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Sample records for multiwavelength blazar analysis

  1. 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.

  2. 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.

  3. A MULTIWAVELENGTH STUDY OF THREE HYBRID BLAZARS

    SciTech Connect

    Stanley, E. C.; Lister, M. L.; Kharb, P.; 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.

  4. 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.

  5. 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.

  6. Multiwavelength temporal variability of the blazar 3C 454.3 during 2014 activity phase

    NASA Astrophysics Data System (ADS)

    Kushwaha, Pankaj; Gupta, Alok C.; Misra, Ranjeev; Singh, K. P.

    2017-01-01

    We present a multiwavelength temporal analysis of the blazar 3C 454.3 during the high γ-ray active period from May to December, 2014. Except for X-rays, the period is well sampled at near-infrared (NIR)-optical by the Small and Moderate Aperture Research Telescope System (SMARTS) facility, and the source is detected continuously on daily time-scale in the Fermi-Large Area Telescope γ-ray band. The source exhibits diverse levels of variability with many flaring/active states in the continuously sampled γ-ray light curve which are also reflected in the NIR-optical light curves and the sparsely sampled X-ray light curve by the Swift-XRT. Multiband correlation analysis of this continuous segment during different activity periods shows a change of state from no lags between IR and γ-ray, optical and γ-ray, and IR and optical to a state where γ-ray lags the IR/optical by ˜3 d. The results are consistent with the previous studies of the same during various γ-ray flaring and active episodes of the source. This consistency, in turn, suggests an extended localized emission region with almost similar conditions during various γ-ray activity states. On the other hand, the delay of γ-ray with respect to IR/optical and a trend similar to IR/optical in X-rays along with strong broad-band correlations favour magnetic field related origin with X-ray and γ-ray being inverse Comptonization of IR/optical photons and external radiation field, respectively.

  7. Multi-wavelength Study of Blazars Using Variability as a Tool

    NASA Astrophysics Data System (ADS)

    Baliyan, Kiran S.; Kaur, Navpreet; Chandra, Sunil; Sameer, Sameer; Ganesh, Shashikiran

    2016-09-01

    Active galactic nuclei (AGN) are too compact to be resolved by any existing optical telescope facility, making it difficult to understand their structure and the emission processes responsible for their huge energy output. However, variability, one of their characteristic properties, provides a tool to probe the inner regions of AGN. Blazars are the best candidates for such a study, and hence a considerable amount of effort is being made to investigate variability in these sources across the electromagnetic spectrum. Here, using the Mt. Abu infrared observatory (MIRO) blazar monitoring program, we present intra-night, inter-night, and long term aspects of the variability in S5 0716+71, 3C66A, and OJ 287. These stars show significant variability on short (a few tens of mins, to a few hours, to a few days) to long term (months to years) timescales. Based on the light travel time argument, the shortest variability timescales (micro-variability) provide upper limits to the size of the emission region. While S5 0716 shows a very high duty cycle of variability (> 80 %), 3C66A shows a much lower intra day variability (IDV) duty cycle (< 20 %). All three show rapid variations within 2.5 to 3.5 hr, which, perhaps, are generated near the vicinity of black holes. Assuming this, estimates of the masses of the black holes are made at 10^{9} , 8×10^{8}, and 2.7×10^{9} M⨀ for S5 0716+71, 3C66A, and OJ 287, respectively. Multi-wavelength light-curves for the blazar PKS 1510-089 are discussed to infer the emission processes responsible for the recent flaring episodes in this source.

  8. The Swift/UVOT Blazar Image Processing For Multi-Wavelength Campaigns And OJ287

    NASA Astrophysics Data System (ADS)

    Verrecchia, Francesco; Leto, C.; Giommi, P.; Ciprini, S.; et al.

    2016-10-01

    In the last years the Swift mission monitoring of non-GRB sources has become an essential tool in multi-frequencies time- domain studies. The ASI Science Data Center (ASDC), which hosts one of the three official Swift data archives and was deputy for the X-ray Telescope (XRT) Deep and Serendipitous surveys, has a long experience on Blazar multi-wavelength campaigns and has recently participated to various campaigns contemporary to observations of new space missions, such as Planck and NuSTAR (Balokovic et al 2016, Furniss et al. 2015, Giommi et al 2012). Since 2006 at the ASDC we have started an activity of UltraViolet Optical Telescope (UVOT) Blazar image processing. The dedicated standard processing procedure of UVOT images, using official software and calibrations, has the goal to add UVOT fluxes to source Spectral Energy Distributions (SEDs) and also support variability studies with comparison to X and gamma-ray data, even on the intra-observation time-scale. Currently data of about 430 sources have been processed, and results have been used in recent papers, such as those on Mkn 421 (Balokovic et al.2016) and OJ 287. The OJ287 UVOT image complete data processing is updated at each observation campaign and results have been published in some survey papers. The 2015 observations have been included in the internal long-term monitoring of the source and considered in the recent multi-frequency study Valtonen et al.(2016) of the new optical-UV outburst of the 12 years cycle, with comparison to the ground optical data and the contemporaneous Swift X-ray ones. We will report the results obtained with UVOT data.

  9. MULTIWAVELENGTH EVIDENCE FOR QUASI-PERIODIC MODULATION IN THE GAMMA-RAY BLAZAR PG 1553+113

    SciTech Connect

    Ackermann, M.; Buehler, R.; Ajello, M.; Albert, A.; Baldini, L.; Blandford, R. D.; Bloom, E. D.; Bottacini, E.; Caliandro, G. A.; Atwood, W. B.; Ballet, J.; Bastieri, D.; Buson, S.; Becerra Gonzalez, J.; Bellazzini, R.; Bissaldi, E.; Bonino, R.; Bregeon, J. [Laboratoire Univers et Particules de Montpellier, Université Montpellier, CNRS Bruel, P. E-mail: sara.cutini@asdc.asi.it E-mail: stefan@astro.su.se [Laboratoire Leprince-Ringuet, École polytechnique, CNRS and others

    2015-11-10

    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.

  10. 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

  11. Multiwavelength Observations of the Very High Energy Blazar 1ES 2344+514

    NASA Astrophysics Data System (ADS)

    Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Boltuch, D.; Bugaev, V.; Cannon, A.; Ciupik, L.; Cogan, P.; Colin, P.; Dickherber, R.; Falcone, A.; Fegan, S. J.; Finley, J. P.; Fortin, P.; Fortson, L. F.; Furniss, A.; Gall, D.; Gillanders, G. H.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Horan, D.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Kildea, J.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Maier, G.; Moriarty, P.; Mukherjee, R.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Smith, A. W.; Steele, D.; Swordy, S. P.; Theiling, M.; Toner, J. A.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wagner, R.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Wood, M.; Zitzer, B.

    2011-09-01

    Multiwavelength observations of the high-frequency-peaked blazar 1ES 2344+514 were performed from 2007 October to 2008 January. The campaign represents the first contemporaneous data on the object at very high energy (VHE, E >100 GeV) γ-ray, X-ray, and UV energies. Observations with VERITAS in VHE γ-rays yield a strong detection of 20σ with 633 excess events in a total exposure of 18.1 hr live time. A strong VHE γ-ray flare on 2007 December 7 is measured at F(>300 GeV) = (6.76 ± 0.62) × 10-11 photons cm-2 s-1, corresponding to 48% of the Crab Nebula flux. Excluding this flaring episode, nightly variability at lower fluxes is observed with a time-averaged mean of F(>300 GeV) = (1.06 ± 0.09) × 10-11 photons cm-2 s-1 (7.6% of the Crab Nebula flux). The differential photon spectrum between 390 GeV and 8.3 TeV for the time-averaged observations excluding 2007 December 7 is well described by a power law with a photon index of Γ = 2.78 ± 0.09stat ± 0.15syst. On the flaring night of 2007 December 7 the measured VHE γ-ray photon index was Γ = 2.43 ± 0.22stat ± 0.15syst. Over the full period of VERITAS observations contemporaneous X-ray and UV data were taken with Swift and RXTE. The measured 2-10 keV flux ranged by a factor of ~7 during the campaign. On 2007 December 8 the highest ever observed X-ray flux from 1ES 2344+514 was measured by Swift X-ray Telescope at a flux of F(2-10 keV) = (6.28 ± 0.31) × 10-11 erg cm-2 s-1. Evidence for a correlation between the X-ray flux and VHE γ-ray flux on nightly timescales is indicated with a Pearson correlation coefficient of r = 0.60 ± 0.11. Contemporaneous spectral energy distributions (SEDs) of 1ES 2344+514 are presented for two distinct flux states. A one-zone synchrotron self-Compton (SSC) model describes both SEDs using parameters consistent with previous SSC modeling of 1ES 2344+514 from non-contemporaneous observations.

  12. MULTIWAVELENGTH OBSERVATIONS OF THE VERY HIGH ENERGY BLAZAR 1ES 2344+514

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Boltuch, D.; Arlen, T.; Fegan, S. J.; Aune, T.; Furniss, A.; Beilicke, M.; Bugaev, V.; Dickherber, R.; Cannon, A.; Ciupik, L.; Fortson, L. F.; Cogan, P.; Colin, P.; Falcone, A.; Finley, J. P.; Gall, D.; Fortin, P.

    2011-09-10

    Multiwavelength observations of the high-frequency-peaked blazar 1ES 2344+514 were performed from 2007 October to 2008 January. The campaign represents the first contemporaneous data on the object at very high energy (VHE, E >100 GeV) {gamma}-ray, X-ray, and UV energies. Observations with VERITAS in VHE {gamma}-rays yield a strong detection of 20{sigma} with 633 excess events in a total exposure of 18.1 hr live time. A strong VHE {gamma}-ray flare on 2007 December 7 is measured at F(>300 GeV) = (6.76 {+-} 0.62) x 10{sup -11} photons cm{sup -2} s{sup -1}, corresponding to 48% of the Crab Nebula flux. Excluding this flaring episode, nightly variability at lower fluxes is observed with a time-averaged mean of F(>300 GeV) = (1.06 {+-} 0.09) x 10{sup -11} photons cm{sup -2} s{sup -1} (7.6% of the Crab Nebula flux). The differential photon spectrum between 390 GeV and 8.3 TeV for the time-averaged observations excluding 2007 December 7 is well described by a power law with a photon index of {Gamma} = 2.78 {+-} 0.09{sub stat} {+-} 0.15{sub syst}. On the flaring night of 2007 December 7 the measured VHE {gamma}-ray photon index was {Gamma} = 2.43 {+-} 0.22{sub stat} {+-} 0.15{sub syst}. Over the full period of VERITAS observations contemporaneous X-ray and UV data were taken with Swift and RXTE. The measured 2-10 keV flux ranged by a factor of {approx}7 during the campaign. On 2007 December 8 the highest ever observed X-ray flux from 1ES 2344+514 was measured by Swift X-ray Telescope at a flux of F(2-10 keV) = (6.28 {+-} 0.31) x 10{sup -11} erg cm{sup -2} s{sup -1}. Evidence for a correlation between the X-ray flux and VHE {gamma}-ray flux on nightly timescales is indicated with a Pearson correlation coefficient of r = 0.60 {+-} 0.11. Contemporaneous spectral energy distributions (SEDs) of 1ES 2344+514 are presented for two distinct flux states. A one-zone synchrotron self-Compton (SSC) model describes both SEDs using parameters consistent with previous SSC modeling of 1ES

  13. 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.

  14. 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.

  15. Multiwavelength Study of Fermi-LAT blazars Variability and Radiation Production Mechanisms

    NASA Astrophysics Data System (ADS)

    Britto, R. J.; Bottacini, E.; Böttcher, M.; Buckley, D. A. H.; Buson, S.; Lott, B.; Marais, J. P.; Meintjes, P. J.; Razzaque, S.; van Soelen, B.

    2016-12-01

    Quasars constitute a subclass of radio-loud active galactic nuclei that release a tremendous amount of non-thermal radiation through a pair of twin jets. When one of these jets is aligned close to the direction of the Earth, the object is then called a blazar. A consistent monitoring of these sources can help to unveil physical mechanisms at the origin of the radiation production that spreads throughout the whole electromagnetic spectrum, from radio waves to γ rays. The goal of this paper is to report some current works being undertaken in term of both spectral studies and time domain analyses of bright blazars which are observed with the Fermi Gamma-Ray Space Telescope and by South Africa-based optical telescopes. In particular, we present our recent and current studies on blazars 3C 454.3 and NVSS J141922-083830 respectively.

  16. 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.

  17. Prominent activity of the blazar OJ 287 in 2005. XMM-Newton and multiwavelength observations

    NASA Astrophysics Data System (ADS)

    Ciprini, S.; Raiteri, C. M.; Rizzi, N.; Agudo, I.; Foschini, L.; Fiorucci, M.; Takalo, L. O.; Villata, M.; Ostorero, L.; Sillanpää, A.; Valtonen, M.; Tosti, G.; Wagner, S. J.; Aller, H.; Aller, M. F.; Arai, A.; Arkharov, A. A.; Bakis, V.; Bagaglia, M.; Böttcher, M.; Buemi, C.; Carosati, D.; Chen, W. P.; Efimov, Y.; Emmanoulopoulos, D.; Erdem, A.; Fuhrmann, L.; Frasca, A.; Fullhart, M.; Goyal, A.; Heidt, J.; Hovatta, T.; Hroch, F.; Ibrahimov, M. A.; Jilková, L.; Joshi, M.; Kamada, M.; Katsuura, M.; Kinoshita, D.; Kostov, A.; Kotaka, D.; Kovalev, Y. Y.; Krejcová, T.; Krichbaum, T.; Gopal-Krishna; Kurosaki, M.; Kurtanidze, O.; Lahteenmaki, A.; Lanteri, L.; Larionov, V.; Lee, C.-U.; Letho, H.; Leto, P.; Li, J.; Lindfors, E.; Münz, F.; Marilli, E.; Matsubara, Y.; Mizoguchi, S.; Mondal, S.; Nakamura, K.; Nieppola, E.; Nilsson, K.; Nishiyama, S.; Nucciarelli, G.; Ogino, A.; Ohlert, J.; Oksanen, A.; Ovcharov, E.; Pak, S.; Pasanen, M.; Pullen, C.; Pursimo, T.; Ros, J. A.; Sadakane, K.; Sadun, A. C.; Sagar, R.; Sohnk, B.-W.; Sumitomo, N.; Tanaka, K.; Trigilio, C.; Torniainenk I.; Tornikoski, M.; Umana, G.; Ungerechts, H.; Valtaoja, E.; Volvach, A.; Webb, J. R.; Wu, J.; Yim, H.-S.; Zhang, Y.

    Two guest-observer XMM-Newton pointings of the blazar OJ 287 in 2005 are introduced, along with part of the radio, mm, near-IR, and optical data obtained during a coordinated and intensive WEBT campaign, during longer-term monitoring observations performed by teams of the ENIGMA network, and during other independent observing programs (like VLBA observations). In that year OJ 287 showed an interesting variable behavior in the optical band. An optical outburst, well matched by our WEBT observations, is claimed in the period Oct.-Nov. 2005, and the XMM-Newton X-ray observations are performed in correspondence with two active optical states (an intermediate flare and such outburst). X-ray data indicates different flux levels, spectral slopes, and emission components, and VLBA radio maps are consistent with a jet precession model. This appreciable observing effort is still ongoing (a further XMM-Newton pointing is planned in 2008), joined with further parallel/multi-monitoring observing programmes devoted to this interesting object.

  18. Multi-Wavelength Observations On The Gamma-Ray Blazar PG1553+113 As A Probe For Geometrical Periodical Modulation

    NASA Astrophysics Data System (ADS)

    Stamerra, Antonio; Prandini, E.; Paiano, S.; Da Vela, P.; Gareth, H.; Covino, S.; Cutini, S.; Sandrinelli, A.; Sobacchi, E.; Sormani, M. C.

    2016-10-01

    New claims of periodic variability from gamma-ray blazars have been reported, possibly pointing at milli-pc SMBH binary systems. A modulation of 2 year on 3.5 cycles was recently discovered with Fermi/LAT on the blazar PG1553+113 - for the first time in gamma-rays with high significance - and confirmed by optical lightcurves. Other possible gamma-ray periodic variations have been claimed on PKS 2155-304 and PKS 0537 by Sandrinelli et al. (2015, 2016). The interpretation of such periodicity, when confirmed with continuous observations in following years, is not straightforward. Emission from blazars is dominated by non-thermal emission from the jet; different processes in the jet or at its base, may lead to quasi-periodic emission. We used multi-wavelength (MWL) observations on PG1553+113 to investigate if the observed modulation can be explained with geometrical variations in the jet, possibly pointing to jet precession or to an helical pattern. The ongoing MWL monitoring campaign from radio to very-high energy gamma-ray bands, led by the MAGIC collaboration, will follow the maximum expected at the beginning of 2017, and will allow to set tighter constrains on underlying periodic processes.

  19. 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.

  20. 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

  1. 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.

  2. Multiwavelength analysis of four millisecond pulsars

    NASA Astrophysics Data System (ADS)

    Guillemot, L.; Cognard, I.; Johnson, T. J.; Venter, C.; Harding, A. K.

    2011-08-01

    Radio timing observations of millisecond pulsars (MSPs) in support of Fermi LAT observations of the gamma-ray sky enhance the sensitivity of high-energy pulsation searches. With contemporaneous ephemerides we have detected gamma-ray pulsations from PSR B1937+21, the first MSP ever discovered, and B1957+20, the first known black-widow system. The two MSPs share a number of properties: they are energetic and distant compared to other gamma-ray MSPs, and both of them exhibit aligned radio and gamma-ray emission peaks, indicating co-located emission regions in the outer magnetosphere of the pulsars. However, radio observations are also crucial for revealing MSPs in Fermi unassociated sources. In a search for radio pulsations at the position of such unassociated sources, the Nançay Radio Telescope discovered two MSPs, PSRs J2017+0603 and J2302+4442, increasing the sample of known Galactic disk MSPs. Subsequent radio timing observations led to the detection of gamma-ray pulsations from these two MSPs as well. We describe multiwavelength timing and spectral analysis of these four pulsars, and the modeling of their gamma-ray light curves in the context of theoretical models.

  3. Analysis of multiwavelength coherent beam combining effect.

    PubMed

    Kai, Han; Xiaojun, Xu; Zejin, Liu

    2012-12-01

    The combination effect of multiwavelength active coherent beam combination (CBC) is investigated theoretically. The dependence of the combination effect on the optical path control precision, spectral width, wavelength number, and channel number is revealed. In the case of small optical path variance, the combination effect approximately decreases in quadratic form with wavelength number N, spectral width Δν, and optical path variance σ increasing. In the case of large optical path variance, the combination effect is independent of the optical path variance and the spectral width. The larger the wavelength number is, the smaller the Strehl ratio expectation is, and it finally degenerates to the incoherent combination. The necessity of optical path control is discussed. This study is helpful for multiwavelength CBC system design and the combination effect estimation.

  4. 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.

  5. A MULTI-WAVELENGTH POLARIMETRIC STUDY OF THE BLAZAR CTA 102 DURING A GAMMA-RAY FLARE IN 2012

    SciTech Connect

    Casadio, Carolina; Gómez, José L.; Agudo, Iván; Molina, Sol N.; Jorstad, Svetlana G.; Marscher, Alan P.; Bala, Vishal; Joshi, Manasvita; Taylor, Brian; Williamson, Karen E.; Larionov, Valeri M.; Blinov, Dmitry A.; Grishina, Tatiana S.; Hagen-Thorn, Vladimir A.; Smith, Paul S.; Gurwell, Mark A.; Lähteenmäki, Anne; Arkharov, Arkady A.; Borman, George A.; Paola, Andrea Di; and others

    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{sub >100} {sub MeV} = 5.2 ± 0.4 × 10{sup −6} photons cm{sup −2} s{sup −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.

  6. Multiwavelength analysis of a solar quiet region

    NASA Astrophysics Data System (ADS)

    Tsiropoula, G.; Tziotziou, K.; Schwartz, P.; Heinzel, P.

    2009-01-01

    Context: We examine oscillatory phenomena in a solar network region from multi-wavelength observations obtained by the ground-based Dutch Open Telescope (DOT) and by the Coronal Diagnostic Spectrometer (CDS) on the spacecraft Solar and Heliospheric Observatory (SoHO). The observations were obtained during a coordinated observing campaign in October 2005. Aims: We investigate the temporal variations of the intensities and the velocities in two distinct regions of the quiet Sun, one containing several dark mottles and the other several bright points defining the network boundaries (NB). The aim is to find similarities and/or differences in the oscillatory phenomena observed in these two regions and in different spectral lines formed from the chromosphere to the transition region, as well as the propagation characteristics of waves. Methods: Intensity and velocity variations are studied with wavelet and phase difference analyses. Results: Both regions (i.e. mottles and NB) show a periodicity of ~5 min in all considered lines. The V-V phase differences in the NB region point to an upward propagation of waves; in the region of mottles, for periods of 250-400 s, the phase difference is mainly negative, which suggests a downward propagation, in turn indicating a refraction of waves from the inclined magnetic field of mottles along the line-of-sight. Conclusions: The phase differences at the NB arise from a predominance of upward propagating waves. In the mottles' region, the negative phase differences we found suggest that propagating waves encounter a boundary and are refracted and reflected. Of course, several limitations exist in the exact interpretation of the phase differences, e.g. the complex topology of the magnetic field, the formation conditions and heights of the examined spectral lines, and the low spatial resolution.

  7. 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).

  8. ANTARES Constrains a Blazar Origin of Two IceCube PeV Neutrino Events

    NASA Technical Reports Server (NTRS)

    Adrian-Martinez, S.; Albert, A.; André, M.; Anton, G.; Ardid, M.; Aubert, J. J.; Baret, B.; Barrios, J.; Basa, S.; Gehrels, N.; Baumgartner, W.; Thompson, D. J.; Ojha, R.

    2015-01-01

    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 di erent 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.

  9. 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.

  10. 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.

  11. B-FlaP: Classifying Gamma-ray Blazars Using Machine Learning

    NASA Astrophysics Data System (ADS)

    Thompson, David John; Chiaro, Graziano; Giroletti, Marcello; Salvetti, David; La Mura, Giovanni; Bastieri, Denis

    2017-01-01

    In the Third Fermi Large Area Telescope Catalog of high-energy gamma-ray sources, 573 are listed as Blazar Candidates of Uncertain type (BCU), or sources without a conclusive classification. Blazar Flaring Patterns (B-FlaP) uses Empirical Cumulative Distribution Function and Artificial Neural Network machine-learning techniques for a fast method of screening and classification of BCUs based on gamma-ray data only, when rigorous multiwavelength analysis is not available. In this study radio analysis and direct observations by ground-based optical observatories are used to validate the B-FlaP method. Tests indicate that the method is effective, suggesting that 342 sources are likely BL Lac objects, 154 are likely Flat Spectrum Radio Quasars, with only 77 remaining uncertain. 53 of the BCUs appear to be High Synchrotron Peaked blazars, a class of particular interest to ground-based imaging atmospheric Cherenkov telescopes.

  12. 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.

  13. Multiwavelength variability analysis of the FSRQ 3C 279

    NASA Astrophysics Data System (ADS)

    Patiño-Álvarez, V.; Chavushyan, V.; León-Tavares, J.; Carramiñana, A.; Carrasco, L.; Fernandes, S.; Schlegel, E. M.; López-Rodríguez, E.

    2015-03-01

    We present a multifrequency analysis of the variability in the flat-spectrum radio quasar 3C 279 from 2008 to 2014. Our multiwavelength dataset includes gamma-ray data from Fermi/LAT (Abdo et al. 2009), observations in 1mm from SMA (Gurwell et al. 2007), Near Infrared from OAGH (Carramiñana & Carrasco 2009) and SMARTS (Bonning et al. 2012); optical V band from the Steward Observatory (Smith et al. 2009) and SMARTS; optical spectra from OAGH (Patiño-Álvarez et al. 2013) and the Steward Observatory; and polarization spectra from the Steward Observatory. The light curves are shown in Fig. 1. Six out of seven optical activity periods identified within our dataset show clear counterparts in mm, NIR and gamma-rays, however, the late 2011 - early 2012 optical flare does not have a counterpart in the GeV regime. In this contribution, we discuss the flaring evolution of 3C 279 and speculate about the production of the anomalous activity period.

  14. MULTIWAVELENGTH ANALYSIS OF A SOLAR FLARE ON 2002 APRIL 15

    NASA Technical Reports Server (NTRS)

    Sui, Linhui; Holman, Gordon D.; White, Stephen M.; Zhang, Jie

    2005-01-01

    We carried out a multiwavelength analysis of the solar limb flare on 2002 April 15. The observations all indicate that the flare occurred in an active region with an asymmetric dipole magnetic configuration. The earlier conclusion that magnetic reconnection is occurring in a large-scale current sheet in this flare is M e r supported by these observations: (1) Several bloblike sources, seen in RHESSI 12-25 keV X-ray images later in the flare, appeared along a line above the flare loops. These indicate the continued presence of the current sheet and are likely to be magnetic islands in the stretched sheet produced by the tearing-mode instability. (2) A cusplike structure is seen in Nobeyama Radioheliogiaph (NoRH) 34 GHz microwave images around the time of the peak flare emission. We quantitatively demonstrate that the X-ray-emitting thermal plasma seen with RHESSI had a higher temperature than the microwave-emitting plasma seen with NoRH. Since the radio data preferentially see cooler thermal plasma, this result is consistent with the picture in which energy release occurs at progressively greater heights and the hard X-rays see hot new loops while the radio sees older cooling loops. The kinetic energy of the coronal mass ejection (CME) associated with this flare was found to be about 1 order of magnitude less than both the thermal energy in the hot plasma and the nonthermal energy carried by the accelerated electrons in the flare, as deduced from the RHESSI observations. This contrasts with the higher CME kinetic energies typically deduced for large flares.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. 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.

  20. Computing the Periods of Light Variation of Blazar Objects 3C279 and OJ 287 with Autoregressive Spectral Analysis Method

    NASA Astrophysics Data System (ADS)

    Tang, Jie; Zhang, Xiao-juan; Pang, Qiao; Zhang, Hao-Jing; Zheng, Yong-Gang; Zhang, Xiong

    2010-04-01

    The light variability is one of the main characteristics of blazar objects. Because of the complexity of their light curves, the present periodicity analysis methods are not yet perfect. Based on the modern spectral estimate theory, this paper has described in details the principles of the maximum entropy spectral estimate and autoregressive (AR) spectral estimate, analyzed the effect of the order number selection on the resultant model. Applying these methods to the periodicity analysis of the quasar 3C 279 and BL Lac object OJ 287, their light periods are obtained to be 7.14 and 11.76 yr, respectively. As is verified by experiments, the AR spectral estimate has a high resolution and is a rather good periodicity analysis method. Finally, the items noteworthy for the application of these spectrum estimation methods to the periodicity analysis of the light variations of blazars are mentioned.

  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. A Multiwavelength Study of Three Hybrid Blazars

    NASA Astrophysics Data System (ADS)

    Stanley, Ethan; Kharb, Preeti; Lister, Matthew L.; Marshall, Herman L.; O'Dea, Christopher; Baum, Stefi

    2017-01-01

    Hybrid active galactic nuclei (AGN) are rare objects that show jet morphology like that of low-power, Fanaroff-Riley Type I (FR-I) AGN on one side of the central black hole and that of high-power, FR-II AGN on the other. As such, they offer an excellent opportunity to study the physical causes of differences between FR-I and FR-II AGN, but so far very few have been well studied. We obtained new Hubble Space Telescope and Chandra X-ray Observatory observations plus archival Very Long Baseline Array (VLBA) and Very Large Array observations of three hybrid AGN to study their spectral energy distributions and model the emission mechanisms of their jets, knots, and hotspots. Based on our parsec-scale VLBA radio observations, these sources have jets that are highly aligned with the line of sight, and the FR-I morphology jet is pointing toward the observer for two of the sources, and the FR-II jet is for the third. Regardless of these alignment differences, all three yielded only optical upper limits on their jet emission, which definitively rules out a single synchrotron emission mechanism for radio through X-ray energies and implies that their emission mechanisms are more similar to FR-II AGN. Additionally, all three sources show high total radio power typical of FR-II AGN. When these 3 AGN are considered alongside the 10 previously well-studied hybrid AGN, a trend emerges that the majority have approaching FR-I morphology jets with FR-II emission mechanisms. In all 13 cases, the X-ray emission is found in the approaching jet. This raises unresolved questions regarding these sources, highlighting the need for additional multifrequency observations of hybrid AGN.

  4. Highlights of the first XMM-Newton observations of OJ 287 and coordinated multiwavelength campaign

    NASA Astrophysics Data System (ADS)

    Ciprini, S.

    2006-10-01

    One of the aims of the European Network for the Investigation of Galactic nuclei through Multifrequency Analysis (ENIGMA) was the organization and implementation of international multiwavelength campaigns, exploiting space-borne and ground-based astrophysical facilities, and the development of blazar multifrequency analysis and modelling. A short summary of a campaign devoted to the peculiar blazar OJ 287 is reported here, as one of the main activity performed during the recruitment of the author in this Research Network. X-ray data obtained during the two proposed XMM-Newton observations of OJ 287 in 2005, showed different brightness states and different spectral slopes and components. The X-ray observation epochs corresponded also to two active and flaring stages at optical wavelengths.

  5. 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.

  6. Blazar flaring patterns (B-FlaP) classifying blazar candidate of uncertain type in the third Fermi-LAT catalogue by artificial neural networks

    NASA Astrophysics Data System (ADS)

    Chiaro, G.; Salvetti, D.; La Mura, G.; Giroletti, M.; Thompson, D. J.; Bastieri, D.

    2016-11-01

    The Fermi-Large Area Telescope (LAT) is currently the most important facility for investigating the GeV γ-ray sky. With Fermi-LAT, more than three thousand γ-ray sources have been discovered so far. 1144 (˜40 per cent) of the sources are active galaxies of the blazar class, and 573 (˜20 per cent) are listed as blazar candidate of uncertain type (BCU), or sources without a conclusive classification. We use the empirical cumulative distribution functions and the artificial neural networks for a fast method of screening and classification for BCUs based on data collected at γ-ray energies only, when rigorous multiwavelength analysis is not available. Based on our method, we classify 342 BCUs as BL Lacs and 154 as flat-spectrum radio quasars, while 77 objects remain uncertain. Moreover, radio analysis and direct observations in ground-based optical observatories are used as counterparts to the statistical classifications to validate the method. This approach is of interest because of the increasing number of unclassified sources in Fermi catalogues and because blazars and in particular their subclass high synchrotron peak objects are the main targets of atmospheric Cherenkov telescopes.

  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. Synchrotron and inverse-Compton emission from blazar jets - III. Compton-dominant blazars

    NASA Astrophysics Data System (ADS)

    Potter, William J.; Cotter, Garret

    2013-05-01

    In this paper, we develop the extended jet model of Potter & Cotter to model the simultaneous multiwavelength spectra of six Compton-dominant blazars. We include an accelerating parabolic base transitioning to a slowly decelerating conical jet with a geometry set by observations of M87 and consistent with simulations and theory. We investigate several jet models and find that the optically thick to thin synchrotron break in the radio spectrum requires the jet to first come into equipartition at large distances along the jet, consistent with the observed transition from parabolic to conical at 105Rs in the jet of M87. We confirm this result analytically and calculate the expected frequency core-shift relations for the models under consideration. We find that a parabolic jet transitioning to a ballistic conical jet at 105Rs, which starts in equipartition and becomes more particle dominated at larger distances, fits the multiwavelength data of the six blazars well, whilst an adiabatic equipartition conical section requires very large bulk Lorentz factors to reproduce the Compton dominance of the blazars. We find that all these blazars require high power (>1039 W), high bulk Lorentz factor (>20) jets observed close to the line of sight (<2°) as we expect from the blazar sequence and consistent with the results from Paper II. The inverse-Compton emission in our fits is due to inverse-Compton scattering of high-redshift cosmic microwave background photons at large distances along the jet due to the high bulk Lorentz factors of the jets. We postulate a new interpretation of the blazar sequence based on the radius of the transition region of the jet (where the jet is brightest in synchrotron emission) scaling linearly with black hole mass.

  9. Multi-wavelength Analysis of a Solar Network Region

    NASA Astrophysics Data System (ADS)

    Tsiropoula, G.; Tziotziou, K.; Schwartz, P.; Heinzel, P.

    We analyse co-temporal observations of a network region found near the solar disc centre, obtained by the Dutch Open Telescope (DOT) and the Coronal Diagnostic Spectrometer (CDS) on-board SOHO during a coordinated observing campaign in October 2005. DOT obtained images in 5 wavelengths along the ha\\ profile, while CDS obtained sit-and-stare observations in several EUV spectral lines that span the upper solar atmosphere. After fitting the CDS spectral line profiles we obtained 2-D space-time maps of intensities, Doppler velocities and Doppler widths. We study the appearance of the network region in the different spectral lines and the temporal variations of the obtained physical parameters. We employ a wavelet analysis to examine the existence of oscillations at the network in the different solar layers.

  10. General physical properties of bright Fermi blazars

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Tavecchio, F.; Foschini, L.; Ghirlanda, G.; Maraschi, L.; Celotti, A.

    2010-02-01

    We studied all blazars of known redshift detected by the Fermi satellite during its first 3-month survey. For the majority of them, pointed Swift observations ensure a good multiwavelength coverage, enabling us to reliably construct their spectral energy distributions (SEDs). We model the SEDs using a one-zone leptonic model and study the distributions of the derived interesting physical parameters as a function of the observed γ-ray luminosity. We confirm previous findings concerning the relation of the physical parameters with source luminosity which are at the origin of the blazar sequence. The SEDs allow to estimate the luminosity of the accretion disc for the majority of broad emitting line blazars, while for the lineless BL Lac objects in the sample upper limits can be derived. We find a positive correlation between the jet power and the luminosity of the accretion disc in broad-line blazars. In these objects, we argue that the jet must be proton dominated, and that the total jet power is of the same order of (or slightly larger than) the disc luminosity. We discuss two alternative scenarios to explain this result.

  11. RXTE Observations of Selected Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Jorstad, Svetlana G.

    2002-01-01

    The work completed includes the analysis of observations obtained during Cycles 4 and 5 of the Rossi X-ray Timing Explorer (RXTE). The project is part of a longer-term, continuing program to study the X-ray emission process in blazars in collaboration with Dr. Ian McHardy (U. of Southampton, UK).

  12. The Spectral Energy Distributions of Fermi Blazars

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Yang, J. H.; Liu, Y.; Luo, G. Y.; Lin, C.; Yuan, Y. H.; Xiao, H. B.; Zhou, A. Y.; Hua, T. X.; Pei, Z. Y.

    2016-10-01

    In this paper, multiwavelength data are compiled for a sample of 1425 Fermi blazars to calculate their spectral energy distributions (SEDs). A parabolic function, {{log}}{(ν {F}ν )={P}1({{log}}ν -{P}2)}2+{P}3, is used for SED fitting. Synchrotron peak frequency ({log}{ν }{{p}}), spectral curvature (P1), peak flux ({ν }{{p}}{F}{ν {{p}}}), and integrated flux (ν {F}ν ) are successfully obtained for 1392 blazars (461 flat-spectrum radio quasars [FSRQs], 620 BL Lacs [BLs], and 311 blazars of uncertain type [BCUs]; 999 sources have known redshifts). Monochromatic luminosity at radio 1.4 GHz, optical R band, X-ray at 1 keV and γ-ray at 1 GeV, peak luminosity, integrated luminosity, and effective spectral indices of radio to optical ({α }{{RO}}) and optical to X-ray ({α }{{OX}}) are calculated. The “Bayesian classification” is employed to log {ν }{{p}} in the rest frame for 999 blazars with available redshift, and the results show that three components are enough to fit the log {ν }{{p}} distribution; there is no ultra-high peaked subclass. Based on the three components, the subclasses of blazars using the acronyms of Abdo et al. are classified, and some mutual correlations are also studied. Conclusions are finally drawn as follows: (1) SEDs are successfully obtained for 1392 blazars. The fitted peak frequencies are compared with common sources from available samples. (2) Blazars are classified as low synchrotron peak sources if log {ν }{{p}}({Hz})≤slant 14.0, intermediate synchrotron peak sources if 14.0\\lt {log} {ν }{{p}}({Hz})≤slant 15.3, and high synchrotron peak sources if {log} {ν }{{p}}({Hz})\\gt 15.3. (3) Gamma-ray emissions are strongly correlated with radio emissions. Gamma-ray luminosity is also correlated with synchrotron peak luminosity and integrated luminosity. (4) There is an anticorrelation between peak frequency and peak luminosity within the whole blazar sample. However, there is a marginally positive correlation for high

  13. [Remote system of natural gas leakage based on multi-wavelength characteristics spectrum analysis].

    PubMed

    Li, Jing; Lu, Xu-Tao; Yang, Ze-Hui

    2014-05-01

    In order to be able to quickly, to a wide range of natural gas pipeline leakage monitoring, the remote detection system for concentration of methane gas was designed based on static Fourier transform interferometer. The system used infrared light, which the center wavelength was calibrated to absorption peaks of methane molecules, to irradiated tested area, and then got the interference fringes by converging collimation system and interference module. Finally, the system calculated the concentration-path-length product in tested area by multi-wavelength characteristics spectrum analysis algorithm, furthermore the inversion of the corresponding concentration of methane. By HITRAN spectrum database, Selected wavelength position of 1. 65 microm as the main characteristic absorption peaks, thereby using 1. 65 pm DFB laser as the light source. In order to improve the detection accuracy and stability without increasing the hardware configuration of the system, solved absorbance ratio by the auxiliary wave-length, and then get concentration-path-length product of measured gas by the method of the calculation proportion of multi-wavelength characteristics. The measurement error from external disturbance is caused by this innovative approach, and it is more similar to a differential measurement. It will eliminate errors in the process of solving the ratio of multi-wavelength characteristics, and can improve accuracy and stability of the system. The infrared absorption spectrum of methane is constant, the ratio of absorbance of any two wavelengths by methane is also constant. The error coefficients produced by the system is the same when it received the same external interference, so the measured noise of the system can be effectively reduced by the ratio method. Experimental tested standards methane gas tank with leaking rate constant. Using the tested data of PN1000 type portable methane detector as the standard data, and were compared to the tested data of the system

  14. 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.

  15. FOURIER ANALYSIS OF BLAZAR VARIABILITY: KLEIN–NISHINA EFFECTS AND THE JET SCATTERING ENVIRONMENT

    SciTech Connect

    Finke, Justin D.; Becker, Peter A. E-mail: pbecker@gmu.edu

    2015-08-10

    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.

  16. Polarization swings reveal magnetic energy dissipation in blazars

    SciTech Connect

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

    2015-05-01

    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.

  17. Polarization swings reveal magnetic energy dissipation in blazars

    DOE PAGES

    Zhang, Haocheng; Chen, Xuhui; Böttcher, Markus; ...

    2015-05-01

    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

  18. POLARIZATION SWINGS REVEAL MAGNETIC ENERGY DISSIPATION IN BLAZARS

    SciTech Connect

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

    2015-05-01

    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 sometimes 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.

  19. Nine years of multi-frequency monitoring of the blazar PKS 0048-097: spectral and temporal variability

    NASA Astrophysics Data System (ADS)

    Wierzcholska, Alicja

    2015-08-01

    Context. Blazars are highly variable, radio-loud active galactic nuclei with jets oriented at a small angle to the line of sight. The observed emission of these sources covers the whole electromagnetic spectrum from radio frequencies up to the high or even very high energy gamma-ray range. To understand the complex physics of these objects, multi-wavelength observations and studies on the variability and correlations between different wavelengths are therefore essential. Aims: The long-term multi-frequency observations of PKS 0048-097 are analysed here to investigate its spectral and temporal features. The studies includes nine years of observations of the blazar, which is well studied in the optical and radio domain, but not in the other frequencies. Methods: Multi-wavelength data collected with OVRO, KAIT, Catalina, Swift/UVOT, Swift/XRT, and Fermi/LAT were studied. Results: The performed analysis revealed strong variability in all wavelengths that is most clearly manifested in the X-ray range. The correlation studies do not exhibit any relation between different wavelengths, except for the very strong positive correlation between the optical emission in V and R bands.

  20. Comparative Analysis of Oscillations of a Solar Quiet Region Using Multi-Wavelength Observations

    NASA Astrophysics Data System (ADS)

    Kontogiannis, I.; Tsiropoula, G.; Tziotziou, K.

    2010-07-01

    We analyze the temporal behavior of a solar quiet region using a set of multi-wavelength observations obtained during a coordinated campaign. The observations were acquired by the ground-based Dutch Open Telescope (DOT), the Michelson Doppler Imager (MDI) on-board SOHO and the UV filters of the Transition Region and Coronal Explorer (TRACE). A large range of height in the solar atmosphere, from the deep photosphere to the upper chromosphere is covered by these instruments. We investigate the oscillation properties of the intensities and velocities in distinct regions of the quiet Sun, i.e. internetwork, bright points (NBP) defining the network boundaries and dark mottles forming a well-defined rosette, as observed by the different instruments and in the different heights. The variations of the intensities and velocities are studied with wavelet analysis. The aim of our work is to find similarities and/or differences in the oscillatory phenomena observed in the different examined regions, as well as comprehensive information on the interaction of the oscillations and the magnetic field.

  1. 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.

  2. Multiwavelength monitoring of active galactic nuclei

    NASA Technical Reports Server (NTRS)

    Urry, C. M.

    1993-01-01

    Recent multiwavelength monitoring of active galactic nuclei (AGN), particularly with the IUE satellite, has produced extraordinay advances in our understanding of the energy-generation mechanism(s) in the central engine and of the structure of the surrounding material. Examples discussed here include both ordinary AGN and blazars (the collective name for highly variable, radio-loud AGN like BL Lac objects and Optically Violently Variable quasars). In the last decade, efforts to obtain single-epoch multiwavelength spectra led to fundamentally new models for the structure of AGN, involving accretion disks for AGN and relativistic jets for blazars. Recent extensions of multiwavelength spectroscopy into the temporal domain have shown that while these general pictures may be correct, the details were probably wrong. Campaigns to monitor Seyfert 1 galaxies like NGC 4151, NGC 5548 and Fairall 9 at infrared, optical, ultraviolet and X-ray wavelengths indicate that broad-emission line regions are stratified by ionization, density, and velocity; argue against a standard thin accretion disk model; and suggest that X-rays represent primary rather than reprocessed radiation. For blazars, years of radio monitoring indicated emission from an inhomogeneous synchrotron-emitting plasma, which could also produce at least some of the shorter-wavelength emission. The recent month-long campaign to observe the BL Lac object PKS 2155-304 has revealed remarkably rapid variability that extends from the infrared through the X-ray with similar amplitude and little or no discernible lag. This lends strong support to relativistic jet models and rules out the proposed accretion disk model for the ultraviolet-X-ray continuum.

  3. RXTE Observations of Selected Blazars

    NASA Technical Reports Server (NTRS)

    Aller, Margo F.

    2002-01-01

    The work completed includes the analysis of observations obtained during Cycles 4 and 5 of the Rossi X-ray Timing Explorer (RXTE). The project is part of a longer-term, continuing program to study the X-ray emission process in blazars in cooperation with Dr. Ian McHardy (U. of Southampton, UK). The goals of the program are to study the X-ray emission mechanism in blazars 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 43 GHz with a resolution of 0.1 milliarcseconds with the Very Long Baseline Array (VLBA), and well-sampled X-ray light curves obtained from a series of approved RXTE programs.

  4. Rapid Variability of Blazar 3C 279 during Flaring States in 2013-2014 with Joint Fermi-LAT, NuSTAR, Swift, and Ground-Based Multiwavelength Observations

    NASA Astrophysics Data System (ADS)

    Hayashida, M.; Nalewajko, K.; Madejski, G. M.; Sikora, M.; Itoh, R.; Ajello, M.; Blandford, R. D.; Buson, S.; Chiang, J.; Fukazawa, Y.; Furniss, A. K.; Urry, C. M.; Hasan, I.; Harrison, F. A.; Alexander, D. M.; Baloković, M.; Barret, D.; Boggs, S. E.; Christensen, F. E.; Craig, W. W.; Forster, K.; Giommi, P.; Grefenstette, B.; Hailey, C.; Hornstrup, A.; Kitaguchi, T.; Koglin, J. E.; Madsen, K. K.; Mao, P. H.; Miyasaka, H.; Mori, K.; Perri, M.; Pivovaroff, M. J.; Puccetti, S.; Rana, V.; Stern, D.; Tagliaferri, G.; Westergaard, N. J.; Zhang, W. W.; Zoglauer, A.; Gurwell, M. A.; Uemura, M.; Akitaya, H.; Kawabata, K. S.; Kawaguchi, K.; Kanda, Y.; Moritani, Y.; Takaki, K.; Ui, T.; Yoshida, M.; Agarwal, A.; Gupta, A. C.

    2015-07-01

    We report the results of a multiband observing campaign on the famous blazar 3C 279 conducted during a phase of increased activity from 2013 December to 2014 April, including first observations of it with NuSTAR. The γ-ray emission of the source measured by Fermi-LAT showed multiple distinct flares reaching the highest flux level measured in this object since the beginning of the Fermi mission, with F(E\\gt 100 {MeV}) of 10-5 photons cm-2 s-1, and with a flux-doubling time scale as short as 2 hr. The γ-ray spectrum during one of the flares was very hard, with an index of {{{Γ }}}γ =1.7+/- 0.1, which is rarely seen in flat-spectrum radio quasars. The lack of concurrent optical variability implies a very high Compton dominance parameter {L}γ /{L}{syn}\\gt 300. Two 1 day NuSTAR observations with accompanying Swift pointings were separated by 2 weeks, probing different levels of source activity. While the 0.5-70 keV X-ray spectrum obtained during the first pointing, and fitted jointly with Swift-XRT is well-described by a simple power law, the second joint observation showed an unusual spectral structure: the spectrum softens by {{Δ }}{{{Γ }}}{{X}}≃ 0.4 at ˜4 keV. Modeling the broadband spectral energy distribution during this flare with the standard synchrotron plus inverse-Compton model requires: (1) the location of the γ-ray emitting region is comparable with the broad-line region radius, (2) a very hard electron energy distribution index p≃ 1, (3) total jet power significantly exceeding the accretion-disk luminosity {L}j/{L}d≳ 10, and (4) extremely low jet magnetization with {L}B/{L}j≲ {10}-4. We also find that single-zone models that match the observed γ-ray and optical spectra cannot satisfactorily explain the production of X-ray emission.

  5. 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...

  6. Synchrotron emission from the blazar PG 1553+113. An analysis of its flux and polarization variability

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Nicastro, F.; Stamerra, A.; Villata, M.; Larionov, V. M.; Blinov, D.; Acosta-Pulido, J. A.; Arévalo, M. J.; Arkharov, A. A.; Bachev, R.; Borman, G. A.; Carnerero, M. I.; Carosati, D.; Cecconi, M.; Chen, W.-P.; Damljanovic, G.; Di Paola, A.; Ehgamberdiev, Sh. A.; Frasca, A.; Giroletti, M.; González-Morales, P. A.; Griñon-Marín, A. B.; Grishina, T. S.; Huang, P.-C.; Ibryamov, S.; Klimanov, S. A.; Kopatskaya, E. N.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Larionova, E. G.; Larionova, L. V.; Lázaro, C.; Leto, G.; Liodakis, I.; Martínez-Lombilla, C.; Mihov, B.; Mirzaqulov, D. O.; Mokrushina, A. A.; Moody, J. W.; Morozova, D. A.; Nazarov, S. V.; Nikolashvili, M. G.; Ohlert, J. M.; Panopoulou, G. V.; Pastor Yabar, A.; Pinna, F.; Protasio, C.; Rizzi, N.; Sadun, A. C.; Savchenko, S. S.; Semkov, E.; Sigua, L. A.; Slavcheva-Mihova, L.; Strigachev, A.; Tornikoski, M.; Troitskaya, Yu. V.; Troitsky, I. S.; Vasilyev, A. A.; Vera, R. J. C.; Vince, O.; Zanmar Sanchez, R.

    2017-04-01

    In 2015 July 29-September 1, the satellite XMM-Newton pointed at the BL Lac object PG 1553+133 six times, collecting data for 218 h. During one of these epochs, simultaneous observations by the Swift satellite were requested to compare the results of the X-ray and optical-UV instruments. Optical, near-infrared and radio monitoring was carried out by the Whole Earth Blazar Telescope (WEBT) collaboration for the whole observing season. We here present the results of the analysis of all these data, together with an investigation of the source photometric and polarimetric behaviour over the last 3 yr. The 2015 EPIC spectra show slight curvature and the corresponding light curves display fast X-ray variability with a time-scale of the order of 1 h. In contrast to previous results, during the brightest X-ray states detected in 2015 the simple log-parabolic model that best fits the XMM-Newton data also reproduces reasonably well the whole synchrotron bump, suggesting a peak in the near-UV band. We found evidence of a wide rotation of the polarization angle in 2014, when the polarization degree was variable, but the flux remained almost constant. This is difficult to interpret with deterministic jet emission models, while it can be easily reproduced by assuming some turbulence of the magnetic field.

  7. 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.

  8. High redshift blazars .

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.

    Blazars are sources whose jet is pointing at us. Since their jets are relativistic, the flux is greatly amplified in the direction of motion, making blazars the most powerful persistent objects in the Universe. This is true at all frequencies, but especially where their spectrum peaks. Although the spectrum of moderate powerful sources peaks in the ˜GeV range, extremely powerful sources at high redshifts peak in the ˜MeV band. This implies that the hard X-ray band is the optimal one to find powerful blazars beyond a redshift of ˜4. First indications strongly suggest that powerful high-z blazars harbor the most massive and active early black holes, exceeding a billion solar masses. Since for each detected blazars there must exist hundreds of similar, but misaligned, sources, the search for high-z blazars is becoming competitive with the search of early massive black holes using radio-quiet quasars. Finding how the two populations of black holes (one in jetted sources, the other in radio-quiet objects) evolve in redshift will shed light on the growth of the most massive black holes and possibly on the feedback between the central engine and the rest of the host galaxy.

  9. 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.

  10. Intrinsic Correlations for Flaring Blazars Detected by Fermi

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Yang, J. H.; Xiao, H. B.; Lin, C.; Constantin, D.; Luo, G. Y.; Pei, Z. Y.; Hao, J. M.; Mao, Y. W.

    2017-02-01

    Blazars are an extreme subclass of active galactic nuclei. Their rapid variability, luminous brightness, superluminal motion, and high and variable polarization are probably due to a beaming effect. However, this beaming factor (or Doppler factor) is very difficult to measure. Currently, a good way to estimate it is to use the timescale of their radio flares. In this Letter, we use multiwavelength data and Doppler factors reported in the literature for a sample of 86 flaring blazars detected by Fermi to compute their intrinsic multiwavelength data and intrinsic spectral energy distributions and investigate the correlations among observed and intrinsic data. Quite interestingly, intrinsic data show a positive correlation between luminosity and peak frequency, in contrast with the behavior of observed data, and a tighter correlation between γ-ray luminosity and the lower-energy ones. For flaring blazars detected by Fermi, we conclude that (1) observed emissions are strongly beamed; (2) the anti-correlation between luminosity and peak frequency from the observed data is an apparent result, the correlation between intrinsic data being positive; and (3) intrinsic γ-ray luminosity is strongly correlated with other intrinsic luminosities.

  11. 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.

  12. Multiwavelength Cosmology

    NASA Astrophysics Data System (ADS)

    Plionis, M.

    2004-07-01

    The recent scientific efforts in Astrophysics & Cosmology have brought a revolution to our understanding of the Cosmos. Amazing results is the outcome of amazing experiments! The huge scientific, technological & financial effort that has gone into building the 10-m class telescopes as well as many space and balloon observatories, essential to observe the multitude of cosmic phenomena in their manifestations at different wavelengths, from gamma-rays to the millimetre and the radio, has given and is still giving its fruits of knowledge. These recent scientific achievements in Observational and Theoretical Cosmology were presented in the "Multiwavelength Cosmology" conference that took place on beautiful Mykonos island in the Aegean between 17 and 20 June 2003. More than 180 Cosmologists from all over the world gathered for a four-day intense meeting in which recent results from large ground based surveys (AAT/2-df, SLOAN) and space missions (WMAP, Chandra, XMM, ISO, HST) were presented and debated, providing a huge impetus to our knowledge of the Cosmos. The future of the subject (experiments, and directions of research) was also discussed. The conference was devoted mostly on the constraints on Cosmological models and galaxy formation theories that arise from the study of the high redshift Universe, from clusters of galaxies, and their evolution, from the cosmic microwave background, the large-scale structure and star-formation history. Link: A Radiative Transport Model for Blazars

    NASA Astrophysics Data System (ADS)

    Lewis, Tiffany; Justin, Finke; Becker, Peter A.

    2017-01-01

    Blazars are observed across the electromagnetic spectrum, often with strong variability throughout. The underlying electron distribution associated with the observed emission is typically not computed from first principles. We start from first-principles to build up a transport model, whose solution is the electron distribution, rather than assuming a convenient functional form. Our analytical transport model considers shock acceleration, adiabatic expansion, stochastic acceleration, Bohm diffusion, and synchrotron radiation. We use this solution to generate predictions for the X-ray spectrum and time lags, and compare the results with data products from BeppoSAX observations of X-ray flares from Mrk 421. This new self-consistent model provides an unprecedented view into the jet physics at play in this source, especially the strength of the shock and stochastic acceleration components and the size of the acceleration region.More recently, we augmented the transport model to incorporate Compton scattering, including Klein-Nishina effects. In this case, an analytical solution cannot be derived, and therefore we obtain the steady-state electron distribution computationally. We compare the resulting radiation spectrum with multi-wavelength data for 3C 279. We show that our new Compton + synchrotron blazar model is the first to successfully fit the FermiLAT gamma-ray data for this source based on a first-principles physical calculation.

  13. A Radiative Transport Model for Blazars

    NASA Astrophysics Data System (ADS)

    Lewis, Tiffany; Finke, Justin; Becker, Peter

    2017-01-01

    Blazars are observed across the electromagnetic spectrum, often with strong variability throughout. We start from first-principles to build up a transport model, whose solution is the electron distribution, rather than assuming a convenient functional form. Our analytical transport model considers shock acceleration, adiabatic expansion, stochastic acceleration, Bohm diffusion, and synchrotron radiation. We use this solution to give predictions for the X-ray spectrum and time lags, comparing the results with BeppoSAX observations of X-ray flares from Mrk 421. This new self-consistent model provides an unprecedented view into the jet physics at play in this source, especially the strength of the shock and stochastic acceleration components and the size of the acceleration region. More recently, we augmented the transport model to incorporate Compton scattering, including Klein-Nishina effects. Here, an analytical solution cannot be derived. Therefore we obtain the steady-state electron distribution computationally. We compare the resulting radiation spectrum with multi-wavelength data for 3C 279. We show that our new Compton + synchrotron blazar model is the first to successfully fit the FermiLAT gamma-ray data for this source based on a first-principles physical calculation.

  14. 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.

  15. What Drives Star Formation in Galaxies?: A Multiwavelength Analysis of Infrared Galaxies

    NASA Astrophysics Data System (ADS)

    Kartaltepe, Jeyhan

    the star formation rate density at this key epoch of star formation and AGN activity and therefore, understanding the origin of these extreme luminosities is fundamental to our understanding of the relative role of several important processes in galaxy evolution. Morphological studies of local (U)LIRGs have shown unambiguously that a galaxy's infrared luminosity is correlated with the presence of galaxy mergers and interactions as well as with the stage that these mergers are in (e.g., Veilleux et al. 2002). However, the role of mergers and interactions at higher redshifts, where these populations dominate, is not yet well constrained. We will put strong constraints on this role at high redshift for the first time by constructing and analyzing a large comprehensive sample of (U)LIRGs at 0multiwavelength data set, to investigate the AGN activity. Spectroscopic data, from the HST grism as well as from several ground-based datasets, will enable us to measure redshifts, study galaxy kinematics, identify galaxy pairs, and probe several AGN diagnostics. By combining these key data sets, we will be able to quantify the role of galaxy mergers and interactions to the cosmic SFR and AGN activity. This work will involve a detailed morphological analysis (including visual classifications as well as several automated statistical techniques), a comparison of multiple SFR measures, a stacking analysis of the Herschel and X-ray data, and spectral analysis of HST-grism observations.

  16. 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

  17. 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.

  18. OSSE Observations of Blazars

    DTIC Science & Technology

    1994-01-01

    directly down a relativistically out owing jet of matter expelled from a supermassive black hole . Many of the current theoretical interpretations of...these results indicate that the gamma rays are associated with jet activity near a supermassive back hole , but the origin of the gamma radia- tion is...standard model for blazar sources involves a black - hole accretion disk with colli- mated jets that are oriented at nearly right angles to the plane of

  19. 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.

  1. 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.

  2. Cobinamide-based cyanide analysis by multiwavelength spectrometry in a liquid core waveguide.

    PubMed

    Ma, Jian; Dasgupta, Purnendu K; Blackledge, William; Boss, Gerry R

    2010-07-15

    A novel cyanide analyzer based on sensitive cobinamide chemistry relies on simultaneous reagent and sample injection and detection in a 50 cm liquid core waveguide (LCW) flow cell illuminated by a white light emitting diode. The transmitted light is read by a fiber-optic charge coupled device (CCD) spectrometer. Alkaline cobinamide (orange, lambda(max) = 510 nm) changes to violet (lambda(max) = 583 nm) upon reaction with cyanide. Multiwavelength detection permits built-in correction for artifact responses intrinsic to a single-line flow injection system and corrects for drift. With optimum choice of the reaction medium, flow rate, and mixing coil length, the limit of detection (LOD, S/N = 3) is 30 nM and the linear dynamic range extends to 10 microM. The response base width for 1% carryover is <95 s, permitting a throughput of 38 samples/h. The relative standard deviations (rsd) for repetitive determinations at 0.15, 0.5, and 1 microM were 7.6% (n = 5), 3.2% (n = 7), and 1.7% (n = 6), respectively. Common ions at 250-80,000x concentrations do not interfere except for sulfide. For the determination of 2 microM CN(-), the presence of 2, 5, 10, 20, 100, and 1000 microM HS(-) results in 22, 27, 48, 58, 88, and 154% overestimation of cyanide. The sulfide product actually has a different characteristic absorption, and in those samples where significant presence is likely, this can be corrected for. We demonstrate applicability by analyzing the hydrolytic cyanide extract of apple and pear seeds with orange seeds as control and also measure HCN in breath air samples. Spike recoveries in these sample extracts ranged from 91 to 108%.

  3. Cobinamide-Based Cyanide Analysis by Multiwavelength Spectrometry in a Liquid Core Waveguide

    PubMed Central

    Ma, Jian; Dasgupta, Purnendu K.; Blackledge, William; Boss, Gerry R.

    2010-01-01

    A novel cyanide analyzer based on sensitive cobinamide chemistry relies on simultaneous reagent and sample injection and detection in a 50 cm liquid core waveguide (LCW) flow cell illuminated by a white light emitting diode. The transmitted light is read by a fiber-optic charge coupled device (CCD) spectrometer. Alkaline cobinamide (orange, λmax = 510 nm) changes to violet (λmax = 583 nm) upon reaction with cyanide. Multiwavelength detection permits built-in correction for artifact responses intrinsic to a single-line flow injection system and corrects for drift. With optimum choice of the reaction medium, flow rate, and mixing coil length, the limit of detection (LOD, S/N = 3) is 30 nM and the linear dynamic range extends to 10 μM. The response base width for 1% carryover is <95 s, permitting a throughput of 38 samples/h. The relative standard deviations (rsd) for repetitive determinations at 0.15, 0.5, and 1 μM were 7.6% (n = 5), 3.2% (n = 7), and 1.7% (n = 6), respectively. Common ions at 250–80 000× concentrations do not interfere except for sulfide. For the determination of 2 μM CN−, the presence of 2, 5, 10, 20, 100, and 1000 μM HS− results in 22, 27, 48, 58, 88, and 154% overestimation of cyanide. The sulfide product actually has a different characteristic absorption, and in those samples where significant presence is likely, this can be corrected for. We demonstrate applicability by analyzing the hydrolytic cyanide extract of apple and pear seeds with orange seeds as control and also measure HCN in breath air samples. Spike recoveries in these sample extracts ranged from 91 to 108%. PMID:20560532

  4. 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

  5. Quantified H I morphology - I. Multi-wavelength analysis of the THINGS galaxies

    NASA Astrophysics Data System (ADS)

    Holwerda, B. W.; Pirzkal, N.; de Blok, W. J. G.; Bouchard, A.; Blyth, S.-L.; van der Heyden, K. J.; Elson, E. C.

    2011-10-01

    Galaxy evolution is driven to a large extent by interactions and mergers with other galaxies and the gas in galaxies is extremely sensitive to the interactions. One method to measure such interactions uses the quantified morphology of galaxy images. Well-established parameters are Concentration, Asymmetry, Smoothness, Gini and M20 of a galaxy image. Thus far, the application of this technique has mostly been restricted to rest-frame ultraviolet and optical images. However, with the new radio observatories being commissioned [South African Karoo Array Telescope (MeerKAT), Australian SKA Pathfinder (ASKAP), Extended Very Large Array (EVLA), Westerbork Synthesis Radio Telescope/APERture Tile In Focus instrument (WSRT/APERTIF) and ultimately the Square Kilometer Array (SKA)], a new window on the neutral atomic hydrogen gas (H I) morphology of large numbers of galaxies will open up. The quantified morphology of gas discs of spirals can be an alternative indicator of the level and frequency of interaction. The H I in galaxies is typically spatially more extended and more sensitive to low-mass or weak interactions. In this paper, we explore six morphological parameters calculated over the extent of the stellar (optical) disc and the extent of the gas disc for a range of wavelengths spanning ultraviolet (UV), optical, near- and far-infrared and 21 cm (H I) of 28 galaxies from The H I Nearby Galaxy Survey (THINGS). Although the THINGS sample is small and contains only a single ongoing interaction, it spans both non-interacting and post-interacting galaxies with a wealth of multi-wavelength data. We find that the choice of area for the computation of the morphological parameters is less of an issue than the wavelength at which they are measured. The signal of interaction is as good in the H I as at any of the other wavelengths at which morphology has been used to trace the interaction rate to date, mostly star formation dominated ones (near- and far-ultraviolet). The

  6. Probing acceleration and turbulence at relativistic shocks in blazar jets

    NASA Astrophysics Data System (ADS)

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

    2017-02-01

    Diffusive shock acceleration (DSA) at relativistic shocks is widely thought to be an important acceleration mechanism in various astrophysical jet sources, including radio-loud active galactic nuclei such as blazars. Such acceleration can produce the non-thermal particles that emit the broad-band continuum radiation that is detected from extragalactic jets. An important recent development for blazar science is the ability of Fermi-Large Area Telescope spectroscopy to pin down the shape of the distribution of the underlying non-thermal particle population. This paper highlights how multiwavelength spectra spanning optical to X-ray to gamma-ray bands can be used to probe diffusive acceleration in relativistic, oblique, magnetohydrodynamic (MHD) shocks in blazar jets. Diagnostics on the MHD turbulence near such shocks are obtained using thermal and non-thermal particle distributions resulting from detailed Monte Carlo simulations of DSA. These probes are afforded by the characteristic property that the synchrotron νFν peak energy does not appear in the gamma-ray band above 100 MeV. We investigate self-consistently the radiative synchrotron and inverse Compton signatures of the simulated particle distributions. Important constraints on the diffusive mean free paths of electrons, and the level of electromagnetic field turbulence are identified for three different case study blazars, Mrk 501, BL Lacertae and AO 0235+164. The X-ray excess of AO 0235+164 in a flare state can be modelled as the signature of bulk Compton scattering of external radiation fields, thereby tightly constraining the energy-dependence of the diffusion coefficient for electrons. The concomitant interpretations that turbulence levels decline with remoteness from jet shocks, and the probable significant role for non-gyroresonant diffusion, are posited.

  7. 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

  8. 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.

  9. Multiwavelength Luminosity Functions of Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan; Oegerle, William R. (Technical Monitor)

    2002-01-01

    I have developed a technique for measuring multi-variate luminosity functions of galaxies. Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and absorption and re-emission of dust within evolving galaxy populations. By using principle component analysis to reduce the dimensionality of the problem, I optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, I derive the multiwavelength luminosity function for the galaxies in the released SDSS catalog, and show that the results are consistent with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by the SIRTF and GALEX missions.

  10. 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.

  11. Optical polarization of gamma-ray bright blazars

    NASA Astrophysics Data System (ADS)

    Blinov, Dmitry; Angelakis, E.; Balokovic, M.; Fuhrmann, L.; Hovatta, T.; Katarzyski, K.; Khodade, P.; King, O.; Kus, A.; Kylafis, N.; Myserlis, I.; Panopoulou, G.; Papadakis, I.; Papamastorakis, I.; Pavlidou, V.; Pazderska, B.; Pazderski, E.; Pearson, T.; Rajarshi, C.; Ramaprakash, A.; Readhead, A.; Reig, P.; Rouneq, R.; Tassis, K.; Zensus, A.

    2014-07-01

    We report about first results of the RoboPol project. RoboPol is a large-sample, high-cadence, polarimetric monitoring program of blazars in optical wavelengths, using a camera specifically constructed for this project, mounted at the University of Crete's Skinakas Observatory 1.3 m telescope. The analysis of RoboPol data is conducted in conjunction with Fermi LAT gamma-ray data, and multifrequency radio data from the OVRO (Caltech), F-GAMMA (MPIfR), and Torun (NCU) monitoring programs. Using carefully selected samples of gamma-ray bright and weak blazars we investigate a connection between their optical polarization behaviour and variability properties in gamma. We examine a relationship of gamma flares with polarization angle rotations relying on robust statistical criteria. We analyse also the optical polarization variability itself in order to establish some restrictions on physical models of blazars jets.

  12. Observations of variability of TeV gamma-ray blazars

    NASA Astrophysics Data System (ADS)

    Feng, Qi

    The boom in ground-based gamma-ray astronomy since the beginning of the 21st century has enabled a new probe of the universe using very-high-energy photons. The Very Energetic Radiation Imaging Telescope Array System (VERITAS) is an array of four 12-m imaging Cherenkov telescopes that is sensitive to gamma rays in the energy range between ~100 GeV and ~30 TeV. Among all known TeV sources, blazars, a particular type of active galactic nuclei, have shown exceptional variabilities over a wide range of timescales and energies. The observations of such variabilities have been previously limited at lower energies, ranging from radio to X-ray. However, the superior sensitivity of VERITAS has made the detection of fast TeV gamma-ray variability of blazars possible. The studies of their gamma-ray variability can, in a relatively model-independent way, shed significant light on the emitting regions and production mechanisms in blazars. This thesis describes my work on blazar variability, based primarily on the VERITAS observations but are interpreted in a multi-wavelength context. One of the most exceptional phenomena observed in blazars with VERITAS is the fast variability of the TeV gamma rays. The short duration of these flares strongly constrains the size of the emitting region, and provides insights to the kinetics and location of the emitting region. We describe the fast TeV flare of BL Lacertae as an example, and discuss the connection between TeV flares and multi-wavelength observations that may help localize the TeV emitting region. To study the persistent variability of TeV blazars, we examine a variety of statistical properties in the time and frequency domains. We study both local properties of time series, e.g. time lags between different energy bands and spectral hysteresis during flares, and global properties, e.g. variability amplitude and power spectrum. These properties are connected to the physical processes in blazars, although they are also limited by

  13. Two new high-energy γ-ray blazar candidates

    NASA Astrophysics Data System (ADS)

    Campana, R.; Maselli, A.; Bernieri, E.; Massaro, E.

    2017-03-01

    We report the detection of two new γ-ray sources in the Fermi-Large Area Telescope sky (Pass 8) at energies higher than 20 GeV and confirmed at lower energies, using a source detection tool based on the Minimum Spanning Tree algorithm. One of these sources, at a Galactic latitude of about -4°, is a new discovery, while the other was previously reported above 50 GeV in the 2FHL catalogue. We searched for archival multiwavelength data of possible counterparts and found interesting candidates. Both objects are radio sources and their Wide-field Infrared Survey Explorer infrared colours are typical of blazars. While, for the former source, no optical spectra are available, for the latter, a puzzling optical spectrum corresponding to a white dwarf star is found in the 6dF data base. We discuss the spectral energy distributions of both sources and possible interpretations.

  14. 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...

  15. CMOS buried quad p-n junction photodetector for multi-wavelength analysis.

    PubMed

    Richard, Charles; Courcier, Thierry; Pittet, Patrick; Martel, Stéphane; Ouellet, Luc; Lu, Guo-Neng; Aimez, Vincent; Charette, Paul G

    2012-01-30

    This paper presents a buried quad p-n junction (BQJ) photodetector fabricated with a HV (high-voltage) CMOS process. Multiple buried junction photodetectors are wavelength-sensitive devices developed for spectral analysis applications where a compact integrated solution is preferred over systems involving bulk optics or a spectrometer due to physical size limitations. The BQJ device presented here is designed for chip-based biochemical analyses using simultaneous fluorescence labeling of multiple analytes such as with advanced labs-on-chip or miniaturized photonics-based biosensors. Modeling and experimental measurements of the spectral response of the device are presented. A matrix-based method for estimating individual spectral components in a compound spectrum is described. The device and analysis method are validated via a test setup using individually modulated LEDs to simulate light from 4-component fluorescence emission.

  16. High-redshift Fermi blazars

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Tagliaferri, G.; Foschini, L.; Ghirlanda, G.; Tavecchio, F.; Della Ceca, R.; Haardt, F.; Volonteri, M.; Gehrels, N.

    2011-02-01

    With the release of the first-year Fermi catalogue, the number of blazars detected above 100 MeV lying at high redshift has been largely increased. There are 28 blazars at z > 2 in the `clean' sample. All of them are flat spectrum radio quasars. We study and model their overall spectral energy distribution in order to find the physical parameters of the jet-emitting region, and for all of them, we estimate their black hole masses and accretion rates. We then compare the jet with the accretion disc properties, setting these sources in the broader context of all the other bright γ-ray or hard X-ray blazars. We confirm that the jet power correlates with the accretion luminosity. We find that the high-energy emission peak shifts to smaller frequencies as the observed luminosity increases, according to the blazar sequence, making the hard X-ray band the most suitable for searching the most-luminous and distant blazars.

  17. Multi-wavelength analysis of supernova remnant MSH11-61A.

    NASA Astrophysics Data System (ADS)

    Auchettl, Katie; Slane, Patrick; Castro, Daniel

    MSH11-61A (G290.1-0.8) has been identified as a mixed morphology supernova remnant (SNR) from its centrally bright X-ray morphology and limb brightened radio profile. The evolutionary sequence which leads to these unusual X-ray properties is not well understood and currently different models can only explain some of the features seen in individual cases. In this analysis we present a study of MSH 11-61A using archival Suzaku data. Our preliminary results indicate enhanced abundances, as previously suggested by ASCA observations and we derive the associated age, energy and ambient density conditions of the remnant using models that we constructed in an attempt to reproduce the observed X-ray properties. Observational evidence from thermal and non-thermal emission of SNRs has provided increasing support in favour of cosmic rays being accelerated at the shock front of the remnant. Whether the observed gamma-ray emission from these accelerated CRs is hadronic or leptonic in nature is currently a hotly debated topic in the literature. SNRs known to be interacting with molecular clouds provide effective targets for detecting and studying gamma-rays. As MSH11-61A is thought to be interacting with a molecular cloud towards the south west of the remnant, we perform a spatial and spectral analysis of the gamma-ray emission in the region of this remnant by using ~64 months of data from the Fermi-LAT telescope. This analysis allows us to constrain the origin of the detected gamma-ray emission.

  18. Multi-wavelength Spectral Analysis of Ellerman Bombs Observed by FISS and IRIS

    NASA Astrophysics Data System (ADS)

    Hong, Jie; Ding, M. D.; Cao, Wenda

    2017-04-01

    Ellerman bombs (EBs) are a kind of solar activity that is suggested to occur in the lower solar atmosphere. Recent observations using the Interface Region Imaging Spectrograph (IRIS) show connections between EBs and IRIS bombs (IBs), which imply that EBs might be heated to a much higher temperature (8 × 104 K) than previous results. Here we perform a spectral analysis of EBs simultaneously observed by the Fast Imaging Solar Spectrograph and IRIS. The observational results show clear evidence of heating in the lower atmosphere, indicated by the wing enhancement in Hα, Ca ii 8542 Å, and Mg ii triplet lines and also by brightenings in images of the 1700 Å and 2832 Å ultraviolet continuum channels. Additionally, the intensity of the Mg ii triplet line is correlated with that of Hα when an EB occurs, suggesting the possibility of using the triplet as an alternative way to identify EBs. However, we do not find any signal in IRIS hotter lines (C ii and Si iv). For further analysis, we employ a two-cloud model to fit the two chromospheric lines (Hα and Ca ii 8542 Å) simultaneously, and obtain a temperature enhancement of 2300 K for a strong EB. This temperature is among the highest of previous modeling results, albeit still insufficient to produce IB signatures at ultraviolet wavelengths.

  19. Very High Energy gamma-rays from blazars

    NASA Astrophysics Data System (ADS)

    Sol, Helene

    2014-07-01

    The extragalactic very high energy (VHE) gamma-ray sky is dominated at the moment by more than fifty blazars detected by the present imaging atmospheric Cherenkov telescopes (IACT), with a majority (about 90%) of high-frequency peaked BL Lac objects (HBL) and a small number of low-frequency peaked and intermediate BL Lac objects (LBL and IBL) and flat spectrum radio quasars (FSRQ). A significant variability is often observed, with time scales from a few minutes to months and years. The spectral energy distribution (SED) of these blazars typically shows two bumps from the radio to the TeV range, which can usually be described by leptonic or hadronic processes. While elementary bricks of the VHE emission scenarios seem now reasonably well identified, a global picture of these sources, describing the geometry and dynamics of the VHE zone, is not yet available. Multiwavelength monitoring and global alert network will be important to better constrain the picture, especially with the perspective of CTA, a major project of the next generation in ground-based gamma-ray astronomy.

  20. Multi-wavelength analysis of a 2011 stellar occultation by Chiron

    NASA Astrophysics Data System (ADS)

    Sickafoose, Amanda A.; Emery, Joshua P.; Bosh, Amanda S.; Person, Michael J.; Zuluaga, Carlos; Ruprecht, Jessica D.; Bianco, Federica; Bus, Schelte J.; Zangari, Amanda Marie

    2016-10-01

    The centaur (2060) Chiron was originally thought to be asteroid-like; however, photometry in the late 1980s revealed an increase in brightness and eventually a directly-imaged coma (e.g. Meech, K.J., & Belton, M.J.S., 1990, AJ, 100,4). Previous stellar occultation observations for Chiron have detected features thought to be narrow jets, a gravitationally-bound dust coma, and a near-circular ring or shell of material (Elliot, J.L., 1995, Nature, 373, 46; Bus, S.J., et al., 1996, Icarus, 123, 478; Ruprecht, J.D., et al. 2015, Icarus, 252, 271). These detections are unusual given Chiron's relatively large distance from the Sun and its relatively large nucleus compared to comet nuclei. The discovery of a ring system around the centaur Chariklo (Braga-Ribas, F., et al. 2014, Nature, 508, 78) provides context for Chiron. A ring system for Chiron has recently been proposed based on a combined analysis of occultation data, the rotational light curve, and spectral variability (Ortiz, J.L., et al. 2015, A&A, 576, A18).Chiron occulted a fairly bright star (R = 14.8) on 2011 November 29. We observed the event with high-speed, visible imaging from NASA's 3-m Infrared Telescope Facility (IRTF) on Mauna Kea and the 2-m Faulkes Telescope North at Haleakala (run by the Las Cumbres Observatory Global Telescope network, LCOGT). At the IRTF, we simultaneously obtained low-resolution, near-infrared spectra spanning 0.9-2.4 microns. Here, we present an analysis of the combined visible and near-infrared occultation data. Distinct extinction features were detected in the visible data, located roughly 300 km from the center (Ruprecht, J.D., et al. 2015, Icarus, 252, 271). We investigate flux versus wavelength trends in the near-infrared data in order to constrain the properties of extinction-causing particles.

  1. 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

  2. Optical and near infrared observations of the blazar 3C 279 with the REM telescope.

    NASA Astrophysics Data System (ADS)

    Impiombato, D.; Tosti, G.; Ciprini, C.; REM Collaboration.

    The Rapid Eye Mount (REM) telescope installed at La Silla (Cile) on June 2003, is a robotic telescope able the capability to observe in optical and infrared bands. Since the late commissioning phase a optical and infrared monitoring program of a sample of blazars, most emitting also in the gamma-ray band, was started. Such program is still on going and it make part of an observational activity aimed to the multiwavelength characterization possible blazars candidate to be observed also in gamma-ray by the instruments on board of AGILE satellites(launched on 23 April 2007) and Glast (that will be launched at the end of the 2007). In this poster we present the optical/near-IR data obtained during the January 2007, outburst of 3C279 (the prototype of the gamma-ray loud).

  3. Study of Multi-Band Flux/spectral Variations in the Blazar Markarian 421

    NASA Astrophysics Data System (ADS)

    Paneque, David

    We are organizing a 1 year long campaign with dense multi-frequency (from radio to TeV) coverage on the nearby TeV blazar Markarian 421 (Mrk421). This data set will allow us to study flux/spectral variations over short and long timescales with unprecedented sensitivity, hence improving our knowledge on the physical processes occurring in Mrk421, and blazars in general. The coverage of the source is already granted at various energy ranges through various instruments/programs (OVRO, GASP, GAMMA, Fermi, MAGIC...). RXTE observations would play a uniquely important role in this multi-wavelength campaign by providing high quality and simultaneous (to ground observatories) X-ray data. For this campaign, we request 276 ks with RXTE, which will be split in 184 individual observations of 1.5 ks.

  4. Multi-wavelength Analysis of the Galactic Supernova Remnant MSH 11-61A

    NASA Astrophysics Data System (ADS)

    Auchettl, Katie; Slane, Patrick; Castro, Daniel; Foster, Adam R.; Smith, Randall K.

    2015-09-01

    Due to its centrally bright X-ray morphology and limb brightened radio profile, MSH 11-61A (G290.1-0.8) is classified as a mixed morphology supernova remnant (SNR). H i and CO observations determined that the SNR is interacting with molecular clouds found toward the north and southwest regions of the remnant. In this paper we report on the detection of γ-ray emission coincident with MSH 11-61A, using 70 months of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. To investigate the origin of this emission, we perform broadband modeling of its non-thermal emission considering both leptonic and hadronic cases and concluding that the γ-ray emission is most likely hadronic in nature. Additionally we present our analysis of a 111 ks archival Suzaku observation of this remnant. Our investigation shows that the X-ray emission from MSH 11-61A arises from shock-heated ejecta with the bulk of the X-ray emission arising from a recombining plasma, while the emission toward the east arises from an ionizing plasma.

  5. MULTI-WAVELENGTH ANALYSIS OF THE GALACTIC SUPERNOVA REMNANT MSH 11-61A

    SciTech Connect

    Auchettl, Katie; Slane, Patrick; Foster, Adam R.; Smith, Randall K.; Castro, Daniel

    2015-09-01

    Due to its centrally bright X-ray morphology and limb brightened radio profile, MSH 11–61A (G290.1–0.8) is classified as a mixed morphology supernova remnant (SNR). H i and CO observations determined that the SNR is interacting with molecular clouds found toward the north and southwest regions of the remnant. In this paper we report on the detection of γ-ray emission coincident with MSH 11–61A, using 70 months of data from the Large Area Telescope on board the Fermi Gamma-ray Space Telescope. To investigate the origin of this emission, we perform broadband modeling of its non-thermal emission considering both leptonic and hadronic cases and concluding that the γ-ray emission is most likely hadronic in nature. Additionally we present our analysis of a 111 ks archival Suzaku observation of this remnant. Our investigation shows that the X-ray emission from MSH 11–61A arises from shock-heated ejecta with the bulk of the X-ray emission arising from a recombining plasma, while the emission toward the east arises from an ionizing plasma.

  6. 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.

  7. 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.

  8. Multi-wavelength Luminosity Functions of Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, J. P.; Miller, N. A.

    2002-01-01

    Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and absorption and re-emission of dust within evolving galaxy populations. By using principal component analysis to reduce the dimensionality of the problem, we optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, we derive the multi-wavelength luminosity function for the galaxies in the released SDSS catalog, and compare the results with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by 2MASS, and the SIRTF and GALEX missions.

  9. Multi-Wavelength Luminosity Functions of Galaxies

    NASA Technical Reports Server (NTRS)

    Gardner, Jonathan P.

    2002-01-01

    Multivariate or multi-wavelength luminosity functions will reveal the interplay between star formation, chemical evolution, and ab- sorption and re-emission of dust within evolving galaxy populations. By using principal component analysis to reduce the dimensionality of the problem, I optimally extract the relevant photometric information from large galaxy catalogs. As a demonstration of the technique, I derive the multi-wavelength luminosity function for the galaxies in the released SDSS catalog, and compare the results with those obtained by traditional methods. This technique will be applicable to catalogs of galaxies from datasets obtained by 2MASS, and the SIRTF and GALEX missions.

  10. Possible Quasi-Periodic Gamma-ray Emission from Blazar PG 1553+113

    NASA Astrophysics Data System (ADS)

    Thompson, David; Cutini, Sara; Ciprini, Stefano; Larsson, Stefan; Stamerra, Antonio; Fermi Large Area Telescope Collaboration

    2017-01-01

    We report an update on a possible gamma-ray and multiwavelength nearly periodic oscillation in an active galactic nucleus. Data from the Fermi Large Area Telescope exhibit an apparent quasi-periodicity in the gamma-ray flux (E > 100 MeV) from the GeV/TeV BL Lac object PG 1553+113. The indication of a 2.18 +/- 0.08 year period gamma-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. Further long-term multiwavelength monitoring of this blazar may discriminate among the possible explanations for this quasi-periodicity.

  11. The Ultimate Multiwavelength Quasar Survey (ROSES-2011)

    NASA Astrophysics Data System (ADS)

    Richards, Gordon

    Our objective is to create the ultimate multi-wavelength quasar catalog by combining moderatelydeep, wide-field data in the NASA archives (from GALEX, 2MASS, Spitzer, and WISE) with public optical imaging data from the Sloan Digital Sky Survey. This catalog will extend from deep samples with signficant multi-wavelength coverage in a small area (e.g., SDSS "Stripe 82"), to shallower samples over a larger area with less multiwavelength coverage. Our efforts are a crucial step to bridging between existing spectroscopic surveys and future photometric surveys. Using this catalog, we will investigate the clustering and luminosity function of faint (i »21-23), high-redshift (z > 2.5) quasars in order to break degeneracies between different models of "feedback" from active galactic nuclei (AGN). Our approach is unique in its application of a Bayesian quasar selection algorithm that has been demonstrated to out-perform standard methods and that has been tested on multi-wavelength data. Once quasars have been identified, we will apply our existing photometric redshift algorithms. Richards and Myers are among the world's experts in finding quasars and using their clustering and luminosity function to do cutting-edge science. Quasar clustering analysis will make use of the team's existing algorithms, which are designed to handle the inherently photometric nature of the quasar sample. The quasar luminosity function algorithms are already in place, allowing for timely completion of this project once the multi-wavelength NASA data have been incorporated. As with all quasar catalogs that represent the next generation in improvements, this multi-wavelength quasar catalog will have an impact that extends far beyond our own science goals. This time is ripe for the construction of such a catalog as only in the past year has this dataset covered such a large range of wavelengths and area. In terms of our own science, understanding the form of AGN feedback and the extent to which it

  12. 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.

  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. 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.

  15. SIMULTANEOUS MULTIWAVELENGTH OBSERVATIONS OF MARKARIAN 421 DURING OUTBURST

    SciTech Connect

    Acciari, V. A.; Benbow, W.; Aliu, E.; Aune, T.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Boettcher, M.; Bradbury, S. M.; Butt, Y.; Cannon, A.; Celik, O.; Chow, Y. C.; Cesarini, A.; Ciupik, L.; Cogan, P.; Colin, P.; Cui, W.; Duke, C. E-mail: cui@physics.purdue.ed

    2009-09-20

    We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and VERITAS, both based in Arizona, as well as the MAGIC telescope, based on La Palma in the Canary Islands. The coordinated effort between the gamma-ray groups allowed for truly simultaneous data in UV/X-ray/gamma-ray wavelengths during a significant portion of the XMM-Newton observations. This simultaneous coverage allowed for a reliable search for correlations between UV, X-ray, and gamma-ray variability over the course of the observations. Investigations of spectral hysteresis and modeling of the spectral energy distributions are also presented.

  16. Multiwavelength and polarimetric analysis of the flat spectrum radio quasars 3C 273 and 3C 279

    NASA Astrophysics Data System (ADS)

    Fernandes, Sunil Anthony

    This dissertation presents results of multiwavelength analyses of 3C 273 and 3C 279. The main goals were to identify the gamma-ray emission region and dominant high-energy emission processes. Our methodology consisted of analyzing light curves from radio to gamma-rays over 6 - 8 years and polarimetric, spectral and line emission behavior. In 3C 279, we found that the emission from millimeter to ultraviolet was simultaneous and therefore co-spatial. We identified two active states where different high-energy emission processes were dominant. We found multiwavelength flaring events consistent with component ejections and shocks. We proposed that the gamma-ray emission region changed over time based on observations of both simultaneous and delayed gamma-rays emission with respect to low-energy emission during different time-frames. In 3C 273, we identified a non-thermal flare related to a component ejection and a thermal flare related to accretion. From reverberation mapping we found that the broad line region dynamical behavior over time possibly affects the derived supermassive black hole mass. In both objects we found that the gamma-ray spectral index was variable, and a trend of harder spectral index with higher gamma-ray luminosity. From the identification of different dominant high-energy emission processes, we concluded that the dominant high-energy emission mechanism changes with time. Overall, we concluded that similar results from both objects points to behavior that is potentially common to flat spectrum radio quasars. Increasing the sample size of objects analyzed with similar methodologies will provide more results to confirm or refine our conclusions.

  17. Multiwavelength and Polarimetric Analysis of the Flat Spectrum Radio Quasars 3C 273 and 3C 279

    NASA Astrophysics Data System (ADS)

    Fernandes, Sunil; Patiño-Álvarez, Victor; Chavushyan, Vahram; Schlegel, Eric M.; Lopez-Rodriguez, Enrique; León-Tavares, Jonathan; Carrasco, Luis; Valdés, José; Carramiñana, Alberto

    2017-01-01

    This poster presents results of multiwavelength analyses of 3C 273 and 3C 279. The main goals were to identify the gamma-ray emission region and dominant high-energy emission processes. Our methodology consisted of analyzing light curves from radio to gamma-rays over 6 - 8 years and polarimetric, spectral and line emission behavior.In 3C 279, we found that the emission from millimeter to ultraviolet was simultaneous and therefore co-spatial. We identified two active states where different high-energy emission processes were dominant. We found multiwavelength flaring events consistent with component ejections and shocks. We proposed that the gamma-ray emission region changed over time based on observations of both simultaneous and delayed gamma-rays emission with respect to low-energy emission during different time-frames.In 3C 273, we identified a non-thermal flare related to a component ejection and a thermal flare related to accretion. From reverberation mapping we found that the broad line region dynamical behavior over time possibly affects the derived supermassive black hole mass.In both objects we found that the gamma-ray spectral index was variable, and a trend of harder spectral index with higher gamma-ray luminosity. From the identification of different dominant high-energy emission processes, we concluded that the dominant high-energy emission mechanism changes with time. Overall, we concluded that similar results from both objects points to behavior that is potentially common to flat spectrum radio quasars. Increasing the sample size of objects analyzed with similar methodologies will provide more results to confirm or refine our conclusions.

  18. 2WHSP: A multi-frequency selected catalogue of high energy and very high energy γ-ray blazars and blazar candidates

    NASA Astrophysics Data System (ADS)

    Chang, Y.-L.; Arsioli, B.; Giommi, P.; Padovani, P.

    2017-01-01

    Aims: High synchrotron peaked blazars (HSPs) dominate the γ-ray sky at energies higher than a few GeV; however, only a few hundred blazars of this type have been cataloged so far. In this paper we present the 2WHSP sample, the largest and most complete list of HSP blazars available to date, which is an expansion of the 1WHSP catalogue of γ-ray source candidates off the Galactic plane. Methods: We cross-matched a number of multi-wavelength surveys (in the radio, infrared and X-ray bands) and applied selection criteria based on the radio to IR and IR to X-ray spectral slopes. To ensure the selection of genuine HSPs, we examined the SED of each candidate and estimated the peak frequency of its synchrotron emission (νpeak) using the ASDC SED tool, including only sources with νpeak > 1015 Hz (equivalent to νpeak > 4 eV). Results: We have assembled the largest and most complete catalogue of HSP blazars to date, which includes 1691 sources. A number of population properties, such as infrared colours, synchrotron peak, redshift distributions, and γ-ray spectral properties have been used to characterise the sample and maximize completeness. We also derived the radio log N-log S distribution. This catalogue has already been used to provide seeds to discover new very high energy objects within Fermi-LAT data and to look for the counterparts of neutrino and ultra high energy cosmic ray sources, showing its potential for the identification of promising high-energy γ-ray sources and multi-messenger targets. Table 4 is 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/598/A17

  19. Multiwavelength astronomy and big data

    NASA Astrophysics Data System (ADS)

    Mickaelian, A. M.

    2016-09-01

    Two major characteristics of modern astronomy are multiwavelength (MW) studies (fromγ-ray to radio) and big data (data acquisition, storage and analysis). Present astronomical databases and archives contain billions of objects observed at various wavelengths, both galactic and extragalactic, and the vast amount of data on them allows new studies and discoveries. Astronomers deal with big numbers. Surveys are the main source for discovery of astronomical objects and accumulation of observational data for further analysis, interpretation, and achieving scientific results. We review the main characteristics of astronomical surveys, compare photographic and digital eras of astronomical studies (including the development of wide-field observations), describe the present state of MW surveys, and discuss the Big Data in astronomy and related topics of Virtual Observatories and Computational Astrophysics. The review includes many numbers and data that can be compared to have a possibly overall understanding on the Universe, cosmic numbers and their relationship to modern computational facilities.

  20. Blazar Anti-Sequence of Spectral Variability for Individual TeV Blazars

    NASA Astrophysics Data System (ADS)

    Zhang, Jin; Zhang, Shuang-Nan; Liang, En-Wei

    2013-01-01

    We compile from literature the broadband SEDs of twelve TeV blazars observed simultaneously or quasi-simultaneously with Fermi/LAT and other instruments. Two SEDs are available for each of the objects and the state is identified as a low or high state according to its flux density at GeV/TeV band. The observed SEDs of BL Lac objects (BL Lacs) are fitted well with the synchrotron + synchrotron-self-Compton (syn+SSC) model, whereas the SEDs of the two flat spectrum radio quasars (FSRQs) need to include the contributions of external Compton scattering. In this scenario, it is found that the Doppler factor δ of FSRQs is smaller than that of BL Lacs, but the magnetic field strength B of FSRQs is larger than that of BL Lacs. The increase of the peak frequency of the SEDs is accompanied with the increase of the flux for the individual sources, which seems opposite to the observational phenomena of the blazar sequence. We refer this phenomenonto blazar anti-sequence of spectral variability for individual TeV blazars. However, both the blazar sequence from FSRQs to BL Lacs and blazar anti-sequence of the spectral variability from low state to high state are accompanied by an increase of the break Lorentz factor of the electron's spectrum γb and a decrease of B. We propose a model in which the mass accretion rate Ṁ is the driving force behind both the blazar sequence for ensembles of blazars and the blazar anti-sequence for individual blazars. Specifically we suggest that the differences in <Ṁ> of different blazars produce the observed blazar sequence, but ΔṀ in each blazar results in the observed blazar anti-sequence.

  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. Polarization Signatures of Kink Instabilities in the Blazar Emission Region from Relativistic Magnetohydrodynamic Simulations

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Li, Hui; Guo, Fan; Taylor, Greg

    2017-02-01

    Kink instabilities are likely to occur in the current-carrying magnetized plasma jets. Recent observations of the blazar radiation and polarization signatures suggest that the blazar emission region may be considerably magnetized. While the kink instability has been studied with first-principle magnetohydrodynamic (MHD) simulations, the corresponding time-dependent radiation and polarization signatures have not been investigated. In this paper, we perform comprehensive polarization-dependent radiation modeling of the kink instability in the blazar emission region based on relativistic MHD (RMHD) simulations. We find that the kink instability may give rise to strong flares with polarization angle (PA) swings or weak flares with polarization fluctuations, depending on the initial magnetic topology and magnetization. These findings are consistent with observations. Compared with the shock model, the kink model generates polarization signatures that are in better agreement with the general polarization observations. Therefore, we suggest that kink instabilities may widely exist in the jet environment and provide an efficient way to convert the magnetic energy and produce multiwavelength flares and polarization variations.

  4. UNVEILING THE NATURE OF UNIDENTIFIED GAMMA-RAY SOURCES. I. A NEW METHOD FOR THE ASSOCIATION OF GAMMA-RAY BLAZARS

    SciTech Connect

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

    2013-06-01

    We present a new method for identifying blazar candidates by examining the locus, i.e., the region occupied by the Fermi {gamma}-ray blazars in the three-dimensional color space defined by the WISE infrared colors. This method is a refinement of our previous approach that made use of the two-dimensional projection of the distribution of WISE {gamma}-ray-emitting blazars (the Strip) in the three WISE color-color planes. In this paper, we define the three-dimensional locus by means of a principal component analysis of the color distribution of a large sample of blazars composed of all the ROMA-BZCAT sources with counterparts in the WISE All-Sky Catalog associated with {gamma}-ray sources in the second Fermi-LAT catalog (2FGL; the WISE Fermi blazars sample, WFB). Our new procedure yields a total completeness of c {sub tot} {approx} 81% and a total efficiency of e {sub tot} {approx} 97%. We also obtain local estimates of the efficiency and completeness as functions of the WISE colors and galactic coordinates of the candidate blazars. The catalog of all WISE candidate blazars associated with the WFB sample is also presented, complemented by archival multi-frequency information for the alternative associations. Finally, we apply the new association procedure to all {gamma}-ray blazars in the 2FGL and provide a catalog containing all the {gamma}-ray candidate blazars selected according to our procedure.

  5. 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.

  6. 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.

  7. 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.

  8. 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

  9. 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.

  10. The Utilization of the RCT Telescope for Studies of Blazar Continuum Emission during the GLAST Gamma-Ray Mission

    NASA Astrophysics Data System (ADS)

    Mattox, J. R.; Cominsky, L.; Spear, G.; Carinni, M.; Gelderman, R.; McGruder, C. H.; Guinan, E.; Howell, S.; Davis, D. R.; Everett, M.; Walter, D. K.

    2003-05-01

    The RCT Consortium successfully proposed to refurbish and automate the Kitt Peak 1.3-m telescope, and to operate it as the Robotically Controlled Telescope (RCT). Refurbishment is nearing completion, and observations have begun. The capabilities of the RCT for broad-band optical photometry will be described. A program for systematic optical monitoring of blazars with the RCT is planned. We anticipate that an important utilization of the RCT will be in conjunction with multi-wavelength studies of blazar continuum emission during the operation of NASA's Gamma-ray Large Area Space Telescope (GLAST) satellite, now scheduled for launch in 2006. Refurbishment of the RCT has been made possible by NASA grant NAG58762.

  11. A Continuing Blazar Monitoring Campaign at Radio Wavelengths with the Morehead State University 21-Meter Space Tracking Antenna

    NASA Astrophysics Data System (ADS)

    Pannuti, Thomas; Grimes, C. K.; Tussey, J. M.; Goff, E. J.; Fite, N. D.; Cahall, B. J.

    2011-05-01

    The Morehead State University 21-Meter Space Tracking Antenna is a particularly unique scientific instrument for pursuing undergraduate research in astrophysics. Current research projects in the radio continuum include pointed observations of Galactic supernova remnants and blazars. In the latter case, undergraduate students and faculty have routinely conducted observations of such well-known blazars as BL Lac, CTA 102 and 3C 454.3: in addition, observations of other blazars detected in outburst at other wavelengths (such as the gamma-ray) have also been observed. We present the results of these observations and an initial analysis of the light curves generated by our observations.

  12. Contribution to the extragalactic gamma-ray background from the cascades of very-high energy gamma rays from blazars

    NASA Astrophysics Data System (ADS)

    Venters, Tonia M.

    2009-06-01

    As very-high-energy photons propagate through the extragalactic background light (EBL), they interact with the soft photons and initiate electromagnetic cascades of lower energy photons and electrons. The collective intensity of a cosmological population emitting at very-high energies (VHE) will be attenuated at the highest energies through interactions with the EBL and enhanced at lower energies by the resulting cascade. We calculate the cascade radiation created by VHE photons produced by blazars and investigate the effects of cascades on the collective intensity of blazars and the resulting effects on the extragalactic gamma-ray background. We find that cascade radiation greatly enhances the collective intensity from blazars at high energies before turning over due to attenuation. The prominence of the resulting features depends on the blazar gamma-ray luminosity function, spectral index distribution, and the model of the EBL. We additionally calculate the cascade radiation from the distinct spectral sub-populations of blazars, BL Lacertae objects (BL Lacs) and flat-spectrum radio quasars (FSRQs), finding that the collective intensity of BL Lacs is considerably more enhanced by cascade radiation than that of the FSRQs. Finally, we discuss the implications that this analysis and upcoming Fermi observations could have for the nature of the EBL, the evolution of blazars, blazar spectra, and other sources of gamma-ray emission.

  13. 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.

  14. THE SMARTS MULTI-EPOCH OPTICAL SPECTROSCOPY ATLAS (SaMOSA): AN ANALYSIS OF EMISSION LINE VARIABILITY IN SOUTHERN HEMISPHERE FERMI BLAZARS

    SciTech Connect

    Isler, Jedidah C.; Urry, C. M.; Bailyn, C.; Coppi, P.; Brady, M.; MacPherson, E.; Hasan, I.; Buxton, M.; Smith, P. S.

    2015-05-01

    We present multi-epoch optical spectroscopy of seven southern Fermi-monitored blazars from 2008 to 2013 using the Small and Medium Aperture Research Telescope System (SMARTS), with supplemental spectroscopy and polarization data from the Steward Observatory. We find that the emission lines are much less variable than the continuum; four of seven blazars had no detectable emission line variability over the 5 yr observation period. This is consistent with photoionization primarily by an accretion disk, allowing us to use the lines as a probe of disk activity. Comparing optical emission line flux with Fermi γ-ray flux and optical polarized flux, we investigate whether relativistic jet variability is related to the accretion flow. In general, we see no such dependence, suggesting that the jet variability is likely caused by internal processes like turbulence or shock acceleration rather than a variable accretion rate. However, three sources showed statistically significant emission line flares in close temporal proximity to very large Fermi γ-ray flares. While we do not have sufficient emission line data to quantitatively assess their correlation with the γ-ray flux, it appears that in some cases the jet might provide additional photoionizing flux to the broad-line region (BLR), which implies that some γ-rays are produced within the BLR, at least for these large flares.

  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. Blazar Observations with the Robotically Controlled Telescope

    NASA Astrophysics Data System (ADS)

    Walters, R.; Carini, M. T.; Mattox, J.; Gelderman, R.

    2004-12-01

    Blazars are the most highly variable AGNs known. By virtue of their featureless spectrum, the only diagnostic we have of the physics at work in these objects is their continuum variability. Optical continuum variations, when combined with observations at higher energies, provide valuable insights into the nature of the emission processes at work in these objects. We present the first results of our program to obtain and analyze high time resolution light curves of Blazars using the Robotically Controlled Telescope.

  17. 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.

  18. 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.

  19. 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}⊙ {{yr}}-1), which agrees with hydrodynamic predictions, and provides a consistent picture along the X-ray, UV, optical, and radio spectral domains.

  20. 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

  1. 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

  2. A physical classification scheme for blazars

    NASA Astrophysics Data System (ADS)

    Landt, Hermine; Padovani, Paolo; Perlman, Eric S.; Giommi, Paolo

    2004-06-01

    Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars based on the strength of their emission lines. This is performed rather arbitrarily by defining a diagonal line in the Ca H&K break value-equivalent width plane, following Marchã et al. We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS) and 2-Jy radio survey and find a significant bimodality for the narrow emission line [OIII]λ5007. This suggests the presence of two physically distinct classes of radio-loud active galactic nuclei (AGN). We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII]λ5007-[OII]λ3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars.

  3. 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.

  4. The Contribution of Fermi-2LAC Blazars to Diffuse TeV–PeV Neutrino Flux

    NASA Astrophysics Data System (ADS)

    Aartsen, M. G.; Abraham, K.; Ackermann, M.; Adams, J.; Aguilar, J. A.; Ahlers, M.; Ahrens, M.; Altmann, D.; Andeen, K.; Anderson, T.; Ansseau, I.; Anton, G.; Archinger, M.; Arguelles, C.; Arlen, T. C.; Auffenberg, J.; Axani, S.; Bai, X.; Barwick, S. W.; Baum, V.; Bay, R.; Beatty, J. J.; Becker Tjus, J.; Becker, K.-H.; BenZvi, S.; Berghaus, P.; Berley, D.; Bernardini, E.; Bernhard, A.; Besson, D. Z.; Binder, G.; Bindig, D.; Bissok, M.; Blaufuss, E.; Blot, S.; Boersma, D. J.; Bohm, C.; Börner, M.; Bos, F.; Bose, D.; Böser, S.; Botner, O.; Braun, J.; Brayeur, L.; Bretz, H.-P.; Burgman, A.; Casey, J.; Casier, M.; Cheung, E.; Chirkin, D.; Christov, A.; Clark, K.; Classen, L.; Coenders, S.; Collin, G. H.; Conrad, J. M.; Cowen, D. F.; Cruz Silva, A. H.; Daughhetee, J.; Davis, J. C.; Day, M.; de André, J. P. A. M.; De Clercq, C.; del Pino Rosendo, E.; Dembinski, H.; De Ridder, S.; Desiati, P.; de Vries, K. D.; de Wasseige, G.; de With, M.; DeYoung, T.; Díaz-Vélez, J. C.; di Lorenzo, V.; Dujmovic, H.; Dumm, J. P.; Dunkman, M.; Eberhardt, B.; Ehrhardt, T.; Eichmann, B.; Euler, S.; Evenson, P. A.; Fahey, S.; Fazely, A. R.; Feintzeig, J.; Felde, J.; Filimonov, K.; Finley, C.; Flis, S.; Fösig, C.-C.; Franckowiak, A.; Fuchs, T.; Gaisser, T. K.; Gaior, R.; Gallagher, J.; Gerhardt, L.; Ghorbani, K.; Giang, W.; Gladstone, L.; Glagla, M.; Glüsenkamp, T.; Goldschmidt, A.; Golup, G.; Gonzalez, J. G.; Góra, D.; Grant, D.; Griffith, Z.; Haack, C.; Haj Ismail, A.; Hallgren, A.; Halzen, F.; Hansen, E.; Hansmann, B.; Hansmann, T.; Hanson, K.; Hebecker, D.; Heereman, D.; Helbing, K.; Hellauer, R.; Hickford, S.; Hignight, J.; Hill, G. C.; Hoffman, K. D.; Hoffmann, R.; Holzapfel, K.; Homeier, A.; Hoshina, K.; Huang, F.; Huber, M.; Huelsnitz, W.; Hultqvist, K.; In, S.; Ishihara, A.; Jacobi, E.; Japaridze, G. S.; Jeong, M.; Jero, K.; Jones, B. J. P.; Jurkovic, M.; Kappes, A.; Karg, T.; Karle, A.; Katz, U.; Kauer, M.; Keivani, A.; Kelley, J. L.; Kemp, J.; Kheirandish, A.; Kim, M.; Kintscher, T.; Kiryluk, J.; Kittler, T.; Klein, S. R.; Kohnen, G.; Koirala, R.; Kolanoski, H.; Konietz, R.; Köpke, L.; Kopper, C.; Kopper, S.; Koskinen, D. J.; Kowalski, M.; Krings, K.; Kroll, M.; Krückl, G.; Krüger, C.; Kunnen, J.; Kunwar, S.; Kurahashi, N.; Kuwabara, T.; Labare, M.; Lanfranchi, J. L.; Larson, M. J.; Lennarz, D.; Lesiak-Bzdak, M.; Leuermann, M.; Leuner, J.; Lu, L.; Lünemann, J.; Madsen, J.; Maggi, G.; Mahn, K. B. M.; Mancina, S.; Mandelartz, M.; Maruyama, R.; Mase, K.; Maunu, R.; McNally, F.; Meagher, K.; Medici, M.; Meier, M.; Meli, A.; Menne, T.; Merino, G.; Meures, T.; Miarecki, S.; Middell, E.; Mohrmann, L.; Montaruli, T.; Moulai, M.; Nahnhauer, R.; Naumann, U.; Neer, G.; Niederhausen, H.; Nowicki, S. C.; Nygren, D. R.; Obertacke Pollmann, A.; Olivas, A.; Omairat, A.; O’Murchadha, A.; Palczewski, T.; Pandya, H.; Pankova, D. V.; Penek, Ö.; Pepper, J. A.; Pérez de los Heros, C.; Pfendner, C.; Pieloth, D.; Pinat, E.; Posselt, J.; Price, P. B.; Przybylski, G. T.; Quinnan, M.; Raab, C.; Rädel, L.; Rameez, M.; Rawlins, K.; Reimann, R.; Relich, M.; Resconi, E.; Rhode, W.; Richman, M.; Riedel, B.; Robertson, S.; Rongen, M.; Rott, C.; Ruhe, T.; Ryckbosch, D.; Rysewyk, D.; Sabbatini, L.; Sanchez Herrera, S. E.; Sandrock, A.; Sandroos, J.; Sarkar, S.; Satalecka, K.; Schimp, M.; Schlunder, P.; Schmidt, T.; Schoenen, S.; Schöneberg, S.; Schönwald, A.; Schumacher, L.; Seckel, D.; Seunarine, S.; Soldin, D.; Song, M.; Spiczak, G. M.; Spiering, C.; Stahlberg, M.; Stamatikos, M.; Stanev, T.; Stasik, A.; Steuer, A.; Stezelberger, T.; Stokstad, R. G.; Stößl, A.; Ström, R.; Strotjohann, N. L.; Sullivan, G. W.; Sutherland, M.; Taavola, H.; Taboada, I.; Tatar, J.; Ter-Antonyan, S.; Terliuk, A.; Tešić, G.; Tilav, S.; Toale, P. A.; Tobin, M. N.; Toscano, S.; Tosi, D.; Tselengidou, M.; Turcati, A.; Unger, E.; Usner, M.; Vallecorsa, S.; Vandenbroucke, J.; van Eijndhoven, N.; Vanheule, S.; van Rossem, M.; van Santen, J.; Veenkamp, J.; Vehring, M.; Voge, M.; Vraeghe, M.; Walck, C.; Wallace, A.; Wallraff, M.; Wandkowsky, N.; Weaver, Ch.; Wendt, C.; Westerhoff, S.; Whelan, B. J.; Wickmann, S.; Wiebe, K.; Wiebusch, C. H.; Wille, L.; Williams, D. R.; Wills, L.; Wissing, H.; Wolf, M.; Wood, T. R.; Woolsey, E.; Woschnagg, K.; Xu, D. L.; Xu, X. W.; Xu, Y.; Yanez, J. P.; Yodh, G.; Yoshida, S.; Zoll, M.; IceCube Collaboration

    2017-01-01

    The recent discovery of a diffuse cosmic neutrino flux extending up to PeV energies raises the question of which astrophysical sources generate this signal. Blazars are one class of extragalactic sources which may produce such high-energy neutrinos. We present a likelihood analysis searching for cumulative neutrino emission from blazars in the 2nd Fermi-LAT AGN catalog (2LAC) using IceCube neutrino data set 2009-12, which was optimized for the detection of individual sources. In contrast to those in previous searches with IceCube, the populations investigated contain up to hundreds of sources, the largest one being the entire blazar sample in the 2LAC catalog. No significant excess is observed, and upper limits for the cumulative flux from these populations are obtained. These constrain the maximum contribution of 2LAC blazars to the observed astrophysical neutrino flux to 27% or less between around 10 TeV and 2 PeV, assuming the equipartition of flavors on Earth and a single power-law spectrum with a spectral index of ‑2.5. We can still exclude the fact that 2LAC blazars (and their subpopulations) emit more than 50% of the observed neutrinos up to a spectral index as hard as ‑2.2 in the same energy range. Our result takes into account the fact that the neutrino source count distribution is unknown, and it does not assume strict proportionality of the neutrino flux to the measured 2LAC γ-ray signal for each source. Additionally, we constrain recent models for neutrino emission by blazars.

  5. 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.

  6. A Luminous and Isolated Gamma-Ray Flare from the Blazar B2 1215+30

    NASA Astrophysics Data System (ADS)

    Abeysekara, A. U.; Archambault, S.; Archer, A.; Benbow, W.; Bird, R.; Buchovecky, M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cerruti, M.; Chen, X.; Ciupik, L.; Cui, W.; Dickinson, H. J.; Eisch, J. D.; Errando, M.; Falcone, A.; Feng, Q.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Grube, J.; Hütten, M.; Håkansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; 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.; Ong, R. A.; Otte, A. N.; Park, N.; Pelassa, V.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rulten, C.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Wakely, S. P.; Weiner, O. M.; Weinstein, A.; Wilhelm, A.; Williams, D. A.; VERITAS Collaboration; Fegan, S.; Giebels, B.; Horan, D.; Fermi-LAT Collaboration; Berdyugin, A.; Kuan, J.; Lindfors, E.; Nilsson, K.; Oksanen, A.; Prokoph, H.; Reinthal, R.; Takalo, L.; Zefi, F.

    2017-02-01

    B2 1215+30 is a BL-Lac-type blazar that was first detected at TeV energies by the MAGIC atmospheric Cherenkov telescopes and subsequently confirmed by the Very Energetic Radiation Imaging Telescope Array System (VERITAS) observatory with data collected between 2009 and 2012. In 2014 February 08, VERITAS detected a large-amplitude flare from B2 1215+30 during routine monitoring observations of the blazar 1ES 1218+304, located in the same field of view. The TeV flux reached 2.4 times the Crab Nebula flux with a variability timescale of < 3.6 {hr}. Multiwavelength observations with Fermi-LAT, Swift, and the Tuorla Observatory revealed a correlated high GeV flux state and no significant optical counterpart to the flare, with a spectral energy distribution where the gamma-ray luminosity exceeds the synchrotron luminosity. When interpreted in the framework of a one-zone leptonic model, the observed emission implies a high degree of beaming, with Doppler factor δ > 10, and an electron population with spectral index p< 2.3.

  7. What determines the observational differences of blazars?

    NASA Astrophysics Data System (ADS)

    Fan, Xu-Liang; Bai, Jin-Ming; Mao, Ji-Rong

    2016-11-01

    We examine the scenario that the Doppler factor determines the observational differences of blazars. Significantly negative correlations are found between the observational synchrotron peak frequency and the Doppler factor. After correcting the Doppler boosting, the intrinsic peak frequency has a tight linear relation with the Doppler factor. It is interesting that this relation is consistent with the scenario that the black hole mass governs both the bulk Lorentz factor and the synchrotron peak frequency. In addition, the distinction between the kinetic jet powers of BL Lac objects and flat spectrum radio quasars disappears after the boosting factor δ 2 is considered. The negative correlation between the peak frequency and the observational isotropic luminosity, known as the blazar sequence, also disappears after the Doppler boosting is corrected. We also find that the correlation between the Compton dominance and the Doppler factor exists for all types of blazars. Therefore, this correlation is unsuitable for examining the external Compton emission dominance.

  8. Blazars in Hard X-rays

    NASA Astrophysics Data System (ADS)

    Ghisellini, Gabriele

    2009-05-01

    Although blazars are thought to emit most of their luminosity in the γ-ray band, there are subclasses of them very prominent in hard X-rays. These are the best candidates to be studied by Simbol-X. They are at the extremes of the blazar sequence, having very small or very high jet powers. The former are the class of TeV emitting BL Lacs, whose synchrotron emission often peaks at tens of keV or more. The latter are the blazars with the most powerful jets, have high black hole masses accreting at high (i.e. close to Eddington) rates. These sources are predicted to have their high energy peak even below the MeV band, and therefore are very promising candidates to be studied with Simbol-X.

  9. A model for periodic blazars

    NASA Astrophysics Data System (ADS)

    Sobacchi, Emanuele; Sormani, Mattia C.; Stamerra, Antonio

    2017-02-01

    We describe a scenario to explain blazar periodicities with time-scales of ˜ few years. The scenario is based on a binary supermassive black hole (SMBH) system in which one of the two SMBHs carries a jet. We discuss the various mechanisms that can cause the jet to precess and produce corkscrew patterns through space with a scale of ˜ few pc. It turns out that the dominant mechanism responsible for the precession is simply the imprint of the jet-carrying SMBH orbital speed on the jet. Gravitational deflection and Lense-Thirring precession (due to the gravitational field of the other SMBH) are second-order effects. We complement the scenario with a kinematical jet model which is inspired to the spine-sheath structure observed in M87. One of the main advantages of such a structure is that it allows the peak of the synchrotron emission to scale with frequency according to νF ∝ νξ as the viewing angle is changed, where ξ is not necessarily 3 or 4 as in the case of jets with uniform velocity, but can be ξ ˜ 1. Finally, we apply the model to the source PG1553+113, which has been recently claimed to show a Tobs = (2.18 ± 0.08) yr periodicity. We are able to reproduce the optical and gamma-ray light curves and multiple synchrotron spectra simultaneously. We also give estimates of the source mass and size.

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

    PubMed

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

    2013-05-01

    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.

  11. 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.

  12. Multi-wavelength polarimetric studies of relativistic jets in active galactic nuclei

    NASA Astrophysics Data System (ADS)

    Casadio, Carolina

    This Thesis is focussed on the study of relativistic jets, commonly present in multiple astrophysical sites, from active galactic nuclei (AGN), to micro- quasars or gamma-ray bursts (GRBs). In the case of AGN, huge amounts of energy across the whole electromagnetic spectrum are released as a conse- quence of the accretion of material onto a supermassive back hole (SMBH) lurking at their centers. The accretion leads to the formation of a pair of very powerful and highly collimated jets extending far beyond the size of the host galaxy. We analyzed the correlation between the multi-wavelength emission and the radio jet in three powerful AGN, the radio galaxies 3C 120 and M 87, and the quasar CTA 102. The main goal of this Thesis is to obtain a better understanding of the jet dynamics and the role played by the magnetic field, and to determine what are the sites and mechanisms for the production of the γ-ray emission observed in these sources. We have performed multi-wavelength studies of the radio galaxy 3C 120 and the blazar CTA 102 during unprecedented γ-ray flares for both sources. The NASA satellite Fermi registered in September-October 2012 a bright γ-ray flare in CTA 102, and between December 2012 and October 2014 a prolonged γ-ray activity in the radio galaxy 3C 120. In both studies, to determine where the γ-ray emission is produced, the analysis of Fermi data has been compared with a detailed study of the morphology and evolution of the parsec scale jet through a series of extremely-high angular resolution Very Long Baseline Array (VLBA) images at 43 GHz from the Boston University blazar monitoring program, in which our research group is actively participating. In the case of 3C 120 we have also collected 15 GHz VLBA data from the MOJAVE monitoring program, extending our study of the radio jet from June 2008 to May 2014. For the study of CTA 102 a total of 80 VLBA images at 43 GHz have been analyzed and compared with observations across the whole

  13. Time-Dependent SSC Cooling Effects on Blazar Emission

    NASA Astrophysics Data System (ADS)

    Zacharias, Michael; Schlickeiser, Reinhard

    2014-03-01

    Blazars are among the most violent sources in the cosmos exhibiting flaring states with remarkably different variability time scales. Especially rapid flares with flux doubling time scales of the order of minutes have been puzzling for quite some time. Many modeling attempts use the well known linear and steady-state scenario for the cooling and emission processes in the jet, albeit the obvious strongly time-dependent nature of flares. Due to the feedback of the self-produced synchrotron radiation with additional scattering by the relativistic electrons, the synchrotron-self Compton (SSC) effect is inherently time-dependent. Recently, an analytical analysis on the effects of this nonlinear behavior has been presented. Here, we summarize these results concerning the effect of the time-dependent SSC cooling on the spectral energy distribution (SED), and the synchrotron lightcurves of blazars. For that, we calculated analytically the synchrotron, SSC and external Compton (EC) component of the SED, giving remarkably different spectral features compared to the standard linear approach. The resulting fluxes strongly depend on the parameters, and SSC might have a strong effect even in sources with strong external photon fields (such as FSRQs). For the synchrotron lightcurve we considered the effects of retardation, including the geometry of the source. The retardation might smear out some effects of the time-dependent cooling, but since lightcurves and SEDs have to be fitted simultaneously with the same set of parameters, the results give nonetheless important clues about the source. Thus, we argue for a wide utilization of the time-dependent treatment in modeling (especially rapid) blazar flares, since it accounts for features in the SED and the lightcurves that are usually accounted for by introducing several breaks in the electron distribution without any physical justification.

  14. 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.

  15. 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.

  16. 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.

  17. 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.

  18. 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.

  19. Time Delay and Accretion Disk Size Measurements in the Lensed Quasar SBS 0909+532 from Multiwavelength Microlensing Analysis

    NASA Astrophysics Data System (ADS)

    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.; Falco, Emilio E.

    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_{AB} = 50^{+2}_{-4}\\,{days}, where the stated uncertainties represent the bounds of the formal 1σ 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 {(r s, r /cm)[cos i/0.5]1/2} = 15.3 ± 0.3 and log {(r s, g /cm)[cos i/0.5]1/2} = 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.

  20. Simultaneous Swift and Rapid Eye Mount telescope observations of the blazar PKS 0537-441

    NASA Astrophysics Data System (ADS)

    Li, Xiao-Pan; Luo, Yu-Hui; Zhang, Li; Yang, Cheng; Yang, Hai-Tao; Cai, Yan

    2017-02-01

    We present the results of simultaneous multiwavelength observations of the blazar PKS 0537-441 performed with the Rapid Eye Mount telescope (REM) and Swift in the period 2009-2011. During our campaign, PKS 0537-441 showed prominent activity with well-correlated light curves from near-infrared to X-rays in different time epochs. The multiwavelength light curves exhibit several significant flares, in which the 2009 November flare particularly presents a double-peak feature, while the 2010 February flare shows strong optical variability (up to a factor of ˜5). The REM data show smaller fractional variability amplitudes than the Swift data. There is a general correlation between optical and X-rays, time-lags have been determined with data correlation methods and their uncertainties with Monte Carlo runs, but they are either very uncertain or too long (of the order of 300 d) to be physically relevant. The X-ray spectra exhibit neither absorption nor emission features characteristically. A slight harder-when-brighter trend in the 2-10 keV energy band is detected. The optical/ultraviolet spectra suggest the presence of thermal emission. We find evidence that the broad-band spectrum is steeper when the degree of variability is larger.

  1. 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.; 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.

  2. The radio-γ-ray connection in Fermi blazars

    NASA Astrophysics Data System (ADS)

    Ghirlanda, G.; Ghisellini, G.; Tavecchio, F.; Foschini, L.; Bonnoli, G.

    2011-05-01

    We study the correlation between the γ-ray flux (Fγ), averaged over the first 11 months of the Fermi survey and integrated above 100 MeV, and the radio flux density (Fr at 20 GHz) of Fermi sources associated with a radio counterpart in the 20-GHz Australia Telescope Compact Array (AT20G) survey. Considering the blazars detected in both bands, the correlation is highly significant and has the form Fγ∝F0.85±0.04r, similar to BL Lacertae objects and flat-spectrum radio quasars. However, only a small fraction (˜1/15) of the AT20G radio sources with flat radio spectra are detected by Fermi. To understand if this correlation is real, we examine the selection effects introduced by the flux limits of both the radio and the γ-ray surveys, and the importance of variability of the γ-ray flux. After accounting for these effects, we find that the radio-γ-ray flux correlation is real, but its slope is steeper than the observed one, that is, Fγ∝Fδr with δ in the range 1.25-1.5. The observed Fγ-Fr correlation and the fraction of radio sources detected by Fermi are reproduced assuming a long-term γ-ray flux variability, following a lognormal probability distribution with standard deviation σ≥ 0.5 (corresponding to Fγ varying by at least a factor of 3). Such a variability is compatible, even if not necessarily equal, with what is observed when comparing, for the sources in common, the EGRET and the Fermi γ-ray fluxes (even if the Fermi fluxes are averaged over ˜1 yr). Another indication of variability is the non-detection of 12 out of 66 EGRET blazars by Fermi, despite its higher sensitivity. We also study the strong linear correlation between the γ-ray and the radio luminosity of the 144 AT20G-Fermi associations with known redshift and show, through partial correlation analysis, that it is statistically robust. Two possible implications of these correlations are discussed: the contribution of blazars to the extragalactic γ-ray background and the prediction

  3. 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.

  4. Are Jets Monoparametric? Extending the Blazar Sequence to the Blazar Envelope in the Fermi Era

    NASA Astrophysics Data System (ADS)

    Meyer, Eileen T.; Fossati, G.; Georganopoulos, M.; Lister, M.

    2011-01-01

    The blazar sequence, first discovered by Fossati et al. (1998), unified the broad emission line, high-powered flat spectrum radio quasars (FSRQ) with the optically featureless BL Lac objects through a simple anti-correlation between synchrotron peak luminosity and peak frequency. This paradigm has come under scrutiny as increasing numbers of sources have emerged off the sequence. We have found evidence for a simple underlying scheme for the apparent 'blazar envelope': blazar jets are mono-parametric engines, such that source power (as measured from the low-frequency, un-beamed extended emission) creates a monotonic relationship between the intrinsic peak luminosity and peak frequency of the synchrotron and inverse Compton components. The envelope naturally emerges below the sequence due to the drop in peak luminosity and frequency as sources are progressively aligned away from our line-of-sight and relativistic beaming drops. We present key evidence for this scheme which has impact on theoretical models of blazar jets with velocity profiles. The envelope also allows us to more clearly unify blazars and the parent population of FR I and II radio galaxies. I will discuss some of the difficulties and caveats in measuring the source power through extended emission, current results, and future applications of this simple idea to broader unification schemes and other source classes.

  5. 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.

  6. 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.

  7. 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.

  8. BLAZAR FLARES FROM COMPTON DRAGGED SHELLS

    SciTech Connect

    Golan, Omri; Levinson, Amir

    2015-08-10

    We compute the dynamics and emission of dissipative shells that are subject to a strong Compton drag, under simplifying assumptions about the dissipation mechanism. We show that under conditions prevailing in blazars, substantial deceleration is anticipated on sub-parsec and parsec scales in cases of rapid dissipation. Such episodes may be the origin of some of the flaring activity occasionally observed in gamma-ray blazars. The shape of the light curves thereby produced reflects the geometry of the emitting surface if the deceleration is very rapid, or the dynamics of the shell if the deceleration is delayed, or initially more gradual, owing, e.g., to continuous injection of energy and momentum.

  9. 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.

  10. 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.

  11. 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.

  12. 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.

  13. 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 degrees of the local direction of the jet. The EVPAs of the jet components are usually within 20 degrees 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.

  14. Multi-wavelength applications of gravitational lensing

    NASA Astrophysics Data System (ADS)

    Fadely, Ross

    2010-12-01

    Using an array of multi-wavelength data, we examine a variety of astrophysical problems with gravitational lensing. First, we seek to understand the mass distribution of an early-type galaxy with an analysis of the lens Q0957+561. We dissect the lens galaxy into luminous and dark components, and model the environment using results from weak lensing. Combining constraints from newly-discovered lensed images and stellar population models, we find the lens has a density profile which is shallower than isothermal, unlike those of typical early-type galaxies. Finally, using the measured time delay between the quasar images we find the Hubble constant to be H 0 = 79.3+6.7-8.5 km s-1 Mpc-1 . One intriguing application of lensing is to exploit the lens magnification boost to study high-redshift objects in greater detail than otherwise possible. Here, we analyze the mid-infrared properties of two lensed z ˜ 2 star-forming galaxies, SDSS J120602.09+514229.5 and SDSS J090122.37+181432.3, using Spitzer /IRS spectra to study their rest-frame ˜ 5-12 μm emission. Both systems exhibit strong polycyclic aromatic hydrocarbon (PAH) features in the spectra, indicating strong star formation and the absence of significant AGN activity. For SDSS J090122.37+181432.3, this detection belies that inferred from optical measurements, indicating mid-IR spectroscopy provides key information needed to understand the properties of high-redshift star-forming galaxies. While lensing provides measurements of the macroscopic properties of lens systems, it can also shed light on small-scale structure of galaxies. To identify and understand lens substructure, we examine the multi-wavelength properties of flux ratios for six lenses. Variations of the flux ratios with wavelength can be used to study the lensed quasars and the small-scale mass distribution of lens galaxies. We detect strong multi-wavelength variations in the lenses HE 0435-1223 and SDSS 0806+2006. For HE 0435-1223, we study its

  15. 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.

  16. 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}.

  17. 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.

  18. Time Dependent Leptonic and Lepto-Hadronic Modeling of Blazar Emission

    NASA Astrophysics Data System (ADS)

    DIltz, Christopher S.

    Active galactic nuclei (AGN) are known to exhibit multi-wavelength variability across the whole electromagnetic spectrum. In the context of blazars, the variability timescale can be as short as a few minutes. Correlated variability has been seen in different bands of the electromagnetic spectrum: from radio wavelengths to high energy gamma-rays. This correlated variability in different wavelength bands can put constraints on the particle content, acceleration mechanisms and radiative properties of the relativistic jets that produce blazar emission. Two models are typically invoked to explain the origin of the broadband emission across the electromagnetic spectrum: Leptonic and Hadronic Modeling. Both models have had success in reproducing the broadband spectral energy distributions (SEDs) of blazar emission with different input parameters, making the origin of the emission difficult to determine. However, flaring events cause the spectral components that produce the SED to evolve on different timescales, producing different light curve behavior for both models. My Ph.D. research involves developing one-zone time dependent leptonic and lepto-hadronic codes to reproduce the broadband SEDs of blazars and then model flaring scenarios in order to find distinct differences between the two models. My lepto-hadronic code also considers the time dependent evolution of the radiation emitted by secondary particles (pions and muons) generated from photo-hadronic interactions between the photons and protons in the emission region. I present fits to the broadband SEDs of the flat spectrum radio quasars (FSRQs) 3C 273 and 3C 279 using my one-zone leptonic and lepto-hadronic model, respectively. I showed that by considering perturbations of any one of the selected input parameters for both models: magnetic field, particle injection luminosity, particle spectral index, and stochastic acceleration time scale, distinct differences arise in the light curves for the optical, X-ray and

  19. 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.

  20. Multiwavelength Strontium Vapor Lasers

    NASA Astrophysics Data System (ADS)

    Soldatov, A. N.; Yudin, N. A.

    2016-08-01

    Based on an analysis of experimental and theoretical works, modern notion on conditions of forming of population density inversion on self-terminating IR transitions of alkali-earth metals is given. It is demonstrated that there is a significant difference in the inversion formation in lasers on self-terminating transitions in the visible and near-IR ranges and lasers on self-terminating transitions of alkali-earth metals lasing IR lines in the mid-IR range. It is shown that in the discharge circuit of lasers on self-terminating metal atom transitions (LSMT) there are processes strengthening the influence of the known mechanism limiting the frequency and energy characteristics (FEC) of radiation caused by the presence of prepulse electron concentration. The mechanism of influence of these processes on FEC of the LSMT and technical methods of their neutralization are considered. The possibility of obtaining average lasing power of ~200 W from one liter volume of the active medium of the strontium vapor laser is demonstrated under conditions of neutralization of these processes.

  1. 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.

  2. Suzaku Observation of TeV Blazar the 1ES 1218+304: Clues on Particle Acceleration in an Extreme TeV Blazar

    SciTech Connect

    Sato, R.; Kataoka, J.; Takahashi, T.; Madejski, G.M.; Rugamer, S.; Wagner, S.J.

    2008-04-22

    We observed the TeV blazar 1ES 1218+304 with the X-ray astronomy satellite Suzaku in May 2006. At the beginning of the two-day continuous observation, we detected a large flare in which the 5-10 keV flux changed by a factor of {approx}2 on a timescale of 5 x 10{sup 4} s. During the flare, the increase in the hard X-ray flux clearly lagged behind that observed in the soft X-rays, with the maximum lag of 2.3 x 10{sup 4} s observed between the 0.3?1 keV and 5?10 keV bands. Furthermore we discovered that the temporal profile of the flare clearly changes with energy, being more symmetric at higher energies. From the spectral fitting of multi-wavelength data assuming a one-zone, homogeneous synchrotron self-Compton model, we obtain B {approx} 0.047 G, emission region size R = 3.0 x 10{sup 16} cm for an appropriate beaming with a Doppler factor of {delta} = 20. This value of B is in good agreement with an independent estimate through the model fit to the observed time lag ascribing the energy-dependent variability to differential acceleration timescale of relativistic electrons provided that the gyro-factor {zeta} is 10{sup 5}.

  3. 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.

  4. 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.

  5. Multiwavelength studies of X-ray selected extragalactic sample

    NASA Astrophysics Data System (ADS)

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

    2016-11-01

    The joint catalogue of Active Galactic Nuclei selected from optical identications of X-ray sources was created as a combination of two samples: Hamburg-ROSAT Catalogue (HRC) and Byurakan-Hamburg-ROSAT Catalogue (BHRC). Both are based on optical identications of X-ray sources from ROSAT catalogues using low-dispersion spectra of Hamburg Quasar Survey (HQS). However, HRC and BHRC contain a number of misidentications and using the recent optical and multiwavelength (MW) catalogues we have revised both samples excluding false AGN and adding new genuine ones. Thus a new large homogeneous complete sample of 4253 X-ray selected AGN was created. 3352 of them are listed in the Catalogue of QSOs and Active Galaxies and 387 also are in Roma Multifrequency Catalogue of Blazars. 901 candidate AGN are subjects for further study. We classified 173 of these objects using their SDSS DR12 spectra. Following activity types were revealed: 61 AGN, 21 HII galaxies, 12 emission-line galaxies without definite type, 71 absorption-line galaxies, 2 stars, and 6 were classified as "Unknown". A special emphasis is made on narrow-line Sy1.0-Sy1.5 galaxies and QSOs, as many of them have soft X-ray, strong FeII lines, and relatively narrow lines coming from BLR ("narrow broad lines"). As a result, the sample of genuine AGN was enlarged to 3413 objects. We have retrieved MW data from recent catalogues and carried out statistical investigations for the whole AGN sample. An attempt to find connections between fluxes in different bands for different types of sources, and to identify their characteristics thus confirming candidate AGNs has been carried out. We have analyzed X-ray properties of these sources to nd a limit between normal galaxies and X-ray AGN.

  6. Understanding the nature of the blazar CGRaBS J0211+1051

    SciTech Connect

    Chandra, Sunil; Baliyan, Kiran S.; Ganesh, S.; Foschini, L.

    2014-08-20

    The source CGRaBS J0211+1051 (MG1 J021114+1051, z = 0.20) flared up on 2011 January 23 in high-energy γ-rays as reported by the Large Area Telescope (LAT) on board Fermi. This event was followed by increased activity at the UV, optical, and radio frequencies as detected by the observing facilities worldwide. The source also showed a high and variable optical polarization based on which it was proposed to be a low-energy peaked BL Lac object (LBL). The present work reports first comprehensive multi-wavelength study of this source using data in the radio, optical, UV, X- and γ-rays, and optical polarization. Using these multi-wavelength data on the source, we have estimated various parameters and verified its classification vis-a-vis blazar sequence. Multi-waveband light curves are used to discuss the flaring events of 2011 January in an attempt to address the nature of the source and pinpoint the possible physical processes responsible for the emission. The light curves show variations in the high-energy γ-rays to be correlated with X-ray, UV, and optical variations, perhaps indicating their co-spatial origin. Our optical data, quasi-simultaneous with UV (Swift-UVOT) and X-ray (Swift-XRT) data, enabled us to trace the low-energy (synchrotron) component of the spectral energy distribution (SED) for CGRaBS J0211+1051 for the first time. The SED shows the synchrotron peak to lie at ∼1.35 × 10{sup 14} Hz, confirming that CGRaBS J0211+1051 is an LBL. Some other parameters, such as the local magnetic field (∼5.93 G) and black hole mass (∼2.4 × 10{sup 8} M {sub ☉}), are also estimated which are in agreement with their typical values for the blazars. Based on the present study, identification of the Fermi/LAT source, 2FGL J0211.2+1050, with its BL Lac counterpart CGRaBS J0211+1051 is confirmed.

  7. Understanding the Nature of the Blazar CGRaBS J0211+1051

    NASA Astrophysics Data System (ADS)

    Chandra, Sunil; Baliyan, Kiran S.; Ganesh, S.; Foschini, L.

    2014-08-01

    The source CGRaBS J0211+1051 (MG1 J021114+1051, z = 0.20) flared up on 2011 January 23 in high-energy γ-rays as reported by the Large Area Telescope (LAT) on board Fermi. This event was followed by increased activity at the UV, optical, and radio frequencies as detected by the observing facilities worldwide. The source also showed a high and variable optical polarization based on which it was proposed to be a low-energy peaked BL Lac object (LBL). The present work reports first comprehensive multi-wavelength study of this source using data in the radio, optical, UV, X- and γ-rays, and optical polarization. Using these multi-wavelength data on the source, we have estimated various parameters and verified its classification vis-a-vis blazar sequence. Multi-waveband light curves are used to discuss the flaring events of 2011 January in an attempt to address the nature of the source and pinpoint the possible physical processes responsible for the emission. The light curves show variations in the high-energy γ-rays to be correlated with X-ray, UV, and optical variations, perhaps indicating their co-spatial origin. Our optical data, quasi-simultaneous with UV (Swift-UVOT) and X-ray (Swift-XRT) data, enabled us to trace the low-energy (synchrotron) component of the spectral energy distribution (SED) for CGRaBS J0211+1051 for the first time. The SED shows the synchrotron peak to lie at ~1.35 × 1014 Hz, confirming that CGRaBS J0211+1051 is an LBL. Some other parameters, such as the local magnetic field (~5.93 G) and black hole mass (~2.4 × 108 M ⊙), are also estimated which are in agreement with their typical values for the blazars. Based on the present study, identification of the Fermi/LAT source, 2FGL J0211.2+1050, with its BL Lac counterpart CGRaBS J0211+1051 is confirmed.

  8. 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

  9. 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.

  10. Frequency-Dependent Time Lags in Three Blazars

    NASA Technical Reports Server (NTRS)

    Marscher, Alan P.; Jorstad, Svetlana G.; Aller, Margo F.

    2004-01-01

    The work completed includes the analysis of observations obtained during Cycle 6 of the Rossi X-ray Timing Explorer (RXTE). The project is part of a longer-term, continuing program to study the X-ray emission process in blazars in collaboration with Dr. Ian McHardy (U. of Southampton, UK). The goals of the program are to study the X-ray emission mechanism in blazars 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 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. During RXTE cycle 6, the project was awarded RXTE time to monitor three quasars: PKS 1510-089 two times per week, and 3C 273 and 3C 279 three times per week each. The X-ray data, including those from earlier cycles, were compared with radio measurements obtained 2-3 times per week in the centimeter-wave band with the Michigan radio telescope, monthly imaging observations with the VLBA at 43 GHz, and optical observations obtained at several telescopes around the world. Since it is the long-term X-ray light curve that is of greatest value, this report includes discussion of all the data collected through August 2003 rather than just the Cycle 6 data.

  11. Detection of VHE gamma-ray emission from the distant blazar 1ES 1101-232 with HESS and broadband characterisation

    NASA Astrophysics Data System (ADS)

    Aharonian, F.; Akhperjanian, A. G.; Bazer-Bachi, A. R.; Beilicke, M.; Benbow, W.; Berge, D.; Bernlöhr, K.; Boisson, C.; Bolz, O.; Borrel, V.; Braun, I.; Brion, E.; Brown, A. M.; Bühler, R.; Büsching, I.; Boutelier, T.; Carrigan, S.; Chadwick, P. M.; Chounet, L.-M.; Coignet, G.; Cornils, R.; Costamante, L.; Degrange, B.; Dickinson, H. J.; Djannati-Ataï, A.; O'C. Drury, L.; Dubus, G.; Egberts, K.; Emmanoulopoulos, D.; Espigat, P.; Farnier, C.; Feinstein, F.; Ferrero, E.; Fiasson, A.; Fontaine, G.; Funk, Seb.; Funk, S.; Füßling, M.; Gallant, Y. A.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Goret, P.; Hadjichristidis, C.; Hauser, D.; Hauser, M.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Holleran, M.; Hoppe, S.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Kendziorra, E.; Kerschhaggl, M.; Khélifi, B.; Komin, Nu.; Kosack, K.; Lamanna, G.; Latham, I. J.; Le Gallou, R.; Lemière, A.; Lemoine-Goumard, M.; Lohse, T.; Martin, J. M.; Martineau-Huynh, O.; Marcowith, A.; Masterson, C.; Maurin, G.; McComb, T. J. L.; Moulin, E.; de Naurois, M.; Nedbal, D.; Nolan, S. J.; Noutsos, A.; Olive, J.-P.; Orford, K. J.; Osborne, J. L.; Panter, M.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Pühlhofer, G.; Punch, M.; Ranchon, S.; Raubenheimer, B. C.; Raue, M.; Rayner, S. M.; Ripken, J.; Rob, L.; Rolland, L.; Rosier-Lees, S.; Rowell, G.; Sahakian, V.; Santangelo, A.; Saugé, L.; Schlenker, S.; Schlickeiser, R.; Schröder, R.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Shalchi, A.; Sol, H.; Spangler, D.; Spanier, F.; Steenkamp, R.; Stegmann, C.; Superina, G.; Tam, P. H.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Vincent, P.; Völk, H. J.; Wagner, S. J.; Ward, M.

    2007-08-01

    Context: The blazar 1ES 1101-232 was observed with the High Energy Stereoscopic System (HESS) of Atmospheric Cherenkov Telescopes (ACT) in 2004 and 2005, for a live time of 43 h. VHE (E > 1011 eV) γ-rays were detected for the first time from this object. Aims: VHE observations of blazars are used to investigate the inner parts of the blazar jets, and also to study the extragalactic background light (EBL) in the near-infrared band. Methods: Observations in 2005 were conducted in a multiwavelength campaign, together with the RXTE satellite and optical observations. In 2004, simultaneous observations with XMM-Newton were obtained. Results: 1ES 1101-232 was detected with HESS with an excess of 649 photons, at a significance of 10σ. The measured VHE γ-ray flux amounts to dN/dE = (5.63 ± 0.89) × 10-13 (E/TeV)-(2.94±0.20) cm-2 s-1 TeV-1, above a spectral energy threshold of 225 GeV. No significant variation of the VHE γ-ray flux on any time scale was found. 1ES 1101-232 exhibits a very hard spectrum, and at a redshift of z = 0.186, is the blazar with the highest confirmed redshift detected in VHE γ-rays so far. Conclusions: The data allow the construction of truly simultaneous spectral energy distributions of the source, from the optical to the VHE band. Using an EBL model with ν Fν = 14 nWm-2 sr-1 at 1.5~μm as presented in Aharonian et al. (2006a) suggests an intrinsic VHE power output peak of the source at above 3 TeV.

  12. NIR flaring of the blazar OJ248

    NASA Astrophysics Data System (ADS)

    Carrasco, L.; Carramiñana, A.; Recillas, E.; Porras, A.; Valdes, J. R.; Escobedo, G.; Torres, I.

    2010-09-01

    We report on our recent observation of the blazar OJ248 also known as 3EGJ0829+2413 and B2 0827+24 with the CANICA NIR camera on the 2.1m telescope at the Observatorio Astrofísico Guillermo Haro, located in Cananea, Mexico. On September 30th, 2010 (JD245554569.9898), we found this source to be in outburst. On this date the source was found to have a flux corresponding to H = 14.59 +/- 0.02, J=15.29 +/- 0.04 and Ks = 13.72 +/- 0.06.

  13. Mrk 421 and other blazars at 60 GeV

    NASA Astrophysics Data System (ADS)

    Smith, David

    2002-04-01

    The CELESTE gamma ray telescope collects atmospheric Cherenkov light using 53 heliostats of the former solar facility "Themis", in the French Pyrennees. The CAT Cherenkov imager operates at the same site.We present measurements of the flux from Mrk 421 obtained with both instruments in March 2000 which we use to constrain the Inverse Compton peak of this blazar's spectral energy distribution. Combining this information with BeppoSAX measurements of the synchrotron peak position allows us to constrain the physical parameters of the blazar in a simple Synchrotron Self Compton framework. We further present the results of searches for other blazars in this previously unexplored energy range.

  14. 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.

  15. 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.

  16. Expanding the Gamma-ray Universe: High Redshift Fermi-LAT Blazars

    NASA Astrophysics Data System (ADS)

    Ojha, Roopesh; Paliya, Vaidehi; Gasparrini, Dario; Ajello, Marco; Cutini, Sara; Fermi-LAT Collaboration

    2017-01-01

    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 Fermi-LAT sample. These blazars appear to host very massive black holes and could shed light on the origin and growth of black holes in the early Universe. We present the latest high redshift blazar detections in the LAT and discuss some of their implications.

  17. The Fermi blazars' divide based on the diagnostic of the SEDs peak frequencies

    NASA Astrophysics Data System (ADS)

    Tramacere, A.; Cavazzuti, E.; Giommi, P.; Mazziotta, N.; Monte, C.

    2010-03-01

    We have studied the quasi-simultaneous Spectral Energy Distributions (SED) of 48 LBAS blazars, detected within the three months of the LAT Bright AGN Sample (LBAS) data taking period, combining Fermi and Swift data with radio NIR-Optical and hard- X/gamma-ray data. Using these quasi-simultaneous SEDs, sampling both the low and the high energy peak of the blazars broad band emission, we were able to apply a diagnostic tool based on the estimate of the peak frequencies of the synchrotron (S) and Inverse Compton (IC) components. Our analysis shows a Fermi blazar's divide based on the peak frequencies of the SED. The robust result is that the Synchrotron Self Compton (SSC) region divides in two the νpS-γpSSC plane. Objects within or below this region, radiating likely via the SSC process, are high-frequency-peaked BL Lac object (HBL), or low/intermediate-frequency-peaked BL Lac object (LBL/IBL). All of the IBLs/LBLs within or below the SSC region are not Compton dominated. The objects lying above the SSC region, radiating likely via the External radiation Compton (ERC) process, are Flat Spectrum Radio Quasars and IBLs/LBLs. All of the IBLs/LBLs in the ERC region show a significant Compton dominance.

  18. 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.

  19. Non-coincident multi-wavelength emission absorption spectroscopy

    SciTech Connect

    Baumann, L.E.

    1995-02-01

    An analysis is presented of the effect of noncoincident sampling on the measurement of atomic number density and temperature by multiwavelength emission absorption. The assumption is made that the two signals, emission and transmitted lamp, are time resolved but not coincident. The analysis demonstrates the validity of averages of such measurements despite fluctuations in temperature and optical depth. At potassium-seeded MHD conditions, the fluctuations introduce additional uncertainty into measurements of potassium atom number density and temperature but do not significantly bias the average results. Experimental measurements in the CFFF aerodynamic duct with coincident and noncoincident sampling support the analysis.

  20. Gamma-ray blazar spectra with H.E.S.S. II mono analysis: The case of PKS 2155-304 and PG 1553+113

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abdalla, H.; Abramowski, A.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Andersson, T.; Angüner, E. O.; Arrieta, M.; Aubert, P.; Backes, M.; Balzer, A.; Barnard, M.; Becherini, Y.; Becker Tjus, J.; Berge, D.; Bernhard, S.; Bernlöhr, K.; Blackwell, R.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brun, F.; Brun, P.; Bryan, M.; Bulik, T.; Capasso, M.; Carr, J.; Casanova, S.; Cerruti, M.; Chakraborty, N.; Chalme-Calvet, R.; Chaves, R. C. G.; Chen, A.; Chevalier, J.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Condon, B.; Conrad, J.; Couturier, C.; Cui, Y.; Davids, I. D.; Degrange, B.; Deil, C.; Devin, J.; deWilt, P.; Dirson, L.; Djannati-Ataï, A.; Domainko, W.; Donath, A.; Drury, L. O.'C.; Dubus, G.; Dutson, K.; Dyks, J.; Edwards, T.; Egberts, K.; Eger, P.; Ernenwein, J.-P.; Eschbach, S.; Farnier, C.; Fegan, S.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Funk, S.; Füßling, M.; Gabici, S.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giavitto, G.; Giebels, B.; Glicenstein, J. F.; Gottschall, D.; Goyal, A.; Grondin, M.-H.; Hadasch, D.; Hahn, J.; Haupt, M.; Hawkes, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hoischen, C.; Holler, M.; Horns, D.; Ivascenko, A.; Jacholkowska, A.; Jamrozy, M.; Janiak, M.; Jankowsky, D.; Jankowsky, F.; Jingo, M.; Jogler, T.; Jouvin, L.; Jung-Richardt, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kerszberg, D.; Khélifi, B.; Kieffer, M.; King, J.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Kraus, M.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lau, J.; Lees, J.-P.; Lefaucheur, J.; Lefranc, V.; Lemière, A.; Lemoine-Goumard, M.; Lenain, J.-P.; Leser, E.; Lohse, T.; Lorentz, M.; Liu, R.; López-Coto, R.; Lypova, I.; Marandon, V.; Marcowith, A.; Mariaud, C.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; Meintjes, P. J.; Meyer, M.; Mitchell, A. M. W.; Moderski, R.; Mohamed, M.; Mohrmann, L.; Morå, K.; Moulin, E.; Murach, T.; de Naurois, M.; Niederwanger, F.; Niemiec, J.; Oakes, L.; O'Brien, P.; Odaka, H.; Öttl, S.; Ohm, S.; Ostrowski, M.; Oya, I.; Padovani, M.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perennes, C.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Prokhorov, D.; Prokoph, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Romoli, C.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Salek, D.; Sanchez, D. A.; Santangelo, A.; Sasaki, M.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwemmer, S.; Settimo, M.; Seyffert, A. S.; Shafi, N.; Shilon, I.; Simoni, R.; Sol, H.; Spanier, F.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Tavernet, J.-P.; Tavernier, T.; Taylor, A. M.; Terrier, R.; Tibaldo, L.; Tiziani, D.; Tluczykont, M.; Trichard, C.; Tuffs, R.; Uchiyama, Y.; van der Walt, D. J.; van Eldik, C.; van Soelen, B.; Vasileiadis, G.; Veh, J.; Venter, C.; Viana, A.; Vincent, P.; Vink, J.; Voisin, F.; Völk, H. J.; Vuillaume, T.; Wadiasingh, Z.; Wagner, S. J.; Wagner, P.; Wagner, R. M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Yang, R.; Zabalza, V.; Zaborov, D.; Zacharias, M.; Zdziarski, A. A.; Zech, A.; Zefi, F.; Ziegler, A.; Żywucka, N.; LAT Collaboration; Ackermann, M.; Ajello, M.; Baldini, L.; Barbiellini, G.; Bellazzini, R.; Blandford, R. D.; Bonino, R.; Bregeon, J.; Bruel, P.; Buehler, R.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Chiang, J.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Costanza, F.; Cutini, S.; D'Ammando, F.; de Palma, F.; Desiante, R.; Di Lalla, N.; Di Mauro, M.; Di Venere, L.; Donaggio, B.; Favuzzi, C.; Focke, W. B.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Guillemot, L.; Guiriec, S.; Horan, D.; Jóhannesson, G.; Kamae, T.; Kensei, S.; Kocevski, D.; Larsson, S.; Li, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Maldera, S.; Manfreda, A.; Mazziotta, M. N.; Michelson, P. F.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Negro, M.; Nuss, E.; Orienti, M.; Orlando, E.; Paneque, D.; Perkins, J. S.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Principe, G.; Rainò, S.; Razzano, M.; Simone, D.; Siskind, E. J.; Spada, F.; Spinelli, P.; Thayer, J. B.; Torres, D. F.; Torresi, E.; Troja, E.; Vianello, G.; Wood, K. S.

    2017-04-01

    Context. The addition of a 28 m Cherenkov telescope (CT5) to the H.E.S.S. array extended the experiment's sensitivityto lower energies. The lowest energy threshold is obtained using monoscopic analysis of data taken with CT5, providing access to gamma-ray energies below 100 GeV for small zenith angle observations. Such an extension of the instrument's energy range is particularly beneficial for studies of active galactic nuclei with soft spectra, as expected for those at a redshift ≥0.5. The high-frequency peaked BL Lac objects PKS 2155-304 (z = 0.116) and PG 1553+113 (0.43 < z < 0.58) are among the brightest objects in the gamma-ray sky, both showing clear signatures of gamma-ray absorption at E > 100 GeV interpreted as being due to interactions with the extragalactic background light (EBL). Aims: The aims of this work are twofold: to demonstrate the monoscopic analysis of CT5 data with a low energy threshold, and to obtain accurate measurements of the spectral energy distributions (SED) of PKS 2155-304 and PG 1553+113 near their SED peaks at energies ≈100 GeV. Methods: Multiple observational campaigns of PKS 2155-304 and PG 1553+113 were conducted during 2013 and 2014 using the full H.E.S.S. II instrument (CT1-5). A monoscopic analysis of the data taken with the new CT5 telescope was developed along with an investigation into the systematic uncertainties on the spectral parameters which are derived from this analysis. Results: Using the data from CT5, the energy spectra of PKS 2155-304 and PG 1553+113 were reconstructed down to conservative threshold energies of 80 GeV for PKS 2155-304, which transits near zenith, and 110 GeV for the more northern PG 1553+113. The measured spectra, well fitted in both cases by a log-parabola spectral model (with a 5.0σ statistical preference for non-zero curvature for PKS 2155-304 and 4.5σ for PG 1553+113), were found consistent with spectra derived from contemporaneous Fermi-LAT data, indicating a sharp break in the

  1. Implications for High Energy Blazar Spectra from Intergalactic Absorption Calculations

    NASA Technical Reports Server (NTRS)

    Stecker, F

    2008-01-01

    Given a knowledge of the density spectra intergalactic low energy photons as a function of redshift, one can derive the intrinsic gamma-ray spectra and luminosities of blazars over a range of redshifts and look for possible trends in blazar evolution. Stecker, Baring & Summerlin have found some evidence hinting that TeV blazars with harder spectra have higher intrinsic TeV gamma-ray luminosities and indicating that there may be a correlation of spectral hardness and luminosity with redshift. Further work along these lines, treating recent observations of the blazers lES02291+200 and 3C279 in the TeV and sub-TeV energy ranges, has recently been explored by Stecker & Scully. GLAST will observe and investigate many blazars in the GeV energy range and will be sensitive to blazers at higher redshifts. I examine the implications high redshift gamma-ray absorption for both theoretical and observational blazer studies.

  2. 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.

  3. 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.

  4. 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.

  5. 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.

  6. 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.

  7. Is the Blazar Sequence related to accretion disk winds?

    NASA Astrophysics Data System (ADS)

    Boula, Stella; Mastichiadis, Apostolos; Kazanas, Demosthenes

    2016-08-01

    Adopting the hypothesis that the nonthermal emission of blazars is primarily due to the acceleration of electrons, we construct a simple leptonic model in order to explain the Blazar Sequence. The acceleration process is assumed to be of the first order Fermi type and the injected electrons and photons in the emitting region of the blazar are described by spatially averaged kinetic equations. According to the leptonic scenario, the spectral energy distributions of blazars have two basic components: a low frequency component, peaking in the optical through X-rays, from synchrotron emission; and a high frequency one, peaking in the γ rays, probably originating from Compton scattering of some seed photon source, either internal (synchrotron self-Compton) and/or external to the jet (external Compton). We find an adequate description of the Blazar Sequence by assuming a wind density profile of the form n(r) 1/r. Higher luminosity objects have higher accretion rates, higher optical thicknesses of the wind to Compton scattering and thus higher external photon fields than the lower luminosity ones. Therefore, we present indicative Blazar Sequence models which reproduce the basic observational trends just by varying one parameter, namely the mass accretion rate dot{m}.

  8. 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.

  9. 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.

  10. 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.

  11. 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.

  12. Interferometric multiwavelength system for long gauge blocks measurements

    NASA Astrophysics Data System (ADS)

    Wengierow, Michal; Sałbut, Leszek; Ramotowski, Zbigniew

    2011-05-01

    This paper describes common efforts of Warsaw University of Technology and Polish Central Office of Measure to build a multiwavelength interferometer with extended measurement range to calibrate long gauge blocks. To achieve this goal modified automatic fringe pattern analysis method based on fringe fraction method is proposed. The setup with special chamber with active temperature control to stabilize environmental conditions has been build. To assure correctness of measure factors like temperature, pressure, humidity and concentration of CO2 are need to be constantly monitored by network of sensors. Summarizing all this efforts we are presenting gauge blocks calibration results with uncertainty analysis.

  13. 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.

  14. Detecting the elusive blazar counter-jets

    NASA Astrophysics Data System (ADS)

    Liodakis, I.; Pavlidou, V.; Angelakis, E.

    2017-02-01

    Detection of blazar pc scale counter-jets is difficult, but it can provide invaluable insight into the relativistic effects, radiative processes and the complex mechanisms of jet production, collimation and accelation in blazars. We build on recent populations models (optimized using the MOJAVE apparent velocity and redshift distributions) in order to derive the distribution of jet-to-counter-jet ratios and the flux densities of the counter-jet at different frequencies, in an effort to set minimum sensitivity limits required for existing and future telescope arrays in order to detect these elusive counter-jets. We find that: for the BL Lacs, 5 per cent of their counter-jets have a flux density higher than 100 mJy, 15 per cent are higher than 10 mJy, and 32 per cent have higher flux density than 1 mJy, whereas for the FSRQs, 8 per cent have a flux density higher than 10 mJy, 17 per cent are higher than 1 mJy, and 32 per cent are higher than 0.1 mJy (at 15 GHz). Future telescopes like the SKA and newly operating like e-MERLIN and JVLA may detect up to 99 per cent of the BL Lac and 77 per cent of the FSRQ counter-jets. Sources with both low apparent velocity and a low Doppler factor make prime candidates for counter-jet detection. Combining our findings with the literature values, we have identified five such counter-jet detection candidates. Finally, we discuss possible effects beyond relativistic deboosting that may complicate the detection of counter-jets and that need to be accounted for in the interpretation of detections.

  15. Gamma-Ray Blazars within the First 2 Billion Years

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; 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.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Cheung, C. C.; Chiang, J.; Chiaro, G.; Ciprini, S.; Conrad, J.; Costantin, D.; Costanza, F.; Cutini, S.; D’Ammando, F.; de Palma, F.; Desiante, R.; Digel, S. W.; Di Lalla, N.; Di Mauro, M.; Di Venere, L.; Domínguez, A.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Finke, J.; Focke, W. B.; Fukazawa, Y.; Funk, S.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Green, D.; Grenier, I. A.; Guillemot, L.; Guiriec, S.; Hartmann, D. H.; Hays, E.; Horan, D.; Jogler, T.; Jóhannesson, G.; Johnson, A. S.; Kuss, M.; La Mura, G.; Larsson, S.; Latronico, L.; Li, J.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J. D.; Maldera, S.; Manfreda, A.; Marcotulli, L.; Mazziotta, M. N.; Michelson, P. F.; Mirabal, N.; Mitthumsiri, W.; Mizuno, T.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Negro, M.; Nuss, E.; Ohsugi, T.; Ojha, R.; Omodei, N.; Orienti, M.; Orlando, E.; Ormes, J. F.; Paliya, V. S.; Paneque, D.; Perkins, J. S.; Persic, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Principe, G.; Rainò, S.; Rando, R.; Rani, B.; Razzano, M.; Razzaque, S.; Reimer, A.; Reimer, O.; Romani, R. W.; Sgrò, C.; Simone, D.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Stalin, C. S.; Stawarz, L.; Suson, D. J.; Takahashi, M.; Tanaka, K.; Thayer, J. B.; Thompson, D. J.; Torres, D. F.; Torresi, E.; Tosti, G.; Troja, E.; Vianello, G.; Wood, K. S.

    2017-03-01

    The detection of high-redshift (z > 3) blazars enables the study of the evolution of the most luminous relativistic jets over cosmic time. More importantly, high-redshift blazars tend to host massive black holes and can be used to constrain the space density of heavy black holes in the early universe. Here, we report the first detection with the Fermi-Large Area Telescope of five γ-ray-emitting blazars beyond z = 3.1, more distant than any blazars previously detected in γ-rays. Among these five objects, NVSS J151002+570243 is now the most distant known γ-ray-emitting blazar at z = 4.31. These objects have steeply falling γ-ray spectral energy distributions (SEDs), and those that have been observed in X-rays have a very hard X-ray spectrum, both typical of powerful blazars. Their Compton dominance (ratio of the inverse Compton to synchrotron peak luminosities) is also very large (> 20). All of these properties place these objects among the most extreme members of the blazar population. Their optical spectra and the modeling of their optical-UV SEDs confirm that these objects harbor massive black holes ({M}{BH}∼ {10}8-10 {M}ȯ ). We find that, at z≈ 4, the space density of > {10}9 {M}ȯ black holes hosted in radio-loud and radio-quiet active galactic nuclei are similar, implying that radio-loudness may play a key role in rapid black hole growth in the early universe.

  16. 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

  17. 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.

  18. The WEBT Campaign on the Blazar 3C 279 in 2006

    NASA Astrophysics Data System (ADS)

    Böttcher, M.; Basu, S.; Joshi, M.; Villata, M.; Arai, A.; Aryan, N.; Asfandiyarov, I. M.; Bach, U.; Bachev, R.; Berduygin, A.; Blaek, M.; Buemi, C.; Castro-Tirado, A. J.; De Ugarte Postigo, A.; Frasca, A.; Fuhrmann, L.; Hagen-Thorn, V. A.; Henson, G.; Hovatta, T.; Hudec, R.; Ibrahimov, M.; Ishii, Y.; Ivanidze, R.; Jelínek, M.; Kamada, M.; Kapanadze, B.; Katsuura, M.; Kotaka, D.; Kovalev, Y. Y.; Kovalev, Yu. A.; Kubánek, P.; Kurosaki, M.; Kurtanidze, O.; Lähteenmäki, A.; Lanteri, L.; Larionov, V. M.; Larionova, L.; Lee, C.-U.; Leto, P.; Lindfors, E.; Marilli, E.; Marshall, K.; Miller, H. R.; Mingaliev, M. G.; Mirabal, N.; Mizoguchi, S.; Nakamura, K.; Nieppola, E.; Nikolashvili, M.; Nilsson, K.; Nishiyama, S.; Ohlert, J.; Osterman, M. A.; Pak, S.; Pasanen, M.; Peters, C. S.; Pursimo, T.; Raiteri, C. M.; Robertson, J.; Robertson, T.; Ryle, W. T.; Sadakane, K.; Sadun, A.; Sigua, L.; Sohn, B.-W.; Strigachev, A.; Sumitomo, N.; Takalo, L. O.; Tamesue, Y.; Tanaka, K.; Thorstensen, J. R.; Tosti, G.; Trigilio, C.; Umana, G.; Vennes, S.; Vitek, S.; Volvach, A.; Webb, J.; Yamanaka, M.; Yim, H.-S.

    2007-12-01

    The quasar 3C 279 was the target of an extensive multiwavelength monitoring campaign from 2006 January through April. An optical-IR-radio monitoring campaign by the Whole Earth Blazar Telescope (WEBT) collaboration was organized around target-of-opportunity X-ray and soft γ-ray observations with Chandra and INTEGRAL in 2006 mid-January, with additional X-ray coverage by RXTE and Swift XRT. In this paper we focus on the results of the WEBT campaign. The source exhibited substantial variability of optical flux and spectral shape, with a characteristic timescale of a few days. The variability patterns throughout the optical BVRI bands were very closely correlated with each other, while there was no obvious correlation between the optical and radio variability. After the ToO trigger, the optical flux underwent a remarkably clean quasi-exponential decay by about 1 mag, with a decay timescale of τd~12.8 days. In intriguing contrast to other (in particular, BL Lac type) blazars, we find a lag of shorter wavelength behind longer wavelength variability throughout the RVB wavelength ranges, with a time delay increasing with increasing frequency. Spectral hardening during flares appears delayed with respect to a rising optical flux. This, in combination with the very steep IR-optical continuum spectral index of α0~1.5-2.0, may indicate a highly oblique magnetic field configuration near the base of the jet, leading to inefficient particle acceleration and a very steep electron injection spectrum. An alternative explanation through a slow (timescale of several days) acceleration mechanism would require an unusually low magnetic field of B<~0.2 G, about an order of magnitude lower than inferred from previous analyses of simultaneous SEDs of 3C 279 and other flat-spectrum radio quasars with similar properties. For questions regarding the availability of the data from the WEBT campaign presented in this paper, please contact the WEBT President Massimo Villata at villata@oato.inaf.it.

  19. 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

  20. 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

  1. Frequency-dependent core shifts and parameter estimation in Blazars

    NASA Astrophysics Data System (ADS)

    Agarwal, Aditi

    2016-07-01

    We study the core shift effect in the parsec-scale jet of blazars using the 4.8-36.8 GHz radio light curves obtained from four decades of continuous monitoring. From a piecewise Gaussian fit to each flare, time lags between the observation frequencies and spectral indices (α) based on peak amplitudes (A) are determined. Index k is calculated and found to be ˜1, indicating equipartition between the magnetic field energy density and the particle energy density. A mean magnetic field strength at 1 pc (B1) and at the core (Bcore) are inferred which are found to be consistent with previous estimates. The measure of core position offset is also performed by averaging over all frequency pairs. Based on the statistical trend shown by the measured core radius as a function of frequency, we infer that the synchrotron opacity model may not be valid for all cases. A Fourier periodogram analysis yields power-law slopes in the range -1.6 to -3.5 describing the power spectral density shape and gives bend timescales. This result, and both positive and negative spectral indices, indicate that the flares originate from multiple shocks in a small region. Important objectives met in our study include: the demonstration of the computational efficiency and statistical basis of the piecewise Gaussian fit; consistency with previously reported results; evidence for the core shift dependence on observation frequency and its utility in jet diagnostics in the region close to the resolving limit of very long baseline interferometry observations.

  2. 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.

  3. VERY HIGH ENERGY γ-RAYS FROM THE UNIVERSE’S MIDDLE AGE: DETECTION OF THE z = 0.940 BLAZAR PKS 1441+25 WITH MAGIC

    SciTech Connect

    Ahnen, M. L.; Biland, A.; Ansoldi, S.; Biasuzzi, B.; Antonelli, L. A.; Bonnoli, G.; Carosi, A.; Antoranz, P.; Babic, A.; Banerjee, B.; Bangale, P.; Almeida, U. Barres de; Borracci, F.; Barrio, J. A.; Bonnefoy, S.; Bednarek, W.; Bernardini, E.; Blanch, O.; Bretz, T.; Carmona, E. E-mail: miguelnievas@ucm.es E-mail: josefa.becerra@nasa.gov; Collaboration: MAGIC Collaboration; Fermi-LAT Collaboration; and others

    2015-12-20

    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.

  4. Roma-BZCAT: a multifrequency catalogue of blazars

    NASA Astrophysics Data System (ADS)

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

    2009-02-01

    We present a new catalogue of blazars based on multifrequency surveys and on an extensive review of the literature. Blazars are classified as BL Lacertae objects, as flat spectrum radio quasars or as blazars of uncertain/transitional type. Each object is identified by a root name, coded as BZB, BZQ and BZU for these three subclasses respectively, and by its coordinates. This catalogue is being built as a tool useful for the identification of the extragalactic sources that will be detected by present and future experiments for X and gamma-ray astronomy, like Swift, AGILE, Fermi-GLAST and Simbol-X. An electronic version is available from the ASI Science Data Center web site at http://www.asdc.asi.it/bzcat.

  5. 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.

  6. High-energy Neutrinos from Recent Blazar Flares

    NASA Astrophysics Data System (ADS)

    Halzen, Francis; Kheirandish, Ali

    2016-11-01

    The energy density of cosmic neutrinos measured by IceCube matches the one observed by Fermi in extragalactic photons that predominantly originate in blazars. This has inspired attempts to match Fermi sources with IceCube neutrinos. A spatial association combined with a coincidence in time with a flaring source may represent a smoking gun for the origin of the IceCube flux. In 2015 June, the Fermi Large Area Telescope observed an intense flare from blazar 3C 279 that exceeded the steady flux of the source by a factor of 40 for the duration of a day. We show that IceCube is likely to observe neutrinos, if indeed hadronic in origin, in data that are still blinded at this time. We also discuss other opportunities for coincident observations that include a recent flare from blazar 1ES 1959+650 that previously produced an intriguing coincidence with AMANDA observations.

  7. 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.

  8. NIR flaring of the blazar PKS0048-097

    NASA Astrophysics Data System (ADS)

    Carrasco, L.; Carramiñana, A.; Recillas, E.; Porras, A.; Escobedo, G.; Mayya, Y. D.; Valdes, J. R.

    2011-01-01

    We call attention on our recent NIR observations of the gamma ray source 1FGL J0050.6-0928, an intermediate redshift Blazar PKS0048-097 (z=0.634), also known as FBQS J0050-0929. The observations were carried out with the CANICA NIR camera on the 2.1m telescope at the Observatorio Astrofísico Guillermo Haro, located in Cananea, Mexico. We found this blazar to be in outburst. It shows fluxes about 1.7 magnitudes brighter than our previous NIR photometry (JD2455450.944784, H = 14.427 ± 0.11).

  9. Initial Blazar Studies with the CELESTE Cherenkov Telescope

    NASA Astrophysics Data System (ADS)

    Münz, F.

    1999-08-01

    CELESTE began systematic blazar observations in March 1999 with a 40-heliostat array at the site of the solar array at Themis in the French Pyrenees. Data is recorded using 1 GHz Flash ADC's which allow faint Cherenkov pulses to be measured. The hybrid analog-logic trigger scheme provides good hadron rejection and high efficiency for low-energy showers. A trigger threshold below 50 GeV allows CELESTE to probe the region near the peak of the inverse compton spectrum observed in many blazars. In this first observation campaign we are concentrating on Mrk 421, Mrk 501, and 1ES 1426+428.

  10. 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.

  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. 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

  13. Long-term optical variability properties of blazars in the SDSS Stripe 82

    NASA Astrophysics Data System (ADS)

    Mao, Lisheng; Zhang, Xuemei

    2016-10-01

    The temporal and spectral variabilities of 31 blazars are investigated using the multi-epoch photometric data released in the Sloan Digital Sky Survey (SDSS) Stripe 82. The performed chi-square tests indicate that all the objects show significant brightness variabilities in the Stripe 82 observational period. Two analysis methods, Spearman correlation analysis and linear regression taking into account measurement errors in both the dependent and independent variable, are combined to probe the spectral variability characteristics. As a result, 21 out of 31 blazars exhibit a significant bluer-when-brighter (BWB) trend, which is at least partly attributed to the effect of larger variability amplitude at higher frequencies. Our analysis shows that the BWB trend generally exists for the optical emission of BL Lacs on long time scales. Meanwhile, there are two sources (SDSS J211817.39+001316.8, SDSS J231000.83-000516.2) showing the opposite behavior, i.e., redder-when-brighter (RWB) trend, which might be attributed to the contribution of thermal emission from the accretion disk. Moreover, it is tentatively found that BL Lacs tend to show larger-amplitude brightness variability but smaller-amplitude spectral index variability with respect to FSRQs, implying that there are different physical conditions in these two populations.

  14. 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.

  15. 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.

  16. 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.

  17. Constraints on cosmic ray and PeV neutrino production in blazars

    NASA Astrophysics Data System (ADS)

    Zhang, B. Theodore; Li, Zhuo

    2017-03-01

    IceCube has detected a cumulative flux of PeV neutrinos, which origin is unknown. Blazars, active galactic nuclei with relativistic jets pointing to us, are long and widely expected to be one of the strong candidates of high energy neutrino sources. The neutrino production depends strongly on the cosmic ray power of blazar jets, which is largely unknown. The recent null results in stacking searches of neutrinos for several blazar samples by IceCube put upper limits on the neutrino fluxes from these blazars. Here we compute the cosmic ray power and PeV neutrino flux of Fermi-LAT blazars, and find that the upper limits for known blazar sources give stringent constraint on the cosmic ray loading factor of blazar jets (i.e., the ratio of the cosmic ray to bolometric radiation luminosity of blazar jets), ξcr lesssim (2–10)ζ‑1 (with ζ lesssim 1 the remained fraction of cosmic ray energy when propagate into the blazar broad line region) for flat cosmic ray spectrum, and that the cumulative PeV neutrino flux contributed by all-sky blazars is a fraction lesssim (10–50)% of the IceCube detected flux.

  18. 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

  19. Violent optical activity of the blazar OJ 287

    NASA Astrophysics Data System (ADS)

    Larionov, V.; Mokrushina, A. A.; Grishina, T. S.

    2016-10-01

    We perform optical photometric and polarimetric monitoring of a sample of gamma-bright blazars using 0.7-m AZT-8 telescope (Crimean Astrophysical Observatory) and 0.4-m LX-200 telescope (St.Petersburg), as a part of WEBT/GASP project.

  20. The core dominance parameter for gamma-ray loud blazars

    NASA Astrophysics Data System (ADS)

    Pei, Z. Y.; Fan, J. H.; Liu, Y.; Xie, H. J.; Gao, Y.; Lin, C.

    2015-03-01

    In this work, we compiled 604 blazars with available core-dominance parameter, out of which 149 blazars are known to have γ-ray emissions. We compared the logR between the 149 Fermi-detected blazars (FDB) and the rest non-Fermi-detected blazars (non-FDB), and found that the average values are < log R > = 1.12 +/- 0.88 for FDBs and < log R > = 0.05 +/- 0.94 for non-FDBs. A K-S test shows that the probability for the distributions of FDB and non-FDB to come from the same parent distribution is P = 2.38 × 10-7. We also investigated the correlation between the core-dominance parameters and the γ-ray emission variability index (VI) for 125 FDBs (45 BLs and 79 FSRQs), and found that there is a tendency for VI to increase with the core-dominance parameter for 79 FSRQs, but there is no such tendency for 46 BLs.

  1. High-redshift Fermi blazars observed by GROND and Swift

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Nardini, M.; Tagliaferri, Greiner, J.; Schady, P.; Rau, A.; Foschini, L.; Tavecchio, F.; Ghirlanda, G.; Sbarrato, T.

    2013-01-01

    We observed five γ-ray-loud blazars at redshift greater than 2 with the X-Ray Telescope (XRT) and the UltraViolet and Optical Telescope (UVOT) on-board the Swift satellite, and the Gamma-Ray burst Optical Near-Infrared Detector (GROND) instrument. These observations were quasi-simultaneous, usually within a few hours. For four of these blazars, the near-IR to UV data show the presence of an accretion disc, and we could reliably estimate its accretion rate and black hole mass. One of them, PKS 1348+007, was found in an extraordinarily high IR-optical state, almost two orders of magnitude brighter than at the epoch of the Sloan Digital Sky Survey observations. For all the five quasars, the physical parameters of the jet-emitting zone, derived by applying a one-zone emission model, are similar to that found for the bulk of other γ-ray-loud quasars. With our observations, we have X-ray data for the full sample of blazars at z > 2 present in the Fermi 2-year (2LAC) catalogue. This allows us to have a rather complete view of the spectral energy distribution of all high-redshift Fermi blazars, and to draw some conclusions about their properties, and especially about the relation between the accretion rate and the jet power.

  2. 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.

  3. IDENTIFICATION OF THE INFRARED NON-THERMAL EMISSION IN BLAZARS

    SciTech Connect

    Massaro, F.; Ajello, M.; D'Abrusco, R.; Grindlay, J. E.; Smith, Howard A.

    2011-10-20

    Blazars constitute the most interesting and enigmatic class of extragalactic {gamma}-ray sources dominated by non-thermal emission. In this Letter, we show how the Wide Infrared Survey Explorer (WISE) infrared data make it possible to identify a distinct region of the [3.4]-[4.6]-[12] {mu}m color-color diagram where the sources dominated by the thermal radiation are separated from those dominated by non-thermal emission, in particular the blazar population. This infrared non-thermal region, which we indicate as the WISE blazar strip (WBS), will constitute a new powerful diagnostic tool when the full WISE survey data are released. The WBS can be used to extract new blazar candidates, to identify those of uncertain type and also to search for the counterparts of unidentified {gamma}-ray sources. We show one example of the value of the use of the WBS identifying the TeV source VER J0648+152, recently discovered by VERITAS.

  4. MC2: Multiwavelength and Dynamical Analysis of the Merging Galaxy Cluster ZwCl 0008.8+5215: An Older and Less Massive Bullet Cluster

    NASA Astrophysics Data System (ADS)

    Golovich, Nathan; van Weeren, Reinout J.; Dawson, William A.; Jee, M. James; Wittman, David

    2017-04-01

    We present and analyze a rich data set including Subaru/SuprimeCam, HST/Advanced Camera for Surveys and Wide Field Camera 3, Keck/DEIMOS, Chandra/ACIS-I, and JVLA/C and D array for the merging cluster of galaxies ZwCl 0008.8+5215. With a joint Subaru+HST weak gravitational lensing analysis, we identify two dominant subclusters and estimate the masses to be {M}200={5.7}-1.8+2.8× {10}14 {M}ȯ and {1.2}-0.6+1.4× {10}14 {M}ȯ . We estimate the projected separation between the two subclusters to be {924}-206+243 {kpc}. We perform a clustering analysis of spectroscopically confirmed cluster member galaxies and estimate the line-of-sight velocity difference between the two subclusters to be 92+/- 164 {km} {{{s}}}-1. We further motivate, discuss, and analyze the merger scenario through an analysis of the 42 ks of Chandra/ACIS-I and JVLA/C and D array polarization data. The X-ray surface brightness profile reveals a merging gas-core reminiscent of the Bullet Cluster. The global X-ray luminosity in the 0.5–7.0 keV band is 1.7+/- 0.1× {10}44 {erg} {{{s}}}-1 and the global X-ray temperature is 4.90 ± 0.13 keV. The radio relics are polarized up to 40 % , and along with the masses, velocities, and positions of the two subclusters, we input these quantities into a Monte Carlo dynamical analysis and estimate the merger velocity at pericenter to be {1800}-300+400 {km} {{{s}}}-1. This is a lower-mass version of the Bullet Cluster and therefore may prove useful in testing alternative models of dark matter (DM). We do not find significant offsets between DM and galaxies, but the uncertainties are large with the current lensing data. Furthermore, in the east, the BCG is offset from other luminous cluster galaxies, which poses a puzzle for defining DM–galaxy offsets.

  5. Multi-wavelength Observations of the Flaring Gamma-ray Blazar 3C 66A in 2008 October

    NASA Astrophysics Data System (ADS)

    Abdo, A. A.; Ackermann, M.; Ajello, M.; Baldini, L.; Ballet, J.; Barbiellini, G.; Bastieri, D.; Bechtol, K.; Bellazzini, R.; Berenji, B.; Blandford, R. D.; Bonamente, E.; Borgland, A. W.; Bouvier, A.; Bregeon, J.; Brez, A.; Brigida, M.; Bruel, P.; Buehler, R.; Buson, S.; Caliandro, G. A.; Cameron, R. A.; Caraveo, P. A.; Carrigan, S.; Casandjian, J. M.; Cavazzuti, E.; Cecchi, C.; Çelik, Ö.; Charles, E.; Chekhtman, A.; Cheung, C. C.; Chiang, J.; Ciprini, S.; Claus, R.; Cohen-Tanugi, J.; Conrad, J.; Costamante, L.; Cutini, S.; Davis, D. S.; Dermer, C. D.; de Palma, F.; Digel, S. W.; do Couto e Silva, E.; Drell, P. S.; Dubois, R.; Dumora, D.; Favuzzi, C.; Fegan, S. J.; Fortin, P.; Frailis, M.; Fuhrmann, L.; Fukazawa, Y.; Funk, S.; 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.; Grove, J. E.; Guillemot, L.; Guiriec, S.; Hadasch, D.; Hayashida, M.; Hays, E.; Horan, D.; Hughes, R. E.; Itoh, R.; Jóhannesson, G.; Johnson, A. S.; Johnson, T. J.; Johnson, W. N.; Kamae, T.; Katagiri, H.; Kataoka, J.; Knödlseder, J.; Kuss, M.; Lande, J.; Latronico, L.; Lee, S.-H.; Longo, F.; Loparco, F.; Lott, B.; Lovellette, M. N.; Lubrano, P.; Makeev, A.; Mazziotta, M. N.; McEnery, J. E.; Mehault, J.; Michelson, P. F.; Mizuno, T.; Moiseev, A. A.; Monte, C.; Monzani, M. E.; Morselli, A.; Moskalenko, I. V.; Murgia, S.; Nakamori, T.; Naumann-Godo, M.; Nestoras, I.; Nolan, P. L.; Norris, J. P.; Nuss, E.; Ohsugi, T.; Okumura, A.; Omodei, N.; Orlando, E.; Ormes, J. F.; Ozaki, M.; Paneque, D.; Panetta, J. H.; Parent, D.; Pelassa, V.; Pepe, M.; Pesce-Rollins, M.; Piron, F.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, A.; Reimer, O.; Reyes, L. C.; Ripken, J.; Ritz, S.; Romani, R. W.; Roth, M.; Sadrozinski, H. F.-W.; Sanchez, D.; Sander, A.; Scargle, J. D.; Sgrò, C.; Shaw, M. S.; Smith, P. D.; Spandre, G.; Spinelli, P.; Strickman, M. S.; Suson, D. J.; Takahashi, H.; Tanaka, T.; Thayer, J. B.; Thayer, J. G.; Thompson, D. J.; Tibaldo, L.; Torres, D. F.; Tosti, G.; Tramacere, A.; Usher, T. L.; Vandenbroucke, J.; Vasileiou, V.; Vilchez, N.; Vitale, V.; Waite, A. P.; Wang, P.; Winer, B. L.; Wood, K. S.; Yang, Z.; Ylinen, T.; Ziegler, M.; Acciari, V. A.; Aliu, E.; Arlen, T.; Aune, T.; Beilicke, M.; Benbow, W.; Böttcher, M.; Boltuch, D.; Bradbury, S. M.; Buckley, J. H.; Bugaev, V.; Byrum, K.; Cannon, A.; Cesarini, A.; Christiansen, J. L.; Ciupik, L.; Cui, W.; de la Calle Perez, I.; Dickherber, R.; Errando, M.; Falcone, A.; Finley, J. P.; Finnegan, G.; Fortson, L.; Furniss, A.; Galante, N.; Gall, D.; Gillanders, G. H.; Godambe, S.; Grube, J.; Guenette, R.; Gyuk, G.; Hanna, D.; Holder, J.; Hui, C. M.; Humensky, T. B.; Imran, A.; Kaaret, P.; Karlsson, N.; Kertzman, M.; Kieda, D.; Konopelko, A.; Krawczynski, H.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Maier, G.; McArthur, S.; McCann, A.; McCutcheon, M.; Moriarty, P.; Mukherjee, R.; Ong, R. A.; Otte, A. N.; Pandel, D.; Perkins, J. S.; Pichel, A.; Pohl, M.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Roache, E.; Rose, H. J.; Schroedter, M.; Sembroski, G. H.; Senturk, G. Demet; Smith, A. W.; Steele, D.; Swordy, S. P.; Tešić, G.; Theiling, M.; Thibadeau, S.; Varlotta, A.; Vassiliev, V. V.; Vincent, S.; Wakely, S. P.; Ward, J. E.; Weekes, T. C.; Weinstein, A.; Weisgarber, T.; Williams, D. A.; Wissel, S.; Wood, M.; Villata, M.; Raiteri, C. M.; Gurwell, M. A.; Larionov, V. M.; Kurtanidze, O. M.; Aller, M. F.; Lähteenmäki, A.; Chen, W. P.; Berduygin, A.; Agudo, I.; Aller, H. D.; Arkharov, A. A.; Bach, U.; Bachev, R.; Beltrame, P.; Benítez, E.; Buemi, C. S.; Dashti, J.; Calcidese, P.; Capezzali, D.; Carosati, D.; Da Rio, D.; Di Paola, A.; Diltz, C.; Dolci, M.; Dultzin, D.; Forné, E.; Gómez, J. L.; Hagen-Thorn, V. A.; Halkola, A.; Heidt, J.; Hiriart, D.; Hovatta, T.; Hsiao, H.-Y.; Jorstad, S. G.; Kimeridze, G. N.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Leto, P.; Ligustri, R.; Lindfors, E.; Lopez, J. M.; Marscher, A. P.; Mommert, M.; Mujica, R.; Nikolashvili, M. G.; Nilsson, K.; Palma, N.; Pasanen, M.; Roca-Sogorb, M.; Ros, J. A.; Roustazadeh, P.; Sadun, A. C.; Saino, J.; Sigua, L. A.; Sillanää, A.; Sorcia, M.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Turchetti, R.; Umana, G.; Belloni, T.; Blake, C. H.; Bloom, J. S.; Angelakis, E.; Fumagalli, M.; Hauser, M.; Prochaska, J. X.; Riquelme, D.; Sievers, A.; Starr, D. L.; Tagliaferri, G.; Ungerechts, H.; Wagner, S.; Zensus, J. A.; Fermi LAT Collaboration; VERITAS Collaboration; GASP-WEBT Consortium

    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.

  6. Blazar flares powered by plasmoids in relativistic reconnection

    NASA Astrophysics Data System (ADS)

    Petropoulou, Maria; Giannios, Dimitrios; Sironi, Lorenzo

    2016-11-01

    Powerful flares from blazars with short (˜min) variability time-scales are challenging for current models of blazar emission. Here, we present a physically motivated ab initio model for blazar flares based on the results of recent particle-in-cell (PIC) simulations of relativistic magnetic reconnection. PIC simulations demonstrate that quasi-spherical plasmoids filled with high-energy particles and magnetic fields are a self-consistent by-product of the reconnection process. By coupling our PIC-based results (i.e. plasmoid growth, acceleration profile, particle and magnetic content) with a kinetic equation for the evolution of the electron distribution function we demonstrate that relativistic reconnection in blazar jets can produce powerful flares whose temporal and spectral properties are consistent with the observations. In particular, our model predicts correlated synchrotron and synchrotron self-Compton flares of duration of several hours-days powered by the largest and slowest moving plasmoids that form in the reconnection layer. Smaller and faster plasmoids produce flares of sub-hour duration with higher peak luminosities than those powered by the largest plasmoids. Yet, the observed fluence in both types of flares is similar. Multiple flares with a range of flux-doubling time-scales (minutes to several hours) observed over a longer period of flaring activity (days or longer) may be used as a probe of the reconnection layer's orientation and the jet's magnetization. Our model shows that blazar flares are naturally expected as a result of magnetic reconnection in a magnetically dominated jet.

  7. The power and production efficiency of blazar jets

    NASA Astrophysics Data System (ADS)

    Pjanka, Patryk; Zdziarski, Andrzej A.; Sikora, Marek

    2017-03-01

    We use published data on the power and production efficiency of jets in blazars with double radio lobes in order to compare results obtained using different methods. In order to eliminate selection effects, we use cross-matched sub-samples containing only luminous blazars. We compare the three main existing methods, namely those based on the emission of radio lobes, on spectral fitting, and on radio-core shift. We find that the average jet power obtained for identical samples with the radio-lobe method is ∼10 times lower than that from the spectral fitting. In turn, the power from spectral fitting is compatible with that from core-shift modelling for plausible parameters of the latter. We also consider a phenomenological estimator based on the γ-ray luminosity. We examine uncertainties of those methods and discuss two alternative hypotheses. In one, the blazar-fit and core-shift methods are assumed to be correct, and the lower power from radio lobes is caused by intermittency of accretion. Long periods of quiescence cause the energy in the radio lobes, accumulated over the lifetime of the blazar, to be much less than that estimated based on the present luminous state. In addition, the power calculated using the radio lobes can be underestimated for intrinsically compact jets, in which the radio-core flux can be over-subtracted. In our second hypothesis, the radio-lobe method is assumed to be correct, and the blazar-fit and core-shift powers are reduced due to the presence of ∼15 pairs per proton and a larger magnetization than usually assumed, respectively.

  8. 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.

  9. 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

  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. 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.

  12. 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.

  13. 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.

  14. AWAKENING OF THE HIGH-REDSHIFT BLAZAR CGRaBS J0809+5341

    SciTech Connect

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

    2015-04-20

    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 × 10{sup 45} erg s{sup −1} and 10{sup 8.4} M{sub ⊙}, 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.

  15. The low-frequency radio emission in blazar PKS2155-304

    NASA Astrophysics Data System (ADS)

    Pandey-Pommier, M.; Sirothia, S.; Chadwick, P.; Martin, J.-M.; Colom, P.; van Driel, W.; Combes, F.; Kharb, P.; Crespeau, P.-J.; Richard, J.; Guiderdoni, B.

    2016-12-01

    We report radio imaging and monitoring observations in the frequency range 0.235 - 2.7 GHz during the flaring mode of PKS 2155-304, one of the brightest BL Lac objects. The high sensitivity GMRT observations not only reveal extended kpc-scale jet and FRI type lobe morphology in this erstwhile 'extended-core' blazar but also delineate the morphological details, thanks to its arcsec scale resolution. The radio light curve during the end phase of the outburst measured in 2008 shows high variability (8.5%) in the jet emission in the GHz range, compared to the lower core variability (3.2%) seen at the lowest frequencies. The excess of flux density with a very steep spectral index in the MHz range supports the presence of extra diffuse emission at low frequencies. The analysis of multi wavelength (radio/optical/gamma-ray) light curves at different radio frequencies confirms the variability of the core region and agrees with the scenario of high energy emission in gamma-rays due to inverse Compton emission from a collimated relativistic plasma jet followed by synchrotron emission in radio. Clearly, these results give an interesting insight of the jet emission mechanisms in blazars and highlight the importance of studying such objects with low frequency radio interferometers like LOFAR and the SKA and its precursor instruments.

  16. VizieR Online Data Catalog: Fermi bright blazars (Fuhrmann+, 2014)

    NASA Astrophysics Data System (ADS)

    Fuhrmann, L.; Larsson, S.; Chiang, J.; Angelakis, E.; Zensus, J. A.; Nestoras, I.; Krichbaum, T. P.; Ungerechts, H.; Sievers, A.; Pavlidou, V.; Readhead, A. C. S.; Max-Moerbeck, W.; Pearson, T. J.

    2015-02-01

    The present study is focusing on the sources observed at radio bands by the F-GAMMA monitoring programme. With a total of about 90 AGN/blazars ever observed since 2007 January, these sources constitute a sample of well known, frequently active and bright blazars (δ>-30°) for detailed studies of the most prominent behaviour of the brightest γ-ray-loud blazars. (1 data file).

  17. Multiwavelength multistatic optical scattering for aerosol characterization

    NASA Astrophysics Data System (ADS)

    Brown, Andrea M.

    The main focus of this research is the development of a technique to remotely characterize aerosol properties, such as particle size distribution, concentration, and refractive index as a function of wavelength, through the analysis of optical scattering measurements. The proposed technique is an extension of the multistatic polarization ratio technique that has been developed by prior students at the Penn State Lidar Lab to include multiple wavelengths. This approach uses the ratio of polarized components of the scattering phase functions at multiple wavelengths across the visible region of the electromagnetic spectrum to extract the microphysical and optical properties of aerosols. The scattering intensities at each wavelength are vertically separated across the face of the imager using a transmission diffraction grating, so that scattering intensities for multiple wavelengths at many angles are available for analysis in a single image. The ratio of the scattering phase function intensities collected using parallel and perpendicular polarized light are formed for each wavelength and analysis of the ratio is used to determine the microphysical properties of the aerosols. One contribution of the present work is the development of an inversion technique based on a genetic algorithm that retrieves lognormal size distributions from scattering measurements by minimizing the squared error between measured polarization ratios and polarization ratios calculated using the Mie solution to Maxwell's equations. The opportunities and limitations of using the polarization ratio are explored, and a genetic algorithm is developed to retrieve single mode and trimodal lognormal size distributions from multiwavelength, angular scattering data. The algorithm is designed to evaluate particles in the diameter size range of 2 nm to 60 im, and uses 1,000 linear spaced diameters within this range to compute the modeled polarization ratio. The algorithm returns geometric mean radii and

  18. Multiwavelength electronic speckle pattern interferometry for surface shape measurement

    NASA Astrophysics Data System (ADS)

    Barbosa, Eduardo A.; Lino, Antonio C. L.

    2007-05-01

    Profilometry by electronic speckle pattern interferometry with multimode diode lasers is both theoretically and experimentally studied. The multiwavelength character of the laser emission provides speckled images covered with interference fringes corresponding to the surface relief in single-exposure processes. For fringe pattern evaluation, variations of the phase-stepping technique are investigated for phase mapping as a function of the number of laser modes. Expressions for two, three, and four modes in four and eight stepping are presented, and the performances of those techniques are compared in the experiments through the surface shaping of a flat bar. The surface analysis of a peach points out the possibility of applying the technique in the quality control of food production and agricultural research.

  19. Multiwavelength ultrashort pulse generator using a diverging time-lens

    NASA Astrophysics Data System (ADS)

    Jiang, Xiangyu; Huo, Li; Wang, Dong; Chen, Xin; Lou, Caiyun

    2015-12-01

    A self-starting optoelectronic oscillator that employs a diverging time lens and a Mach-Zehnder modulator (MZM) in a fiber-extended cavity to generate a multiwavelength ultrashort pulse train is demonstrated. The switching window formed by the MZM is narrowed by the use of a diverging time lens, which is a phase modulator in our study. A wavelength assignment scheme is deployed to simultaneously suppress the pedestals of pulses on different wavelengths. A detailed analysis is given, and the results are presented by experiment. We have generated 25 GHz optical pulses simultaneously on four wavelengths as a proof-of-concept demonstration. The pulse width of the optical pulse, the phase noise, and the timing jitter performance of the generated microwave signal are experimentally measured.

  20. Rules of Emissivity Sample Choice in Multi-wavelength Pyrometry

    NASA Astrophysics Data System (ADS)

    Liang, M.; Sun, B.; Sun, X.; Xie, J.; Yu, C.

    2017-03-01

    Since the theory for emissivity sample (example) is not clear, there exists unavoidable blindness in the sample choice for the true temperature determination (create emissivity samples using an assumption to calculate the true temperature according to brightness temperature and wavelength) in multi-wavelength pyrometry, resulting in considerable computational complexity and slow computing speed. In this article, the rules of the emissivity sample were first discovered through the theoretical analysis of the relationship between brightness temperature and emissivity, which provide a theoretical basis for the emissivity sample choice. Furthermore, the rules can reduce the sample size (amount) and improve the calculation speed. The effectiveness of the proposed rules was verified by measuring the true temperature of a solid rocket engine plume, in which the rules were applied to effectively select emissivity samples. The experimental results demonstrate that the computing speed of the true temperature determination can be improved by 5.73% to 48.64%.

  1. Multiwavelength optical storage of diarylethene PMMA films

    NASA Astrophysics Data System (ADS)

    Guo, Haobo; Zhang, Fushi; Sun, Fan; Pu, Shouzhi; Zhou, Xinhong

    2003-04-01

    Current applied optical storage technologies are all based on the heat effect of the recording laser, i.e., heat-mode optical storage. In the present work, photon-mode optical storage using photochromic diarylethene materials was investigated. Two diarylethene molecules dispersed into PMMA together was used as storage material. The recording layer was spin-coated on a glass substrate with Al reflective layer. Two laser beams of 532 nm and 650 nm were used in recording and readout by simultaneously writing and reading, and the reading lasers detected signals with high S/N ratio. Multi-wavelength storage was realized with the diarylethene PMMA film.

  2. WEBT multiwavelength monitoring and XMM-Newton observations of BL Lacertae in 2007-2008. Unveiling different emission components

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Villata, M.; Capetti, A.; Aller, M. F.; Bach, U.; Calcidese, P.; Gurwell, M. A.; Larionov, V. M.; Ohlert, J.; Nilsson, K.; Strigachev, A.; Agudo, I.; Aller, H. D.; Bachev, R.; Benítez, E.; Berdyugin, A.; Böttcher, M.; Buemi, C. S.; Buttiglione, S.; Carosati, D.; Charlot, P.; Chen, W. P.; Dultzin, D.; Forné, E.; Fuhrmann, L.; Gómez, J. L.; Gupta, A. C.; Heidt, J.; Hiriart, D.; Hsiao, W.-S.; Jelínek, M.; Jorstad, S. G.; Kimeridze, G. N.; Konstantinova, T. S.; Kopatskaya, E. N.; Kostov, A.; Kurtanidze, O. M.; Lähteenmäki, A.; Lanteri, L.; Larionova, L. V.; Leto, P.; Latev, G.; Le Campion, J.-F.; Lee, C.-U.; Ligustri, R.; Lindfors, E.; Marscher, A. P.; Mihov, B.; Nikolashvili, M. G.; Nikolov, Y.; Ovcharov, E.; Principe, D.; Pursimo, T.; Ragozzine, B.; Robb, R. M.; Ros, J. A.; Sadun, A. C.; Sagar, R.; Semkov, E.; Sigua, L. A.; Smart, R. L.; Sorcia, M.; Takalo, L. O.; Tornikoski, M.; Trigilio, C.; Uckert, K.; Umana, G.; Valcheva, A.; Volvach, A.

    2009-11-01

    Context: BL Lacertae is the prototype of the blazar subclass named after it. Yet, it has occasionally shown a peculiar behaviour that has questioned a simple interpretation of its broad-band emission in terms of synchrotron plus synchrotron self-Compton (SSC) radiation. Aims: In the 2007-2008 observing season we carried out a new multiwavelength campaign of the Whole Earth Blazar Telescope (WEBT) on BL Lacertae, involving three pointings by the XMM-Newton satellite in July and December 2007, and January 2008, to study its emission properties, particularly in the optical-X-ray energy range. Methods: The source was monitored in the optical-to-radio bands by 37 telescopes. The brightness level was relatively low. Some episodes of very fast variability were detected in the optical bands. Flux changes had larger amplitude at the higher radio frequencies than at longer wavelengths. Results: The X-ray spectra acquired by the EPIC instrument onboard XMM-Newton are well fitted by a power law with photon index Γ ˜ 2 and photoelectric absorption exceeding the Galactic value. However, when taking into account the presence of a molecular cloud on the line of sight, the EPIC data are best fitted by a double power law, implying a concave X-ray spectrum. The spectral energy distributions (SEDs) built with simultaneous radio-to-X-ray data at the epochs of the XMM-Newton observations suggest that the peak of the synchrotron emission lies in the near-IR band, and show a prominent UV excess, besides a slight soft-X-ray excess. A comparison with the SEDs corresponding to previous observations with X-ray satellites shows that the X-ray spectrum is very variable, since it can change from extremely steep to extremely hard, and can be more or less curved in intermediate states. We ascribe the UV excess to thermal emission from the accretion disc, and the other broad-band spectral features to the presence of two synchrotron components, with their related SSC emission. We fit the thermal

  3. 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

  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. 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.

  6. GTC Optical Spectroscopy of TeV Blazars

    NASA Astrophysics Data System (ADS)

    Paiano, Simona; Falomo, R.; Treves, A.; Landoni, M.; Scarpa, R.; Righi, C.

    2016-10-01

    We carried out an extensive spectroscopic campaign of blazars of unknown or uncertain redshift which are either detected in the TeV band by Cherenkov telescopes or good candidate as TeV emitters. We used the OSIRIS spectrograph at the Gran Telescopio of Canarias (GTC) at La Palma to secure high signal-to-noise ratio spectra at intermediate resolution in the range 3800-10000 Ang. These observations allow us to confirm the blazar classification, to find new redshift and/or to set stringent lower limits. The results are discussed in the context of emission modeling of TeV sources and are of importance for the characterization of the Extragalactic Background Light.

  7. Egret detection of the blazar PKS 0420-014

    NASA Technical Reports Server (NTRS)

    Radecke, H.-D.; Bertsch, D. L.; Dingus, B. L.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Lin, Y. C.; Mattox, J. R.

    1995-01-01

    During its full-sky survey, the Energetic Gamma Ray Experiment Telescope (EGRET) high-energy instrument aboard the Compton Gamma-Ray Observatory detected gamma-ray emission in the energy range above 30 MeV from a source identified as the blazar PKS 0420-014. This object was observed during two separate viewing periods in 1992 February/March and May/June. An intensity decrease above 100 MeV of a factor of at least 1.5 from a maximum of (5.0 +/- 1.4) x 10(exp -7) photons 1 sq cm/s was observed during that time interval indicating extensive variability. The photon spectrum in the range between 30 and 10,000 MeV at the time of the maximum intensity is well represented by a power law with an exponent of -1.9 +/- 0.3. Some similarities with other EGRET detected blazars are briefly discussed.

  8. 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.

  9. QUASI-PERIODICITIES AT YEAR-LIKE TIMESCALES IN BLAZARS

    SciTech Connect

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

    2016-03-15

    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 and 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.

  10. The γ-ray spectral changes in Fermi blazars

    NASA Astrophysics Data System (ADS)

    Yang, Jianghe; Fan, Junhui; Nie, Jianjun; Yang, Rushu; Tuo, Manxian; Zhang, Yuelian

    2017-02-01

    Based upon Fermi 2FGL and 3FGL catalogues, a sample of 842 blazars (hereinto 356 FSRQs, 486 BL Lac objects) is collected to discuss the changes of γ-ray photon spectral indices and brightness from 2FGL to 3FGL blazars. Our results indicate that the distributions of γ-ray photon spectral indices and luminosities between 2FGL and 3FGL have no obvious difference; The photon spectral indices and γ-ray luminosity from 2FGL are closely correlated with that from 3FGL respectively; There are close anti-relations between the change of photon spectral indices and the change of luminosity for FSRQs and BL Lac objects samples and for sub-class samples of HBLs, IBLs and LBLs, which suggests that the spectrum becomes flat when the source becomes bright.

  11. Searching for the first blazars with LMT and GLAST

    SciTech Connect

    Rodriguez-Linan, Gustavo M.; Carraminana, Alberto

    2007-07-12

    Massive star formation and black hole growth are prone to be linked in massive protogalaxies. This relation has been studied at low redshifts, pointing to active galactic nuclei growing within dust enshrouded high redshift galaxies, a prime target of the Large Millimeter Telescope. The coincidence of GLAST sources with highly-obscured high-redshift LMT/GTM galaxies can be a powerful tool for studying the formation of the first blazars.

  12. Extended Optical Flaring of the Blazar 3C 279

    NASA Astrophysics Data System (ADS)

    Turner, C. S.; Miller, H. R.

    2017-03-01

    The blazar, 3C 279, was previously reported to be undergoing a major optical outburst (ATEL#10121 and ATEL#10161). We report optical observations of 3C 279 on March 19 when it was observed with the 24-inch telescope at Georgia State University's Hard Labor Creek Observatory with R=13.46+/-0.01 mag. These observations indicate that 3C 279 continues to be in an extremely bright state.

  13. 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.

  14. Polarization-independent all-fiber multiwavelength-switchable filter based on a polarization-diversity loop configuration

    NASA Astrophysics Data System (ADS)

    Lee, Yong Wook; Han, Kyung Jun; Lee, Byoungho; Jung, Jaehoon

    2003-12-01

    In this paper a polarization-independent all-fiber multiwavelength-switchable filter based on a polarization-diversity loop configuration is newly proposed. The proposed apparatus consists of a polarization beam splitter, high birefringence fibers, and polarization controllers. Our theoretical analysis shows that the apparatus exhibits unique feature which allows it to operate as a polarization-independent multiwavelength periodic filter with a good channel isolation and to make its channel wavelength switchable by varying effective birefringence of the polarization-diversity loop through the proper adjustment of the polarization controllers contained within the loop. Theoretical prediction was experimentally verified.

  15. Tea quality and classification evaluation using multi-wavelength light-emitting diodes induced fluorescence spectroscopy

    NASA Astrophysics Data System (ADS)

    Feng, Chao; Liu, Xuan; Yan, Chunsheng; He, Sailing; Mei, Liang

    2013-03-01

    In this paper, we demonstrated a detective system to evaluate the quality and classification of different tea samples based on multi-wavelength LED-induced fluorescence spectroscopy. By utilizing multiple excitation wavelengths, we obtained much more physical and chemical information from the detected samples than single excitation wavelength. By utilizing principal component analysis (PCA), we extracted the dominant features of the samples to classify and characterize the tea samples.

  16. 2WHSP: A multi-frequency selected catalog of VHE gamma-ray blazars and blazar candidates

    NASA Astrophysics Data System (ADS)

    Chang, Yu Lin; Arsioli, Bruno; Giommi, Paolo; Padovani, Paolo

    2016-08-01

    High Synchrotron Peaked Blazars (HSPs) are extremely important for VHE astronomy. We built the largest existing catalog of High Synchrotron Blazars (2WHSP) based on multi-frequency data. The catalog is an extension of the 1WHSP list. We compared several general properties of HSPs such as the synchrotron peak, the redshift and IR the color-color diagram. We also built the logN-logS for the sources, trying to see the evolution and the deficiency of the catalog. The catalog will provide a unique sample of targets for VHE observations in future since the HSPs are the dominant extra-Galactic sources in VHE sky. This might help find more VHE sources later. In the future, we will use this catalog to estimate other VHE properties of HSPs.

  17. Observations of 4 Blazars with the Robotically Controlled Telescope in 2011

    NASA Astrophysics Data System (ADS)

    Carini, Michael T.; Brown, R.

    2012-01-01

    During 2011, four Blazars were intensively monitored in the R band with the Robotically Controlled Telescope (RCT): 3C 273, 3C 279, BL Lacertae and 1ES 1028+511. We present the results of this optical R band monitoring and demonstrate the vast potential of the RCT as an instrument for monitoring Blazars and other astronomical phenomena with time variable continuum emission.

  18. Characterizing the Optical Variability of Bright Blazars: Variability-Based Selection of Fermi Active Galactic Nuclei

    DTIC Science & Technology

    2012-11-20

    10′. We do not apply cosmological redshift corrections here for blazar selection. Similar to the conclusions drawn from Figure 4, there is clear...effects. For example, the observed blazar characteristic damping timescale τblz,obs (after correcting for cosmological redshift) should be shortened in

  19. 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.

  20. 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

  1. Thermal Emission Signatures in Non-thermal Blazars

    NASA Astrophysics Data System (ADS)

    Malmrose, Michael Paul

    Blazars, a subclass of active galactic nuclei with powerful relativistic plasma jets, are among the most luminous and violently variable objects in the universe. They emit radiation across the entire electromagnetic spectrum, and often change in brightness over the course of hours or days. Different emission mechanisms are necessary in order to explain the observed flux in different frequency ranges. In the ultraviolet-optical- infrared regime these include components that arise from: 1) polarized synchrotron radiation emanating from a powerful parsec-scale jet flowing from near the central accreting black hole, 2) a multi-temperature accretion disk emitting thermal radiation, and 3) an optically thick dusty torus located several parsecs from the central engine that absorbs and re-emits, at infrared wavelengths, radiation originating in the accretion disk. The goal of this study is to determine the relative importance of these spectral components in the spectra of blazars. I use data from the Spitzer Space Telescope in order to search for the presence of the dusty torus surrounding four blazars, as well as to determine its luminosity and temperature. In two of the observed sources, 1222+216 and CTA102, I determine that the torus can be modeled as a 1200 K blackbody emitting at nearly 1046 erg s-1. Furthermore, I determine the relative variability of the accretion disk of a sample of blazars by using spectropolarimetry observations to separate the optical-UV spectrum into a polarized component, consisting of radiation described by a power-law Fnu ∝ nu-alpha, and an accretion disk which consists of a thin disk described by the power-law Fdisk ∝ nu1/3 plus a hot-spot of variable temperature. The spectra of several blazars are explained by a version of this model in which the thin disk component is held constant, while the blackbody varies on timescales of approximately years resulting with a flux of the blackbody component comparable to the power-law disk

  2. The gamma-ray blazar quest: new optical spectra, state of art and future perspectives

    NASA Astrophysics Data System (ADS)

    Massaro, F.; Álvarez Crespo, N.; D'Abrusco, R.; Landoni, M.; Masetti, N.; Ricci, F.; Milisavljevic, D.; Paggi, A.; Chavushyan, V.; Jiménez-Bailón, E.; Patiño-Álvarez, V.; Strader, J.; Chomiuk, L.; La Franca, F.; Smith, Howard A.; Tosti, G.

    2016-10-01

    We recently developed a procedure to recognize γ-ray blazar candidates within the positional uncertainty regions of the unidentified/unassociated γ-ray sources (UGSs). Such procedure was based on the discovery that Fermi blazars show peculiar infrared colors. However, to confirm the real nature of the selected candidates, optical spectroscopic data are necessary. Thus, we performed an extensive archival search for spectra available in the literature in parallel with an optical spectroscopic campaign aimed to reveal and confirm the nature of the selected γ-ray blazar candidates. Here, we first search for optical spectra of a selected sample of γ-ray blazar candidates that can be potential counterparts of UGSs using the Sloan Digital Sky Survey (SDSS DR12). This search enables us to update the archival search carried out to date. We also describe the state-of-art and the future perspectives of our campaign to discover previously unknown γ-ray blazars.

  3. 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.

  4. Understanding the general feature of microvariability in Kepler blazar W2R 1926+42

    NASA Astrophysics Data System (ADS)

    Sasada, Mahito; Mineshige, Shin; Yamada, Shinya; Negoro, Hitoshi

    2017-02-01

    We analyze the Kepler monitoring light curve of a blazar W2R 1926+42 to examine features of microvariability by means of the "shot analysis" technique. We select 195 intra-day, flare-like variations (shots) for the continuous light curve of Quarter 14 with a duration of 100 d. In the application of the shot analysis, an averaged profile of variations is assumed to converge with a universal profile which reflects a physical mechanism generating the microvariability in a blazar jet, although light-variation profiles of selected shots show a variety. A mean profile, which is obtained by aligning the peaks of the 195 shots, is composed of a spiky-shaped shot component at ± 0.1 d (with respect to the time of the peak), and two slow varying components ranging from -0.50 d to -0.15 d and from 0.10 d to 0.45 d of the peak time. The former spiky feature is well represented by an exponential rise of 0.043 ± 0.001 d and an exponential decay of 0.061 ± 0.002 d. These timescales are consistent with that corresponding to a break frequency of a power spectrum density calculated from the obtained light curve. After verification with the Monte Carlo method, the exponential shape, but not the observed asymmetry, of the shot component can be explained by noise variation. The asymmetry is difficult to explain through a geometrical effect (i.e., changes of the geometry of the emitting region), but is more likely to be caused by the production and dissipation of high-energy accelerated particles in the jet. Additionally, the durations of the detected shots show a systematic variation with a dispersion caused by a statistical randomness. A comparison with the variability of Cygnus X-1 is also briefly discussed.

  5. News Note: National Strategy for Multi-wavelength Astronomy

    NASA Astrophysics Data System (ADS)

    2016-06-01

    The Department of Science and Technology (DST) has released the National Strategy for Multiwavelength Astronomy, which is intended to allow South Africa to take full advantage of its geographical advantages, and to maximise the return on investment made in astronomy.

  6. Multi-wavelength Observations of Microflares Near an Active Region

    NASA Astrophysics Data System (ADS)

    Bein, B.; Veronig, A.; Rybak, J.; Gömöry, P.; Berkebile-Stoiser, S.; Sütterlin, P.

    We study the multi-wavelength characteristics of a microflaring active region (AR 10898) near disc centre. The analysed data were from the 4^{th} of July 2006, and were recorded by DOT (Hα, Ca II H), RHESSI (X-rays), TRACE (EUV) and SOHO/MDI (magnetograms). The identified microflare events were studied with respect to their magnetic field configuration and their multi-wavelength time evolution.

  7. Comparison of Fresh and Aged TNT with Multiwavelength Raman Spectroscopy

    DTIC Science & Technology

    2014-12-04

    Naval Research Laboratory Washington, DC 20375-5320 NRL/MR/6730--14-9572 Comparison of Fresh and Aged TNT with Multiwavelength Raman Spectroscopy...NUMBER OF PAGES 17. LIMITATION OF ABSTRACT Comparison of Fresh and Aged TNT with Multiwavelength Raman Spectroscopy Robert Lunsford, Jacob Grun, and...fresh and aged variants. This is particularly true of UV aging which had the greater effect on the sample of the two aging processes tested

  8. 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

  9. Blazar physics through multi-band linear and circular polarization monitoring

    NASA Astrophysics Data System (ADS)

    Myserlis, I.

    2013-09-01

    show rapid polarization variability. I will start the talk with a general discussion of the great potential that high cadence polarization monitoring holds for probing the physical conditions of blazars. Subsequently, a description of the FGAMMA and RoboPol monitoring programs will follow, including: (a) the sample selection, (b) the system description and (c) important observational facts. Then, the focus will be put on the radio polarization measurements and the method followed for the necessary determination and correction of the instrumental polarization. Such measurements can be very challenging, especially for circular polarization, since most AGN exhibit low levels of radio polarization (~5% linear and <1% circular) due to incoherent emission, beam depolarization and so on. Nevertheless, preliminary analysis of the radio monitoring data has revealed sources which show significant Stokes V measurements persistently (3C84, 3C454.3). These findings are very promising because circular polarization measurements can give us a direct insight into the magnetic field ordering, the composition and other features of the jet. Finally, some first results from the radio and optical polarimetric data analysis in progress will be discussed. Such results can also be combined to investigate the correlation between the two regions of the jet which are probed by optical and radio emission.

  10. 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.

  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. 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.

  13. NEARLY PERIODIC FLUCTUATIONS IN THE LONG-TERM X-RAY LIGHT CURVES OF THE BLAZARS AO 0235+164 AND 1ES 2321+419

    SciTech Connect

    Rani, Bindu; Gupta, Alok C.; Wiita, Paul J. E-mail: acgupta30@gmail.com

    2009-05-10

    We have performed a structure function analysis of the Rossi X-Ray Timing Explorer All-Sky Monitor data to search for variability in 24 blazars using data trains that each exceed 12 yr. Although 20 of them show nominal periods through this technique, the great majority of these 'periods' are clearly related to yearly variations arising from the instrument. Nonetheless, an apparently real periodic component of about 17 days was detected for the blazar AO 0235+164 and it was confirmed by discrete correlation function and periodogram analyses. For 1ES 2321+419, a component of variability with a near periodicity of about 420 days was detected by all of these methods. We discuss several possible explanations for these nearly periodic components and conclude that they most likely arise from the intersections of a shock propagating down a relativistic jet that possesses a helical structure.

  14. The RINGO2 and DIPOL optical polarization catalogue of blazars

    NASA Astrophysics Data System (ADS)

    Jermak, H.; Steele, I. A.; Lindfors, E.; Hovatta, T.; Nilsson, K.; Lamb, G. P.; Mundell, C.; Barres de Almeida, U.; Berdyugin, A.; Kadenius, V.; Reinthal, R.; Takalo, L.

    2016-11-01

    We present ˜2000 polarimetric and ˜3000 photometric observations of 15 γ-ray bright blazars over a period of 936 days (2008-10-11 to 2012-10-26) using data from the Tuorla blazar monitoring program (KVA DIPOL) and Liverpool Telescope (LT) RINGO2 polarimeters (supplemented with data from SkyCamZ (LT) and Fermi-LAT γ-ray data). In 11 out of 15 sources we identify a total of 19 electric vector position angle (EVPA) rotations and 95 flaring episodes. We group the sources into subclasses based on their broad-band spectral characteristics and compare their observed optical and γ-ray properties. We find that (1) the optical magnitude and γ-ray flux are positively correlated, (2) EVPA rotations can occur in any blazar subclass, four sources show rotations that go in one direction and immediately rotate back, (3) we see no difference in the γ-ray flaring rates in the sample; flares can occur during and outside of rotations with no preference for this behaviour, (4) the average degree of polarization (DoP), optical magnitude and γ-ray flux are lower during an EVPA rotation compared with during non-rotation and the distribution of the DoP during EVPA rotations is not drawn from the same parent sample as the distribution outside rotations, (5) the number of observed flaring events and optical polarization rotations are correlated, however we find no strong evidence for a temporal association between individual flares and rotations and (6) the maximum observed DoP increases from ˜10 per cent to ˜30 per cent to ˜40 per cent for subclasses with synchrotron peaks at high, intermediate and low frequencies, respectively.

  15. 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.

  16. 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.

  17. NIR flaring of the blazar B2 0619+33

    NASA Astrophysics Data System (ADS)

    Carrasco, L.; Carramiñana, A.; Recillas, E.; Porras, A.; Mayya, D. Y.; Escobedo, G.

    2010-09-01

    We report on our recent observation of the blazar B2 0619+33 also known as GB6 J0622+3326 with the CANICA NIR camera on the 2.1m telescope at the Observatorio Astrofísico Guillermo Haro, located in Cananea, Mexico. On September 11th, 2010 (JD24555450.98694), we found this source to be in outburst. On this date the source was found to have a flux corresponding to H = 14.223 +/- 0.05. The source was not detected by the 2mass all sky survey.

  18. NIR flaring of the blazar B3 1726+455

    NASA Astrophysics Data System (ADS)

    Carrasco, L.; Carramiñana, A.; Recillas, E.; Porras, A.; Valdes, J. R.; Mayya, Y. D.; Escobedo, G.; Torres, I.

    2010-10-01

    We report on our recent observation of the blazar B3 1726+455, also known as S4 1726+45, and CGRaBS J1727+4530, with the CANICA NIR camera on the 2.1m telescope at the Observatorio Astrofísico Guillermo Haro, located in Cananea, Mexico. On September 16th,2010 (JD2455455.7092), we found this source to be in outburst. On this date the source was found to have a flux corresponding to H = 14.32 +/- 0.06.

  19. NIR brightening of the Blazar PKS1550-242

    NASA Astrophysics Data System (ADS)

    Carrasco, L.; Porras, A.; Escobedo, G.; Recillas, E.; Carraminana, A.

    2013-04-01

    We call attention on our recent NIR observations of the Gamma Ray source 1FGLJ1553.4-2425, (cross correlated in position with the radio source PKS1550-242) with the CANICA NIR camera on the 2.1m telescope at the Observatorio Astrofisico Guillermo Haro, located in Cananea, Mexico. On April 5th, 2013 (JD2456387.0006), we found this blazar to be in a new outburst. It showed fluxes about 0.7 magnitudes brighter than our previous NIR photometry.

  20. Detection of cm to sub-mm band radio and gamma-ray correlated variability in Fermi bright blazars

    NASA Astrophysics Data System (ADS)

    Fuhrmann, Lars; Larsson, S.; Chiang, J.; Angelakis, E.; Zensus, A.; F-GAMMA Team; Fermi Collaboration

    2014-01-01

    The exact location of the gamma-ray emitting region in blazars is still controversial. In order to attack this problem we performed a detailed statistical cross-correlation analysis between radio (cm/mm/sub-mm wavelengths, F-GAMMA program) and gamma-ray 3.5 year light curves of 54 Fermi bright blazars. In this talk, the main results of this analysis are highlighted including the first significant detection of multi-band radio/gamma-ray correlations using a stacking analysis. The radio bands are usually lagging the gamma rays with average time delays (source frame) ranging between 76+/-23 and 7+/-9 days, systematically decreasing from cm to mm/sub-mm bands following a power-law frequency dependence. The latter is in good agreement with synchrotron self-absorption dominated opacity effects, whereas a (positive) time lag of 12+/-8 days at 3 mm strongly suggests that the bulk gamma-ray production region is usually located within or even upstream of the innermost mm core region of these sources. Based on our findings we finally demonstrate that the gamma-ray emitting region of quasar 3C 454.3 is located at a distance of > 0.8-1.6 pc from the central supermassive black hole, i.e. at the outer edge of the Broad Line Region or beyond.

  1. 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.

  2. Monitoring of Gamma-Ray Bright AGN: The Multi-Frequency Polarization of the Flaring Blazar 3C 279

    NASA Astrophysics Data System (ADS)

    Kang, Sincheol; Lee, Sang-Sung; Byun, Do-Young

    2015-10-01

    We present results of long-term multi-wavelength polarization observations of the powerful blazar 3C 279 after its γ-ray flare on 2013 December 20. We followed up this flare with single-dish polarization observations using two 21-m telescopes of the Korean VLBI Network. Observations carried out weekly from 2013 December 25 to 2015 January 11, at 22 GHz, 43 GHz, 86 GHz simultaneously, as part of the Monitoring Of GAmma-ray Bright AGN (MOGABA) program. We measured 3C 279 total flux densities of 22-34 Jy at 22 GHz, 15-28 Jy (43 GHz), and 10-21 Jy (86 GHz), showing mild variability of ≤ 50 % over the period of our observations. The spectral index between 22 GHz and 86 GHz ranged from -0.13 to -0.36. Linear polarization angles were 27°-38°, 30°-42°, and 33°-50° at 22 GHz, 43 GHz, and 86 GHz, respectively. The degree of linear polarization was in the range of 6-12%, and slightly decreased with time at all frequencies. We investigated Faraday rotation and depolarization of the polarized emission at 22-86 GHz, and found Faraday rotation measures (RM) of -300 to -1200 rad m^{-2} between 22 GHz and 43 GHz, and -800 to -5100 rad m^{-2} between 43 GHz and 86 GHz.The RM values follow a power law with a mean power law index a of 2.2, implying that the polarized emission at these frequencies travels through a Faraday screen in or near the jet. We conclude that the regions emitting polarized radio emission may be different from the region responsible for the 2013 December γ-ray flare and are maintained by the dominant magnetic field perpendicular to the direction of the radio jet at milliarcsecond scales.

  3. 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.

  4. 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.

  5. Correlation between γ-Ray and Radio Bands for γ-Ray Loud Blazars

    NASA Astrophysics Data System (ADS)

    Wu, D. X.; Fan, J. H.; Li, S. H.

    2014-09-01

    The most identified sources observed by Fermi are blazars (Flat Spectrum Radio Quasars (FSRQs) and BL Lacertae objects (BLs). In this paper, we obtained 124 γ-ray loud blazars with available γ-ray and radio (core and total) data. It is interesting that the γ-ray luminosity have a good correlation with the radio luminosity. This phenomenon exists in the core radio luminosity ( L c) and total radio luminosity ( L t). The correlation between the γ-ray and the radio luminosities is still stronger even after we eliminated the redshift effect, which suggests that the γ-ray radiations in the γ-ray loud blazars are strongly beamed.

  6. Gamma-Ray Flares and VLBI Outbursts of Blazars

    NASA Astrophysics Data System (ADS)

    Romanova, M. M.; Lovelace, R. V. E.

    1997-01-01

    A model is developed for the time dependent electromagnetic--radio to gamma-ray--emission of active galactic nuclei, specifically, the blazars, based on the acceleration and creation of leptons at a propagating discontinuity or front of a self-collimated Poynting flux jet. The front corresponds to a discrete relativistic jet component as observed with very long baseline interferometry (VLBI). Equations are derived for the number, momentum, and energy of particles in the front taking into account synchrotron, synchrotron-self-Compton (SSC), and inverse-Compton processes as well as photon-photon pair production. The apparent synchrotron, SSC, and inverse Compton luminosities as functions of time are determined. Predictions of the model are compared with observations in the gamma, optical, and radio bands. The delay between the high-energy gamma-ray flare and the onset of the radio is explained by self-absorption and/or free-free absorption by external plasma. Two types of gamma-ray flares are predicted: Compton dominated or SSC dominated, depending on the initial parameters in the front. The theory is applied to the recently observed gamma-ray flare of the blazar PKS 1622-297 (Mattox et al. 1997). Approximate agreement of theoretical and observed light curves is obtained for a viewing angle θobs ~ 0.1 rad, a black hole mass M ~ 3 × 109 M⊙, and a magnetic field at the base of the jet B0 ~ 103 G.

  7. Dust Obscured Blazars as sources of high-energy neutrinos

    NASA Astrophysics Data System (ADS)

    Maggi, G.; de Vries, K. D.; van Eijndhoven, N.

    2016-08-01

    Active Galactic Nuclei (AGN) are believed to be among the most promising sources of the ultra-high-energy cosmic ray flux. A hadronic component which is accelerated in the high energy environment of an AGN immediately implies the production of high-energy neutrinos. Nevertheless, no clear correlation between AGN and the high-energy cosmic-neutrino flux obtained by IceCube has been found so-far, putting strong limits on the neutrino production at AGN. We discuss a specific type of AGN for which an enhanced neutrino production is expected. This specific sub-set is given by AGN with their high-energy jet directed toward Earth, which is obscured by surrounding dust or gas, defining Dust Obscured Blazars. This type of AGN is predicted to have an enhanced neutrino emission due to the interaction of a possible hadronic component inside the AGN-jet with the surrounding matter. From two different galaxy catalogs, we have selected a sample of nearby sources with the characteristics of Dust Obscured Blazars. This selection is based on observations in the X-ray and radio bands. The data is consequently used to investigate the column density of the surrounding matter, providing an estimate for the neutrino production enhancement due to the nucleon-matter interactions in a beam dump scenario for various dust or gas compositions.

  8. Novel multiwavelength microscopic scanner for mouse imaging.

    PubMed

    Alencar, Herlen; Mahmood, Umar; Kawano, Yoshihiro; Hirata, Tadashi; Weissleder, Ralph

    2005-11-01

    Real-time in vivo imaging of molecular targets at (sub)cellular resolution is essential in better understanding complex biology. Confocal microscopy and multiphoton microscopy have been used in the past to achieve this goal, but their true capabilities have often been limited by bulky optics and difficult experimental set-ups requiring exteriorized organs. We describe here the development and validation of a unique near-infrared laser scanning microscope system that uses novel optics with a millimeter footprint. Optimized for use in the far red and near-infrared ranges, the system allows an imaging depth that extends up to 500 microm from a 1.3-mm-diameter stick objective, which is up to 2 cm in length. We show exceptionally high spatial, temporal, and multiwavelength resolutions of the system and show that it can be applied to virtually any internal organ through a keyhole surgical access. We demonstrate that, when combined with novel far red imaging probes, it is possible to image the cellular details of many organs and disease processes. The new optics, coupled with the use of near-infrared probes, should prove immensely valuable for in vivo cancer imaging.

  9. 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.

  10. Rings in Radio Galaxies: a Multiwavelength Approach

    NASA Astrophysics Data System (ADS)

    Gizani, Nectaria A.; Garrett, M. A.; Morganti, R.; Cohen, A.; Kassim, N.; Gonzales-Serrano, I.; Leahy, J. P.

    We are studying the two powerful radio galaxies Hercules A and 3C310 and their clusters. They present many essential and atypical similarities with the striking one being the presence of large-scale rings instead of hotspots. Employing a multiwavelength observational campaign from radio to Gamma-ray wavelengths we are trying to determine the origin of their unusual structure and tenue (compared with the common AGN) and to disentagle the physical mechanisms taking place interior to them and in their clusters. For example: -In the RADIO we probe the pc- and kpc-scale environment. -In the (Near-)INFRARED we try to constrain the nature of the acceleration mechanism in the rings with the corresponding in the usual hotspots investigate the ISM shed light in their evolution. -In the OPTICAL we study of the ionized gas in the accretion disk fuelling the massive black hole. -In the ULTRAVIOLET we explore the nuclear region the ISM and its interaction with the jets. -In the X-RAYS we probe the intracluster medium identify possible interactions between the X-ray and radio emission measure cluster magnetic fields. -In the GAMMA-RAYS we study the intergalactic medium.

  11. 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.

  12. A multiwavelength survey of interacting galaxies

    NASA Technical Reports Server (NTRS)

    Bushouse, Howard A.; Lamb, Susan A.; Lo, K.-Y.; Lord, S.; Werner, M.

    1990-01-01

    Galaxy-galaxy collisions are known to produce drastic changes in morphology and, in many cases, enhance the level of star formation activity in galaxies. In order to better quantify the effects that interactions have on the star formation characteristics of galaxies the authors undertook a multiwavelength survey of a large sample of interacting disk-type galaxies. The sample is optically-selected, the inclusion of systems having been based upon the presence of unusual morphological features--such as tidal tails, plumes, rings, warped disks--suggestive of tidal interaction. The sample is composed of about 115 systems, most of which are spiral-spiral pairs, with a few spiral-elliptical pairs and a few merging systems (see Bushouse 1986 for more details of the sample selection). This sample has now been studied in the optical, infrared, and radio regimes, including optical spectra and H alpha images, near-infrared photometry and imaging, far-infrared photometry, H I 21 cm emission-line measurements, Very Large Array (VLA) 20 cm maps, and CO emission-line measurements. This paper presents an overview and comparison of the results of the optical, infrared and CO surveys. With these data the authors can compare the far-infrared and CO properties of the galaxies with the classic optical and radio indicators of star formation activity and thereby determine what, if any, relationships exist between star formation activity and the far-infrared and CO properties of the galaxies.

  13. Search for muon-neutrino emission from GeV and TeV gamma-ray flaring blazars using five years of data of the ANTARES telescope

    SciTech Connect

    Collaboration: 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.

  14. 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.

  15. Aerosol optical properties from multiwavelength lidar measurements in Romania

    NASA Astrophysics Data System (ADS)

    Nicolae, Doina; Talianu, Camelia; Carstea, Emil; Nemuc, Anca

    2009-09-01

    Vertically resolved profiles of optical properties of aerosols were measured using a multi-wavelength lidar system-RALI, set up at the scientific research center in Magurele, Bucharest area (44.35 N latitude, 26.03 E longitude) during 2008. The use of multiple laser wavelengths has enabled us to observe significant variations in backscatter profiles depending on the particle origins. An air mass backward trajectory analysis, using Hysplit-4, was carried out to track the aerosol plumes. Aerosols can serve as valuable tracers of air motion in the planetary boundary layer (PBL). The height of layers in the lower troposphere from lidar signal was calculated using the gradient method- minima of the first derivative. The Richardson number method was used to estimate PBL height from the radio-soundings. We have used pressure, temperature and dew point profiles as well as the wind direction profiles from NOAA (National Oceanic and Atmospheric Administration) data base. The results were consistent with the ones obtained from LIDAR.

  16. 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.

  17. COLLISION-INDUCED MAGNETIC RECONNECTION AND A UNIFIED INTERPRETATION OF POLARIZATION PROPERTIES OF GRBs AND BLAZARS

    DOE PAGES

    Deng; Zhang; Zhang; ...

    2016-04-11

    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 resultsmore » to model the polarization observational data of GRB prompt emission and blazar optical emission. In this article, 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.« less

  18. COLLISION-INDUCED MAGNETIC RECONNECTION AND A UNIFIED INTERPRETATION OF POLARIZATION PROPERTIES OF GRBs AND BLAZARS

    SciTech Connect

    Deng, Wei; Zhang, Bing; Zhang, Haocheng; Li, Hui E-mail: zhang@physics.unlv.edu E-mail: hz193909@ohio.edu

    2016-04-10

    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.

  19. COLLISION-INDUCED MAGNETIC RECONNECTION AND A UNIFIED INTERPRETATION OF POLARIZATION PROPERTIES OF GRBs AND BLAZARS

    SciTech Connect

    Deng , Wei; Zhang , Haocheng; Zhang , Bing; Li , Hui

    2016-04-11

    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. In this article, 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.

  20. A proton synchrotron blazar model for flaring in Markarian 501

    NASA Astrophysics Data System (ADS)

    Mücke, A.; Protheroe, R. J.

    2001-03-01

    The spectral energy distribution (SED) of gamma-ray (γ-ray) loud BL Lac objects typically has a double-humped appearance usually interpreted in terms of synchrotron self-Compton models. In proton blazar models, the SED is instead explained in terms of acceleration of protons and subsequent cascading. We discuss a variation of the synchrotron proton blazar model, first proposed by Mücke and Protheroe (Proc. Workshop GeV-TeV Astrophysics: Toward a Major Atmospheric Cherenkov Telescope VI, Snowbird, Utah, submitted for publication), in which the low energy part of the SED is mainly proton synchrotron radiation by electrons co-accelerated with protons, which produce the high energy part of the SED mainly as synchrotron radiation. As an approximation, we assume non-relativistic shock acceleration which could apply if the bulk of the plasma in the jet frame were non-relativistic. Our results may therefore change if a relativistic equation of state was used. We consider the case where the maximum energy of the accelerated protons is above the threshold for pion photoproduction interactions on the synchrotron photons of the low energy part of the SED. Using a Monte Carlo/numerical technique to simulate the interactions and subsequent cascading of the accelerated protons, we are able to fit the high-energy γ-ray portion of the observed SED of Markarian 501 during the April 1997 flare. We find that the emerging cascade spectra initiated by γ-rays from π 0 decay and by e ± from μ ± decay turn out to be relatively featureless. Synchrotron radiation produced by μ ± from π ± decay, and even more importantly by protons, and subsequent synchrotron-pair cascading, is able to reproduce well the high energy part of the SED. For this fit, we find that synchrotron radiation by protons dominates the TeV emission, pion photoproduction being less important with the consequence that we predict a lower neutrino flux than in other proton blazar models.

  1. 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

  2. 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.

  3. OPTICAL SPECTROSCOPIC OBSERVATIONS OF GAMMA-RAY BLAZAR CANDIDATES. V. TNG, KPNO, AND OAN OBSERVATIONS OF BLAZAR CANDIDATES OF UNCERTAIN TYPE IN THE NORTHERN HEMISPHERE

    SciTech Connect

    Álvarez Crespo, N.; Massaro, F.; Masetti, N.; Ricci, F.; La Franca, F.; Landoni, M.; Patiño-Álvarez, V.; Chavushyan, V.; Torrealba, J.; D’Abrusco, R.; Paggi, A.; Smith, Howard A.; Jiménez-Bailón, E.; Latronico, L.; Tosti, G.

    2016-02-15

    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.

  4. Supercontinuum generation using continuous-wave multiwavelength pumping and dispersion management.

    PubMed

    Sylvestre, Thibaut; Vedadi, Armand; Maillotte, Hervé; Vanholsbeeck, Frédérique; Coen, Stéphane

    2006-07-01

    We experimentally demonstrate that continuous-wave supercontinuum generation in optical fibers can be significantly enhanced by using both multiwavelength pumping and dispersion management. We show by detailed spectral analysis that continuum enhancement is achieved mainly through a combination of Raman-assisted modulation instabilities, soliton compression, and dispersive wave generation. With this technique, an 800 nm wide (from 1.2 to 2.0 microm) 2 W supercontinuum source is reported that uses a three-wavelength pump and a dispersion-tailored four-optical fibers arrangement.

  5. James Webb Space Telescope primary mirror integration: testing the multiwavelength interferometer on the test bed telescope

    NASA Astrophysics Data System (ADS)

    Olczak, Gene; Fischer, David J.; Connelly, Mark; Wells, Conrad

    2011-09-01

    The James Webb Space Telescope (JWST) integration includes a center of curvature test on its 18 primary mirror segment assemblies (PMSAs). This important test is the only ground test that will demonstrate the ability to align all 18 PMSAs. Using a multi-wavelength interferometer (MWIF) integrated to the test bed telescope (TBT), a one-sixth scale model of the JWST, we verify our ability to align and phase the 18 PMSAs. In this paper we will discuss data analysis and test results when using the MWIF to align the segments of the TBT in preparation for alignment of the JWST.

  6. 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.

  7. 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.

  8. Radio variability of the blazar AO 0235 + 164

    NASA Technical Reports Server (NTRS)

    O'Dell, S. L.; Dennison, B.; Broderick, J. J.; Altschuler, D. R.; Condon, J. J.; Payne, H. E.; Mitchell, K. J.

    1988-01-01

    The high-redshift blazar A0 0235 + 164 exhibits flux-density variations which are primarily of the less common variety in which low-frequency flux-density variations track the high-frequency variations but are delayed and of smaller amplitude. Observational results based on five years of monitoring are presented which are correlated over at least a factor of 50 frequency range in the sense expected for an expanding synchrotron component: outbursts propagating toward lower frequencies with diminishing amplitudes. A simple, semiempirical jet model is developed which accounts reasonably well for the radio properties of the object. The predictions of the model are compared with observations, examining the radio flux-density histories, the radio spectral evolution, the radio structure, and evidence for relativistic bulk motion.

  9. 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.

  10. 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.

  11. 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

  12. 0. 35-3. 5 micron photometry of blazars

    SciTech Connect

    Sitko, M.L.; Sitko, A.K. Cincinnati Observatory, OH )

    1991-02-01

    Thirty-one blazars were observed photometrically in the near-infrared, with additional observations in the optical for many of them. A few of them exhibit spectral behavior indicative of multiple emission components or emission processes. Six objects were also analyzed for any possible correlation between spectral steepness and luminosity. In one object, 0735 + 178, the spectral index alpha is correlated with the flux level with 99.9 pct confidence. Two other objects, 0846 + 513 and 0851 + 202, showed similar correlations at the 98 and 90 pct confidence levels, respectively. In all three cases the spectrum became flatter at higher flux levels. the data are consistent with expectations of models of inhomogeneous synchrotron models. In some cases, the self-Compton component may contribute significantly to the optical flux. 27 refs.

  13. Long-term monitoring of PKS 0537-441 with Fermi-LAT and multiwavelength observations

    NASA Astrophysics Data System (ADS)

    D'Ammando, F.; Antolini, E.; Tosti, G.; Finke, J.; Ciprini, S.; Larsson, S.; Ajello, M.; Covino, S.; Gasparrini, D.; Gurwell, M.; Hauser, M.; Romano, P.; Schinzel, F.; Wagner, S. J.; Impiombato, D.; Perri, M.; Persic, M.; Pian, E.; Polenta, G.; Sbarufatti, B.; Treves, A.; Vercellone, S.; Wehrle, A.; Zook, A.

    2013-05-01

    We report on multiwavelength observations of the blazar PKS 0537-441 (z = 0.896) obtained from microwaves through γ-rays by Submillimeter Array, Rapid Eye Mounting, Automatic Telescope for Optical Monitoring (ATOM), Swift and Fermi mostly during 2008 August-2010 April. Strong variability has been observed in γ-rays, with two major flaring episodes (2009 July and 2010 March) and a harder-when-brighter behaviour, quite common for flat spectrum radio quasars and low-synchrotron-peaked BL Lacertae objects (BL Lacs), in 2010 March. In the same way, the spectral energy distribution (SED) of the source cannot be modelled by a simple synchrotron self-Compton model, as opposed to many BL Lacs, but the addition of an external Compton component of seed photons from a dust torus is needed. The 230 GHz light curve showed an increase simultaneous with the γ-ray one, indicating co-spatiality of the mm and γ-ray emission region likely at large distance from the central engine. The low, average, and high activity SED of the source could be fit changing only the electron distribution parameters, but two breaks in the electron distribution are necessary. The ensuing extra spectral break, located at near-infrared (NIR)-optical frequencies, together with that in γ-rays seem to indicate a common origin, most likely due to an intrinsic feature in the underlying electron distribution. An overall correlation between the γ-ray band with the R band and K band has been observed with no significant time lag. On the other hand, when inspecting the light curves on short time-scales some differences are evident. In particular, flaring activity has been detected in NIR and optical bands with no evident γ-ray counterparts in 2009 September and November. Moderate variability has been observed in X-rays with no correlation between flux and photon index. An increase of the detected X-ray flux with no counterpart at the other wavelengths has been observed in 2008 October, suggesting once more a

  14. Coordinated Multiwavelength Observation of 3C 66A during the WEBT Campaign of 2003-2004

    NASA Astrophysics Data System (ADS)

    Böttcher, M.; Harvey, J.; Joshi, M.; Villata, M.; Raiteri, C. M.; Bramel, D.; Mukherjee, R.; Savolainen, T.; Cui, W.; Fossati, G.; Smith, I. A.; Able, D.; Aller, H. D.; Aller, M. F.; Arkharov, A. A.; Augusteijn, T.; Baliyan, K.; Barnaby, D.; Berdyugin, A.; Benítez, E.; Boltwood, P.; Carini, M.; Carosati, D.; Ciprini, S.; Coloma, J. M.; Crapanzano, S.; de Diego, J. A.; Di Paola, A.; Dolci, M.; Fan, J.; Frasca, A.; Hagen-Thorn, V.; Horan, D.; Ibrahimov, M.; Kimeridze, G. N.; Kovalev, Y. A.; Kovalev, Y. Y.; Kurtanidze, O.; Lähteenmäki, A.; Lanteri, L.; Larionov, V. M.; Larionova, E. G.; Lindfors, E.; Marilli, E.; Mirabal, N.; Nikolashvili, M.; Nilsson, K.; Ohlert, J. M.; Ohnishi, T.; Oksanen, A.; Ostorero, L.; Oyer, G.; Papadakis, I.; Pasanen, M.; Poteet, C.; Pursimo, T.; Sadakane, K.; Sigua, L. A.; Takalo, L.; Tartar, J. B.; Teräsranta, H.; Tosti, G.; Walters, R.; Wiik, K.; Wilking, B. A.; Wills, W.; Xilouris, E.; Fletcher, A. B.; Gu, M.; Lee, C.-U.; Pak, S.; Yim, H.-S.

    2005-09-01

    The BL Lac object 3C 66A was the target of an extensive multiwavelength monitoring campaign from 2003 July through 2004 April (with a core campaign from 2003 September to 2003 December) involving observations throughout the electromagnetic spectrum. Radio, infrared, and optical observations were carried out by the WEBT-ENIGMA collaboration. At higher energies, 3C 66A was observed in X-rays (RXTE), and at very high energy (VHE) in γ-rays (STACEE, VERITAS). In addition, the source has been observed with the VLBA at nine epochs throughout the period 2003 September to 2004 December, including three epochs contemporaneous with the core campaign. A gradual brightening of the source over the course of the campaign was observed at all optical frequencies, culminating in a very bright maximum around 2004 February 18. The WEBT campaign revealed microvariability with flux changes of ~5% on timescales as short as ~2 hr. The source was in a relatively bright state, with several bright flares on timescales of several days. The spectral energy distribution (SED) indicates a νFν peak in the optical regime. A weak trend of optical spectral hysteresis with a trend of spectral softening throughout both the rising and decaying phases has been found. On longer timescales, there appears to be a weak indication of a positive hardness-intensity correlation for low optical fluxes, which does not persist at higher flux levels. The 3-10 keV X-ray flux of 3C 66A during the core campaign was historically high and its spectrum very soft, indicating that the low-frequency component of the broadband SED extends beyond ~10 keV. No significant X-ray flux and/or spectral variability was detected. STACEE and Whipple observations provided upper flux limits at >150 and >390 GeV, respectively. The 22 and 43 GHz data from the three VLBA epochs made between 2003 September and 2004 January indicate a rather smooth jet with only very moderate internal structure. Evidence for superluminal motion (8

  15. 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

  16. VLBI observations of four radio quasars at z > 4: blazars or not?

    NASA Astrophysics Data System (ADS)

    Cao, H. M.; Frey, S.; Gabányi, K. É.; Paragi, Z.; Yang, J.; Cseh, D.; Hong, X.-Y.; An, T.

    2017-01-01

    Blazars are active galactic nuclei (AGN) whose relativistic jets point nearly to the line of sight. Their compact radio structure can be imaged with very long baseline interferometry (VLBI) on parsec scales. Blazars at extremely high redshifts provide a unique insight into the AGN phenomena in the early Universe. We observed four radio sources at redshift z > 4 with the European VLBI Network (EVN) at 1.7 and 5 GHz. These objects were previously classified as blazar candidates based on X-ray observations. One of them, J2134-0419 is firmly confirmed as a blazar with our VLBI observations, due to its relativistically beamed radio emission. Its radio jet extended to ˜10 milli-arcsec scale makes this source a promising target for follow-up VLBI observations to reveal any apparent proper motion. Another target, J0839+5112 shows a compact radio structure typical of quasars. There is evidence for flux density variability and its radio "core" has a flat spectrum. However, the EVN data suggest that its emission is not Doppler-boosted. The remaining two blazar candidates (J1420+1205 and J2220+0025) show radio properties totally unexpected from radio AGN with small-inclination jet. Their emission extends to arcsec scales and the Doppler factors of the central components are well below 1. Their structures resemble that of double-lobed radio AGN with large inclination to the line of sight. This is in contrast with the blazar-type modeling of their multi-band spectral energy distributions. Our work underlines the importance of high-resolution VLBI imaging in confirming the blazar nature of high-redshift radio sources.

  17. Stability properties of multiwavelength, incoherent, dissipative spatial solitons.

    PubMed

    Ultanir, E A; Stegeman, G I; Lange, C H

    2005-03-01

    We have investigated the interaction between two dissipative spatial solitons of different frequencies in periodically patterned semiconductor optical amplifiers. The experimental results are in good agreement with the theory. Simulations suggest that multiwavelength interactions do not produce stable bound solitons unless the system's modeling equations are completely symmetric.

  18. Multiwavelength micropulse lidar in atmospheric aerosol study: signal processing

    NASA Astrophysics Data System (ADS)

    Posyniak, Michal; Malinowski, Szymon P.; Stacewicz, Tadeusz; Markowicz, Krzysztof M.; Zielinski, Tymon; Petelski, Tomasz; Makuch, Przemyslaw

    2011-11-01

    Multiwavelength micropulse lidar (MML) designed for continuous optical sounding of the atmosphere is presented. A specific signal processing technique applying two directional Kalman filtering is introduced in order to enhance signal to noise ratio. Application of this technique is illustrated with profiles collected in course of COAST 2009 and WRNP 2010 research campaigns.

  19. 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.

  20. 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.

  1. Multi-wavelength studies of wind driving cataclysmic variables

    NASA Astrophysics Data System (ADS)

    Witherick, Dugan Kenneth

    This thesis presents several case studies of disc winds from high-state cataclysmic variable stars, based on multi-wavelength time-series spectroscopy. The research presented here primarily focuses on three low-inclination, nova-like systems: RW Sextansis, V592 Cassiopeiae and BZ Camelopardalis. The aim was to derive and compare key spectral line diagnostics of the outflows, spanning a wide range of ionisation and excitation using (new) FUSE, HST, IUE and optical data. Analysis of the far-UV time-series of RW Sex reveals the wind to be highly variable but generally confined to between ~ -1000 and ~ 0 km/s for all ionisation states; no evidence of the wind at red-shifted velocities is found. This wind is modulated on the orbital period of the system and it is argued that the observed variability is due to changes in the blue-shifted absorption rather than a variable velocity emission. The Balmer profiles observed in the optical time-series of V592 Cas were found to be characterised by three components: a broad, shallow absorption trough, a narrow central emission and a blue-shifted absorption from the disc wind. The wind is also found to be modulated on the systems orbital period, although this modulation is slightly out of phase with the Balmer emission radial velocities. The wind of BZ Cam was found to behave very differently to that of RW Sex and V592 Cas. At times, it was seen (in the Balmer lines and some of the He I lines) to be extremely strong and variable but at other times is was seemingly not present; there was no evidence to suggest that it is modulated on the orbital or any other period. This study is an immense source of data on CV disc winds and importantly tries to parameterise three nova-like CVs to understand the similarities and differences between them and their winds.

  2. Multiwavelength Pyrometer Developed for Use at Elevated Temperatures in Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Ng, Daniel L.

    2003-01-01

    Researchers at the NASA Glenn Research Center have developed a unique multiwavelength pyrometer for aerospace applications. It has been shown to be a useful and versatile instrument for measuring the surface temperatures of ceramic zirconia thermal barrier coatings (TBCs) and alumina, even when their emissivity is unknown. The introduction of fiber optics into the pyrometer has greatly increased the ease of using this instrument. Direct comparison of measurements obtained using the pyrometer and thin film thermocouples on a sample provided independent verification of pyrometry temperature measurement. Application of the pyrometer has also included simultaneous surface and bulk temperature measurement in a transparent material, the measurement of combustion gas temperatures in the flames of an atmospheric burner, the measurement of the temperature distribution appearing on a large surface from the recording of just a single radiation spectrum emitted from this nonuniform temperature surface, and the measurement of some optical properties for special aeronautical materials-such as nanostructured layers. The multiwavelength pyrometer temperature is obtained from a radiation spectrum recorded over a broad wavelength region by transforming it into a straight line segment(s) in part or all of the spectral region. The intercept of the line segment(s) with the vertical axis at zero wavelength gives the inverse of the temperature. In a two-color pyrometer, the two data points are also amenable to this analysis to determine the unknown temperature. Implicit in a two-color pyrometer is the assumption of wavelength-independent emissivity. Its two (and minimum) pieces of data are sufficient to determine this straight line. However, a multiwavelength pyrometer not only has improved accuracy but also confirms that the wavelength-independent emissivity assumption is valid when a multitude of data points are shown to lie on a simple straight line.

  3. 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.

  4. 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

  5. VizieR Online Data Catalog: Blazars equivalent widths and radio luminosity (Landt+, 2004)

    NASA Astrophysics Data System (ADS)

    Landt, H.; Padovani, P.; Perlman, E. S.; Giommi, P.

    2004-07-01

    Blazars are currently separated into BL Lacertae objects (BL Lacs) and flat spectrum radio quasars based on the strength of their emission lines. This is performed rather arbitrarily by defining a diagonal line in the Ca H&K break value-equivalent width plane, following Marcha et al. (1996MNRAS.281..425M). We readdress this problem and put the classification scheme for blazars on firm physical grounds. We study ~100 blazars and radio galaxies from the Deep X-ray Radio Blazar Survey (DXRBS, Cat. and ) and 2-Jy radio survey and find a significant bimodality for the narrow emission line [OIII]{lambda}5007. This suggests the presence of two physically distinct classes of radio-loud active galactic nuclei (AGN). We show that all radio-loud AGN, blazars and radio galaxies, can be effectively separated into weak- and strong-lined sources using the [OIII]{lambda}5007-[OII]{lambda}3727 equivalent width plane. This plane allows one to disentangle orientation effects from intrinsic variations in radio-loud AGN. Based on DXRBS, the strongly beamed sources of the new class of weak-lined radio-loud AGN are made up of BL Lacs at the ~75 per cent level, whereas those of the strong-lined radio-loud AGN include mostly (~97 per cent) quasars. (4 data files).

  6. Multiwavelength Thermometry at High Temperature: Why It is Advantageous to Work in the Ultraviolet

    NASA Astrophysics Data System (ADS)

    Girard, F.; Battuello, M.; Florio, M.

    2014-07-01

    In principle, multiwavelength radiation thermometry allows one to correctly measure the temperature of surfaces of unknown and varying surface emissivity. Unfortunately, none of the practical realizations proposed in the past proved to be sufficiently reliable because of a strong influence of the errors arising from incorrect modeling of the emissivity and of the limited number of operating wavelengths. The use of array detectors allows a high degree of flexibility both in terms of number and spectral position of the working wavelength bands. In the case of applications at high temperatures, i.e., near 2000 C or above, an analysis of the theoretical measuring principles of multiwavelength thermometry, suggests the opportunity of investigating the possible advantages in extending the operating wavelengths toward the ultraviolet region. To this purpose, a simulation program was developed which allows investigation of the effect of different influencing parameters. This paper presents a brief theoretical introduction and practical analysis of the method. The best choices are derived in terms of the different influencing parameters and data relative to the simulation of both real materials and fictitious emissivity curves and have been studied and analyzed with different emissivity models to check the robustness of the method.

  7. VizieR Online Data Catalog: Blazars in the Swift-BAT hard X-ray sky (Maselli+, 2010)

    NASA Astrophysics Data System (ADS)

    Maselli, A.; Cusumano, G.; Massaro, E.; La Parola, V.; Segreto, A.; Sbarufatti, B.

    2010-06-01

    We reported the list of hard X-ray blazars obtained adopting sigma=3 as detection threshold: with this choice a number of three spurious sources over a total of 121 blazars is expected. 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 (1)" below. We obtained 69 FSRQs, 24 BL Lac objects and 28 blazars of uncertain classification, representing 4.4%, 2.4% and 11.0% of the corresponding populations classified in the BZCAT, respectively. This sample has been compared with other lists and catalogues found in literature (Tueller et al., 2010, Cat. J/ApJS/186/378, Ajello et al. 2009ApJ...699..603A, Cusumano et al., 2010, Cat. J/A+A/510/A48). (1 data file).

  8. Synchrotron and inverse-Compton emission from blazar jets - II. An accelerating jet model with a geometry set by observations of M87

    NASA Astrophysics Data System (ADS)

    Potter, William J.; Cotter, Garret

    2013-02-01

    In this paper we develop the jet model of Potter & Cotter to include a magnetically dominated accelerating parabolic base transitioning to a slowly decelerating conical jet with a geometry set by recent radio observations of M87. We conserve relativistic energy-momentum and particle number along the jet and calculate the observed synchrotron emission from the jet by calculating the integrated line-of-sight synchrotron opacity through the jet in the rest frame of each section of plasma. We calculate the inverse-Compton emission from synchrotron, cosmic microwave background (CMB), accretion disc, starlight, broad-line region (BLR), dusty torus and narrow-line region photons by transforming into the rest frame of the plasma along the jet. We fit our model to simultaneous multi-wavelength observations of the Compton-dominant FSRQ type blazar PKS 0227-369, with a jet geometry set by M87 and an accelerating bulk Lorentz factor consistent with simulations and theory. We investigate models in which the jet comes into equipartition at different distances along the jet and equipartition is maintained via the conversion of jet bulk kinetic energy into particle acceleration. We find that the jet must still be magnetically dominated within the BLR and cannot be in equipartition due to the severe radiative energy losses. The model fits the observations, including radio data, very well if the jet comes into equipartition outside the BLR within the dusty torus (1.5 pc) or at further distances (34 pc). The fits require a high-power jet with a large bulk Lorentz factor observed close to the line of sight, consistent with our expectations for a Compton-dominant blazar. We find that our fit in which the jet comes into equipartition furthest along the jet, which has a jet with the geometry of M87 scaled linearly with black hole mass, has an inferred black hole mass close to previous estimates. This implies that the jet of PKS 0227 might be well described by the same jet geometry as M87.

  9. 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.

    2010-03-01

    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

  10. Searching for Hard X-Ray Emission from Radio-Loud Gamma-Ray Quiet Blazars

    NASA Astrophysics Data System (ADS)

    Wada, Katelyn R.; Macomb, Daryl J.

    2017-01-01

    While the Swift BAT AGN source catalog is dominated by radio-quiet Seyfert AGN, around 15% of the sample are radio galaxies or blazars (Ajello et al., 2009). There is an overlap of about 40 sources between the Fermi LAT and Swift BAT detected AGN populations, only a few percent of the Fermi total. These small numbers are presumably a result of selection bias as the SSC peak often falls squarely within the Fermi LAT bandpass while the Swift BAT sensitivity is highest in the spectral region straddling the synchrotron and SSC components.Recently however, a significant sample of bright (F 15GHz >1.5 Jy), radio selected AGN was found, surprisingly, to overlap with Fermi at only the ~80% level (Lister et. al., 2015). This could be a result of selection bias as well as the gamma-ray quiet objects of that survey having synchrotron peak frequencies of 10^13.4 Hz or less. On the other hand it could be due to deficient Doppler boosting among that ~20%. One can, in principle, test the former possibility by assessing emission from the low-energy wings of putative sub-GeV peaked SSC components. We describe our ongoing joint Swift BAT analysis project that attempts to address this possibility. Initial results, comparisons with INTEGRAL observations, and conclusions are presented.

  11. VizieR Online Data Catalog: Gamma-ray bright blazars spectrophotometry (Williamson+, 2014)

    NASA Astrophysics Data System (ADS)

    Williamson, K. E.; Jorstad, S. G.; Marscher, A. P.; Larionov, V. M.; Smith, P. S.; Agudo, I.; Arkharov, A. A.; Blinov, D. A.; Casadio, C.; Efimova, N. V.; Gomez, J. L.; Hagen-Thorn, V. A.; Joshi, M.; Konstantinova, T. S.; Kopatskaya, E. N.; Larionova, E. G.; Larionova, L. V.; Malmrose, M. P.; McHardy, I. M.; Molina, S. N.; Morozova, D. A.; Schmidt, G. D.; Taylor, B. W.; Troitsky, I. S.

    2017-03-01

    Since 2007, we have been collecting multi-waveband fluxes, polarization measurements, and radio images of blazars to provide the data for understanding the physics of the jets (see, e.g., Marscher 2012, arXiv:1201.5402). This study includes 28 of the original 30 objects selected for the monitoring campaign, confirmed as γ-ray sources by EGRET (Energetic γ-Ray Experiment Telescope) on the Compton Gamma Ray Observatory, have an R-band brightness exceeding 18 mag (bright enough for optical polarization measurements at a 1-2 m class optical telescope without needing excessive amounts of telescope time), exceed 0.5 Jy at 43 GHz, and have a declination accessible to the collaboration's observatories (> - 30°). Three additional BL Lacs (1055+018, 1308+326, and 1749+096) and two FSRQs (3C345 and 3C446) included in this analysis were among those added when they were detected as γ-ray sources by the Fermi LAT (Abdo et al. 2009, J/ApJ/700/597). (4 data files).

  12. 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.

  13. 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

  14. 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.

  15. 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.

  16. 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.

  17. [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.

  18. 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.

  19. 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.

  20. 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.

  1. On radiative acceleration in spine-sheath structured blazar jets

    NASA Astrophysics Data System (ADS)

    Chhotray, A.; Nappo, F.; Ghisellini, G.; Salafia, O. S.; Tavecchio, F.; Lazzati, D.

    2017-04-01

    It has been proposed that blazar jets are structured, with a fast spine surrounded by a slower sheath or layer. This structured jet model explains some properties of their emission and morphology. Because of their relative motion, the radiation produced by one component is seen amplified by the other, thus enhancing the inverse Compton emission of both. Radiation is emitted anisotropically in the comoving frames and causes the emitting plasma to recoil. As seen in the observer frame, this corresponds to a deceleration of the fastest component (the spine) and an acceleration of the slower one (the layer). While the deceleration of the spine has already been investigated, here we study for the first time the acceleration of the sheath and find self-consistent velocity profile solutions for both the spine and the sheath while accounting for radiative cooling. We find that the sheath can be accelerated to the velocities required by the observations if its leptons remain energetic in the acceleration region, assumed to be of the order of ∼100 Schwarzschild radii, demanding continuous injection of energetic particles in that region.

  2. Search for Magnetically Broadened Cascade Emission from Blazars with VERITAS

    NASA Astrophysics Data System (ADS)

    Archambault, S.; Archer, A.; Benbow, W.; Buchovecky, M.; Bugaev, V.; Cerruti, M.; Connolly, M. P.; Cui, W.; Falcone, A.; Fernández Alonso, M.; Finley, J. P.; Fleischhack, H.; Fortson, L.; Furniss, A.; Griffin, S.; Hütten, M.; Hervet, O.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kieda, D.; Krause, M.; Krennrich, F.; Lang, M. J.; Lin, T. T. Y.; Maier, G.; McArthur, S.; Moriarty, P.; Nieto, D.; O’Brien, S.; Ong, R. A.; Otte, A. N.; Pohl, M.; Popkow, A.; Pueschel, E.; Quinn, J.; Ragan, K.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Rovero, A. C.; Sadeh, I.; Shahinyan, K.; Staszak, D.; Telezhinsky, I.; Tyler, J.; Wakely, S. P.; Weinstein, A.; Weisgarber, T.; Wilcox, P.; Wilhelm, A.; Williams, D. A.; Zitzer, B.

    2017-02-01

    We present a search for magnetically broadened gamma-ray emission around active galactic nuclei (AGNs), using VERITAS observations of seven hard-spectrum blazars. A cascade process occurs when multi-TeV gamma-rays from an AGN interact with extragalactic background light (EBL) photons to produce electron–positron pairs, which then interact with cosmic microwave background photons via inverse-Compton scattering to produce gamma-rays. Due to the deflection of the electron–positron pairs, a non-zero intergalactic magnetic field (IGMF) would potentially produce detectable effects on the angular distribution of the cascade emission. In particular, an angular broadening compared to the unscattered emission could occur. Through non-detection of angularly broadened emission from 1ES 1218+304, the source with the largest predicted cascade fraction, we exclude a range of IGMF strengths around 10‑14 G at the 95% confidence level. The extent of the exclusion range varies with the assumptions made about the intrinsic spectrum of 1ES 1218+304 and the EBL model used in the simulation of the cascade process. All of the sources are used to set limits on the flux due to extended emission.

  3. 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.

  4. 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).

  5. 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.

  6. 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.

  7. The international AGN watch: A multiwavelength monitoring consortium

    NASA Technical Reports Server (NTRS)

    Alloin, D.; Clavel, J.; Peterson, B. M.; Reichert, G. A.; Stirpe, G. M.

    1994-01-01

    The International AGN Watch, an informal consortium of over 100 astronomers, was established to coordinate multiwavelength monitoring of a limited number of active galactic nuclei and thus obtain comprehensive continuum and emission-line variability data with unprecedented temporal and wavelength coverage. We summarize the principal scientific results from two completed space-based and ground-based campaigns on the Seyfert galaxies NGC 5548 and NGC 3783. We describe a project in progress and outline our future plans.

  8. 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.

  9. Multiwavelength parallel phase-shifting digital holography using angular multiplexing.

    PubMed

    Tahara, Tatsuki; Ito, Yasunori; Lee, Yonghee; Xia, Peng; Inoue, Junichi; Awatsuji, Yasuhiro; Nishio, Kenzo; Ura, Shogo; Kubota, Toshihiro; Matoba, Osamu

    2013-08-01

    We propose a single-shot digital holography for recording multiwavelength and complex amplitude information by using a single monochromatic image sensor. The zeroth-order wave and conjugate image in each wavelength are removed from a recorded single hologram by applying parallel phase-shifting interferometry. Angular multiplexing is utilized to record the complex amplitude of an object wave in each wavelength separately, and no color filter is required. The effectiveness of the proposed technique was experimentally verified.

  10. Multiwavelength generation in a random distributed feedback fiber laser using an all fiber Lyot filter.

    PubMed

    Sugavanam, S; Yan, Z; Kamynin, V; Kurkov, A S; Zhang, L; Churkin, D V

    2014-02-10

    Multiwavelength lasing in the random distributed feedback fiber laser is demonstrated by employing an all fiber Lyot filter. Stable multiwavelength generation is obtained, with each line exhibiting sub-nanometer line-widths. A flat power distribution over multiple lines is obtained, which indicates that the power between lines is redistributed in nonlinear mixing processes. The multiwavelength generation is observed both in first and second Stokes waves.

  11. 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.

  12. Searching for γ-ray signature in WHSP blazars. Fermi-LAT detection of 150 excess signal in the 0.3-500 GeV band

    NASA Astrophysics Data System (ADS)

    Arsioli, B.; Chang, Y.-L.

    2017-02-01

    Aims: A direct search of γ-ray emission centered on multifrequency selected candidates is a valuable complementary approach to the standard search adopted in current γ-ray Fermi-LAT catalogs. Our sources are part of the 2WHSP sample that was assembled with the aim of providing targets for Imaging Atmospheric Cherenkov Telescopes (IACT). A likelihood analysis based on their known position enabled us to detect 150 γ-ray excess signals that have not yet been reported in previous γ-ray catalogs (1FGL, 2FGL, 3FGL). By identifying new sources, we solve a fraction of the extragalactic isotropic γ-ray background (IGRB) composition, improving the description of the γ-ray sky. Methods: We perform data reduction with the Fermi Science Tools using positions from 400 high synchrotron peaked (HSP) blazars as seeds of tentative γ-ray sources; none of them have counterparts from previous 1FGL, 2FGL and 3FGL catalogs. Our candidates are part of the 2WHSP sample (currently the largest set of HSP blazars). We focus on HSPs characterized by bright synchrotron component with peak flux νf(ν) ≥ 10-12.1 erg/cm2/s, testing the hypothesis of having a γ-ray source in correspondence to the WHSP positions. Our likelihood analysis considers the 0.3-500 GeV energy band, integrating over 7.2 yr of Fermi-LAT observation and making use of the Pass 8 data release. Results: From the 400 candidates tested, a total of 150 2WHSPs showed excess γ-ray signature: 85 high-significance detections with test statistic (TS) > 25, and 65 lower-significance detections with TS between 10 to 25. We assume a power law spectrum in the 0.3-500 GeV band and list the spectrum parameters describing all 150 new γ-ray sources. We study the γ-ray photon spectral index distribution, the likelihood of detection according to the synchrotron peak brightness (figure of merit parameter), and plot the measured γ-ray LogN-LogS of HSP blazars, also discussing the portion of the IGRB that has been resolved by the

  13. 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.

  14. Community-level microalgal toxicity assessment by multiwavelength-excitation PAM fluorometry.

    PubMed

    Schmitt-Jansen, Mechthild; Altenburger, Rolf

    2008-01-20

    In ecotoxicological studies involving community-level investigations, rapid and multiparametric fluorescence-based methods may provide substantial advantages over traditional methods used for structural and functional community analysis. Therefore, multiwavelength-excitation pulse-amplitude modulated (PAM) fluorometry was applied in this study to assess long-term changes in periphyton community structure, short-term effects on periphyton functioning (photosynthesis) and pollution induced community tolerance (PICT). For inter-calibration, periphyton structure was evaluated by chemotaxonomic analysis of accessory pigments and a four-wavelength-excitation PAM fluorometer. Short-term effects of herbicides were evaluated by fluorescence quenching analysis and (14)C-incorporation as a proxy of primary production. Subsequently, the method was applied to assess structural and functional changes in periphyton communities after isoproturon exposure for 14 and 26 days, respectively. Results showed good correlation of the PAM fluorescence-based measurements with traditional methods for biofilms in the initial colonisation phase for structural and functional parameters. However, for biofilms older than 9 weeks PAM fluorescence may underestimate biomass. Multiwavelength-excitation PAM fluorometry showed good correlation with marker pigment concentrations indicating that this method provides a reliable estimate of the community structure. PAM fluorometry was able to quantify changes of biomass and follow relative shifts in class composition of biofilms under exposure of isoproturon. Short-term tests based on the quantification of the inhibition of the effective quantum yield revealed a concentration-dependent increase of PICT. The observation of two succession phases of the biofilms after 14 and 26 days of growth, respectively, revealed that sensitivity of biofilms decreased with increasing age and biomass, respectively, but PICT remained a characteristic parameter of exposed

  15. 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.

  16. Decelerating Flows in the TeV Blazars

    NASA Technical Reports Server (NTRS)

    Kazanas, Demosthenes

    2004-01-01

    TeV emission from a class of BL Lacertae (BL) objects is commonly modeled as radiation from relativistically moving homogeneous plasma blobs. In the context of these models, the blob Lorentz factors needed to reproduce the (corrected for absorption by the IR background) TeV emission are large ($\\delta \\gtrsim 50$) are required to reproduce via Synchrotron-Self Compton (SSC) the observed TeV emission. The main reason for this is that stronger beaming eases the problem of the lack of $\\sim$ IR-UV synchrotron seed photons needed to produce the de-absorbed $\\sim$ few TeV peak of the spectral energy distribution (SED). However, such high Doppler factors are in strong disagreement with the unified scheme, according to which BLs are FR I radio galaxies with their jets closely aligned to the line of sight. Here, motivated by the detection of sub-luminal velocities in the sub-pc scale jets of the best studied TeV blazars, MKN 421 and MKN 501. we examine the possibility that the relativistic flow in the TeV BLs is longitudinally decelerating. In this case, the problem of the missing seed photons is solved due to Upstream Compton (UC) scattering, a process in which the upstream energetic electrons from the fast base of the flow 'see' the synchrotron seed photons produced in the slow part of the flow relativistically beamed. Modest Lorentz factors ($\\Gamma kim 15s). decelerating down to values compatible with the recent radio interferometric observations, reproduce the $\\sim$ few TeV peak energy of these sources. Furthermore, such decelerating flows are shown to be in agreement with the BL - FR I unification.

  17. Curvature of the spectral energy distributions of blazars

    SciTech Connect

    Chen, Liang

    2014-06-20

    In this paper, spectral energy distributions (SED) of both synchrotron and inverse Compton (IC) components of a sample of Fermi bright blazars are fitted by a log-parabolic law. The second-degree term of the log parabola measures the curvature of an SED. We find a statistically significant correlation between the synchrotron peak frequency and its curvature. This result is in agreement with the theoretical prediction and confirms previous studies that dealt with a single source with observations at various epochs or a small sample. If a broken power law is employed to fit the SED, the difference between the two spectral indices (i.e., |α{sub 2} – α{sub 1}|) can be considered a 'surrogate' of the SED curvature. We collect data from the literature and find a correlation between the synchrotron peak frequency and the spectral difference. We do not find a significant correlation between the IC peak frequency and its curvature, which may be caused by a complicated seed photon field. It is also found that the synchrotron curvatures are on average larger than those of IC curvatures, and there is no correlation between these two parameters. As suggested by previous works, both the log-parabolic law of the SED and the above correlation can be explained by statistical and/or stochastic particle accelerations. Based on a comparison of the slops of the correlation, our result seems to favor stochastic acceleration mechanisms and emission processes. Additional evidence, including SED modeling, particle acceleration simulation, and comparisons between some predictions and empirical relations/correlations, also seems to support the idea that the electron energy distribution (and/or synchrotron SED) may be log-parabolic.

  18. Fermi LAT detection of renewed GeV activity from blazar 3C 279

    NASA Astrophysics Data System (ADS)

    Ciprini, Stefano; Gonzalez, Josefa Becerra

    2014-04-01

    The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed high-level gamma-ray activity from a source positionally consistent with the blazar 3C 279 (RA: 194.046527 deg, Dec: -5.789312 deg, J2000; Johnston et al.1995, AJ, 110, 880). ...

  19. Extremes of the jet–accretion power relation of blazars, as explored by NuSTAR

    DOE PAGES

    Sbarrato, T.; Ghisellini, G.; Tagliaferri, G.; ...

    2016-07-18

    Hard X-ray observations are crucial to study the non-thermal jet emission from high-redshift, powerful blazars. We observed two bright z > 2 flat spectrum radio quasars (FSRQs) in hard X-rays to explore the details of their relativistic jets and their possible variability. S5 0014+81 (at z = 3.366) and B0222+185 (at z=2.690) have been observed twice by the Nuclear Spectroscopic Telescope Array (NuSTAR) simultaneously with Swift/XRT, showing different variability behaviors. We found that NuSTAR is instrumental to explore the variability of powerful high-redshift blazars, even when no gamma-ray emission is detected. The two sources have proven to have respectively themore » most luminous accretion disk and the most powerful jet among known blazars. Furthermore, thanks to these properties, they are located at the extreme end of the jet-accretion disk relation previously found for gamma-ray detected blazars, to which they are consistent.« less

  20. 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.

  1. VERITAS OBSERVATIONS OF SIX BRIGHT, HARD-SPECTRUM FERMI-LAT BLAZARS

    SciTech Connect

    Aliu, E.; Errando, M.; Archambault, S.; Arlen, T.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Boettcher, M.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Collins-Hughes, E.; Cui, W.; Duke, C.; Dumm, J.; Falcone, A. E-mail: pafortin@cfa.harvard.edu; Collaboration: VERITAS Collaboration; and others

    2012-11-10

    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 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 X-Ray Telescope 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 shows a synchrotron peak bordering between the intermediate- and high-spectrum-peak classifications, with four of the six resulting in particle-dominated emission regions.

  2. Hidden Parents Of High-Z Blazars: Quencing And Dark Bubbles

    NASA Astrophysics Data System (ADS)

    Sbarrato, Tullia; Ghisellini, G.

    2016-10-01

    At redshift larger than 3 a relevant disagreement arises between the number of blazars (with jets aligned to our line-of-sight) and their parent population (with jets pointing elsewhere). We are missing the high-redshift blazars misaligned counterparts in our optical and radio surveys. Are we losing the optical nuclear emission or the extended radio flux? On one side, we could be missing the most misaligned sources, whose radio emission from their extended structures is likely quenched by the CMB energy density. But we also find a discrepancy between blazars and their slightly misaligned counterparts: we are missing slightly misaligned jets, too. This cannot be ascribed only to a quenched extended emission. I will show that an over- developed dusty structure can account for the missing misaligned population: bubbles of dust covering the nuclear region could completely obscure it. The jet can pierce the bubble, leaving visible the optical nucleus only if observing down the jet axis. This hypothesis would justify the relevant lack of parents, compared to the number of blazars that we keep finding at z>4.

  3. 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.

  4. Detecting the Attenuation of Blazar Gamma-ray Emission by Extragalactic Background Light with GLAST

    NASA Technical Reports Server (NTRS)

    Chen, Andrew; Ritz, Steven

    1999-01-01

    Gamma rays with energy above 10 GeV interact with optical-UV photons resulting in pair production. Therefore, a large sample of high redshift sources of these gamma rays can be used to probe the extragalactic background starlight (EBL) by examining the redshift dependence of the attenuation of the flux above 10 GeV. GLAST, the next generation high-energy gamma-ray telescope, will for the first time have the unique capability to detect thousands of gamma-ray blazars up to redshifts of at least z = 4, with enough angular resolution to allow identification of a large fraction of their optical counterparts. By combining recent determinations of the gamma-ray blazar luminosity function, recent calculations of the high energy gamma-ray opacity due to EBL absorption, and the expected GLAST instrument performance to produce simulated samples of blazars that GLAST would detect, including their redshifts and fluxes, we demonstrate that these blazars have the potential to be a highly effective probe of the EBL.

  5. Optical flare observed in the flaring gamma-ray blazar S5 1044+71

    NASA Astrophysics Data System (ADS)

    Pursimo, Tapio; Blay, Pere; Telting, John; Ojha, Roopesh

    2017-01-01

    We report optical photometry of the blazar S5 1044+71, obtained with the 2.56m Nordic Optical Telescope in La Palma, to look for any enhanced optical activity associated with a recent flare in the daily averaged gamma-ray flux (ATel#9928).

  6. 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.

  7. Recent radio activity of the Fermi blazar 4C +38.41

    NASA Astrophysics Data System (ADS)

    Myserlis, I.; Angelakis, E.; Fuhrmann, L.; Karamanavis, V.; Nestoras, I.; Krichbaum, T. P.; Zensus, J. A.; Ungerechts, H.; Sievers, A.

    2012-10-01

    We report the recent activity (raising flux density) seen in the monitored blazar 4C +38.41 (J1635+3808, RA= 16:35:16, DEC=+38:08:05 in J2000), as recorded within the framework of the F-GAMMA program responding to ATels #4389, #4400 and #4437 (gamma, NIR and optical respectively).

  8. Recent radio activity of the Fermi blazar S5 0716+714

    NASA Astrophysics Data System (ADS)

    Myserlis, I.; Angelakis, E.; Fuhrmann, L.; Karamanavis, V.; Nestoras, I.; Krichbaum, T. P.; Zensus, J. A.; Ungerechts, H.; Sievers, A.

    2012-10-01

    We report the recent activity (raising flux density) seen in the monitored blazar S5 0716+714 (J0721+7120, RA= 07:21:53, DEC=+71:20:36 in J2000) as recorded within the framework of the F-GAMMA program responding to ATel #4437 (optical).

  9. 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.

  10. 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

  11. 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

  12. Estimating the distribution of rest-frame time-scales for blazar jets: a statistical approach

    NASA Astrophysics Data System (ADS)

    Liodakis, I.; Blinov, D.; Papadakis, I.; Pavlidou, V.

    2017-03-01

    In any flux-density limited sample of blazars, the distribution of the time-scale modulation factor Δt΄/Δt, which quantifies the change in observed time-scales compared to the rest-frame ones due to redshift and relativistic compression follows an exponential distribution with a mean depending on the flux limit of the sample. In this work, we produce the mathematical formalism that allows us to use this information in order to uncover the underlining rest-frame probability density function of measurable time-scales of blazar jets. We extensively test our proposed methodology using a simulated Flat Spectrum Radio Quasar population with a 1.5 Jy flux-density limit in the simple case (where all blazars share the same intrinsic time-scale), in order to identify limits of applicability and potential biases due to observational systematics and sample selection. We find that for monitoring with time intervals between observations longer than ∼30 per cent of the intrinsic time-scale under investigation the method loses its ability to produce robust results. For time intervals of ∼3 per cent of the intrinsic time-scale, the error of the method is as low as 1 per cent in recovering the intrinsic rest-frame time-scale. We applied our method to rotations of the optical polarization angle of blazars observed by RoboPol. We found that the intrinsic time-scales of the longest duration rotation event in each blazar follows a narrow distribution, well described by a normal distribution with mean 87 d and standard deviation 5 d. We discuss possible interpretations of this result.

  13. PATCHY BLAZAR HEATING: DIVERSIFYING THE THERMAL HISTORY OF THE INTERGALACTIC MEDIUM

    SciTech Connect

    Lamberts, Astrid; Chang, Philip; Pfrommer, Christoph; Puchwein, Ewald; Broderick, Avery E.; Shalaby, Mohamad

    2015-09-20

    TeV-blazars potentially heat the intergalactic medium (IGM) as their gamma rays interact with photons of the extragalactic background light to produce electron–positron pairs, which lose their kinetic energy to the surrounding medium through plasma instabilities. This results in a heating mechanism that is only weakly sensitive to the local density, and therefore approximately spatially uniform, naturally producing an inverted temperature–density relation in underdense regions. In this paper we go beyond the approximation of uniform heating and quantify the heating rate fluctuations due to the clustered distribution of blazars and how this impacts the thermal history of the IGM. We analytically compute a filtering function that relates the heating rate fluctuations to the underlying dark matter density field. We implement it in the cosmological code GADGET-3 and perform large-scale simulations to determine the impact of inhomogeneous heating. We show that because of blazar clustering, blazar heating is inhomogeneous for z ≳ 2. At high redshift, the temperature–density relation shows an important scatter and presents a low temperature envelope of unheated regions, in particular at low densities and within voids. However, the median temperature of the IGM is close to that in the uniform case, albeit slightly lower at low redshift. We find that blazar heating is more complex than initially assumed and that the temperature–density relation is not unique. Our analytic model for the heating rate fluctuations couples well with large-scale simulations and provides a cost-effective alternative to subgrid models.

  14. Polarization Signatures distinguish the kinetic- and the magnetic-driven blazar jet models

    NASA Astrophysics Data System (ADS)

    Zhang, Haocheng; Li, Hui; Taylor, Gregory B.

    2017-01-01

    Blazars are a type of active galaxies whose jets direct close to our line of sight. They exhibit strong variability across the entire electromagnetic spectrum, from radio up to TeV gamma-rays. The radio to optical polarization signatures, which originate from synchrotron emission in a partially ordered magnetic field, show strong variability as well. Two scenarios have been advanced to explain the blazar variability. The kinetic-driven model argues that the emission region can drain kinetic energy through shocks to accelerate nonthermal particles and generate flares. The magnetic-driven model suggests that the magnetic energy can dissipate through current-driven instabilities to fuel the variability. Both models have their merits in understanding blazar spectra and light curves during flares, thus they cannot be distinguished. We perform comprehensive polarization-dependent radiation modeling of shocks and kink instabilities in the blazar emission region, based on detailed relativistic magnetohydrodynamic (RMHD) simulations. Our approach involves self-consistent magnetic field evolution, nonthermal particle injection based on the energy release from the RMHD simulation, and detailed radiation transfer including all light travel time effects. Hence our method offers the self-consistent time-dependent radiation and polarization signatures from first principles. By comparing the shock and the kink models, we find that while both can interpret the light curves well, the shock model generally produce too strong polarization variations compared to observations. On the other hand, the kink model well fits the general polarization fluctuations and polarization angle swings. We conclude that by coupling first-principle simulations and detailed polarization-dependent radiaiton modeling, polarization signatures can probe the origin of the blazar jet variability, and offer a general diagnostic of the jet physics, including the energy composition, the particle acceleration, and

  15. Reconnection-driven plasmoids in blazars: fast flares on a slow envelope

    NASA Astrophysics Data System (ADS)

    Giannios, Dimitrios

    2013-05-01

    TeV flares of a duration of ˜10 min have been observed in several blazars. The fast flaring requires compact regions in the jet that boost their emission towards the observer at an extreme Doppler factor of δem ≳ 50. For ˜100 GeV photons to avoid annihilation in the broad-line region of PKS 1222+216, the flares must come from large (pc) scales, challenging most models proposed to explain them. Here I elaborate on the magnetic reconnection minijet model for the blazar flaring, focusing on the inherently time-dependent aspects of the process of magnetic reconnection. I argue that, for the physical conditions prevailing in blazar jets, the reconnection layer fragments, leading to the formation a large number of plasmoids. Occasionally, a plasmoid grows to become a large, `monster' plasmoid. I show that radiation emitted from the reconnection event can account for the observed `envelope' of day-long blazar activity, while radiation from monster plasmoids can power the fastest TeV flares. The model is applied to several blazars with observed fast flaring. The inferred distance of the dissipation zone from the black hole and the typical size of the reconnection regions are Rdiss ˜ 0.3-1 pc and l' ≲ 1016 cm, respectively. The required magnetization of the jet at this distance is modest: σ ˜ a few. Such distance Rdiss and reconnection size l' are expected if the jet contains field structures with a size of the order of the black hole horizon.

  16. 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.

  17. Multi-wavelength interferometer for high accuracy measurement of long gauge blocks

    NASA Astrophysics Data System (ADS)

    Wengierow, Michal; Salbut, Leszek; Pakula, Anna; Lukaszewski, Dariusz

    2008-08-01

    In the paper the multiwavelength interferometer with automatic data analysis based on phase fraction method is described. It is used to extend measurement range without losing sensitivity, especially to calibrate long gauge blocks. Numerical simulations and experimental work results have been shown to confirm proper functioning of this method. However, stabilization of environmental conditions and light sources has significant influence on correctness of measurement results. To match those requirements measurement system, which will be built for Polish Central Office of Measures, has been designed. This design is based on Twyman-Green interferometer and assumes usage of two highly stabilized laser sources. Optical and mechanical design of this system has been shown. Moreover, system for monitoring and stabilization of environmental conditions is required.

  18. VizieR Online Data Catalog: Water masers in M31. II. Multiwavelength data (Amiri+, 2016)

    NASA Astrophysics Data System (ADS)

    Amiri, N.; Darling, J.

    2016-09-01

    In this paper, we present a comparative multiwavelength analysis of 22GHz water-maser-emitting and non-maser-emitting 24um luminous star-forming regions in M31. We use WISE, Spitzer, and Herschel infrared continuum maps, maps of derived quantities such as star formation and dust temperature, and archival catalogs to examine the differences between maser-emitting and non-maser-emitting regions, to examine correlations between observable quantities among each population, and to constrain the parameter space most likely to produce detectable water masers. Throughout the manuscript, we assume a distance to M31 of 780kpc when calculating luminosities from continuum or line flux measurements. (2 data files).

  19. 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.

  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. 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).

  2. Multi-wavelength multi-level optical storage

    NASA Astrophysics Data System (ADS)

    Wullert, John R., II

    Current digital information storage technologies offer rapid access and seemingly ever-increasing capacities. New storage techniques that improve the data rate of high-density storage technologies are attractive, particularly for cost-sensitive services such as video on demand. Wavelength multiplexing of optical information storage has the potential to increase storage capacity, density and data rate. This dissertation addresses the design, simulation and fabrication of a multi-wavelength, multi-level optical storage structure that has the potential to increase the capacity, density and data rate of optical storage. Multi-wavelength, multi-layer optical storage is a technique for storing data in many separate layers in a medium, where each layer responds to a unique optical wavelength. This approach builds on the strengths of current optical storage technologies and addresses some of their limitations. Multiple layers of storage increase the high storage density possible with optical techniques and the parallelism of wavelength multiplexing improves the relatively low data rate. Multi-wavelength, multi-level optical storage has been investigated theoretically and experimentally. The experimental results provide the first demonstration of optical storage using three wavelengths to read three separate layers of information. These read-only optical memories were based on dielectric mirrors of silicon dioxide, magnesium oxide and aluminum oxide. The layers were designed to be read with semiconductor lasers of 635, 780 and 980 nanometers. The prototype devices exhibited open margins between the on and off states for all eight combinations of the presence and absence of the three mirrors. Theoretical simulations were employed to assess the dynamic operation of multi-wavelength storage devices. Through systematic simulations, variations in the thickness and refractive index of the layers in the structure were identified as the primary noise mechanism and a critical

  3. Multi-wavelength optical storage of diarylethene PMMA film

    NASA Astrophysics Data System (ADS)

    Guo, Haobo; Zhang, Fushi; Wu, Guo-shi; Sun, Fan; Pu, Shouzhi; Mai, Xuesong; Qi, Guosheng

    2003-05-01

    Current commercial optical storage technologies are all based on the heat effect of the recording laser, i.e., heat-mode optical storage. In the present work, photon-mode optical storage using photochromic diarylethene materials was investigated. Two diarylethene derivatives were dispersed into PMMA solution, and spin-coated on a glass substrate with Al reflective layer as the recording layer. Two laser beams of 532 and 650 nm were used in recording and readout simultaneously, and signals with high S/ N ratio were detected. Multi-wavelength optical storage was realized with the diarylethene PMMA film.

  4. 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.

  5. Multiwavelength Variability Study of the Classical BL Lac Object PKS 0735+178 on Timescales Ranging from Decades to Minutes

    NASA Astrophysics Data System (ADS)

    Goyal, Arti; Stawarz, Łukasz; Ostrowski, Michał; Larionov, Valeri; Gopal-Krishna; Wiita, Paul J.; Joshi, Santosh; Soida, Marian; Agudo, Iván

    2017-03-01

    We present the results of our power spectral analysis for the BL Lac object PKS 0735+178, utilizing the Fermi-LAT survey at high-energy γ-rays, several ground-based optical telescopes, and single-dish radio telescopes operating at GHz frequencies. The novelty of our approach is that, by combining long-term and densely sampled intra-night light curves in the optical regime, we were able to construct for the first time the optical power spectrum of the blazar for a time domain extending from 23 years down to minutes. Our analysis reveals that: (1) the optical variability is consistent with a pure red noise, for which the power spectral density can be well approximated by a single power law throughout the entire time domain probed; (2) the slope of power spectral density at high-energy γ-rays (∼1) is significantly flatter than that found at radio and optical frequencies (∼2) within the corresponding time variability range; (3) for the derived power spectra, we did not detect any low-frequency flattening, nor do we see any evidence for cutoffs at the highest frequencies down to the noise floor levels due to measurement uncertainties. We interpret our findings in terms of a model where the blazar variability is generated by the underlying single stochastic process (at radio and optical frequencies), or a linear superposition of such processes (in the γ-ray regime). Along with the detailed PSD analysis, we also present the results of our extended (1998–2015) intra-night optical monitoring program and newly acquired optical photo-polarimetric data for the source.

  6. 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

  7. Search for Blazar Flux-Correlated TeV Neutrinos in IceCube 40-String Data

    NASA Astrophysics Data System (ADS)

    Turley, Colin; Fox, Derek; Murase, Kohta; AMON Core Team Team

    2017-01-01

    We present a targeted search for blazar TeV flux-correlated high-energy neutrinos from six bright northern blazars in the IceCube ``40-string'' sample of TeV neutrinos from 2008-2009. We use VERITAS lightcurves to identify periods of excess and flaring emission and search for an excess of neutrinos during these intervals relative to the atmospheric neutrino background. We make two searches: One for excess neutrinos from Mrk 421, and one for neutrinos associated with the brightest emission periods of five other blazars. We find no significant excess of neutrinos from the blazar directions during the predefined temporal windows, and derive upper limits on the number of blazar-associated neutrinos from each search. These upper limits are sufficiently close to the physically-interesting regime that we anticipate future analyses using already-collected data will either constrain models or yield discovery of the first blazar-associated high-energy neutrinos. NSF grant PHY-1412633

  8. 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.

  9. 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.

  10. Multiwavelength Observations of 3C66A during the WEBT-ENIGMA Campaign of 2003/2004

    NASA Astrophysics Data System (ADS)

    Harvey, J. E.; Boettcher, M.; Joshi, M.; Villata, M.; Mukherjee, R.; Bramel, D.; Cui, W.; Savolainen, T.; Fossati, G.; Smith, I. A.; WEBT

    2004-12-01

    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. 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 hardness - intensity anti-correlation on intraday time scales. The X-ray spectrum is consistent with a power-law with a photon spectral index of ˜ 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 only very moderate internal structure. After decomposition in Gaussian components, evidence for superluminal motion (11.0 ± 4.7 h-1 c) was found in only one out of 6 jet components. The radial radio brightness profile suggests a magnetic field decay ˜ r-1 in the case of a conical jet and, thus, a predominantly perpendicular magnetic field orientation. This work was partially supported by NASA RXTE GO grant no. NNG 04GB13G.

  11. Multiwavelength micromirrors in the cuticle of scarab beetle Chrysina gloriosa.

    PubMed

    Agez, Gonzague; Bayon, Chloé; Mitov, Michel

    2017-01-15

    Beetles from the genus Chrysina show vivid reflections from bright green to metallic silver-gold as a consequence of the cholesteric liquid crystal organization of chitin molecules. Particularly, the cuticle of Chrysina gloriosa exhibits green and silver stripes. By combining confocal microscopy and spectrophotometry, scanning electron microscopy and numerical simulations, the relationship between the reflectance and the structural parameters for both stripes at the micro- and nanoscales are established. Over the visible and near IR spectra, polygonal cells in tessellated green stripes behave as multiwavelength selective micro-mirrors and the silver stripes as specular broadband mirrors. Thermoregulation, conspecifics or intra-species communication, or camouflage against predators are discussed as possible functions. As a prerequisite to bio-inspired artificial replicas, the physical characteristics of the polygonal texture in Chrysina gloriosa cuticle are compared to their equivalents in synthetic cholesteric oligomers and their fundamental differences are ascertained. It is shown that the cuticle has concave cells whereas the artificial films have convex cells, contrary to expectation and assumption in the literature. The present results may provide inspiration for fabricating multiwavelength selective micromirrors or spatial wavelength-specific light modulators.

  12. Multi-wavelength photoplethysmography method for skin arterial pulse extraction

    PubMed Central

    Liu, Jing; Yan, Bryan Ping-Yen; Dai, Wen-Xuan; Ding, Xiao-Rong; Zhang, Yuan-Ting; Zhao, Ni

    2016-01-01

    In this work, we present a multi-wavelength (MW) PPG method exploiting the wavelength dependence of light penetration in skin tissue to provide depth resolution of skin blood pulsation. The MW PPG system requires two to three light sources in different wavelengths and extracts the arterial blood pulsation through a multi-wavelength multi-layer light-skin interaction model, which removes the capillary pulsation (determined from the short-wavelength PPG signal) from the long-wavelength PPG signal using absorption weighting factors that are quasi-analytically calibrated. The extracted pulsations are used to calculate blood pressure (BP) through pulse transit time (PTT), and the results are compared with those obtained from the single wavelength PPG method. The comparative study is clinically performed on 20 subjects including 10 patients diagnosed with cardiovascular diseases and 10 healthy subjects. The result demonstrates that the MW PPG method significantly improves the measurement accuracy of systolic BP (SBP), reducing the mean absolute difference between the reference and the estimated SBP values from 5.7 mmHg (for single-wavelength PPG) to 2.9 mmHg (for three-wavelength PPG). PMID:27867733

  13. Explaining Multi-wavelength Photometric Variability in Young Stellar Objects

    NASA Astrophysics Data System (ADS)

    Kesseli, Aurora; Whitney, B.; Wood, K.; Plavchan, P.; Terebey, S.; Stauffer, J. R.; Morales-Calderon, M.; YSOVAR

    2013-01-01

    We explore a variety of radiation transfer models to explain multi-wavelength photometric variability of young stellar objects in the Orion Nebula Cluster (Morales-Calderon et al. (2011). Our models include hotspots, warps in the accretion disk, and spiral arms. Variability comes in different types, which have been categorized as periodic or quasi-periodic, narrow or broad dips in the light curves, and rapid flux variations or “wild type” stars. Our models can successfully reproduce these. The optical and near-infrared light curves are sensitive to the stellar variations and obscurations from the circumstellar material. The mid-infrared provides an additional diagnostic because it is sensitive to emission from the inner disk and the inner wall height. Our models make specific predictions as to the shapes and phasing of optical through mid-infrared photometry that can be tested with multi-wavelength time-series data. This work is based in part on observations made with the Spitzer Space Telescope, which is operated by the Jet Propulsion Laboratory, California Institute of Technology under a contract with NASA. Support for this work was provided by NASA through an award issued by JPL/Caltech and was partially supported by the National Science Foundation's REU program through NSF Award AST-1004881.

  14. Multi-wavelength fluorometry for anaerobic digestion process monitoring.

    PubMed

    Morel, E; Santamaria, K; Perrier, M; Guiot, S R; Tartakovsky, B

    2005-01-01

    Applicability of multi-wavelength fluorometry for anaerobic digestion process monitoring was investigated in a 3.5 L upflow anaerobic sludge bed (UASB) lab-scale reactor. Both off-line and on-line monitoring of key process parameters was tested. Off-line emission spectra were measured at an angle of 90 degrees to the excitation beam using a cuvette. On-line measurements were carried out using a fiber optic probe in the external recirculation line of the digester. Fluorescence spectra were correlated to available analytical measurements to obtain partial least square regression models. An independent set of measurements was used to validate the regression models. Model estimations showed reasonable agreement with analytical measurements with multiple determination coefficients (R2) between 0.6 and 0.95. Results showed that offline fluorescence measurements can be used for fast estimation of anaerobic digestor effluent quality. At the same time, the on-line implementation of multi-wavelength fluorescence measurements can be used for realtime process monitoring and, potentially, for on-line process control.

  15. 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

  16. Multi-wavelength properties and SMBH's masses of the isolated AGNs in the Local Universe

    NASA Astrophysics Data System (ADS)

    Vavilova, I. B.; Vasylenko, A. A.; Babyk, Iu. V.; Pulatova, N. G.

    2016-08-01

    The sample of 36 nearest isolated AGNs was cross-matched by 2MIG and Veron-Cetty catalogues and limited to Ks ≤ 12.0m and Vr < 15 000 km/s in the northern sky (δ ≥ -15°). These objects were in isolation during ~ 3 Gyrs. For revealing their multi-wavelength properties we used all the available databases obtained with ground-based and space observatories (from radio to X-ray ranges). It is allowed us to separate the internal evolution mechanisms from the environment influence and consider them as two separate processes related to fueling nuclear activity and accretion on the SMBHs outside of the environment. In this report we present briefly main results, which were already published (Pulatova N., Vavilova I., Sawangwit U. et al. The 2MIG isolated AGNs - I. General and multiwavelength properties of AGNs and host galaxies in the northern sky, MNRAS, 447, Issue 3, p. 2209-2223 (2015)). We accentuate that for the first time we revealed that the host isolated galaxies with AGNs of Sy1 type (without faint companions) appear to possess the bar morphological features (e.g., the interaction with neighboring galaxies is not necessary condition for broad-line region formation). We give also current results as concerns with more detail X-ray analysis, emission features and spectral models for several AGNs for which a cumulative soft and hard energy spectrum was reconstructed. The estimates of SMBH masses show that are systematically lower than the SMBH masses of AGNs located in a dense environment.

  17. 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.

  18. AGN-host galaxy connection: multiwavelength study

    NASA Astrophysics Data System (ADS)

    Pović, M.; Sánchez-Portal, M.; García, A. M. Pérez; Bongiovanni, A.; Cepa, J.; Cepa

    2013-02-01

    The connection between active galactic nuclei (AGN) and their hosts showed to be important for understanding the formation and evolution of active galaxies. Using X-ray and deep optical data, we study how morphology and colours are related to X-ray properties at redshifts z<=2.0 for a sample of > 300 X-ray detected AGN in the Subaru/XMM-Newton Deep Survey (SXDS; Furusawa et al. 2008) and Groth-Westphal Strip (GWS; Pović et al. 2009) fields. We performed our morphological classification using the galSVM code (Huertas-Company et al. 2008), which is a new method that is particularly suited when dealing with high-redshift sources. To separate objects between X-ray unobscured and obscured, we used X-ray hardness ratio HR(0.5-2 keV/2-4.5 keV). Colour-magnitude diagrams were studied in relationship to redshift, morphology, X-ray obscuration, and X-ray-to-optical flux ratio. Around 50% of X-ray detected AGN at z<=2.0 analysed in this work reside in spheroidal and bulge-dominated galaxies, while at least 18% have disk-dominated hosts. This suggests that different mechanisms may be responsible for triggering the nuclear activity. When analysing populations of X-ray detected AGN in both colour-magnitude (CMD) and colour-stellar mass diagrams (Figure 1), the highest number of sources is found to reside in the green valley at redshifts ~ 0.5-1.5. For the first time we studied CMD of these AGN in relation to morphology and X-ray obscuration, finding that they can reside in both early- and late-type hosts, where both morphological types cover similar ranges of X-ray obscuration (Figure 1). Our findings appear to confirm some previous suggestions that X-ray selected AGN residing in the green valley represent a transitional population (e.g. Nandra et al. 2007, Silverman et al. 2008, Treister et al. 2009), quenching star formation by means of different AGN feedback mechanisms and evolving to red-sequence galaxies. More details on analysis and results presented here can be found in

  19. Detection of significant cm to sub-mm band radio and γ-ray correlated variability in Fermi bright blazars

    NASA Astrophysics Data System (ADS)

    Fuhrmann, L.; Larsson, S.; Chiang, J.; Angelakis, E.; Zensus, J. A.; Nestoras, I.; Krichbaum, T. P.; Ungerechts, H.; Sievers, A.; Pavlidou, V.; Readhead, A. C. S.; Max-Moerbeck, W.; Pearson, T. J.

    2014-07-01

    The exact location of the γ-ray emitting region in blazars is still controversial. In order to attack this problem we present first results of a cross-correlation analysis between radio (11 cm to 0.8 mm wavelength, F-GAMMA programme) and γ-ray (0.1-300 GeV) ˜3.5 yr light curves of 54 Fermi-bright blazars. We perform a source stacking analysis and estimate significances and chance correlations using mixed source correlations. Our results reveal: (i) the first highly significant multiband radio and γ-ray correlations (radio lagging γ rays) when averaging over the whole sample, (ii) average time delays (source frame: 76 ± 23 to 7 ± 9 d), systematically decreasing from cm to mm/sub-mm bands with a frequency dependence τr, γ(ν) ∝ ν-1, in good agreement with jet opacity dominated by synchrotron self-absorption, (iii) a bulk γ-ray production region typically located within/upstream of the 3 mm core region (τ3mm, γ = 12 ± 8 d), (iv) mean distances between the region of γ-ray peak emission and the radio `τ = 1 photosphere' decreasing from 9.8 ± 3.0 pc (11 cm) to 0.9 ± 1.1 pc (2 mm) and 1.4 ± 0.8 pc (0.8 mm), (v) 3 mm/γ-ray correlations in nine individual sources at a significance level where one is expected by chance (probability: 4 × 10-6), (vi) opacity and `time lag core shift' estimates for quasar 3C 454.3 providing a lower limit for the distance of the bulk γ-ray production region from the supermassive black hole (SMBH) of ˜0.8-1.6 pc, i.e. at the outer edge of the broad-line region (BLR) or beyond. A 3 mm τ = 1 surface at ˜2-3 pc from the jet base (i.e. well outside the `canonical BLR') finally suggests that BLR material extends to several parsec distances from the SMBH.

  20. 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.

  1. Optical spectroscopic classification of a selection of Southern Hemisphere Fermi-LAT unclassified blazars

    NASA Astrophysics Data System (ADS)

    Klindt, L.; van Soelen, B.; Meintjes, P. J.; Väisänen, P.

    2017-01-01

    The Fermi-LAT has detected more than 3000 sources in the GeV γ-ray regime. The majority are extra-galactic and these sources are dominated by blazars. However, ˜28 per cent of the sources in Fermi 3LAC are listed as blazar candidates of uncertain type (BCU). Increasing the number of classified Fermi-LAT sources is important for improving our understanding of extra-galactic γ-ray sources and can be used to search for new very high energy sources. We report on the optical spectroscopy of seven selected unclassified BCU sources during 2014 and 2015 undertaken using the SAAO 1.9-m and Southern African Large Telescope (SALT). Based on the identified spectral lines we have classified three of the sources as FSRQs and the remaining four as BL Lac objects, determining the redshift for four sources.

  2. Tunable multiwavelength SOA fiber laser with ultra-narrow wavelength spacing based on nonlinear polarization rotation.

    PubMed

    Zhang, Zuxing; Wu, Jian; Xu, Kun; Hong, Xiaobin; Lin, Jintong

    2009-09-14

    A tunable multiwavelength fiber laser with ultra-narrow wavelength spacing and large wavelength number using a semiconductor optical amplifier (SOA) has been demonstrated. Intensity-dependent transmission induced by nonlinear polarization rotation in the SOA accounts for stable multiwavelength operation with wavelength spacing less than the homogenous broadening linewidth of the SOA. Stable multiwavelength lasing with wavelength spacing as small as 0.08 nm and wavelength number up to 126 is achieved at room temperature. Moreover, wavelength tuning of 20.2 nm is implemented via polarization tuning.

  3. AGILE detection of renewed gamma-ray activity from the blazar PKS 1502+106

    NASA Astrophysics Data System (ADS)

    Pittori, C.; Bulgarelli, A.; Lucarelli, F.; Verrecchia, F.; Fioretti, V.; Tavani, M.; Vercellone, S.; Piano, G.; Striani, E.; Donnarumma, I.; 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.

    2016-01-01

    The AGILE satellite detects renewed gamma-ray activity from a source positionally consistent with the high-redshift (z=1.8383) blazar PKS 1502+106 (also known as OR 103, S3 1502+10 and 3FGLJ1504.4+1029), with radio coordinates, R.A.: 226.10408 deg, Dec: 10.49422 deg (J2000) (Johnston et al. 1995, AJ, 110, 880).

  4. 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.

  5. 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.

  6. Contemporaneous VLBA 5 GHz Observations of Large Area Telescope Detected Blazars

    DTIC Science & Technology

    2012-01-10

    blazars detected by the Large Area Telescope (LAT) on board the Fermi Gamma - ray Space Telescope have been observed contemporaneously by the Very Long...galaxies: jets – galaxies: nuclei – gamma rays : galaxies – radio continuum: galaxies 1. INTRODUCTION The Large Area Telescope (LAT; Atwood et al. 2009...on board the Fermi Gamma - ray Space Telescope is a wide-field telescope covering the energy range from about 20 MeV to more than 300 GeV. It has been

  7. 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.

  8. 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.

  9. Central engine of a gamma-ray blazar resolved through the magnifying glass of gravitational microlensing

    NASA Astrophysics Data System (ADS)

    Neronov, Andrii; Vovk, Ievgen; Malyshev, Denys

    2015-08-01

    Gamma-ray emission from blazars is known to originate from jets emitted by supermassive black holes. However, the exact location and size of the γ-ray emitting part of the jets is uncertain. The main difficulty is the very small angular size of these sources, beyond the angular resolution of γ-ray telescopes. Here, we report a measurement of the projected size of the γ-ray jet, revealed by the detection of microlensing in the gravitationally lensed blazar PKS 1830-211. This measurement is consistent with a constraint from the intrinsic variability timescale of the blazar. Our measurement shows that the γ-ray emission originates from the vicinity of the central supermassive black hole. Combining the X-ray and γ-ray data, we use the microlensing effect to constrain the size of the X-ray source. We show that the effect of pair production of γ-rays on X-ray photons does not make the source opaque, owing to the large size of the X-ray emission region.

  10. 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.

  11. 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.

  12. The blazar S5 0014+813: a real or apparent monster?

    NASA Astrophysics Data System (ADS)

    Ghisellini, G.; Foschini, L.; Volonteri, M.; Ghirlanda, G.; Haardt, F.; Burlon, D.; Tavecchio, F.

    2009-10-01

    A strong hard X-ray luminosity from a blazar flags the presence of a very powerful jet. If the jet power is in turn related to the mass accretion rate, the most luminous, hard X-ray blazars should pinpoint the largest accretion rates, and thus the largest black hole masses. These ideas are confirmed by the Swift satellite observations of the blazar S5 0014+813, at the redshift z = 3.366. Swift detected this source with all its three instruments, from the optical to the hard X-rays. Through the construction of its spectral energy distribution, we are confident that its optical-ultraviolet (UV) emission is thermal in origin. Associating it with the emission of a standard optically thick geometrically thin accretion disc, we find a black hole mass, M ~ 4 × 1010Msolar, radiating at 40 per cent the Eddington value. The derived mass is among the largest ever found. Super-Eddington slim discs or thick discs with the presence of a collimating funnel can in principle reduce the black hole mass estimate, but tend to produce spectra bluer than observed.

  13. 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).

  14. Multiband optical variability of the blazar OJ 287 during its outbursts in 2015-2016

    NASA Astrophysics Data System (ADS)

    Gupta, Alok C.; Agarwal, Aditi; Mishra, Alka; Gaur, H.; Wiita, P. J.; Gu, M. F.; Kurtanidze, O. M.; Damljanovic, G.; Uemura, M.; Semkov, E.; Strigachev, A.; Bachev, R.; Vince, O.; Zhang, Z.; Villarroel, B.; Kushwaha, P.; Pandey, A.; Abe, T.; Chanishvili, R.; Chigladze, R. A.; Fan, J. H.; Hirochi, J.; Itoh, R.; Kanda, Y.; Kawabata, M.; Kimeridze, G. N.; Kurtanidze, S. O.; Latev, G.; Dimitrova, R. V. Muñoz; Nakaoka, T.; Nikolashvili, M. G.; Shiki, K.; Sigua, L. A.; Spassov, B.

    2017-03-01

    We present recent optical photometric observations of the blazar OJ 287 taken during 2015 September-2016 May. Our intense observations of the blazar started in 2015 November and continued until 2016 May and included detection of the large optical outburst in 2015 December that was predicted using the binary black hole model for OJ 287. For our observing campaign, we used a total of nine ground-based optical telescopes of which one is in Japan, one is in India, three are in Bulgaria, one is in Serbia, one is in Georgia, and two are in the USA. These observations were carried out in 102 nights with a total of ∼1000 image frames in BVRI bands, though the majority were in the R band. We detected a second comparably strong flare in 2016 March. In addition, we investigated multiband flux variations, colour variations, and spectral changes in the blazar on diverse time-scales as they are useful in understanding the emission mechanisms. We briefly discuss the possible physical mechanisms most likely responsible for the observed flux, colour, and spectral variability.

  15. Theory of inversion with two-dimensional regularization: profiles of microphysical particle properties derived from multiwavelength lidar measurements.

    PubMed

    Kolgotin, Alexei; Müller, Detlef

    2008-09-01

    We present the theory of inversion with two-dimensional regularization. We use this novel method to retrieve profiles of microphysical properties of atmospheric particles from profiles of optical properties acquired with multiwavelength Raman lidar. This technique is the first attempt to the best of our knowledge, toward an operational inversion algorithm, which is strongly needed in view of multiwavelength Raman lidar networks. The new algorithm has several advantages over the inversion with so-called classical one-dimensional regularization. Extensive data postprocessing procedures, which are needed to obtain a sensible physical solution space with the classical approach, are reduced. Data analysis, which strongly depends on the experience of the operator, is put on a more objective basis. Thus, we strongly increase unsupervised data analysis. First results from simulation studies show that the new methodology in many cases outperforms our old methodology regarding accuracy of retrieved particle effective radius, and number, surface-area, and volume concentration. The real and the imaginary parts of the complex refractive index can be estimated with at least as equal accuracy as with our old method of inversion with one-dimensional regularization. However, our results on retrieval accuracy still have to be verified in a much larger simulation study.

  16. Multi-wavelength Analysis of a Quiet Solar Region

    NASA Astrophysics Data System (ADS)

    Tsiropoula, G.; Tziotziou, K.; Giannikakis, J.; Young, P.; Schühle, U.; Heinzel, P.

    2007-05-01

    We present observations of a solar quiet region obtained by the ground-based Dutch Open Telescope (DOT), and by instruments on the spacecraft SOHO and TRACE. The observations were obtained during a coordinated observing campaign on October 2005. The aim of this work is to present the rich diversity of fine-scale structures that are found at the network boundaries and their appearance in different instruments and different spectral lines that span the photosphere to the corona. Detailed studies of these structures are crucial to understanding their dynamics in different solar layers, as well as the role such structures play in the mass balance and heating of the solar atmosphere.

  17. Multi-Wavelength Monitoring of GRS 1915+105

    NASA Technical Reports Server (NTRS)

    Bandyopadhyay, R.; Martini, P.; Gerard, E.; Charles, P. A.; Wagner, R. M.; Shrader, C.; Shahbaz, T.; Mirabel, I. F.

    1997-01-01

    Since its discovery in 1992, the superluminal X-ray transient GRS 1915+105 has been extensively observed in an attempt to understand its behaviour. We present here preliminary results from a multi-wavelength campaign undertaken from July to September 1996. This study includes X-ray data from the RXTE All Sky Monitor and BATSE, two-frequency data from the Nancay radio telescope, and infrared photometry from the 1.8m Perkins telescope at Lowell Observatory. The K-band data presented herein provide the first long-term well-sampled IR light curve of GRS 1915+105. We compare the various light curves, searching for correlations in the behaviour of the source at differing wavelengths and for possible periodicities.

  18. Preselecting AGN candidates from multi-wavelength data by ADTree

    NASA Astrophysics Data System (ADS)

    Zhang, Yanxia; Zheng, Hongwen; Zhao, Yongheng

    2005-03-01

    With the information era in astronomy coming, this "data avalanche" may provide many answers to important problems in contemporary astrophysics. The most important problem is sifting through massive amounts of data to mine knowledge. In this paper, we positionally cross-identify multi-wavelength data from optical, near-infrared, and x-ray bands, and then employ alternating decision trees (adtree) to quickly and robustly separate AGN candidates to a high degree of accuracy. We emphasise the application of the method due to the development of large survey projects and the establishment of the virtual observatory, and conclude that the application of data mining algorithms in astronomy is of great importance to discover new knowledge impossible to obtain before, and promote the development of astronomy.

  19. LS 5039 and HD 259440: A Multiwavelength Approach

    NASA Astrophysics Data System (ADS)

    Aragona, Christina

    2012-07-01

    A handful of Galactic High Mass X-ray Binaries have been observed to emit radiation at very high energies (MeV-TeV), dubbed gamma-ray binaries. This poster will review the importance of multiwavelength observations for understanding two of these systems, HD 259440 and LS 5039. For HD 259440, detection of a nearby high-energy source instigated optical observations to search for evidence the system's binarity. For LS 5039, optically determined orbital and stellar parameters combined with constraints on the system inclination angle from X-ray, UV, and radio observations are bringing us closer to identifying the nature of the interaction region and the compact object. I am grateful for support from NSF grant AST-1109247 and Lehigh University.

  20. A multiwavelength study of young stars in the Elephant Trunk

    NASA Astrophysics Data System (ADS)

    López Martí, B.; Bayo, A.; Morales Calderón, M.; Barrado, D.

    2013-05-01

    We present the results of a multiwavelength study of young stars in IC 1396A, ``the Elephant Trunk Nebula''. Our targets are selected combining optical, near-infrared and mid-infrared photometry. Near-infrared and optical spectroscopy are used to confirm their youth and to derive spectral types for these objects, showing that they are early to mid-M stars, and that our sample includes some of the lowest-mass objects reported so far in the region. The photometric and spectroscopic information is used to construct the spectral energy distributions and to study the properties of the stars (mass, age, accretion, disks, spatial location). The implications for the triggered star formation picture are discussed.

  1. Advances from Recent Multi-wavelength Campaigns on Sgr A*

    NASA Astrophysics Data System (ADS)

    Haggard, Daryl

    2017-01-01

    Sagittarius A* is the closest example of a supermassive black hole and our proximity allows us to detect emission from its accretion flow in the radio, submillimeter, near IR, and X-ray regimes. Ambitious monitoring campaigns have yielded rich multi-wavelength, time-resolved data that have the power to probe the physical processes underlying Sgr A*'s quiescent and flare emission. Here, I review the status of Sgr A* X-ray monitoring campaigns from the Chandra X-ray Observatory (also XMM Newton, and Swift), and efforts to coordinate these with observations across the electromagnetic spectrum. I also discuss how these observations constrain models for Sgr A*'s variability, which range from tidal disruption of asteroids to gravitational lensing to collimated outflows to magnetic reconnection.

  2. Multiwavelength Coverage of a Bright Flare from Sgr A

    SciTech Connect

    Trap, G.; Goldwurm, A.

    2009-05-11

    The dynamical center of our galaxy hosts a supermassive black hole, Sgr A*, which has been the target of an extensive multiwavelength campaign for a week in April 2007. We report here the detection of a bright flare from the vicinity of the horizon, observed simultaneously in X-rays (XMM-Newton) and NIR (VLT/NACO) on April 4{sup th}. For the first time, such an event also benefitted from a soft {gamma}-rays (INTEGRAL/ISGRI) and MIR (VLT/VISIR) coverage, which enabled us to derive upper limits at both ends of Sgr A* spectral energy distribution (SED). We discuss the physical implications of the contemporaneous light curves as well as the SED, in terms of synchrotron, synchrotron self-Compton and external Compton emission processes.

  3. Full-spectrum multiwavelength pyrometry for nongray surfaces

    NASA Astrophysics Data System (ADS)

    Ng, Daniel; Williams, W. D.

    1992-04-01

    A full-spectrum (encompassing radiation on both sides of the Wien displacement peak) multiwavelength pyrometer was developed. It measures the surface temperature of arbitrary nongray ceramics by curve fitting a spectrum in this spectral region to a Planck function of temperature T. This function of T is modified by the surface spectral emissivity. The emissivity function was derived experimentally from additional spectra that were obtained by using an auxiliary radiation source and from application of Kirchhoff's law. This emissivity was verified by results that were obtained independently by using electromagnetic and solid-state theories. In the presence of interfering reflected radiation this general pyrometry improves the accuracy of the measured temperature by measuring an additional spectrum that characterizes the interfering radiation source.

  4. Compact multiwavelength transmitter module for multimode fiber optic ribbon cable

    DOEpatents

    Deri, Robert J.; Pocha, Michael D.; Larson, Michael C.; Garrett, Henry E.

    2002-01-01

    A compact multiwavelength transmitter module for multimode fiber optic ribbon cable, which couples light from an M.times.N array of emitters onto N fibers, where the M wavelength may be distributed across two or more vertical-cavity surface-emitting laser (VCSEL) chips, and combining emitters and multiplexer into a compact package that is compatible with placement on a printed circuit board. A key feature is bringing together two emitter arrays fabricated on different substrates--each array designed for a different wavelength--into close physical proximity. Another key feature is to compactly and efficiently combine the light from two or more clusters of optical emitters, each in a different wavelength band, into a fiber ribbon.

  5. Multiwavelength Signatures of Cosmic Ray Acceleration by Young Supernova Remnants

    SciTech Connect

    Vink, Jacco

    2008-12-24

    An overview is given of multiwavelength observations of young supernova remnants, with a focus on the observational signatures of efficient cosmic ray acceleration. Some of the effects that may be attributed to efficient cosmic ray acceleration are the radial magnetic fields in young supernova remnants, magnetic field amplification as determined with X-ray imaging spectroscopy, evidence for large post-shock compression factors, and low plasma temperatures, as measured with high resolution optical/UV/X-ray spectroscopy. Special emphasis is given to spectroscopy of post-shock plasma's, which offers an opportunity to directly measure the post-shock temperature. In the presence of efficient cosmic ray acceleration the post-shock temperatures are expected to be lower than according to standard equations for a strong shock. For a number of supernova remnants this seems indeed to be the case.

  6. Multi-Wavelength Monitoring of GRS 1915+105

    NASA Technical Reports Server (NTRS)

    Bandyopadhyay, R.; Martini, P.; Gerard, E.; Charles, P. A.; Wagner, R. M.; Shrader, C.; Shahbaz, T.; Mirabel, I. F.

    1997-01-01

    Since its discovery in 1992, the superluminal X-ray transient GRS 1915+105 has been extensively observed in an attempt to understand its behaviour. We present here first results from a multi-wavelength campaign undertaken from July to September 1996. This study includes X-ray data from the RXTE All Sky Monitor and BATSE, two-frequency data from the Nancay radio telescope, and infrared photometry from the 1.8 m Perkins telescope at Lowell Observatory. The first long-term well-sampled IR light curve of GRS 1915+105 is presented herein and is consistent with the interpretation of this source as a long-period binary. We compare the various light curves, searching for correlations in the behaviour of the source at differing wavelengths and for possible periodicities.

  7. Multiwavelength anomalous diffraction at high x-ray intensity.

    PubMed

    Son, Sang-Kil; Chapman, Henry N; Santra, Robin

    2011-11-18

    The multiwavelength anomalous diffraction (MAD) method is used to determine phase information in x-ray crystallography by employing anomalous scattering from heavy atoms. X-ray free-electron lasers (FELs) show promise for revealing the structure of single molecules or nanocrystals, but the phase problem remains largely unsolved. Because of the ultrabrightness of x-ray FEL, samples experience severe electronic radiation damage, especially to heavy atoms, which hinders direct implementation of MAD with x-ray FELs. Here, we propose a generalized version of MAD phasing at high x-ray intensity. We demonstrate the existence of a Karle-Hendrickson-type equation in the high-intensity regime and calculate relevant coefficients with detailed electronic damage dynamics of heavy atoms. The present method offers a potential for ab initio structural determination in femtosecond x-ray nanocrystallography.

  8. Multi-wavelength probes of distant lensed galaxies

    NASA Astrophysics Data System (ADS)

    Serjeant, Stephen

    2012-08-01

    I summarise recent results on multi-wavelength properties of distant lensed galaxies, with a particular focus on Herschel. Submm surveys have already resulted in a breakthrough discovery of an extremely efficient selection technique for strong gravitational lenses. Benefitting from the gravitational magnification boost, blind mm-wave redshifts have been demonstrated on IRAM, SMA and GBT, and follow-up emission line detections have been made of water, [Oiii], [Cii] and other species, revealing the PDR/XDR/CRDR conditions. I also discuss HST imaging of submm lenses, lensed galaxy reconstruction, the prospects for ALMA and e-Merlin and the effects of differential magnification. Many emission line diagnostics are relatively unaffected by differential magnification, but SED-based estimates of bolometric fractions in lensed infrared galaxies are so unreliable as to be useless, unless a lens mass model is available to correct for differential amplification.

  9. Multi-wavelength study of MGRO J2019+37

    NASA Astrophysics Data System (ADS)

    Hou, Chao; Chen, Song-Zhan; Yuan, Qiang; Cao, Zhen; He, Hui-Hai; Sheng, Xiang-Dong

    2014-08-01

    MGRO J2019+37, within the Cygnus region, is a bright extended source revealed by Milagro at 12-35 TeV. This source is almost as bright as the Crab Nebula in the northern sky, but is not confirmed by ARGO-YBJ around the TeV scale. Up to now, no obvious counterpart at low energy wavelengths has been found. Hence, MGRO J2019+37 is a rather mysterious object and its VHE γ-ray emission mechanism is worth investigating. In this paper, a brief summary of the multi-wavelength observations from radio to γ-rays is presented. All the available data from XMM-Newton and INTEGRAL at X-ray, and Fermi-LAT at γ-ray bands, are used to get constraints on its emission flux at low energy wavelengths. Then, its possible counterparts and the VHE emission mechanism are discussed.

  10. A multiwavelength investigation of the supernova remnant IC 443

    NASA Technical Reports Server (NTRS)

    Mufson, S. L.; Mccollough, M. L.; Dickel, J. R.; Petre, R.; White, R.

    1986-01-01

    Multiwavelength observations of the supernova remnant IC 443 at radio, infrared, optical, ultraviolet, and X-ray wavelengths are presented. This morphological study of IC 443 presents a detailed picture of an adolescent supernova remnant in a multiphase interstellar medium. Radio observations show that better than 80 percent of the continuum emission at 18 cm is in a large-scale (greater than 18 arcmin) component. Decomposition of the infrared data shows that radiatively heated dust, shocked blackbody dust emission, and infrared line emission are all important components of the observed IRAS fluxes. The morphology of the IC 443 region is consistent with a supernova blast in an interstellar medium with a nonuniform distribution of clouds. The bright northeast rim and the great extent of the remnant to the southwest are most easily explained by a cloud filling factor which is greatest in the northeast and falls off toward the southwest.

  11. Characterisation of a phantom for multiwavelength quantitative photoacoustic imaging.

    PubMed

    Fonseca, M; Zeqiri, B; Beard, P C; Cox, B T

    2016-07-07

    Quantitative photoacoustic imaging (qPAI) has the potential to provide high- resolution in vivo images of chromophore concentration, which may be indicative of tissue function and pathology. Many strategies have been proposed recently for extracting quantitative information, but many have not been experimentally verified. Experimental phantom-based validation studies can be used to test the robustness and accuracy of such algorithms in order to ensure reliable in vivo application is possible. The phantoms used in such studies must have well-characterised optical and acoustic properties similar to tissue, and be versatile and stable. Polyvinyl chloride plastisol (PVCP) has been suggested as a phantom for quality control and system evaluation. By characterising its multiwavelength optical properties, broadband acoustic properties and thermoelastic behaviour, this paper examines its potential as a phantom for qPAI studies too. PVCP's acoustic properties were assessed for various formulations, as well as its intrinsic optical absorption, and scattering with added TiO2, over a range of wavelengths from 400-2000 nm. To change the absorption coefficient, pigment-based chromophores that are stable during the phantom fabrication process, were used. These yielded unique spectra analogous to tissue chromophores and linear with concentration. At the high peak powers typically used in photoacoustic imaging, nonlinear optical absorption was observed. The Grüneisen parameter was measured to be [Formula: see text]  =  1.01  ±  0.05, larger than typically found in tissue, though useful for increased PA signal. Single and multiwavelength 3D PA imaging of various fabricated PVCP phantoms were demonstrated.

  12. Characterisation of a phantom for multiwavelength quantitative photoacoustic imaging

    NASA Astrophysics Data System (ADS)

    Fonseca, M.; Zeqiri, B.; Beard, P. C.; Cox, B. T.

    2016-07-01

    Quantitative photoacoustic imaging (qPAI) has the potential to provide high- resolution in vivo images of chromophore concentration, which may be indicative of tissue function and pathology. Many strategies have been proposed recently for extracting quantitative information, but many have not been experimentally verified. Experimental phantom-based validation studies can be used to test the robustness and accuracy of such algorithms in order to ensure reliable in vivo application is possible. The phantoms used in such studies must have well-characterised optical and acoustic properties similar to tissue, and be versatile and stable. Polyvinyl chloride plastisol (PVCP) has been suggested as a phantom for quality control and system evaluation. By characterising its multiwavelength optical properties, broadband acoustic properties and thermoelastic behaviour, this paper examines its potential as a phantom for qPAI studies too. PVCP’s acoustic properties were assessed for various formulations, as well as its intrinsic optical absorption, and scattering with added TiO2, over a range of wavelengths from 400-2000 nm. To change the absorption coefficient, pigment-based chromophores that are stable during the phantom fabrication process, were used. These yielded unique spectra analogous to tissue chromophores and linear with concentration. At the high peak powers typically used in photoacoustic imaging, nonlinear optical absorption was observed. The Grüneisen parameter was measured to be Γ   =  1.01  ±  0.05, larger than typically found in tissue, though useful for increased PA signal. Single and multiwavelength 3D PA imaging of various fabricated PVCP phantoms were demonstrated.

  13. A Multiwavelength Study of IC 63 and IC 59

    NASA Astrophysics Data System (ADS)

    Karr, J. L.; Noriega-Crespo, A.; Martin, P. G.

    2005-02-01

    IC 63 and IC 59 are two nearby arc-shaped nebulae with relatively simple geometries and minimal obscuring material. The two regions, in spite of a similar projected distance from their ionizing star, have very different observational properties, both in continuum emission and in the presence and strength of line emission from molecular species. This paper conducts a multiwavelength study of the two regions using archived data from a variety of sources, including the Canadian Galactic Plane Survey and the Infrared Space Observatory. The multiwavelength morphology and structure of the two nebulae are studied in detail, particularly the ionization fronts in IC 63. The possibility of triggered star formation in IC 63 is investigated and determined to be spurious. H2 and polycyclic aromatic hydrocarbon emission is detected in both IC 63 and IC 59, confirming the presence of molecular hydrogen in IC 59. The averaged line ratios are similar in the two regions, but variations are seen within each region. Temperatures and densities were calculated from the S(3) and S(5) pure rotational lines of molecular hydrogen. We derived a temperature of 630 K in IC 63, comparable to previous results, and a column density of 5.8×1017 cm-2, somewhat lower than previous values. New results for IC 59 show values of 590 K and 3.4×1017 cm-2, slightly cooler and with lower column density than IC 63. The contrast in appearance between IC 63 and IC 59 is consistent with a difference in actual (rather than projected) distances and a small variation in temperature and column density.

  14. Science Drivers for Multiwavelength Investigations Using the New Gamma-Ray Observatories and Missions

    NASA Technical Reports Server (NTRS)

    Thompson, Dave

    2007-01-01

    This viewgraph presentation discusses the need for multiwavelength research in terms of types of observation facilities, advances in communication, astrophysics vs. astronomy, and maximizing the scientific return from new gamma-ray facilities.

  15. Multiwavelength fiber lasers based on spatial mode beating for high resolution linear and angular displacement sensing

    NASA Astrophysics Data System (ADS)

    Chen, Nan-Kuang; Chang, Yung-Hsiang; Cheng, Wood-Hi; Guo, Tuan; Guan, Bai-Ou

    2014-05-01

    We demonstrate multiwavelength fiber lasers by incorporating the micro Michelson interferometer with spatial mode beating phenomenon, which comes from the interferences among cladding modes, into ring cavity for high resolution linear and angular displacement sensing.

  16. Multiwavelength Opportunities and Challenges in the Era of Fermi Gamma-ray Space Telescope Public Data

    NASA Astrophysics Data System (ADS)

    Thompson, David John; Fermi Large Area Telescope Collaboration

    2010-01-01

    The gamma-ray survey of the sky by the Fermi Gamma-ray Space Telescope offers 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. Identification of newly-discovered gamma-ray sources is largely a multiwavelength effort. 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 can be difficult both in terms of logistics and in terms of generating scientific interest. The Fermi LAT team continues to welcome cooperative efforts aimed at maximizing the scientific return from the mission through multiwavelength studies.

  17. Multiwavelength Photosensor for On-Chip Real-Time Monitoring of Fluorescence and Turbidity

    NASA Astrophysics Data System (ADS)

    Maruyama, Yuki; Ishida, Makoto; Sawada, Kazuaki

    2009-06-01

    In this paper, we report simultaneous detection of fluorescence and turbidity using a multiwavelength photosensor. The multiwavelength photosensor is fabricated in a 5 µm 1-poly 1-metal p-well complementary metal oxide semiconductor (CMOS) technology. First, to confirm the basic characteristics of the multiwavelength photosensor, the linearity of irradiated intensity and photocurrent, fluorescence detection capability, and turbidity detection capability were separately observed. Then, in the fluorescence detection measurement using a fluorescent dye, a detection limit of DNA concentration of 49.8 nM was determined. Then, the turbidity detection performance was compared with that of a Si photodiode. Finally, the sensor was used for real-time monitoring of DNA amplification using the loop-mediated isothermal amplification (LAMP) method. Owing to its multiwavelength detection, simultaneous changes in fluorescence and turbidity were successfully observed using a single sensor.

  18. V404 Cygni: coordination of multi-wavelength observations and request for coverage during HST visits

    NASA Astrophysics Data System (ADS)

    Knigge, C.; Marsh, T. R.; Sivakoff, G. R.; Altamirano, D.; Hernández Santisteban, J. V.; Shaw, A.; Charles, P. A.; Gandhi, P.

    2015-06-01

    In an effort to coordinate the multi-wavelength observations covering the ongoing outburst of the black hole X-ray transient V404 Cygni, we have set up a mailing list to facilitate communication between observers.

  19. Optical Spectroscopic Observations of Gamma-Ray Blazar Candidates. VI. Further Observations from TNG, WHT, OAN, SOAR, and Magellan Telescopes

    NASA Astrophysics Data System (ADS)

    Álvarez Crespo, N.; Massaro, F.; Milisavljevic, D.; Landoni, M.; Chavushyan, V.; Patiño-Álvarez, V.; Masetti, N.; Jiménez-Bailón, E.; Strader, J.; Chomiuk, L.; Katagiri, H.; Kagaya, M.; Cheung, C. C.; Paggi, A.; D'Abrusco, R.; Ricci, F.; La Franca, F.; Smith, Howard A.; Tosti, G.

    2016-04-01

    Blazars, one of the most extreme classes of active galaxies, constitute so far the largest known population of γ-ray sources, and their number is continuously growing in the Fermi catalogs. However, in the latest release of the Fermi catalog there is still a large fraction of sources that are classified as blazar candidates of uncertain type (BCUs) for which optical spectroscopic observations are necessary to confirm their nature and their associations. In addition, about one-third of the γ-ray point sources listed in the Third Fermi-LAT Source Catalog (3FGL) are still unassociated and lacking an assigned lower-energy counterpart. Since 2012 we have been carrying out an optical spectroscopic campaign to observe blazar candidates to confirm their nature. In this paper, the sixth of the series, we present optical spectroscopic observations for 30 γ-ray blazar candidates from different observing programs we carried out with the Telescopio Nazionale Galileo, William Herschel Telescope, Observatorio Astronómico Nacional, Southern Astrophysical Research Telescope, and Magellan Telescopes. We found that 21 out of 30 sources investigated are BL Lac objects, while the remaining targets are classified as flat-spectrum radio quasars showing the typical broad emission lines of normal quasi-stellar objects. We conclude that our selection of γ-ray blazar candidates based on their multifrequency properties continues to be a successful way to discover potential low-energy counterparts of the Fermi unidentified gamma-ray sources and to confirm the nature of BCUs.

  20. Optical archival spectra of blazar candidates of uncertain type in the 3rd Fermi Large Area Telescope Catalog

    NASA Astrophysics Data System (ADS)

    Álvarez Crespo, N.; Massaro, F.; D'Abrusco, R.; Landoni, M.; Masetti, N.; Chavushyan, V.; Jiménez-Bailón, E.; La Franca, F.; Milisavljevic, D.; Paggi, A.; Patiño-Álvarez, V.; Ricci, F.; Smith, Howard A.

    2016-09-01

    Despite the fact that blazars constitute the rarest class among active galactic nuclei (AGNs) they are the largest known population of associated γ-ray sources. Many of the γ-ray objects listed in the Fermi-Large Area Telescope Third Source catalog (3FGL) are classified as blazar candidates of uncertain type (BCUs), either because they show multifrequency behavior similar to blazars but lacking optical spectra in the literature, or because the quality of such spectra is too low to confirm their nature. Here we select, out of 585 BCUs in the 3FGL, 42 BCUs which we identify as probable blazars by their WISE infrared colors and which also have optical spectra that are available in the Sloan Digital Sky Survey (SDSS) and/or Six-Degree Field Galaxy Survey Database (6dFGS). We confirm the blazar nature of all of the sources. We furthermore conclude that 28 of them are BL Lacs, 8 are radio-loud quasars with flat radio spectrum and 6 are BL Lac whose emission is dominated by their host galaxy.

  1. A figure of merit for blazar-like source identification in the gamma-ray energy band

    SciTech Connect

    Cavazzuti, Elisabetta; Pittori, Carlotta; Giommi, Paolo; Colafrancesco, Sergio

    2007-07-12

    The microwave to gamma-ray slope {alpha}{mu}{gamma} can be used as a viable figure of merit for blazar-like source identification in gamma-rays. Taking into account the constraints from the observed extragalactic gamma-ray background, one can estimate the maximum duty cycle allowed for a selected sample of low energy peaked (LBL) blazars, in order to be detectable for the nominal sensitivity values of AGILE and GLAST gamma-ray experiments. This work is based on the results of a recently derived blazar radio LogN-LogS obtained by combining several multi-frequency surveys. We present our estimates of duty cycle constraints applied on a sample composed by 146 high latitude and 74 medium latitude LBL blazars from the new WMAP3 yr catalog. Our results can be used as an indicator to identify good gamma-ray blazar candidates: sources with high values of duty cycle can in principle be detectable also in a ''steady'' state by AGILE and GLAST without over-predicting the extragalactic background.

  2. FERMI LARGE AREA TELESCOPE DETECTION OF GRAVITATIONAL LENS DELAYED γ-RAY FLARES FROM BLAZAR B0218+357

    SciTech Connect

    Cheung, C. C.; Grove, J. E.; Larsson, S.; Scargle, J. D.; Amin, M. A.; Blandford, R. D.; Chiang, J.; Marshall, P. J.; Bulmash, D.; Ciprini, S.; Corbet, R. H. D.; Falco, E. E.; Wood, D. L.; Ajello, M.; Bastieri, D.; Chekhtman, A.; D'Ammando, F.; Giroletti, M.; Lott, B.; and others

    2014-02-20

    Using data from the Fermi Large Area Telescope (LAT), we report the first clear γ-ray measurement of a delay between flares from the gravitationally lensed images of a blazar. The delay was detected in B0218+357, a known double-image lensed system, during a period of enhanced γ-ray activity with peak fluxes consistently observed to reach >20-50 × its previous average flux. An auto-correlation function analysis identified a delay in the γ-ray data of 11.46 ± 0.16 days (1σ) that is ∼1 day greater than previous radio measurements. Considering that it is beyond the capabilities of the LAT to spatially resolve the two images, we nevertheless decomposed individual sequences of superposing γ-ray flares/delayed emissions. In three such ∼8-10 day-long sequences within a ∼4 month span, considering confusion due to overlapping flaring emission and flux measurement uncertainties, we found flux ratios consistent with ∼1, thus systematically smaller than those from radio observations. During the first, best-defined flare, the delayed emission was detailed with a Fermi pointing, and we observed flux doubling timescales of ∼3-6 hr implying as well extremely compact γ-ray emitting regions.

  3. Fermi-LAT Detection of Gravitational Lens Delayed Gamma-Ray Flares from Blazar B0218+357

    NASA Technical Reports Server (NTRS)

    Cheung, C. C.; Larsson, S.; Scargle, J. D.; Amin, M. A.; Blandford, R. D.; Bulmash, D.; Chiang, J.; Ciprini, S.; Corbet, R. D. H.; Falco, E. E.; Marshall, P. J.; Wood, D. L.; Ajello, M.; Bastieri, D.; Chekhtman, A.; D'Ammando, F.; Giroletti, M.; Grove, J. E.; Lott, B.; Ohja, R.; Orienti, M.; Perkins, J. S.; Razzano, M.; Smith, A. W.; Thompson, D. J.; Wood, K. S.

    2014-01-01

    Using data from the Fermi Large Area Telescope (LAT), we report the first clear gamma-ray measurement of a delay between flares from the gravitationally lensed images of a blazar. The delay was detected in B0218+357, a known double-image lensed system, during a period of enhanced gamma-ray activity with peak fluxes consistently observed to reach greater than 20-50 times its previous average flux. An auto-correlation function analysis identified a delay in the gamma-ray data of 11.46 plus or minus 0.16 days (1 sigma) that is approximately 1 day greater than previous radio measurements. Considering that it is beyond the capabilities of the LAT to spatially resolve the two images, we nevertheless decomposed individual sequences of superposing gamma-ray flares/delayed emissions. In three such approximately 8-10 day-long sequences within an approximately 4-month span, considering confusion due to overlapping flaring emission and flux measurement uncertainties, we found flux ratios consistent with approximately 1, thus systematically smaller than those from radio observations. During the first, best-defined flare, the delayed emission was detailed with a Fermi pointing, and we observed flux doubling timescales of approximately 3-6 hours implying as well extremely compact gamma-ray emitting regions.

  4. Very Rapid High-amplitude Gamma-Ray Variability in Luminous Blazar PKS 1510-089 Studied with Fermi-LAT

    SciTech Connect

    Saito, S.; Stawarz, L.; Tanaka, Y.T.; Takahashi, T.; Madejski, G.; D'Ammando, F.

    2013-03-20

    Here we report on the detailed analysis of the γ-ray light curve of a luminous blazar PKS 1510-089 observed in the GeV range with the Large Area Telescope (LAT) onboard 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 three-hours. In the latter case we estimate the corresponding γ-ray flux doubling timescale to be below one hour, which is extreme and never previously reported for any active galaxy

  5. The New Surprising Behaviour of the Two 'Prototype' Blazars PKS 2155-304 and 3C 279

    SciTech Connect

    Costamante, Luigi; Aharonian, Felix; Buhler, Rolf; Khangulyan, Dmitry; Reimer, Anita; Reimer, Olaf; /Stanford U., HEPL /KIPAC, Menlo Park

    2011-11-21

    Recent VHE observations have unveiled a surprising behaviour in two well-known blazars at opposite sides of the blazar sequence. PKS 2155-304 have shown for the first time in an HBL a large Compton dominance, high {gamma}-ray luminosities and a cubic relation between X-ray and VHE fluxes. 3C 279 is the first FSRQ detected at VHE. The high luminosity required to overcome the significant absorption caused by the BLR emission cannot be easily reconciled with the historical and quasi-simultaneous SED properties. Both cases shed a new light on the structure and ambient fields of blazars. Contrary to previous claims, it is also shown that 3C 279 - as any FSRQ - cannot provide robust constraints on the EBL.

  6. The ASTRODEEP Frontier Fields catalogues. I. Multiwavelength photometry of Abell-2744 and MACS-J0416

    NASA Astrophysics Data System (ADS)

    Merlin, E.; Amorín, R.; Castellano, M.; Fontana, A.; Buitrago, F.; Dunlop, J. S.; Elbaz, D.; Boucaud, A.; Bourne, N.; Boutsia, K.; Brammer, G.; Bruce, V. A.; Capak, P.; Cappelluti, N.; Ciesla, L.; Comastri, A.; Cullen, F.; Derriere, S.; Faber, S. M.; Ferguson, H. C.; Giallongo, E.; Grazian, A.; Lotz, J.; Michałowski, M. J.; Paris, D.; Pentericci, L.; Pilo, S.; Santini, P.; Schreiber, C.; Shu, X.; Wang, T.

    2016-05-01

    Context. The Frontier Fields survey is a pioneering observational program aimed at collecting photometric data, both from space (Hubble Space Telescope and Spitzer Space Telescope) and from ground-based facilities (VLT Hawk-I), for six deep fields pointing at clusters of galaxies and six nearby deep parallel fields, in a wide range of passbands. The analysis of these data is a natural outcome of the Astrodeep project, an EU collaboration aimed at developing methods and tools for extragalactic photometry and creating valuable public photometric catalogues. Aims: We produce multiwavelength photometric catalogues (from B to 4.5 μm) for the first two of the Frontier Fields, Abell-2744 and MACS-J0416 (plus their parallel fields). Methods: To detect faint sources even in the central regions of the clusters, we develop a robust and repeatable procedure that uses the public codes Galapagos and Galfit to model and remove most of the light contribution from both the brightest cluster members, and the intra-cluster light. We perform the detection on the processed HST H160 image to obtain a pure H-selected sample, which is the primary catalogue that we publish. We also add a sample of sources which are undetected in the H160 image but appear on a stacked infrared image. Photometry on the other HST bands is obtained using SExtractor, again on processed images after the procedure for foreground light removal. Photometry on the Hawk-I and IRAC bands is obtained using our PSF-matching deconfusion code t-phot. A similar procedure, but without the need for the foreground light removal, is adopted for the Parallel fields. Results: The procedure of foreground light subtraction allows for the detection and the photometric measurements of ~2500 sources per field. We deliver and release complete photometric H-detected catalogues, with the addition of the complementary sample of infrared-detected sources. All objects have multiwavelength coverage including B to H HST bands, plus K

  7. Detection of very high energy gamma-ray emission from the gravitationally lensed blazar QSO B0218+357 with the MAGIC telescopes

    NASA Astrophysics Data System (ADS)

    Ahnen, M. L.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Arcaro, C.; Babic, A.; Banerjee, B.; Bangale, P.; Barres de Almeida, U.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Berti, A.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Buson, S.; 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.; Di Pierro, F.; Doert, M.; Domínguez, A.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher Glawion, D.; Elsaesser, D.; Engelkemeier, M.; Fallah Ramazani, V.; 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.; Gora, D.; Guberman, D.; Hadasch, D.; Hahn, A.; 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.; Longo, F.; López, M.; López-Coto, R.; 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.; Nogués, L.; Paiano, S.; Palacio, J.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Pedaletti, G.; Peresano, M.; Perri, L.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Garcia, J. R.; Reichardt, I.; Rhode, W.; Ribó, M.; Rico, J.; Saito, T.; Satalecka, K.; Schroeder, S.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Strzys, M.; Surić, T.; Takalo, L.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Torres, D. F.; Toyama, T.; Treves, A.; Vanzo, G.; Verguilov, V.; Vovk, I.; Ward, J. E.; Will, M.; Wu, M. H.; Zanin, R.; Desiante, R.

    2016-11-01

    Context. QSO B0218+357 is a gravitationally lensed blazar located at a redshift of 0.944. The gravitational lensing splits the emitted radiation into two components that are spatially indistinguishable by gamma-ray instruments, but separated by a 10-12 day delay. In July 2014, QSO B0218+357 experienced a violent flare observed by the Fermi-LAT and followed by the MAGIC telescopes. Aims: The spectral energy distribution of QSO B0218+357 can give information on the energetics of z 1 very high energy gamma-ray sources. Moreover the gamma-ray emission can also be used as a probe of the extragalactic background light at z 1. Methods: MAGIC performed observations of QSO B0218+357 during the expected arrival time of the delayed component of the emission. The MAGIC and Fermi-LAT observations were accompanied by quasi-simultaneous optical data from the KVA telescope and X-ray observations by Swift-XRT. We construct a multiwavelength spectral energy distribution of QSO B0218+357 and use it to model the source. The GeV and sub-TeV data obtained by Fermi-LAT and MAGIC are used to set constraints on the extragalactic background light. Results: Very high energy gamma-ray emission was detected from the direction of QSO B0218+357 by the MAGIC telescopes during the expected time of arrival of the trailing component of the flare, making it the farthest very high energy gamma-ray source detected to date. The observed emission spans the energy range from 65 to 175 GeV. The combined MAGIC and Fermi-LAT spectral energy distribution of QSO B0218+357 is consistent with current extragalactic background light models. The broadband emission can be modeled in the framework of a two-zone external Compton scenario, where the GeV emission comes from an emission region in the jet, located outside the broad line region.

  8. Search for Blazar Flux-correlated TeV Neutrinos in IceCube 40-string Data

    NASA Astrophysics Data System (ADS)

    Turley, C. F.; Fox, D. B.; Murase, K.; Falcone, A.; Barnaba, M.; Coutu, S.; Cowen, D. F.; Filippatos, G.; Hanna, C.; Keivani, A.; Messick, C.; Mészáros, P.; Mostafá, M.; Oikonomou, F.; Shoemaker, I.; Toomey, M.; Tešić, G.; Astrophysical Multimessenger Observatory Network, For The

    2016-12-01

    We present a targeted search for blazar flux-correlated high-energy ({\\varepsilon }ν ≳ 1 TeV) neutrinos from six bright northern blazars, using the public database of northern hemisphere neutrinos detected during “IC40” 40-string operations of the IceCube neutrino observatory (2008 April to 2009 May). Our six targeted blazars are subjects of long-term monitoring campaigns by the VERITAS TeV γ-ray observatory. We use the publicly available VERITAS light curves to identify periods of excess and flaring emission. These predefined intervals serve as our “active temporal windows” in a search for an excess of neutrinos, relative to Poisson fluctuations of the near-isotropic atmospheric neutrino background, which dominates at these energies. After defining the parameters of an optimized search, we confirm the expected Poisson behavior with Monte Carlo simulations prior to testing for excess neutrinos in the actual data. We make two searches: one for excess neutrinos associated with the bright flares of Mrk 421 that occurred during the IC40 run, and one for excess neutrinos associated with the brightest emission periods of five other blazars (Mrk 501, 1ES 0806+524, 1ES 1218+304, 3C 66A, and W Comae), all significantly fainter than the Mrk 421 flares. We find no significant excess of neutrinos from the preselected blazar directions during the selected temporal windows. We derive 90% confidence upper limits on the number of expected flux-associated neutrinos from each search. These limits are consistent with previous point-source searches and Fermi GeV flux-correlated searches. Our upper limits are sufficiently close to the physically interesting regime that we anticipate that future analyses using already-collected data will either constrain models or yield discovery of the first blazar-associated high-energy neutrinos.

  9. Understanding Grb Physics With Multi-Wavelength Data

    NASA Astrophysics Data System (ADS)

    Zhang, Bing

    The study of Gamma-ray bursts (GRBs) has entered a full multi-wavelength era. A rich trove of data from NASA GRB missions and ground-based follow up observations have been collected. Careful data mining with well-defined scientific objectives holds the key to address open questions in GRB physics, such as jet composition, radiation mechanism, progenitor and central engine physics. We propose to perform data analyses in the following three directions. 1. The time resolved GRB spectra have a dominant component that can be fit with a phenomenological ``Band'' function. The physical meaning of this function remains unclear. Recently we made a breakthrough in theoretical modeling, and showed that fast-cooling synchrotron radiation of electrons in a decreasing magnetic field can mimic the Band function in detector's bandpass, but differs from Band function slightly. We propose to apply this physically-motivated model to systematically fit the GRB prompt emission data collected by Fermi GBM and LAT, and test whether the dominant GRB emission mechanism is fast cooling synchrotron radiation. We will also fit time-dependent spectra with a time-dependent model to investigate whether a quasi- thermal "photosphere'' emission component is indeed needed to fit the observed spectra. This would shed light onto the unknown composition of GRB jets. By fitting the time resolved spectra, we will also constrain important physical parameters of GRB prompt emission, such as the emission site of GRBs, the strength of magnetic fields, as well as their evolution with radius. 2. Recent GRB multi-wavelength observations suggest that it is not straightforward to define the physical category of a GRB based on the traditional classification in the "duration''-"hardness'' domain. Some long-duration GRBs may not have a massive star origin, while some short-duration GRBs may instead have a massive star origin. We propose to systematically study the gamma-ray Swift/BAT, Fermi/GBM- LAT), X-ray (Swift

  10. Multi-Wavelength Time Variability of Active Galactic Nuclei

    NASA Astrophysics Data System (ADS)

    Chatterjee, Ritaban

    2009-01-01

    Due to their large distances, AGNs are not spatially resolved with current and near-future technologies except by radio interferometry. However, we can use time variability, one of the defining properties of AGNs, to probe the location and physical processes related to the emission at resolutions even finer than provided by VLBI. I use extensive multi-frequency monitoring data of the blazars 3C 279 and PKS 1510-089 (over 10 years long) and the radio galaxy 3C 120 ( 5 years), including well-sampled light curves (radiative flux vs. time) at X-ray energies (2-10 keV), optical wavelengths (R band), and radio frequencies (14.5 GHz and 37 GHz), as well as monthly images obtained with the Very Long Baseline Array (VLBA) at 43 GHz that follow changes in the emission structure of the jet on parsec scales. I have developed and applied a set of statistical tools to characterize the time variability of AGNs. This includes the power spectral density (PSD) and its uncertainties, discrete cross-correlation functions and their significance using random light curves simulated from the previously calculated PSDs, and decomposition of light curves into individual flares. I also model the time variable emission spectrum of an AGN jet using a numerical code that includes conical geometry, turbulent magnetic field and density, and energization of electrons due to a moving shock front. Comparing the results of the model calculations and the application of the above-mentioned statistical procedures on the real data, I draw conclusions about the location of the emission regions of these objects. I also identify the ongoing emission mechanisms and implications regarding the physics of jets. This work is supported by NASA through grants NNX08AJ64G (ADP) and NNX08AV65G (Fermi).

  11. MULTIWAVELENGTH OBSERVATIONS OF THE HOT DB STAR PG 0112+104

    SciTech Connect

    Dufour, P.; Desharnais, S.; Wesemael, F.; Bergeron, P.; Fontaine, G.; Beauchamp, A.; Limoges, M.-M. E-mail: stephanie@astro.umontreal.c E-mail: bergeron@astro.umontreal.c

    2010-08-01

    We present a comprehensive multiwavelength analysis of the hot DB white dwarf PG 0112+104. Our analysis relies on newly acquired FUSE observations, on medium-resolution FOS and GHRS data, on archival high-resolution GHRS observations, on optical spectrophotometry both in the blue and around H{alpha}, as well as on time-resolved photometry. From the optical data, we derive a self-consistent effective temperature of 31,300 {+-} 500 K, a surface gravity of log g = 7.8 {+-} 0.1 (M = 0.52 M{sub sun}), and a hydrogen abundance of log N(H)/N(He)< -4.0. The FUSE spectra reveal the presence of C II and C III lines that complement the previous detection of C II transitions with the GHRS. The improved carbon abundance in this hot object is log N(C)/N(He) = -6.15 {+-} 0.23. No photospheric features associated with other heavy elements are detected. We reconsider the role of PG 0112+104 in the definition of the blue edge of the V777 Her instability strip in light of our high-speed photometry and contrast our results with those of previous observations carried out at the McDonald Observatory.

  12. SIMULTANEOUS MULTIWAVELENGTH AND OPTICAL MICROVARIABILITY OBSERVATIONS OF CTA 102 (PKS J2232+1143)

    SciTech Connect

    Osterman Meyer, Angela; Miller, H. Richard; Marshall, Kevin; Ryle, Wesley T.; Aller, Hugh; Aller, Margo; Balonek, Tom

    2009-12-15

    We present analysis of both the short-term optical and long-term multiwavelength variability of CTA 102. In 2004, this object was observed in an intense optical flaring state. Extensive R-band microvariability observations were carried out during this high state. In 2005, we obtained several weeks of contemporaneous radio, optical, and X-ray observations of CTA 102. These observations recorded distinct flaring activity in all three wavebands. Subsequent analysis revealed that this object may appear redder when in a brighter optical state, and that the X-ray, optical, and radio activity do not appear to be correlated. The shape of the observed spectral energy distributions suggests that both synchrotron-related and external inverse Compton processes may contribute to the X-ray emission. Our results are also compared to other results on this object and archival microvariability observations. It appears that more rapid, dramatic microvariability events occur when CTA 102 is in an elevated optical flux state.

  13. A new multi-wavelength model-based method for determination of enzyme kinetic parameters.

    PubMed

    Sorouraddin, Mohammad-Hossein; Amini, Kaveh; Naseri, Abdolhossein; Vallipour, Javad; Hanaee, Jalal; Rashidi, Mohammad-Reza

    2010-09-01

    Lineweaver-Burk plot analysis is the most widely used method to determine enzyme kinetic parameters. In the spectrophotometric determination of enzyme activity using the Lineweaver-Burk plot, it is necessary to find a wavelength at which only the substrate or the product has absorbance without any spectroscopic interference of the other reaction components. Moreover, in this method, different initial concentrations of the substrate should be used to obtain the initial velocities required for Lineweaver-Burk plot analysis. In the present work, a multi-wavelength model-based method has been developed and validated to determine Michaelis-Menten constants for some enzyme reactions. In this method, a selective wavelength region and several experiments with different initial concentrations of the substrate are not required. The absorbance data of the kinetic assays are fitted by non-linear regression coupled to the numeric integration of the related differential equation. To indicate the applicability of the proposed method, the Michaelis-Menten constants for the oxidation of phenanthridine, 6-deoxypenciclovir and xanthine by molybdenum hydroxylases were determined using only a single initial concentration of the substrate, regardless of any spectral overlap.

  14. Multi-wavelength fine structure and mass flows in solar microflares

    NASA Astrophysics Data System (ADS)

    Berkebile-Stoiser, S.; Gömöry, P.; Veronig, A. M.; Rybák, J.; Sütterlin, P.

    2009-10-01

    Aims: We study the multi-wavelength characteristics at high spatial resolution, as well as chromospheric evaporation signatures of solar microflares. To this end, we analyze the fine structure and mass flow dynamics in the chromosphere, transition region and corona of three homologous microflares (GOES class multi-wavelength analysis using temporally and spatially highly resolved imaging data from the Dutch open telescope (Hα, Ca ii H), the transition region and coronal explorer (17.1 nm), the extreme-ultraviolet imaging telescope (19.5 nm), and the Reuven Ramaty high energy solar spectroscopic imager (≳3 keV) was carried out. EUV line spectra provided by the coronal diagnostic spectrometer are searched for Doppler shifts in order to study associated plasma flows at chromospheric (He i, T˜3.9× 104 K), transition region (e.g. O v, T˜ 2.6× 105 K), and coronal temperatures (Si xii, T˜ 2× 106 K). RHESSI X-ray spectra provide information about non-thermal electrons. Results: The multi-wavelength appearance of the microflares is in basic agreement with the characteristics of large flares. For the first event, a complex flare sequence is observed in TRACE 17.1 nm images (T≈ 1 MK), which show several brightenings, narrow loops of enhanced emission, and an EUV jet. EIT 19.5 nm data (T≈ 1.5 MK) exhibit similar features for the third event. DOT measurements show finely structured chromospheric flare brightenings for all three events, loop-shaped fibrils of increased emission between Hα brightenings, as well as a similar feature in Ca ii. For all three events, a RHESSI X-ray source (3-8 keV, T ≳ 10 MK) is located in between two chromospheric brightenings situated in magnetic flux of opposite polarity. We find the flow dynamics associated with the events to be very complex. In the chromosphere and transition region, CDS observed downflows for the first (v ≲ 40 km s-1), and

  15. Use of a Multiwavelength Pyrometer in Several Elevated Temperature Aerospace Applications

    NASA Technical Reports Server (NTRS)

    Ng, Daniel; Fralick, Gustave

    2001-01-01

    A multiwavelength pyrometer was developed for applications unique to aerospace environments. It was shown to be a useful and versatile technique for measuring temperature, even when the emissivity is unknown. It has also been used to measure the surface temperatures of ceramic zircomia thermal barrier coatings and alumina. The close agreement between pyrometer and thin film thermocouple temperatures provided an independent check. Other applications of the multiwavelength pyrometer are simultaneous surface and bulk temperature measurements of a transparent material, and combustion gas temperature measurement using a special probe interfaced to the multiwavelength pyrometer via an optical fiber. The multiwavelength pyrometer determined temperature by transforming the radiation spectrum in a broad wavelength region to produce a straight line (in a certain spectral region), whose intercept in the vertical axis gives the temperature. Implicit in a two-color pyrometer is the assumption of wavelength independent emissivity. Though the two data points of a two-color pyrometer similarly processed would result immediately in a similar straight line to give the unknown temperature, the two-color pyrometer lacks the greater data redundancy of the multiwavelength pyrometer, which enables it to do so with improved accuracy. It also confirms that emissivity is indeed wavelength independent, as evidenced by a multitude of the data lying on a simple straight line. The multiwavelength pyrometer was also used to study the optical transmission properties of a nanostructured material from which a quadratic exponential functional frequency dependence of its spectral transmission was determined. Finally, by operating the multiwavelength pyrometer in a very wide field of view mode, the surface temperature distribution of a large hot surface was obtained through measurement of just a single radiation spectrum.

  16. Aerosol Optical Properties Characterization By Means Of The CNR-IMAA Multi-Wavelength Raman Lidar

    NASA Astrophysics Data System (ADS)

    Mona, L.; Amodeo, A.; D'Amico, G.; Pappalardo, G.

    2007-12-01

    A Raman/elastic lidar for tropospheric aerosol study is operational at CNR-IMAA (40°36'N, 15°44'E, 760 m above sea level) since May 2000 in the framework of EARLINET. Since August 2005, this system provides aerosol backscatter coefficient profiles at 1064 nm, and independent measurements of aerosol extinction and backscatter coefficient profiles at 355 and 532 nm. In this way, lidar ratio (i.e. extinction to backscatter ratio) profiles at 355 and 532 nm are also obtained. In addition, depolarization ratio measurements at 532 nm are obtained by means of detection of components of backscattered light polarized perpendicular and parallel to the direction of the linearly polarized transmitted laser beam. Depolarization ratio measurements provide information about shape and orientation of aerosolic particles, while lidar ratio measurements and wavelength dependences of both backscatter and extinction are important for aerosol characterization in terms of aerosol type and size. In addition, high quality multi-wavelength measurements (3 backscatter + 2 extinction) can allow the determination of microphysical aerosol properties (refractive index, single-scattering albedo and effective particles radii). Systematic measurements are performed three times per week according to the EARLINET schedule since May 2000, and further measurements are performed in order to investigate particular events, like dust intrusions, volcanic eruptions and forest fires. This extended dataset allows the optical characterization of aerosol located close to the surface, namely in the Planetary Boundary Layer, as well as in the free troposphere. In the free troposphere, an high occurrence of Saharan dust intrusions at CNR-IMAA (about 1 day of Saharan dust intrusion every 10 days) has been identified by means of back-trajectory analysis and in accordance with satellite images, because of the short distance from the Sahara region. In addition, CNR-IMAA is pretty close to Etna, the largest European

  17. Model fitting of the kinematics of ten superluminal components in blazar 3C 279

    NASA Astrophysics Data System (ADS)

    Qian, Shan-Jie

    2013-07-01

    The kinematics of ten superluminal components (C11- C16, C18, C20, C21 and C24) of blazar 3C 279 are studied from VLBI observations. It is shown that their initial trajectory, distance from the core and apparent speed can be well fitted by the precession model proposed by Qian. Combined with the results of the model fit for the six superluminal components (C3, C4, C7a, C8, C9 and C10) already published, the kinematics of sixteen superluminal components can now be consistently interpreted in the precession scenario with their ejection times spanning more than 25 yr (or more than one precession period). The results from model fitting show the possible existence of a common precessing trajectory for these knots within a projected core distance of ~0.2-0.4 mas. In the framework of the jet-precession scenario, we can, for the first time, identify three classes of trajectories which are characterized by their collimation parameters. These different trajectories could be related to the helical structure of magnetic fields in the jet. Through fitting the model, the bulk Lorentz factor, Doppler factor and viewing angle of these knots are derived. It is found that there is no evidence for any correlation between the bulk Lorentz factor of the components and their precession phase (or ejection time). In a companion paper, the kinematics of another seven components (C5a, C6, C7, C17, C19, C22 and C23) have been derived from model fitting, and a binary black-hole/jet scenario was envisaged. The precession model proposed by Qian would be useful for understanding the kinematics of superluminal components in blazar 3C 279 derived from VLBI observations, by disentangling different mechanisms and ingredients. More generally, it might also be helpful for studying the mechanism of jet swing (wobbling) in other blazars.

  18. An Emerging Class of Gamma-ray Flares from Blazars: Beyond One-zone Models

    NASA Astrophysics Data System (ADS)

    Tavani, M.; Vittorini, V.; Cavaliere, A.

    2015-11-01

    Blazars radiate from relativistic plasma jets with bulk Lorentz factors {{Γ }}∼ 10, closely aligned along our line of sight. In a number of blazars of the flat-spectrum radio quasar type, such as 3C 454.3 and 3C 279, gamma-ray flares have recently been detected with very high luminosity and few or no counterparts in the optical and soft X-ray bands. They challenge the current one-zone leptonic models of emissions from within the broad-line region (BLR). The latter envisage the optical/X-ray emissions to be produced as synchrotron radiation by the same population of highly relativistic electrons in the jet that would also yield the gamma rays by inverse Compton upscattering of surrounding soft photons. To meet the challenge, we present here a model based on primary synchrotron photons emitted in the BLR by a plasmoid moving out with the jet and scattered back toward the incoming plasmoid by an outer plasma clump acting as a mirror. We consider both a scenario based on a static mirror located outside the BLR and an alternative provided by a moving mirror geometry. We show that mirroring phenomena can locally enhance the density and anisotropy with associated relativistic boosting of soft photons within the jet, so as to trigger bright inverse Compton gamma-ray transients from nearly steady optical/X-ray synchrotron emissions. In this picture we interpret the peculiarly asymmetric light curves of the recently detected gamma-ray flares from 3C 279. Our scenario provides a promising start to understanding the widening class of bright and transient gamma-ray activities in blazars.

  19. Resolving the blazar CGRaBS J0809+5341 in the presence of telescope systematics

    NASA Astrophysics Data System (ADS)

    Natarajan, Iniyan; Paragi, Zsolt; Zwart, Jonathan; Perkins, Simon; Smirnov, Oleg; van der Heyden, Kurt

    2017-02-01

    We analyse very long baseline interferometry (VLBI) observations of the blazar CGRaBS J0809+5341 using Bayesian inference methods. The observation was carried out at 5 GHz using eight telescopes which form part of the European VLBI Network. Imaging and deconvolution using traditional methods imply that the blazar is unresolved. To search for source structure beyond the diffraction limit, we perform Bayesian model selection between three source models (point, elliptical Gaussian and circular Gaussian). Our modelling jointly accounts for antenna-dependent gains and system equivalent flux densities. We obtain posterior distributions for the various source and instrumental parameters along with the corresponding uncertainties and correlations between them. We find that there is very strong evidence (>109:1) in favour of an elliptical Gaussian structure and using this model derive the apparent brightness temperature distribution of the blazar, accounting for uncertainties in the shape estimates. To test the integrity of our method, we also perform model selection on synthetic observations and use this to develop a Bayesian criterion for the minimum resolvable source size and consequently the maximum measurable brightness temperature for a given interferometer, dependent on the signal-to-noise ratio (SNR) of the data incorporating the aforementioned systematics. We find that calibration errors play an increasingly important role in determining the over-resolution limit for SNR≫100. We show that it is possible to exploit the resolving power of future VLBI arrays down to about 5 per cent of the size of the naturally weighted restoring beam, if the gain calibration is precise to 1 per cent or less.

  20. Masses, Dimensionless Kerr Parameters, and Emission Regions in GeV Gamma-Ray-loud Blazars

    NASA Astrophysics Data System (ADS)

    Xie, G.-Z.; Ma, L.; Liang, E.-W.; Zhou, S.-B.; Xie, Z.-H.

    2003-11-01

    We have compiled sample of 17 GeV γ-ray-loud blazars, for which rapid optical variability and γ-ray fluxes are well observed, from the literature. We derive estimates of the masses, the minimum Kerr parameters amin, and the size of the emission regions of the supermassive black holes (SMBHs) for the blazars in the sample from their minimum optical variability timescales and γ-ray fluxes. The results show that (1) the masses derived from the optical variability timescale (MH) are significantly correlated with the masses from the γ-ray luminosity (MKNH); (2) the values of amin of the SMBHs with masses MH>=108.3 Msolar (three out of 17 objects) range from ~0.5 to ~1.0, suggesting that these SMBHs are likely to be Kerr black holes. For the SMBHs with MH<108.3 Msolar, however, amin=0, suggesting that a nonrotating black hole model cannot be ruled out for these objects. In addition, the values of the size of the emission region, r*, for the two kinds of SMBHs are significantly different. For the SMBHs with amin>0, the sizes of the emission regions are almost within the horizon (2rG) and marginally bound orbit (4rG), while for those with amin=0 they are in the range (4.3-66.4)rG, extending beyond the marginally stable orbit (6rG). These results may imply that (1) the rotational state, the radiating regions, and the physical processes in the inner regions for the two kinds of SMBH are significantly different and (2) the emission mechanisms of GeV γ-ray blazars are related to the SMBHs in their centers but are not related to the two different kinds of SMBH.