTARES telescope, located in the Mediterranean sea, aims at detecting these high energy neutrinos, which could reveal the presence of a cosmic ray accelerator. However, to enhance the sensitivity to transient sources, a method based on multi-wavelength follow-up of neutrino alerts has been developed within the ANTARES collaboration. This program, denoted as TAToO, triggers a network of robotic optical telescopes and the Swift-XRT with a delay of only a few seconds after a neutrino detection. The telescopes start an observation program of the corresponding region of the sky in order to detect a possible electromagnetic counterpart to the neutrino event. The work presented in this thesis covers the development and implementation of an optical image analysis pipeline, as well as the analysis of optical and X-ray data to search for fast transient sources, such as GRB afterglows, and slowly varying transient sources, such as CCSNe.

  11. Electromagnetic cascades propagating from low-redshift blazars

    NASA Astrophysics Data System (ADS)

    Orellana, M.; Pellizza, L. J.; Romero, G. E.; Tueros, M.; Medina, M. C.; Pedrosa, S. E.

    2015-08-01

    It has been established that the Extragalactic Background Light attenuates the very high-energy photons emitted by blazars through pair production. The pairs are deflected by the Extragalactic Magnetic Field (EGMF) and cooled down by Inverse Compton scattering with the Cosmic Microwave Background (CMB) photons while they develop an electromagnetic cascade. The EGMF may also take out energy from the pairs in the form of synchrotron radiation. The originally emitted spectrum, the source extent and the arriving time of the photons are modified by such cascades. In order to study this problem we assume the blazar original emission to follow a power-law with exponential cutoff, and track the three-dimensional trajectories of each particle and photon in the cascade. In this work we describe the results of numerical simulations regarding the -ray propagation through Mpc scales, making focus on the construction of the outcoming spectrum which results from the energy conservation and thus combines the information from the different channels of energy losses. Different spectra arise when varying the EGMF strength.

  12. Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope

    NASA Astrophysics Data System (ADS)

    The ANTARES Collaboration

    2015-12-01

    The ANTARES telescope is well-suited for detecting astrophysical transient neutrino sources as it can observe a full hemisphere of the sky at all times with a high duty cycle. The background due to atmospheric particles can be drastically reduced, and the point-source sensitivity improved, by selecting a narrow time window around possible neutrino production periods. Blazars, being radio-loud active galactic nuclei with their jets pointing almost directly towards the observer, are particularly attractive potential neutrino point sources, since they are among the most likely sources of the very high-energy cosmic rays. Neutrinos and gamma rays may be produced in hadronic interactions with the surrounding medium. Moreover, blazars generally show high time variability in their light curves at different wavelengths and on various time scales. This paper presents a time-dependent analysis applied to a selection of flaring gamma-ray blazars observed by the FERMI/LAT experiment and by TeV Cherenkov telescopes using five years of ANTARES data taken from 2008 to 2012. The results are compatible with fluctuations of the background. Upper limits on the neutrino fluence have been produced and compared to the measured gamma-ray spectral energy distribution.

  13. Multiwavelength EDM measurements in southern California

    USGS Publications Warehouse

    Slater, L.E.; McGarr, A.; Langbein, J.O.; Linker, M.F.

    1983-01-01

    We installed a precise geodetic network along the San Andreas fault near Pearblossom, California in November, 1980. The network is within the region frequently referred to as the "Palmdale Uplift" and consists of 13 lines radiating from a central benchmark. The lines range in length from 3.2 to 8.1 km are generally measured several times each week. The multiwavelength distance measuring (MWDM) instrument is located at the central benchmark and is housed in a small protective shelter. The MWDM instrument has demonstrated a capability to make measurements to a precision of 1 part in 10 million. Using a coordinate system whose x-axis is parallel to the local trace of the San Andreas fault the following strain rates were observed during the first 10 months of this effort: {greater-than with dot}exx = -0.180 ?? 0.025 ??str/yr{greater-than with dot}eyy = -0.031 ?? 0.029 ??str/yr{greater-than with dot}exy = +0.077 ?? 0.024 ??str/yr?? = -0.213 ?? 0.039 ??str/yr. The observed strain rates do not appear to be constant in time, much of the deformation occurs in fairly well defined episodes. These changes in strain rate are particularly obvious in the \\ ??.geyy component. ?? 1983.

  14. Multiwavelength infrared focal plane array detector

    NASA Technical Reports Server (NTRS)

    Forrest, Stephen R. (Inventor); Olsen, Gregory H. (Inventor); Kim, Dong-Su (Inventor); Lange, Michael J. (Inventor)

    1995-01-01

    A multiwavelength focal plane array infrared detector is included on a common substrate having formed on its top face a plurality of In.sub.x Ga.sub.1-x As (x.ltoreq.0.53) absorption layers, between each pair of which a plurality of InAs.sub.y P.sub.1-y (y<1) buffer layers are formed having substantially increasing lattice parameters, respectively, relative to said substrate, for preventing lattice mismatch dislocations from propagating through successive ones of the absorption layers of decreasing bandgap relative to said substrate, whereby a plurality of detectors for detecting different wavelengths of light for a given pixel are provided by removing material above given areas of successive ones of the absorption layers, which areas are doped to form a pn junction with the surrounding unexposed portions of associated absorption layers, respectively, with metal contacts being formed on a portion of each of the exposed areas, and on the bottom of the substrate for facilitating electrical connections thereto.

  15. Recent Optical Transients Found by SNF/PQ: Possible Blazars and a Dwarf Nova

    NASA Astrophysics Data System (ADS)

    Djorgovski, S. G.; Nugent, P. E.; Glikman, E.; Mahabal, A.; Baltay, C.; Rabinowitz, D.

    2008-09-01

    Further to ATel #1694, additional transients found in the PQ data by the SNF pipeline, not associated with known radio sources, but possibly previously unidentified blazars, judging by their strong variability and blue colors, include:

  16. Renewed Gamma-Ray Emission from the blazar PKS 1510-089 Detected by AGILE

    NASA Astrophysics Data System (ADS)

    Munar-Adrover, P.; Pittori, C.; Bulgarelli, A.; Lucarelli, F.; Verrecchia, F.; Piano, G.; Fioretti, V.; Zoli, A.; Tavani, M.; Vercellone, S.; Minervini, G.; Striani, E.; Cardillo, M.; Gianotti, F.; Trifoglio, M.; Giuliani, A.; Mereghetti, S.; Caraveo, P.; Perotti, F.; Chen, A.; Argan, A.; Costa, E.; Del Monte, E.; Donnarumma, I.; Evangelista, Y.; Feroci, M.; Lazzarotto, F.; Lapshov, I.; Pacciani, L.; Soffitta, P.; Sabatini, S.; Vittorini, V.; Pucella, G.; Rapisarda, M.; Di Cocco, G.; Fuschino, F.; Galli, M.; Labanti, C.; Marisaldi, M.; Pellizzoni, A.; Pilia, M.; Trois, A.; Barbiellini, G.; Vallazza, E.; Longo, F.; Morselli, A.; Picozza, P.; Prest, M.; Lipari, P.; Zanello, D.; Cattaneo, P. W.; Rappoldi, A.; Colafrancesco, S.; Parmiggiani, N.; Ferrari, A.; Antonelli, A.; Giommi, P.; Salotti, L.; Valentini, G.; D'Amico, F.

    2016-09-01

    AGILE is currently detecting enhanced gamma-ray emission above 100 MeV from a source which position is consistent with the blazar PKS 1510-089. (the last activity of this source was reported in ATel #9350).

  17. Kronos: A Multiwavelength Observatory for Mapping Accretion-Driven Sources

    NASA Technical Reports Server (NTRS)

    Peterson, Bradley M.; Polidan, Ronald S.; Robinson, Edward L.

    2002-01-01

    Kronos is a multiwavelength observatory proposed as a NASA Medium Explorer. Kronos is designed to make use of the natural variability of accreting sources to create microarcsecond-resolution maps of the environments of supermassive black holes in active galaxies and stella-size black holes in binary systems and to characterize accretion processes in Galactic compact binaries. Kronos will obtain broad energy range spectroscopic data with co-aligned X-ray, ultraviolet, and optical spectrometers. The high-Earth orbit of Kronos enables well-sampled, high time-resolution observations, critical for the innovative and sophisticated methods that are used to understand the accretion flows, mass outflows, jets, and other phenomena found in accreting sources. By utilizing reverberation mapping analysis techniques, Kronos produces advanced high-resolution maps of unprecedented resolution of the extreme environment in the inner cores of active galaxies. Similarly, Doppler tomography and eclipse mapping techniques characterize and map Galactic binary systems, revealing the details of the physics of accretion processes in black hole, neutron star, and white dwarf binary systems. The Kronos instrument complement, sensitivity, and orbital environment make it suitable to aggressively address time variable phenomena in a wide range of astronomical objects from nearby flare stars to distant galaxies.

  18. MULTIWAVELENGTH PHOTOMETRY IN THE GLOBULAR CLUSTER M2

    SciTech Connect

    Dalessandro, E.; Lanzoni, B.; Ferraro, F.R.; Beccari, G.; Schiavon, R.; Rood, R.T.

    2009-06-15

    We present a multiwavelength photometric analysis of the globular cluster M2. The data set has been obtained by combining high-resolution (Hubble Space Telescope/WFPC2 and ACS) and wide-field (Galaxy Evolution Explorer) space observations and ground-based (MEGACAM-CFHT, EMMI-NTT) images. The photometric sample covers the entire cluster extension from the very central regions up to the tidal radius and beyond. It allows an accurate determination of the cluster center of gravity and other structural parameters derived from the star count density profile. Moreover, we study the Blue Straggler Star (BSS) population and its radial distribution. A total of 123 BSSs have been selected, and their radial distribution has been found to be bimodal (highly peaked in the center, decreasing at intermediate radii, and rising outward), as already found in a number of other clusters. The radial position of the minimum of the BSS distribution is consistent with the radius of avoidance caused by the dynamical friction of massive (1.2 M {sub sun}) objects over the cluster age. We also searched for gradients in the red giant branch (RGB) and the asymptotic giant branch (AGB) populations. At the 2{sigma} level, we found an overabundance of AGB stars within the core radius and confirmed the result of Sohn et al. that the central region of M2 is bluer than the outer part. We show that the latter is due to a deficit of very luminous RGB stars in the central region.

  19. Discovery of very high energy gamma-ray emission from the blazar 1ES 1727+502 with the MAGIC Telescopes

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Antonelli, L. A.; Antoranz, P.; Asensio, M.; Backes, M.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Boller, A.; Bonnefoy, S.; Bonnoli, G.; Borla Tridon, D.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Cossio, L.; Covino, S.; da Vela, P.; Dazzi, F.; de Angelis, A.; de Caneva, G.; de Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadamek, A.; Hadasch, D.; Häfner, D.; Herrero, A.; Hose, J.; Hrupec, D.; Idec, W.; Jankowski, F.; Kadenius, V.; Klepser, S.; Knoetig, M. L.; Krähenbühl, T.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Masbou, J.; Mazin, D.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moldón, J.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nowak, N.; Orito, R.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reichardt, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rügamer, S.; Saggion, A.; Saito, K.; Saito, T. Y.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Spiro, S.; Stamatescu, V.; Stamerra, A.; Steinke, B.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Weitzel, Q.; Zandanel, F.; Zanin, R.; MAGIC Collaboration

    2014-03-01

    Motivated by the prediction of a high TeV luminosity we investigated whether the blazar 1ES 1727+502 (z = 0.055) is emitting very high energy (VHE, E > 100 GeV) γ rays. We observed the BL Lac object 1ES 1727+502 in stereoscopic mode with the two MAGIC telescopes for 14 nights between May 6th and June 10th 2011, for a total effective observing time of 12.6 h. To study the multiwavelength spectral energy distribution (SED), we used simultaneous optical R-band data from the KVA telescope, archival UV/optical and X-ray observations from instruments UVOT and XRT on board of the Swift satellite, and high energy (HE, 0.1 GeV-100 GeV) γ-ray data from the Fermi-LAT instrument. We detected, for the first time, VHE γ-ray emission from 1ES 1727+502 at a statistical significance of 5.5σ. The integral flux above 150 GeV is estimated to be (2.1 ± 0.4)% of the Crab nebula flux and the de-absorbed VHE spectrum has a photon index of (2.7 ± 0.5). No significant short-term variability was found in any of the wavebands presented here. We model the SED using a one-zone synchrotron self-Compton model obtaining parameters typical for this class of sources.

  20. Optical follow-up of the blazar S5 2007+77

    NASA Astrophysics Data System (ADS)

    Nesci, Roberto

    2016-02-01

    Following the announcement of a Gamma-ray flare of the blazar S5 2007+77 (ATel #8635) by S. Cutini we observed the source with the 30cm telescope of the Foligno Observatory on 2016-02-05.77 UT. The blazar was detected at V=15.93+-0.05: three observations at 18 minutes intervals showed an appreciable decreasing trend of about 0.045 mag/hour.

  1. Theoretical and experimental investigation of multi-wavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Wo, Jianghai; Sun, Qizhen

    2009-08-01

    In this paper, a method for realizing a stable multi-wavelength EDFL at room temperature is analyzed theoretically and obtained experimentally. We have proposed a multi-wavelength fiber ring cavity laser by using EDF as the gain medium. A F-P and a band-pass filter are inserted into the cavity to achieve the selection of multi-wavelength. Meanwhile, by inserting a nonlinear optical loop mirror (NOLM) in the linear cavity, which can suppresses the mode competition owing to the homogeneous broaden line in EDF and eliminates the unstable single wavelength lasing, stable output can be obtained at room temperature. As a result, power-stable, broad bandwidth and uniform multi-wavelength operations with narrow line-width and high side mode suppression ratio are obtained at room temperature. In addition, we also demonstrate a kind of tunable multi-wavelength EDFL based on multi-channel FBG (M-FBG). Four-wavelength output with the flatness and SNR of almost 1dB and more than 50dB is achieved and the output wavelength can be changed by applying stress on the M-FBG.

  2. Spectacular variability of gamma-ray emission in blazar 3C279 during the large outburst in June 2015

    NASA Astrophysics Data System (ADS)

    Madejski, Grzegorz; Hayashida, Masaaki; Asano, Katsuaki; Thompson, David; Nalewajko, Krzysztof; Sikora, Marek; Fermi-LAT Collaboration

    2016-03-01

    The most luminous celestial extragalactic sources of persistent gamma-ray emission are active galaxies with relativistic jets pointing towards the observer. Those are commonly called blazars, and Flat Spectrum Radio Quasar 3C 279 has been one of the brightest gamma-ray blazars in the sky. In Dec. 2013, April 2014, and June 2015 it showed powerful outbursts with the gamma-ray flux at E > 100 MeV higher than 1e-5 ph/cm2/s, measured by the Fermi-LAT gamma-ray detector. The Dec. 2013 outburst showed an unusually hard power-law gamma-ray spectrum (photon index ~1.7), and an asymmetric light curve profile with a few-hour time scale variability. The June 2015 outburst was extreme, with a record-breaking E > 100 MeV flux of 4e-5 ph/cm2/s, more than 10 × higher than the average gamma-ray flux of the Crab Nebula. The high flux prompted a Fermi-LAT Target of Opportunity pointing observation. The increase of exposure and the very high flux state of the source allowed us to resolve the gamma-ray flux on a sub-orbital time scales, revealing variability on time scales of tens of minutes. Here, we present the observational results of those outbursts from 3C279 with a focus on detailed analysis of the 2015 June outburst.

  3. Fermi/LAT detection of extraordinary variability in the gamma-ray emission of the blazar PKS 1510-089

    NASA Astrophysics Data System (ADS)

    Foschini, L.; Bonnoli, G.; Ghisellini, G.; Tagliaferri, G.; Tavecchio, F.; Stamerra, A.

    2013-07-01

    We have reanalyzed the giant outburst of the blazar PKS 1510-089 (z = 0.36) that occurred on 2011 October-November. The γ-ray flux in the 0.1-100 GeV energy range exceeded the value of 10-5 ph cm-2 s-1 for several days. The peak flux was reached on 2011 October 19, with a value of ~4.4 × 10-5 ph cm-2 s-1, which in turn corresponds to a luminosity of ~2 × 1049 erg s-1. A very short timescale variability was measured. Particularly on 2011 October 18, the flux-doubling time was as short as ~20 min. This is the shortest variability ever detected in the MeV-GeV energy band. We compared our analysis with two other outbursts observed in 2009 March and 2012 February-March, when the blazar was also detected by H.E.S.S. and MAGIC to infer information about the emission at hundreds of GeV.

  4. HESS and Fermi-LAT discovery of γ-rays from the blazar 1ES 1312-423

    NASA Astrophysics Data System (ADS)

    HESS Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Giebels, B.; Glicenstein, J. F.; Göring, D.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hague, J. D.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Nedbal, D.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spieß, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.; Perkins, J. S.; Ojha, R.; Stevens, J.; Edwards, P. G.; Kadler, M.

    2013-09-01

    A deep observation campaign carried out by the High Energy Stereoscopic System (HESS) on Centaurus A enabled the discovery of γ-rays from the blazar 1ES 1312-423, 2° away from the radio galaxy. With a differential flux at 1 TeV of φ(1 TeV) = (1.9 ± 0.6stat ± 0.4sys) × 10-13 cm-2 s-1 TeV-1 corresponding to 0.5 per cent of the Crab nebula differential flux and a spectral index Γ = 2.9 ± 0.5stat ± 0.2sys, 1ES 1312-423 is one of the faintest sources ever detected in the very high energy (E > 100 GeV) extragalactic sky. A careful analysis using three and a half years of Fermi Large Area Telescope (Fermi-LAT) data allows the discovery at high energies (E > 100 MeV) of a hard spectrum (Γ = 1.4 ± 0.4stat ± 0.2sys) source coincident with 1ES 1312-423. Radio, optical, UV and X-ray observations complete the spectral energy distribution of this blazar, now covering 16 decades in energy. The emission is successfully fitted with a synchrotron self-Compton model for the non-thermal component, combined with a blackbody spectrum for the optical emission from the host galaxy.

  5. Collision-induced Magnetic Reconnection and a Unified Interpretation of Polarization Properties of GRBs and Blazars

    NASA Astrophysics Data System (ADS)

    Deng, Wei; Zhang, Haocheng; Zhang, Bing; Li, Hui

    2016-04-01

    The jet composition and energy dissipation mechanism of gamma-ray bursts (GRBs) and blazars are fundamental questions that remain not fully understood. One plausible model is to interpret the γ-ray emission of GRBs and optical emission of blazars as synchrotron radiation of electrons accelerated from the collision-induced magnetic dissipation regions in Poynting-flux-dominated jets. The polarization observation is an important and independent information to test this model. Based on our recent 3D relativistic MHD simulations of collision-induced magnetic dissipation of magnetically dominated blobs, here we perform calculations of the polarization properties of the emission in the dissipation region and apply the results to model the polarization observational data of GRB prompt emission and blazar optical emission. We show that the same numerical model with different input parameters can reproduce well the observational data of both GRBs and blazars, especially the 90° polarization angle (PA) change in GRB 100826A and the 180° PA swing in blazar 3C279. This supports a unified model for GRB and blazar jets, suggesting that collision-induced magnetic reconnection is a common physical mechanism to power the relativistic jet emission from events with very different black hole masses.

  6. SWIFT BURST ALERT TELESCOPE, FERMI LARGE AREA TELESCOPE, AND THE BLAZAR SEQUENCE

    SciTech Connect

    Sambruna, R. M.; Mushotzky, R. F.; Maraschi, L.

    2010-02-10

    Using public Fermi Large Area Telescope (LAT) and Swift Burst Alert Telescope observations, we constructed the first sample of blazars selected at both hard X-rays and gamma rays. Studying its spectral properties, we find a luminosity dependence of the spectral slopes at both energies. Specifically, luminous blazars, generally classified as flat spectrum radio quasars, have hard continua in the medium-hard X-ray range but soft continua in the LAT gamma-ray range (photon indices GAMMA{sub X} {approx}< 2 and GAMMA{sub G} {approx}> 2), while lower luminosity blazars, classified as BL Lacs, have opposite behavior, i.e., soft X-ray and hard gamma-ray continua (GAMMA{sub X} {approx}> 2.4 and GAMMA{sub G} < 2). The trends are confirmed by detailed Monte Carlo simulations explicitly taking into account the observational biases of both instruments. Our results support the so-called blazar sequence which was originally based on radio samples of blazars and radio luminosities. We also argue that the X-ray-to-gamma-ray continua of blazars may provide independent insights into the physical conditions around the jet, complementing/superseding the ambiguities of the traditional classification based on optical properties.

  7. Optical and radio variability in blazars

    NASA Technical Reports Server (NTRS)

    Hufnagel, Beth R.; Bregman, Joel N.

    1992-01-01

    An analysis is presented of the optical (0.44 micron) and radio flux density variations (4.8, 8.0, and 14.5 GHz) of the five best observed variable AGN, of which three are BL Lac objects and two are optically violent variable (OVV) quasars. For each object the nature of the variability at individual wavelengths is determined by using a structure function analysis and the autocorrelation function as calculated from the discrete correlation technique. Both techniques yield similar results, showing that the optical variations are similar for all objects and are a combination of flicker and shot noise. The radio variability is distinct, being described by shot noise (less variation at short times), with the two OVVs exhibiting the most extreme behavior. The time lag between the variations at the three radio frequencies and the optical flux is studied with the discrete cross-correlation function and the mean variance methods. It is concluded that the optical and radio emitting regions are physically related, exist on distinct time scales, and excite their synchrotron emitting plasmas differently.

  8. Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. V. TNG, KPNO, and OAN Observations of Blazar Candidates of Uncertain Type in the Northern Hemisphere

    NASA Astrophysics Data System (ADS)

    Álvarez Crespo, N.; Masetti, N.; Ricci, F.; Landoni, M.; Patiño-Álvarez, V.; Massaro, F.; D'Abrusco, R.; Paggi, A.; Chavushyan, V.; Jiménez-Bailón, E.; Torrealba, J.; Latronico, L.; La Franca, F.; Smith, Howard A.; Tosti, G.

    2016-02-01

    The extragalactic γ-ray sky is dominated by emission from blazars, a peculiar class of active galactic nuclei. Many of the γ-ray sources included in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs) because there are no optical spectra available in the literature to confirm their nature. In 2013, we started a spectroscopic campaign to look for the optical counterparts of the BCUs and of the unidentified γ-ray sources to confirm their blazar nature. Whenever possible we also determine their redshifts. Here, we present the results of the observations carried out in the northern hemisphere in 2013 and 2014 at the Telescopio Nazionale Galileo, Kitt Peak National Observatory, and Observatorio Astronómico Nacional in San Pedro Mártir. In this paper, we describe the optical spectra of 25 sources. We confirmed that all of the 15 BCUs observed in our campaign and included in our sample are blazars and we estimated the redshifts for three of them. In addition, we present the spectra for three sources classified as BL Lacs in the literature but with no optical spectra available to date. We found that one of them is a quasar (QSO) at a redshift of z = 0.208 and the other two are BL Lacs. Moreover, we also present seven new spectra for known blazars listed in the Roma-BZCAT that have an uncertain redshift or are classified as BL Lac candidates. We found that one of them, 5BZB J0724+2621, is a “changing look” blazar. According to the spectrum available in the literature, it was classified as a BL Lac, but in our observation we clearly detected a broad emission line that led us to classify this source as a QSO at z = 1.17.

  9. Multiwavelength data for bright active galaxies

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.; Abrahamyan, Hayk V.; Paronyan, Gurgen M.; Harutyunyan, Gohar S.

    2012-08-01

    The spectral energy distribution (SED) gives a complete picture of the radiation of space objects and may result in correct classifications compared to those based only on optical (or other local) spectra. This is especially crucial for active galaxies, both AGN and Starbursts (SB). For this, multiwavelength (MW) data are needed taken from available surveys and catalogs. We have cross-correlated the Catalogue of quasars and active galaxies with all-sky or large-area MW catalogues, such as X-ray ROSAT (BSC and FSC), UV GALEX (MIS and AIS), optical APM, MAPS, USNO-B1.0, GSC 2.3.2, and SDSS DR8, NIR 2MASS, MIR/FIR WISE, IRAS (PSC and FSC) and AKARI (IRC and FIS), radio GB6, NVSS, FIRST, and WENSS. We have established accurate positions and photometry for a few thousands of objects that appeared in the catalog with poor data, as well as achieved the best astrometric and photometric data for all objects. This allowed correct cross-correlations and establishing correct MW data for these objects. As a result, we obtained 34 photometric points from X-rays to radio and using VO tools built SEDs for some 10,000 bright objects. Some data from other surveys were also used, such as Chandra, XMM, Spitzer, etc. All objects were grouped into several forms of SED and were compared to the known optical classes given in the catalog (QSO, BLL, Sy1, Sy1.2-1.9, Sy2, LINER, SB, and HII). This allowed reveal obscured AGN, as well as find previously misclassified objects. A homogeneous classification for these objects was established. The first part of this project is presented; establishment of accurate positions and photometry and cross-correlations with MW catalogs.

  10. The 2009 multiwavelength campaign on Mrk 421: Variability and correlation studies

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Berger, K.; Bernardini, E.; Biland, A.; Blanch, O.; Bock, R. K.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Carreto Fidalgo, D.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; Delgado Mendez, C.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Farina, E.; Ferenc, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Giavitto, G.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadamek, A.; Hadasch, D.; Herrero, A.; Hildebrand, D.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Krause, J.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Longo, F.; Lombardi, S.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mankuzhiyil, N.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Meucci, M.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Niedzwiecki, A.; Nilsson, K.; Nowak, N.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Partini, S.; Persic, M.; Prada, F.; Prada Moroni, P. G.; Prandini, E.; Preziuso, S.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; RodriguezGarcia, J.; Rügamer, S.; Saggion, A.; Saito, K.; Salvati, M.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Spanier, F.; Stamatescu, V.; Stamerra, A.; Steinbring, T.; Storz, J.; Sun, S.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Tibolla, O.; Torres, D. F.; Toyama, T.; Treves, A.; Uellenbeck, M.; Vogler, P.; Wagner, R. M.; Zandanel, F.; Zanin, R.; MAGIC Collaboration; Archambault, S.; Behera, B.; Beilicke, M.; Benbow, W.; Bird, R.; Buckley, J. H.; Bugaev, V.; Cerruti, M.; Chen, X.; Ciupik, L.; Collins-Hughes, E.; Cui, W.; Dumm, J.; Eisch, J. D.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortin, P.; Fortson, L.; Furniss, A.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Hanna, D.; Holder, J.; Hughes, G.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krawczynski, H.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; Meagher, K.; Moriarty, P.; Mukherjee, R.; Ong, R. A.; Otte, A. N.; Park, N.; Pichel, A.; Pohl, M.; Popkow, A.; Prokoph, H.; Quinn, J.; Ragan, K.; Rajotte, J.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Theiling, M.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Wakely, S. P.; Weekes, T. C.; Weinstein, A.; Welsing, R.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; VERITAS Collaboration; Villata, M.; Raiteri, C.; Aller, H. D.; Aller, M. F.; Chen, W. P.; Jordan, B.; Koptelova, E.; Kurtanidze, O. M.; Lähteenmäki, A.; McBreen, B.; Larionov, V. M.; Lin, C. S.; Nikolashvili, M. G.; Angelakis, E.; Capalbi, M.; Carramiñana, A.; Carrasco, L.; Cassaro, P.; Cesarini, A.; Fuhrmann, L.; Giroletti, M.; Hovatta, T.; Krichbaum, T. P.; Krimm, H. A.; Max-Moerbeck, W.; Moody, J. W.; Maccaferri, G.; Mori, Y.; Nestoras, I.; Orlati, A.; Pace, C.; Pearson, R.; Perri, M.; Readhead, A. C. S.; Richards, J. L.; Sadun, A. C.; Sakamoto, T.; Tammi, J.; Tornikoski, M.; Yatsu, Y.; Zook, A.

    2015-04-01

    Aims: We perform an extensive characterization of the broadband emission of Mrk 421, as well as its temporal evolution, during the non-flaring (low) state. The high brightness and nearby location (z = 0.031) of Mrk 421 make it an excellent laboratory to study blazar emission. The goal is to learn about the physical processes responsible for the typical emission of Mrk 421, which might also be extended to other blazars that are located farther away and hence are more difficult to study. Methods: We performed a 4.5-month multi-instrument campaign on Mrk 421 between January 2009 and June 2009, which included VLBA, F-GAMMA, GASP-WEBT, Swift, RXTE, Fermi-LAT, MAGIC, and Whipple, among other instruments and collaborations. This extensive radio to very-high-energy (VHE; E> 100 GeV) γ-ray dataset provides excellent temporal and energy coverage, which allows detailed studies of the evolution of the broadband spectral energy distribution. Results: Mrk421 was found in its typical (non-flaring) activity state, with a VHE flux of about half that of the Crab Nebula, yet the light curves show significant variability at all wavelengths, the highest variability being in the X-rays. We determined the power spectral densities (PSD) at most wavelengths and found that all PSDs can be described by power-laws without a break, and with indices consistent with pink/red-noise behavior. We observed a harder-when-brighter behavior in the X-ray spectra and measured a positive correlation between VHE and X-ray fluxes with zero time lag. Such characteristics have been reported many times during flaring activity, but here they are reported for the first time in the non-flaring state. We also observed an overall anti-correlation between optical/UV and X-rays extending over the duration of the campaign. Conclusions: The harder-when-brighter behavior in the X-ray spectra and the measured positive X-ray/VHE correlation during the 2009 multi-wavelength campaign suggests that the physical processes

  11. Multiwavelength observations of Markarian 421 in 2005-2006.

    SciTech Connect

    Horan, D.; Acciari, V. A.; Bradury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Smith, A. W.; Hays, E.

    2009-01-01

    Since 2005 September, the Whipple 10 m Gamma-ray Telescope has been operated primarily as a blazar monitor. The five northern hemisphere blazars that have already been detected at the Whipple Observatory, Markarian 421 (Mrk 421), H1426+428, Mrk 501, 1ES 1959+650, and 1ES 2344+514, are monitored routinely each night that they are visible. We report on the Mrk 421 observations taken from 2005 November to 2006 June in the gamma-ray, X-ray, optical, and radio bands. During this time, Mrk 421 was found to be variable at all wavelengths probed. Both the variability and the correlations among different energy regimes are studied in detail here. A tentative correlation, with large spread, was measured between the X-ray and gamma-ray bands, while no clear correlation was evident among the other energy bands. In addition to this, the well-sampled spectral energy distribution of Mrk 421 (1101+384) is presented for three different activity levels. The observations of the other blazar targets will be reported separately.

  12. The Bright Gamma-Ray Transient GRO J1838-0145: Multiwavelength Studies of X-Ray Novae

    NASA Technical Reports Server (NTRS)

    Tavani, Marco

    1999-01-01

    We completed the observational work regarding the bright gamma-ray transient GRO J1838-014 that might be a representative of a new class of gamma-ray sources in our Galaxy. A bright gamma-ray flare was detected by EGRET in June 1996. Its time variability (approx. weeks) and the absence of a clearly identified radio-loud (-approx. 1 Jy) blazar in its error box are crucial for our interpretation of GRO J1838-014 as an object different from gamma-ray blazars or isolated pulsars. We also observed the error box with ASCA and SAX pointings without identifying obvious candidate counterparts. The X-ray flux in quiescence, if any, is quite low, and canonical X-ray binary systems are also excluded. GRO J1838-014 is not the only non-blazar gamma-ray transients detected by EGRET in the Galactic plane. An analysis of CGRO Cycle 4 data is being completed in collaboration with R. Mukherjee and J. Mattox with the discussion of other interesting unidentified sources. Pulsars embedded in transient gaseous surroundings (maybe in binary systems) or compact objects in special systems are plausible candidates. A theoretical analysis is being developed. We also continued the study of Galactic X-ray novae, in particular of systems producing radio jets such as GRS 1915+10. The use of Green Bank Interferometer data (of which the MT is the chair of the executive committee) has been of great use to GRO and other satellite missions. We completed a study of X-ray/radio outbursts of GRS 1915+10 with BSAX and Ryle radiotelescope data and CGRO/BATSE simultaneous data. We also continued our theoretical work on gamma-ray bursts.

  13. External inverse-Compton Emission from Blazar Jets

    SciTech Connect

    Carson, Jennifer E.; Chiang, James; /SLAC

    2007-09-25

    According to leptonic models for the high-energy emission from blazars, relativistic electrons in the inner jets inverse-Compton scatter photons from a variety of sources. Seed photons are certainly introduced via the synchrotron process from the electrons themselves, but external sources of seed photons may also be present. In this paper, we present detailed derivations of the equations describing external inverse-Compton scattering from two sources of seed photons: direct emission from the accretion disk, and accretion disk photons that have scattered off the broad line region. For each source, we derive the seed photon spectrum incident on the jet, the single electron energy loss rate, and the emitted photon spectrum.

  14. Studio delle popolazioni di blazar ad alte energie

    NASA Astrophysics Data System (ADS)

    Gasparrini, D.; Giommi, P.

    2008-10-01

    Utilizzando la grande quantita' di dati sui blazar disponibile ad oggi, e' possibile costruire una distribuzione spettrale di energia (SED) media per ciascuna classe di oggetti. Basandosi su un modello SSC, e' inoltre possibile stimare il comportamento di questi oggetti nella banda di energia dei raggi gamma partendo dalle informazioni ottenute da osservazioni in altre bande di energia quali il radio e l'X. Utilizzando le simulazioni sara` possibile prevedere un eventuale cambio di popolazione dominante ad alte energie(oltre 1GeV) rispetto a quanto avviene in banda radio dove domina la popolazione dei FSRQ rispetto ai BL Lac e cercare un'eventuale conferma dagli esperimenti AGILE e GLAST.

  15. Second-Order Fermi Acceleration and Emission in Blazar Jets

    NASA Astrophysics Data System (ADS)

    Asano, Katsuaki; Takahara, Fumio; Toma, Kenji; Kusunose, Masaaki; Kakuwa, Jun

    The second-order Fermi acceleration (Fermi-II) driven by turbulence may be responsible for the electron acceleration in blazar jets. We test this model with time-dependent simulations, adopt it for 1ES 1101-232, and Mrk 421. The Fermi-II model with radial evolution of the electron injection rate and/or diffusion coefficient can reproduce the spectra from the radio to the gamma-ray regime. For Mrk 421, an external radio photon field with a luminosity of 4.9 begin{math} {times} 10 (38) erg s (-1) is required to agree with the observed GeV flux. The temporal variability of the diffusion coefficient or injection rate causes flare emission. The observed synchronicity of X-ray and TeV flares implies a decrease of the magnetic field in the flaring source region.

  16. TeV blazars as seen by the CAT telescope

    NASA Astrophysics Data System (ADS)

    Piron, Frederic; CAT Collaboration

    2001-05-01

    Les blazars de type Lacertide sont des noyaux actifs de galaxies possedant un jet relativiste de matiere dirige vers la Terre. L'emis- sion de ce jet, amplifiee par effet Doppler, domine celle de l'objet central sur un large domaine en energie, avec des variations parfois tres courtes dans le repere de l'observateur. Les resultats d'observation par C.A.T. de Lacertides extremes seront presentes. L'etude de leur emission au TeV, et de sa corre- lation avec celle observee dans le domaine des rayons X, permet de sonder les mecanismes d'acceleration a l'oeuvre dans les jets, dans l'environnement proche du trou noir central.

  17. Shaping the GeV-spectra of bright blazars

    NASA Astrophysics Data System (ADS)

    Hunger, L.; Reimer, A.

    2016-05-01

    Aims: The non-thermal spectra of jetted active galactic nuclei (AGN) show a variety of shapes and degrees of curvature in their low- and high energy components. From some of the brightest Fermi-LAT blazars, prominent spectral breaks at a few GeV have been regularly detected, which is inconsistent with conventional cooling effects. We study the effects of continuous time-dependent injection of electrons into the jet with differing rates, durations, locations, and power-law spectral indices, and evaluate its impact on the ambient emitting particle spectrum that is observed at a given snapshot time in the framework of a leptonic blazar emission model. With this study, we provide a basis for analyzing ambient electron spectra in terms of injection requirements, with implications for particle acceleration modes. Methods: The emitting electron spectrum is calculated by Compton cooling the continuously injected electrons, where target photons are assumed to be provided by the accretion disk and broad line region (BLR). From this setup, we calculate the non-thermal photon spectra produced by inverse Compton scattering of these external target radiation fields using the full Compton cross-section in the head-on approximation. Results: By means of a comprehensive parameter study we present the resulting ambient electron and photon spectra, and discuss the influence of each injection parameter individually. We found that varying the injection parameters has a notable influence on the spectral shapes, which in turn can be used to set interesting constraints on the particle injection scenarios. By applying our model to the flare state spectral energy distribution (SED) of 3C 454.3, we confirm a previous suggestion that explained the observed spectral changes at a few GeV by a combination of the Compton-scattered disk and BLR radiation. We determine the required injection parameters for this scenario. We also show that this spectral turn-over can also be understood as Compton

  18. TeV blazar variability: the firehose instability?

    NASA Astrophysics Data System (ADS)

    Subramanian, Prasad; Shukla, Amit; Becker, Peter A.

    2012-06-01

    Recently observed minute-time-scale variability of blazar emission at TeV energies has imposed severe constraints on jet models and TeV emission mechanisms. We focus on a robust jet instability to explain this variability. As a consequence of the bulk outflow of the jet plasma, the pressure is likely to be anisotropic, with the parallel pressure P|| in the forward jet direction exceeding the perpendicular pressure P⊥. Under these circumstances, the jet is susceptible to the firehose instability, which can cause disruptions in the large-scale jet structure and result in variability of the observed radiation. For a realistic range of parameters, we find that the growth time-scale of the firehose instability is ≈ a few minutes, in good agreement with the observed TeV variability time-scales for Mrk 501 and PKS 2155-304.

  19. Remote Heat Flux Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (k = 6 gm). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 gm) radiation transmitted through the sapphire disk. The thermal conductivity of the sapphire disk and the heat transfer coefficients h, and h2 of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  20. Remote Heat Flux Measurement Using a Self Calibration Multiwavelength Pyrometer and a Transparent Material

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1998-01-01

    A self calibrating multiwavelength pyrometer was used to conduct remote heat flux measurements using a transparent sapphire disk by determining the sapphire disk's front and back surface temperatures. Front surface temperature (Tfs) was obtained from detection of surface emitted radiation at long wavelengths (lambda > 6 micrometers). Back surface temperature (Tbs) was obtained from short wavelength (1 to 5 micrometers) radiation transmitted through the sapphire disk. The thermal conductivity k of the sapphire disk and the heat transfer coefficients h(sub 1) and h(sub 2) of its surfaces are determined experimentally. An analysis of the heat flux measurement is presented.

  1. Anatomy of a blazar in the (sub-)millimeter: ALMA observations of PKS 0521-365

    NASA Astrophysics Data System (ADS)

    Leon, S.; Cortes, P. C.; Guerard, M.; Villard, E.; Hidayat, T.; Ocaña Flaquer, B.; Vila-Vilaro, B.

    2016-02-01

    Aims: We aim at analyzing the (sub-)millimeter emission in a nearby blazar, PKS 0521-365, to study the synchrotron and thermal emission in the different components detected at low frequency. Methods: We analyzed the archive public data of the ALMA Cycle 0 where PKS 0521-365 is used as a calibrator. A total of 13 projects with 23 dataset were analyzed in Bands 3, 6, and 7 and combined. The whole set of data was combined and wavelet-filtered to obtain a deep image toward PKS 0521-365, reaching a dynamic range of 47 000. The individual emission flux was measured on different dates over a period of 11 months in various components. Finally we analyzed the spectral energy distribution (SED) in each different component, including the radio jet and counter jet. Results: The point sources detected in the field follow a similar distribution to previous studies. The blazar flux shows large variation especially in Band 3. Different components are observed: core, radio jet, and newly detected counter jet, hot spot (HS), and a disky structure roughly perpendicular to the jet. The HS emission is formed by a point source surrounded by an extended emission. The viewing angle of the jet is about 30° with a Doppler factor of δ = 1.6. The HS is at a distance of 19 kpc from the center. The SED analysis shows a strong variation in the core spectral index, especially in Band 3. The two components in the radio jet have roughly a flat spectral index in Bands 6 and 7. Conclusions: The different weak and extended components in PKS 0521-365 are detected with the ALMA data. The analysis of both jets constrains the geometrical distance of the HS to the center. The SED presents a different shape in time and frequency for each component. Finally, a new structure is detected roughly perpendicular to the radio jet. and a thermal emission origin is currently favored. Further observations at higher spatial resolution are needed to confirm that hypothesis. FITS files for all the images are only

  2. GAMMA-RAY LIGHT CURVES AND VARIABILITY OF BRIGHT FERMI-DETECTED BLAZARS

    SciTech Connect

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Bechtol, K.; Berenji, B.; Blandford, R. D.; Bloom, E. D.; Borgland, A. W.; Bouvier, A.; Antolini, E.; Bonamente, E.; Baldini, L.; Bellazzini, R.; Bregeon, J.; Brez, A.; Ballet, J.; Bastieri, D.; Brigida, M.; Bruel, P. E-mail: stefano.ciprini@pg.infn.i E-mail: stefan@astro.su.s E-mail: stefan@astro.su.s E-mail: sarac@slac.stanford.ed

    2010-10-10

    This paper presents light curves as well as the first systematic characterization of variability of the 106 objects in the high-confidence Fermi Large Area Telescope Bright AGN Sample (LBAS). Weekly light curves of this sample, obtained during the first 11 months of the Fermi survey (2008 August 4-2009 July 4), are tested for variability and their properties are quantified through autocorrelation function and structure function analysis. For the brightest sources, 3 or 4 day binned light curves are extracted in order to determine power density spectra (PDSs) and to fit the temporal structure of major flares. More than 50% of the sources are found to be variable with high significance, where high states do not exceed 1/4 of the total observation range. Variation amplitudes are larger for flat spectrum radio quasars and low/intermediate synchrotron frequency peaked BL Lac objects. Autocorrelation timescales derived from weekly light curves vary from four to a dozen of weeks. Variable sources of the sample have weekly and 3-4 day bin light curves that can be described by 1/f {sup {alpha}} PDS, and show two kinds of gamma-ray variability: (1) rather constant baseline with sporadic flaring activity characterized by flatter PDS slopes resembling flickering and red noise with occasional intermittence and (2)-measured for a few blazars showing strong activity-complex and structured temporal profiles characterized by long-term memory and steeper PDS slopes, reflecting a random walk underlying mechanism. The average slope of the PDS of the brightest 22 FSRQs and of the 6 brightest BL Lacs is 1.5 and 1.7, respectively. The study of temporal profiles of well-resolved flares observed in the 10 brightest LBAS sources shows that they generally have symmetric profiles and that their total duration vary between 10 and 100 days. Results presented here can assist in source class recognition for unidentified sources and can serve as reference for more detailed analysis of the

  3. Probing the Relativistic Jets of Active Galactic Nuclei with Multiwavelength Monitoring

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Jorstad, Svetlana G.; Aller, Margo

    2005-01-01

    The work completed includes the analysis of observations obtained during Cycle 7 (March 2002-February 2003) of the Rossi X-ray Timing Explorer (RXTE). The project was part of a longer-term, continuing program to study the X-ray emission process in blazars and radio galaxies in collaboration with Dr. Ian McHardy (U. of Southampton, UK) and Prof. Thomas Balonek (Colgate U.). The goals of the program are to study the X-ray emission mechanism in blazars and radio galaxies and the relation of the X-ray emission to changes in the relativistic jet. The program includes contemporaneous brightness and linear polarization monitoring at radio and optical wavelengths, total and polarized intensity imaging at at 43 GHz with a resolution of 0.1 milliarcseconds with the VLBA, and well-sampled X-ray light curves obtained from a series of approved RXTE programs. The objects studied in the time period covered by the grant were 3C 120, 3C 279, PKS 1510-089, and 3C 273, all with radio jets containing bright knots that appear to move at superluminal speeds. During RXTE Cycle 7, the project was awarded RXTE time to monitor PKS 1510-089 two times per week, 3C 273 and 3C 279 three times per week, and 3C 120 four times per week. In addition, 3C273 and 3C 279 were observed several times per day during a ten-day period in April 2002. The X-ray data, including those from earlier cycles, were compared with radio measurements obtained in the centimeter-wave band by the monitoring program of Drs. Margo and Hugh Aller at the University of Michigan Radio Astronomy Observatory, monthly imaging observations with the VLBA at 43 GHz, and optical observations obtained at several telescopes around the world.

  4. Multiwavelength monolithic integrated fiber optics terminal - An update

    NASA Technical Reports Server (NTRS)

    Spear-Zino, J. D.; Rice, R. R.; Powers, J. K.; Bryan, D. A.; Hall, D. G.; Dalke, E. A.; Reed, W. R.

    1981-01-01

    This paper serves as an update for the Multiwavelength Monolithic Integrated Fiber Optic Terminal (MMIFOT) being developed by MDAC-St. Louis for NASA's Johnson Space Center. The program objective is to utilize guided wave optical technology to develop a passive optical wavelength multiplexing subsystem with a single mode optical fiber serving as the transmission medium.

  5. Multiwavelength studies of Galactic TeV particle accelerators

    NASA Astrophysics Data System (ADS)

    Kaaret, Philip

    2016-07-01

    Our Milky Way galaxy is host to a variety of astrophysical objects capable of accelerating particles to TeV energies, including supernova remnants and pulsar wind nebulae. I will review recent multiwavelength results on Galactic TeV sources and discuss the implications for particle acceleration and diffusion in these systems.

  6. X-ray spectral studies of TeV γ-ray emitting blazars

    NASA Astrophysics Data System (ADS)

    Wierzcholska, Alicja; Wagner, Stefan J.

    2016-05-01

    This work is a summary of the X-ray spectral studies of 29 TeV (1012 eV, tera-electron-volt) γ-ray emitting blazars observed with Swift/XRT, especially focusing on sources for which the X-ray regime allows us to study the low- and the high-energy ends of the particle distribution function. Variability studies require simultaneous coverage, ideally sampling different flux states of each source. This is achieved using X-ray observations by disentangling the high-energy end of the synchrotron emission and the low-energy end of the Compton emission, which are produced by the same electron population. We focused on a sample of 29 TeV γ-ray emitting blazars with the best signal-to-noise X-ray observations collected with Swift/XRT in the energy range 0.3-10 keV during 10 yr of Swift/XRT operations. We investigate the X-ray spectral shapes and the effects of different corrections for neutral hydrogen absorption and decompose the synchrotron and inverse Compton components. For five sources (3C 66A, S5 0716+714, W Comae, 4C +21.35 and BL Lacertae) a superposition of both components is observed in the X-ray band, permitting simultaneous, time-resolved studies of both ends of the electron distribution. The analysis of multi-epoch observations revealed that the break energy of the X-ray spectrum varies only by a small factor with flux changes. Flux variability is more pronounced in the synchrotron domain (high-energy end of the electron distribution) than in the Compton domain (low-energy end of the electron distribution). The spectral shape of the Compton domain is stable, while the flux of the synchrotron domain is variable. These changes cannot be described by simple variations of the cut-off energy, suggesting that the high-energy end of the electron distribution is not generally well described by cooling only.

  7. Multiwavelength optical properties of compact dust aggregates in protoplanetary disks

    NASA Astrophysics Data System (ADS)

    Min, M.; Rab, Ch.; Woitke, P.; Dominik, C.; Ménard, F.

    2016-01-01

    Context. In protoplanetary disks micron-size dust grains coagulate to form larger structures with complex shapes and compositions. The coagulation process changes the absorption and scattering properties of particles in the disk in significant ways. To properly interpret observations of protoplanetary disks and to place these observations in the context of the first steps of planet formation, it is crucial to understand the optical properties of these complex structures. Aims: We derive the optical properties of dust aggregates using detailed computations of aggregate structures and compare these computationally demanding results with approximate methods that are cheaper to compute in practice. In this way we wish to understand the merits and problems of approximate methods and define the context in which they can or cannot be used to analyze observations of objects where significant grain growth is taking place. Methods: For the detailed computations we used the discrete dipole approximation (DDA), a method able to compute the interaction of light with a complexly shaped, inhomogeneous particle. We compared the results to those obtained using spherical and irregular, homogeneous and inhomogeneous particles. Results: While no approximate method properly reproduces all characteristics of large dust aggregates, the thermal properties of dust can be analyzed using irregularly shaped, porous, inhomogeneous grains. The asymmetry of the scattering phase function is a good indicator of aggregate size, while the degree of polarization is probably determined by the size of the constituent particles. Optical properties derived from aggregates significantly differ from the most frequently used standard ("astronomical silicate" in spherical grains). We outline a computationally fast and relatively accurate method that can be used for a multiwavelength analysis of aggregate dust in protoplanetary disks.

  8. A Multiwavelength Study of the Orion-Eridanus Superbubble.

    NASA Astrophysics Data System (ADS)

    Guo, Zhiyu

    1995-01-01

    A multiwavelength study of the Orion-Eridanus superbubble has been carried out based on the ROSAT PSPC pointed observation data, IRAS 100 μm data, the 21 cm data obtained with NRAO 140-foot telescope at Green Bank and the inter-stellar Na D data obtained with NOAO Coude Feed telescope. The temperature and the N_{rm H} distribution across the superbubble have been obtained from the X-ray data analysis. It is found that the temperature and N _{rm H} distribution obtained from the best fit are consistent with the morphology difference between the 1over 4 keV and the 3over 4 keV X-ray emission results from the absorption by the intervening gas. Distance limits to the boundary of the Local Bubble and to the near and far sides of the shell associated with the Orion-Eridanus bubble have been estimated based on our 21 cm mapping of the X-ray absorbing clouds and our interstellar Na D absorption line observations toward stars in the 21 cm fields. It is found that the distance to the near side of the Orion -Eridanus bubble is 155 +/- 22 pc in the direction (1,b) ~ (203 ^circ, -40^circ ) and the upper distance limit to the far side of the bubble is 586 pc in the same direction. The observed geometry and kinematics of the Orion-Eridanus feature have been compared with the standard wind-blown bubble theory. It is found that the Orion-Eridanus feature can be explained as a stellar wind superbubble associated with the Orion OB1 association. The evolution and dynamics of the Orion -Eridanus superbubble have also been discussed and it is found that the interstellar pressures from cosmic rays and interstellar magnetic fields play important roles in determining whether the Orion-Eridanus superbubble will blow out the entire galactic H scI disk.

  9. Reconstructing the Gamma-Ray Photon Optical Depth of the Universe To Z Approx. 4 from Multiwavelength Galaxy Survey Data

    NASA Technical Reports Server (NTRS)

    Helgason, Kari; Kashlinsky, Alexander

    2012-01-01

    Reconstructing the Gamma-Ray Photon Optical Depth of the Universe To Z Approx. 4fFrom Multiwavelength Galaxy Survey Data We reconstruct the gamma-ray opacity of the universe out to z approx. < 3–4 using an extensive library of 342 observed galaxy luminosity function (LF) surveys extending to high redshifts .We cover the whole range from UV to mid-IR (0.15–25 micron ) providing for the first time a robust empirical calculation of the gamma gamma optical depth out to several TeV. Here, we use the same database as Helgason et al. where the extragalactic background light was reconstructed from LFs out to 4.5 micron and was shown to recover observed galaxy counts to high accuracy. We extend our earlier library Of LFs to 25micron such that it covers the energy range of pair production with gamma -rays (1) in the entire Fermi/LAT energy range, and (2) at higher TeV energies probed by ground-based Cherenkov telescopes. In the absence of significant contributions to the cosmic diffuse background from unknown populations, such as the putative Population III era sources, the universe appears to be largely transparent to gamma-rays at all Fermi/LAT energies out to z approx.. 2 whereas it becomes opaque to TeV photons already at z approx. < 0.2 and reaching tau approx 10 at z = 1. Comparing with the currently available Fermi/LAT gamma-ray burst and blazar data shows that there is room for significant emissions originating in the first stars era.

  10. The 1993 multiwavelength campaign on 3C 279: The radio to gamma-ray energy distribution inlow state

    NASA Technical Reports Server (NTRS)

    Maraschi, L.; Grandi, P.; Urry, C. M.; Wehrle, A. E.; Madejski, G. M.; Fink, H. H.; Ghisellini, G.; Hartman, R. C.; Koratkar, A. P.; Von Montigny, C.

    1994-01-01

    Simultaneous observations of 3C 279 at radio, millimeter, near-infrared, optical, ultraviolet (with IUE) and X-ray (with ROSAT) wavelengths were obtained in 1992 December-1993 January, during a three week pointing at the source by the Compton Gamma Ray Observatory. The blazar was in a quiescent or 'low' state during this period. Comparing the multiwavelength energy distribution to that from 1991 June, when 3C 279 was in its brightest recorded gamma-ray state, we find the following: (1) 3C 279 faded dramatically at all frequencies above 10(exp 14) Hz, while the flux variations at low frequencies (radio to millimeter wavelengths) were minor. (2) The near-infrared-optical-ultraviolet spectral shape was softer (steeper) in the quiescent state, and the X-ray spectra also appear softer, although the spectral indix measured by ROSAT refer to a lower energy band than that measured earlier with Ginga. (3) The ratio of the gamma-ray luminosity to that across all other frequencies decreased from a value of approximately equal to 10 in the flaring state to a value approximately equal to 1 in the quiescent state. These findings imply that the production of gamma-rays is closely related to the optical-ultraviolet continuum, in agreement with models where gamma-rays are produced through inverse Compton (IC) scattering by relativistic electrons emitting the synchrotron continuum. The observed nonlinear relation between the synchrotron and IC requires both a change in the electron spectrum and an associated change in the seed photons.

  11. Black hole-jet systems: From blazars to microquasars

    NASA Astrophysics Data System (ADS)

    Xue, Yongquan

    Understanding black holes is one of the most intriguing and important topics in high energy astrophysics. Many astronomical black hole systems are known to contain three basic components: a black hole, an accretion disk, and a pair of collimated jets that are likely coupled physically to the accretion disk. For this thesis work, the focus is on two classes of black hole-jet systems, known as blazars and microquasars. There is growing evidence that the central engines in both types of systems are qualitatively similar. Collectively, they may, therefore, provide an excellent laboratory for studying common physical processes over a vast range of physical scales. Although both types of systems have been studied extensively, there are still many outstanding issues. The goal of this thesis work is to cast light on some of these important issues. First, to understand the energetics of the flaring phenomenon in blazars, it is necessary to get a handle on the size of the emitting region. An effective way to do so is to quantify timescales over which a source varies. I systematically studied X-ray flaring activities of the TeV blazar Mrk 501 and found flares over a wide range of timescale, with the most rapid one lasting for only about 800 s, which is the shortest ever seen in this system. The latter sets an upper limit of ~ 2.4 × 10^14 cm (i.e., 800 light seconds) on the size of the region that produces the flare, which is already comparable to the characteristic size of the black hole (of ~ 10 9 [Special characters omitted.] ). Second, a related question is what causes the observed flares in blazars. To this end, I studied X-ray spectral evolution of TeV blazars Mrk 421 and Mrk 501 during individual flares that last for a few days. Such a study has become possible only recently, with high-quality X-ray data taken during very active periods of the sources. I fitted the time-resolved X-ray spectra with a synchrotron model and found that, in order to account for the observed

  12. High-energy sources at low radio frequency: the Murchison Widefield Array view of Fermi blazars

    NASA Astrophysics Data System (ADS)

    Giroletti, M.; Massaro, F.; D'Abrusco, R.; Lico, R.; Burlon, D.; Hurley-Walker, N.; Johnston-Hollitt, M.; Morgan, J.; Pavlidou, V.; Bell, M.; Bernardi, G.; Bhat, R.; Bowman, J. D.; Briggs, F.; Cappallo, R. J.; Corey, B. E.; Deshpande, A. A.; Ewall-Rice, A.; Emrich, D.; Gaensler, B. M.; Goeke, R.; Greenhill, L. J.; Hazelton, B. J.; Hindson, L.; Kaplan, D. L.; Kasper, J. C.; Kratzenberg, E.; Feng, L.; Jacobs, D.; Kudryavtseva, N.; Lenc, E.; Lonsdale, C. J.; Lynch, M. J.; McKinley, B.; McWhirter, S. R.; Mitchell, D. A.; Morales, M. F.; Morgan, E.; Oberoi, D.; Offringa, A. R.; Ord, S. M.; Pindor, B.; Prabu, T.; Procopio, P.; Riding, J.; Rogers, A. E. E.; Roshi, A.; Udaya Shankar, N.; Srivani, K. S.; Subrahmanyan, R.; Tingay, S. J.; Waterson, M.; Wayth, R. B.; Webster, R. L.; Whitney, A. R.; Williams, A.; Williams, C. L.

    2016-04-01

    Context. Low-frequency radio arrays are opening a new window for the study of the sky, both to study new phenomena and to better characterize known source classes. Being flat-spectrum sources, blazars are so far poorly studied at low radio frequencies. Aims: We characterize the spectral properties of the blazar population at low radio frequency, compare the radio and high-energy properties of the gamma-ray blazar population, and search for radio counterparts of unidentified gamma-ray sources. Methods: We cross-correlated the 6100 deg2 Murchison Widefield Array Commissioning Survey catalogue with the Roma blazar catalogue, the third catalogue of active galactic nuclei detected by Fermi-LAT, and the unidentified members of the entire third catalogue of gamma-ray sources detected by Fermi-LAT. When available, we also added high-frequency radio data from the Australia Telescope 20 GHz catalogue. Results: We find low-frequency counterparts for 186 out of 517 (36%) blazars, 79 out of 174 (45%) gamma-ray blazars, and 8 out of 73 (11%) gamma-ray blazar candidates. The mean low-frequency (120-180 MHz) blazar spectral index is ⟨αlow⟩ = 0.57 ± 0.02: blazar spectra are flatter than the rest of the population of low-frequency sources, but are steeper than at ~GHz frequencies. Low-frequency radio flux density and gamma-ray energy flux display a mildly significant and broadly scattered correlation. Ten unidentified gamma-ray sources have a (probably fortuitous) positional match with low radio frequency sources. Conclusions: Low-frequency radio astronomy provides important information about sources with a flat radio spectrum and high energy. However, the relatively low sensitivity of the present surveys still misses a significant fraction of these objects. Upcoming deeper surveys, such as the GaLactic and Extragalactic All-Sky MWA (GLEAM) survey, will provide further insight into this population. Tables 5-7 are only available at the CDS via anonymous ftp to http

  13. Optical Variability of the Blazar 3C 454.3: Long-term Behavior and the Dramatic 2005 Outburst

    NASA Astrophysics Data System (ADS)

    Balonek, T. J.; Gadway, B.; Mullan, B.; Wortel, S.; Pierkowski, D.; Forsyth, C.

    2006-06-01

    In May of 2005, observations at R, V, and I with the Foggy Bottom Observatory 16-inch Cassegrain reflecting telescope at Colgate University revealed an unprecedented outburst in the blazar type quasar 3C 454.3. At its peak, R 11.9, the blazar was four times brighter than during any previously observed period in our seventeen-year blazar monitoring program. This object had undergone only relatively mild flaring amid low-level optical meandering in the past. The blazar 3C 454.3 exhibits a variety of variability timescales (from hours to years) in which there is a discernible correlation between the brightness and optical color indices. A two-component model (with distinct variable and non-variable components) to the blazar optical variations can account for the general trends seen in the color (spectral index) and brightness variations.

  14. Diode-end-pumped solid-state lasers with dual gain media for multi-wavelength emission

    NASA Astrophysics Data System (ADS)

    Cho, C. Y.; Chang, C. C.; Chen, Y. F.

    2015-01-01

    We develop a theoretical model for designing a compact efficient multi-wavelength laser with dual gain media in a shared resonator. The developed model can be used to analyze the optimal output reflectivity for each wavelength to achieve maximum output power for multi-wavelength emission. We further demonstrate a dual-wavelength laser at 946 nm and 1064 nm with Nd:YAG and Nd:YVO4 crystals to confirm the numerical analysis. Under optimum conditions and at incident pump power of 17 W, output power at 946 nm and 1064 nm was up to 2.51 W and 2.81 W, respectively.

  15. Multiwavelength monitoring of the BL Lacertae object PKS 2155-304. 4: Multiwavelength analysis

    NASA Technical Reports Server (NTRS)

    Edelson, R.; Krolik, J.; Madejski, G.; Maraschi, L.; Pike, G.; Urry, C. M.; Brinkmann, W.; Courvoisier, T. J.-L.; Ellithorpe, J.; Horne, K.

    1995-01-01

    Simultaneous X-ray, ultraviolet, optical, infrared, and radio monitoring data were used to test and constrain models of continuum emission from the BL Lacertae object PKS 2155-304. Intensively sampled ultraviolet and soft X-ray light curves showed a clear temporal correlation with the X-rays leading the ultraviolet by 2-3 hr. This lag was found to be significantly different from zero after an exhaustive comparison of four different techniques for measuring temporal correlations. Variations in the ultraviolet trough optical wave bands were also strongly correlated, with no measurable lag down to limiting timescales of approximately less than 1-2 hr. This strong correlation extends to the near-infrared, but the less intensive sampling precludes measurement of any lag beyomnd an upper limit of approximately less than 1 day. These lags and limits of the order of hours are much shorter than most rapid observed single-band variations. Because of the very sparse radio sampling, it was not possible to measure quantitatively the correlation and lag with shorter wavelengths, but the data do suggest that the radio may lag the optical/ultraviolet by approximately 1 week, with longer delays and weaker variations to longer radio wavelengths. The epoch-folding Q(exp 2) statistic was used to test for periodicity, and no evidence for strict or quasi-periodicity was found in any of the light curves. Because they lead the lower frequencies, the soft X-rays (approximately less than 1 keV) cannot arise from synchrotron self-Compton scattering. These results also rule out the accretion disk model, which predicts a measurable lag between ultraviolet/optical wavelength bands and a correlation between hardness and brightness, neither of which were seen. They are consistent with the entire radio through X-ray continuum arising from direct synchrotron emission from a relativistic jet. However, the tapered jet model, in which the X-ray emission is produced closer in, has problems explaining the magnitude of the ultraviolet/X-ray lag, because the X-ray-emitting electrons have very short lifetimes (t(sub 1/2) much less than 1 s). The result that the lag is much smaller than the variability timescale suggests instead that the radiation may be produced in a flattened region such as a shock front.

  16. Methods for the Quasi-Periodic Variability Analysis in Blazars

    NASA Astrophysics Data System (ADS)

    Liu, Y.; Fan, J. H.; Wang, H. G.; Deng, G. G.

    2011-06-01

    In this work, four methods are introduced to analyse the unevenly sampled data. The four methods are power spectral density, auto-correlation function, structure function and Jurkevich method. Some interesting mathematical links are derived amongst the four methods. These links show that the four methods have the same performance. For the Jurkevich method, the effect of the width of bins is apparent. If the width is half the time scale, the method has better performance.

  17. The connection between radio and γ-ray emission in Fermi/LAT blazars

    NASA Astrophysics Data System (ADS)

    Fan, Xu-Liang; Bai, Jin-Ming; Liu, Hong-Tao; Chen, Liang; Liao, Neng-Hui

    2012-11-01

    We collect the second Large Area Telescope AGN catalog (2LAC) and Monitor of Jets in AGN with VLBA Equipment (MOJAVE) quasi-simultaneous data to investigate the radio-γ connection of blazars. The cross sample contains 166 sources. The statistical analysis based on this sample confirms positive correlations between these two bands, but the correlations become weaker as the γ-ray energy increases. The statistical results between various parameters show negative correlations of γ-ray photon spectral index with γ-ray loudness for both Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects, positive correlations of γ-ray variability index with the γ-ray loudness for FSRQs, a negative correlation of the γ-ray variability index with the γ-ray photon spectral index for FSRQs, and negative correlations of γ-ray photon spectral index with γ-ray luminosity for FSRQs. These results suggest that the γ-ray variability may be due to changes inside the γ-ray emission region like the injected power, rather than changes in the photon density of the external radiation fields, and the variability amplitude tends to be larger as the γ-rays are closer to the high energy peak of the spectral energy distribution (SED). No correlation of variability index found for BL Lacertae objects implies that variability behavior may differ below and above the peak energy.

  18. Study of the Flux and Spectral Variations in the VHE Emission from the Blazar Markarian 501, with the MAGIC Telescope

    SciTech Connect

    Paneque, D.

    2007-06-13

    The blazar Markarian 501 (Mrk 501) was observed above 100 GeV with the MAGIC Telescope during May, June and July 2005. The high sensitivity of the instrument made possible the detection of the source with high significance in each of the observing nights. During this observational campaign, the emitted gamma-ray flux from Mkn 501 was found to vary by one order of magnitude, and showed a high correlation with spectral changes. Intra-night flux variability was also observed, with flux-doubling times of {approx} 2 minutes. The data showed a clear evidence of a spectral peak (in the nuFnu representation) during the nights when the gamma-ray activity was highest. The location of this spectral feature was found to be correlated with the emitted gamma-ray flux. In these proceedings we discuss some of the results of this unprecedented spectral and temporal analysis of Mrk 501 observations in the very high energy range.

  19. Gamma-ray luminosity and photon index evolution of FSRQ blazars and contribution to the gamma-ray background

    SciTech Connect

    Singal, J.; Ko, A.; Petrosian, V.

    2014-05-10

    We present the redshift evolutions and distributions of the gamma-ray luminosity and photon spectral index of flat spectrum radio quasar (FSRQ) type blazars, using non-parametric methods to obtain the evolutions and distributions directly from the data. The sample we use for analysis consists of almost all FSRQs observed with a greater than approximately 7σ detection threshold in the first-year catalog of the Fermi Gamma-ray Space Telescope's Large Area Telescope, with redshifts as determined from optical spectroscopy by Shaw et al. We find that FSQRs undergo rapid gamma-ray luminosity evolution, but negligible photon index evolution, with redshift. With these evolutions accounted for we determine the density evolution and luminosity function of FSRQs and calculate their total contribution to the extragalactic gamma-ray background radiation, resolved and unresolved, which is found to be 16(+10/–4)%, in agreement with previous studies.

  20. Time Dependent Multi Zone Modeling of X-ray and Gamma-ray Variability of the TeV Blazar Mrk 421.

    NASA Astrophysics Data System (ADS)

    Fossati, Giovanni; Chen, X.

    2010-02-01

    We present a new time-dependent multi-zone code and its first application to study the SSC emission of Blazar Mrk 421. The code couples Fokker-Planck and Monte Carlo methods. All the light travel time effects are fully considered, internal and external. It has long been realized that simple one-zone homogeneous models are not adequate to describe several aspects of the phenomenology, in particular those pertaining to the complex multiwavelength variability. Progress has been made by several groups but important trade-offs have always been necessary, such as neglecting internal light travel time or the inclusion of IC losses in the electron evolution. Our code fully accounts for all the relevant effects, and it also affords us significant freedom w.r.t. geometry and "variability". This latter is implemented as a shock traveling along the jet, with electrons being injected as it sweeps the blob. Results are compared with the 2001 observations of Mrk 421. We also analyzed cases including a pre-existing cospatial electron population contributing to the SED, and external radiation field. It seems to be possible to achieve adequate fits to the observations, but a there remain several open issues, such as a systematic soft X-ray intraband lag, and a delay of the gamma-ray flare with respect to the X-ray flare. The two principal challenges are: 1. The simulated VHE spectrum is always softer than the observed one. 2. The correlation between the TeV gamma-ray and X-ray does not reproduce the (super)quadratic relationship observed in multiple occasions. In fact we have not been able to reproduce anything close to it in this first suite of models. We will report also on the extension of the code, and case studies, to jet-in-jet and spine-layer configurations, as well as to the study of red blazars. We acknowledge support from Chandra Award AR9-0016X

  1. BLAZAR HALOS AS PROBE FOR EXTRAGALACTIC MAGNETIC FIELDS AND MAXIMAL ACCELERATION ENERGY

    SciTech Connect

    Dolag, K.; Kachelriess, M.; Ostapchenko, S.; Tomas, R.

    2009-09-20

    High-energy photons from blazars interact within tens of kpc with the extragalactic photon background, initiating electromagnetic pair cascades. The charged component of such cascades is deflected by extragalactic magnetic fields (EGMFs), leading to halos even around initially point-like sources. We calculate the intensity profile of the resulting secondary high-energy photons for different assumptions on the initial source spectrum and the strength of the EGMF, employing also fields found earlier in a constrained simulation of structure formation including magnetohydrodynamics processes. We find that the observation of halos around blazars like Mrk 180 probes an interesting range of EGMF strengths and acceleration models: in particular, blazar halos test if the photon energy spectrum at the source extends beyond {approx}100 TeV and how anisotropic this high-energy component is emitted.

  2. Blazar Gamma-Rays, Shock Acceleration, and the Extragalactic Background Light

    NASA Technical Reports Server (NTRS)

    Stecker, Floyd W.; Baring, Matthew G.; Summerlin, Errol J.

    2007-01-01

    The observed spectra of blazars, their intrinsic emission, and the underlying populations of radiating particles are intimately related. The use of these sources as probes of the extragalactic infrared background, a prospect propelled by recent advances in TeV-band telescopes, soon to be augmented by observations by NASA's upcoming Gamma-Ray Large Area Space Telescope (GLAST), has been a topic of great recent interest. Here, it is demonstrated that if particles in blazar jets are accelerated at relativistic shocks, then GAMMA-ray spectra with indices less than 1.5 can be produced. This, in turn, loosens the upper limits on the near infrared extragalactic background radiation previously proposed. We also show evidence hinting that TeV blazars with flatter spectra have higher intrinsic TeV GAMMA-ray luminosities and we indicate that there may be a correlation of flatness and luminosity with redshift.

  3. SIMILAR RADIATION MECHANISM IN GAMMA-RAY BURSTS AND BLAZARS: EVIDENCE FROM TWO LUMINOSITY CORRELATIONS

    SciTech Connect

    Wang, F. Y.; Yi, S. X.; Dai, Z. G.

    2014-05-01

    Active galactic nuclei and gamma-ray bursts (GRBs) are powerful astrophysical events with relativistic jets. In this Letter, the broadband spectral properties of GRBs and well-observed blazars are compared. The distribution of GRBs is consistent with the well-known blazar sequence including the νL {sub ν}(5 GHz) – α{sub RX} and νL {sub ν}(5 GHz) – ν{sub peak} correlations, where α{sub RX} is defined as the broadband spectral slope in radio-to-X-ray bands, and ν{sub peak} is defined as the spectral peak frequency. Moreover, GRBs occupy the low radio luminosity end of these sequences. These two correlations suggest that GRBs could have a radiation process, i.e., synchrotron radiation, similar to blazars both in the prompt emission and afterglow phases.

  4. A Multiwavelength Study of the Intracluster Medium and the Characterization of the Multiwavelength Sub/millimeter Inductance Camera

    NASA Astrophysics Data System (ADS)

    Siegel, Seth Robert

    The first part of this thesis combines Bolocam observations of the thermal Sunyaev-Zel'dovich (SZ) effect at 140 GHz with X-ray observations from Chandra, strong lensing data from the Hubble Space Telescope (HST), and weak lensing data from HST and Subaru to constrain parametric models for the distribution of dark and baryonic matter in a sample of six massive, dynamically relaxed galaxy clusters. For five of the six clusters, the full multiwavelength dataset is well described by a relatively simple model that assumes spherical symmetry, hydrostatic equilibrium, and entirely thermal pressure support. The multiwavelength analysis yields considerably better constraints on the total mass and concentration compared to analysis of any one dataset individually. The subsample of five galaxy clusters is used to place an upper limit on the fraction of pressure support in the intracluster medium (ICM) due to nonthermal processes, such as turbulent and bulk flow of the gas. We constrain the nonthermal pressure fraction at r500c to be less than 0.11 at 95% confidence, where r500c refers to radius at which the average enclosed density is 500 times the critical density of the Universe. This is in tension with state-of-the-art hydrodynamical simulations, which predict a nonthermal pressure fraction of approximately 0.25 at r500c for the clusters in this sample. The second part of this thesis focuses on the characterization of the Multiwavelength Sub/millimeter Inductance Camera (MUSIC), a photometric imaging camera that was commissioned at the Caltech Submillimeter Observatory (CSO) in 2012. MUSIC is designed to have a 14 arcminute, diffraction-limited field of view populated with 576 spatial pixels that are simultaneously sensitive to four bands at 150, 220, 290, and 350 GHz. It is well-suited for studies of dusty star forming galaxies, galaxy clusters via the SZ Effect, and galactic star formation. MUSIC employs a number of novel detector technologies: broadband phased

  5. A Multiwavelength Study of the Intracluster Medium and the Characterization of the Multiwavelength Sub/millimeter Inductance Camera

    NASA Astrophysics Data System (ADS)

    Siegel, Seth Robert

    The first part of this thesis combines Bolocam observations of the thermal Sunyaev-Zel'dovich (SZ) effect at 140 GHz with X-ray observations from Chandra, strong lensing data from the Hubble Space Telescope (HST), and weak lensing data from HST and Subaru to constrain parametric models for the distribution of dark and baryonic matter in a sample of six massive, dynamically relaxed galaxy clusters. For five of the six clusters, the full multiwavelength dataset is well described by a relatively simple model that assumes spherical symmetry, hydrostatic equilibrium, and entirely thermal pressure support. The multiwavelength analysis yields considerably better constraints on the total mass and concentration compared to analysis of any one dataset individually. The subsample of five galaxy clusters is used to place an upper limit on the fraction of pressure support in the intracluster medium (ICM) due to nonthermal processes, such as turbulent and bulk flow of the gas. We constrain the nonthermal pressure fraction at r500c to be less than 0.11 at 95% confidence, where r500c refers to radius at which the average enclosed density is 500 times the critical density of the Universe. This is in tension with state-of-the-art hydrodynamical simulations, which predict a nonthermal pressure fraction of approximately 0.25 at r500c for the clusters in this sample. The second part of this thesis focuses on the characterization of the Multiwavelength Sub/millimeter Inductance Camera (MUSIC), a photometric imaging camera that was commissioned at the Caltech Submillimeter Observatory (CSO) in 2012. MUSIC is designed to have a 14 arcminute, diffraction-limited field of view populated with 576 spatial pixels that are simultaneously sensitive to four bands at 150, 220, 290, and 350 GHz. It is well-suited for studies of dusty star forming galaxies, galaxy clusters via the SZ Effect, and galactic star formation. MUSIC employs a number of novel detector technologies: broadband phased

  6. Stochastic modeling of the Fermi/LAT γ-ray blazar variability

    SciTech Connect

    Sobolewska, M. A.; Siemiginowska, A.; Kelly, B. C.; Nalewajko, K.

    2014-05-10

    We study the γ-ray variability of 13 blazars observed with the Fermi/Large Area Telescope (LAT). These blazars have the most complete light curves collected during the first four years of the Fermi sky survey. We model them with the Ornstein-Uhlenbeck (OU) process or a mixture of the OU processes. The OU process has power spectral density (PSD) proportional to 1/f {sup α} with α changing at a characteristic timescale, τ{sub 0}, from 0 (τ >> τ{sub 0}) to 2 (τ << τ{sub 0}). The PSD of the mixed OU process has two characteristic timescales and an additional intermediate region with 0 < α < 2. We show that the OU model provides a good description of the Fermi/LAT light curves of three blazars in our sample. For the first time, we constrain a characteristic γ-ray timescale of variability in two BL Lac sources, 3C 66A and PKS 2155-304 (τ{sub 0} ≅ 25 days and τ{sub 0} ≅ 43 days, respectively, in the observer's frame), which are longer than the soft X-ray timescales detected in blazars and Seyfert galaxies. We find that the mixed OU process approximates the light curves of the remaining 10 blazars better than the OU process. We derive limits on their long and short characteristic timescales, and infer that their Fermi/LAT PSD resemble power-law functions. We constrain the PSD slopes for all but one source in the sample. We find hints for sub-hour Fermi/LAT variability in four flat spectrum radio quasars. We discuss the implications of our results for theoretical models of blazar variability.

  7. SEARCHING FOR {gamma}-RAY BLAZAR CANDIDATES AMONG THE UNIDENTIFIED INTEGRAL SOURCES

    SciTech Connect

    Massaro, F.; Paggi, A.; D'Abrusco, R.; Tosti, G.

    2012-05-10

    The identification of low-energy counterparts for {gamma}-ray sources is one of the biggest challenges in modern {gamma}-ray astronomy. Recently, we developed and successfully applied a new association method to recognize {gamma}-ray blazar candidates that could be possible counterparts for the unidentified {gamma}-ray sources above 100 MeV in the second Fermi Large Area Telescope Catalog. This method is based on the infrared colors of the recent Wide-Field Infrared Survey Explorer (WISE) all-sky survey. In this Letter, we applied our new association method to the case of unidentified INTEGRAL sources (UISs) listed in the fourth soft gamma-ray source catalog. Only 86 UISs out of the 113 can be analyzed due to the sky coverage of the WISE Preliminary Data Release. Among these 86 UISs, we found that 18 appear to have a {gamma}-ray blazar candidate within their positional error region. Finally, we analyzed Swift archival data available for 10 out of these 18 {gamma}-ray blazar candidates, and we found that 7 out of 10 are clearly detected in soft X-rays and/or in the optical-ultraviolet band. We cannot confirm the associations between the UISs and the selected {gamma}-ray blazar candidates due to the discrepancies between the INTEGRAL and the soft X-ray spectra. However, the discovery of the soft X-ray counterparts for the selected {gamma}-ray blazar candidates adds an important clue to help us understand their origin and to confirm their blazar nature.

  8. Searching for Gamma-Ray Blazar Candidates Among the Unidentified INTEGRAL Sources

    SciTech Connect

    Massaro, F.; Paggi, A.; D'Abrusco, R.; Tosti, G.; /Perugia U.

    2012-04-02

    The identification of low-energy counterparts for {gamma}-ray sources is one of the biggest challenge in modern {gamma}-ray astronomy. Recently, we developed and successfully applied a new association method to recognize {gamma}-ray blazar candidates that could be possible counterparts for the unidentified {gamma}-ray sources above 100 MeV in the second Fermi Large Area Telescope (LAT) catalog (2FGL). This method is based on the Infrared (IR) colors of the recent Wide-Field Infrared Survey Explorer (WISE) all-sky survey. In this letter we applied our new association method to the case of unidentified INTEGRAL sources (UISs) listed in the fourth soft gamma-ray source catalog (4IC). Only 86 UISs out of the 113 can be analyzed, due to the sky coverage of the WISE Preliminary data release. Among these 86 UISs, we found that 18 appear to have a {gamma}-ray blazar candidate within their positional error region. Finally, we analyzed the Swift archival data available for 10 out these 18 {gamma}-ray blazar candidates, and we found that 7 out of 10 are clearly detected in soft X-rays and/or in the optical-ultraviolet band. We cannot confirm the associations between the UISs and the selected {gamma}-ray blazar candidates due to the discrepancies between the INTEGRAL and the soft X-ray spectra. However, the discovery of the soft X-ray counterparts for the selected {gamma}-ray blazar candidates adds an important clue to help understand their origin and to confirm their blazar nature.

  9. Temporal Correlations between Optical and Gamma-Ray Activity in Blazars

    NASA Astrophysics Data System (ADS)

    Cohen, Daniel P.; Romani, Roger W.; Filippenko, Alexei V.; Cenko, S. Bradley; Lott, Benoit; Zheng, WeiKang; Li, Weidong

    2014-12-01

    We have been using the 0.76 m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory to optically monitor a sample of 157 blazars that are bright in gamma-rays being detected with high significance (>=10σ) in one year by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. We attempt to observe each source on a three-day cadence with KAIT, subject to weather and seasonal visibility. The gamma-ray coverage is essentially continuous. KAIT observations extend over much of the five-year Fermi mission for several objects, and most have >100 optical measurements spanning the last three years. These blazars (flat-spectrum radio quasars and BL Lac objects) exhibit a wide range of flaring behavior. Using the discrete correlation function (DCF), here we search for temporal relationships between optical and gamma-ray light curves in the 40 brightest sources in hopes of placing constraints on blazar acceleration and emission zones. We find strong optical-gamma-ray correlation in many of these sources at time delays of ~1 to ~10 days, ranging between -40 and +30 days. A stacked average DCF of the 40 sources verifies this correlation trend, with a peak above 99% significance indicating a characteristic time delay consistent with 0 days. These findings strongly support the widely accepted leptonic models of blazar emission. However, we also find examples of apparently uncorrelated flares (optical flares with no gamma-ray counterpart and gamma-ray flares with no optical counterpart) that challenge simple, one-zone models of blazar emission. Moreover, we find that flat-spectrum radio quasars tend to have gamma-rays leading the optical, while intermediate- and high-synchrotron peak blazars with the most significant peaks have smaller lags/leads. It is clear that long-term monitoring at high cadence is necessary to reveal the underlying physical correlation.

  10. TEMPORAL CORRELATIONS BETWEEN OPTICAL AND GAMMA-RAY ACTIVITY IN BLAZARS

    SciTech Connect

    Cohen, Daniel P.; Filippenko, Alexei V.; Zheng, WeiKang; Li, Weidong; Romani, Roger W.; Cenko, S. Bradley

    2014-12-20

    We have been using the 0.76 m Katzman Automatic Imaging Telescope (KAIT) at Lick Observatory to optically monitor a sample of 157 blazars that are bright in gamma-rays being detected with high significance (≥10σ) in one year by the Large Area Telescope (LAT) on the Fermi Gamma-ray Space Telescope. We attempt to observe each source on a three-day cadence with KAIT, subject to weather and seasonal visibility. The gamma-ray coverage is essentially continuous. KAIT observations extend over much of the five-year Fermi mission for several objects, and most have >100 optical measurements spanning the last three years. These blazars (flat-spectrum radio quasars and BL Lac objects) exhibit a wide range of flaring behavior. Using the discrete correlation function (DCF), here we search for temporal relationships between optical and gamma-ray light curves in the 40 brightest sources in hopes of placing constraints on blazar acceleration and emission zones. We find strong optical-gamma-ray correlation in many of these sources at time delays of ∼1 to ∼10 days, ranging between –40 and +30 days. A stacked average DCF of the 40 sources verifies this correlation trend, with a peak above 99% significance indicating a characteristic time delay consistent with 0 days. These findings strongly support the widely accepted leptonic models of blazar emission. However, we also find examples of apparently uncorrelated flares (optical flares with no gamma-ray counterpart and gamma-ray flares with no optical counterpart) that challenge simple, one-zone models of blazar emission. Moreover, we find that flat-spectrum radio quasars tend to have gamma-rays leading the optical, while intermediate- and high-synchrotron peak blazars with the most significant peaks have smaller lags/leads. It is clear that long-term monitoring at high cadence is necessary to reveal the underlying physical correlation.

  11. Micro-arcsecond stucture in blazar PKS 1257-326

    NASA Astrophysics Data System (ADS)

    Hodgson, Jeffrey; Bignall, Hayley; Ellingsen, Simon; Fuhrmann, Lars; Godfrey, Leith; Shabala, Stanislav; Krichbaum, Thomas P.; Savolainen, Tuomas

    2012-10-01

    We propose to monitor the intra-hour variable scintillating blazar PKS 1257-326, using the wide bandwidth provided by the CABB system, to investigate the structure and evolution of an ultracompact radio jet, with micro-arcsecond scale resolution. This probes within ~100 Schwarzschild radii of the 10^9 solar mass black hole in this quasar at redshift z=1.256. An earlier study of the frequency-dependent structure has shown evidence of properties that are inconsistent with standard models of a conical jet. Additionally, earlier (pre-CABB) observations showed evidence of changes in source opacity on microarcsecond scales, correlated with total flux density and spectral index variations. Regular observations with the CABB system will allow detailed investigation of the jet physics, and the construction of a model of the microarcsecond-scale frequency-dependent structure that can be compared against larger milli-arcsecond scale structure and intrinsic flux density changes. The novel technique we propose achieves resolution more than an order of magnitude better than VLBI, with only a 6km array. Rapid scintillators have been known to ‘switch off’, making observing as soon as possible imperative.

  12. TeV blazar variability: the firehose instability?

    NASA Astrophysics Data System (ADS)

    Subramanian, Prasad; Becker, Peter; Shukla, Amit

    2012-07-01

    Recently observed minute timescale variability of blazar emission at TeV energies has imposed severe constraints on jet models and TeV emission mechanisms. %The TeV emission is assumed to be due to inverse Compton emission off the electrons, which have a random Lorentz factor γ ˜ 10^6. We focus on a robust jet instability to explain this variability. As a consequence of the bulk outflow of the jet plasma, the pressure is likely to be anisotropic, with the parallel pressure P_{||} in the forward jet direction exceeding the perpendicular pressure P_{\\perp}. Under these circumstances, the jet is susceptible to the firehose instability, which can cause disruptions in the large scale jet structure and result in variability of the observed radiation. %We investigate if the large-scale structure of the jet can be disrupted by the firehose instability. For a realistic range of parameters, we find that the growth timescale of the firehose instability is ≈ a few minutes, in good agreement with the observed TeV variability timescales for Mrk 501 (Albert et al. 2007) and PKS 2155-304 (Aharonian et al. 2007). %We therefore conclude that the relativistic firehose instability is a viable candidate for explaining minute timescale TeV variability.

  13. [Measurement of multi-wavelength pulse oxygen saturation based on dynamic spectroscopy].

    PubMed

    Wang, Xiao-Fei; Zhao, Wen-Jun

    2014-05-01

    The present paper puts forward multi-wavelength pulse oxygen saturation measurement based on dynamic spectroscopy to do the non-invasive determination of oxygen saturation. Compared to conventional ways, the new method makes full use of more wavelengths light and improves the measurement accuracy. During the experiment, the in-vivo measurements were carried out on 60 patients and their spectroscopic data were collected by the high sensitivity type fiber optic spectrometer. Singletrial estimation method was used to extract the dynamic spectroscopy at the wavelengths of 606. 44 approximately 987. 55 nm. Oxygen saturation obtained from arterial blood gas analysis is regarded as the true value. Synergy interval partial least square (siPLS) was used to establish the calibration model of subjects' oxygen saturation values against dynamic spectroscopy data. The relative error of prediction is +/-0. 017 6, but the relative error of the subjects in the same set measured by the patient monitor which was two-wavelength measure system is +/-0. 116 4. Measurement results show that the use of the high sensitivity type fiber optic spectrometer to collect multi-wavelength spectroscopic data and dynamic spectroscopy method to process data can do better in improving the accuracy of the oxygen saturation measurement. PMID:25095431

  14. Magnetic reconnection signatures in the solar atmosphere: results from multi-wavelength observations

    NASA Astrophysics Data System (ADS)

    Zuccarello, F.; Guglielmino, S. L.; Romano, P.

    In the solar atmosphere magnetic reconnection is invoked as the main mechanism causing very energetic events (1028 - 1032 erg), like flares and coronal mass ejections, as well as other less energetic phenomena, like microflares, X-ray jets and chromospheric surges. In the last decade, thanks to high spatial resolution, multi-wavelength observations carried out by both ground-based telescopes (THEMIS, SST, VTT, DST) and space-born satellites (SOHO, TRACE, RHESSI, HINODE), it has been possible to study these phenomena and several signatures of the occurrence of magnetic reconnection have been singled out. In this paper, we describe some results obtained from the analysis of multi-wavelength observations carried out in the last years, with special emphasis on those events that were characterized by plasma outflows from the reconnection site. The events here discussed are relevant to some active regions observed on the Sun, characterized by the interaction of different bundles of magnetic flux tubes, as a consequence of phenomena of emergence of new magnetic flux from the subphotospheric layers and/or of cancellation of magnetic fragments. We report on these phenomena in order to give a contribution to the possibility to find a similarity with jets observed in AGNs.

  15. A significant hardening and rising shape detected in the MeV/GeV νFν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February

    NASA Astrophysics Data System (ADS)

    Tanaka, Yasuyuki T.; Becerra Gonzalez, Josefa; Itoh, Ryosuke; Finke, Justin D.; Inoue, Yoshiyuki; Ojha, Roopesh; Carpenter, Bryce; Lindfors, Elina; Krauß, Felicia; Desiante, Rachele; Shiki, Kensei; Fukazawa, Yasushi; Longo, Francesco; McEnery, Julie E.; Buson, Sara; Nilsson, Kari; Fallah Ramazani, Vandad; Reinthal, Riho; Takalo, Leo; Pursimo, Tapio; Boschin, Walter

    2016-08-01

    We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z = 0.368) during an exceptionally bright optical flare in 2015 February. During the time period (2015 February 13/14, or MJD 57067) when the MAGIC telescope detected VHE γ-ray emission from the source, the Fermi-LAT data indicated a significant spectral hardening at GeV energies, with a power-law photon index of 1.8 ± 0.1-compared with the 3FGL (The Fermi LAT 4-Year Point Source Catalog) value (averaged over four years of observation) of 2.34 ± 0.04. In contrast, Swift X-Ray Telescope data showed a softening of the X-ray spectrum, with a photon index of 1.72 ± 0.08 (compared with 1.38 ± 0.03 averaged during the flare from MJD 57066 to 57077), possibly indicating a modest contribution of synchrotron photons by the highest-energy electrons superposed on the inverse Compton component. Fitting of the quasi-simultaneous (<1 d) broad-band spectrum with a one-zone synchrotron plus inverse-Compton model revealed that GeV/TeV emission could be produced by inverse-Compton scattering of external photons from the dust torus. We emphasize that a flaring blazar showing high flux of ≳1.0 × 10-6 photons cm-2 s-1 (E > 100 MeV) and a hard spectral index of ΓGeV < 2.0 detected by Fermi-LAT on daily timescales is a promising target for TeV follow-up by ground-based Cherenkov telescopes to discover high-redshift blazars, investigate their temporal variability and spectral features in the VHE band, and also constrain the intensity of the extragalactic background light.

  16. A significant hardening and rising shape detected in the MeV/GeV νFν spectrum from the recently discovered very-high-energy blazar S4 0954+65 during the bright optical flare in 2015 February

    NASA Astrophysics Data System (ADS)

    Tanaka, Yasuyuki T.; Becerra Gonzalez, Josefa; Itoh, Ryosuke; Finke, Justin D.; Inoue, Yoshiyuki; Ojha, Roopesh; Carpenter, Bryce; Lindfors, Elina; Krauß, Felicia; Desiante, Rachele; Shiki, Kensei; Fukazawa, Yasushi; Longo, Francesco; McEnery, Julie E.; Buson, Sara; Nilsson, Kari; Fallah Ramazani, Vandad; Reinthal, Riho; Takalo, Leo; Pursimo, Tapio; Boschin, Walter

    2016-05-01

    We report on Fermi Large Area Telescope (LAT) and multi-wavelength results on the recently discovered very-high-energy (VHE, E > 100 GeV) blazar S4 0954+65 (z = 0.368) during an exceptionally bright optical flare in 2015 February. During the time period (2015 February 13/14, or MJD 57067) when the MAGIC telescope detected VHE γ-ray emission from the source, the Fermi-LAT data indicated a significant spectral hardening at GeV energies, with a power-law photon index of 1.8 ± 0.1-compared with the 3FGL (The Fermi LAT 4-Year Point Source Catalog) value (averaged over four years of observation) of 2.34 ± 0.04. In contrast, Swift X-Ray Telescope data showed a softening of the X-ray spectrum, with a photon index of 1.72 ± 0.08 (compared with 1.38 ± 0.03 averaged during the flare from MJD 57066 to 57077), possibly indicating a modest contribution of synchrotron photons by the highest-energy electrons superposed on the inverse Compton component. Fitting of the quasi-simultaneous (<1 d) broad-band spectrum with a one-zone synchrotron plus inverse-Compton model revealed that GeV/TeV emission could be produced by inverse-Compton scattering of external photons from the dust torus. We emphasize that a flaring blazar showing high flux of ≳1.0 × 10-6 photons cm-2 s-1 (E > 100 MeV) and a hard spectral index of ΓGeV < 2.0 detected by Fermi-LAT on daily timescales is a promising target for TeV follow-up by ground-based Cherenkov telescopes to discover high-redshift blazars, investigate their temporal variability and spectral features in the VHE band, and also constrain the intensity of the extragalactic background light.

  17. Multiwavelength LIDAR for remote sensing of chlorophyll A in algae and phytoplankton

    NASA Technical Reports Server (NTRS)

    Mumola, P. B.; Jarrett, O., Jr.; Brown, C. A., Jr.

    1975-01-01

    A theoretical and experimental analysis of laser induced fluorescence for remote detection of chlorophyll A in living algae and phytoplankton is presented. The fluorescent properties of various species of algae representative of the different color groups are described. Laboratory measurements of fluorescent scattering cross sections is discussed and quantitive data presented. A scattering matrix model is developed to demonstrate the essential requirement of multiwavelength laser excitation in order to make accurate quantitative measurements of chlorophyll A concentration when more than one color group of algae is present in the water. A practical airborne laser fluorosensor design is considered and analysis of field data discussed. Successful operation of the Langley ALOPE (airborne LIDAR oceanographic probing experiment) system is described and field measurements presented. Accurate knowledge of alpha, the optical attenuation coefficient of the water, is shown to be essential for quantitative analysis of chlorophyll A concentration. The feasibility of remotely measuring alpha by laser radar is discussed.

  18. Multiwavelength fiber laser for the fiber link monitoring system

    NASA Astrophysics Data System (ADS)

    Peng, Peng-Chun; Lee, Wei-Yun; Wu, Shin-Shian; Hu, Hsuan-Lun

    2013-10-01

    This work proposes a novel fiber link monitoring system that uses a multiwavelength fiber laser for wavelength-division-multiplexed (WDM) passive optical network (PON). The multiwavelength fiber laser is based on an erbium-doped fiber amplifier (EDFA) and a semiconductor optical amplifier (SOA). Experimental results show the feasibility using the system to monitor a fiber link with a high and stable signal-to-noise ratio (SNR) of over 26 dB. The link quality of downstream signals as well as the fiber link on WDM channels can be monitored in real time. Favorable carrier-to-noise ratio (CNR), composite second-order (CSO), and composite triple beat (CTB) performance metrics were obtained for cable television (CATV) signals that were transported through 25 km of standard single-mode fiber (SMF).

  19. Temperature Measurement of Ceramic Materials Using a Multiwavelength Pyrometer

    NASA Technical Reports Server (NTRS)

    Ng, Daniel; Fralick, Gustave

    1999-01-01

    The surface temperatures of several pure ceramic materials (alumina, beryllia, magnesia, yittria and spinel) in the shape of pellets were measured using a multiwavelength pyrometer. In one of the measurements, radiation signal collection is provided simply by an optical fiber. In the other experiments, a 4.75 inch (12 cm) parabolic mirror collects the signal for the spectrometer. Temperature measurement using the traditional one- and two-color pyrometer for these ceramic materials is difficult because of their complex optical properties, such as low emissivity which varies with both temperature and wavelength. In at least one of the materials, yittria, the detected optical emission increased as the temperature was decreased due to such emissivity variation. The reasons for such changes are not known. The multiwavelength pyrometer has demonstrated its ability to measure surface temperatures under such conditions. Platinum electrodes were embedded in the ceramic pellets for resistance measurements as the temperature changed.

  20. GLAST: GeV astronomy in a multiwavelength context

    NASA Astrophysics Data System (ADS)

    Thompson, David J.

    2004-04-01

    The GLAST Large Area Telescope (LAT), successor to Energetic Gamma-ray Experiment Telescope (EGRET) on the Compton Observatory, will play an important role in multiwavelength studies during the second half of this decade. Operating at energies between 20 MeV and greater than 300 GeV with sensitivity 30 or more times greater than that of EGRET, the LAT will offer good spatial and time resolution over a large (>2 sr) field of view. The LAT will bring insight to the whole range of high-energy γ-ray phenomena, including bursts, active galactic nuclei, pulsars, supernova remnants, diffuse emission and unidentified sources. In essentially all cases, the maximum scientific return will come from coordinated (although not necessarily simultaneous) multiwavelength observations. Particularly with its planned scanning mode of operation, GLAST will have full sky coverage on relatively short time scales. The LAT team looks forward to cooperating with observers at other wavelengths.

  1. Multiwavelength AGN Surveys and Studies (IAU S304)

    NASA Astrophysics Data System (ADS)

    Mickaelian, Areg M.; Sanders, David B.

    2014-08-01

    1. Historical surveys: spectral and colorimetric surveys for AGN, surveys for UV-excess galaxies; 2. AGN from IR/submm surveys: 2MASS, IRAS, ISO, AKARI, SCUBA, SST, WISE, Herschel; 3. AGN from radio/mm surveys: NVSS, FIRST, ALMA, Planck, and others; 4. AGN from X-ray/gamma-ray surveys: ROSAT, ASCA, BeppoSAX, Chandra, XMM, INTEGRAL, Fermi, HESS, MAGIC, VERITAS, NuSTAR; 5. Multiwavelength AGN surveys, AGN statistics and cross-correlation of multiwavelength surveys; 6. Unification and other models of AGN, accretion modes, understanding of the structure of nearby AGN from IFUs on VLT and other telescopes; 7. AGN feedback in galaxies and clusters, AGN host galaxies and the AGN environments; 8. Binary AGN and Merging Super-Massive Black Holes; 9. Study of unique AGN, AGN variability and the Phenomena of Activity; 10. Future large projects; Author index.

  2. Identification of aerosol composition from multi-wavelength lidar measurements

    NASA Technical Reports Server (NTRS)

    Wood, S. A.

    1984-01-01

    This paper seeks to develop the potential of lidar for the identification of the chemical composition of atmospheric aerosols. Available numerical computations suggest that aerosols can be identified by the wavelength dependence of aerosol optical properties. Since lidar can derive the volume backscatter coefficient as a function of wavelength, a multi-wavelength lidar system may be able to provide valuable information on the composition of aerosols. This research theoretically investigates the volume backscatter coefficients for the aerosol classes, sea-salts, and sulfates, as a function of wavelength. The results show that these aerosol compositions can be characterized and identified by their backscatter wavelength dependence. A method to utilize multi-wavelength lidar measurements to discriminate between compositionally different thin aerosol layers is discussed.

  3. Hints of an axion-like particle mixing in the GeV gamma-ray blazar data?

    SciTech Connect

    Mena, Olga; Razzaque, Soebur E-mail: srazzaque@uj.ac.za

    2013-11-01

    Axion-Like Particles (ALPs), if exist in nature, are expected to mix with photons in the presence of an external magnetic field. The energy range of photons which undergo strong mixing with ALPs depends on the ALP mass, on its coupling with photons as well as on the external magnetic field and particle density configurations. Recent observations of blazars by the Fermi Gamma-Ray Space Telescope in the 0.1–300 GeV energy range show a break in their spectra in the 1–10 GeV range. We have modeled this spectral feature for the flat-spectrum radio quasar 3C454.3 during its November 2010 outburst, assuming that a significant fraction of the gamma rays convert to ALPs in the large scale jet of this blazar. Using theoretically motivated models for the magnetic field and particle density configurations in the kiloparsec scale jet, outside the broad-line region, we find an ALP mass m{sub a} ∼ (1−3)⋅10{sup −7} eV and coupling g{sub aγ} ∼ (1−3)⋅10{sup −10} GeV{sup −1} after performing an illustrative statistical analysis of spectral data in four different epochs of emission. The precise values of m{sub a} and g{sub aγ} depend weakly on the assumed particle density configuration and are consistent with the current experimental bounds on these quantities. We apply this method and ALP parameters found from fitting 3C454.3 data to another flat-spectrum radio quasar PKS1222+216 (4C+21.35) data up to 400 GeV, as a consistency check, and found good fit. We find that the ALP-photon mixing effect on the GeV spectra may not be washed out for any reasonable estimate of the magnetic field in the intergalactic media.

  4. The polarization dependence of γγ absorption—implications for γ-ray bursts and blazars

    SciTech Connect

    Böttcher, M.

    2014-11-01

    This paper presents an analysis of the dependence of the opacity for high-energy γ-rays to γγ absorption by low-energy photons on the polarization of the γ-ray and target photons. This process has so far only been considered using the polarization-averaged γγ absorption cross section. It is demonstrated that in the case of polarized γ-ray emission, subject to source-intrinsic γγ absorption by polarized target photons, this may lead to a slight overestimation of the γγ opacity by up to ∼10% in the case of a perfectly ordered magnetic field. Thus, for realistic astrophysical scenarios with partially ordered magnetic fields, the use of the polarization-averaged γγ cross section is justified for practical purposes, such as estimates of minimum Doppler factors inferred for γ-ray bursts and blazars, based on γγ transparency arguments; this paper quantifies the small error incurred by the unpolarized-radiation approximation. Furthermore, it is shown that polarization-dependent γγ absorption of initially polarized γ-rays can lead to a slight increase in the polarization beyond the spectral break caused by γγ absorption. This amount is distinctly different from the change in polarization expected if the same spectral break were produced by a break in the underlying electron distribution. This may serve as a diagnostic of whether γγ absorption is relevant in sources such as γ-ray bursts and blazars where the γ-ray emission may be intrinsically highly polarized.

  5. MULTIWAVELENGTH OBSERVATIONS OF 3C 454.3. III. EIGHTEEN MONTHS OF AGILE MONITORING OF THE 'CRAZY DIAMOND'

    SciTech Connect

    Vercellone, S.; Romano, P.; Ferrari, A.; Chen, A. W.; Raiteri, C. M.; Villata, M.; Krimm, H.; Tiengo, A.; Venturi, T.; Giroletti, M.; Lister, M. L.

    2010-03-20

    We report on 18 months of multiwavelength observations of the blazar 3C 454.3 (Crazy Diamond) carried out in the period 2007 July-2009 January. In particular, we show the results of the AGILE campaigns which took place on 2008 May-June, 2008 July-August, and 2008 October-2009 January. During the 2008 May-2009 January period, the source average flux was highly variable, with a clear fading trend toward the end of the period, from an average gamma-ray flux F{sub E>100{sub MeV}} {approx}> 200 x 10{sup -8} photons cm{sup -2} s{sup -1} in 2008 May-June, to F{sub E>100{sub MeV}} {approx} 80 x 10{sup -8} photons cm{sup -2} s{sup -1} in 2008 October-2009 January. The average gamma-ray spectrum between 100 MeV and 1 GeV can be fit by a simple power law, showing a moderate softening (from GAMMA{sub GRID} {approx} 2.0 to GAMMA{sub GRID} {approx} 2.2) toward the end of the observing campaign. Only 3sigma upper limits can be derived in the 20-60 keV energy band with Super-AGILE, because the source was considerably off-axis during the whole time period. In 2007 July-August and 2008 May-June, 3C 454.3 was monitored by Rossi X-ray Timing Explorer (RXTE). The RXTE/Proportional Counter Array (PCA) light curve in the 3-20 keV energy band shows variability correlated with the gamma-ray one. The RXTE/PCA average flux during the two time periods is F{sub 3-20{sub keV}} = 8.4 x 10{sup -11} erg cm{sup -2} s{sup -1}, and F{sub 3-20{sub keV}} = 4.5 x 10{sup -11} erg cm{sup -2} s{sup -1}, respectively, while the spectrum (a power law with photon index GAMMA{sub PCA} = 1.65 +- 0.02) does not show any significant variability. Consistent results are obtained with the analysis of the RXTE/High-Energy X-Ray Timing Experiment quasi-simultaneous data. We also carried out simultaneous Swift observations during all AGILE campaigns. Swift/XRT detected 3C 454.3 with an observed flux in the 2-10 keV energy band in the range (0.9-7.5) x 10{sup -11} erg cm{sup -2} s{sup -1} and a photon index in the range

  6. Temperature Measurement of a Glass Material Using a Multiwavelength Pyrometer

    NASA Technical Reports Server (NTRS)

    Ng, Daniel

    1997-01-01

    Temperature measurement of a substance that is transparent using the traditional 1-color, 2-color and other pyrometers has been difficult. The radiation detected by pyrometers do not come from a well defined location in the transparent body. The multiwavelength pyrometer developed at the NASA Lewis Research Center can measure the surface temperature of many materials. We show in this paper that it also measures the surface and a bulk subsurface temperature of transparent materials like glass.

  7. Monte Carlo studies of multiwavelength pyrometry using linearized equations

    NASA Astrophysics Data System (ADS)

    Gathers, G. R.

    1992-03-01

    Multiwavelength pyrometry has been advertised as giving significant improvement in precision by overdetermining the solution with extra wavelengths and using least squares methods. Hiernaut et al. [1] have described a six-wavelength pyrometer for measurements in the range 2000 to 5000 K. They use the Wien approximation and model the logarithm of the emissivity as a linear function of wavelength in order to produce linear equations. The present work examines the measurement errors associated with their technique.

  8. A determination of the gamma-ray flux and photon spectral index distributions of blazars from the Fermi-LAT 3LAC

    NASA Astrophysics Data System (ADS)

    Singal, J.

    2015-11-01

    We present a determination of the distributions of gamma-ray photon flux - the so-called LogN-LogS relation - and photon spectral index for blazars, based on the third extragalactic source catalogue of the Fermi Gamma-ray Space Telescope's Large Area Telescope, and considering the photon energy range from 100 MeV to 100 GeV. The data set consists of the 774 blazars in the so-called Clean sample detected with a greater than approximately 7σ detection threshold and located above ±20° Galactic latitude. We use non-parametric methods verified in previous works to reconstruct the intrinsic distributions from the observed ones which account for the data truncations introduced by observational bias and includes the effects of the possible correlation between the flux and photon index. The intrinsic flux distribution can be represented by a broken power law with a high-flux power-law index of -2.43 ± 0.08 and a low-flux power-law index of -1.87 ± 0.10. The intrinsic photon index distribution can be represented by a Gaussian with mean of 2.62 ± 0.05 and width of 0.17 ± 0.02. We also report the intrinsic distributions for the subpopulations of BL Lac and FSRQ (Flat Spectrum Radio Quasar)-type blazars separately and these differ substantially. We then estimate the contribution of FSRQs and BL Lacs to the diffuse extragalactic gamma-ray background radiation. Under the simplistic assumption that the flux distributions probed in this analysis continue to arbitrary low flux, we calculate that the best-fitting contribution of FSRQs is 35 per cent and BL Lacs 17 per cent of the total gamma-ray output of the Universe in this energy range.

  9. Distributions of gamma-ray bursts and blazars in the L {sub p}-E {sub p}-plane and possible implications for their radiation physics

    SciTech Connect

    Lyu, Fen; Liang, En-Wei; Liang, Yun-Feng; Sun, Xiao-Na; Lu, Rui-Jing; Zhang, Bing; Wu, Xue-Feng; Zhang, Jin E-mail: xfwu@pmo.ac.cn

    2014-09-20

    We present a spectral analysis for a sample of redshift-known gamma-ray bursts (GRBs) observed with Fermi/GBM. Together with the results derived from our systematical spectral energy distribution modeling with the leptonic models for a Fermi/LAT blazar sample, we compare the distributions of the GRBs and the blazars by plotting the synchrotron peak luminosity (L {sub s}) and the corresponding peak photon energy E {sub s} of blazars in the L {sub p}-E {sub p}-plane of GRBs, where L {sub p} and E {sub p} are the peak luminosity and peak photon energy of the GRB time-integrated νf {sub ν} spectrum, respectively. The GRBs are in the high-L {sub p}, high-E {sub p} corner of the plane and a tight L {sub p}-E {sub p} relation is found, i.e., L{sub p}∝E{sub p}{sup 2.13{sub −}{sub 0}{sub .}{sub 4}{sub 6}{sup +{sup 0{sup .{sup 5{sup 4}}}}}}. Both flat spectrum radio quasars (FSRQs) and low-synchrotron peaking BL Lac objects (LBLs) are clustered in the low-E {sub p}, low-L {sub p} corner. Intermediate- and high-synchrotron peaking BL Lac objects (IBLs and HBLs) have E {sub s} ∼ 2 × 10{sup –3}-10{sup 2} keV and L {sub s} ∼ 10{sup 44}-10{sup 47} erg s{sup –1}, but no dependence of L {sub s} on E {sub s} is found. We show that the tight L{sub p} -E{sub p} relation of GRBs is potentially explained with the synchrotron radiation of fast-cooling electrons in a highly magnetized ejecta, and the weak anti-correlation of L {sub s}-E {sub s} for FSRQs and LBLs may be attributed to synchrotron radiation of slow-cooling electrons in a moderately magnetized ejecta. The distributions of IBLs and HBLs in the L {sub p}-E {sub p}-plane may be interpreted with synchrotron radiation of fast-cooling electrons in a matter-dominated ejecta. These results may present a unified picture for the radiation physics of relativistic jets in GRBs and blazars within the framework of the leptonic synchrotron radiation models.

  10. Distributions of Gamma-Ray Bursts and Blazars in the L p-E p-Plane and Possible Implications for their Radiation Physics

    NASA Astrophysics Data System (ADS)

    Lyu, Fen; Liang, En-Wei; Liang, Yun-Feng; Wu, Xue-Feng; Zhang, Jin; Sun, Xiao-Na; Lu, Rui-Jing; Zhang, Bing

    2014-09-01

    We present a spectral analysis for a sample of redshift-known gamma-ray bursts (GRBs) observed with Fermi/GBM. Together with the results derived from our systematical spectral energy distribution modeling with the leptonic models for a Fermi/LAT blazar sample, we compare the distributions of the GRBs and the blazars by plotting the synchrotron peak luminosity (L s) and the corresponding peak photon energy E s of blazars in the L p-E p-plane of GRBs, where L p and E p are the peak luminosity and peak photon energy of the GRB time-integrated νf ν spectrum, respectively. The GRBs are in the high-L p, high-E p corner of the plane and a tight L p-E p relation is found, i.e., L_p\\propto E_p2.13^{+0.54-0.46}. Both flat spectrum radio quasars (FSRQs) and low-synchrotron peaking BL Lac objects (LBLs) are clustered in the low-E p, low-L p corner. Intermediate- and high-synchrotron peaking BL Lac objects (IBLs and HBLs) have E s ~ 2 × 10-3-102 keV and L s ~ 1044-1047 erg s-1, but no dependence of L s on E s is found. We show that the tight Lp -Ep relation of GRBs is potentially explained with the synchrotron radiation of fast-cooling electrons in a highly magnetized ejecta, and the weak anti-correlation of L s-E s for FSRQs and LBLs may be attributed to synchrotron radiation of slow-cooling electrons in a moderately magnetized ejecta. The distributions of IBLs and HBLs in the L p-E p-plane may be interpreted with synchrotron radiation of fast-cooling electrons in a matter-dominated ejecta. These results may present a unified picture for the radiation physics of relativistic jets in GRBs and blazars within the framework of the leptonic synchrotron radiation models.

  11. Variability in blazars: clues from PKS 2155-304

    NASA Astrophysics Data System (ADS)

    Narayan, Ramesh; Piran, Tsvi

    2012-02-01

    Rapid variability on a time-scale much faster than the light-crossing time of the central supermassive black hole has been seen in TeV emission from the blazar PKS 2155-304. The most plausible explanation for this puzzling observation is that the radiating fluid in the relativistic jet is divided into a large number of subregions which move in random directions with relative Lorentz factors ?. The random motions introduce new relativistic effects, over and above those due to the overall mean bulk Lorentz factor Γb of the jet. We consider two versions of this 'jets in a jet' model. In the first, the 'subjets' model, stationary regions in the mean jet frame emit relativistic subjets that produce the observed radiation. The variability time-scale is determined by the size of the subregions in the mean jet frame. This model, which is loosely based on magnetic reconnection, has great difficulty explaining the observations in PKS 2155-304. In the alternate 'turbulence' model, various subregions move relativistically in random directions and the variability time-scale is determined by the size of these regions in their own comoving frames. This model fits the data much more comfortably. Details such as what generates the turbulent motion, how particles are heated, and what the radiation process is, remain to be worked out. We consider collisions between TeV photons and soft photons and find that, in both the subjets and turbulence models, the mean bulk Lorentz factor Γb of the jet needs to be >25 to avoid the pair catastrophe.

  12. Multi-wavelength differential absorption measurements of chemical species

    NASA Astrophysics Data System (ADS)

    Brown, David M.

    algorithms to select filters for use with a MWIR (midwave infrared) imager for detection of plumes of methane, propane, gasoline vapor, and diesel vapor. These simulations were prepared for system designs operating on a down-looking airborne platform. A data analysis algorithm for use with a hydrocarbon imaging system extracts regions of interest from the field-of-view for further analysis. An error analysis is presented for a scanning DAS (Differential Absorption Spectroscopy) lidar system operating from an airborne platform that uses signals scattered from topographical targets. The analysis is built into a simulation program for testing real-time data processing approaches, and to gauge the effects on measurements of path column concentration due to ground reflectivity variations. An example simulation provides a description of the data expected for methane. Several accomplishments of this research include: (1) A new lidar technique for detection and measurement of concentrations of atmospheric species is demonstrated that uses a low-power supercontinuum source. (2) A new multi-wavelength algorithm, which demonstrates excellent performance, is applied to processing spectroscopic data collected by a longpath supercontinuum laser absorption instrument. (3) A simulation program for topographical scattering of a scanning DAS system is developed, and it is validated with aircraft data from the ITT Industries ANGEL (Airborne Natural Gas Emission Lidar) 3-lambda lidar system. (4) An error analysis procedure for DAS is developed, and is applied to measurements and simulations for an airborne platform. (5) A method for filter selection is developed and tested for use with an infrared imager that optimizes the detection for various hydrocarbons that absorb in the midwave infrared. (6) The development of a Fourier analysis algorithm is described that allows a user to rapidly separate hydrocarbon plumes from the background features in the field of view of an imaging system.

  13. The extension of variability properties in gamma-ray bursts to blazars

    NASA Astrophysics Data System (ADS)

    Wu, Qingwen; Zhang, Bing; Lei, Wei-Hua; Zou, Yuan-Chuan; Liang, En-Wei; Cao, Xinwu

    2016-01-01

    Both gamma-ray bursts (GRBs) and blazars have relativistic jets pointing at a small angle from our line of sight. Several recent studies suggested that these two kinds of sources may share similar jet physics. In this work, we explore the variability properties for GRBs and blazars as a whole. We find that the correlation between minimum variability time-scale (MTS) and Lorentz factor, Γ, as found only in GRBs by Sonbas et al. can be extended to blazars with a joint correlation of MTS∝Γ-4.7±0.3. The same applies to the MTS∝ L_{γ }^{-1.0± 0.1} correlation as found in GRBs, which can be well extended into blazars as well. These results provide further evidence that the jets in these two kinds of sources are similar despite of the very different mass scale of their central engines. Further investigations of the physical origin of these correlations are needed, which can shed light on the nature of the jet physics.

  14. VERITAS Observations of Six Bright, Hard-Spectrum Fermi-LAT Blazars

    NASA Technical Reports Server (NTRS)

    E. Aliu; Archambault, S.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Boettcher, M.; Bouvier, A.; Buckley, J. H.; Bugaev, V.; Cesarini, A.; Ciupick, L.; Collins-Hughes, E.; Connolly, M. P.; Cui, W.; Dickherber, R.; Duke, C.; Dumm, J.; Erando, M.; Falcone, A.; Federici, S.; Feng, Q.; Finley, J. P.; Finnegan, G.; Perkins, J. S.

    2012-01-01

    We report on VERITAS very-high-energy (VHE; E >= 100 GeV) observations of six blazars selected from the Fermi Large Area Telescope First Source Catalog (1FGL). The gamma-ray emission from 1FGL sources was extrapolated up to the VHE band, taking gamma-ray absorption by the extragalactic background light into account. This allowed the selection of six bright, hard-spectrum blazars that were good candidate TeV emitters. Spectroscopic redshift measurements were attempted with the Keck Telescope for the targets without Sloan Digital Sky Survey (SDSS) spectroscopic data. No VHE emission is detected during the observations of the six sources described here. Corresponding TeV upper limits are presented, along with contemporaneous Fermi observations and non-concurrent Swift UVOT and XRT data. The blazar broadband spectral energy distributions (SEDs) are assembled and modeled with a single-zone synchrotron self-Compton model. The SED built for each of the six blazars show a synchrotron peak bordering between the intermediate- and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission region.

  15. Short-term flux and colour variations in low-energy peaked blazars

    NASA Astrophysics Data System (ADS)

    Rani, Bindu; Gupta, Alok C.; Strigachev, A.; Bachev, R.; Wiita, Paul J.; Semkov, E.; Ovcharov, E.; Mihov, B.; Boeva, S.; Peneva, S.; Spassov, B.; Tsvetkova, S.; Stoyanov, K.; Valcheva, A.

    2010-06-01

    We have measured multiband optical flux and colour variations for a sample of 12 low-energy peaked blazars (LBLs) on short, day-to-month, time-scales. Our sample contains six BL Lacertae objects (BL Lacs) and six flat spectrum radio quasars (FSRQs). These photometric observations, made during 2008 September to 2009 June, used five optical telescopes, one in India and four in Bulgaria. We detected short-term flux variations in 11 of these blazars and colour variability in eight of them. Our data indicate that six blazars (3C 66A, AO 0235+164, S50716+714, PKS 0735+178, OJ 287 and 3C 454.3) were observed in pre- or post-outburst states, five (PKS 0420-014, 4C 29.45, 3C 279, PKS 1510-089 and BL Lac) were in a low state, while one (3C 273) was in an essentially steady state. The duty cycles for flux and colour variations on short time-scales in these LBLs are ~92 and ~33 per cent, respectively. The colour versus magnitude correlations seen here support the hypothesis that BL Lac objects tend to become bluer with increase in brightness; however, FSRQs may show the opposite trend, and there are exceptions to these trends in both categories of blazar. We briefly discuss emission models for active galactic nuclei that might explain our results.

  16. Lower limits on ultrahigh-energy cosmic ray and jet powers of TeV blazars

    NASA Astrophysics Data System (ADS)

    Razzaque, Soebur; Dermer, Charles; Finke, Justin

    2012-03-01

    Lower limits on the power emitted in ultrahigh-energy cosmic ray (UHECR) protons are derived for TeV blazars with the assumption that the observed TeV gamma rays are generated due to interactions of these protons with cosmic microwave photons. This mechanism may be at work in four blazars, namely 1ES 0229+200; 1ES 1101-232; 1ES 0347-121 and 1ES 1426+428, which are at sufficiently high redshift (>0.1) that allow efficient cascade development to make TeV emission and which are non-varying or very weakly varying at >TeV energies. The lower limits on the UHECR power are lower than the respective synchrotron luminosities in case of all blazars except for 1ES 1426+428. The proposed Auger North Observatory can detect 40 EeV cosmic rays from this extraordinary source and test the UHECR-generated TeV emission model, which requires the intergalactic magnetic field strength to be below 10-16 G. The lower limits on the jet power for all four TeV blazars exceed the Eddington luminosity of a 10^9 solar mass black hole in case the injected UHECR spectrum is softer than -2.2.

  17. The Influence of Plasma Effects of Pair Beams on the Intergalactic Cascade Emission of Blazars

    NASA Astrophysics Data System (ADS)

    Menzler, Ulf; Schlickeiser, Reinhard

    2014-03-01

    The attenuation of TeV γ-rays from distant blazars by the extragalactic background light (EBL) produces relativistic electron-positron pair beams. It has been shown by Broderick et. al. (2012) and Schlickeiser et. al (2012) that a pair beam traversing the intergalactic medium is unstable to linear two-stream instabilities of both electrostatic and electromagnetic nature. While for strong blazars all free pair energy is dissipated in heating the intergalactic medium and a potential electromagnetic cascade via inverse-Compton scattering with the cosmic microwave background is suppressed, we investigate the case of weak blazars where the back reaction of generated electrostatic turbulence leads to a plateauing of the electron energy spectrum. In the ultra-relativistic Thomson limit we analytically calculate the inverse-Compton spectral energy distribution for both an unplateaued and a plateaued beam scenario, showing a peak reduction factor of Rpeak ≈ 0.345. This is consistent with the FERMI non-measurements of a GeV excess in the spectrum of EBL attenuated TeV blazars. Claims on the lower bound of the intergalactic magnetic field strengths, made by several authors neglecting plasma effects, are thus put into question.

  18. Blazars S5 0716+71 and B3 1633+38 in unprecedented outbursts

    NASA Astrophysics Data System (ADS)

    Arkharov, A. A.; Borman, G. A.; Di Paola, A.; Larionov, V. M.; Morozova, D. A.

    2015-01-01

    We perform optical and near-infrared monitoring of selected gamma-bright blazars using 40-cm LX-200 (optical, St.Petersburg, Russia), 70-cm AZT-8 (optical, Crimea) and 1.1-m AZT-24 (near-infrared, Campo Imperatore, Italy), as a part of WEBT/GASP project.

  19. Infrared properties of blazars: putting the GASP-WEBT sources into context

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Villata, M.; Carnerero, M. I.; Acosta-Pulido, J. A.; Larionov, V. M.; D'Ammando, F.; Arévalo, M. J.; Arkharov, A. A.; Bueno Bueno, A.; Di Paola, A.; Efimova, N. V.; González-Morales, P. A.; Gorshanov, D. L.; Grinon-Marin, A. B.; Lázaro, C.; Manilla-Robles, A.; Pastor Yabar, A.; Puerto Giménez, I.; Velasco, S.

    2014-07-01

    The infrared properties of blazars can be studied from the statistical point of view with the help of sky surveys, like that provided by the Wide-field Infrared Survey Explorer and the Two Micron All Sky Survey. However, these sources are known for their strong and unpredictable variability, which can be monitored for a handful of objects only. In this paper, we consider the 28 blazars (14 BL Lac objects and 14 flat-spectrum radio quasars, FSRQs) that are regularly monitored by the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope since 2007. They show a variety of infrared colours, redshifts, and infrared-optical spectral energy distributions (SEDs), and thus represent an interesting mini-sample of bright blazars that can be investigated in more detail. We present near-IR light curves and colours obtained by the GASP from 2007 to 2013, and discuss the infrared-optical SEDs. These are analysed with the aim of understanding the interplay among different emission components. BL Lac SEDs are accounted for by synchrotron emission plus an important contribution from the host galaxy in the closest objects, and dust signatures in 3C 66A and Mrk 421. FSRQ SEDs require synchrotron emission with the addition of a quasar-like contribution, which includes radiation from a generally bright accretion disc (νLν up to ˜4 × 1046 erg s-1), broad-line region, and a relatively weak dust torus.

  20. Optical polarization plane rotation for the blazar PG 1553+113

    NASA Astrophysics Data System (ADS)

    Blinov, D.; Casadi, C.

    2016-09-01

    We report about RoboPol observations of the ongoing rotation of the optical polarization angle for the blazar PG 1553+113 (RA=15h55m43s; Dec=+11d11m24s). The rotation began around August, 19. So far the total amplitude of the rotation is ~130 degrees with an average rate of ~8 deg/day.

  1. Rotation of the optical polarization plane for the blazar 4C +38.41

    NASA Astrophysics Data System (ADS)

    Panopoulou, G. V.; Maragkakis, G. M.; Xexakis, K.

    2016-08-01

    We report on the ongoing rotation of the optical polarization angle (R-band) seen in the monitored blazar 4C +38.41 (RA=16:35:15.5, DEC=38:08:05, J2000) as recorded within the framework of the RoboPol program.

  2. VERY RAPID HIGH-AMPLITUDE GAMMA-RAY VARIABILITY IN LUMINOUS BLAZAR PKS 1510-089 STUDIED WITH FERMI-LAT

    SciTech Connect

    Saito, S.; Stawarz, L.; Takahashi, T.; Tanaka, Y. T.; Madejski, G.; D'Ammando, F.

    2013-03-20

    Here we report on the detailed analysis of the {gamma}-ray light curve of a luminous blazar PKS 1510-089 observed in the GeV range with the Large Area Telescope (LAT) on board the Fermi satellite during the period 2011 September-December. By investigating the properties of the detected three major flares with the shortest possible time binning allowed by the photon statistics, we find a variety of temporal characteristics and variability patterns. This includes a clearly asymmetric profile (with a faster flux rise and a slower decay) of the flare resolved on sub-daily timescales, a superposition of many short uncorrelated flaring events forming the apparently coherent longer-duration outburst, and a huge single isolated outburst unresolved down to the timescale of 3 hr. In the latter case we estimate the corresponding {gamma}-ray flux doubling timescale to be below 1 hr, which is extreme and never previously reported for any active galaxy in the GeV range. The other unique finding is that the total power released during the studied rapid and high-amplitude flares constitutes the bulk of the power radiatively dissipated in the source and a significant fraction of the total kinetic luminosity of the underlying relativistic outflow. Our analysis allows us to access directly the characteristic timescales involved in shaping the energy dissipation processes in the source, and to provide constraints on the location and the structure of the blazar emission zone in PKS 1510-089.

  3. Probing the Disk-Jet Connection in Fermi Gamma-Ray Bright Blazars

    NASA Astrophysics Data System (ADS)

    Isler, Jedidah; Urry, C. M.; Coppi, P. S.; Bailyn, C. D.; Chatterjee, R.; Fossati, G.; Bonning, E. W.; Maraschi, L.; Buxton, M.; SMARTS

    2014-01-01

    Relativistic jets in blazars produce radio through gamma-ray emission, via synchrotron radiation at long wavelengths and inverse Compton scattering at gamma-ray energies. Variability across these wavelengths allows us to estimate the densities and energies of the radiating particles. Yet, the physics of blazar jets is still uncertain; e.g., it is not clear whether the gamma-rays come from sub- or kilo-parsec scales. The unprecedented temporal and spectral sensitivity of the Fermi Space Telescope has ushered in a new era of discovery and over the past 5 years I have obtained queue-scheduled, nightly optical-infrared (OIR) photometry and bi-weekly optical spectroscopy using the Small and Medium Aperture Research Telescope System (SMARTS) 1.3m+Andicam and 1.5m+RCSpec, in Cerro Tololo, Chile; totaling ~70 gamma-ray bright blazars that are detected nightly with Fermi. In my dissertation, I analyze 5 years of bi-monthly spectroscopy of 6 blazars. I find that the broad lines - which are presumably photoionized by the accretion disk - vary substantially less than the OIR continuum, which is dominated by the Doppler-beamed jet. However, during the largest gamma-ray flares in 3C 454.3 and PKS 1510-089, I see significant broad emission line variations, with lags on the order days and infer that the jet, in its brightest state, contributes significantly to photoionizing the broad-line clouds, meaning the gamma-emitting region is within the broad line region at sub-parsec scales. These variations are not seen at lower gamma-ray fluxes or in any other blazars we observed. I also describe inferences about the jet physics obtained from the SMARTS OIR photometry, which is well correlated with the gamma-ray flux for 11 blazars, with lags of less than one day, strongly supporting the inverse Compton model for gamma-ray production. In addition, color changes in the OIR constrain the ratio of thermal disk to non-thermal jet emission. The color evolution differs by source and also in a

  4. Simultaneous Planck, Swift, and Fermi Observations of X-ray and Gamma-ray Selected Blazars

    NASA Technical Reports Server (NTRS)

    Giommi, P.; Polenta, G.; Laehteenmaeki, A.; Thompson, D. J.; Capalbi, M.; Cutini, S.; Gasparrini, D.; Gonzalez, Nuevo, J.; Leon-Tavares, J.; Lopez-Caniego, M.; Mazziotta, M. N.; Monte, C.; Perri, M.; Raino, S.; Tosti, G.; Tramacere, A.; Verracchia, F.; Aller, H. D.; Aller, MF.; Angelakis, E.; Bastieri, D.; Berdyugin, A.; Bonaldi, A.; Bonavera, L.; Lawrence, C. R.

    2012-01-01

    We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and gamma-ray bands, with additional 5 GHz flux-density limits to ensure a good probability of a Planck detection. We compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set allows us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by the Fermi Large Area Telescope (LAT), whereas 30% to 40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma-ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-millimetre spectral slope of blazars is quite flat, with (alpha) approx 0 up to about 70GHz, above which it steepens to (alpha) approx -0.65. The BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (nu(sup s)(sub peak)) in the spectral energy distribution (SED) of FSRQs is the same in all the blazar samples with (nu(sup s)(sub peak)) = 10(exp 13.1 +/- 0.1) Hz, while the mean inverse Compton peak frequency, (nu(sup IC)(sub peak)), ranges from 10(exp 21) to 10(exp 22) Hz. The distributions of nu(sup s)(sub peak) and nu(sup IC)(sub peak) of BL Lacs are much broader and are shifted to higher energies than those of FSRQs; their shapes strongly depend on the selection method. The Compton dominance of blazars. defined as the ratio of the inverse Compton to synchrotron peak luminosities, ranges from less than 0.2 to nearly 100, with only FSRQs reaching values larger than about 3. Its distribution is broad and depends

  5. Simultaneous Planck, Swift, and Fermi Observations of X-Ray and gamma-Ray Selected Blazars

    NASA Technical Reports Server (NTRS)

    Giommi, P.; Polenta, G.; Laehteenmaeki, A.; Thompson, D. J.; Capalbi, M.; Cutini, S.; Gasparrini, D.; Gonzalez-Nuevo, J.; Leon-Tavares, J.; Lopez-Caniego, M.; Mazziotta, M. N.; Monte, C.; Perri, M.; Raino, S.; Tosti, G.; Tramacere, A.; Verrecchia, F.; Aller, H. D.; Aller, M. F.; Angelakis, E.; Bastieri, D.; Berdyugin, A.; Bonaldi, A.; Bonavera, L.; Burigana, C.

    2011-01-01

    We present simultaneous Planck, Swift, Fermi, and ground-based data for 105 blazars belonging to three samples with flux limits in the soft X-ray, hard X-ray, and -ray bands, and we compare our results to those of a companion paper presenting simultaneous Planck and multi-frequency observations of 104 radio-loud northern active galactic nuclei selected at radio frequencies. While we confirm several previous results, our unique data set has allowed us to demonstrate that the selection method strongly influences the results, producing biases that cannot be ignored. Almost all the BL Lac objects have been detected by Fermi Large Area Telescope (LAT), whereas 30 to 40% of the flat-spectrum radio quasars (FSRQs) in the radio, soft X-ray, and hard X-ray selected samples are still below the gamma ray detection limit even after integrating 27 months of Fermi-LAT data. The radio to sub-millimetre spectral slope of blazars is quite flat, with [alpha] approximately 0 up to about 70 GHz, above which it steepens to [alpha] approximately -0.65. BL Lacs have significantly flatter spectra than FSRQs at higher frequencies. The distribution of the rest-frame synchrotron peak frequency (v(sup IC) (sub (PEAK)), ranges from 10(sup 21) to 10(sup 22) HZ. The distribution of the rest-frame synchrotron peak frequency (v(sup s)(sub peak)) in the spectral energy distribution (SED) of FSRQs is the same in all the blazar samples with (v(sup s)(sub peak) = 10(sup 13:1 plus or minus 0.1) Hz, while the mean inverse-Compton peak frequency,(v(sup IC)(sub peak) ranges from 10(sup 21) to 10(sup 22) Hz. The distributions of v(sup S)(sub peak) and of v(sup IC)(sub peak) of BL Lacs are much broader and are shifted to higher energies than those of FSRQs; their shapes strongly depend on the selection method. The Compton dominance of blazars ranges from less than 0.2 to nearly 100, with only FSRQs reaching values larger than about 3. Its distribution is broad and depends strongly on the selection method

  6. Optical spectroscopic observations of γ-ray blazar candidates. I. Preliminary results

    SciTech Connect

    Paggi, A.; Milisavljevic, D.; D'Abrusco, R.; Smith, H. A.; Margutti, R.; Martínez-Galarza, J. R.; Landoni, M.; Grindlay, J. E.; Masetti, N.; Giroletti, M.; Jiménez-Bailón, E.; Otí-Floranes, H.; Chavushyan, V.; Massaro, F.; Funk, S.; Tosti, G.

    2014-05-01

    A significant fraction (∼30%) of the γ-ray sources listed in the second Fermi/LAT (2FGL) catalog is still of unknown origin, being not yet associated with counterparts at lower energies. Using the available information at lower energies and optical spectroscopy on the selected counterparts of these γ-ray objects, we can pinpoint their exact nature. Here, we present a pilot project pointing to assess the effectiveness of the several classification methods developed to select γ-ray blazar candidates. To this end, we report optical spectroscopic observations of a sample of five γ-ray blazar candidates selected on the basis of their infrared Wide-field Infrared Survey Explorer (WISE) colors or of their low-frequency radio properties. Blazars come in two main classes, BL Lac objects and FSRQs, showing similar optical spectra except for the stronger emission lines of the latter. For three of our sources, the almost featureless optical spectra obtained confirm their BL Lac nature, while for the source WISEJ022051.24+250927.6 we observe emission lines with equivalent width EW ∼ 31 Å, identifying it as a FSRQ with z = 0.48. The source WISEJ064459.38+603131.7, although not featuring a clear radio counterpart, shows a blazar-like spectrum with weak emission lines with EW ∼ 7 Å, yielding a redshift estimate of z = 0.36. In addition, we report optical spectroscopic observations of four WISE sources associated with known γ-ray blazars without a firm classification or redshift estimate. For the latter sources, we confirm a BL Lac classification, with a tentative redshift estimate for the source WISEJ100800.81+062121.2 of z = 0.65.

  7. The core shift effect in the blazar 3C 454.3

    NASA Astrophysics Data System (ADS)

    Kutkin, A. M.; Sokolovsky, K. V.; Lisakov, M. M.; Kovalev, Y. Y.; Savolainen, T.; Voytsik, P. A.; Lobanov, A. P.; Aller, H. D.; Aller, M. F.; Lahteenmaki, A.; Tornikoski, M.; Volvach, A. E.; Volvach, L. N.

    2014-02-01

    Opacity-driven shifts of the apparent very long baseline interferometry (VLBI) core position with frequency (the `core shift' effect) probe physical conditions in the innermost parts of jets in active galactic nuclei. We present the first detailed investigation of this effect in the brightest γ-ray blazar 3C 454.3 using direct measurements from simultaneous 4.6-43 GHz very long baseline array observations, and a time lag analysis of 4.8-37 GHz light curves from the University of Michigan Radio Observatory, Crimean Astrophysical Observatory and Metsähovi observations in 2007-2009. The results support the standard Königl model of jet physics in the VLBI core region. The distance of the core from the jet origin rc(ν), the core size W(ν) and the light curve time lag ΔT(ν) all depend on the observing frequency ν as rc(ν) ∝ W(ν) ∝ ΔT(ν) ∝ ν-1/k. The obtained range of k = 0.6-0.8 is consistent with the synchrotron self-absorption being the dominating opacity mechanism in the jet. The similar frequency dependence of rc(ν) and W(ν) suggests that the external pressure gradient does not dictate the jet geometry in the cm-band core region. Assuming equipartition, the magnetic field strength scales with distance r as B = 0.4(r/1 pc)-0.8 G. The total kinetic power of electron/positron jet is about 1044 ergs s-1.

  8. Calculation of equilibrium constants from multiwavelength spectroscopic data-I Mathematical considerations.

    PubMed

    Gampp, H; Maeder, M; Meyer, C J; Zuberbühler, A D

    1985-02-01

    Multiwavelength spectrophotometric and spectroscopic data in general contain considerably more information about complexation equilibria than potentiometric data do. With the construction of a fully automatic titration set-up built into a high-precision spectrophotometer, the problems related to the wider use of this method have shifted from the quality of the primary data to the complexity of their numerical treatment. Matrix algebra is used to show how these problems can be overcome. An algorithm is described for calculation of stability constants and absorption spectra, together with the associated standard errors, at a reasonable expense of computer time. Problems in finding the minimum in a multidimensional parameter space are reduced by elimination of the molar absorptivities from the algorithm for the iterative refinement. Numerical safety and speed of calculation are improved by use of analytical instead of numerical derivatives. The number of data to be fitted is decreased by principal-component analysis. PMID:18963802

  9. Development of SAC-OCDMA in FSO with multi-wavelength laser source

    NASA Astrophysics Data System (ADS)

    Moghaddasi, Majid; Mamdoohi, Ghazaleh; Muhammad Noor, Ahmad Shukri; Mahdi, Mohd Adzir; Ahmad Anas, Siti Barirah

    2015-12-01

    We propose and demonstrate a free space optical network, based on spectral amplitude coding optical code division multiple access (SAC-OCDMA) with a multi-wavelength laser source. A detailed theoretical analysis that represents the characteristics of SAC-OCDMA system was developed. In addition to the impact of turbulence, influences of several system noises such as optical beat interference (OBI), relative intensity noise, and receiver noises, have been studied. From the numerical results, it was found that the influence of OBI is more dominant, especially at higher received power. Two different codes, namely, modified quadratic congruence and modified double weight, are then compared with the latter which provides better performance. A transmission distance of 2.6 km with 10 users and an 8 cm aperture diameter is advisable whenever the turbulence is moderate. These results can be improved when a beam divergence smaller than 1 mrad is utilized.

  10. Microwave photonic filter using multiwavelength Brillouin-erbium fiber laser with double-Brillouin-frequency shift

    NASA Astrophysics Data System (ADS)

    Loh, K. K.; Yeo, K. S.; Shee, Y. G.

    2015-04-01

    A microwave photonic filter based on double-Brillouin-frequency spaced multiwavelength Brillouin-erbium fiber laser (BEFL) is experimentally demonstrated. The filter selectivity can be easily adjusted by tuning and apodizing the optical taps generated from the multiwavelength BEFL. Reconfiguration of different frequency responses are demonstrated.

  11. Microwave photonic filter using multiwavelength Brillouin-erbium fiber laser with double-Brillouin-frequency shift

    SciTech Connect

    Loh, K. K.; Yeo, K. S.; Shee, Y. G.

    2015-04-24

    A microwave photonic filter based on double-Brillouin-frequency spaced multiwavelength Brillouin-erbium fiber laser (BEFL) is experimentally demonstrated. The filter selectivity can be easily adjusted by tuning and apodizing the optical taps generated from the multiwavelength BEFL. Reconfiguration of different frequency responses are demonstrated.

  12. A simplified view of blazars: contribution to the X-ray and γ-ray extragalactic backgrounds

    NASA Astrophysics Data System (ADS)

    Giommi, P.; Padovani, P.

    2015-07-01

    The blazar-simplified view is a new paradigm that explains well the diverse statistical properties of blazars observed over the entire electromagnetic spectrum on the basis of minimal assumptions on blazars' physical and geometrical properties. In this paper, the fourth in a series, we extend the predictions of this paradigm below the sensitivity of existing surveys and estimate the contribution of blazars to the X-ray and γ-ray extragalactic backgrounds. We find that the integrated light from blazars can explain up to 100 per cent of the cosmic background at energies larger than ˜10 GeV, and contribute ≈40-70 per cent of the γ-ray diffuse radiation between 100 MeV and 10 GeV. The contribution of blazars to the X-ray background, between 1 and 50 keV, is approximately constant and of the order of 4-5 per cent. On the basis of an interpolation between the estimated flux at X-ray and γ-ray energies, we can expect that the contribution of blazars raises to ˜10 per cent at 100 keV, and continues to increase with energy until it becomes the dominant component at a few MeV. Finally, we show that a strong dependence of the synchrotron peak frequency on luminosity, as postulated by the blazar sequence, is ruled out by the observational data as it predicts a γ-ray background above a few GeV that is far in excess of the observed value.

  13. Flux and spectral variability of the blazar PKS 2155 -304 with XMM-Newton: Evidence of particle acceleration and synchrotron cooling

    NASA Astrophysics Data System (ADS)

    Bhagwan, Jai; Gupta, A. C.; Papadakis, I. E.; Wiita, Paul J.

    2016-04-01

    We have analyzed XMM-Newton observations of the high energy peaked blazar, PKS 2155 -304, made on 24 May 2002 in the 0.3-10 keV X-ray band. These observations display a mini-flare, a nearly constant flux period and a strong flux increase. We performed a time-resolved spectral study of the data, by dividing the data into eight segments. We fitted the data with a power-law and a broken power-law model, and in some of the segments we found a noticeable spectral flattening of the source's spectrum below 10 keV. We also performed "time-resolved" cross-correlation analyses and detected significant hard and soft lags (for the first time in a single observation of this source) during the first and last parts of the observation, respectively. Our analysis of the spectra, the variations of photon-index with flux as well as the correlation and lags between the harder and softer X-ray bands indicate that both the particle acceleration and synchrotron cooling processes make an important contribution to the emission from this blazar. The hard lags indicate a variable acceleration process. We also estimated the magnetic field value using the soft lags. The value of the magnetic field is consistent with the values derived from the broad-band SED modeling of this source.

  14. Exploring Blazar Jet Dynamics with Optical and Gamma Ray Cross-Correlations Using the Fermi Gamma Ray Space Telescope Public Data

    NASA Astrophysics Data System (ADS)

    Cook, Kyle; Carini, M. T.

    2010-01-01

    For the past 9 years Western Kentucky University has been monitoring approximately 50 Blazar sources at the R-band optical wavelengths. The Fermi Gamma Ray Space Telescope provides a source of gamma-ray data publicly available for cross correlation analysis, and the recent release of the data has made this possible. Such an analysis will prove useful in understanding the processes present in the jets producing the observed emission in these AGN. This type of analysis is being conducted at Western Kentucky University, pulling together the optical data from the WKU telescope network as well as other public databases and comparing them to the released FGST data. Here we present the initial results from the cross-correlation analysis and apply it to sources of interest. This research is funded by the NASA Kentucky Space Grant Consortium.

  15. Development, characterization, and application of the DRI model 2015 multiwavelength thermal-optical carbon analyzer

    NASA Astrophysics Data System (ADS)

    Sumlin, Benjamin J.

    A multiwavelength thermal/optical carbon analyzer (DRI Model 2015) equipped with a novel seven-wavelength light source (405, 445, 532, 635, 780, 808, and 980 nm) was developed to analyze chemical and optical properties of carbonaceous particles collected on quartz-fiber filters. Built upon on the DRI Model 2001 carbon analyzer at 633 nm, major modifications were made to mechanical and electrical components, flow control, and the carbon detector to adopt modern technologies, increase instrument reliability, and reduce costs and maintenance. This instrument quantifies organic and elemental carbon (OC and EC, respectively) and their thermal fractions. It also allows estimation of the amount of brown and black carbon (BrC and BC, respectively) on filters. Continuous monitoring of the light reflected from and transmitted through the filter along with carbon evolved from the filter when heated to different temperatures under either inert or oxidizing gas environments provides insights into the optical properties of the carbon released from the filter; it also allows examination of the charring process as pyrolyzed char has been one of the major uncertainties in quantifying OC and EC. The objectives of this study are: 1) characterize the Model 2015's performance parameters including detection limits, and optical behavior; 2) establish performance equivalence between the Model 2015 and Model 2001 DRI carbon analyzers when comparing similar laser wavelength to maintain consistency for long-term network sample analysis; and 3) conduct a preliminary analysis of the multiwavelength signal to estimate BrC and BC, and to optimize char correction. A selection of samples, including standard chemicals, as well as rural and urban ambient filter samples were measured by both the Model 2015 and Model 2001 analyzers. The design and construction experience will be discussed, as well as recommended future scientific research and engineering development.

  16. Algebraic solution for phase unwrapping problems in multiwavelength interferometry.

    PubMed

    Falaggis, Konstantinos; Towers, David P; Towers, Catherine E

    2014-06-10

    Recent advances in multiwavelength interferometry techniques [Appl. Opt.52, 5758 (2013)] give new insights to phase unwrapping problems and allow the fringe order information contained in the measured phase to be extracted with low computational effort. This work introduces an algebraic solution to the phase unwrapping problem that allows the direct calculation of the unknown integer fringe order. The procedure resembles beat-wavelength approaches, but provides greater flexibility in choosing the measurement wavelengths, a larger measurement range, and a higher robustness against noise, due to the ability to correct for errors during the calculation. PMID:24921139

  17. Nonlinear optical signal processing on multiwavelength sensitive materials.

    PubMed

    Azimipour, Mehdi; Pashaie, Ramin

    2013-11-01

    Exploiting salient features in the photodynamics of specific types of light sensitive materials, a new approach is presented for realization of parallel nonlinear operations with optics. We briefly review the quantum structure and mathematical models offered for the photodynamics of two multiwavelength sensitive materials, doped crystals of lithium niobate and thick layers of bacteriorhodopsin. Next, a special mode of these dynamics in each material is investigated and a graphical design procedure is offered to produce highly nonlinear optical responses that can be dynamically reshaped via applying minimum changes in the optical setup. PMID:24177084

  18. Development of the multiwavelength monolithic integrated fiber optics terminal

    NASA Technical Reports Server (NTRS)

    Chubb, C. R.; Bryan, D. A.; Powers, J. K.; Rice, R. R.; Nettle, V. H.; Dalke, E. A.; Reed, W. R.

    1982-01-01

    This paper describes the development of the Multiwavelength Monolithic Integrated Fiber Optic Terminal (MMIFOT) for the NASA Johnson Space Center. The program objective is to utilize guided wave optical technology to develop wavelength-multiplexing and -demultiplexing units, using a single mode optical fiber for transmission between terminals. Intensity modulated injection laser diodes, chirped diffraction gratings and thin film lenses are used to achieve the wavelength-multiplexing and -demultiplexing. The video and audio data transmission test of an integrated optical unit with a Luneburg collimation lens, waveguide diffraction grating and step index condensing lens is described.

  19. Multiwavelength spectrophotometric determination of acidity constants of some azo dyes.

    PubMed

    Shamsipur, Mojtaba; Maddah, Bozorgmehr; Hemmateenejad, Bahram; Rouhani, Shohreh; Haghbeen, Kamaladin; Alizadeh, Kamal

    2008-06-01

    A multiwavelength spectrophotometric titration method was applied to study the acidity constants of some azo dyes in water. The UV-vis absorption spectra of azo dye solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components have been calculated. The quantitative effects of the substituents on the acidity of the studied azo dyes were investigated by the linear free energy relationship (LFER) using Hammet sigma constant (sigma) and field and resonance effects of Kamlet and Taft (f and Re, respectively). PMID:17719268

  20. Multiwavelength spectrophotometric determination of acidity constants of some azo dyes

    NASA Astrophysics Data System (ADS)

    Shamsipur, Mojtaba; Maddah, Bozorgmehr; Hemmateenejad, Bahram; Rouhani, Shohreh; Haghbeen, Kamaladin; Alizadeh, Kamal

    2008-06-01

    A multiwavelength spectrophotometric titration method was applied to study the acidity constants of some azo dyes in water. The UV-vis absorption spectra of azo dye solutions were recorded in the course of their pH-metric titration with a standard base solution. The protolytic equilibrium constants, spectral profiles, concentration diagrams and also the number of components have been calculated. The quantitative effects of the substituents on the acidity of the studied azo dyes were investigated by the linear free energy relationship (LFER) using Hammet sigma constant ( σ) and field and resonance effects of Kamlet and Taft ( f and ℜ, respectively).

  1. Molecular transport network security using multi-wavelength optical spins.

    PubMed

    Tunsiri, Surachai; Thammawongsa, Nopparat; Mitatha, Somsak; Yupapin, Preecha P

    2016-01-01

    Multi-wavelength generation system using an optical spin within the modified add-drop optical filter known as a PANDA ring resonator for molecular transport network security is proposed. By using the dark-bright soliton pair control, the optical capsules can be constructed and applied to securely transport the trapped molecules within the network. The advantage is that the dark and bright soliton pair (components) can securely propagate for long distance without electromagnetic interference. In operation, the optical intensity from PANDA ring resonator is fed into gold nano-antenna, where the surface plasmon oscillation between soliton pair and metallic waveguide is established. PMID:25058032

  2. Multiwavelength Constraints on the Dynamical History of Omega Centauri

    NASA Astrophysics Data System (ADS)

    Haggard, Daryl; Cool, A. M.; Arias, T.; Brochmann, M. B.; Dorfman, J.; Gafford, A.; White, V.; Anderson, J.; Davies, M. B.

    2012-09-01

    Omega Centauri, the Milky Way's most massive and enigmatic old stellar cluster, offers a treasure trove of astronomical discovery and controversy. Is the cluster a globular or a dwarf galaxy remnant? Does it host a massive central black hole? What are the origins and dynamical histories of the cluster's multiple stellar populations? I will discuss our multiwavelength imaging and spectroscopic campaigns, and in particular a new Chandra X-ray flux limit on the cluster's purported IMBH. These observations also probe Omega Cen's binary populations and shed light on the cluster's dynamical history.

  3. Monitoring the dissolution rate of photoresist thin films via multiwavelength interferometry

    NASA Astrophysics Data System (ADS)

    Agrawal, Ankur; Henderson, Clifford L.

    2003-05-01

    Dissolution rate monitors (DRMs) and related techniques have been used for a number of years to study the dissolution behavior of photoresist materials in detail. Due to the relative difficulty in obtaining commercial DRM instruments, crude methods for measuring dissolution rates such as the (formula availble in paper) have been developed. In this method, the resist-coated substrate is immersed in a developer solution for a fixed development time, removed and dried, and the remaining film thickness is measured. The dissolution rate information for the resist is then calculated from the slope of the resist thickness versus development time data. This method is simple and can easily be used in a fab environment, but it suffers from a number of limitations. For example, this method is very inaccurate for resists that develop very quickly (< 20 seconds) such as many modern chemically amplified resists. Such quick development times are often crucial in exploring the full behavior of a resist. A much better method for measuring the dissolution behavior of photoresist films is to use interferometric methods such as those suggested originally by Dill and coworkers. In this work, an extremely flexible and simple instrument based on inexpensive, commercially available, PC card spectrometers will be presented that can be used quite robustly in both fab and laboratory environments for measuring the dissolution behavior of photoresist films. The hardware required in order to construct such a simple apparatus will be discussed along with various experimental configurations that are appropriate for different measurement tasks. Thin film thickness estimation using the DRM can be done using either single wavelength versus time interferometry data (plot of reflected light intensity versus development time) or the complete multiwavelength spectra obtained from a spectroscopic reflectometry system. Film thickness estimation using single wavelength data analysis is good for films that

  4. Multiwavelength FLIM: new applications and algorithms

    NASA Astrophysics Data System (ADS)

    Rück, A.; Strat, D.; Dolp, F.; von Einem, B.; von Arnim, C. A. F.

    2011-03-01

    The combination of time-resolved and spectral resolved techniques as achieved by SLIM (spectrally resolved fluorescence lifetime imaging) improves the analysis of complex situations, when different fluorophores have to be distinguished. This could be the case when endogenous fluorophores of living cells and tissues are observed to identify the redox state and oxidative metabolic changes of the mitochondria. Other examples are FRET (resonant energy transfer) measurements, when different donor/acceptor pairs are observed simultaneously. SLIM is working in the time domain employing excitation with short light pulses and detection of the fluorescence intensity decay in many cases with time-correlated single photon counting (TCSPC). Spectral resolved detection is achieved by a polychromator in the detection path and a 16-channel multianode photomultiplier tube with the appropriate routing electronics. Within this paper special attention will be focused on FRET measurements with respect to protein interactions in Alzheimers disease. Using global analysis as the phasor plot approach or integration of the kinetic equations taking into account the multidimensional datasets in every spectral channel we could demonstrate considerable improvement of our calculations.

  5. Study Case of Air-Mass Modification over Poland and Romania Observed by the Means of Multiwavelength Raman Depolarization Lidars

    NASA Astrophysics Data System (ADS)

    Costa-Surós, Montserrat; Janicka, Lucja; Stachlewska, Iwona S.; Nemuc, Anca; Talianu, Camelia; Heese, Birgit; Engelmann, Ronny

    2016-06-01

    An air-mass modification, on its way from Poland to Romania, observed between 19-21 July 2014 is discussed. The air-mass was investigated using data of two multi-wavelength lidars capable of performing regular elastic, depolarization and Raman measurements in Warsaw, Poland, and in Magurele, Romania. The analysis was focused on evaluating optical properties of aerosol in order to search for similarities and differences in the vertical profiles describing the atmospheric layers above the two stations within given period.

  6. 1WHSP: An IR-based sample of ~1000 VHE γ-ray blazar candidates

    NASA Astrophysics Data System (ADS)

    Arsioli, B.; Fraga, B.; Giommi, P.; Padovani, P.; Marrese, P. M.

    2015-07-01

    Context. Blazars are the dominant type of extragalactic sources at microwave and at γ-ray energies. In the most energetic part of the electromagnetic spectrum (E ≳ 100 GeV) a high fraction of high Galactic latitude sources are blazars of the high synchrotron peaked (HSP) type, that is BL Lac objects with synchrotron power peaking in the UV or in the X-ray band. Building new large samples of HSP blazars is key to understand the properties of jets under extreme conditions, and to study the demographics and the peculiar cosmological evolution of these sources. Aims: High synchrotron peaked blazars are remarkably rare, with only a few hundreds of them expected to be above the sensitivity limits of currently available surveys, some of which include hundreds of millions of sources. To find these very uncommon objects, we have devised a method that combines ALLWISE survey data with multi-frequency selection criteria. Methods: The sample was defined starting from a primary list of infrared colour-colour selected sources from the ALLWISE all sky survey database, and applying further restrictions on IR-radio and IR-X-ray flux ratios. Using a polynomial fit to the multi-frequency data (radio to X-ray), we estimated synchrotron peak frequencies and fluxes of each object. Results: We assembled a sample including 992 sources, which is currently the largest existing list of confirmed and candidates HSP blazars. All objects are expected to radiate up to the highest γ-ray photon energies. In fact, 299 of these are confirmed emitters of GeV γ-ray photons (based on Fermi-LAT catalogues), and 36 have already been detected in the TeV band. The majority of sources in the sample are within reach of the upcoming Cherenkov Telescope Array (CTA), and many may be detectable even by the current generation of Cherenkov telescopes during flaring episodes. The sample includes 425 previously known blazars, 151 new identifications, and 416 HSP candidates (mostly faint sources) for which no

  7. Multiwavelength FLIM: new concept for fluorescence diagnosis

    NASA Astrophysics Data System (ADS)

    Rück, Angelika; Lorenz, S.; Hauser, Carmen; Mosch, S.; Kalinina, S.

    2012-03-01

    Fluorescence guided tumor resection is very well accepted in the case of bladder cancer and brain tumor, respectively. However, false positive results are one of the major problems, which will make the discrimination between tumor tissue and inflammation difficult. In contrast fluorescence lifetime imaging (FLIM) and especially spectral resolved FLIM (SLIM) can significantly improve the analysis. The fluorescence decay of a fluorophore in many cases does not show a simple monoexponential profile. A very complex situation arises, when more than one compound has to be analyzed. This could be the case when endogenous fluorophores of living cells and tissues have to be discriminated to identify oxidative metabolic changes. Other examples are PDT, when different photosensitizer metabolites are observed simultaneously. In those cases a considerable improvement could be achieved when time-resolved and spectral-resolved techniques are simultaneously incorporated. Within this presentation the principles of spectral and time-resolved fluorescence imaging will be discussed. Successful applications as autofluorescence and 5-ALA induced porphyrin fluorescence will be described in more detail.

  8. 40nm tunable multi-wavelength fiber laser

    NASA Astrophysics Data System (ADS)

    Jia, Qingsong; Wang, Tianshu; Zhang, Peng; Dong, Keyan; Jiang, Huilin

    2014-12-01

    A Brillouin-Erbium multi-wavelength tunable fiber laser at C-band is demostrated. A 10 km long singlemode fiber(SMF), a 6 m long Erbium-doped fiber, two couplers, a wavelength division multiplexer, a isolator, an optical circulator, a 980nm pump laser and a narrow linewidth tunable laser are included in the structure. A segment of 10 km-long single-mode fiber (SMF) between the two ports of a 1×2 coupler is used as Brillouin gain. Ebiumdoped fiber amplifier (EDFA) consists of a segment of 6m er-doped fiber pumped by 980nm laser dioder . A narrow linewidth tunable laser from 1527 to 1607 nm as Brillouin bump, At the Brillouin pump power of 8mW and the 980 nm pump power of 400 mw, 16 output channels with 0.08 nm spacing and tuning range of 40 nm from 1527 nm to 1567 nm are achieved. We realize the tunable output of wavelength by adjusting the 980 nm pump power and the Brillouin pump wavelength. Stability of the multiwavelength fiber laser is also observed.

  9. Jet evolution in Steep Spectrum Radio Quasars: a multiwavelength study

    NASA Astrophysics Data System (ADS)

    Torresi, Eleonora; Grandi, Paola

    2013-12-01

    Thanks to the Fermi γ-ray satellite, it is now confirmed that Misaligned Active Galactic Nuclei (MAGN), i.e. radio galaxies and steep spectrum radio quasars, are a new class of GeV emitters. In this work we present the first γ-ray and multiwavelength study of the two steep spectrum radio quasars, i.e. 3C 207 and 3C 380, belonging to the MAGN sample. From the γ -ray variability study we estimate the physical size of the zone where high-energy photons are dissipated: for both sources this region should be very compact, not larger than 0.05 pc. As a successive step, we build multiwavelength light curves of 3C 207 and 3C 380 to search for possible simultaneous outbursts in different wavebands with the aim of localizing the compact emitting region. This is an important issue with strong impact on theoretical models: indeed, knowing where highenergy photons are dissipated (at sub-pc or pc-scale) provides information on the nature of the seed photons involved in the production of the GeV radiation.

  10. Multi-wavelength coverage of outburst decays of LMXBs

    NASA Astrophysics Data System (ADS)

    Kalemci, Emrah; Tomsick, John; Bailyn, Charles; Dincer, Tolga

    2016-07-01

    Low mass X-ray binaries (LMXB) are dynamic laboratories that are powered by accretion, and under some conditions these systems create strong outflows in the form of highly collimated jets, or winds. Outburst decays of transient LMXBs provide additional information about compact jets and their relation to changes in timing properties. Our group characterizes the multi-wavelength evolution of Galactic black hole transients during their outburst decays using simultaneous X-ray (RXTE, Swift, and INTEGRAL), optical/infrared (SMARTS) and radio (VLA, ATCA, VLBI). By characterizing the X-ray spectral and timing evolution of these systems, and merging this information with the evolution in the near-infrared and radio, we obtain the conditions necessary to launch stable compact jets, and discuss how jets can be influencing and/or influenced by X-ray timing and spectral properties of these systems. In this presentation, I will summarize recent results regarding multi-wavelength observations of not only black hole systems, but also neutron star X-ray binaries during outburst decays, and discuss models that explain not only the broad spectral energy distribution, but also some of the timing properties of these systems.

  11. Emissivity measurements of shocked tin using a multi-wavelength integrating sphere

    SciTech Connect

    Seifter, A; Holtkamp, D B; Iverson, A J; Stevens, G D; Turley, W D; Veeser, L R; Wilke, M D; Young, J A

    2011-11-01

    Pyrometric measurements of radiance to determine temperature have been performed on shock physics experiments for decades. However, multi-wavelength pyrometry schemes sometimes fail to provide credible temperatures in experiments, which incur unknown changes in sample emissivity, because an emissivity change also affects the spectral radiance. Hence, for shock physics experiments using pyrometry to measure temperatures, it is essential to determine the dynamic sample emissivity. The most robust way to determine the normal spectral emissivity is to measure the spectral normal-hemispherical reflectance using an integrating sphere. In this paper we describe a multi-wavelength (1.6–5.0 μm) integrating sphere system that utilizes a “reversed” scheme, which we use for shock physics experiments. The sample to be shocked is illuminated uniformly by scattering broadband light from inside a sphere onto the sample. A portion of the light reflected from the sample is detected at a point 12° from normal to the sample surface. For this experiment, we used the system to measure emissivity of shocked tin at four wavelengths for shock stress values between 17 and 33 GPa. The results indicate a large increase in effective emissivity upon shock release from tin when the shock is above 24–25 GPa, a shock stress that partially melts the sample. We also recorded an IR image of one of the shocked samples through the integrating sphere, and the emissivity inferred from the image agreed well with the integrating-sphere, pyrometer-detector data. Here, we discuss experimental data, uncertainties, and a data analysis process. We also describe unique emissivity-measurement problems arising from shock experiments and methods to overcome such problems.

  12. Development of a Thermal/Optical Carbon Analyzer with Multi-Wavelength Capabilities

    NASA Astrophysics Data System (ADS)

    Sumlin, B.; Chow, J. C.; Watson, J. G.; Wang, X.; Gronstal, S.; Chen, L. W. A. A.; Trimble, D.

    2014-12-01

    A thermal/optical carbon analyzer (DRI Model 2015) equipped with a novel seven-wavelength light source (405, 445, 532, 635, 780, 808, and 980 nm) was developed to analyze chemical and optical properties of particles collected on quartz-fiber filters. Based on the DRI Model 2001 carbon analyzer at 633 nm, major modifications were made on mechanical and electrical components, flow control, and the carbon detector to adopt modern technologies, increase instrument reliability, and reduce costs and maintenance. The correlation between wavelength-dependent light attenuation and organic and elemental carbon (OC and EC, respectively) content allows estimation of the amount of brown and black carbon (BrC and BC, respectively) on filters. Continuous monitoring of the light reflected from and transmitted through the filter along with carbon evolved from the filter when heated to different temperatures under either inert or oxidizing gas environments provides insights into the optical properties of the carbon released from the filter; it also allows examination of the charring process as pyrolyzed char has been one of the major uncertainties in quantifying OC and EC. The objectives of this study are: 1) establish performance equivalency between the Model 2015 and Model 2001 DRI carbon analyzers when comparing similar laser wavelength to maintain consistency for long-term network sample analysis; and 2) analyze the multi-wavelength signal to quantify BrC and BC, and to optimize char correction. A selection of samples, including standard chemicals, rural and urban ambient filters, and emission sources from biomass burning, diesel and gasoline engine exhaust, and resuspended dust were measured by both the Model 2015 and Model 2001 analyzers. The instrument design, calibration, comparison with legacy analyzer, and interpretation of the multi-wavelengths measurement will be presented.

  13. The WFCAM multiwavelength Variable Star Catalog

    NASA Astrophysics Data System (ADS)

    Ferreira Lopes, C. E.; Dékány, I.; Catelan, M.; Cross, N. J. G.; Angeloni, R.; Leão, I. C.; De Medeiros, J. R.

    2015-01-01

    Context. Stellar variability in the near-infrared (NIR) remains largely unexplored. The exploitation of public science archives with data-mining methods offers a perspective for a time-domain exploration of the NIR sky. Aims: We perform a comprehensive search for stellar variability using the optical-NIR multiband photometric data in the public Calibration Database of the WFCAM Science Archive (WSA), with the aim of contributing to the general census of variable stars and of extending the current scarce inventory of accurate NIR light curves for a number of variable star classes. Methods: Standard data-mining methods were applied to extract and fine-tune time-series data from the WSA. We introduced new variability indices designed for multiband data with correlated sampling, and applied them for preselecting variable star candidates, i.e., light curves that are dominated by correlated variations, from noise-dominated ones. Preselection criteria were established by robust numerical tests for evaluating the response of variability indices to the colored noise characteristic of the data. We performed a period search using the string-length minimization method on an initial catalog of 6551 variable star candidates preselected by variability indices. Further frequency analysis was performed on positive candidates using three additional methods in combination, in order to cope with aliasing. Results: We find 275 periodic variable stars and an additional 44 objects with suspected variability with uncertain periods or apparently aperiodic variation. Only 44 of these objects had been previously known, including 11 RR Lyrae stars on the outskirts of the globular cluster M 3 (NGC 5272). We provide a preliminary classification of the new variable stars that have well-measured light curves, but the variability types of a large number of objects remain ambiguous. We classify most of the new variables as contact binary stars, but we also find several pulsating stars, among which

  14. A Diagnostic Test for Determining the Location of the GeV Emission in Powerful Blazars

    NASA Technical Reports Server (NTRS)

    Dotson, Amanda; Georganopoulos, Markos; Kazanas, Demosthenes; Perlman, Eric

    2011-01-01

    An issue currently under debate in the literature is how far from the black hole is the Fermi-observed GeV emission of powerful blazars emitted. Here we present a clear diagnostic tool for testing whether the Ge V emission site is located within the sub-pc broad emission line (BLR) region or further out in the few pc scale molecular torus (MT) environment. Within the BLR the scatteri takes place at the onset of the Klein-Nishina regime, causing the electron cooling time to become almost energy independent and as a result, the variation of high-energy emission is expected to be achromatic. Contrarily, if the emission site is located outside the BLR, the expected GeY variability is energy-dependent and with amplitude increasing with energy. We demonstrate this using time-dependent numerical simulations of blazar variability.

  15. Rapid Gamma-Ray and Optical Variability in Bright Fermi Blazars

    NASA Astrophysics Data System (ADS)

    Coppi, Paolo S.; Saitoh, Shinya; Stawarz, Lukasz

    2016-04-01

    Using an "aperture photometry" technique to generate Fermi lightcurves on minute timescales, we have searched the brightest blazar flares for variability down to ~10 minute timescales. We find evidence for strong gamma-ray variability down to ~1 - 2 hour timescales, but not on ~10-30 minute timescales even though the photon statistics are sufficient to detect it. Using SMARTS optical/NIR, we then search for correlated rapid optical variability on similar timescales. While variability on these very short timescales is detected in a few cases, the optical variability amplitude is typically much smaller than the gamma-ray one. Interestingly, on ~1-3 daytimescales the optical and gamma-ray variability are instead well-correlated and of similar amplitude. We discuss the implications of this variability behavior for blazar modeling.

  16. Short timescale variability in the broadband emission of the blazars Mkn421 and Mkn501

    NASA Astrophysics Data System (ADS)

    McKernan, B.; Carson, M. J.; Yaqoob, T.; Fegan, D. J.

    2000-09-01

    We analyse ASCA satellite X-ray data and Whipple Observatory TeV γ-ray data from the Blazars Mkn421 and Mkn501 for short timescale variability using the excess pair fraction method. We discuss the method and the data as well as EPF sensitivity to these data. We find that in these data sets, we can rule out an amplitude of variability greater than 10% on timescales less than 10 min from both sources and at both wavelengths at a confidence level of >99.7%. We discuss briefly the implications of low amplitudes of variability on short timescales for the beamed jet of relativistic particles probably producing these radiations and, we derive limits from the data on the local percentage change in both the lepton density and the magnetic field strength in these Blazar jets.

  17. Undergraduate Participation in the Blazar Monitoring Program at the WKU Bell Observatory

    NASA Astrophysics Data System (ADS)

    Carini, M. T.; Barnaby, D.; Atkerson, A.; Glass, D. A.; Monroe, T. R.; Poteet, C.; Ryle, W. T.; Walters, R.; Wills, W. L.

    2003-12-01

    Blazars are the most extreme example of the AGN phenomena. They have as one of thier defining characteristics large amplitude variability at all wavelengths and on multiple timescales. We have established a Blazar monitoring program using the 0.6m telescope of the Bell Observatory at Western Kentucky University. Undergraduate students play a primary role in this program. They observe with the telescope, reduce and analyze the resulting data and present their results at local, state, and national conferences. We discuss the monitoring program, the results from its first 3 years, and student participation. This program has been funded by the Kentucky Space Grant Consortium, The Kentucky NSF EPSCoR Program, The NASA/Kentucky EPSCoR Program, The Applied Research and Technology Program at Western Kentucky University and the Western Kentucky University Faculty Summer Fellowship program * Now at Indiana University ** Now at Georgia State University

  18. Rapid millimeter and centimeter band flux density increase in the gamma-ray blazar BL Lacertae

    NASA Astrophysics Data System (ADS)

    Hovatta, Talvikki; Richards, Joseph L.; Max-Moerbeck, Walter; Pearson, Timothy J.; Readhead, Anthony C. S.

    2012-11-01

    We have observed a rapid flux density increase of BL Lacertae (2200+420) at 15 GHz (2 cm) and 95 GHz (3 mm) following the report on highest millimeter flux density ever observed at the SMA (ATel #4557). Since 2009, BL Lacertae has been observed approximately twice per week at 15 GHz with the Owens Valley Radio Observatory (OVRO) 40m Telescope as part of our gamma-ray blazar monitoring program (Richards et al....

  19. The Evolution of Swift/BAT blazars and the origin of the MeV background

    SciTech Connect

    Ajello, M.; Costamante, L.; Sambruna, R.M.; Gehrels, N.; Chiang, J.; Rau, A.; Escala, A.; Greiner, J.; Tueller, J.; Wall, J.V.; Mushotzky, R.F.; /NASA, Goddard

    2009-10-17

    We use 3 years of data from the Swift/BAT survey to select a complete sample of X-ray blazars above 15 keV. This sample comprises 26 Flat-Spectrum Radio Quasars (FSRQs) and 12 BL Lac objects detected over a redshift range of 0.03 < z < 4.0. We use this sample to determine, for the first time in the 15-55 keV band, the evolution of blazars. We find that, contrary to the Seyfert-like AGNs detected by BAT, the population of blazars shows strong positive evolution. This evolution is comparable to the evolution of luminous optical QSOs and luminous X-ray selected AGNs. We also find evidence for an epoch-dependence of the evolution as determined previously for radio-quiet AGNs. We interpret both these findings as a strong link between accretion and jet activity. In our sample, the FSRQs evolve strongly, while our best-fit shows that BL Lacs might not evolve at all. The blazar population accounts for 10-20% (depending on the evolution of the BL Lacs) of the Cosmic X-ray background (CXB) in the 15-55 keV band. We find that FSRQs can explain the entire CXB emission for energies above 500 keV solving the mystery of the generation of the MeV background. The evolution of luminous FSRQs shows a peak in redshift (z{sub c} = 4.3 {+-} 0.5) which is larger than the one observed in QSOs and X-ray selected AGNs. We argue that FSRQs can be used as tracers of massive elliptical galaxies in the early Universe.

  20. Lower Limits on Ultrahigh-energy Cosmic Ray and Jet powers of TeV Blazars

    NASA Astrophysics Data System (ADS)

    Razzaque, Soebur; Dermer, Charles D.; Finke, Justin D.

    2012-02-01

    Lower limits on the power emitted in ultrahigh-energy cosmic rays (UHECRs), which are assumed to be protons with energy >~ 1017-1020 eV, are derived for TeV blazars with the assumption that the observed TeV γ-rays are generated due to interactions of these protons with cosmic microwave photons. The limits depend on the spectrum of the injected UHECR protons. While for a -2.2 injection spectrum the lower limits on the powers emitted in UHECRs by 1ES 0229+200, 1ES 1101-232, and 1ES 0347-121 are lower than their respective synchrotron luminosities (~1046 erg s-1), in the case of 1ES 1426+428 it exceeds the corresponding synchrotron luminosity by up to an order of magnitude. The proposed Auger North Observatory should be able to detect 4 × 1019 eV cosmic-ray (CR) protons from 1ES 1426+428 within a few years of operation and test the TeV γ-ray production model by UHECR energy losses while propagating along the line of sight or constrain the intergalactic magnetic field to be larger than ~10-16 G in case of no detection. The lower limits on the apparent-isotropic jet power from accelerated 1010-1020 eV proton spectra in the blazar jet is of the order of the Eddington luminosity of a 109 M ⊙ black hole for a CR injection spectrum -2.2 or harder for all blazars considered except for 1ES 1426+428. In the case of the latter, the apparent-isotropic jet power exceeds the Eddington luminosity by an order of magnitude. For an injection spectrum softer than -2.2, as is required to fit the observed CR data above ~1017-1018 eV, the Eddington luminosity is exceeded by the lower limits on the jet power for all blazars considered.

  1. Blazar B2 1156+29 is in a flaring state in optical.

    NASA Astrophysics Data System (ADS)

    Jorstad, S.; Larionov, V.; Blinov, D.; Morozova, D.; Kopatskaya, E.; Konstantinova, T.; Pavlova, Yu.; Mokrushina, A.

    2012-04-01

    We perform optical photometric and R-band polarimetric monitoring of FSRQ B2 1156+29 = 4C +29.45 = Ton 599 using 1.8-m Perkins telescope (Az,USA), 70-cm AZT-8 (CrAO, Ukraine) and 0.4-m LX-200 (St.Petersburg, Russia) telescopes, partly in the frames of GASP project. Our data show that starting from 2012 April 2 this blazar entered a phase of violent optical activity.

  2. Four Years of EUVE Observations of the Bursting Gamma-Ray Emitting Blazar Markarian 421

    NASA Technical Reports Server (NTRS)

    Cagnoni, Ilaria; Fruscione, Antonella; Papadakis, Iossif

    1998-01-01

    We present spectral and timing analysis of all the data collected by the Extreme Ultraviolet Explorer Satellite (EUVE) for the bright, nearby BL Lacertae object, Markarian 421, during the four-year period 1994-1997. During these years Mrk 421 has been observed by EUVE 4 times with the Deep-Survey/Spectrograph and 2 times with the imaging telescopes for a total of approximately 1.4 7nillions seconds. From 1993 to 1996 three very bright gamma ray flares were also detected by the Whipple observatory. In 1994 Mrk 421 was observed simultaneously by EUVE (Apr 2-12) and IUE one month before the TeV flare; of the 2 EUVF, observations (Feb 4-7 and Apr 25-May 13) of 1995, the second was part of a multiwavelength campaign that mapped the evolution of the TeV flare. In 1996 we observed Mrk 421 twice simultaneously with XTE: one immediately before (Apr 17-30) and another one (May 10-11) right after the May 7 1996 TeV flare. And finally in 1997 from Feb. 7 to Feb. ll. The total light curve seems to be smoothly varying on the long time-scale while on a shorter time-scale there is evidence of an EUVE flare well correlated to the TeV energy 1995 flare. We have analysed the three spectral data set in an homogenous way using the appropriate calibration data for the off-axis observations and our analysis confirms the presence of the absorption features around approximately 70A, in the entire 1995 dataset and possibly in the 1996 data set. We also show the first power spectrum analysis of the Mrk 421 EUVE lightcurves and a comparison with the power spectra predicted by current theoretical models.

  3. SYNCHROTRON LIGHTCURVES OF BLAZARS IN A TIME-DEPENDENT SYNCHROTRON-SELF COMPTON COOLING SCENARIO

    SciTech Connect

    Zacharias, Michael; Schlickeiser, Reinhard E-mail: rsch@tp4.rub.de

    2013-11-10

    Blazars emit non-thermal radiation in all frequency bands from radio to γ-rays. Additionally, they often exhibit rapid flaring events at all frequencies with doubling timescale of the TeV and X-ray flux on the order of minutes, and such rapid flaring events are difficult to explain theoretically. We explore the effect of the synchrotron-self Compton cooling, which is inherently time-dependent, leading to a rapid cooling of the electrons. Having intensively discussed the resulting effects of this cooling scenario on the spectral energy distribution of blazars in previous papers, the effects of the time-dependent approach on the synchrotron lightcurve are investigated here. Taking into account the retardation due to the finite size of the source and the source geometry, we show that the time-dependent synchrotron-self Compton (SSC) cooling still has profound effects on the lightcurve compared to the usual linear (synchrotron and external Compton) cooling terms. This is most obvious if the SSC cooling takes longer than the light crossing timescale. Then, in most frequency bands, the variability timescale is up to an order of magnitude shorter than under linear cooling conditions. This is yet another strong indication that the time-dependent approach should be taken into account for modeling blazar flares from compact emission regions.

  4. Joint Spitzer and AGILE observations of the blazar 3C 454.3

    NASA Astrophysics Data System (ADS)

    Donnarumma, Immacolata; D'Ammando, Filippo

    2007-12-01

    We require SPITZER IRAC and MIPS observations for multifrequency follow-up of the blazar 3C 454.3. During the last three days AGILE is revealing a strong activity in the gamma-rays band. Joint Spitzer and AGILE observations offers the unprecedented great opportunity to study the correlated variability in the low and high energy peaks. This will contribute to improve the understanding of the structure of the inner jet, the origin of the seed photons for the IC process and then discriminating the different emission models in the red blazars during their high gamma-rays activity. The AGILE Team is going to activate a similar ToO to Swift, while a monitoring in the optical energy band is occurring thanks to WEBT. Therefore Spitzer observation of this blazar will give a unique and extraordinary opportunity to investigate its electromagnetic emission on a wide energy range in its strong flaring activity and then to determine its Spectral Energy Distribution.

  5. VizieR Online Data Catalog: Sample of Fermi Blazars (Chen+, 2016)

    NASA Astrophysics Data System (ADS)

    Chen, Y.-Y.; Zhang, X.; Xiong, D.-R.; Wang, S.-J.; Yu, X.-L.

    2016-04-01

    We tried to select a large number of blazars with reliable redshift, radio core and extended radio luminosity at 1.4GHz. Firstly, we considered the following samples of blazars to get the radio core luminosity and extended luminosity at 1.4GHz: Kharb et al. (2010, J/ApJ/710/764), Antonucci & Ulvestad (1985ApJ...294..158A), Cassaro et al. (1999A&AS..139..601C), Murphy et al. (1993MNRAS.264..298M), Landt & Bignall (2008MNRAS.391..967L), Caccianiga & Marcha (2004, Cat. J/MNRAS/348/973), Giroletti et al. (2004). We cross-correlated these samples with the Fermi LAT Third Source Catalog (3FGL), and we acquired the 3FGL spectral index and energy flux at 0.1-100GeV from clean sources in 3FGL (Fermi-LAT Collaboration 2015, J/ApJS/218/23) Using these catalogs, we compiled 201 Fermi blazars. (1 data file).

  6. ON THE REDSHIFT OF THE VERY HIGH ENERGY BLAZAR 3C 66A

    SciTech Connect

    Furniss, A.; Williams, D. A.; Fumagalli, M.; Danforth, C.; Prochaska, J. X.

    2013-03-20

    As a bright gamma-ray source, 3C 66A is of great interest to the high-energy astrophysics community, having a potential for placing cosmological constraints on models for the extragalactic background light (EBL) and the processes which contribute to this photon field. No firm spectroscopic redshift measurement has been possible for this blazar due to a lack of intrinsic emission and absorption features in optical spectra. We present new far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 3C 66A covering the wavelength range 1132-1800 A. The data show a smooth continuum with intergalactic medium absorption features which can be used to place a firm lower limit on the blazar redshift of z {>=} 0.3347. An upper limit is set by statistically treating the non-detection of additional absorbers beyond z = 0.3347, indicating a redshift of less than 0.41 at 99% confidence and ruling out z {>=} 0.444 at 99.9% confidence. We conclude by showing how the redshift limits derived from the COS spectra remove the potential for this gamma-ray emitting blazar to place an upper limit on the flux of the EBL using high energy data from a flare in 2009 October.

  7. Evidence for Secondary Emission as the Origin of Hard Spectra in TeV Blazars

    NASA Astrophysics Data System (ADS)

    Zheng, Y. G.; Kang, T.

    2013-02-01

    We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy γ-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE γ-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy γ-rays, especially the shape of the VHE γ-ray tail of the observed spectra, can be explained by secondary γ-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

  8. EVIDENCE FOR SECONDARY EMISSION AS THE ORIGIN OF HARD SPECTRA IN TeV BLAZARS

    SciTech Connect

    Zheng, Y. G.; Kang, T.

    2013-02-20

    We develop a model for the possible origin of hard, very high energy (VHE) spectra from a distant blazar. In the model, both the primary photons produced in the source and secondary photons produced outside it contribute to the observed high-energy {gamma}-ray emission. That is, the primary photons are produced through the synchrotron self-Compton process, and the secondary photons are produced through high-energy proton interactions with background photons along the line of sight. We apply the model to a characteristic case of VHE {gamma}-ray emission in the distant blazar 1ES 1101-232. Assuming suitable electron and proton spectra, we obtain excellent fits to the observed spectra of this blazar. This indicated that the surprisingly low attenuation of the high-energy {gamma}-rays, especially the shape of the VHE {gamma}-ray tail of the observed spectra, can be explained by secondary {gamma}-rays produced in interactions of cosmic-ray protons with background photons in intergalactic space.

  9. Multi-TeV flaring from blazars: Markarian 421 as a case study

    NASA Astrophysics Data System (ADS)

    Sahu, Sarira; Miranda, Luis Salvador; Rajpoot, Subhash

    2016-03-01

    The TeV blazar Markarian 421 underwent multi-TeV flaring during April 2004 and simultaneously observations in the X-ray and TeV energies were made. It was observed that the TeV outbursts had no counterparts in the lower energy range. One implication of this is that it might be an orphan flare. We show that Fermi-accelerated protons of energy ≤ 168 TeV can interact with the low energy tail of the background synchrotron self-Compton photons in the inner region of the blazar to produce the multi-TeV flare and our results fit very well with the observed spectrum. Based on our study, we predict that the blazars with a deep valley in between the end of the synchrotron spectrum and the beginning of the SSC spectrum are possible candidates for orphan flaring. Future possible candidates for this scenario are the HBLs Mrk 501 and PG 1553 + 113 objects.

  10. SMARTS Optical and Near-Infrared Observations of Fermi LAT Blazars

    NASA Astrophysics Data System (ADS)

    Buxton, Michelle; Isler, J.; Urry, C. M.; Hasan, I.; MacPherson, E.; Bailyn, C. D.; Coppi, P. S.; Gamma-ray Space Telescope, Fermi

    2014-01-01

    Since 2008, we have been monitoring southern-hemisphere blazars at optical and near-infrared (OIR) wavelengths using the SMARTS 1.3m+ANDICAM instrument. Our targets are observed simultaneously with the Fermi Gamma-ray telescope providing us with an opportunity to probe the relative contribution of the thermal and non-thermal emission to the broad-band spectral energy distribution. In this poster we present our results which include OIR light curves that, in some cases, show ‘orphan’ flares in OIR fluxes that are not present in gamma-rays. In addition we see evidence for intra-night variability in some blazars. Discrete correlation functions of simultaneous gamma-ray and OIR fluxes suggest there is no lag or lead time between OIR and gamma-ray fluxes during some flares. Finally, color-magnitude diagrams of some blazars show clear changes in color over flares allowing us to study the evolution of accretion disk vs. jet emission during flaring events.

  11. Scientific Drivers for X-Ray Polarimetry Observations of Active Galactic Nuclei and Blazars

    NASA Astrophysics Data System (ADS)

    Beheshtipour, Banafsheh

    2016-04-01

    Spectropolarimetric observations promise to give us insights into the structure of the the accretion flows and collimated outflows (jets) of mass accreting supermassive black holes. In this talk, I will present results from general relativistic ray tracing studies showing that the spectropolarimetric observations of bright Seyfert galaxies give information that is complimentary to that from Fe K-alpha line and Compton reflection hump spectroscopy. Combining polarimetric with spectral and timing results will allow us to pin down the physical properties of the accretion disk and corona with higher accuracy and with smaller systematic uncertainties. The X-ray polarimetric observations of blazars (mass accreting supermassive black holes with jets aligned with the line of sight) will allow us to study the structure of the magnetic field inside the jets (and thus to constrain the jet launching mechanism) in high synchrotron peaked blazars, and to identify and constrain the emission mechanism responsible for the X-ray to gamma-ray emission in low and intermediate synchrotron peaked blazars.

  12. Intergalactic magnetic fields and gamma-ray observations of extreme TeV blazars

    SciTech Connect

    Arlen, Timothy C.; Vassilev, Vladimir V.; Weisgarber, Thomas; Wakely, Scott P.; Shafi, S. Yusef

    2014-11-20

    The intergalactic magnetic field (IGMF) in cosmic voids can be indirectly probed through its effect on electromagnetic cascades initiated by a source of teraelectronvolt (TeV) gamma-rays, such as active galactic nuclei (AGNs). AGNs that are sufficiently luminous at TeV energies, 'extreme TeV blazars', can produce detectable levels of secondary radiation from inverse Compton scattering of the electrons in the cascade, provided that the IGMF is not too large. We review recent work in the literature that utilizes this idea to derive constraints on the IGMF for three TeV-detected blazars, 1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also investigate four other hard-spectrum TeV blazars in the same framework. Through a recently developed, detailed, three-dimensional particle-tracking Monte Carlo code, incorporating all major effects of QED and cosmological expansion, we research the effects of major uncertainties, such as the spectral properties of the source, uncertainty in the ultraviolet and far-infrared extragalactic background light, undersampled very high energy (energy ≥100 GeV) coverage, past history of gamma-ray emission, source versus observer geometry, and the jet AGN Doppler factor. The implications of these effects on the recently reported lower limits of the IGMF are thoroughly examined to conclude that the presently available data are compatible with a zero-IGMF hypothesis.

  13. HIGHLY VARIABLE OBJECTS IN THE PALOMAR-QUEST SURVEY: A BLAZAR SEARCH USING OPTICAL VARIABILITY

    SciTech Connect

    Bauer, Anne; Baltay, Charles; Coppi, Paolo; Ellman, Nancy; Glikman, Eilat; Jerke, Jonathan; Rabinowitz, David; Scalzo, Richard; Donalek, Ciro; Drake, Andrew; Djorgovski, S. G.; Graham, Matthew; Mahabal, Ashish; Williams, Roy

    2009-11-01

    We identify 3113 highly variable objects in 7200 deg{sup 2} of the Palomar-QUEST (PQ) Survey, which each varied by more than 0.4 mag simultaneously in two broadband optical filters on timescales from hours to roughly 3.5 years. The primary goal of the selection is to find blazars by their well-known violent optical variability. Because most known blazars have been found in radio and/or X-ray wavelengths, a sample discovered through optical variability may have very different selection effects, elucidating the range of behavior possible in these systems. A set of blazars selected in this unusual manner will improve our understanding of the physics behind this extremely variable and diverse class of active galactic nucleus (AGN). The object positions, variability statistics, and color information are available using the PQ CasJobs server. The time domain is just beginning to be explored over large sky areas; we do not know exactly what a violently variable sample will hold. About 20% of the sample has been classified in the literature; over 70% of those objects are known or likely AGNs. The remainder largely consists of a variety of variable stars, including a number of RR Lyrae and cataclysmic variables.

  14. Multiband optical variability of three TeV blazars on diverse time-scales

    NASA Astrophysics Data System (ADS)

    Gupta, Alok C.; Agarwal, A.; Bhagwan, J.; Strigachev, A.; Bachev, R.; Semkov, E.; Gaur, H.; Damljanovic, G.; Vince, O.; Wiita, Paul J.

    2016-05-01

    We present our optical photometric observations of three TeV blazars, PKS 1510-089, PG 1553+113, and Mrk 501, taken using two telescopes in India, one in Bulgaria, one in Greece, and one in Serbia during 2012-2014. These observations covered a total of 95 nights with a total of 202 B filter frames, 247 images in V band, 817 in R band while 229 images were taken in the I filter. This work is focused on multiband flux and colour variability studies of these blazars on diverse time-scales which are useful in understanding the emission mechanisms. We studied the variability characteristics of above three blazars and found all to be active over our entire observational campaigns. We also searched for any correlation between the brightness of the sources and their colour indices. During the times of variability, no significant evidence for the sources to display spectral changes correlated with magnitude was found on time-scales of a few months. We briefly discuss the possible physical mechanisms most likely responsible for the observed flux variability.

  15. Intergalactic Magnetic Fields and Gamma-Ray Observations of Extreme TeV Blazars

    NASA Astrophysics Data System (ADS)

    Arlen, Timothy C.; Vassilev, Vladimir V.; Weisgarber, Thomas; Wakely, Scott P.; Yusef Shafi, S.

    2014-11-01

    The intergalactic magnetic field (IGMF) in cosmic voids can be indirectly probed through its effect on electromagnetic cascades initiated by a source of teraelectronvolt (TeV) gamma-rays, such as active galactic nuclei (AGNs). AGNs that are sufficiently luminous at TeV energies, "extreme TeV blazars", can produce detectable levels of secondary radiation from inverse Compton scattering of the electrons in the cascade, provided that the IGMF is not too large. We review recent work in the literature that utilizes this idea to derive constraints on the IGMF for three TeV-detected blazars, 1ES 0229+200, 1ES 1218+304, and RGB J0710+591, and we also investigate four other hard-spectrum TeV blazars in the same framework. Through a recently developed, detailed, three-dimensional particle-tracking Monte Carlo code, incorporating all major effects of QED and cosmological expansion, we research the effects of major uncertainties, such as the spectral properties of the source, uncertainty in the ultraviolet and far-infrared extragalactic background light, undersampled very high energy (energy >=100 GeV) coverage, past history of gamma-ray emission, source versus observer geometry, and the jet AGN Doppler factor. The implications of these effects on the recently reported lower limits of the IGMF are thoroughly examined to conclude that the presently available data are compatible with a zero-IGMF hypothesis.

  16. Stable multi-wavelength fiber laser with single-mode fiber in a Sagnac loop.

    PubMed

    Wang, Pinghe; Wang, Lei; Shi, Guohua; He, Tiejun; Li, Heping; Liu, Yong

    2016-04-20

    In this paper, we propose and experimentally demonstrate a stable multi-wavelength fiber laser at 1.5 μm with single-mode fiber (SMF). The Sagnac loop structure with a 48.6:51.4 coupler and 2 km SMF has an intensity-dependent loss, which contributes to suppress the mode competition in the cavity and leads to a steady multi-wavelength output. In the experiment, five stable lasing wavelengths are obtained with a pump power of 300 mW at 980 nm. The demonstrated multi-wavelength fiber laser has great potential for applications in optical communications and optical sensing systems. PMID:27140108

  17. Multiwavelength Imaging of Planetary Nebulae: Resolving & Disentangling Structure

    NASA Astrophysics Data System (ADS)

    Freeman, Marcus J.

    2015-10-01

    Planetary nebulae (PNe) represent the late stages of low-mass stellar evolution. The formation of the myriad of PNe morphologies involves processes that are present in many other astrophysical systems such as the wind-blown bubbles of massive stars. In this dissertation we present the results of an X-ray study of PNe, and two modeling projects that incorporate the resulting data with the goal of furthering our understanding of their X-ray properties and morphologies, and the 3D multiwavelength structure of PNe. This work expands the Chandra Planetary Nebula Survey (ChanPlaNS), which was designed to investigate X-ray emission from PNe, from 35 to 59 objects. The results from Cycle 14 Chandra observations of 24 PNe brought the overall ChanPlaNS diffuse X-ray detection rate to ~27% and the point source detection rate to ∼36%. The detection of diffuse X-ray emission is unmistakably associated with young (≲ 5 × 10^3 yr), compact (R_neb ≲ 0.15 pc) PNe that exhibit closed elliptical structures and high electron densities (n_e ≳ 10^3 cm^-3). Utilizing the ChanPlaNS data for 14 PNe that exhibit diffuse X-ray emission, we constructed simple, spherically symmetric two-phase models using the astrophysical modeling tool, SHAPE. Our models consisted of a hot bubble and swept-up shell with the intent of investigating the X- ray morphology of these objects and the extinction caused by the swept-up shell. We compared simulated and observed radial profiles and we conclude that while most (∼79%) PNe are best described by a limb-darkened X-ray morphology, this is due to nebular extinction of an intrinsically limb-brightened hot bubble structure. Expanding upon our two-phase model, we used SHAPE to generate a 3D model of the brightest diffuse X-ray PN, BD+30 3639, with the model constrained by previously published multiwavelength data extending from the radio to the X-ray regimes. Our aim was to investigate the multiwavelength 3D morphology of this well-studied nebula and

  18. Optical Spectroscopic Observations of Gamma-ray Blazar Candidates. IV. Results of the 2014 Follow-up Campaign

    NASA Astrophysics Data System (ADS)

    Ricci, F.; Massaro, F.; Landoni, M.; D'Abrusco, R.; Milisavljevic, D.; Stern, D.; Masetti, N.; Paggi, A.; Smith, Howard A.; Tosti, G.

    2015-05-01

    The extragalactic γ-ray sky is dominated by the emission arising from blaz