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Sample records for bl lacertae objects

  1. No evidence for radio-quiet BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Stocke, John T.; Morris, Simon L.; Gioia, Isabella; Maccacaro, Tommmaso; Schild, R. E.

    1990-01-01

    Using a large, flux-limited sample of faint X-ray sources, a search has been conducted for radio-quiet BL Lacertae objects. None has been found. Thirty-two X-ray-selected BL Lac objects and BL Lac candidates have been found within the sources of the Einstein Medium Sensitivity Survey (EMSS). Thirty-one of these have been observed with the VLA and all have been detected at 5 GHz. While the optical magnitudes of the EMSS BL Lac objects range from 17 to 20.8, their radio-to-optical spectral indices occupy a very small range. The very bright X-ray-selected BL Lac objects like PKS 2155-304 and Markarian 501 have similar range values. Therefore, unlike the clear dichotomy between radio-loud quasars and radio-quiet QSOs, there is no evidence for two populations of Lacertids distinguished by radio loudness.

  2. Photometric monitoring of 12 BL Lacertae objects

    NASA Astrophysics Data System (ADS)

    Xie, G. Z.; Zhou, S. B.; Dai, B. Z.; Liang, E. W.; Li, K. H.; Bai, J. M.; Xing, S. Y.; Liu, W. W.

    2002-02-01

    We present the results of our monitoring the flux variability of 12 BL Lac objects, which have variabilities on time-scales ranging from hours to months. Individual sources are discussed in detail. Three of them, OY091, H0548-322 and 0048-097, show significant rapid variation (hours). Two of them, 3C 66A and Mrk 501, exhibit significant variability on time-scales of months. We find that 3C 66A has a variability period of 63+/-5d, supporting the 65-d period obtained by Lainela et al. The periodicity seems to be weak according to the Jurkevich Vm2 test. We also find a correlation between B-V colour index and B magnitude for Mrk 421. We discuss possible physical mechanisms on the basis of these observational phenomena.

  3. X-ray spectroscopy of five BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Urry, C. M.; Mushotzky, R. F.; Holt, S. S.

    1986-01-01

    Five X-ray bright BL Lacertae objects were observed in the energy range 0.6-4.5 keV with the solid state spectrometer (SSS) of the Einstein Observatory. The 14 SSS spectra obtained represent most of the X-ray spectra of BL Lac objects with resolution better than approximately 3. These data do not reveal the presence of large amounts of thermal gas, with upper limits for the equivalent width of individual spectral features typically less that about 100 eV. However, the SSS spectra are the first set of X-ray data to indicate low-energy absorption in excess of that caused by the cold interstellar matter in the Galaxy. Comparison with contemporaneous, lower energy X-ray data implies that this absorption does not arise in cold neutral material, but in hotter, highly ionized material, probably intrinsic to the source. All five BL Lac objects have X-ray continua that are well fitted by power-law models, with power-law energy indices usually greater than about 1. In a few cases, a flattening at higher energies is observed; these and other data suggest that two-component X-ray spectra, steep at low energies and flat at high energies, are a common feature of BL Lac objects. Three of the five sources clearly vary between SSS observations, with time scales ranging from days to years. A historical synopsis of the X-ray spectral data confirms the tendency for BL Lacertae objects to be highly variable in the X-ray band but reveals no correlation between spectral and intensity changes.

  4. The cosmic evolution of Fermi BL Lacertae objects

    SciTech Connect

    Ajello, M.; Romani, R. W.; Shaw, M. S.; Healey, S. E.; Michelson, P. F.; Gasparrini, D.; Bolmer, J.; Cotter, G.; Potter, W. J.; Finke, J.; Greiner, J.; Rau, A.; Schady, P.; King, O.; Max-Moerbeck, W.; Readhead, A. C. S.; Richards, J. L. E-mail: rwr@astro.stanford.edu E-mail: gasparrini@asdc.asi.it

    2014-01-01

    Fermi has provided the largest sample of γ-ray-selected blazars to date. In this work we use a uniformly selected set of 211 BL Lacertae (BL Lac) objects detected by Fermi during its first year of operation. We obtained redshift constraints for 206 out of the 211 BL Lac objects in our sample, making it the largest and most complete sample of BL Lac objects available in the literature. We use this sample to determine the luminosity function of BL Lac objects and its evolution with cosmic time. We find that for most BL Lac classes the evolution is positive, with a space density peaking at modest redshift (z ≈ 1.2). Low-luminosity, high-synchrotron-peaked (HSP) BL Lac objects are an exception, showing strong negative evolution, with number density increasing for z ≲ 0.5. Since this rise corresponds to a drop-off in the density of flat-spectrum radio quasars (FSRQs), a possible interpretation is that these HSPs represent an accretion-starved end state of an earlier merger-driven gas-rich phase. We additionally find that the known BL Lac correlation between luminosity and photon spectral index persists after correction for the substantial observational selection effects with implications for the so-called 'blazar sequence'. Finally, by estimating the beaming corrections to the luminosity function, we find that BL Lac objects have an average Lorentz factor of γ=6.1{sub −0.8}{sup +1.1}, and that most are seen within 10° of the jet axis.

  5. A survey of the milliarcsecond polarization properties of BL Lacertae objects at 5 GHz

    NASA Technical Reports Server (NTRS)

    Gabuzda, D. C.; Cawthorne, T. V.; Roberts, D. H.; Wardle, J. F. C.

    1992-01-01

    Consideration is given to millarcsecond-resolution total-intensity and linear polarization maps at 5 GHz presented for 11 BL Lacertae objects. In every BL Lacertae object in which polarization structure was detected, the polarization position angle of the knots is nearly parallel to the VLBI structural axis. The direction of the polarization in the cores of these sources appears to be random. The preferred polarization direction in the jets is explained by the fact that plane perpendicular shock waves are common in these sources; the origin of the absence of the preferred polarization direction in the core components is unclear. These results support an early conclusion that it cannot be the case that a significant number of BL Lacertae objects are gravitationally microlensed images of more distant quasars, since the characteristic VLBI polarization structures observed in these two types of objects are very different.

  6. The fraction of BL Lacertae objects in groups of galaxies

    NASA Astrophysics Data System (ADS)

    Muriel, H.

    2016-06-01

    Context. BL Lac objects are a rare class of active galactic nuclei that typically show featureless optical spectra that make it difficult to estimate the redshift. A novel method for estimating the redshift of BL Lac objects has recently been proposed which assumes that these objects typically reside in groups of galaxies. Aims: The aim of this work is to estimate the fraction of BL Lac objects that reside in groups of galaxies. Methods: We use a sample of groups (M12 catalogue) selected by applying a friends-of-friends algorithm in the SDSS DR12. Galaxies in the M12 sample were cross-correlated with the sample of blazars in the BZCAT. We found that 121 galaxies in the M12 catalogue are blazars in the BZCAT sample, all but one are BL Lac objects, and a large fraction are classified as BL Lac-galaxy dominated. Results: Analysing the fraction of galaxies in groups as a function of redshift we have estimated a correction factor that takes into account the typical incompleteness of the catalogues based on the friends-of-friends algorithm. Once this factor was applied to the sample of BL Lac objects with a counterpart in the M12 catalogue, we found that the percentage of BL Lac objects in groups is ≳ 67 ± 8%. Conclusions: The high rate of BL Lac objects in groups found in this work strongly supports a recent method that has successfully estimated the redshift of BL Lac objects with featureless spectra.

  7. Ultraviolet spectra of QSOs, BL Lacertae objects, and Seyfert galaxies

    NASA Technical Reports Server (NTRS)

    Lanzetta, Kenneth M.; Turnshek, David A.; Sandoval, Jennifer

    1993-01-01

    Motivated by the possibility of detecting strong absorption features toward extragalactic background objects, we present optimally extracted and co-added IUE spectra of QSOs, BL Lac objects, and Seyfert galaxies. These spectra together with those presented (in a similar work) by Kinney et al. form an essentially complete sample of the SWP, LWP, and LWR observations of QSOs, BL Lac objects, and Seyfert galaxies with redshifts z greater than 0.05 available in the IUE merged observation log as of 1991 December.

  8. Ultraviolet spectra of QSOs, BL Lacertae objects, and Seyfert galaxies

    NASA Astrophysics Data System (ADS)

    Lanzetta, Kenneth M.; Turnshek, David A.; Sandoval, Jennifer

    1993-02-01

    Motivated by the possibility of detecting strong absorption features toward extragalactic background objects, we present optimally extracted and co-added IUE spectra of QSOs, BL Lac objects, and Seyfert galaxies. These spectra together with those presented (in a similar work) by Kinney et al. form an essentially complete sample of the SWP, LWP, and LWR observations of QSOs, BL Lac objects, and Seyfert galaxies with redshifts z greater than 0.05 available in the IUE merged observation log as of 1991 December.

  9. X ray constraints on the beaming hypothesis for BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Padovani, P.; Urry, C. M.

    1989-01-01

    BL Lacertae objects may be Fanaroff-Riley type I (FR I) galaxies with a relativistic jet roughly parallel to the line of sight. The ratio of parent objects (FR Is) to beamed objects (BL Lacs) depends only on the jet velocity. Recently this ratio become observable. X-ray-flux-limited samples are used to demonstrate the viability of the beaming hypothesis. In the process, the X-ray luminosity functions of FR I galaxies and BL Lac objects are derived. Their respective contributions to the cosmic X-ray background radiation are calculated.

  10. Accretion disk emission from a BL Lacertae object

    NASA Technical Reports Server (NTRS)

    Urry, C. Megan; Wandel, Amri

    1990-01-01

    The accretion disk is an attractive model for BL Lac objects because of its preferred axis and high efficiency. While the smooth continuum spectra of BL Lacs do not show large UV bumps, in marked contrast to quasars, high quality simultaneous data do reveal deviations from smoothness. Using detailed calculations of cool accretion disk spectra, the best measured ultraviolet and soft x ray spectra of the BL Lac object PKS 2155-304 are fitted. The mass and accretion rate required are determined. A hot disk or corona could comptonize soft photons from the cool disk and produce the observed power law spectrum in the 1 to 10 keV range. The dynamic time scales in the disk regions that contribute most of the observed ultraviolet and soft x ray photons are consistent with the respective time scales for intensity variations. The mass derived from fitting the continuum spectrum is consistent with the limit derived from the fastest hard x ray variability.

  11. VLBI observations of seven BL Lacertae objects from RGB sample

    NASA Astrophysics Data System (ADS)

    Wu, Zhongzu; Jiang, D. R.; Gu, Minfeng; Liu, Yi

    2007-04-01

    We present EVN observations of seven BL Lac objects selected from the RGB sample. To investigate the intrinsic radiation property of BL Lac objects, we estimated the Doppler factor with the VLA or MERLIN core and the total 408 MHz luminosity for a sample of 170 BL Lac objects. The intrinsic (comoving) synchrotron peak frequency was then calculated by using the estimated Doppler factor. Assuming a Lorentz factor of 5, the viewing angle of jets was constrained. The high-resolution VLBI images of seven sources all show a core-jet structure. We estimated the proper motions of three sources with the VLBI archive data, and find that the apparent speed increases with the distance of components to the core for all of them. In our BL Lacs sample, the Doppler factor of LBLs is systematically larger than that of IBLs and HBLs. We find a significant anti-correlation between the total 408 MHz luminosity and the intrinsic synchrotron peak frequency. However, the scatter is much larger than for the blazar sequence. Moreover, we find a significant positive correlation between the viewing angle and the intrinsic synchrotron peak frequency. The BL Lac objects show a continuous distribution on the viewing angle. While LBLs have a smaller viewing angle than that of IBLs and HBLs, IBLs are comparable to HBLs. We conclude that the intrinsic synchrotron peak frequency is not only related to the intrinsic radio power (though with a large scatter), but also to the viewing angle for the present sample. Tables 1-4 are only available in electronic form at http://www.aanda.org

  12. Spectroscopy of BL Lacertae objects of extraordinary luminosity

    NASA Astrophysics Data System (ADS)

    Landoni, M.; Falomo, R.; Treves, A.; Sbarufatti, B.

    2014-10-01

    Aims: We aim to determine the redshift (or stringent lower limits) of a number of bright BL Lacs objects. Methods: We secured optical and near-infrared medium-resolution spectra of four bright BL Lac objects of unknown redshift using the spectrograph X-Shooter at the ESO-VLT. Results: In spite of the high quality of the spectra and the extended spectral range of the observations, we have not detected intrisic spectral features for these sources. However, we are able to provide strigent lower limits to their redshift. In particular, for the two TeV sources PG 1553+113 and H 1722+119, we infer z> 0.30 and z> 0.35 respectively. We also detect an intervening Ca II absorption doublet in the spectrum of MH 2136-428 that is ascribed to the halo of a nearby giant elliptical galaxy at a projected distance of ~100 kpc. Conclusions: Under the hypothesis that all BL Lacs are hosted by a luminous bulge-dominated galaxies, the spectroscopic observations of bright BL Lacs presently indicate that these objects are likely sources with extremely beamed nuclear emission. We present simulations to show under which circumstances it is possible to probe this hypothesis from the detection of very weak absorptions using the next generation of extremely large optical telescopes. Figures 6-17 are available in electronic form at http://www.aanda.orgThe full spectra 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/570/A126

  13. Looking for the least luminous BL Lacertae objects

    NASA Astrophysics Data System (ADS)

    Capetti, A.; Raiteri, C. M.

    2015-08-01

    Among active galactic nuclei, BL Lac objects show extreme properties that have been interpreted as the effect of relativistic beaming on the emission from a plasma jet oriented close to the line of sight. The Doppler amplification of the jet emission makes them ideal targets for studying jet physics. In particular, low-power BL Lacs (LPBL) are very interesting because they probe the jet formation and emission processes at the lowest levels of accretion. However, they are difficult to identify since their emission is swamped by the radiation from the host galaxy in most observing bands. In this paper we propose a new LPBL selection method based on the mid-infrared emission, in addition to the traditional optical indices. We considered the radio-selected sample of Best & Heckman (2012, MNRAS, 421, 1569) and cross-matched it with the WISE all-sky survey. In a new diagnostic plane including the W2-W3 color and the Dn(4000) index, LPBL are located in a region scarcely populated by other sources. By filtering objects with small emission line equivalent width, we isolated 36 LPBL candidates up to redshift 0.15. Their radio luminosity at 1.4 GHz spans the range log Lr = 39.2-41.5 [erg s-1]. Considering the completeness of our sample, we analyzed the BL Lac luminosity function (RLF), finding a dramatic paucity of LPBL with respect to the extrapolation of the RLF toward low power. This requires a break in the RLF located at log Lr ~ 40.6 [erg s-1]. The consequent peak in the BL Lacs number density is possibly the manifestation of a minimum power required to launch a relativistic jet.

  14. Possible links between BL Lacertae objects and quasars from very long baseline interferometry radio data.

    PubMed Central

    Gabuzda, D C

    1995-01-01

    Systematic differences in the very long baseline interferometry (VLBI) radio polarization structure and average VLBI component speeds of BL Lacertae objects and quasars support the view that the observational distinction between these classes, based in large part on the strength of their optical line emission, is meaningful; in other words, this distinction reflects significant differences in the physical conditions in these sources. Possible models providing a link between the optical and VLBI properties of BL Lacertae objects and quasars are discussed. Most VLBI polarization observations to date have been global observations made at 6 cm; recent results suggest that the VLBI polarization structure of some sources may change dramatically on scales smaller than those probed by these 6-cm observations. PMID:11607606

  15. Accretion disk emission from a BL Lacertae object

    NASA Technical Reports Server (NTRS)

    Wandel, Amri; Urry, C. Megan

    1991-01-01

    It is suggested here that the UV and X-ray emission of BL Lac objects may originate in an accretion disk. Using detailed calculations of accretion disk spectra, the best-measured ultraviolet and soft X-ray spectra of the BL Lac object PKS 2155-304 are fitted, and the mass and accretion rate required is determined. The ultraviolet through soft X-ray continuum is well fitted by the spectrum of an accretion disk, but near-Eddington accretion rates are required to produce the soft X-ray excess. A hot disk or corona could Comptonize soft photons from the cool disk and produce the observed power-law spectrum in the 1-10 keV range. The dynamic time scale in the disk regions that contribute most of the observed ultraviolet and soft X-ray photons are consistent with the respective time scales for intensity variations observed in these two wave bands; the mass derived from fitting the continuum spectrum is consistent with the limit derived from the fastest hard X-ray variability.

  16. Upper limits from hard X-ray observations of five BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Bezler, M.; Gruber, D. E.; Rothschild, R. E.

    1988-01-01

    Results are presented from hard X-ray observations of the five brightest X-ray BL Lacertae objects: PKS 0548-322, Mrk 421 (=1101+384), 2A 1219+305, Mrk 501 (=1652+398), and PKS 2155-304. The observations covered the energy range 15-165 keV from August 1977 to December 1978. The results are compared with previous studies.

  17. Simultaneous observations of the BL Lacertae object I Zw 187

    NASA Technical Reports Server (NTRS)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Pollock, J. T.; Pica, A. J.; Smith, A. G.; Webb, J. R.; Ku, W. H.-M.; Rudy, R. J.; Levan, P. D.

    1982-01-01

    Two sets of simultaneous spectra consisting of data obtained with radio, IR, optical, UV and X-ray telescopes were obtained 10 months apart for the X-ray bright BL Lac object IZw 187. In addition, nonsimultaneous observations were made in several of the aforementioned observing bands in order to detect flux variations and galactic light contamination was removed from all observations. The BL Lac component is found to have a weak 3000 A bump superposed on an IR-optical-UV spectrum of slope 0.9. Consistent with the arising of the IR-through-X-ray continuum from a single synchrotron source, the X-ray data fall on or near an extrapolation of this power law. No flux variations have been detected in the flat radio spectrum. Optical and X-ray fluxes are observed to vary by a factor not greater than three, and the shortest variability time scales in these bands are comparable at about one week.

  18. Coordinated observations of X-ray bright BL lacertae objects

    NASA Technical Reports Server (NTRS)

    Urry, C. M.

    1985-01-01

    Simultaneous multifrequency observations of the BL Lac object Mkn421 covering radio through X-ray wavelengths were performed. Composite multifrequency spectra of the central nonthermal component were obtained at the two epochs after subtracting the optical and infrared light of the underlying galaxy. Physical parameters of Mkn421 are discussed in terms of the synchrotron self-Compton model. Taking the spectral turnover between infrared and radio for synchrotrom self absorption, the radio emmision originates in a more extended region than the infrared to X-ray emission, the source size of which should be less than .01 milliarcseconds. Relativistic beaming is required if the angular size is smaller than a few times .001 milliarcseconds. A possible explanation of the spectral change during the two epochs is also discussed.

  19. QUANTITATIVE EVALUATION OF THE HYPOTHESIS THAT BL LACERTAE OBJECTS ARE QSO REMNANTS

    SciTech Connect

    Borra, E. F.

    2014-11-20

    We evaluate with numerical simulations the hypothesis that BL Lacertae objects (BLLs) are the remnants of quasi-stellar objects. This hypothesis is based on their highly peculiar redshift evolution. They have a comoving space density that increases with decreasing redshift, contrary to all other active galactic nuclei. We assume that relativistic jets are below detection in young radio-quiet quasars and increase in strength with cosmic time so that they eventually are detected as BLLs. Our numerical simulations fit very well the observed redshift distributions of BLLs. There are strong indications that only the high-synchrotron-peaked BLLs could be QSO remnants.

  20. Multifrequency Observations of BL Lacertae Object A0 0235+164

    NASA Astrophysics Data System (ADS)

    Howard, E. S.; Webb, J. R.; Benitez, E. M.; Balonek, T. J.; McGrath, E.; Shrader, C. R.; Inst. de Astronomia Team; CGRO/LHEA Team

    1999-05-01

    The BL Lacertae Object A0 0235+164 dramatically increased in brightness on October 20, 1997. This outburst was dectected with the 1 meter SARA (Southeastern Association for Research in Astronomy) telescope located at Kitt Peak National Observatory (KPNO). As a result of our observations, AO 0235+164 was also observed during the outburst by the Rossi X-ray Timing Experiment (RXTE), Foggy Bottom Observatory (Colgate), and University of Michigan 26 meter Radio telescope as a part of a Target of Opportunity (TOO) program. We present here the historical lightcurve A0 0235+164, multifrequency observations and multifrequency spectra collected during the 1997 through 1998 outburst.

  1. Optical periodicity analysis for radio selected BL Lacertae objects (RBLs)

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Lin, R. G.; Xie, G. Z.; Zhang, L.; Mei, D. C.; Su, C. Y.; Peng, Z. M.

    2002-01-01

    The recently compiled historical lightcurves of 10 RBLs are probed with the Jurkevich method in a search for periodic behaviour. Monte Carlo simulations of artificial lightcurves are used to detect spurious periods and evaluate sources of error in this kind of analysis. Additional analysis based on the discrete correlation function (DCF) provides confirmation for those periods that could have physical significance. We find that periods in the range 1.4-17.85 yr are present in nine objects of the sample. Figures 2 to 10 are only available in electronic form at http://www.edpsciences.org

  2. Fanaroff-Riley I galaxies as the parent population of BL Lacertae objects. I - X-ray constraints

    NASA Technical Reports Server (NTRS)

    Padovani, P.; Urry, C. M.

    1990-01-01

    The hypothesis that BL Lacertae objects are a special subset of Fanaroff-Riley type I radio galaxies, namely, those dominated by beamed emission from a relativistic jet aligned with the line of sight, is examined by looking at the relative number densities. The calculation depends primarily on observed quantities, including the X-ray luminosity function of Fanaroff-Riley type I galaxies. The model predicts the X-ray luminosity function of BL Lacertae objects, the shape of the X-ray counts below currently observed fluxes, and the velocity of the X-ray emitting jet. With Fanaroff-Riley type I galaxies as the parent population the flat luminosity function, the observed X-ray number counts, and the partial redshift distribution of BL Lacertae objects can be explained.

  3. The Spectroscopic Properties of a New Uniform Sample of BL Lacertae Objects

    NASA Astrophysics Data System (ADS)

    Rector, Travis A.; Laurent-Muehleisen, Sally; Stocke, John

    1999-02-01

    We propose to study spectroscopically the new ROSAT-Green Bank (RGB) sample of BL Lacertae objects. Prior X-ray and radio surveys have discovered only the most extreme BL Lacs (i.e., the most radio or X-ray bright), causing an artificial separation of BL Lacs into two classes, radio loud and X-ray loud BL Lacs (RBLs and XBLs respectively). Not suprisingly then, efforts to understand the relationship between RBLs and XBLs have not been successful. However, the RGB survey has discovered BL Lacs intermediate to XBLs and RBLs (i.e., ``optically- peaked" BL Lacs); and as a whole the RGB is the only sample which spans the entire observed range of broadband spectral energy distributions. However, redshifts are known for only half of the RGB, making the overall intrinsic properties of the sample highly uncertain. We therefore propose to obtain high-SNR spectra of RGB BL Lacs without redshifts to determine redshifts and spectral line properties. The multiwavelength luminosity functions as well as the distribution of redshifts, emission-line luminosities, V/V_max, MgII absorption systems and starlight fractions will be used to determine the relationship between XBLs, RBLs and quasars. This data will also be used in a research-based science education program (RBSE) operated by NOAO, wherein middle- and high-school science students learn astronomy and inquiry-based learning skills via research.

  4. CCD photometry of the BL Lacertae object 1400+162 and the associated group of galaxies

    NASA Technical Reports Server (NTRS)

    Weistrop, D.; Reitsema, H. J.; Smith, B. A.; Shaffer, D. B.

    1983-01-01

    Surface photometry of the BL Lacertae object 1400+162 and an apparently associated group of galaxies has been obtained using a CCD camera. Observations were made in V, broad bandpasses centered on 0.75 micron and 1.0 micron and with no filter. The colors of all but two of the galaxies suggest they are ellipticals, with the colors of the remaining two considerably bluer. Analysis using a method described by Schechter and Press (1976) suggests the group is a small one. The group may be similar to the one associated with the quasar 3C 273. The spectral index of the BL Lac object is 1.49 + or 0.21. This value allows, but does not require, the presence of an underlying elliptical galaxy. The radio-optical and optical-X-ray indices for 1400+162 are similar to values found for quasars.

  5. 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.

  6. A model of the polarization position-angle swings in BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Konigl, A.; Choudhuri, A. R.

    1985-01-01

    The polarization position-angle swings that have been measured in a number of BL Lacertae objects and highly variable quasars are interpreted in terms of shock waves which illuminate (by enhanced synchrotron radiation) successive transverse cross sections of a magnetized, relativistic jet. The jet is assumed to have a nonaxisymmetric magnetic field configuration of the type discussed in the companion paper on the equilibria of force-free jets. For a jet that is viewed at a small angle to the axis, the passage of a shock will give rise to an apparent rotation of the polarization position angle whose amplitude can be substantially larger than 180 deg. The effects of freely propagating shocks are compared with those of bow shocks which form in front of dense obstacles in the jet, and specific applications to 0727 - 115 and BL Lacertae are considered. In the case of 0727 - 115, it is pointed out that the nonuniformity of the swing rate and the apparent oscillations of the degree of polarization could be a consequence of relativistic aberration.

  7. X-ray Emission of Low-Energy-Peaked BL Lacertae Objects

    SciTech Connect

    Randall, Jill M.; Perlman, Eric S.

    2009-12-18

    Presented here is an analysis of X-ray observations of the following seven low-energy-peaked BL Lacertae objects: BL Lacertae, S5 0716+71, W Comae, 3C 66A, S4 0954+65, OJ 287, and AO 0235+16. The spectral data for these objects were taken from observations by the XMM-Newton and/or Chandra X-ray observatories. These objects are being analyzed in an effort to reanalyze all XMM-Newton and Chandra data of low-energy BL Lacs, similar to the efforts of Perlman et al.[4] for high energy BL Lacs. The objects were studied in an effort to understand the nature of the X-ray and multi-waveband emissions in these objects, study the shape of the spectra, and compare the observations of low-energy-peaked BL Lacs to previous observations of these objects and also to observations of high-energy-peaked BL Lacs. Light curves and spectra were analyzed to look for evidence of spectral variability in the objects and as a comparison to previous research on these objects. Most data shows both synchrotron and Inverse-Compton emission, though only little correlation was seen between the emission strength and the spectral slope. Our data is generally well-fitted to a broken power law model with distinct bimodality seen in the first spectral index (six observations with {Gamma}{sub 1{approx}}0.4 and four observations with {Gamma}{sub 1{approx}}3.0), a break in energy between 0.6 and 1.4 keV, and a second spectral index {Gamma}{sub 2{approx}}2.0. None of the observations showed spectral lines, which is consistent with past results. For S5 0716+71 the XMM-Newton X-ray and optical data, along with radio data obtained from the University of Michigan Radio Astronomy Observatory (UMRAO), a spectral energy distribution was created and peak frequencies were estimated.

  8. Relativistic jet models for the BL Lacertae object Mrk 421 during three epochs of observation

    NASA Technical Reports Server (NTRS)

    Mufson, S. L.; Hutter, D. J.; Kondo, Y.; Wisniewski, W. Z.

    1988-01-01

    Coordinated observation of the nearby BL Lacertae object Mrk 421 obtained during May 1980, January 1984, and March 1984 are described. These observations give a time-frozen picture of the continuous spectrum of Mrk 421 at X-ray, ultraviolet, optical, and radio wavelengths. The observed spectra have been fitted to an inhomogeneous relativistic jet model. In general, the models reproduce the data well. Many of the observed differences during the three epochs can be attributed to variations in the opening angle of the jet and in the angle that the jet makes to the line of sight. The jet models obtained here are compared with the homogeneous, spherically symmetric, synchrotron self-Compton models for this source. The models are also compared with the relativistic jet models obtained for other active galactic nuclei.

  9. Radio Properties of Radio Selected and the X-Ray Selected BL Lacertae Objects

    NASA Astrophysics Data System (ADS)

    Yang, Fu-Li; Li, Yue-Huang; Yang, Jiang-He

    2008-09-01

    The authors collect the radio data (core and extended luminosity) for the radio (RBL) and X-ray (XBL) selected BL Lacertae objects, and calculate their core-dominance parameter. The results show that the total radio luminosity of RBLs is two decades higher than that of XBLs. A detailed analysis suggests that the difference is from the fact that the core luminosity of RBLs is two decades more powerful than that of XBLs whereas the extended luminosity is only one decade more powerful than that in the XBLs. They also investigate the correlation between the core/extended luminosity and the core-dominance parameter, the extended luminosity is anti-correlated with the core-dominance parameter, however, there is almost no correlation between the core/total luminosity and the core-dominance parameter for each subclass.

  10. Colour variation of the BL Lacertae object PKS 0537-441

    NASA Astrophysics Data System (ADS)

    Li, Xiaopan; Zhang, Li; Luo, Yuhui; Wang, Lisha; Zhou, Li

    2015-05-01

    We present the colour indices V - R of BL Lacertae object PKS 0537-441 on the basis of the photometric data monitored by the Rapid Eye Mounting (REM) telescope located at the ESO Cerro La Silla observatory (Chile). Nearly 700 quasi-simultaneous data groups were collected during the period from 2004 to 2010. Our colour analysis shows the existence of at least two variability mechanisms: one is the long-term chromatic mechanism in which the variation traces a 0.04 ± 0.01 slope in the V - R versus V plot, the other is the chromatic mechanism implying the spectral changes during the flares and on intraday time-scales. A general bluer-when-brighter trend is confirmed in both ascent and descent states during the flares and in the 2010 February flare interval, while a much stronger bluer-when-brighter chromatism is observed in both faint and bright states on intraday time-scales. The discrete correlation function analysis reveals the existence of a time-lag of 13^{+5.8}_{-1.2} d between colour indices and magnitudes during the period MJD 54404-54453, whereas no measurable time-lag during other periods is found. Our results suggest that geometric effects may be responsible for the long-term achromatic mechanism, while the intrinsic shock-in-jet mechanism may produce the chromatic variability during the flares and on intraday time-scales.

  11. Intraday optical variability of the BL Lacertae object S5 0716+714

    NASA Astrophysics Data System (ADS)

    Zhang, B. K.; Dai, B. Z.; Wang, L. P.; Zhao, M.; Zhang, L.; Cao, Z.

    2012-04-01

    The intraday optical variability of the BL Lacertae object S5 0716+714 is studied using historical light curves. The well-sampled intranight data set is selected. In total, 19 333 data points have been collected over 208 nights. The source exhibits strong variability in the optical band. At a confidence level of 99.9 per cent, for 162 of the 208 nights the source shows intranight variability. The source varies with an increasing rate of 0.043 mag h-1 and a decreasing rate of 0.036 mag h-1 during the observations, with no evident difference between rising and falling parts. The fast variability is found on JD 245 1909, with a decreasing rate of 0.015 mag min-1 over 6 min. The temporal characteristic is studied by using the structure function method. The result shows that the source varies with an 11.5-min time-scale. For this source, the emission size is estimated to be 1.39 × 1014 cm, the mass of the central black hole is estimated to be 107.87 M⊙ and the magnetic field strength is estimated to be 10.6 G.

  12. Simultaneous optical monitoring of BL Lacertae object S5 0716+714 with high temporal resolution

    NASA Astrophysics Data System (ADS)

    Man, Zhongyi; Zhang, Xiaoyuan; Wu, Jianghua; Yuan, Qirong

    2016-03-01

    We have monitored the BL Lacertae object S5 0716+714 simultaneously in the B, R and I bands on three nights in 2014 November. The average time resolution is quite high (73, 34 and 58 s for the filters B, R and I), which can help us trace the profile of the variation and search for the short inter-band time delay. Intra-day variability was about 0.1 mag on the first two nights and more than 0.3 mag on the third. A bluer-when-brighter colour behaviour was found. A clear loop path can be seen on the colour-magnitude diagram of the third night, revealing possible time delays between variations at high and low energies. It is the first time that the intra-day spectral hysteresis loop has been found so obviously in the optical band. We used the interpolated cross-correlation function method to further confirm the time delay and calculated the values of lag between light curves at different wavelengths on each night. On the third night, variations in the R and B bands are approximately 1.5 min lagging behind the I band. Such optical time delay is probably due to the interplay of different processes of electrons in the jet of the blazar.

  13. Finding the rarest objects in the universe: A new, efficient method for discovering BL Lacertae objects

    NASA Technical Reports Server (NTRS)

    Stocke, John; Perlman, Eric; Granados, Arno; Schachter, Jonathan; Elvis, Martin; Urry, Meg; Impey, Chris; Smith, Paul

    1993-01-01

    We present a new, efficient method for discovering new BL Lac Objects based upon the results of the Einstein Extended Medium Sensitivity Survey (EMSS). We have found that all x-ray selected BL Lacs are radio emitters, and further, that in a 'color-color' diagram (radio/optical and optical/x-ray) the BL Lac Objects occupy an area distinct from both radio loud quasars and the radio quiet QSOs and Seyferts which dominate x-ray selected samples. After obtaining radio counterparts via VLA 'snapshot' observations of a large sample of unidentified x-ray sources, the list of candidates is reduced. These candidates then can be confirmed with optical spectroscopy and/or polarimetry. Since greater than 70 percent of these sources are expected to be BL Lacs, the optical observations are very efficient. We have tested this method using unidentified sources found in the Einstein Slew Survey. The 162 Slew Survey x-ray source positions were observed with the VLA in a mixed B/C configuration at 6 cm resulting in 60 detections within 1.5 position error circle radii. These x-ray/optical/radio sources were then plotted, and 40 BL Lac candidates were identified. To date, 10 candidates have been spectroscopically observed resulting in 10 new BL Lac objects! Radio flux, optical magnitude, and polarization statistics (obtained in white light with the Steward Observatory 2.3 m CCD polarimeter) for each are given.

  14. Long-term observations of the blazar BL Lacertae

    NASA Astrophysics Data System (ADS)

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

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

  15. Six-year Optical Monitoring of the BL Lacertae Object 1ES 0806+52.4

    NASA Astrophysics Data System (ADS)

    Man, Zhongyi; Zhang, Xiaoyuan; Wu, Jianghua; Zhou, Xu; Yuan, Qirong

    2014-12-01

    We present the results of the first systematic long-term multicolor optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from 2005 December to 2011 February. The overall brightness of this object decreased from 2005 December to 2008 December but was regained after that. A sharp outburst probably occurred around the end of our monitoring program. Overlapping the long-term trend are some short-term small-amplitude oscillations. No intranight variability was found in the object, which is in accordance with the historical observations before 2005. By investigating the color behavior, we found a strong bluer-when-brighter chromatism for the long-term variability of 1ES 0806+52.4. The total amplitudes at the c, i, and o bands are 1.18, 1.12, and 1.02 mag, respectively. The amplitudes tend to increase toward shorter wavelengths, which may be a major cause of the bluer-when-brighter chromatism. Such bluer-when-brighter chromatisms are also found in other blazars, such as S5 0716+714, OJ 287. The hard-X-ray data collected from the Swift/BAT archive was correlated with our optical data. No positive result was found, the reason for which may be that the hard-X-ray flux is a combination of the synchrotron and inverse Compton emission, but with different timescales and cadences under the leptonic synchrotron self-Compton model.

  16. Six-year optical monitoring of the BL Lacertae object 1ES 0806+52.4

    SciTech Connect

    Man, Zhongyi; Zhang, Xiaoyuan; Wu, Jianghua; Zhou, Xu; Yuan, Qirong

    2014-12-01

    We present the results of the first systematic long-term multicolor optical monitoring of the BL Lacertae object 1ES 0806+52.4. The monitoring was performed in multiple passbands with a 60/90 cm Schmidt telescope from 2005 December to 2011 February. The overall brightness of this object decreased from 2005 December to 2008 December but was regained after that. A sharp outburst probably occurred around the end of our monitoring program. Overlapping the long-term trend are some short-term small-amplitude oscillations. No intranight variability was found in the object, which is in accordance with the historical observations before 2005. By investigating the color behavior, we found a strong bluer-when-brighter chromatism for the long-term variability of 1ES 0806+52.4. The total amplitudes at the c, i, and o bands are 1.18, 1.12, and 1.02 mag, respectively. The amplitudes tend to increase toward shorter wavelengths, which may be a major cause of the bluer-when-brighter chromatism. Such bluer-when-brighter chromatisms are also found in other blazars, such as S5 0716+714, OJ 287. The hard-X-ray data collected from the Swift/BAT archive was correlated with our optical data. No positive result was found, the reason for which may be that the hard-X-ray flux is a combination of the synchrotron and inverse Compton emission, but with different timescales and cadences under the leptonic synchrotron self-Compton model.

  17. Two New Bl-Lacertae Objects Discovered in the Error Boxes of Hard X-Ray Sources

    NASA Astrophysics Data System (ADS)

    Tagliaferri, G.; Giommi, P.; Beuermann, K.; Branduardi-Raymont, G.; Brissenden, R.; Mason, K. O.; Murdin, P.; Thomas, H.-C.; Tuohy, I.

    Two new BL Lacertae objects, located within the error boxes of hard X-ray sources, have been discovered during a systematic program to identify a large sample of EXOSAT serendipitous sources. Both hard X-ray sources were detected during the HEAD 1 whole sky survey and have been associated to a Seyfert galaxy and to a Be star. The EXOSAT data are consistent with the two BL Lacs being the only counterparts of the hard X-ray sources. If this is the case the space density of BL Lacs, at fluxes 3 x 10-11 erg cm -2 s -1 (2-10 keV), might be higher than previously thought. The implications for the shape on the X-ray LogN-LogS of BL Lac objects are briefly discussed.

  18. SEVEN-YEAR MULTI-COLOR OPTICAL MONITORING OF BL LACERTAE OBJECT S5 0716+714

    SciTech Connect

    Dai Yan; Wu Jianghua; Zhu Zonghong; Wang Lingzhi; Zhou Xu; Ma Jun; Yuan Qirong

    2013-02-15

    We have monitored the BL Lacertae object S5 0716+714 in five intermediate optical wavebands from 2004 September to 2011 April. Here, we present data that include 8661 measurements representing one of the largest databases obtained for an object in the optical domain. A simple analysis of the data indicates that the object was active most of the time, and intraday variability was frequently observed. In total, the object varied by 2.614 mag in the i band. Strong bluer-when-brighter chromatism was observed on long, intermediate, and short timescales.

  19. Host galaxy and environment of the BL Lacertae object PKS 0548-322: Observations with subarcsecond resolution

    NASA Technical Reports Server (NTRS)

    Falomo, Renato; Pesce, Joseph E.; Treves, Aldo

    1995-01-01

    We report on direct, subarcsecond resolution imaging of the nebulosity and spectroscopy of galaxies in the field of the BL Lacertae object PKS 0548-322. Surface photometry of the nebulosity is used to derive the properties of the host galaxy (M(sub V) = -23.4), which exhibits signs of interaction with a close companion galaxy at approximately 25 kpc. The radial brightness profile of the nebulosity is well fitted by the contribution of a bulge (r(exp 1/4)) plus a point source and a small internal disk. An analysis of the galaxies in the field shows that the source is located in a rich cluster of galaxies. Spectra of five galaxies in the field indicate that they are at the same redshift as the BL Lac object, thus supporting the imaging result of a surrounding cluster associated with the BL Lac. This cluster is most likely Abell S0549.

  20. 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

  1. Detection of the BL Lacertae Object H1426+428 at TeV Gamma-Ray Energies

    NASA Astrophysics Data System (ADS)

    Horan, D.; Badran, H. M.; Bond, I. H.; Bradbury, S. M.; Buckley, J. H.; Carson, M. J.; Carter-Lewis, D. A.; Catanese, M.; Cui, W.; Dunlea, S.; Das, D.; de la Calle Perez, I.; D'Vali, M.; Fegan, D. J.; Fegan, S. J.; Finley, J. P.; Gaidos, J. A.; Gibbs, K.; Gillanders, G. H.; Hall, T. A.; Hillas, A. M.; Holder, J.; Jordan, M.; Kertzman, M.; Kieda, D.; Kildea, J.; Knapp, J.; Kosack, K.; Krennrich, F.; Lang, M. J.; LeBohec, S.; Lessard, R.; Lloyd-Evans, J.; McKernan, B.; Moriarty, P.; Muller, D.; Ong, R.; Pallassini, R.; Petry, D.; Quinn, J.; Reay, N. W.; Reynolds, P. T.; Rose, H. J.; Sembroski, G. H.; Sidwell, R.; Stanton, N.; Swordy, S. P.; Vassiliev, V. V.; Wakely, S. P.; Weekes, T. C.

    2002-06-01

    A very high energy γ-ray signal has been detected at the 5.5 σ level from H1426+428, an X-ray-selected BL Lacertae object at a redshift of 0.129. The object was monitored from 1995 to 1998 with the Whipple 10 m imaging atmospheric Cerenkov telescope as part of a general blazar survey; the results of these observations, although not statistically significant, were consistently positive. X-ray observations of H1426+428 during 1999 with the BeppoSAX instrument revealed that the peak of its synchrotron spectrum occurs at greater than 100 keV, leading to the prediction of observable TeV emission from this object. H1426+428 was monitored extensively at the Whipple Observatory during the 1999, 2000, and 2001 observing seasons. The strongest TeV signals were detected in 2000 and 2001. During 2001, an integral flux of 2.04+/-0.35×10-11 cm-2 s-1 above 280 GeV was recorded from H1426+428. The detection of H1426+428 supports the idea that, as also seen in Mrk 501 and 1ES 2344+514, BL Lacertae objects with extremely high synchrotron peak frequencies produce γ-rays in the TeV range.

  2. Understanding BL Lacertae objects. Structural and kinematic mode changes in the BL Lac object PKS 0735+178

    NASA Astrophysics Data System (ADS)

    Britzen, S.; Witzel, A.; Gong, B. P.; Zhang, J. W.; Gopal-Krishna; Goyal, A.; Aller, M. F.; Aller, H. D.; Zensus, J. A.

    2010-06-01

    Context. We present evidence that parsec-scale jets in BL Lac objects may be significantly distinct in kinematics from their counterparts in quasars. We argued this previously for the BL lac sources 1803+784 and 0716+714 and report here a similar pattern for another well-known BL Lac object, PKS 0735+178, whose nuclear jet is found to exhibit kinematics atypical of quasars. Aims: By analyzing the pc-scale jet morphology and its changes in 0735+178 we seek to understand the emission processes in BL Lac objects and to decipher their differences from quasars. A detailed study of the jet components' motion reveals that the standard AGN paradigm of apparent superluminal motion does not always describe the kinematics in BL Lac objects. We study 0735+178 here to augment and improve the understanding of the peculiar motions in the jets of BL Lac objects as a class. Methods: We analyzed 15 GHz VLBA (Very Long Baseline Array) observations (2 cm/MOJAVE survey) performed at 23 epochs between 1995.27 and 2008.91. Multiple Gaussians were fitted to the derived VLBA data, to trace the kinematical and flux density evolution of the individual VLBI (Very Long Baseline Interferometry) components in the nuclear jet. We then compared the jet kinematics with the optical and radio light curves available for this BL Lac object and point out some striking correlations between the properties of the radio knots and the features in the light curves. Results: We found a drastic structural mode change in the VLBI jet of 0735+178, between 2000.4 and 2001.8 when its twice sharply bent trajectory turned into a linear shape. We further found that this jet had undergone a similar transition sometime between December 1981 and June 1983. A mode change, occurring in the reverse direction (between mid-1992 and mid-1995) has already been reported in the literature. These structural mode changes are found to be reflected in changed kinematical behavior of the nuclear jet, manifested as an apparent

  3. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects

    SciTech Connect

    Covino, S.; Baglio, M. C.; Foschini, L.; Sandrinelli, A.; Tavecchio, F.; Treves, A.; Zhang, H.; Barres de Almeida, U.; Bonnoli, G.; Böttcher, M.; Cecconi, M.; D’Ammando, F.; di Fabrizio, L.; Giarrusso, M.; Leone, F.; Lindfors, E.; Lorenzi, V.; Molinari, E.; Prandini, E.; Raiteri, C. M.

    2015-06-05

    Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysis of rapid variability of the total and polarized flux at optical wavelengths. Methods. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results. Our intense monitoring allowed us to draw strongly different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability on time-scales from hours to a few minutes and the latter practically constant in total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions. No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. As a

  4. Short timescale photometric and polarimetric behavior of two BL Lacertae type objects

    DOE PAGESBeta

    Covino, S.; Baglio, M. C.; Foschini, L.; Sandrinelli, A.; Tavecchio, F.; Treves, A.; Zhang, H.; Barres de Almeida, U.; Bonnoli, G.; Böttcher, M.; et al

    2015-06-05

    Context. Blazars are astrophysical sources whose emission is dominated by non-thermal processes, typically interpreted as synchrotron and inverse Compton emission. Although the general picture is rather robust and consistent with observations, many aspects are still unexplored. Aims. Polarimetric monitoring can offer a wealth of information about the physical processes in blazars. Models with largely different physical ingredients can often provide almost indistinguishable predictions for the total flux, but usually are characterized by markedly different polarization properties. We explore, with a pilot study, the possibility to derive structural information about the emitting regions of blazars by means of a joint analysismore » of rapid variability of the total and polarized flux at optical wavelengths. Methods. Short timescale (from tens of seconds to a couple of minutes) optical linear polarimetry and photometry for two blazars, BL Lacertae and PKS 1424+240, was carried out with the PAOLO polarimeter at the 3.6 m Telescopio Nazionale Galileo. Several hours of almost continuous observations were obtained for both sources. Results. Our intense monitoring allowed us to draw strongly different scenarios for BL Lacertae and PKS 1424+240, with the former characterized by intense variability on time-scales from hours to a few minutes and the latter practically constant in total flux. Essentially the same behavior is observed for the polarized flux and the position angle. The variability time-scales turned out to be as short as a few minutes, although involving only a few percent variation of the flux. The polarization variability time-scale is generally consistent with the total flux variability. Total and polarized flux appear to be essentially uncorrelated. However, even during our relatively short monitoring, different regimes can be singled out. Conclusions. No simple scenario is able to satisfactorily model the very rich phenomenology exhibited in our data. As

  5. High-resolution imaging of EINSTEIN Slew Survey BL Lacertae objects

    NASA Astrophysics Data System (ADS)

    Heidt, Jochen

    High-resolution images of 7 newly identified BL Lac objects (among them one BL Lac candidate) at z <= 0.2 from the Einstein Slew Survey are presented for the first time. In all cases we were able to resolve the host galaxy. Our 2-dimensional analysis of the host galaxies shows that all these BL Lac objects are embedded in elliptical galaxies with an average M_r = -23.1 and r_e = 10 kpc. One BL Lac might have both an bulge and an underlying disk. These results are similar to those obtained for the hosts of other BL Lac objects. The environments of the BL Lac objects are spectacular. In at least two (perhaps three) cases we found clear evidence for interaction. All BL Lac objects (except one) have at least 2 companions, some of which are bright, within a projected distance of 60 kpc from the BL Lac. In two cases we found 5 companions within 50 kpc. This implies that interaction is more related to the BL Lac phenomenon than previously assumed. One possible test for this scenario is briefly discussed.

  6. The Lack of Torus Emission from BL Lacertae Objects: An Infrared View of Unification with WISE

    NASA Astrophysics Data System (ADS)

    Plotkin, Richard M.; Anderson, Scott F.; Brandt, W. N.; Markoff, Sera; Shemmer, Ohad; Wu, Jianfeng

    2012-02-01

    We use data from the Wide-Field Infrared Survey Explorer (WISE) to perform a statistical study on the mid-infrared (IR) properties of a large number (~102) of BL Lac objects—low-luminosity active galactic nuclei (AGNs) with a jet beamed toward the Earth. As expected, many BL Lac objects are so highly beamed that their jet synchrotron emission dominates their IR spectral energy distributions. In other BL Lac objects, however, the jet is not strong enough to completely dilute the rest of the AGN emission. We do not see observational signatures of the dusty torus from these weakly beamed BL Lac objects. The lack of observable torus emission is consistent with suggestions that BL Lac objects are fed by radiatively inefficient accretion disks. Implications for the "nature versus nurture" debate for FR I and FR II radio galaxies are briefly discussed. Our study supports the notion that, beyond orientation, accretion rate plays an important role in AGN unification.

  7. The new BL Lacertae objects discovered by an efficient X-ray/radio/optical technique

    NASA Technical Reports Server (NTRS)

    Schachter, Jonathan F.; Stocke, John T.; Perlman, Eric; Elvis, Martin; Remillard, Ron; Granados, Arno; Luu, Jane; Huchra, John P.; Humphreys, Roberta; Urry, C. M.

    1993-01-01

    We report the recent discovery of ten BL Lac objects in the Einstein IPC Slew Survey by means of X-ray/radio versus X-ray/optical color-color diagrams and confirming optical spectroscopy. These ten BL Lac objects were discovered using a technique proposed by Stocke et al. (1989) which exploits the characteristic broad-band spectra of BL Lac objects. New VLA detections provide accurate fluxes (limiting f(6 cm) about 0.5 mJy) and about 1 arcsec positions, facilitating the determination of an optical counterpart. All ten new BL Lac objects show essentially featureless optical spectra and lie within the range of radio/X-ray/optical colors of known X-ray-selected BL Lac objects, when about 1 mag optical variability is included. We expect about 50 new BL Lac objects in total, from complete optical follow-up of our now completed VLA work and recent Australia Telescope observations, yielding a complete Slew Survey sample of about 90 BL Lac objects.

  8. Radio constraints on the nature of BL Lacertae objects and their parent population

    NASA Technical Reports Server (NTRS)

    Kollgaard, R. I.; Wardle, J. F. C.; Roberts, D. H.; Gabuzda, D. C.

    1992-01-01

    5 GHz VLA observations of 17 BL Lac objects with bright radio cores at both high and low resolution are reported. Extended emission is detected around most objects. None of the sources observed at low resolution show evidence of giant halos on the scale of tens of arcmin. In general, the sources with the most luminous extended emission exhibit FR II characteristics in both morphology and polarization, and less luminous sources exhibit FR I characteristics. Thus, the parent population of the BL Lac objects contains both FR I and FR II radio sources. No BL Lac objects are found that clearly exhibit quasarlike polarization at milliarcsec resolution. This argues against the view that the more luminous BL Lac objects are simply an extension of the quasar/OVV population, or that most BL Lac objects are gravitationally microlensed images of distant quasars. Other properties are generally consistent with the view the BL Lac objects are normal radio galaxies whose jets make a small angle to the line of sight.

  9. Thirteen new BL Lacertae objects discovered by an efficient x ray/radio/optical technique

    NASA Technical Reports Server (NTRS)

    Schachter, Jonathan F.; Stocke, John T.; Perlman, Eric; Elvis, Martin S.; Luu, Jane; Huchra, John P.; Humphreys, Roberta; Remillard, Ron; Wallin, John

    1992-01-01

    The discovery of 13 serendipitous BL Lac objects in the Einstein IPC Slew Survey by means of x ray/radio vs. x ray/optical color-color diagrams and confirmation by optical spectroscopy are reported. These 13 BL Lacs were discovered using a technique which exploits the characteristic broad band spectra of BL Lacs. New VLA detections provide accurate fluxes (f(6 cm) is approximately 0.5 mJy) and 2 in. positions, facilitating the determination of an optical counterpart. All 13 new BL Lacs show essentially featureless optical spectra. Nine of these lie within the range of colors of known x ray selected BL Lacs. Of the remaining four, one is apparently x ray louder (by a factor of 1.5) or optically quieter (by 0.8 mags); and three are optically louder (by 1-1.3 mags) than x ray selected BL Lacs. Approximately 50 new BL Lacs in total are expected from VLA work and upcoming Australia Telescope observations, yielding a complete Slew Survey sample of approximately 90 BL Lacs.

  10. THE LACK OF TORUS EMISSION FROM BL LACERTAE OBJECTS: AN INFRARED VIEW OF UNIFICATION WITH WISE

    SciTech Connect

    Plotkin, Richard M.; Markoff, Sera; Anderson, Scott F.; Brandt, W. N.; Wu Jianfeng; Shemmer, Ohad

    2012-02-15

    We use data from the Wide-Field Infrared Survey Explorer (WISE) to perform a statistical study on the mid-infrared (IR) properties of a large number ({approx}10{sup 2}) of BL Lac objects-low-luminosity active galactic nuclei (AGNs) with a jet beamed toward the Earth. As expected, many BL Lac objects are so highly beamed that their jet synchrotron emission dominates their IR spectral energy distributions. In other BL Lac objects, however, the jet is not strong enough to completely dilute the rest of the AGN emission. We do not see observational signatures of the dusty torus from these weakly beamed BL Lac objects. The lack of observable torus emission is consistent with suggestions that BL Lac objects are fed by radiatively inefficient accretion disks. Implications for the 'nature versus nurture' debate for FR I and FR II radio galaxies are briefly discussed. Our study supports the notion that, beyond orientation, accretion rate plays an important role in AGN unification.

  11. Radio outburst of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Buemi, C. S.; Leto, P.; Trigilio, C.; Umana, G.; Giroletti, M.; Orienti, M.; Raiteri, C. M.; Villata, M.; Bach, U.

    2013-04-01

    We report on extremely high radio flux of BL Lacertae at 43 and 8 GHz. Observations at 43 GHz with the 32 m radio telescope in Noto (Italy) revealed a flux density of 10.5 +/- 0.2 Jy on 2013 April 10.65, while observations at 8 GHz with the 32 m radio telescope in Medicina (Italy) detected a flux density of 8.2 +/- 0.7 Jy on April 12.22. These extremely high radio fluxes show that the radio activity likely correlated to the strong optical, near-infrared, and gamma-ray activity of 2011-2012 (see ATels #4028, #4031, #4155, #4271, #4277, #4349, #4565, #4600), and X-ray activity of late 2012 (ATels #4557, #4627), is far to be exhausted.

  12. Soft X-Ray Observations of a Complete Sample of X-Ray--selected BL Lacertae Objects

    NASA Astrophysics Data System (ADS)

    Perlman, Eric S.; Stocke, John T.; Wang, Q. Daniel; Morris, Simon L.

    1996-01-01

    We present the results of ROSAT PSPC observations of the X-ray selected BL Lacertae objects (XBLs) in the complete Einstein Extended Medium Sensitivity Survey (EM MS) sample. None of the objects is resolved in their respective PSPC images, but all are easily detected. All BL Lac objects in this sample are well-fitted by single power laws. Their X-ray spectra exhibit a variety of spectral slopes, with best-fit energy power-law spectral indices between α = 0.5-2.3. The PSPC spectra of this sample are slightly steeper than those typical of flat ratio-spectrum quasars. Because almost all of the individual PSPC spectral indices are equal to or slightly steeper than the overall optical to X-ray spectral indices for these same objects, we infer that BL Lac soft X-ray continua are dominated by steep-spectrum synchrotron radiation from a broad X-ray jet, rather than flat-spectrum inverse Compton radiation linked to the narrower radio/millimeter jet. The softness of the X-ray spectra of these XBLs revives the possibility proposed by Guilbert, Fabian, & McCray (1983) that BL Lac objects are lineless because the circumnuclear gas cannot be heated sufficiently to permit two stable gas phases, the cooler of which would comprise the broad emission-line clouds. Because unified schemes predict that hard self-Compton radiation is beamed only into a small solid angle in BL Lac objects, the steep-spectrum synchrotron tail controls the temperature of the circumnuclear gas at r ≤ 1018 cm and prevents broad-line cloud formation. We use these new ROSAT data to recalculate the X-ray luminosity function and cosmological evolution of the complete EMSS sample by determining accurate K-corrections for the sample and estimating the effects of variability and the possibility of incompleteness in the sample. Our analysis confirms that XBLs are evolving "negatively," opposite in sense to quasars, with Ve/Va = 0.331±0.060. The statistically significant difference between the values for

  13. RATAN-600 multi-frequency data for the BL Lacertae objects

    NASA Astrophysics Data System (ADS)

    Mingaliev, M. G.; Sotnikova, Yu. V.; Udovitskiy, R. Yu.; Mufakharov, T. V.; Nieppola, E.; Erkenov, A. K.

    2014-12-01

    Aims: We present a new catalogue of the RATAN-600 multi-frequency measurements for BL Lac objects. The purpose of this catalogue is to compile the BL Lac multi-frequency data that is acquired with the RATAN-600 simultaneously at several frequencies. The BL Lac objects emit a strongly variable and polarized non-thermal radiation across the entire electromagnetic spectrum from radio to γ rays and represent about 1% of known AGNs. They belong to the blazar population and differ from other blazars' featureless optical spectrum, which sometimes have absorption lines, or have weak and narrow emission lines. One of the most effective ways of studying the physics of BL Lacs is the use of simultaneous multi-frequency data. Methods: The multi-frequency broadband radio spectrum was obtained simultaneously with an accuracy of up to 1-2 min for four to six frequencies: 1.1, 2.3, 4.8, 7.7, 11.2, and 21.7 GHz. The catalogue is based on the RATAN-600 observations and on the data from: equatorial coordinate and redshift, R-band magnitude, synchrotron peak frequency, SED classes, and object type literature. Results: The present version of the catalogue contains RATAN-600 flux densities measurements over nine years (2006-2014), radio spectra at different epochs, and their parameters of the catalogue for more than 300 BL Lacs objects and candidates. The BL Lacs list is constantly updated with new observational data of RATAN-600. The catalogue is presented in interactive form and available at Special Astrophysical Observatory of the Russian Academy of Sciences website http://www.sao.ru/blcat/

  14. BROAD Ly{alpha} EMISSION FROM THREE NEARBY BL LACERTAE OBJECTS

    SciTech Connect

    Stocke, John T.; Danforth, Charles W.; Perlman, Eric S. E-mail: stocke@casa.colorado.edu

    2011-05-10

    We present far-UV HST/COS spectra of four nearby BL Lac objects. BL Lac spectra are dominated by a smooth, power-law continuum which arises in a relativistic jet. However, the spectra are not necessarily featureless; weak, broad- and/or narrow-line emission is sometimes seen in high-quality optical spectra. We present detections of Ly{alpha} emission in HST/COS spectra of Mrk 421 (z = 0.030) and PKS 2005-489 (z = 0.071) as well as an archival HST/GHRS observation of Mrk 501 (z = 0.0337). Archival HST/STIS observations of PKS 2155-304 (z = 0.116) show no Ly{alpha} emission to a very low upper limit. Using the assumption that the broad-line region (BLR) clouds are symmetrically placed around the active galactic nucleus (AGN), we use these measured Ly{alpha} emission features to constrain either the relativistic {Gamma} values for the ionizing continuum produced by the jet (in the ionization-bounded case) or the mass of warm gas (in the density-bounded case). While realistic {Gamma} values can be obtained for all four cases, the values for Mrk 421 and PKS 2155-304 are high enough to suggest that covering factors of BLR clouds of {approx}1%-2% might be required to provide consistency with earlier values of Doppler boosting and viewing angles suggested for this class of BL Lacs. This discrepancy also exists in the case of M 87, where the amount of Doppler boosting in our direction is expected to be minimal, again suggestive of a small covering factor of BLR clouds. If, as these small covering factors might suggest, the assumptions of a density-bounded model could be more correct, then the observed Ly{alpha} luminosities require that BL Lac/FR 1 nuclei possess very little warm gas (10{sup -4} to 10{sup -5} M{sub sun}) as suggested by Guilbert et al. If these clouds are in pressure balance with a hotter ({approx}10{sup 6} K) gas, the BLR contains too little mass to power the AGN by accretion alone.

  15. Optical-X-ray Observations of BL Lacertae Object AO 0235+164

    NASA Astrophysics Data System (ADS)

    Howard, Emily S.; Webb, James R.; Balonek, Thomas J.; McGrath, Elizabeth; Shrader, Chris R.

    1998-11-01

    The BL Lacertea object AO 0235+164 dramatically increased in brightness on October 20, 1997. This outburst was observed with the 1 meter SARA (Southeastern Association for Research in Astronomy) telescope located at Kitt Peak National Observatory (KPNO) located southwest of Tucson, Arizona. As a result of our observations, AO 0235+164 was also observed during the outbust by the Rossi X-ray Timing Experiment (RXTE) and Foggy Bottom Observaotry, Colgate Univserity, New York as a part of a Target of Opportunity (TOO) program. We present here the historical lightcurve of AO 0235+164, Optical observations during the ourtburst from the SARA and Foggy Bottom Observatories and X-ray observations from RXTE. Also, we present multifrequency data during this period and compare the variability of the Optical and X-ray bands.

  16. The collective emission of electromagnetic waves from astrophysical jets - Luminosity gaps, BL Lacertae objects, and efficient energy transport

    NASA Technical Reports Server (NTRS)

    Baker, D. N.; Borovsky, Joseph E.; Benford, Gregory; Eilek, Jean A.

    1988-01-01

    A model of the inner portions of astrophysical jets is constructed in which a relativistic electron beam is injected from the central engine into the jet plasma. This beam drives electrostatic plasma wave turbulence, which leads to the collective emission of electromagnetic waves. The emitted waves are beamed in the direction of the jet axis, so that end-on viewing of the jet yields an extremely bright source (BL Lacertae object). The relativistic electron beam may also drive long-wavelength electromagnetic plasma instabilities (firehose and Kelvin-Helmholtz) that jumble the jet magnetic field lines. After a sufficient distance from the core source, these instabilities will cause the beamed emission to point in random directions and the jet emission can then be observed from any direction relative to the jet axis. This combination of effects may lead to the gap turn-on of astrophysical jets. The collective emission model leads to different estimates for energy transport and the interpretation of radio spectra than the conventional incoherent synchrotron theory.

  17. Longterm optical monitoring of bright BL Lacertae objects with ATOM: Spectral variability and multiwavelength correlations

    NASA Astrophysics Data System (ADS)

    Wierzcholska, Alicja; Ostrowski, Michał; Stawarz, Łukasz; Wagner, Stefan; Hauser, Marcus

    2015-01-01

    Context. Blazars are the established sources of an intense and variable non-thermal radiation extending from radio wavelengths up to high and very high-energy γ-rays. Understanding the spectral evolution of blazars in selected frequency ranges, as well as multifrequency correlations in various types of blazar sources, is of a primary importance for constraining blazar physics. Aims: We present the results of a long-term optical monitoring of a sample of 30 blazars of the BL Lac type, most of which are the confirmed TeV emitters. We study the optical color-magnitude correlation patterns emerging in the analyzed sample and compare the optical properties of the targets with the high-energy γ-ray and high-frequency radio data. Methods: The optical observations were carried out in R and B filters using the Automatic Telescope for Optical Monitoring (ATOM) located at the site of the H.E.S.S. Array. Each object in the sample was observed during at least 20 nights in the period 2007 to 2012. Results: We find significant overall color-magnitude correlations (meaning bluer-when-brighter spectral evolution) in 40% of the sample. The sources that do not display any clear chromatism in the full datasets often do exhibit bluer-when-brighter behavior but only in isolated shorter time intervals. We also discovered spectral state transitions at optical wavelengths in several of the analyzed sources. Finally, we find that the radio, optical, and γ-ray luminosities of the sources in the sample obey almost linear correlations, which seem induced, at least partly, by the redshift dependence and may also be affected by the non-simultaneity of the analyzed multifrequency dataset. Conclusions: We argue that the observed bluer-when-brighter behavior is intrinsic to the jet-emission regions, at least for some of these blazars, rather than resulting from the contamination of the measured flux by the starlight of host galaxies. We also conclude that the significance of color

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

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Capetti, A.

    2016-03-01

    In a previous paper, we proposed a new method to select low-power BL Lacs (LPBLs) based on mid-infrared emission and flux contrast through the Ca II spectral break; that study led to the selection of a complete sample formed by 34 LPBLs with 0.05 BL Lacs. We find that the ratios between the X-ray and radio luminosities range from ~20 to ~30 000 and that the synchrotron peak frequencies span a wide energy interval, from log νpeak ~ 13.5 to ~20 [Hz]. This indicates a broad variety of SED shapes and a mixture of BL Lac flavors. Indeed, although the majority of our LPBLs are high-energy peaked BL Lacs (HBLs), we find that a quarter of them are low-energy peaked BL Lacs (LBLs), despite the fact that the sample is biased against the selection of LBLs. The analysis of the median LPBL SED confirms disagreement with the blazar sequence at low radio luminosities. Furthermore, if we limit the sample to the LBLs subsample, we find that their median SED shape is essentially indistinguishable from that of the most luminous BL Lacs. We conclude that the observed radio power is not the main driving parameter of the multiwavelength properties of BL Lacs.

  19. CATALOG AND STATISTICAL STUDY OF X-RAY SELECTED BL LACERTAE OBJECTS

    SciTech Connect

    Kapanadze, Bidzina Z.

    2013-02-01

    This paper presents a catalog of 312 X-ray selected BL Lacerate objects (XBLs), optically identified through the end of 2011. It contains the names from different surveys, equatorial coordinates, redshifts, multifrequency flux values, and luminosities for each source. In addition, the different characteristics of XBLs are statistically investigated (redshift, radio/optical/X-ray luminosities, central black hole (BH) mass, synchrotron peak frequency, broadband spectral indices, optical flux variability). Their values are collected through an extensive bibliographic and database search or calculated by us. The redshifts range from 0.031 to 0.702 with a maximum of the distribution at z = 0.223. The 1.4 GHz luminosities of XBLs log {nu}L{sub {nu}} {approx} 39-42 erg s{sup -1} while optical V and X-ray 0.1-2.4 keV bands show log {nu}L{sub {nu}} {approx} 43-46 erg s{sup -1}. The XBL hosts are elliptical galaxies with effective radii r{sub eff} = 3.2625.40 kpc and ellipticities, in = 0.040.52. Their R-band absolute magnitudes M{sub R} range from -21.11 mag to -24.86 mag with a mean value of -22.83 mag. The V - R indices of the hosts span from 0.61 to 1.52 and reveal a fourth-degree polynomial relationship with z that enables us to evaluate the redshifts of five sources whose V - R indices were determined from the observations but whose irredshifts values are either not found or not confirmed. The XBL nuclei show a wider range of 7.31 mag for M{sub R} with the highest luminosity corresponding to M{sub R} = -27.24 mag. The masses of central BHs are found in the interval log M{sub BH} = 7.39-9.30 solar masses (with distribution maximum at log M{sub BH}/M{sub Sun} = 8.30). The synchrotron peak frequencies are spread over the range log {nu}{sub peak} = 14.56-19.18 Hz with a peak of the distribution at log {nu}{sub peak} = 16.60 Hz. The broadband radio-to-optical ({alpha}{sub ro}), optical-to-X-ray ({alpha}{sub ox}), and radio-to-X-ray ({alpha}{sub rx}) spectral indices are

  20. ERRATIC JET WOBBLING IN THE BL LACERTAE OBJECT OJ287 REVEALED BY SIXTEEN YEARS OF 7 mm VLBA OBSERVATIONS

    SciTech Connect

    Agudo, Ivan; Gomez, Jose L.; Marscher, Alan P.; Jorstad, Svetlana G.; Perucho, Manel; Piner, B. Glenn; Rioja, Maria; Dodson, Richard

    2012-03-01

    We present the results from an ultra-high-resolution 7 mm Very Long Baseline Array study of the relativistic jet in the BL Lacertae object OJ287 from 1995 to 2011 containing 136 total intensity images. Analysis of the image sequence reveals a sharp jet-position-angle swing by >100 Degree-Sign during [2004,2006], as viewed in the plane of the sky, which we interpret as the crossing of the jet from one side of the line of sight to the other during a softer- and longer-term swing of the inner jet. Modulating such long-term swing, our images also show for the first time a prominent erratic wobbling behavior of the innermost {approx}0.4 mas of the jet with fluctuations in position angle of up to {approx}40 Degree-Sign over timescales {approx}2 yr. This is accompanied by highly superluminal motions along non-radial trajectories, which reflect the remarkable non-ballistic nature of the jet plasma on these scales. The erratic nature and short timescales of the observed behavior rule out scenarios such as binary black hole systems, accretion disk precession, and interaction with the ambient medium as possible origins of the phenomenon on the scales probed by our observations, although such processes may cause longer-term modulation of the jet direction. We propose that variable asymmetric injection of the jet flow, perhaps related to turbulence in the accretion disk, coupled with hydrodynamic instabilities leads to the non-ballistic dynamics that causes the observed non-periodic changes in the direction of the inner jet.

  1. Optical and radio behaviour of the BL Lacertae object 0716+714

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Villata, M.; Tosti, G.; Nesci, R.; Massaro, E.; Aller, M. F.; Aller, H. D.; Teräsranta, H.; Kurtanidze, O. M.; Nikolashvili, M. G.; Ibrahimov, M. A.; Papadakis, I. E.; Krichbaum, T. P.; Kraus, A.; Witzel, A.; Ungerechts, H.; Lisenfeld, U.; Bach, U.; Cimò, G.; Ciprini, S.; Fuhrmann, L.; Kimeridze, G. N.; Lanteri, L.; Maesano, M.; Montagni, F.; Nucciarelli, G.; Ostorero, L.

    2003-04-01

    Eight optical and four radio observatories have been intensively monitoring the BL Lac object 0716+714 in the last years: 4854 data points have been collected in the UBVRI bands since 1994, while radio light curves extend back to 1978. Many of these data, which all together constitute the widest optical and radio database available on this object, are presented here for the first time. Four major optical outbursts were observed at the beginning of 1995, in late 1997, at the end of 2000, and in fall 2001. In particular, an exceptional brightening of 2.3 mag in 9 days was detected in the R band just before the BeppoSAX pointing of October 30, 2000. A big radio outburst lasted from early 1998 to the end of 1999. The long-term trend shown by the optical light curves seems to vary with a characteristic time scale of about 3.3 years, while a longer period of 5.5-6 years seems to characterize the radio long-term variations. In general, optical colour indices are only weakly correlated with brightness; a clear spectral steepening trend was observed during at least one long-lasting dimming phase. Moreover, the optical spectrum became steeper after JD ˜ 2,451,000, the change occurring in the decaying phase of the late-1997 outburst. The radio flux behaviour at different frequencies is similar, but the flux variation amplitude decreases with increasing wavelength. The radio spectral index varies with brightness (harder when brighter), but the radio fluxes seem to be the sum of two different-spectrum contributions: a steady base level and a harder-spectrum variable component. Once the base level is removed, the radio variations appear as essentially achromatic, similarly to the optical behaviour. Flux variations at the higher radio frequencies lead the lower-frequency ones with week-month time scales. The behaviour of the optical and radio light curves is quite different, the broad radio outbursts not corresponding in time to the faster optical ones and the cross

  2. An active state of the BL Lacertae object Markarian 421 detected by INTEGRAL in April 2013

    NASA Astrophysics Data System (ADS)

    Pian, E.; Türler, M.; Fiocchi, M.; Boissay, R.; Bazzano, A.; Foschini, L.; Tavecchio, F.; Bianchin, V.; Castignani, G.; Ferrigno, C.; Raiteri, C. M.; Villata, M.; Beckmann, V.; D'Ammando, F.; Hudec, R.; Malaguti, G.; Maraschi, L.; Pursimo, T.; Romano, P.; Soldi, S.; Stamerra, A.; Treves, A.; Ubertini, P.; Vercellone, S.; Walter, R.

    2014-10-01

    Aims: Multiwavelength variability of blazars offers indirect, but very effective, insight into their powerful engines and on the mechanisms through which energy is propagated from the centre down the jet. The BL Lac object Mkn 421 is a TeV emitter, a bright blazar at all wavelengths, and therefore an excellent target for variability studies. Methods: We activated INTEGRAL observations of Mkn 421 in an active state on 16-21 April 2013, and complemented them with Fermi-LAT data. Results: We obtained well sampled optical, soft, and hard X-ray light curves that show the presence of two flares and time-resolved spectra in the 3.5-60 keV (JEM-X and IBIS/ISGRI) and 0.1-100 GeV (Fermi-LAT) ranges. The average flux in the 20-100 keV range is 9.1 × 10-11 erg s-1 cm-2 (~4.5 mCrab) and the nuclear average apparent magnitude, corrected for Galactic extinction, is V ≃ 12.2. In the time-resolved X-ray spectra, which are described by broken power laws and, marginally better, by log-parabolic laws, we see a hardening that correlates with flux increase, as expected in refreshed energy injections in a population of electrons that later cool via synchrotron radiation. The hardness ratios between the JEM-X fluxes in two different bands and between the JEM-X and IBIS/ISGRI fluxes confirm this trend. During the observation, the variability level increases monotonically from the optical to the hard X-rays, while the large LAT errors do not allow a significant assessment of the MeV-GeV variability. The cross-correlation analysis during the onset of the most prominent flare suggests a monotonically increasing delay of the lower frequency emission with respect to that at higher frequency, with a maximum time-lag of about 70 min, that is however not well constrained. The spectral energy distributions from the optical to the TeV domain were compared to homogeneous models of blazar emission based on synchrotron radiation and synchrotron self-Compton scattering. They represent a satisfactory

  3. Optical and radio brightening of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Ehgamberdiev, Sh. A.; Mirzaqulov, D. O.; Buemi, C. S.; Leto, P.; Trigilio, C.; Umana, G.; Raiteri, C. M.; Villata, M.; Bach, U.

    2012-07-01

    Optical observations at the Mount Maidanak Observatory in the framework of the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) reveal a rapid optical brightening of BL Lacertae. This is one of the 28 blazars for which the GASP performs a long-term, multiwavelength monitoring. The source brightness has recently increased from R = 13.66 +/- 0.01 on July 19.82 to R = 12.60 +/- 0.01 on July 22.97.

  4. Testing the Pairs-Reflection Model with X-Ray Spectral Variability and X-Ray Properties of Complete Samples of Radio-Selected BL Lacertae Objects

    NASA Astrophysics Data System (ADS)

    Urry, C. Megan

    1997-01-01

    This grant was awarded to Dr. C. Megan Urry of the Space Telescope Science Institute in response to two successful ADP proposals to use archival Ginga and Rosat X-ray data for 'Testing the Pairs-Reflection model with X-Ray Spectral Variability' (in collaboration with Paola Grandi, now at the University of Rome) and 'X-Ray Properties of Complete Samples of Radio-Selected BL Lacertae Objects' (in collaboration with then-graduate student Rita Sambruna, now a post-doc at Goddard Space Flight Center). In addition, post-docs Joseph Pesce and Elena Pian, and graduate student Matthew O'Dowd, have worked on several aspects of these projects. The grant was originally awarded on 3/01/94; this report covers the full period, through May 1997. We have completed our project on the X-ray properties of radio-selected BL Lacs.

  5. The noise of BL Lacertae

    NASA Technical Reports Server (NTRS)

    Moore, R. L.; Angel, J. R. P.; Duerr, R.; Lebofsky, M. J.; Wisniewski, W. Z.; Rieke, G. H.; Axon, D. J.; Bailey, J.; Hough, J. M.; Mcgraw, J. T.

    1982-01-01

    Results are presented from an intensive optical and IR monitoring program of the flux and polarization characteristics of BL Lac. It is found that the polarization variations increase in amplitude with increasing time interval, and that the path traced out by the polarization vector in the Q-U plane is a random walk. In view of earlier measurements of BL Lac, the polarization fluctuations can be represented at low frequencies by the flat power spectrum of white noise, up to a frequency of 0.05 cycles/day. Above this frequency, the spectrum steepens to that of a random walk. A model for BL Lac suggested by the polarimetric noise can be constructed from independent sources of light with randomly oriented, strong polarization. Small random differences in spectral index from source to source could also explain the variable wavelength dependence of polarization.

  6. Optical activity of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Larionov, V.; Blinov, D.; Konstantinova, T.

    2012-04-01

    We perform optical photometric and R-band polarimetric monitoring of BL Lac using 70-cm AZT-8 (CrAO, Ukraine) and 0.4-m LX-200 (St.Petersburg, Russia) telescopes, as a part of GASP project. As reported in Atel#4028, this blazar was found by Fermi LAT in active state on 2012 April 9. Our data show that a sharp optical maximum was reached on the date 2012-04-08UT02:20, R=13.10, while on 2012-04-11UT01:30 R=13.40.

  7. Long-term optical and radio variability of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Guo, Y. C.; Hu, S. M.; Xu, C.; Liu, C. Y.; Chen, X.; Guo, D. F.; Meng, F. Y.; Xu, M. T.; Xu, J. Q.

    2015-04-01

    Well-sampled optical and radio light curves of BL Lacertae in B, V, R, I bands and 4.8, 8.0, 14.5 GHz from 1968 to 2014 were presented in this paper. A possible 1.26 ± 0.05 yr period in optical bands and a 7.50 ± 0.15 yr period in radio bands were detected based on discrete correlation function, structure function as well as Jurkevich method. Correlations among different bands were also analyzed and no reliable time delay was found between optical bands. Very weak correlations were detected between V band and radio bands. However, in radio bands the variation at low frequency lagged that at high frequency obviously. The spectrum of BL Lacertae turned mildly bluer when the object turned brighter, and stronger bluer-when-brighter trends were found for short flares. A scenario including a precessing helical jet and periodic shocks was put forward to interpret the variation characteristics of BL Lacertae.

  8. BL Lacertae Objects Beyond Redshift 1.3 - UV-to-NIR Photometry and Photometric Redshift for Fermi/LAT Blazars

    NASA Technical Reports Server (NTRS)

    Rau, A.; Schady, P.; Greiner, J.; Salvato, M.; Ajello, M.; Bottacini, E.; Gehrels, N.; Afonso, P. M. J.; Elliott, J.; Filgas, R.; Kann, D. A.; Klose, S.; Kruehler, T.; Nardini, M.; Guelbenzu, A. Nicuesa; OlivaresE, F.; Rossi, A.; Sudilovsky. V.; Updike, A. C.; Hartmann, D. H.

    2011-01-01

    Context. Observations of the gamma-ray sky with Fermi led to significant advances towards understanding blazars, the most extreme class of Active Galactic Nuclei. A large fraction of the population detected by Fermi is formed by BL Lacertae (BL Lac) objects, whose sample has always suffered from a severe redshift incompleteness due to the quasi-featureless optical spectra. Aims. Our goal is to provide a significant increase of the number of confirmed high-redshift BL Lac objects contained in the 2 LAC Fermi/LAT catalog. Methods. For 103 Fermi/LAT blazars, photometric redshifts using spectral energy distribution fitting have been obtained. The photometry includes 13 broad-band filters from the far ultraviolet to the near-IR observed with Swift/UVOT and the multi-channel imager GROND at the MPG/ESO 2.2m telescope. Data have been taken quasi-simultaneously and the remaining source-intrinsic variability has been corrected for. Results. We release the UV-to-near-IR 13-band photometry for all 103 sources and provide redshift constraints for 75 sources without previously known redshift. Out of those, eight have reliable photometric redshifts at z > or approx. 1.3, while for the other 67 sources we provide upper limits. Six of the former eight are BL Lac objects, which quadruples the sample of confirmed high-redshift BL Lac. This includes three sources with redshifts higher than the previous record for BL Lac, including CRATES J0402-2615, with the best-fit solution at z approx. = 1.9.

  9. An HST/COS observation of broad Lyα emission and associated absorption lines of the BL Lacertae object H 2356-309

    SciTech Connect

    Fang, Taotao; Danforth, Charles W.; Stocke, John T.; Shull, J. Michael; Buote, David A.; Canizares, Claude R.; Gastaldello, Fabio

    2014-11-01

    Weak spectral features in BL Lacertae objects (BL Lacs) often provide a unique opportunity to probe the inner region of this rare type of active galactic nucleus. We present a Hubble Space Telescope/Cosmic Origins Spectrograph observation of the BL Lac H 2356-309. A weak Lyα emission line was detected. This is the fourth detection of a weak Lyα emission feature in the ultraviolet (UV) band in the so-called high-energy peaked BL Lacs, after Stocke et al. Assuming the line-emitting gas is located in the broad line region (BLR) and the ionizing source is the off-axis jet emission, we constrain the Lorentz factor (Γ) of the relativistic jet to be ≥8.1 with a maximum viewing angle of 3.°6. The derived Γ is somewhat larger than previous measurements of Γ ≈ 3-5, implying a covering factor of ∼3% of the line-emitting gas. Alternatively, the BLR clouds could be optically thin, in which case we constrain the BLR warm gas to be ∼10{sup –5} M {sub ☉}. We also detected two H I and one O VI absorption lines that are within |Δv| < 150 km s{sup –1} of the BL Lac object. The O VI and one of the H I absorbers likely coexist due to their nearly identical velocities. We discuss several ionization models and find a photoionization model where the ionizing photon source is the BL Lac object that can fit the observed ion column densities with reasonable physical parameters. This absorber can either be located in the interstellar medium of the host galaxy or in the BLR.

  10. Discovery of a new BL Lacertae object /1E 1402.3 + 0416/ with the Einstein Observatory

    NASA Technical Reports Server (NTRS)

    Stocke, J.; Liebert, J.; Stockman, H.; Danziger, J.; Lub, J.; Maccacaro, T.; Griffiths, R.; Giommi, P.

    1982-01-01

    It is noted that only one BL Lac object, designated 1E 1402.3 + 0416, has so far been discovered as part of an optical identification program for a complete sample of faint X-ray sources detected with the Einstein Observatory. Consistent with previously X-ray-discovered BL Lacs, this object is blue and radio weak (17 mJy at 6 cm). It is pointed out that the percentage of BL Lacs in the faint extragalactic X-ray sample (2%) is smaller than the percentage at higher X-ray fluxes (6%). Over the same range in X-ray flux, the percentage of emission-line active galaxy nuclei (QSO + Seyferts) rises from 40% to 74%). This is seen as suggesting that BL Lacs do not evolve in a manner similar to quasars and are, therefore, not substantial contributors to the X-ray background.

  11. Short and long term flux variability of the BL Lacertae object 1ES 2200+420, in the MeV - GeV range

    NASA Astrophysics Data System (ADS)

    Herath, Mahesh; Abeysekara, Anushka; Jayaratne, Chandana

    2016-03-01

    Blazars are a class of Active Galactic Nuclei (AGN) that exhibit variable flux states across the electromagnetic spectrum, from radio to TeV. Current measurements show that the MeV-GeV flux of a Blazar could have a variability time scale as small as few hours or as long as several months. In this talk I will report the MeV-GeV flux variability patterns of the BL Lacertae object (1ES 2200+420). The data has been obtained from the Fermi-LAT archival database, and analysed using the recently released Pass 8 Fermi Science Tools. The cross correlations between MeV-GeV flux and KeV flux observed by Swift-XRT will also be reported, which is an important measurement to constraint the Synchrotron models.

  12. Optical and radio variability of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Gaur, H.; Gupta, A. C.; Bachev, R.; Strigachev, A.; Semkov, E.; Wiita, P. J.; Volvach, A. E.; Gu, M. F.; Agarwal, A.; Agudo, I.; Aller, M. F.; Aller, H. D.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lähteenmäki, A.; Peneva, S.; Nikolashvili, M. G.; Sigua, L. A.; Tornikoski, M.; Volvach, L. N.

    2015-10-01

    Context. We extensively observed the prototype blazar, BL Lacertae, in optical and radio bands during an active phase in the period 2010-2013 when the source showed several prominent outbursts. We searched for possible correlations and time lags between the optical and radio band flux variations using multi-frequency data to learn about the mechanisms producing variability. Aims: During an active phase of BL Lacertae, we searched for possible correlations and time lags between multi-frequency light curves of several optical and radio bands. We tried to estimate any possible variability timescales and inter-band lags in these bands. Methods: We performed optical observations in B, V, R, and I-bands from seven telescopes in Bulgaria, Georgia, Greece, and India and obtained radio data at 36.8, 22.2, 14.5, 8, and 4.8 GHz frequencies from three telescopes in Crimea, Finland, and USA. Results: Significant cross-correlations between optical and radio bands are found in our observations with a delay of cm-fluxes with respect to optical bands of ~250 days. The optical and radio light curves do not show any significant timescales of variability. BL Lacertae showed many optical "mini-flares" on short timescales. Variations on longer term timescales are mildly chromatic with the superposition of many strong optical outbursts. In radio bands, the amplitude of variability is frequency dependent. Flux variations at higher radio frequencies lead the lower frequencies by days or weeks. Conclusions: The optical variations are consistent with being dominated by a geometric scenario where a region of emitting plasma moves along a helical path in a relativistic jet. The frequency dependence of the variability amplitude supports an origin of the observed variations intrinsic to the source. Tables of the light curves 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/582/A103

  13. DETECTION OF A TRANSIENT X-RAY ABSORPTION LINE INTRINSIC TO THE BL LACERTAE OBJECT H 2356-309

    SciTech Connect

    Fang Taotao; Buote, David A.; Humphrey, Philip J.; Canizares, Claude R.

    2011-04-10

    Since the launch of the Einstein X-ray Observatory in the 1970s, a number of broad absorption features have been reported in the X-ray spectra of BL Lac objects. These features are often interpreted as arising from high-velocity outflows intrinsic to the BL Lac object, therefore providing important information about the inner environment around the central engine. However, such absorption features have not been observed more recently with high-resolution X-ray telescopes such as Chandra and XMM-Newton. In this paper, we report the detection of a transient X-ray absorption feature intrinsic to the BL Lac object H 2356-309 with the Chandra X-ray Telescope. This BL Lac object was observed during XMM-Newton cycle 7 and Chandra cycles 8 and 10, as part of our campaign to investigate X-ray absorption produced by the warm-hot intergalactic medium residing in the foreground large-scale superstructure. During one of the 80 ks Chandra cycle 10 observations, a transient absorption feature was detected at 3.3{sigma} (or 99.9% confidence level, accounting for the number of 'trials), which we identify as the O VIII K{alpha} line produced by an absorber intrinsic to the BL Lac object. None of the other 11 observations showed this line. We constrain the ionization parameter (25 {approx}< {Xi} {approx}< 40) and temperature (10{sup 5} K

  14. Multifrequency-spectral behavior of the BL Lacertae objects OI 90.4 and 3C 66A

    NASA Technical Reports Server (NTRS)

    Worrall, D. M.; Rodriguez-Espinosa, J. M.; Puschell, J. J.; Bruhweiler, F. C.; Miller, H. R.; Aller, M. F.; Aller, H. D.

    1984-01-01

    Single-epoch multifrequency data for the BL Lac objects OI 90.4 and 3C 66A, spanning radio through ultraviolet wavelengths, are presented, as well as other measurements relevant to intensity and spectral-shape variability. Both BL Lac objects exhibit spectral curvature in the infrared-to-ultraviolet region, a properity that is inferred to be usual for this object class. Variability in the ultraviolet spectral index of OI 90.4 is found, whereas the spectral index of 3C 66A is the same in two observations 17 months apart. A synchrotron self-Compton jet model is applied to each BL Lac object. The OI 90.4 data are found to be best satisfied by a jet with a relatively high degree of relativistic beaming, but emission at frequencies below about 50 GHz is not described by the model. Furthermore, 3C 66A may not always undergo strong relativistic beaming, and the model may incorporate the small fraction of the total radio emission below about 20 GHz that is from within about 1.5 milliarcsec of the core.

  15. The X-ray spectra of the BL Lacertae objects PKS 0548 - 322 and 3C 66A

    NASA Technical Reports Server (NTRS)

    Maccacaro, T.; Maccagni, D.; Tarenghi, M.

    1983-01-01

    Einstein Observatory simultaneous imaging proportional counter and monitor proportional counter data are combined in order to derive the energy spectra of the BL Lac objects PKS 0548-322 and 3C 66A between 0.2 and 10 keV. While the latter is found to be variable in both intensity and spectral shape, the former, although constant in the present data, is found to have experienced a spectrum variation in view of results from other experiments. Attention is given to the implications of flux and spectral variability in BL Lac objects for models of X-ray emission mechanisms. It is suggested that the wide spread of the spectral index distribution is due to the detection of the highly variable synchrotron-produced X-rays that are generally undetected in QSOs.

  16. The jet of the BL Lacertae object PKS 0521-365 in the near-IR: MAD adaptive optics observations

    NASA Astrophysics Data System (ADS)

    Falomo, R.; Pian, E.; Treves, A.; Giovannini, G.; Venturi, T.; Moretti, A.; Arcidiacono, C.; Farinato, J.; Ragazzoni, R.; Diolaiti, E.; Lombini, M.; Tavecchio, F.; Brast, R.; Donaldson, R.; Kolb, J.; Marchetti, E.; Tordo, S.

    2009-07-01

    Context: BL Lac objects are low-power active nuclei exhibiting a variety of peculiar properties caused by the presence of a relativistic jet and orientation effects. Aims: We present adaptive optics near-IR images at high spatial resolution of the nearby BL Lac object PKS 0521-365, which is known to display a prominent jet both at radio and optical frequencies. Methods: The observations were obtained in Ks-band using the ESO multi-conjugated adaptive optics demonstrator at the Very Large Telescope. This allowed us to obtain images with 0.1 arcsec effective resolution. We performed a detailed analysis of the jet and its related features from the near-IR images, and combined them with images previously obtained with HST in the R band and by a re-analysis of VLA radio maps. Results: We find a remarkable similarity in the structure of the jet at radio, near-IR, and optical wavelengths. The broad-band emission of the jet knots is dominated by synchrotron radiation, while the nucleus also exhibits a significant inverse Compton component. We discovered the near-IR counterpart of the radio hotspot and found that the near-IR flux is consistent with being a synchrotron emission from radio to X-ray wavelengths. The bright red object (red-tip), detached but well aligned with the jet, is well resolved in the near-IR and has a linear light profile. Since it has no radio counterpart, we propose that it is a background galaxy not associated with the jet. Conclusions: The new adaptive optics near-IR images and previous observations at other frequencies allow us to study the complex environment around the remarkable BL Lac object PKS 0521-365. These data exemplify the capabilities of multi conjugate adaptive optics observations of extragalactic extended sources. Based on observations collected at ESO, Paranal, Chile, as part of MAD Guaranteed Time Observations.

  17. Near-infrared brightening of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Carnerero, M. I.; Gonzalez, A. I.; Pulido, J. A. Acosta; Raiteri, C. M.; Villata, M.

    2012-07-01

    Near-infrared observations at the Teide Observatory, in the framework of the GLAST-AGILE Support Program (GASP) of the Whole Earth Blazar Telescope (WEBT) confirm a rapid brightening of BL Lacertae, as reported by ATel#4271. Here we report on four observations obtained at the Carlos Sanchez Telescope in a week period, according to which the source has increased its brightness by 0.7 mag. On 2012 July 20.14 the source was observed at J=11.25 +/-0.01 (H=10.27+/-0.01 and Ks=9.46+/-0.01), on July 21.15 at J=11.00+/-0.02 (H=10.02+/-0.02, Ks=9.21+/-0,02), on July 24.98 at J=10.72+/-0.01 (H=9.76+/-0.01, Ks=8.94+/-0.01), and on July 26.12 at J=10.57+/-0.01 (H=9.58+/-0.01, Ks=8.77+/-0.01).

  18. Statistical Analysis on Temporal Properties of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Guo, Yu Cheng; Hu, Shao Ming; Li, Yu Tong; Chen, Xu

    2016-04-01

    A comprehensive temporal analysis has been performed on optical light curves of BL Lacertae in B, V and R bands. The light curves were denoised by Gaussian smoothing and decomposed into individual flares using an exponential profile. Asymmetry, duration, peak flux and equivalent energy output of flares were measured and the frequency distributions are presented. Most optical flares of BL Lacertae are highly symmetric, with a weak tendency towards gradual rises and rapid decays. The distribution of flare durations is not random but consistent with a gamma distribution. Peak fluxes and energy outputs of flares all follow lognormal distribution. A positive correlation is detected between flare durations and peak fluxes. The temporal properties of BL Lacertae provide evidence of the stochastic magnetohydrodynamic process in accretion disk and jet. Results presented here can serve as constraints on physical models attempting to interpreting blazar variations.

  19. Statistical analysis of the temporal properties of BL Lacertae

    NASA Astrophysics Data System (ADS)

    Guo, Yu Cheng; Hu, Shao Ming; Li, Yu Tong; Chen, Xu

    2016-08-01

    A comprehensive temporal analysis has been performed on optical light curves of BL Lacertae in the B, V and R bands. The light curves were denoised by Gaussian smoothing and decomposed into individual flares using an exponential profile. The asymmetry, duration, peak flux and equivalent energy output of flares were measured and the frequency distributions presented. Most optical flares of BL Lacertae are highly symmetric, with a weak tendency towards gradual rises and rapid decays. The distribution of flare durations is not random, but consistent with a gamma distribution. Peak fluxes and energy outputs of flares all follow a log-normal distribution. A positive correlation is detected between flare durations and peak fluxes. The temporal properties of BL Lacertae provide evidence of the stochastic magnetohydrodynamic process in the accretion disc and jet.The results presented here can serve as constraints on physical models attempting to interpret blazar variations.

  20. Discovery of hard-spectrum γ-ray emission from the BL Lacertae object 1ES 0414+009

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Barres de Almeida, U.; Becherini, Y.; Becker, J.; Behera, B.; Bernloehr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Buesching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Chounet, L.-M.; Clapson, A. C.; Coignet, G.; Cologna, G.; Conrad, J.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataie, A.; Domainko, W.; Drury, L. O'c.; Dubois, F.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Farnier, C.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Foerster, A.; Fuesling, M.; Gallant, Y. A.; Gast, H.; Gerard, L.; Gerbig, D.; Giebels, B.; Glicenstein, J. F.; Glueck, B.; Goret, P.; Goering, D.; Haeffner, S.; Hague, J. D.; Hampf, D.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hinton, J. A.; Hoffmann, A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzynski, K.; Katz, U.; Kaufmann, S.; Keogh, D.; Khangulyan, D.; Khelifi, B.; Klochkov, D.; Kluzniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Laffon, H.; Lamanna, G.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maurin, D.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Mehault, J.; Moderski, R.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Ona Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pedaletti, G.; Pelletier, G.; Petrucci, P.-O.; Pita, S.; Puehlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Rayner, S. M.; Reimer, A.; Reimer, O.; Renaud, M.; de Los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Ruppel, J.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schoeck, F. M.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Sikora, M.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, L.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Vialle, J. P.; Viana, A.; Vincent, P.; Voelk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S. L.; Costamante, L.; Fegan, S.; Ajello, M.

    2012-02-01

    Context. 1ES 0414 + 009 (z = 0.287) is a distant high-frequency-peaked BL Lac object, and has long been considered a likely emitter of very-high-energy (VHE, E > 100 GeV) γ-rays due to its high X-ray and radio flux. Aims: Observations in the VHE γ-ray band and across the electromagnetic spectrum can provide insights into the origin of highly energetic particles present in the source and the radiation processes at work. Because of the distance of the source, the γ-ray spectrum might provide further limits on the level of the extragalactic background light (EBL). Methods: We report observations made between October 2005 and December 2009 with H.E.S.S., an array of four imaging atmospheric Cherenkov telescopes. Observations at high energies (HE, 100 MeV-100 GeV) with the Fermi-LAT instrument in the first 20 months of its operation are also reported. To complete the multi-wavelength picture, archival UV and X-ray observations with the Swift satellite and optical observations with the ATOM telescope are also used. Results: Based on the observations with H.E.S.S., 1ES 0414 + 009 is detected for the first time in the VHE band. An excess of 224 events is measured, corresponding to a significance of 7.8σ. The photon spectrum of the source is well described by a power law, with photon index of ΓVHE = 3.45 ± 0.25stat ± 0.20syst. The integral flux above 200 GeV is (1.88 ± 0.20stat ± 0.38syst) × 10-12 cm-2 s-1. Observations with the Fermi-LAT in the first 20 months of operation show a flux between 200 MeV and 100 GeV of (2.3 ± 0.2stat) × 10-9 erg cm-2 s-1, and a spectrum well described by a power-law function with a photon index ΓHE = 1.85 ± 0.18. Swift/XRT observations show an X-ray flux between 2 and 10 keV of (0.8-1) × 10-11 erg cm-2 s-1, and a steep spectrum ΓX = (2.2-2.3). Combining X-ray with optical-UV data, a fit with a log-parabolic function locates the synchrotron peak around 0.1 keV. Conclusions: Although the GeV-TeV observations do not provide better

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

    NASA Astrophysics Data System (ADS)

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

    2012-06-01

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

  2. Discovery of high and very high-energy emission from the BL Lacertae object SHBL J001355.9-185406

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; O'C. Drury, L.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Gast, H.; Giebels, B.; Glicenstein, J. F.; Göring, D.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hague, J. D.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Nedbal, D.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spieß, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2013-06-01

    The detection of the high-frequency peaked BL Lac object (HBL) SHBL J001355.9-185406 (z = 0.095) at high (HE; 100 MeV < E < 300 GeV) and very high-energy (VHE; E > 100 GeV) with the Fermi Large Area Telescope (LAT) and the High Energy Stereoscopic System (H.E.S.S.) is reported. Dedicated observations were performed with the H.E.S.S. telescopes, leading to a detection at the 5.5σ significance level. The measured flux above 310 GeV is (8.3 ± 1.7stat ± 1.7sys) × 10-13 photons cm-2 s-1 (about 0.6% of that of the Crab Nebula), and the power-law spectrum has a photon index of Γ = 3.4 ± 0.5stat ± 0.2sys. Using 3.5 years of publicly available Fermi-LAT data, a faint counterpart has been detected in the LAT data at the 5.5σ significance level, with an integrated flux above 300 MeV of (9.3 ± 3.4stat ± 0.8sys) × 10-10 photons cm-2 s-1 and a photon index of Γ = 1.96 ± 0.20stat ± 0.08sys. X-ray observations with Swift-XRT allow the synchrotron peak energy in νFν representation to be located at ~1.0 keV. The broadband spectral energy distribution is modelled with a one-zone synchrotronself-Compton (SSC) model and the optical data by a black-body emission describing the thermal emission of the host galaxy. The derived parameters are typical of HBLs detected at VHE, with a particle-dominated jet.

  3. On the Location of the gamma-Ray Outburst Emission in the BL Lacertae Object AO 0235 + 164 Through Observations Across the Electromagnetic Spectrum

    NASA Technical Reports Server (NTRS)

    Agudo, Ivan; Marscher, Alan P.; Jorstad, Svetlana G.; Larionov, Valeri M.; Gomez, Jose L.; Laehteenmaeki, Anne; Smith, Paul S.; Nilsson, Kari; Readhead, Anthony C. S.; Aller, Margo F.; Heidt, Jochien; Gurwell, Mark; Thum, Clemens; Wehrle, Ann E.; Nikolashvili, Maria G.; Aller, Hugh D.; Benitez, Erika; Blinov, Dmitriy A.; Hagen-Thorn, Vladimir A.; Hiriart, David; Jannuzi, Buell T.; Joshi, Manasvita; Kimeridze, Givi N.; Kurtanidze, Omar M.; Kurtanidze, Sofia O.

    2011-01-01

    We present observations of a major outburst at centimeter, millimeter, optical, X-ray, and gamma-ray wavelengths of the BL Lacertae object AO 0235+164. We analyze the timing of multi-waveband variations in the flux and linear polarization, as well as changes in Very Long Baseline Array images at A = 7 mm with approx.0.15 milliarcsec resolution. The association of the events at different wavebands is confirmed at high statistical significance by probability arguments and Monte Carlo simulations. A series of sharp peaks in optical linear polarization, as well as a pronounced maximum in the 7 mm polarization of a superluminal jet knot, indicate rapid fluctuations in the degree of ordering of the magnetic field. These results lead us to conclude that the outburst occurred in the jet both in the quasi-stationary "core" and in the superluminal knot, both parsecs downstream of the supermassive black hole. We interpret the outburst as a consequence of the propagation of a disturbance, elongated along the line of sight by light-travel time delays, that passes through a standing recollimation shock in the core and propagates down the jet to create the superluminal knot. The multi-wavelength light curves vary together on long timescales (months/ years), but the correspondence is poorer on shorter timescales. This, as well as the variability of the polarization and the dual location of the outburst, agrees with the expectations of a multi-zone emission model in which turbulence plays a major role in modulating the synchrotron and inverse Compton fluxes.

  4. KEPLER OBSERVATIONS OF RAPID OPTICAL VARIABILITY IN THE BL LACERTAE OBJECT W2R1926+42

    SciTech Connect

    Edelson, R.; Mushotzky, R.; Vaughan, S.; Scargle, J.; Gandhi, P.; Malkan, M.; Baumgartner, W.

    2013-03-20

    We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with {approx}0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous {delta}I/I > 25% flares over timescales as short as a day. The flux distribution is highly skewed and non-Gaussian. The variability shows a strong rms-flux correlation with the clearest evidence to date for nonlinearity in this relation. We introduce a method to measure periodograms from the discrete autocorrelation function, an approach that may be well-suited to a wide range of Kepler data. The periodogram is not consistent with a simple power-law, but shows a flattening at frequencies below 7 Multiplication-Sign 10{sup -5} Hz. Simple models of the power spectrum, such as a broken power law, do not produce acceptable fits, indicating that the Kepler blazar light curve requires more sophisticated mathematical and physical descriptions than currently in use.

  5. The Evolving Radio Jet in BL Lacerta

    NASA Astrophysics Data System (ADS)

    Aller, H. D.; Hughes, P. A.; Aller, M. F.

    1994-05-01

    During the past 15 years, there have been at least ten outbursts at centimeter wavelengths in this extragalactic object. We describe here the flux density and linear polarization variations observed at 4.8, 8.0 and 14.5 GHz with the Michigan 26-meter telescope during the series of outbursts since 1987. The recent bursts are somewhat different from the highly polarized bursts in the early 1980s, which provided a successful quantitative test of a source model based on propagating transverse shocks in a relativistic jet. The most notable change is that the polarization position angle during polarized outbursts has increased by approximately 10 degrees. This is approximately the same shift as found in a comparison of VLBI maps taken during the same time periods by Mutel, Denn and Dryer (1994, NRAO Workshop on Compact Extragalactic Radio Sources, ed. Zensus and Kellermann, p. 191), and supports their conclusion that the orientation of the radio emitting jet in BL Lac has changed over time. Our preliminary analysis further suggests that a simple scaling of the physical parameters which gave quantitatively good fits to both the 1982 and 1983 bursts will not accurately describe the recent, relatively isolated, burst in 1991. We also note that while some bursts (e.g. in 1982, 1983 and 1991) exhibit degrees of linear polarization in excess of ten percent, other bursts (e.g. in 1980 and 1990) exhibit a very low degree of linear polarization. A common characteristic of the low polarization events is that they all exhibit high internal synchrotron self absorption (as indicated by the flux density spectra of the outbursts). This research has been supported in part by NSF grant AST-9120224.

  6. Detection of high-energy gamma-ray emission from the BL Lacertae object Markarian 421 by the Egret telescope on the Compton Observatory

    NASA Technical Reports Server (NTRS)

    Lin, Y. C.; Bertsch, D. L.; Chiang, J.; Fichtel, C. E.; Hartman, R. C.; Hunter, S. D.; Kanbach, G.; Kniffen, D. A.; Kwok, P. W.; Mattox, J. R.

    1992-01-01

    Gamma radiation in the energy range from 50 MeV to well over 1 GeV has been observed from the direction of the BL Lac object Markarian 421 by the Energetic Gamma Ray Experiment Telescope on the Compton Observatory during the period 1991 June 27-July 11. The source flux is weak, but still statistically significant at the level of 10 exp -5; the integrated photon flux above 100 MeV is (1.4 +/- 0.3) x 10 exp -7/sq cm s. The differential photon energy spectrum can be represented by a power law with exponent 1.96 +/- 0.14. This is the first detection of gamma-ray emission from a BL Lac object.

  7. Rapid millimeter and centimeter band flux density increase in the gamma-ray blazar BL Lacertae

    NASA Astrophysics Data System (ADS)

    Hovatta, Talvikki; Richards, Joseph L.; Max-Moerbeck, Walter; Pearson, Timothy J.; Readhead, Anthony C. S.

    2012-11-01

    We have observed a rapid flux density increase of BL Lacertae (2200+420) at 15 GHz (2 cm) and 95 GHz (3 mm) following the report on highest millimeter flux density ever observed at the SMA (ATel #4557). Since 2009, BL Lacertae has been observed approximately twice per week at 15 GHz with the Owens Valley Radio Observatory (OVRO) 40m Telescope as part of our gamma-ray blazar monitoring program (Richards et al....

  8. HIGH-FREQUENCY-PEAKED BL LACERTAE OBJECTS AS SPECTRAL CANDLES TO MEASURE THE EXTRAGALACTIC BACKGROUND LIGHT IN THE FERMI AND AIR CHERENKOV TELESCOPES ERA

    SciTech Connect

    Mankuzhiyil, Nijil; Persic, Massimo; Tavecchio, Fabrizio

    2010-05-20

    The extragalactic background light (EBL) is the integrated light from all the stars that have ever formed, and spans the IR-UV range. The interaction of very high-energy (VHE: E > 100 GeV) {gamma}-rays, emitted by sources located at cosmological distances, with the intervening EBL results in e {sup -} e {sup +} pair production that leads to energy-dependent attenuation of the observed VHE flux. This introduces a fundamental ambiguity into the interpretation of measured VHE {gamma}-ray spectra: neither the intrinsic spectrum nor the EBL are separately known-only their combination is. In this Letter, we propose a method to measure the EBL photon number density. It relies on using simultaneous observations of BL Lac objects in the optical, X-ray, high-energy (HE: E > 100 MeV) {gamma}-ray (from the Fermi telescope), and VHE {gamma}-ray (from Cherenkov telescopes) bands. For each source, the method involves best-fitting the spectral energy distribution from optical through HE {gamma}-rays (the latter being largely unaffected by EBL attenuation as long as z {approx_lt} 1) with a synchrotron self-Compton model. We extrapolate such best-fitting models into the VHE regime and assume they represent the BL Lacs' intrinsic emission. Contrasting measured versus intrinsic emission leads to a determination of the {gamma}{gamma} opacity to VHE photons. Using, for each given source, different states of emission will only improve the accuracy of the proposed method. We demonstrate this method using recent simultaneous multifrequency observations of the high-frequency-peaked BL Lac object PKS 2155-304 and discuss how similar observations can more accurately probe the EBL.

  9. High-frequency-peaked BL Lacertae Objects as Spectral Candles to Measure the Extragalactic Background Light in the Fermi and Air Cherenkov Telescopes Era

    NASA Astrophysics Data System (ADS)

    Mankuzhiyil, Nijil; Persic, Massimo; Tavecchio, Fabrizio

    2010-05-01

    The extragalactic background light (EBL) is the integrated light from all the stars that have ever formed, and spans the IR-UV range. The interaction of very high-energy (VHE: E > 100 GeV) γ-rays, emitted by sources located at cosmological distances, with the intervening EBL results in e - e + pair production that leads to energy-dependent attenuation of the observed VHE flux. This introduces a fundamental ambiguity into the interpretation of measured VHE γ-ray spectra: neither the intrinsic spectrum nor the EBL are separately known—only their combination is. In this Letter, we propose a method to measure the EBL photon number density. It relies on using simultaneous observations of BL Lac objects in the optical, X-ray, high-energy (HE: E > 100 MeV) γ-ray (from the Fermi telescope), and VHE γ-ray (from Cherenkov telescopes) bands. For each source, the method involves best-fitting the spectral energy distribution from optical through HE γ-rays (the latter being largely unaffected by EBL attenuation as long as z <~ 1) with a synchrotron self-Compton model. We extrapolate such best-fitting models into the VHE regime and assume they represent the BL Lacs' intrinsic emission. Contrasting measured versus intrinsic emission leads to a determination of the γγ opacity to VHE photons. Using, for each given source, different states of emission will only improve the accuracy of the proposed method. We demonstrate this method using recent simultaneous multifrequency observations of the high-frequency-peaked BL Lac object PKS 2155-304 and discuss how similar observations can more accurately probe the EBL.

  10. Soft X-ray spectrum of BL Lacertae object AO 0235+164 as a tracer of elemental abundances at z approximately 0.5

    NASA Technical Reports Server (NTRS)

    Madejski, Greg

    1994-01-01

    We report the soft X-ray spectrum of BL Lac object AO 0235+164, observed with the Einstein Observatory Imaging Proportional Counter (IPC). This object (z = 0.94) has an intervening galaxy (or a protogalactic disk) at z = 0.524 present in the line of sight, producing both radio and optical absorption lines in the background BL Lac continuum. The X-ray spectrum exhibits a substantial soft X-ray cutoff, corresponding to several times that expected from our own Galaxy; we interpret that excess cutoff as due to the intervening galaxy. The comparison of the hydrogen column density inferred from the 21 cm radio data and the X-ray absorption allows, in principle, the determination of the elemental abundances in the intervening galaxy. However, the uncertainties in both the H I spin temperature and X-ray spectral parameters only loosely restrict these abundances to be 2 +/- 1 solar, which even at the lower limit appears higher than that inferred from studies of samples of optical absoprtion-line systems.

  11. SIMULTANEOUS B'V'R' MONITORING OF BL LACERTAE OBJECT S5 0716+714 AND DETECTION OF INTER-BAND TIME DELAY

    SciTech Connect

    Wu Jianghua; He Xiangtao; Boettcher, Markus; Zhou Xu; Ma Jun; Jiang Zhaoji

    2012-05-15

    We present the results of our optical monitoring of the BL Lac object S5 0716+714 over seven nights in 2006 December. The monitoring was carried out simultaneously at three optical wavelengths with a novel photometric system. The object did not show large-amplitude internight variations during this period. Intranight variations were observed on four nights and probably on one more. Strong bluer-when-brighter chromatism was detected on both intranight and internight timescales. The intranight variation amplitude decreases in the wavelength sequence of B', R', and V'. Cross-correlation analyses revealed that the variability at the B' and V' bands leads that at the R' band by about 30 minutes on one night.

  12. X-ray spectral evolution of TeV BL Lacertae objects: eleven years of observations with BeppoSAX, XMM-Newton and Swift satellites

    NASA Astrophysics Data System (ADS)

    Massaro, F.; Tramacere, A.; Cavaliere, A.; Perri, M.; Giommi, P.

    2008-02-01

    Context: Many of the extragalactic sources detected in γ rays at TeV energies are BL Lac objects. In particular, they belong to the subclass of “high frequency peaked BL Lacs” (HBLs), as their spectral energy distributions exhibit a first peak in the X-ray band. At a closer look, their X-ray spectra appear to be generally curved into a log-parabolic shape. In a previous investigation of Mrk 421, two correlations were found between the spectral parameters. One involves the height Sp increasing with the position Ep of the first peak; this was interpreted as a signature of synchrotron emission from relativistic electrons. The other involves the curvature parameter b decreasing as Ep increases; this points toward statistical/stochastic acceleration processes for the emitting electrons. Aims: We analyse X-ray spectra of several TeV HBLs to pinpoint their behaviours in the E_p-Sp and E_p-b planes and to compare them with Mrk 421. Methods: We perfom X-ray spectral analyses of a sample of 15 BL Lacs. We report the whole set of observations obtained with the BeppoSAX, XMM-Newton and Swift satellites between 29/06/96 and 07/04/07. We focus on five sources (PKS 0548-322, 1H 1426+418, Mrk 501, 1ES 1959+650, PKS 2155-304) whose X-ray observations warrant detailed searching of correlations or trends. Results: Within our database, we find that four out of five sources, namely PKS 0548-322, 1H 1426+418, Mrk 501 and 1ES 1959+650, follow similar trends as Mrk 421 in the E_p-Sp plane, while PKS 2155-304 differs. As for the E_p-b plane, all TeV HBLs follow a similar behaviour. Conclusions: The trends exhibited by Mrk 421 appear to be shared by several TeV HBLs, such as to warrant discussing predictions from the X-ray spectral evolution to that of TeV emissions. Appendix A is only available in electronic form at http://www.aanda.org

  13. The optical-gamma correlation in BL Lacertae

    NASA Astrophysics Data System (ADS)

    Raiteri, Claudia M.; Villata, Massimo; D'Ammando, Filippo; Larionov, Valeri M.; Gurwell, Mark A.; Mirzaqulov, Davron O.; Smith, Paul S.; Carnerero, Maria Isabel

    2013-12-01

    We present multifrequency light curves of BL Lacertae from February 2008 to October 2012. Lowenergy data (optical and millimetre) were acquired in the framework of a GASP-WEBT project. High-energy data (ultraviolet, X-ray, and γ-ray) come from observations of the Swift, RXTE, and Fermi satellites. After a period of moderate activity, in May 2011 the source suddenly started to flare at γ and optical-UV frequencies. Activity at millimetre wavelengths and X rays began 3-4 months later. This behaviour offered a good opportunity to study the correlation among flux variability in different bands, in particular between the best-sampled optical and γ-ray light curves. However, even in this fortuitous case, we can only define a general correlation with likely no time lag, but with a lag uncertainty of ±1 day. Indeed, the data reveal a complex relationship between the γ and optical fluxes, which cannot be unveiled because of the small gaps in the sampling of this extremely variable source.

  14. Discovery of very high energy γ-ray emission from the BL Lacertae object PKS 0301-243 with H.E.S.S.

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Ait Benkhali, F.; Akhperjanian, A. G.; Angüner, E.; Anton, G.; Balenderan, S.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker Tjus, J.; Bernlöhr, K.; Birsin, E.; Bissaldi, E.; Biteau, J.; Böttcher, M.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Chalme-Calvet, R.; Chaves, R. C. G.; Cheesebrough, A.; Chrétien, M.; Colafrancesco, S.; Cologna, G.; Conrad, J.; Couturier, C.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; deWilt, P.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Edwards, T.; Egberts, K.; Eger, P.; Espigat, P.; Farnier, C.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fernandez, D.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gajdus, M.; Gallant, Y. A.; Garrigoux, T.; Giebels, B.; Glicenstein, J. F.; Grondin, M.-H.; Grudzińska, M.; Häffner, S.; Hague, J. D.; Hahn, J.; Harris, J.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hervet, O.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; Jahn, C.; Jamrozy, M.; Janiak, M.; Jankowsky, F.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Khélifi, B.; Kieffer, M.; Klepser, S.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Kolitzus, D.; Komin, Nu.; Kosack, K.; Krakau, S.; Krayzel, F.; Krüger, P. P.; Laffon, H.; Lamanna, G.; Lefaucheur, J.; Lemoine-Goumard, M.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Marx, R.; Maurin, G.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Menzler, U.; Meyer, M.; Moderski, R.; Mohamed, M.; Moulin, E.; Murach, T.; Naumann, C. L.; de Naurois, M.; Nedbal, D.; Niemiec, J.; Nolan, S. J.; Oakes, L.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Parsons, R. D.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Poon, H.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raab, S.; Raue, M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schüssler, F.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sol, H.; Spengler, G.; Spies, F.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Trichard, C.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorster, M.; Wagner, S. J.; Wagner, P.; Ward, M.; Weidinger, M.; Weitzel, Q.; White, R.; Wierzcholska, A.; Willmann, P.; Wörnlein, A.; Wouters, D.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2013-11-01

    The active galactic nucleus PKS 0301-243 (z = 0.266) is a high-synchrotron-peaked BL Lac object that is detected at high energies (HE, 100 MeV 100 GeV) by the High Energy Stereoscopic System (H.E.S.S.) from observations between September 2009 and December 2011 for a total live time of 34.9 h. Gamma rays above 200 GeV are detected at a significance of 9.4σ. A hint of variability at the 2.5σ level is found. An integral flux I(E > 200 GeV) = (3.3 ± 1.1stat ± 0.7syst) × 10-12 ph cm-2 s-1 and a photon index Γ = 4.6 ± 0.7stat ± 0.2syst are measured. Multi-wavelength light curves in HE, X-ray and optical bands show strong variability, and a minimal variability timescale of eight days is estimated from the optical light curve. A single-zone leptonic synchrotron self-Compton scenario satisfactorily reproduces the multi-wavelength data. In this model, the emitting region is out of equipartition and the jet is particle dominated. Because of its high redshift compared to other sources observed at TeV energies, the very high energy emission from PKS 0301-243 is attenuated by the extragalactic background light (EBL) and the measured spectrum is used to derive an upper limit on the opacity of the EBL.

  15. Discovery of VHE γ-ray emission and multi-wavelength observations of the BL Lacertae object 1RXS J101015.9-311909

    NASA Astrophysics Data System (ADS)

    H.E.S.S. Collaboration; Abramowski, A.; Acero, F.; Aharonian, F.; Akhperjanian, A. G.; Anton, G.; Balzer, A.; Barnacka, A.; Becherini, Y.; Becker, J.; Bernlöhr, K.; Birsin, E.; Biteau, J.; Bochow, A.; Boisson, C.; Bolmont, J.; Bordas, P.; Brucker, J.; Brun, F.; Brun, P.; Bulik, T.; Büsching, I.; Carrigan, S.; Casanova, S.; Cerruti, M.; Chadwick, P. M.; Charbonnier, A.; Chaves, R. C. G.; Cheesebrough, A.; Cologna, G.; Conrad, J.; Dalton, M.; Daniel, M. K.; Davids, I. D.; Degrange, B.; Deil, C.; Dickinson, H. J.; Djannati-Ataï, A.; Domainko, W.; Drury, L. O'C.; Dubus, G.; Dutson, K.; Dyks, J.; Dyrda, M.; Egberts, K.; Eger, P.; Espigat, P.; Fallon, L.; Fegan, S.; Feinstein, F.; Fernandes, M. V.; Fiasson, A.; Fontaine, G.; Förster, A.; Füßling, M.; Gallant, Y. A.; Gast, H.; Gérard, L.; Gerbig, D.; Giebels, B.; Glicenstein, J. F.; Glück, B.; Göring, D.; Häffner, S.; Hague, J. D.; Hahn, J.; Hampf, D.; Harris, J.; Hauser, M.; Heinz, S.; Heinzelmann, G.; Henri, G.; Hermann, G.; Hillert, A.; Hinton, J. A.; Hofmann, W.; Hofverberg, P.; Holler, M.; Horns, D.; Jacholkowska, A.; de Jager, O. C.; Jahn, C.; Jamrozy, M.; Jung, I.; Kastendieck, M. A.; Katarzyński, K.; Katz, U.; Kaufmann, S.; Keogh, D.; Khélifi, B.; Klochkov, D.; Kluźniak, W.; Kneiske, T.; Komin, Nu.; Kosack, K.; Kossakowski, R.; Krayzel, F.; Laffon, H.; Lamanna, G.; Lenain, J.-P.; Lennarz, D.; Lohse, T.; Lopatin, A.; Lu, C.-C.; Marandon, V.; Marcowith, A.; Masbou, J.; Maxted, N.; Mayer, M.; McComb, T. J. L.; Medina, M. C.; Méhault, J.; Moderski, R.; Mohamed, M.; Moulin, E.; Naumann, C. L.; Naumann-Godo, M.; de Naurois, M.; Nedbal, D.; Nekrassov, D.; Nguyen, N.; Nicholas, B.; Niemiec, J.; Nolan, S. J.; Ohm, S.; de Oña Wilhelmi, E.; Opitz, B.; Ostrowski, M.; Oya, I.; Panter, M.; Paz Arribas, M.; Pekeur, N. W.; Pelletier, G.; Perez, J.; Petrucci, P.-O.; Peyaud, B.; Pita, S.; Pühlhofer, G.; Punch, M.; Quirrenbach, A.; Raue, M.; Rayner, S. M.; Reimer, A.; Reimer, O.; Renaud, M.; de los Reyes, R.; Rieger, F.; Ripken, J.; Rob, L.; Rosier-Lees, S.; Rowell, G.; Rudak, B.; Rulten, C. B.; Sahakian, V.; Sanchez, D. A.; Santangelo, A.; Schlickeiser, R.; Schulz, A.; Schwanke, U.; Schwarzburg, S.; Schwemmer, S.; Sheidaei, F.; Skilton, J. L.; Sol, H.; Spengler, G.; Stawarz, Ł.; Steenkamp, R.; Stegmann, C.; Stinzing, F.; Stycz, K.; Sushch, I.; Szostek, A.; Tavernet, J.-P.; Terrier, R.; Tluczykont, M.; Valerius, K.; van Eldik, C.; Vasileiadis, G.; Venter, C.; Viana, A.; Vincent, P.; Völk, H. J.; Volpe, F.; Vorobiov, S.; Vorster, M.; Wagner, S. J.; Ward, M.; White, R.; Wierzcholska, A.; Zacharias, M.; Zajczyk, A.; Zdziarski, A. A.; Zech, A.; Zechlin, H.-S.

    2012-06-01

    1RXS J101015.9-311909 is a galaxy located at a redshift of z=0.14 hosting an active nucleus (called AGN) belonging to the class of bright BL Lac objects. Observations at high (HE, E > 100 MeV) and very high (VHE, E > 100 GeV) energies provide insights into the origin of very energetic particles present in such sources and the radiation processes at work. We report on results from VHE observations performed between 2006 and 2010 with the H.E.S.S. instrument, an array of four imaging atmospheric Cherenkov telescopes. H.E.S.S. data have been analysed with enhanced analysis methods, making the detection of faint sources more significant. VHE emission at a position coincident with 1RXS J101015.9-311909 is detected with H.E.S.S. for the first time. In a total good-quality livetime of about 49 h, we measure 263 excess counts, corresponding to a significance of 7.1 standard deviations. The photon spectrum above 0.2 TeV can be described by a power-law with a photon index of Γ = 3.08 ± 0.42stat ± 0.20sys. The integral flux above 0.2 TeV is about 0.8% of the flux of the Crab nebula and shows no significant variability over the time reported. In addition, public Fermi/LAT data are analysed to search for high energy emission from the source. The Fermi/LAT HE emission in the 100 MeV to 200 GeV energy range is significant at 8.3 standard deviations in the chosen 25-month dataset. UV and X-ray contemporaneous observations with the Swift satellite in May 2007 are also reported, together with optical observations performed with the atom telescope located at the H.E.S.S. site. Swift observations reveal an absorbed X-ray flux of F(0.3-7) keV = 1.04+0.04-0.05 × 10-11 erg cm-2 s-1 in the 0.3-7 keV range. Finally, all the available data are used to study the multi-wavelength properties of the source. The spectral energy distribution (SED) can be reproduced using a simple one-zone Synchrotron Self Compton (SSC) model with emission from a region with a Doppler factor of 30 and a

  16. Non-radial motion in the TeV blazar S5 0716+714. The pc-scale kinematics of a BL Lacertae object

    NASA Astrophysics Data System (ADS)

    Britzen, S.; Kam, V. A.; Witzel, A.; Agudo, I.; Aller, M. F.; Aller, H. D.; Karouzos, M.; Eckart, A.; Zensus, J. A.

    2009-12-01

    Context: Flat-spectrum radio sources often show a core-jet structure on pc-scales. Individual jet components reveal predominantly outward directed motion. For the BL Lac object S5 0716+714 conflicting apparent velocities have been reported in the literature. This object is an intra-day variable source and suited to investigate a possible correlation between kinematic properties and flux-density variability on different timescales. Aims: We study the kinematics in the pc-scale jet of S5 0716+714 to determine the apparent speeds of the jet components based on a much improved data set. In addition, we search for correlations between the radio flux-density light curves and the morphological changes detected along the VLBI jet. Methods: We (re-)analyze 50 VLBI observations obtained with the VLBA at 5 different frequencies (5-43 GHz) between 1992.73 and 2006.32. The data have been parameterized using circular Gaussian components. We analyze the jet component motion in detail taking care not only to account for motion in the radial but also in the orthogonal direction. We study the evolution of the jet ridge line and investigate the spectral properties of the individual components. We search for correlations between radio band light curves and the kinematic properties of the jet components. Results: We present an alternative kinematic scenario for jet component motion in S5 0716+714. We present evidence for the apparent stationarity of jet components (with regard to their core separation) with time. Jet components, however, do seem to move significantly non-radially with regard to their position angle and in a direction perpendicular to the major axis of the jet. We discuss a possible correlation between the long-term radio flux-density variability and apparent jet component motions. Conclusions: In S5 0716+714 an alternative motion scenario is proposed. With regard to the core separation, rather stationary components can fit the VLBI observations well. A new model to

  17. Intermediate BL Lac objects

    NASA Astrophysics Data System (ADS)

    Bondi, M.; Marchã, M. J. M.; Dallacasa, D.; Stanghellini, C.

    2001-08-01

    The 200-mJy sample, defined by Marchã et al., contains about 60 nearby, northern, flat-spectrum radio sources. In particular, the sample has proved effective at finding nearby radio-selected BL Lac objects with radio luminosities comparable to those of X-ray-selected objects, and low-luminosity flat-spectrum weak emission-line radio galaxies (WLRGs). The 200-mJy sample contains 23 BL Lac objects (including 6 BL Lac candidates) and 19 WLRGs. We will refer to these subsamples as the 200-mJy BL Lac sample and the 200-mJy WLRG sample, respectively. We have started a systematic analysis of the morphological pc-scale properties of the 200-mJy radio sources using VLBI observations. This paper presents VLBI observations at 5 and 1.6GHz of 14 BL Lac objects and WLRGs selected from the 200-mJy sample. The pc-scale morphology of these objects is briefly discussed. We derive the radio beaming parameters of the 200-mJy BL Lac objects and WLRGs and compare them with those of other BL Lac samples and with a sample of FR I radio galaxies. The overall broad-band radio, optical and X-ray properties of the 200-mJy BL Lac sample are discussed and compared with those of other BL Lac samples, radio- and X-ray-selected. We find that the 200-mJy BL Lac objects fill the gap between HBL and LBL objects in the colour-colour plot, and have intermediate αXOX as expected in the spectral energy distribution unification scenario. Finally, we briefly discuss the role of the WLRGs.

  18. Properties of optically selected BL Lacertae candidates from the SDSS

    NASA Astrophysics Data System (ADS)

    Kügler, S. D.; Nilsson, K.; Heidt, J.; Esser, J.; Schultz, T.

    2014-09-01

    Context. Deep optical surveys open the avenue for finding large numbers of BL Lac objects that are hard to identify because they lack the unique properties classifying them as such. While radio or X-ray surveys typically reveal dozens of sources, recent compilations based on optical criteria alone have increased the number of BL Lac candidates considerably. However, these compilations are subject to biases and may contain a substantial number of contaminating sources. Aims: In this paper we extend our analysis of 182 optically selected BL Lac object candidates from the SDSS with respect to an earlier study. The main goal is to determine the number of bona fide BL Lac objects in this sample. Methods: We examine their variability characteristics, determine their broad-band radio-UV spectral energy distributions (SEDs), and search for the presence of a host galaxy. In addition we present new optical spectra for 27 targets with improved signal-to-noise ratio with respect to the SDSS spectra. Results: At least 59% of our targets have shown variability between SDSS DR2 and our observations by more than 0.1-0.27 mag depending on the telescope used. A host galaxy was detected in 36% of our targets. The host galaxy type and luminosities are consistent with earlier studies of BL Lac host galaxies. Simple fits to broad-band SEDs for 104 targets of our sample derived synchrotron peak frequencies between 13.5 ≤ log 10(νpeak) ≤ 16 with a peak at log 10 ~ 14.5. Our new optical spectra do not reveal any new redshift for any of our objects. Thus the sample contains a large number of bona fide BL Lac objects and seems to contain a substantial fraction of intermediate-frequency peaked BL Lacs. Based on observations collected with the NTT on La Silla (Chile) operated by the European Southern Observatory under proposal 082.B-0133.Based on observations collected at the Centro Astronómico Hispano Alemán (CAHA), operated jointly by the Max-Planck-Institut für Astronomie and the

  19. Lacerta

    NASA Astrophysics Data System (ADS)

    Murdin, P.

    2000-11-01

    (the Lizard; abbrev. Lac, gen. Lacertae; area 201 sq. deg.) A northern constellation which lies between Cygnus and Andromeda, and culminates at midnight in late August. It was introduced by the astronomer Johannes Hevelius (1611-87) of Danzig (Gdansk), who included it in his atlas Firmamentum Sobiescianum sive Uranographia of 1687. Hevelius also gave it the alternative name of Stellio (the Stelli...

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

    NASA Astrophysics Data System (ADS)

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

    2016-07-01

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

  1. Multiwavelength intraday variability of the BL Lacertae S5 0716+714

    NASA Astrophysics Data System (ADS)

    Gupta, Alok C.; Krichbaum, T. P.; Wiita, P. J.; Rani, B.; Sokolovsky, K. V.; Mohan, P.; Mangalam, A.; Marchili, N.; Fuhrmann, L.; Agudo, I.; Bach, U.; Bachev, R.; Böttcher, M.; Gabanyi, K. E.; Gaur, H.; Hawkins, K.; Kimeridze, G. N.; Kurtanidze, O. M.; Kurtanidze, S. O.; Lee, C.-U.; Liu, X.; McBreen, B.; Nesci, R.; Nestoras, G.; Nikolashvili, M. G.; Ohlert, J. M.; Palma, N.; Peneva, S.; Pursimo, T.; Semkov, E.; Strigachev, A.; Webb, J. R.; Wiesemeyer, H.; Zensus, J. A.

    2012-09-01

    We report results from a one-week multiwavelength campaign to monitor the BL Lacertae object (BL Lac) S5 0716+714 (on 2009 December 9-16). Nine ground-based telescopes at widely separated longitudes and one space-based telescope aboard the Swift satellite collected optical data. Radio data were obtained from the Effelsberg and Urumqi observatories and X-ray data from Swift. In the radio bands, the source shows rapid [˜(0.5-1.5) d] intraday variability with peak amplitudes of up to ˜10 per cent. The variability at 2.8 cm leads by about 1 d the variability at 6 and 11 cm. This time lag and more rapid variations suggest an intrinsic contribution to the source's intraday variability at 2.8 cm, while at 6 and 11 cm, interstellar scintillation (ISS) seems to predominate. Large and quasi-sinusoidal variations of ˜0.8 mag were detected in the V, R and I bands. The X-ray data (0.2-10 keV) do not reveal significant variability on a 4 d time-scale, favouring reprocessed inverse Compton over synchrotron radiation in this band. The characteristic variability time-scales in radio and optical bands are similar. A quasi-periodic variation of 0.9-1.1 d in the optical data may be present, but if so it is marginal and limited to 2.2 cycles. Cross-correlations between radio and optical bands are discussed. The lack of a strong radio-optical correlation indicates different physical causes of variability (ISS at long radio wavelengths, source intrinsic origin in the optical) and is consistent with a high jet opacity and a compact synchrotron component peaking at ≃100 GHz in an ongoing very prominent flux-density outburst. For the campaign period, we construct a quasi-simultaneous spectral energy distribution, including γ-ray data from the Fermi satellite. We obtain lower limits for the relativistic Doppler boosting of δ ≥ 12-26, which for a BL Lac-type object is remarkably high.

  2. Imaging redshift estimates for Fermi BL Lac objects

    SciTech Connect

    Stadnik, Matt; Romani, Roger W. E-mail: rwr@astro.stanford.edu

    2014-04-01

    We have obtained WIYN and SOAR i' images of BL Lacertae objects and used these to detect or constrain the flux of the host galaxy. Under common standard candle assumptions, these data provide estimates of, or lower bounds on, the redshift. Our targets are a set of flat-spectrum radio counterparts of high flux Fermi Large Area Telescope sources, with sensitive spectral observations showing them to be continuum-dominated BL Lac objects. In this sample, 5 of 11 BL Lac objects yielded significant host detections, with standard candle redshifts z = 0.13-0.58. Our estimates and lower bounds are generally in agreement with other redshifts estimates, although our z = 0.374 estimate for J0543–5532 implies a significantly sub-luminous host.

  3. The ultraviolet/optical variability of PG 1553+11. [BL Lac object

    NASA Technical Reports Server (NTRS)

    Miller, H. R.; Carini, M. T.; Gaston, B. J.; Hutter, D. J.

    1988-01-01

    Ultraviolet optical observations of the BL Lacertae object, PG 1553+11, indicate that significant color variations are associated with the luminosity variations seen in the ultraviolet and the optical regions of the spectrum. The color variations are consistent with the presence of an accretion disk in this system.

  4. RAPID TeV GAMMA-RAY FLARING OF BL LACERTAE

    SciTech Connect

    Arlen, T.; Aune, T.; Bouvier, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Dickherber, R.; Benbow, W.; Cesarini, A.; Connolly, M. P.; Ciupik, L.; Cui, W.; Feng, Q.; Finley, J. P.; Dumm, J.; Fortson, L.; Errando, M.; Falcone, A.; Federici, S.; Finnegan, G. E-mail: cui@purdue.edu; Collaboration: VERITAS Collaboration; and others

    2013-01-10

    We report on the detection of a very rapid TeV gamma-ray flare from BL Lacertae on 2011 June 28 with the Very Energetic Radiation Imaging Telescope Array System (VERITAS). The flaring activity was observed during a 34.6 minute exposure, when the integral flux above 200 GeV reached (3.4 {+-} 0.6) Multiplication-Sign 10{sup -6} photons m{sup -2} s{sup -1}, roughly 125% of the Crab Nebula flux measured by VERITAS. The light curve indicates that the observations missed the rising phase of the flare but covered a significant portion of the decaying phase. The exponential decay time was determined to be 13 {+-} 4 minutes, making it one of the most rapid gamma-ray flares seen from a TeV blazar. The gamma-ray spectrum of BL Lacertae during the flare was soft, with a photon index of 3.6 {+-} 0.4, which is in agreement with the measurement made previously by MAGIC in a lower flaring state. Contemporaneous radio observations of the source with the Very Long Baseline Array revealed the emergence of a new, superluminal component from the core around the time of the TeV gamma-ray flare, accompanied by changes in the optical polarization angle. Changes in flux also appear to have occurred at optical, UV, and GeV gamma-ray wavelengths at the time of the flare, although they are difficult to quantify precisely due to sparse coverage. A strong flare was seen at radio wavelengths roughly four months later, which might be related to the gamma-ray flaring activities. We discuss the implications of these multiwavelength results.

  5. Historic Light Curve and Long-Term Optical Variation of BL Lacertae 2200+420

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Xie, G. Z.; Pecontal, E.; Pecontal, A.; Copin, Y.

    1998-11-01

    In this paper, historical optical (UBVRI) data and newly observed data from the Yunnan Observatory of China (over ~100 yr) are presented for BL Lacertae. Large variations of ΔU = 5.12 mag, ΔB = 5.31 mag, ΔV = 4.73 mag, ΔR = 2.59 mag, and ΔI = 2.54 mag, and color indices of U-B = -0.11 +/- 0.20, B-V = 1.0 +/- 0.11, V-R = 0.73 +/- 0.19, V-I = 1.42 +/- 0.25, R-I = 0.82 +/- 0.11, and B-I = 2.44 +/- 0.29 have been obtained from the literature. The Jurkevich method is used to investigate the existence of periods in the B-band light curve, and a long-term period of 14 yr is found. The 0.6 and 0.88 yr periods reported by Webb et al. are confirmed. In addition, a close relation between B-I and B is found, suggesting that the spectrum flattens when the source brightens.

  6. Optically Selected BL Lacertae Candidates from the Sloan Digital Sky Survey Data Release Seven

    NASA Astrophysics Data System (ADS)

    Plotkin, Richard M.; Anderson, Scott F.; Brandt, W. N.; Diamond-Stanic, Aleksandar M.; Fan, Xiaohui; Hall, Patrick B.; Kimball, Amy E.; Richmond, Michael W.; Schneider, Donald P.; Shemmer, Ohad; Voges, Wolfgang; York, Donald G.; Bahcall, Neta A.; Snedden, Stephanie; Bizyaev, Dmitry; Brewington, Howard; Malanushenko, Viktor; Malanushenko, Elena; Oravetz, Dan; Pan, Kaike; Simmons, Audrey

    2010-02-01

    We present a sample of 723 optically selected BL Lac candidates from the Sloan Digital Sky Survey Data Release 7 (SDSS DR7) spectroscopic database encompassing 8250 deg2 of sky; our sample constitutes one of the largest uniform BL Lac samples yet derived. Each BL Lac candidate has a high-quality SDSS spectrum from which we determine spectroscopic redshifts for ~60% of the objects. Redshift lower limits are estimated for the remaining objects utilizing the lack of host galaxy flux contamination in their optical spectra; we find that objects lacking spectroscopic redshifts are likely at systematically higher redshifts. Approximately 80% of our BL Lac candidates match to a radio source in FIRST/NVSS, and ~40% match to a ROSAT X-ray source. The homogeneous multiwavelength coverage allows subdivision of the sample into 637 radio-loud BL Lac candidates and 86 weak-featured radio-quiet objects. The radio-loud objects broadly support the standard paradigm unifying BL Lac objects with beamed radio galaxies. We propose that the majority of the radio-quiet objects may be lower-redshift (z < 2.2) analogs to high-redshift weak line quasars (i.e., active galactic nucleus with unusually anemic broad emission line regions). These would constitute the largest sample of such objects, being of similar size and complementary in redshift to the samples of high-redshift weak line quasars previously discovered by the SDSS. However, some fraction of the weak-featured radio-quiet objects may instead populate a rare and extreme radio-weak tail of the much larger radio-loud BL Lac population. Serendipitous discoveries of unusual white dwarfs, high-redshift weak line quasars, and broad absorption line quasars with extreme continuum dropoffs blueward of rest-frame 2800 Å are also briefly described.

  7. The awakening of BL Lacertae: observations by Fermi, Swift and the GASP-WEBT

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Villata, M.; D'Ammando, F.; Larionov, V. M.; Gurwell, M. A.; Mirzaqulov, D. O.; Smith, P. S.; Acosta-Pulido, J. A.; Agudo, I.; Arévalo, M. J.; Bachev, R.; Benítez, E.; Berdyugin, A.; Blinov, D. A.; Borman, G. A.; Böttcher, M.; Bozhilov, V.; Carnerero, M. I.; Carosati, D.; Casadio, C.; Chen, W. P.; Doroshenko, V. T.; Efimov, Yu. S.; Efimova, N. V.; Ehgamberdiev, Sh. A.; Gómez, J. L.; González-Morales, P. A.; Hiriart, D.; Ibryamov, S.; Jadhav, Y.; Jorstad, S. G.; Joshi, M.; Kadenius, V.; Klimanov, S. A.; Kohli, M.; Konstantinova, T. S.; Kopatskaya, E. N.; Koptelova, E.; Kimeridze, G.; Kurtanidze, O. M.; Larionova, E. G.; Larionova, L. V.; Ligustri, R.; Lindfors, E.; Marscher, A. P.; McBreen, B.; McHardy, I. M.; Metodieva, Y.; Molina, S. N.; Morozova, D. A.; Nazarov, S. V.; Nikolashvili, M. G.; Nilsson, K.; Okhmat, D. N.; Ovcharov, E.; Panwar, N.; Pasanen, M.; Peneva, S.; Phipps, J.; Pulatova, N. G.; Reinthal, R.; Ros, J. A.; Sadun, A. C.; Schwartz, R. D.; Semkov, E.; Sergeev, S. G.; Sigua, L. A.; Sillanpää, A.; Smith, N.; Stoyanov, K.; Strigachev, A.; Takalo, L. O.; Taylor, B.; Thum, C.; Troitsky, I. S.; Valcheva, A.; Wehrle, A. E.; Wiesemeyer, H.

    2013-12-01

    Since the launch of the Fermi satellite, BL Lacertae has been moderately active at γ-rays and optical frequencies until 2011 May, when the source started a series of strong flares. The exceptional optical sampling achieved by the GLAST-AGILE Support Program of the Whole Earth Blazar Telescope in collaboration with the Steward Observatory allows us to perform a detailed comparison with the daily γ-ray observations by Fermi. Discrete correlation analysis between the optical and γ-ray emission reveals correlation with a time lag of 0 ± 1 d, which suggests cospatiality of the corresponding jet emitting regions. A better definition of the time lag is hindered by the daily gaps in the sampling of the extremely fast flux variations. In general, optical flares present more structure and develop on longer time-scales than corresponding γ-ray flares. Observations at X-rays and at millimetre wavelengths reveal a common trend, which suggests that the region producing the mm and X-ray radiation is located downstream from the optical and γ-ray-emitting zone in the jet. The mean optical degree of polarization slightly decreases over the considered period and in general it is higher when the flux is lower. The optical electric vector polarization angle (EVPA) shows a preferred orientation of about 15°, nearly aligned with the radio core EVPA and mean jet direction. Oscillations around it increase during the 2011-2012 outburst. We investigate the effects of a geometrical interpretation of the long-term flux variability on the polarization. A helical magnetic field model predicts an evolution of the mean polarization that is in reasonable agreement with the observations. These can be fully explained by introducing slight variations in the compression factor in a transverse shock waves model.

  8. The long-term Swift observations of the high-energy peaked BL Lacertae source 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Kapanadze, B.; Romano, P.; Vercellone, S.; Kapanadze, S.; Mdzinarishvili, T.; Kharshiladze, G.

    2016-03-01

    We present the results based on the monitoring of the high-energy peaked BL Lacertae object 1ES 1959+650 by the Swift satellite during 2005-2014. Our timing study shows that the source was highly variable on longer (weeks-to-months) time-scales with the 0.3-10 keV fluxes ranging by a factor of 8. It sometimes showed a significant intra-day variability in the course of ˜1 ks, detected mainly in the epochs of higher brightness states. The flux variability exhibited an erratic character and no signatures of periodic variations are revealed. The X-ray spectra were mainly curved with broad ranges of photon index, curvature parameter, hardness ratio, synchrotron spectral energy distribution (SED) peak location which exhibited a significant variability with the flux at different time-scales. Our study of multi-wavelength cross-correlations shows that the one-zone synchrotron self-Compton scenario was not always valid for 1ES 1959+650. The X-ray flares were sometimes not accompanied with an increasing activity in the γ-ray or lower-energy parts of the spectrum and vice versa. Similar to the prominent `orphan' TeV event in 2002, significant flares in the high-energy and very high energy bands in 2009 May and 2012 May were not accompanied by those in the synchrotron part of the spectrum. Similar to other TeV-detected high-energy peaked BLLs, the stochastic acceleration of the electrons from the magnetic turbulence close to the shock front may be more important for our target compared to other scenarios since it showed mainly broader synchrotron SEDs during the X-ray flares expected when the stochastic mechanism is more efficient.

  9. Multifrequency observations of the BL Lacertae object 0735+178

    NASA Technical Reports Server (NTRS)

    Bregman, J. N.; Glassgold, A. E.; Huggins, P. J.; Aller, H. D.; Aller, M. F.; Hodge, P. E.; Rieke, G. H.; Lebofsky, M. J.; Pollock, J. T.; Pica, A. J.

    1984-01-01

    In each of the present four simultaneous spectra covering the radio-through-X-ray regimes, the IR-UV synchrotron continuum dominates the total observed power and presumably becomes opague between 10 to the 11th and 10 to the 13th Hz. Nonsimultaneous observations were also conducted, over a longer time period, in order to study long- and short-term variability at X-ray, optical, and radio frequencies. These data indicate that the rapid and dramatic variations evident at IR and optical wavelengths are absent at radio and X-ray frequencies, supporting a view of IR-UV flux emanation from a small region, while the X-rays are produced by the inverse Compton process in the radio-emitting region. Particles, photons and magnetic field may not be far from equipartition in this region. Theoretical suggestions are developed regarding the radial behavior of the electron density and magnetic field.

  10. Ondas de choque em jatos de quasares e objetos BL Lacertae

    NASA Astrophysics Data System (ADS)

    Melo, F. E.; Botti, L. C. L.

    2003-08-01

    Este trabalho é parte de um projeto que vem sendo realizado há dois anos no CRAAM, cujos objetivos principais são analisar e aplicar um modelo generalizado de ondas de choque em jatos relativísticos de plasma, presentes em quasares e objetos BL Lacertae, para explicar a variabilidade observada nestes objetos. O método consiste em uma decomposição de curvas de luz em séries de explosões similares, em várias freqüências, baseando-se em uma evolução espectro-temporal média das explosões. A partir da evolução média, um ajuste de cada explosão é feito com base em equações empíricas, modificando-se apenas parâmetros específicos de cada explosão. Inicialmente o modelo foi aplicado ajustando-se as curvas de luz a explosões delineadas por uma evolução do choque em três estágios, segundo a predominância do processo de emissão: síncrotron, Compton e adiabático. Entretanto, nesta nova fase de projeto, visando uma parametrização mais concisa, uma otimização do algoritmo de ajuste e uma convergência mais rápida, a formulação para cada evento foi assumida com uma evolução em apenas dois estágios: subida e descida. Isto possibilitou uma ótima delineação das curvas de luz das fontes OV236, OJ287, 3C273 e BL Lac, entre 1980 e 2000, nas freqüências 4.8, 8.0, 14.5 e 22 GHz, utilizando-se dados do Observatório da Universidade de Michigan, do Observatório do Itapetinga (Atibaia SP) e do Observatório Metsähovi. Como conclusões importantes, verificou-se que: os parâmetros ajustados descrevem o comportamento do jato; os valores do índice que descreve a expansão do jato sugerem que o mesmo se expande de uma forma não-cônica; o campo magnético é turbulento atrás da frente de choque; e as peculiaridades das explosões são devidas à influência de grandezas tais como o coeficiente da distribuição espectral de energia dos elétrons, a intensidade de campo magnético e o fator de feixe Doppler, no início do choque.

  11. Veritas Observations of Relativistic Outflows in - and Intermediate-Frequency BL Lac Objects

    NASA Astrophysics Data System (ADS)

    Prokoph, Heike

    2014-03-01

    The majority of blazars detected at very high energies (VHE; E > 100 GeV) are high-frequency-peaked BL Lac objects (HBLs). Low- and intermediate-frequency-peaked BL Lacs (LBLs/IBLs with synchrotron-peak frequencies in the infrared and optical regime) are generally more powerful, more luminous, and have a richer jet environment than HBLs. However, only a handful of these IBL and LBLs have been detected by ground-based gamma-ray telescopes, typically during high-flux states. The VERITAS array has been monitoring five known VHE LBLs/IBLs since 2009: 3C 66A, W Comae, PKS 1424+240, S5 0716+714 and BL Lacertae, with typical exposures of 5-10 hours per year. The results of these long-term observations are presented, including a bright, subhour-scale VHE flare of BL Lacertae in June 2011, the first low-state detections of 3C 66A and W Comae, and the detection and characterization of the IBL B2 1215+30.

  12. BL Lac Objects at the highest redshifts

    NASA Astrophysics Data System (ADS)

    Ajello, Marco

    2013-10-01

    For a long time high-redshift BL Lac objects were deemed not to exist. Fermi showed us that there is relevant population of BL Lacs with redshift beyond 1.0. Some of them belong to the high-synchrotron peaked (HSP) class and are among the hardest gamma-ray sources detected by Fermi showing emission up and beyond 100 GeV. This makes them the most luminous BL Lacs ever detected and rates them among the most powerful accelerators in the Universe. We plan to observe 3 extreme BL Lacs simultaneously with XMM-Newton, GROND and Swift. This will provide unprecedented coverage of the synchrotron peak from IR to hard X-ray allowing us: to understand the nature and the energetic of these objects, to answer long-standing questions on the blazar sequence and to use them as probes of the EBL.

  13. Probing the Innermost Regions of AGN Jets and Their Magnetic Fields with RadioAstron. I. Imaging BL Lacertae at 21 Microarcsecond Resolution

    NASA Astrophysics Data System (ADS)

    Gómez, José L.; Lobanov, Andrei P.; Bruni, Gabriele; Kovalev, Yuri Y.; Marscher, Alan P.; Jorstad, Svetlana G.; Mizuno, Yosuke; Bach, Uwe; Sokolovsky, Kirill V.; Anderson, James M.; Galindo, Pablo; Kardashev, Nikolay S.; Lisakov, Mikhail M.

    2016-02-01

    We present the first polarimetric space very long baseline interferometry (VLBI) imaging observations at 22 GHz. BL Lacertae was observed in 2013 November 10 with the RadioAstron space VLBI mission, including a ground array of 15 radio telescopes. The instrumental polarization of the space radio telescope is found to be less than 9%, demonstrating the polarimetric imaging capabilities of RadioAstron at 22 GHz. Ground-space fringes were obtained up to a projected baseline distance of 7.9 Earth diameters in length, allowing us to image the jet in BL Lacertae with a maximum angular resolution of 21 μas, the highest achieved to date. We find evidence for emission upstream of the radio core, which may correspond to a recollimation shock at about 40 μas from the jet apex, in a pattern that includes other recollimation shocks at approximately 100 and 250 μas from the jet apex. Polarized emission is detected in two components within the innermost 0.5 mas from the core, as well as in some knots 3 mas downstream. Faraday rotation analysis, obtained from combining RadioAstron 22 GHz and ground-based 15 and 43 GHz images, shows a gradient in rotation measure and Faraday-corrected polarization vector as a function of position angle with respect to the core, suggesting that the jet in BL Lacertae is threaded by a helical magnetic field. The intrinsic de-boosted brightness temperature in the unresolved core exceeds 3× {10}12 K, suggesting, at the very least, departure from equipartition of energy between the magnetic field and radiating particles.

  14. Optical Variability of BL Lacertae During the Major Outburst of 1997

    NASA Technical Reports Server (NTRS)

    Ghosh, K. K.; Ramsey, B. D.; Sadun, A. C.; Soundarajaperumal, S.; Wang, J.

    1999-01-01

    We have undertaken an investigation of recent flux variability in BL Lac. We present optical observations taken over 12 nights documenting major as well as minor outbursts. This has been combined, for purposes of multifrequency analysis, with published X-ray and gamma ray data taken for an additional single night. On two nights in particular, which includes the night of the X-ray observations, a major outburst of about a full magnitude of variation was recorded. All the data have been analyzed with theoretical models. Attempts were made to use synchrotron self-Compton and external Comptonization models to explain the data; however both classes of models were found lacking. More satisfactory results were obtained using an analytical model proposed by Wang et al. that involves the evolution of synchrotron spectra in a homogeneous jet due to the injection of relativistic electrons, taking into account radiation losses during the outbursts. It is hoped that the results of this study of BL Lac, an archetype for the class of blazars in general, represent a more generic phenomenon applicable to the entire class.

  15. Optical Variability of BL Lacertae During the Major Outburst of 1997

    NASA Technical Reports Server (NTRS)

    Ghosh, K. K.; Ramsey, B. D.; Sadun, A. C.; Soundararajaperumal, S.; Wang, J.

    2000-01-01

    We have undertaken an investigation of recent flux variability in BL Lac. We present optical observations taken over 22 nights documenting major as well as minor outbursts. This has been combined, for purposes of multifrequency analysis, with published X-ray and T-ray data taken for an additional single night, On two nights in particular, including the night of the X-ray observations, a major outburst of about a full magnitude of variation was recorded. All the data have been analyzed with theoretical models. Attempts were made to use synchrotron self-Compton and external Comptonization models to explain the data; however, both classes of models were found lacking. More satisfactory results were obtained using an analytical model proposed by Wang et al. that involves the evolution of synchrotron spectra in a homogeneous jet due to the injection of relativistic electrons, taking into account radiation losses during the outbursts. It is hoped that the results of this study of BL Lac, an archetype for the class of blazars in general, represent a more generic phenomenon applicable to the entire class.

  16. The 1997 Outburst of BL Lacertae and Detection of a 0.6-mag Rapid Variation

    NASA Astrophysics Data System (ADS)

    Matsumoto, Katsura; Kato, Taichi; Nogami, Daisaku; Kawaguchi, Toshihiro; Kinnunen, Timo; Poyner, Gary

    1999-04-01

    Photometric observations of BL Lac were carried out during the large optical and X-ray outburst in 1997. Time-resolved photometry on 1997 August 2 revealed a rapid increase of brightness by about 0.6 mag within 40 min. This large-amplitude, short-time variation is the most active one among known variability of blazars in the optical wavelength. By considering a model based on the ``synchrotron self-Compton model'' of the relativistic jets of blazars, the size of the variable source should be R ~ 7.2 x 10^{{14}} cm from the 40 min variation. The power-density spectrum of the light curve on the night yielded a dependence of the power to the frequency f^{{-1.0}} for timescales of the variabilities and down to a possible minimum timescale of around 10 min. The clear difference between the observed f^{{-1.0}} dependence from the canonical f^{{-1.5}} --f^{{-1.8}} power indices observed in X-ray variations of radio-loud AGNs suggests that different mechanisms are responsible for short-term optical variability between BL Lacs and radio-loud AGNs.

  17. Studies of the jet in BL Lacertae. I. Recollimation shock and moving emission features

    SciTech Connect

    Cohen, M. H.; Hovatta, T.; Meier, D. L.; Arshakian, T. G.; Homan, D. C.; Kovalev, Y. Y.; Pushkarev, A. B.; Savolainen, T.

    2014-06-01

    Parsec-scale VLBA images of BL Lac at 15 GHz show that the jet contains a permanent quasi-stationary emission feature 0.26 mas (0.34 pc projected) from the core, along with numerous moving features. In projection, the tracks of the moving features cluster around an axis at a position angle of –166.°6 that connects the core with the standing feature. The moving features appear to emanate from the standing feature in a manner strikingly similar to the results of numerical two-dimensional relativistic magneto-hydrodynamic (RMHD) simulations in which moving shocks are generated at a recollimation shock (RCS). Because of this, and the close analogy to the jet feature HST-1 in M87, we identify the standing feature in BL Lac as an RCS. We assume that the magnetic field dominates the dynamics in the jet, and that the field is predominantly toroidal. From this we suggest that the moving features are compressions established by slow and fast mode magneto-acoustic MHD waves. We illustrate the situation with a simple model in which the slowest moving feature is a slow-mode wave, and the fastest feature is a fast-mode wave. In the model, the beam has Lorentz factor Γ{sub beam}{sup gal}≈3.5 in the frame of the host galaxy and the fast mode wave has Lorentz factor Γ{sub Fwave}{sup beam}≈1.6 in the frame of the beam. This gives a maximum apparent speed for the moving features, β{sub app} = v{sub app}/c = 10. In this model the Lorentz factor of the pattern in the galaxy frame is approximately three times larger than that of the beam itself.

  18. Simultaneous UV, optical and radio monitoring of the BL Lac object OJ 287 in March 1993

    NASA Technical Reports Server (NTRS)

    Pian, E.; Edelson, R.; Wagner, S.; Bregman, J.; George, I.; Treves, A.; Wamsteker, W.; Bock, H.; Carini, M.; Courvoisier, T.

    1995-01-01

    The BL Lacertae object OJ 287 was intensively monitored with the IUE satellite from 1993 March 15 to 20 in the 2000-3000 A wavelength region. The very low emission state of the source hampered the detection during part of the 23 performed exposures. The light curve at 2650 A constructed with the 11 best images exhibits a variable trend with a factor is less than or approximately 2 enhancement of the flux in about 3 hours. Simultaneous ground based observations show an optical flux variability of smaller amplitude, but correlated with the UV light curve without any apparent lag. The radio light curve is nearly constant. The UV emission state is the weakest observed in 15 years for this flaring blazard, being a factor of less than orapproximately 20 lower than the maximum recorded one.

  19. Comparison between TeV and non-TeV BL Lac Objects

    NASA Astrophysics Data System (ADS)

    Lin, Chao; Fan, Jun-Hui

    2016-07-01

    BL Lacertae objects (BL Lacs) are the dominant population of TeV emitting blazars. In this work, we investigate whether there are any special observational properties associated with TeV sources. To do so, we will compare the observational properties of TeV detected BL Lacs (TeV BLs) with non-TeV detected BL Lac objects (non-TeV BLs). From the 3rd Fermi/LAT source catalog (3FGL), we can obtain 662 BL Lacs, out of which 47 are TeV BLs and 615 are non-TeV BLs. Their multi-wavelength flux densities (F R, F O, F X and F γ), photon spectral indexes (αX ph and αph γ), and effective spectral indexes (αRO and αOX) are compiled from the available literature. Then the luminosities (log vL R, log vL O, log vL X, log vL γ) are calculated. From comparisons, we find that TeV BLs are different from low synchrotron peaked BLs and intermediate synchrotron peaked BLs, but TeV BLs show similar properties to high synchrotron peaked (HSP) BLs. Therefore, we concentrated on a comparison between TeV HSP BLs and non-TeV HSP BLs. Analysis results suggest that TeV HSP BLs and non-TeV HSP BLs exhibit some differences in their αRO and αγ ph, but their other properties are quite similar.

  20. Gamma-ray luminosity function of BL Lac objects

    NASA Astrophysics Data System (ADS)

    Zeng, Houdun; Yan, Dahai; Zhang, Li

    2014-06-01

    The gamma-ray luminosity function (GLF) of BL Lac objects is constructed by using a sample of BL Lac objects with redshifts selected from the Second LAT AGN catalog. The GLFs of BL Lacs in the frame of the pure density evolution (PDE), the pure luminosity evolution (PLE), and the luminosity-dependent density (LDDE) models are determined by using the Markov Chain Monte Carlo (MCMC) technique, respectively. Our results suggest that the PDE model can give best description for BL Lac GLF based on the combination of constraints of model parameters and good fits to the observed data of Fermi-Large Area Telescope (LAT) BL Lacs, but other two models (PLE and LDDE) cannot be excluded. Based on our constructed GLFs, the contribution to the extragalactic diffuse gamma-ray background (EGRB) from BL Lacs is estimated, and ˜1-5 per cent of the EGRB in the 0.1-100 GeV band is found to come from unresolved BL Lacs (including the cascade emission). In addition, it is found that the BL Lac GLF is very different from flat spectrum radio quasar GLF and then the contribution of blazars to the EGRB should be estimated separately.

  1. Variabilidade óptica de longo período e precessão de jato: o caso de BL Lacertae

    NASA Astrophysics Data System (ADS)

    Caproni, A.; Abraham, Z.

    2003-08-01

    Variabilidade é tipicamente uma característica de AGNs, sendo observada em toda a faixa eletromagnética. Em relação às escalas de tempo, variações desde horas até de algumas décadas foram encontradas por vários autores. Em alguns casos, análises temporais de curvas de luz mostram a existência de periodicidade nas variações observadas. Um exemplo de objeto que preenche as características mencionadas acima é BL Lacertae, o protótipo da classe BL Lac dos AGNs. Neste trabalho, nós interpretamos a variabilidade periódica de longo período detectada na curva de luz na banda B (~7,5 anos) como o resultado da periodicidade na amplificação da radiação oriunda do jato relativístico. Neste cenário, a amplificação periódica seria induzida pela precessão, que muda o ângulo entre o jato e a linha de visada. Com esta abordagem e vínculos adicionais fornecidos por observações em altas energias, nós podemos impor limites para os parâmetros do modelo de precessão, tais como o fator de Lorentz associado ao movimento global do jato, o ângulo de abertura do cone de precessão e o ângulo entre o eixo do cone e a linha de visada.

  2. Gamma-ray observations of BL Lac objects

    NASA Technical Reports Server (NTRS)

    Hanlon, L.; McBreen, B.; OFlaherty, K.; Metcalfe, L.; Hunter, S.; Tashiro, M.; Wagner, S.; Bouchet, P.; Nicolson, G. D.; Smith, N. J.

    1997-01-01

    The results from observations of a sample of BL Lac objects by the Compton telescope (COMPTEL) and energetic gamma ray experiment telescope (EGRET) onboard the Compton Gamma Ray Observatory (CGRO) are presented. The main targets in the sample were selected on the basis of their X-ray brightness and apparent spectral hardening at hard X-ray energies. One of the targets, PKS 0521-365 was detected by EGRET, and these data are presented together with contemporaneous ground-based radio data. Subsequent X-ray observations of this source with the Advanced Satellite for Cosomology and Astrophysics (ASCA) demonstrated that, although originally classified as a BL Lac object, it is better described as a flat spectrum radio quasar. Upper limits on the gamma ray flux from all the non-detected BL lacs are presented.

  3. QUASI-PERIODICITIES OF THE BL LACERTAE OBJECT PKS 2155–304

    SciTech Connect

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

    2014-09-20

    We have searched for periodicities in our VRIJHK photometry of PKS 2155–304, which covers the years 2005-2012. A peak of the Fourier spectrum with high significance is found at T ∼ 315 days, confirming the recent findings by Zhang et al. The examination of the gamma-ray light curves from the Fermi archives yields a significant signal at ∼2T, which, while nominally significant, involves data spanning only ∼6T. Assuming a black hole mass of 10{sup 9} M {sub ☉}, the Keplerian distance corresponding to the quasi-period T is ∼10{sup 16} cm, about 50 Schwarzschild radii.

  4. The environment of x ray selected BL Lacs: Host galaxies and galaxy clustering

    NASA Technical Reports Server (NTRS)

    Wurtz, Ron; Stocke, John T.; Ellingson, Erica; Yee, Howard K. C.

    1993-01-01

    Using the Canada-France-Hawaii Telescope, we have imaged a complete, flux-limited sample of Einstein Medium Sensitivity Survey BL Lacertae objects in order to study the properties of BL Lac host galaxies and to use quantitative methods to determine the richness of their galaxy cluster environments.

  5. The BL-Lacertae gamma-ray blazar PKS 1424+240 associated with a group of galaxies at z = 0.6010

    NASA Astrophysics Data System (ADS)

    Rovero, A. C.; Muriel, H.; Donzelli, C.; Pichel, A.

    2016-04-01

    Context. PKS 1424+240 is a BL-Lac blazar with unknown redshift that was detected at high-energy gamma rays by Fermi-LAT with a hard spectrum. At very high energy (VHE), it was first detected by VERITAS and later confirmed by MAGIC. Its spectral energy distribution is highly attenuated at VHE gamma rays, which is coherent with distant sources. Several estimations enabled the redshift to be constrained to the range 0.6 BL-Lac objects directly, we aim to establish a reliable redshift value for this blazar by finding its host group of galaxies. Methods: Elliptical galaxies are associated with groups, and BL-Lac objects are typically hosted by them, so we decided to search for the host group of the blazar. For this, we performed optical spectroscopic observations of thirty objects in the field of view of PKS 1424+240 using the Gemini Multi-Object Spectrograph. After analysing the data for groups, we evaluated the probability of finding groups of galaxies by chance around the position of PKS 1424+240, using a deep catalogue of groups. We also used photometric data from the SDSS catalogue to analyse the red sequence of the proposed blazar host group Results: We found a new group of galaxies with eight members at z = 0.6010 ± 0.003, a virial radius of Rvir = 1.53 Mpc, and a velocity dispersion of σv = 813 ± 187 km s-1. The photometric study indicates that more members are probably populating this previously uncatalogued group of galaxies. The probability of PKS 1424+240 being a member of this group was found to be ≳98%. Conclusions: The new group of galaxies found at z = 0.6010 ± 0.003 is very likely

  6. The X-ray behaviour of the high-energy peaked BL Lacertae source PKS 2155-304 in the 0.3-10 keV band

    NASA Astrophysics Data System (ADS)

    Kapanadze, B.; Romano, P.; Vercellone, S.; Kapanadze, S.

    2014-10-01

    We present the results of our monitoring of the high-energy peaked BL Lac object PKS 2155-304 by the Swift/X-Ray Telescope (XRT) during 2005-2012. Our timing study shows that the source was highly variable both on longer (weeks-to-months) and intra-day time-scales, up to a factor of 7 in flux, and 30 per cent in fractional variability amplitudes, with no periodic variations. The X-ray spectra are mainly curved with broad ranges of photon index, curvature parameter, and hardness ratio which exhibit significant variability with the flux on different time-scales. Our study of multi-wavelength cross-correlations has revealed that the one-zone SSC scenario seems to be valid for the most optical-to-gamma-ray flares observed during 2006-2012. An `orphan' X-ray flare with no counterpart in other spectral bands suggests the existence of different electron populations. Based on the absence of a correlation between photon index and curvature parameter (expected from the energy-dependent acceleration probability scenario), the observed distribution of curvature parameter from the XRT spectra peaking at b = 0.37, and the observed anti-correlation between the curvature parameter and the 0.3-10 keV flux (i.e. lower curvatures in flaring states), we conclude that the most likely mechanism responsible for producing X-ray emission during the flares is the stochastic acceleration of the electrons.

  7. Rosat-Green bank sample of intermediate BL Lac objects

    SciTech Connect

    Laurent-Muchleisen, S.A.; Kollgaurd, R.I.; Feigelson, E.D.

    1997-04-01

    The Rosat-GreenBank BLLac sample consists of 119 objects and smoothly bridges the gap between the previously disparate subclasses of radio- and X-ray-selected objects. Further study of this sample should provide useful constraints to the unified scheme and help determine if modifications are necessary.

  8. Spectroscopy of optically selected BL Lac objects and their γ-ray emission

    SciTech Connect

    Sandrinelli, A.; Treves, A.; Farina, E. P.; Landoni, M.; Falomo, R.; Foschini, L.; Sbarufatti, B.

    2013-12-01

    We present Very Large Telescope optical spectroscopy of nine BL Lac objects of unknown redshift belonging to the list of optically selected radio-loud BL Lac candidates. We explore their spectroscopic properties and possible link with gamma-ray emission. From the new observations we determine the redshifts of four objects from faint emission lines or from absorption features of their host galaxies. In three cases we find narrow intervening absorptions from which a lower limit to the redshift is inferred. For the remaining two featureless sources, lower limits to the redshift are deduced from the absence of spectral lines. A search for γ counterpart emission shows that six out of the nine candidates are Fermi γ-ray emitters and we find two new detections. Our analysis suggests that most of the BL Lac objects still lacking redshift information are most likely located at high redshifts.

  9. INFRARED SPECTRAL OBSERVATION OF EIGHT BL LAC OBJECTS FROM THE SPITZER INFRARED SPECTROGRAPH

    SciTech Connect

    Chen, P. S.; Shan, H. G.

    2011-05-01

    The Spitzer Infrared Spectrograph (IRS) low-resolution spectra for eight BL Lac objects are presented in this paper. It can be seen that the infrared spectrum of S5 0716+714 shows in the IRS region many emission features that would be from a nearby galaxy. It is also shown that, except for the silicate absorptions around 10 {mu}m for some sources, emission lines in the infrared spectra for the other seven BL Lac objects are indeed very weak or absent. In addition, ignoring the silicate feature, all spectra can be well fitted by a power-law distribution indicative of the emission mechanism of the synchrotron radiation for these BL Lac objects in the IRS region.

  10. Computing the period of light variability in BL Lac objects using the Jurkevich method.

    NASA Astrophysics Data System (ADS)

    Zhang, Xiong; Xie, Guangzhong; Bai, Jinming

    1998-07-01

    The authors present a method for finding the period of light variation in BL Lac objects. They find the long periods light variability in the BL Lac objects OJ 287, ON 231 and Mrk 421. Analysis and computing have shown that the data sample should span a very long time interval (about 100 years), covering at least six times the length of the periodicity being claimed, the possible period should refer to large amplitude variations and thus directly visible in the light curve. When the amplitude is low, far more than six times of the period length will be necessary to demonstrate its reality. The authors conclude that the method is the best way for period search in BL Lac objects.

  11. Are BL Lac-type objects nearby black holes. [gas accretion model

    NASA Technical Reports Server (NTRS)

    Shapiro, S. L.; Elliot, J. L.

    1974-01-01

    It is pointed out that isolated black holes accreting interstellar gas can account for the characteristic properties of the Lacertids. Emission spectra for various interstellar gas densities and black hole masses are compared with the data plotted by Strittmatter et al. (1972) for the BL Lac-type objects. Rough estimates indicate that there may indeed be a finite number of stellar-mass black holes close to the earth as required by the theory. If it is determined that the BL Lac-type objects lie outside of the galactic disk a black hole accretion model may still apply if certain conditions are satisfied.

  12. Discovery of quasi-periodic oscillations in the AM Herculis object BL Hydri

    SciTech Connect

    Middleditch, J.; Imamura, J.N.; Steiman-Cameron, T.Y.

    1997-11-01

    We obtained high-speed optical photometry of the AM Her object BL Hyi at the Las Campanas Observatory and the Cerro Tololo Inter-American Observatory during 1989{endash}1996. BL Hyi was in its faint-luminosity state in 1989; it subsequently brightened and was in its high-luminosity state for our 1994{endash}1996 observations. We discovered broad, 0.2{endash}0.8 Hz quasi-periodic oscillations (QPOs) and narrower QPOs superposed on the broad QPOs when BL Hyi was in its high-luminosity state. The broad QPOs had widths of {Delta}f/f{sub p}{approximately}0.5{endash}1 and runs pulsed amplitudes of {approximately}1{percent}{minus}4{percent}, where f{sub p} is the frequency of the QPO peak. The narrow QPOs had widths of {Delta}f/f{sub p}{lt}0.1{endash}1 and rms pulsed amplitudes of less than 1{percent}. BL Hyi showed stronger QPOs and was slightly brighter in 1994 than in 1995{endash}1996. The amplitudes of the broad and narrow QPOs were modulated on the orbital period of the system; they were strongest during the bright orbital phase. BL Hyi is the fifth AM Her system to show the short-period QPOs discovered by Middleditch. {copyright} {ital 1997} {ital The American Astronomical Society}

  13. Hot absorbers and the x-ray spectra of BL Lac objects

    NASA Technical Reports Server (NTRS)

    Urry, C. Megan

    1994-01-01

    This is the final report to the National Aeronautics and Space Administration (NASA) concerning NASA grant NAG5-1671. This grant was awarded to Dr. C. Megan Urry of the Space Telescope Science Institute in response to a proposal, entitled 'Hot Absorbers and the X-Ray Spectra of BL Lac Objects.' The grant was originally awarded in October 1991 and expired in February 1994. The purpose of this project was to detect spectral features in high signal-to-noise Rosat PSPC spectra of X-ray-bright BL Lac objects. We were granted observations of three targets: PKS2155-304, Mrk421, and Mrk501. All three were bright and yielded 5,000-30,000 photons in the good PSPC data.

  14. STRUCTURED JETS IN BL LAC OBJECTS: EFFICIENT PeV NEUTRINO FACTORIES?

    SciTech Connect

    Tavecchio, Fabrizio; Ghisellini, Gabriele; Guetta, Dafne

    2014-09-20

    The origin of high-energy neutrinos (0.1–1 PeV range) detected by IceCube remains a mystery. In this work, we explore the possibility that efficient neutrino production can occur in structured jets of BL Lac objects, characterized by a fast inner spine surrounded by a slower layer. This scenario has been widely discussed in the framework of the high-energy emission models for BL Lac objects and radio galaxies. One of the relevant consequences of a velocity structure is the enhancement of the inverse Compton emission caused by the radiative coupling of the two zones. We show that a similar boosting could occur for the neutrino output of the spine through the photo-meson reaction of high-energy protons scattering off the amplified soft target photon field of the layer. Assuming the local density and the cosmological evolution of γ-ray BL Lac object derived from Fermi Large Area Telescope data, we calculate the expected diffuse neutrino intensity, which can match the IceCube data for a reasonable choice of parameters.

  15. X-Ray Spectral Variability Signatures of Flares in BL Lac Objects

    NASA Technical Reports Server (NTRS)

    Boettcher, Markus; Chiang, James; White, Nicholas E. (Technical Monitor)

    2002-01-01

    We are presenting a detailed parameter study of the time-dependent electron injection and kinematics and the self-consistent radiation transport in jets of intermediate and low-frequency peaked BL Lac objects. Using a time-dependent, combined synchrotron-self-Compton and external-Compton jet model, we study the influence of variations of several essential model parameters, such as the electron injection compactness, the relative contribution of synchrotron to external soft photons to the soft photon compactness, the electron- injection spectral index, and the details of the time profiles of the electron injection episodes giving rise to flaring activity. In the analysis of our results, we focus on the expected X-ray spectral variability signatures in a region of parameter space particularly well suited to reproduce the broadband spectral energy distributions of intermediate and low-frequency peaked BL Lac objects. We demonstrate that SSC- and external-Compton dominated models for the gamma-ray emission from blazars are producing significantly different signatures in the X-ray variability, in particular in the soft X-ray light curves and the spectral hysteresis at soft X-ray energies, which can be used as a powerful diagnostic to unveil the nature of the high-energy emission from BL Lac objects.

  16. The transition between BL Lac objects and flat spectrum radio quasars

    NASA Astrophysics Data System (ADS)

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

    2011-07-01

    We study the BL Lac objects detected in the 1-year all-sky survey of the Fermi satellite, with an energy spectral slope αγ in the 0.1-100 GeV band greater than 1.2. In the αγ versus γ-ray luminosity plane, these BL Lacs occupy the region populated by flat spectrum radio quasars (FSRQs). Studying the properties of their spectral energy distributions (SEDs) and of their emitting lines, we find that several of these BL Lacs have an SED similar to FSRQs and that they do have broad lines of large equivalent width (EW), and should be reclassified as FSRQs even adopting the current phenomenological definition (i.e. EW of the emitting line greater than 5 Å). In other cases, even if the EW is small, the emitting lines can be as luminous as in quasars, and again their SED is similar to the SED of FSRQs. Sources classified as BL Lacs with an SED appearing as intermediate between BL Lacs and FSRQs also have relatively weak broad emission lines and small EW, and can be considered as transition sources. These properties are confirmed also by model fitting that allows us to derive the relevant intrinsic jet parameters and the jet power. This study leads us to propose a physical distinction between the two classes of blazars, based on the luminosity of the broad-line region measured in Eddington units. The dividing line is of the order of LBLR/LEdd˜ 5 × 10-4, in good agreement with the idea that the presence of strong emitting lines is related to a transition in the accretion regime, becoming radiatively inefficient below a disc luminosity of the order of 1 per cent of the Eddington one.

  17. The optical periodic analysis of BL Lac object AO 0235+164

    NASA Astrophysics Data System (ADS)

    Wang, Hongtao

    2014-05-01

    BL Lac object AO 0235+164 is a well-known object. We collect a large number of effective observation in B, V, R and I band from historical literatures. The possible periods are analyzed by means of discrete correlation function (DCF) method, structure function (SF) method and Jurkevich (J-K) method. The results show that there are possible periodic variations of 2.63-2.66 years in B band, 2.79-2.84 years in V band, 2.57-2.87 years in R band, 2.62-2.88 years in I band, respectively.

  18. Contemporaneous Broadband Observations of Three High-redshift BL LAC Objects

    NASA Astrophysics Data System (ADS)

    Ackermann, M.; Ajello, M.; An, H.; Baldini, L.; Barbiellini, G.; Bastieri, D.; Bellazzini, R.; Bissaldi, E.; Blandford, R. D.; Bonino, R.; Bregeon, J.; Britto, R. J.; Bruel, P.; Buehler, R.; Caliandro, G. A.; Cameron, R. A.; Caragiulo, M.; Caraveo, P. A.; Cavazzuti, E.; Cecchi, C.; Charles, E.; Chekhtman, A.; Chiaro, G.; Ciprini, S.; Cohen-Tanugi, J.; Costanza, F.; Cutini, S.; D'Ammando, F.; de Angelis, A.; de Palma, F.; Desiante, R.; Di Mauro, M.; Di Venere, L.; Domínguez, A.; Drell, P. S.; Favuzzi, C.; Fegan, S. J.; Ferrara, E. C.; Finke, J.; Fusco, P.; Gargano, F.; Gasparrini, D.; Giglietto, N.; Giordano, F.; Giroletti, M.; Green, D.; Grenier, I. A.; Guiriec, S.; Horan, D.; Jóhannesson, G.; Katsuragawa, M.; Kuss, M.; Larsson, S.; Latronico, L.; Li, J.; Li, L.; Longo, F.; Loparco, F.; Lovellette, M. N.; Lubrano, P.; Magill, J.; Maldera, S.; Manfreda, A.; Mayer, M.; 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.; Okada, C.; Orlando, E.; Paneque, D.; Pesce-Rollins, M.; Piron, F.; Pivato, G.; Porter, T. A.; Rainò, S.; Rando, R.; Razzano, M.; Reimer, O.; Rau, A.; Romani, R. W.; Schady, P.; Sgrò, C.; Simone, D.; Siskind, E. J.; Spada, F.; Spandre, G.; Spinelli, P.; Stern, D.; Takahashi, H.; Thayer, J. B.; Torres, D. F.; Tosti, G.; Troja, E.; Vianello, G.; Wood, K. S.; Wood, M.

    2016-03-01

    We have collected broadband spectral energy distributions (SEDs) of three BL Lac objects 3FGL J0022.1-1855 (z = 0.689), 3FGL J0630.9-2406 (z\\quad ≳ 1.239), and 3FGL J0811.2-7529 (z = 0.774), detected by Fermi with relatively flat gigaelectronvolt spectra. By observing simultaneously in the near-infrared to hard X-ray band, we can well characterize the high end of the synchrotron component of the SED. Thus, fitting the SEDs to synchro-Compton models of the dominant emission from the relativistic jet, we can constrain the underlying particle properties and predict the shape of the gigaelectronvolt Compton component. Standard extragalactic background light (EBL) models explain the high-energy absorption well, with poorer fits for high-ultraviolet models. The fits show clear evidence for EBL absorption in the Fermi spectrum of our highest-redshift source 3FGL J0630.9-2406. While synchrotron self-Compton models adequately describe the SEDs, the situation may be complicated by possible external Compton components. For 3FGL J0811.2-7529, we also discover a nearby serendipitous source in the X-ray data, which is almost certainly another lower synchrotron peak frequency ({ν }{{pk}}{{sy}}) BL Lac, that may contribute flux in the Fermi band. Since our sources are unusual high-luminosity, moderate {ν }{{pk}}{{sy}} BL Lacs, we compare these quantities and the Compton dominance, the ratio of peak inverse Compton to peak synchrotron luminosities ({L}{{pk}}{{IC}}/{L}{{pk}}{{sy}}), with those of the full Fermi BL Lac population.

  19. 4U1722 + 11 - The discovery of an X-ray selected BL Lac object

    NASA Technical Reports Server (NTRS)

    Griffiths, R. E.; Wilson, A. S.; Ward, M. J.; Tapia, S.; Ulvestad, J. S.

    1989-01-01

    The Uhuru X-ray source 4U1722 + 11 was observed using the microchannel-plate detector (High Resolution Imager) on the Einstein Observatory, and its coordinates measured to a precision of about 5 arcsec. A 16th-magnitude stellar object within the error circle was observed spectroscopically at CTIO, and at the AAT, and found to have a featureless continuum. Subsequent radio observations at the VLA have established that the object is a radio source at the level of 60 mJy, and optical polarization measurements have determined that the source exhibits variable polarization at the level of 10 percent. On the basis of these observations, it is concluded that 4U1722 + 11 is a member of the class of objects known as X-ray selected blazars of BL Lac objects.

  20. Fermi LAT Detection of a Gamma-ray Flare from the BL Lac Object ON 246

    NASA Astrophysics Data System (ADS)

    Becerra, Josefa

    2015-06-01

    The Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope has observed increasing gamma-ray flux from a source positionally consistent with the BL Lac object ON 246 (RA=187.55871 deg, Dec=25.30198 deg, J2000, Beasley et al. 2002, ApJS, 141, 13; with redshift z=0.135, Nass et al. 1996, A&A, 309, 419), also known as S3 1227+25 and 3FGL J1230.3+2519 (3FGL; Acero et al. 2015, arXiv:1501.02003).

  1. The Long-term Light Variation of BL Lac Object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Yuan, Y. H.; Liu, F. Q.

    2013-09-01

    In this paper, the long-term observations of Tuorla Observatory in Finland are collected. The power spectrum, the DCF (Discrete Correlation Function) method, and the Jurkevich method are used to analyze the periodicity. The results show that the periodicity of BL Lac Object 1ES 1959+650 is P=1.4±0.3 yr. Considering that there is a relation between the origin of periodicity and accretion disk, we use this periodicity to obtain the unstable region lying at R=9.65R_{g}}, where R_{g} represents the Schwarzschild radius.

  2. The Long-term Light Variation of BL Lac Object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Yuan, Yu-hai; Liu, Fu-qing

    2014-07-01

    According to the data of optical observations of the Tuorla Observatory in Finland, using the power spectrum method, DCF (Discrete Correlation Function) method, and Jurkevich method, respectively, we analyzed the periodicity of the long-term light variation of the BL Lac object 1ES 1959+650, and obtained its light period to be P =1.4±0.3 yr. Assuming that the origin of the periodicity is concerned with the accretion disk, we obtained the region where the instability of this source occurs being R =9.65 Rg, here Rg represents the Schwarzschild radius.

  3. An Analysis of Periodic Components in BL Lac Object S5 0716 +714 with MUSIC Method

    NASA Astrophysics Data System (ADS)

    Tang, J.

    2012-01-01

    Multiple signal classification (MUSIC) algorithms are introduced to the estimation of the period of variation of BL Lac objects.The principle of MUSIC spectral analysis method and theoretical analysis of the resolution of frequency spectrum using analog signals are included. From a lot of literatures, we have collected a lot of effective observation data of BL Lac object S5 0716 + 714 in V, R, I bands from 1994 to 2008. The light variation periods of S5 0716 +714 are obtained by means of the MUSIC spectral analysis method and periodogram spectral analysis method. There exist two major periods: (3.33±0.08) years and (1.24±0.01) years for all bands. The estimation of the period of variation of the algorithm based on the MUSIC spectral analysis method is compared with that of the algorithm based on the periodogram spectral analysis method. It is a super-resolution algorithm with small data length, and could be used to detect the period of variation of weak signals.

  4. HESS J1943+213: A Non-classical High-frequency-peaked BL Lac Object

    NASA Astrophysics Data System (ADS)

    Straal, S. M.; Gabányi, K. É.; van Leeuwen, J.; Clarke, T. E.; Dubner, G.; Frey, S.; Giacani, E.; Paragi, Z.

    2016-05-01

    HESS J1943+213 is an unidentified TeV source that is likely a high-frequency-peaked BL Lac (HBL) object, but that is also compatible with a pulsar wind nebula (PWN) nature. Each of these enormously different astronomical interpretations is supported by some of the observed unusual characteristics. In order to finally classify and understand this object, we took a three-pronged approach, through time-domain, high angular resolution, and multi-frequency radio studies. First, our deep time-domain observations with the Arecibo telescope failed to uncover the putative pulsar powering the proposed PWN. We conclude with ˜70% certainty that HESS J1943+213 does not host a pulsar. Second, long-baseline interferometry of the source with e-MERLIN at 1.5 and 5 GHz shows only a core, that is, a point source at ˜ 1–100 mas resolution. Its 2013 flux density is about one-third lower than that detected in the 2011 observations with similar resolution. This radio variability of the core strengthens the HBL object hypothesis. Third, additional evidence against the PWN scenario comes from the radio spectrum we compiled. The extended structure follows a power-law behavior with spectral index α \\=\\-0.54+/- 0.04 while the core component displays a flat spectrum (α \\=\\-0.03+/- 0.03). In contrast, the radio synchrotron emission of PWNe predicts a single power-law distribution. Overall, we rule out the PWN hypothesis and conclude that the source is a BL Lac object. The consistently high fraction (70%) of the flux density from the extended structure then leads us to conclude that HESS J1943+213 must be a non-classical HBL object.

  5. HESS J1943+213: A Non-classical High-frequency-peaked BL Lac Object

    NASA Astrophysics Data System (ADS)

    Straal, S. M.; Gabányi, K. É.; van Leeuwen, J.; Clarke, T. E.; Dubner, G.; Frey, S.; Giacani, E.; Paragi, Z.

    2016-05-01

    HESS J1943+213 is an unidentified TeV source that is likely a high-frequency-peaked BL Lac (HBL) object, but that is also compatible with a pulsar wind nebula (PWN) nature. Each of these enormously different astronomical interpretations is supported by some of the observed unusual characteristics. In order to finally classify and understand this object, we took a three-pronged approach, through time-domain, high angular resolution, and multi-frequency radio studies. First, our deep time-domain observations with the Arecibo telescope failed to uncover the putative pulsar powering the proposed PWN. We conclude with ∼70% certainty that HESS J1943+213 does not host a pulsar. Second, long-baseline interferometry of the source with e-MERLIN at 1.5 and 5 GHz shows only a core, that is, a point source at ∼ 1–100 mas resolution. Its 2013 flux density is about one-third lower than that detected in the 2011 observations with similar resolution. This radio variability of the core strengthens the HBL object hypothesis. Third, additional evidence against the PWN scenario comes from the radio spectrum we compiled. The extended structure follows a power-law behavior with spectral index α \\=\\-0.54+/- 0.04 while the core component displays a flat spectrum (α \\=\\-0.03+/- 0.03). In contrast, the radio synchrotron emission of PWNe predicts a single power-law distribution. Overall, we rule out the PWN hypothesis and conclude that the source is a BL Lac object. The consistently high fraction (70%) of the flux density from the extended structure then leads us to conclude that HESS J1943+213 must be a non-classical HBL object.

  6. POWERFUL HIGH-ENERGY EMISSION OF THE REMARKABLE BL Lac OBJECT S5 0716+714

    SciTech Connect

    Vittorini, V.; Chen, A. W.; Ferrari, A.; Tavani, M.; D'Ammando, F.; Donnarumma, I.; Pacciani, L.; Pucella, G.; Bulgarelli, A.; Colafrancesco, S.; Giommi, P.

    2009-12-01

    BL Lac objects of the intermediate subclass (IBLs) are known to emit a substantial fraction of their power in the energy range 0.1-10 GeV. Detecting gamma-ray emission from such sources provides therefore a direct probe of the emission mechanisms and of the underlying powerhouse. The gamma-ray satellite, AGILE, detected the remarkable IBL S5 0716+714 (z approx = 0.3) during a high state in the period from 2007 September-October, marked by two very intense flares reaching peak fluxes of 200 x 10{sup -8} photons cm{sup -2} s{sup -1} above 100 MeV, with simultaneous optical and X-ray observations. We present here a theoretical model for the two major flares and discuss the overall energetics of the source. We conclude that 0716+714 is among the brightest BL Lac's ever detected at gamma-ray energies. Because of its high power and lack of signs for ongoing accretion or surrounding gas, the source is an ideal candidate to test the maximal power extractable from a rotating supermassive black hole via the pure Blandford-Znajek (BZ) mechanism. We find that during the 2007 gamma-ray flares 0716+714 approached or just exceeded the upper limit set by BZ for a black hole of mass 10{sup 9} M{sub sun}.

  7. Analysis of Optical Variations of BL Lac Object AO 0235+164

    NASA Astrophysics Data System (ADS)

    Hong-tao, Wang

    2014-03-01

    Historical optical BVRI band data are combined on the BL Lac object AO 0235 + 164. In order to examine the possible existence of lags and correlations between variations in different optical bands from this source, a statistical analysis is performed through the Discrete Correlation Function (DCF) method. Monte Carlo simulations called Flux Redistribution/Random Subset Selection (FR/RSS) are performed to obtain statistically meaningful values for the cross-correlation time lags and their related uncertainties. The analysis confirms that the variations in different optical light curves are strongly correlated, with no or very weak lag within the errors. Long term variability of color indices are also analysed. No color variabilities are found.

  8. IUE observations of extragalactic objects

    NASA Technical Reports Server (NTRS)

    Boksenberg, A.; Snijders, M. A. J.; Wilson, R.; Benvenuti, P.; Clavell, J.; Macchetto, F.; Penston, M.; Boggess, A.; Gull, T. R.; Gondhalekar, P.

    1978-01-01

    During the commissioning phase of IUE several extragalactic objects were observed spectrally at low dispersion in the UV range lambda lambda 1150-3200: the Seyfert galaxies NGC4151 and NGC1068, the QSO 3C273, the BL Lacertae object B2 1101+38, the giant elliptical galaxy M87 and the spiral galaxy M81. The results obtained are presented and a preliminary analysis given for all six objects, discussing the continuous spectrum, extinction, emission line spectrum and absorption line spectrum, where possible for each case. Several new or confirmatory astrophysical results are obtained.

  9. A hadronic origin for ultra-high-frequency-peaked BL Lac objects

    NASA Astrophysics Data System (ADS)

    Cerruti, M.; Zech, A.; Boisson, C.; Inoue, S.

    2015-03-01

    Current Cherenkov telescopes have identified a population of ultra-high-frequency peaked BL Lac objects (UHBLs), also known as extreme blazars, that exhibit exceptionally hard TeV spectra, including 1ES 0229+200, 1ES 0347-121, RGB J0710+591, 1ES 1101-232, and 1ES 1218+304. Although one-zone synchrotron-self-Compton (SSC) models have been generally successful in interpreting the high-energy emission observed in other BL Lac objects, they are problematic for UHBLs, necessitating very large Doppler factors and/or extremely high minimum Lorentz factors of the emitting leptonic population. In this context, we have investigated alternative scenarios where hadronic emission processes are important, using a newly developed (lepto-)hadronic numerical code to systematically explore the physical parameters of the emission region that reproduces the observed spectra while avoiding the extreme values encountered in pure SSC models. Assuming a fixed Doppler factor δ = 30, two principal parameter regimes are identified, where the high-energy emission is due to: (1) proton-synchrotron radiation, with magnetic fields B ˜ 1-100 G and maximum proton energies Ep; max ≲ 1019 eV; and (2) synchrotron emission from p-γ-induced cascades as well as SSC emission from primary leptons, with B ˜ 0.1-1 G and Ep; max ≲ 1017 eV. This can be realized with plausible, sub-Eddington values for the total (kinetic plus magnetic) power of the emitting plasma, in contrast to hadronic interpretations for other blazar classes that often warrant highly super-Eddington values.

  10. The Gamma-Ray Bright BL Lac Object RX J1211+2242

    NASA Technical Reports Server (NTRS)

    Beckmann, V.; Favre, P.; Tavecchio, F.; Bussien, T.; Fliri, J.; Wolter, A.

    2004-01-01

    RX J1211+2242 is an optically faint (B approximately equal to 19.2mag) but X-ray bright (f2-10kev = 5 x l0(exp -12)erg per square centimeter per second) AGN, which has been shown to be a BL Lac object at redshift z = 0.455. The ROSAT X-ray, Calar Alto optical, and NVSS radio data suggest that the peak of the synchrotron emission of this object is at energies as high as several keV. BeppoSAX observations have been carried out simultaneously with optical observations in order to extend the coverage to higher energies. The new data indeed indicate a turn-over in the 2 - 10keV energy region. We propose that RX J1211+2242 is the counterpart of the unidentified EGRET source 3EG J1212+2304, making it a gamma-ray emitter with properties similar to, for example, Markarian 501 in its bright state, though being at a much larger distance.

  11. Are some BL Lacs artefacts of gravitational lensing?

    PubMed

    Ostriker, J P; Vietri, M

    1990-03-01

    WE suggested in 1985 that a significant fraction of BL Lacertae objects, a kind of lineless quasar, seen in nearby galaxies are in fact images, gravitationally lensed and substantially amplified by stars in the nearby galaxy, of background objects, optically violent variable (OVV) quasars at redshifts z > 1 (ref. 1). This hypothesis was made on the basis of certain general similarities between BL Lacs and O Ws, but for two recently observed BL Lacs(2,3) a strong case can be made that the accompanying elliptical galaxy is a foreground object. In addition, we argue that the distribution of BL Lac redshifts is hard to understand without gravitational lensing, unless we happen to be at a very local maximum of the spatial cosmic distribution of BL Lacs. Our analysis also indicates that the galaxies whose stars are likely to act as microlenses will be found in two peaks, one nearby, with redshift 0.05-0.10, and the other near the distant quasar. PMID:18278021

  12. Rapid Tev Gamma-ray Variability Of Bl Lac

    NASA Astrophysics Data System (ADS)

    Feng, Qi

    2011-09-01

    Recent VERITAS observations of BL Lacertae revealed rapid gamma-ray flaring of the object at TeV energies (Ong, 2011, ATel #3459). Here, we present preliminary results from the observations. The flaring activity was observed during a 20-minute exposure, when the flux above 200 GeV reached a peak of about 3x10^-6 m^-2s^-1 (roughly one and a half times the Crab Nebula flux). The light curve shows that the observations missed the rising phase of the flare but covered the decaying phase almost in its entirety. The decay time of the flare is about 4 minutes, making it one of the most rapid gamma-ray flares seen for any TeV blazars. Compared to several other blazars that are known to produce gamma-ray flares on a timescale of minutes, BL Lacertae produces the bulk of its radiation at much lower frequencies. The measured gamma-ray spectrum appears to be as soft as that of the non-flaring state, when compared with the published MAGIC spectrum of the source. We will discuss the implications of the results. VERITAS research is supported by grants from the U.S. Department of Energy, the U.S. National Science Foundation, the Smithsonian Institution, by NSERC in Canada, by STFC in the U.K. and by Science Foundation Ireland.

  13. BL LAC OBJECT PKS B1144-379: AN EXTREME SCINTILLATOR

    SciTech Connect

    Turner, R. J.; Ellingsen, S. P.; Shabala, S. S.; Blanchard, J.; Lovell, J. E. J.; McCallum, J. N.; Cimo, G.

    2012-08-01

    Rapid variability in the radio flux density of the BL Lac object PKS B1144-379 has been observed at four frequencies, ranging from 1.5 to 15 GHz, with the Very Large Array and the University of Tasmania's Ceduna antenna. Intrinsic and line-of-sight effects were examined as possible causes of this variability, with interstellar scintillation best explaining the frequency dependence of the variability timescales and modulation indices. This scintillation is consistent with a compact source 20-40 {mu}as or 0.15-0.3 pc in size. The inferred brightness temperature for PKS B1144-379 (assuming that the observed variations are due to scintillation) is 6.2 Multiplication-Sign 10{sup 12} K at 4.9 GHz, with approximately 10% of the total flux in the scintillating component. We show that scintillation surveys aimed at identifying variability timescales of days to weeks are an effective way to identify the active galactic nuclei with the highest brightness temperatures.

  14. Dust in BL Lac objects and Fanaroff-Riley radio galaxies: infrared region

    NASA Astrophysics Data System (ADS)

    Seal Braun, P.

    2015-12-01

    Here 28 BL Lac objects, 18 FR I type radio galaxies, 4 FR I/II type radio galaxies and 10 FR II type radio galaxies are studied from FIR (far infrared) to optical region (180 μm to 0.44 μm) to understand the nature of infrared emission from these objects and the physical properties of dust in the emitting region. Using the flux densities from 2MASS, IRAS, ISO, SCUBA (40 % samples), WISE All-sky Data, AKARI (10 % samples) data and optical (B) observations, the spectral energy distributions are constructed. FIR and NIR spectral indices (α_{FIR} and α_{NIR}) are estimated. The dust temperatures and dust masses of all the samples are estimated from FIR flux densities. The SEDs of most of the samples (90 %) show steep slopes from FIR to optical region and about 10 % of the samples show flat continuous spectra from FIR to NIR region. The SEDs of 80 % FR I type radio galaxies and 1 out of 4 FR I/II type radio galaxies and two RBLs show a bump in the NIR to optical region. The SEDs of these sources are compared with Radiative transfer models. From FIR to MIR region, the SEDs of 90 % of the objects studied here can be fitted to the models with luminosities L˜ 10^{9.5} L0, considering uncertainty from 10 % to 20 %. But the observable fluxes in the NIR region are higher and can be fitted to other models with higher L˜ 10^{12.5} L0. Since there is a difference in emission in NIR region, mainly for FR I radio galaxies, so the variation of apparent K magnitudes with logarithm of redshift z is also studied. The WISE colours, (W1 - W2) and (W2 - W3) are compared with isodensity contours. Comparing with radiative transfer models it can be suggested that, in the FIR and MIR region the infrared emission is from the dust containing large grains, small graphites and PAHs at temperature ˜50 K-100 K. In the NIR region hot dust is mainly due to small grains at temperature ˜1200 K and the emission is mainly from synchrotron radiation produced in the inner part of the relativistic

  15. VERITAS OBSERVATIONS OF THE BL LAC OBJECT PG 1553+113

    SciTech Connect

    Aliu, E.; Archer, A.; Beilicke, M.; Buckley, J. H.; Bugaev, V.; Aune, T.; Barnacka, A.; Behera, B.; Chen, X.; Benbow, W.; Cerruti, M.; Berger, K.; Bird, R.; Byrum, K.; Cardenzana, J. V; Dickinson, H. J.; Ciupik, L.; Connolly, M. P.; Cui, W.; Dumm, J.; and others

    2015-01-20

    We present results from VERITAS observations of the BL Lac object PG 1553+113 spanning the years 2010, 2011, and 2012. The time-averaged spectrum, measured between 160 and 560 GeV, is well described by a power law with a spectral index of 4.33 ± 0.09. The time-averaged integral flux above 200 GeV measured for this period was (1.69 ± 0.06) × 10{sup –11} photons cm{sup –2} s{sup –1}, corresponding to 6.9% of the Crab Nebula flux. We also present the combined γ-ray spectrum from the Fermi Large Area Telescope and VERITAS covering an energy range from 100 MeV to 560 GeV. The data are well fit by a power law with an exponential cutoff at 101.9 ± 3.2 GeV. The origin of the cutoff could be intrinsic to PG 1553+113 or be due to the γ-ray opacity of our universe through pair production off the extragalactic background light (EBL). Given lower limits to the redshift of z > 0.395 based on optical/UV observations of PG 1553+113, the cutoff would be dominated by EBL absorption. Conversely, the small statistical uncertainties of the VERITAS energy spectrum have allowed us to provide a robust upper limit on the redshift of PG 1553+113 of z ≤ 0.62. A strongly elevated mean flux of (2.50 ± 0.14) × 10{sup –11} photons cm{sup –2} s{sup –1} (10.3% of the Crab Nebula flux) was observed during 2012, with the daily flux reaching as high as (4.44±0.71)×10{sup −11} photons cm{sup −2} s{sup −1} (18.3% of the Crab Nebula flux) on MJD 56048. The light curve measured during the 2012 observing season is marginally inconsistent with a steady flux, giving a χ{sup 2} probability for a steady flux of 0.03%.

  16. Unusual optical quiescence of the classical BL Lac object PKS 0735+178 on intranight time-scale

    NASA Astrophysics Data System (ADS)

    Goyal, Arti; Gopal-Krishna; Anupama, G. C.; Sahu, D. K.; Sagar, R.; Britzen, S.; Karouzos, M.; Aller, M. F.; Aller, H. D.

    2009-11-01

    We present the result of our extensive intranight optical monitoring of the well-known low-energy peaked BL Lac (LBL) object PKS 0735+178. This long-term follow-up consists of R-band monitoring for a minimum duration of ~4 hours, on 17 nights spanning 11 years (1998-2008). Using the CCD as an N-star photometer, a detection limit of around 1 per cent was attained for the intranight optical variability (INOV). Remarkably, an INOV amplitude of >=3 per cent on hour-like time-scale was not observed on any of the 17 nights, even though the likelihood of a typical LBL showing such INOV levels in a single session of >~4 hours duration is known to be high (~50 per cent). Our observations have thus established a peculiar long-term INOV quiescence of this radio-selected BL Lac object. Moreover, the access to unpublished optical monitoring data of similarly high sensitivity, acquired in another programme, has allowed us to confirm the same anomalous INOV quiescence of this LBL all the way back to 1989, the epoch of its historically largest radio outburst. Here, we present observational evidence revealing the very unusual INOV behaviour of this classical BL Lac object and discuss this briefly in the context of its other known exceptional properties.

  17. Fermi and Swift observations of correlated outburst activity from the BL Lac object OT 081 (PKS 1749+096)

    NASA Astrophysics Data System (ADS)

    Ciprini, Stefano; Gonzalez, Josefa Becerra; Pivato, Giovanna; Thompson, David J.

    2016-07-01

    We report a strong multi-wavelength outburst in the BL Lac object OT 081 (also known as PKS 1749+096, 4C +09.57) with the radio counterpart position R.A.: 267.88674 deg, Dec.: 9.65020 deg (J2000.0, Lanyi et al. 2010, AJ, 139, 1695) and with redshift z=0.322 (Stickel, Fried, Kuehr 1988, A & A, 191, 16). Gamma ray and X-ray flares reached peaks during the interval 2016 July 16 and 20 simultaneous with an optical outburst (Balonek et al, 2016, ATel #9259).

  18. Fermi-LAT detection of a GeV gamma-ray flare from the BL Lac object OT 081

    NASA Astrophysics Data System (ADS)

    Becerra Gonzalez, J.; Thompson, D.; Fermi-LAT Collaboration

    2016-07-01

    The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with the BL Lac object OT 081 (also known as PKS 1749+096, 4C 09.57, 0FGL J1751.5+0935, 1FGL J1751.5+0937, 2FGL J1751.5+0938, 1FHL J1751.5+0938, 3FGL J1751.5+0939), with the radio counterpart position R.A.: 267.88674 deg, Dec.: 9.65020 deg (J2000.0, Lanyi et al. 2010, AJ, 139, 1695).

  19. An Analysis of Light Periods of BL Lac Object S5 0716+714 with the MUSIC Algorithm

    NASA Astrophysics Data System (ADS)

    Tang, Jie

    2012-07-01

    The multiple signal classification (MUSIC) algorithm is introduced to the estimation of light periods of BL Lac objects. The principle of the MUSIC algorithm is given, together with a testing on its spectral resolution by using a simulative signal. From a lot of literature, we have collected a large number of effective observational data of the BL Lac object S5 0716+714 in the three optical wavebands V, R, and I from 1994 to 2008. The light periods of S5 0716+714 are obtained by means of the MUSIC algorithm and average periodogram algorithm, respectively. It is found that there exist two major periodic components, one is the period of (3.33±0.08) yr, another is the period of (1.24±0.01) yr. The comparison of the performances of periodicity analysis of two algorithms indicates that the MUSIC algorithm has a smaller requirement on the sample length, as well as a good spectral resolution and anti-noise ability, to improve the accuracy of periodicity analysis in the case of short sample length.

  20. EVN Observations of HESS J1943+213: Evidence for an Extreme TeV BL Lac Object

    NASA Astrophysics Data System (ADS)

    Akiyama, Kazunori; Stawarz, Łukasz; Tanaka, Yasuyuki T.; Nagai, Hiroshi; Giroletti, Marcello; Honma, Mareki

    2016-06-01

    We report on the 1.6 GHz (18 cm) very long baseline interferometry (VLBI) observations of the unresolved, steady TeV source HESS J1943+213 located in the Galactic plane, performed with the European VLBI Network (EVN) in 2014. Our new observations with a nearly full EVN array provide the deepest image of HESS J1943+213 at the highest resolution ever achieved, enabling us to resolve the long-standing issues of the source identification. The milliarcsecond-scale structure of HESS J1943+213 has a clear asymmetric morphology consisting of a compact core and a diffuse jet-like tail. This is broadly consistent with the previous e-EVN observations of the source performed in 2011 and re-analyzed in this work. The core component is characterized by the brightness temperature of ≳ 1.8× {10}9 K, which is typical for low-luminosity blazars in general. Overall, the radio properties of HESS J1943+213 are consistent with the source classification as an “extreme high-frequency-peaked BL Lac object.” Remarkably, we note that because HESS J1943+213 does not reveal any optical or infrared signatures of the active galactic nucleus activity, it would never be recognized and identified as a BL Lac object if not for its location close to the Galactic plane where the High Energy Stereoscopic System surveyed for and the follow-up dedicated X-ray and radio studies triggered by the source detection in the TeV range. Our results suggest, therefore, a presence of an unrecognized, possibly very numerous population of particularly extreme HBLs and simultaneously demonstrate that the low-frequency VLBI observations with high angular resolution are indispensable for a proper identification of such objects.

  1. Active Galactic Nuclei, Quasars, BL Lac Objects and X-Ray Background

    NASA Technical Reports Server (NTRS)

    Mushotzky, Richard (Technical Monitor); Elvis, Martin

    2005-01-01

    The XMM COSMOS survey is producing the large surface density of X-ray sources anticipated. The first batch of approx. 200 sources is being studied in relation to the large scale structure derived from deep optical/near-IR imaging from Subaru and CFHT. The photometric redshifts from the opt/IR imaging program allow a first look at structure vs. redshift, identifying high z clusters. A consortium of SAO, U. Arizona and the Carnegie Institute of Washington (Pasadena) has started a large program using the 6.5meter Magellan telescopes in Chile with the prime objective of identifying the XMM X-ray sources in the COSMOS field. The first series of observing runs using the new IMACS multi-slit spectrograph on Magellan will take place in January and February of 2005. Some 300 spectra per field will be taken, including 70%-80% of the XMM sources in each field. The four first fields cover the center of the COSMOS field. A VLT consortium is set to obtain bulk redshifts of the field galaxies. The added accuracy of the spectroscopic redshifts over the photo-z's will allow much lower density structures to be seen, voids and filaments. The association of X-ray selected AGNs, and quasars with these filaments, is a major motivation for our studies. Comparison to the deep VLA radio data now becoming available is about to begin.

  2. Multi-wavelength study of flaring activity in BL Lac object S5 0716+714 during the 2015 outburst

    SciTech Connect

    Chandra, Sunil; Zhang, Haocheng; Kushwaha, Pankaj; Singh, K. P.; Bottcher, M.; Kaur, Navpreet; Baliyan, K. S.

    2015-08-17

    We present a detailed investigation of the flaring activity observed from a BL Lac object, S5 0716+714 , during its brightest ever optical state in the second half of 2015 January. Observed almost simultaneously in the optical, X-rays, and γ-rays, a significant change in the degree of optical polarization (PD) and a swing in the position angle (PA) of polarization were recorded. A TeV (VHE) detection was also reported by the MAGIC consortium during this flaring episode. Two prominent sub-flares, peaking about five days apart, were seen in almost all of the energy bands. The multi-wavelength light curves, spectral energy distribution, and polarization are modeled using the time-dependent code developed by Zhang et al. This model assumes a straight jet threaded by large-scale helical magnetic fields taking into account the light travel time effects, incorporating synchrotron flux and polarization in 3D geometry. Furthermore, the rapid variation in PD and rotation in PA are most likely due to reconnections happening in the emission region in the jet, as suggested by the change in the ratio of toroidal to poloidal components of the magnetic field during the quiescent and flaring states.

  3. Multi-wavelength study of flaring activity in BL Lac object S5 0716+714 during the 2015 outburst

    DOE PAGESBeta

    Chandra, Sunil; Zhang, Haocheng; Kushwaha, Pankaj; Singh, K. P.; Bottcher, M.; Kaur, Navpreet; Baliyan, K. S.

    2015-08-17

    We present a detailed investigation of the flaring activity observed from a BL Lac object, S5 0716+714 , during its brightest ever optical state in the second half of 2015 January. Observed almost simultaneously in the optical, X-rays, and γ-rays, a significant change in the degree of optical polarization (PD) and a swing in the position angle (PA) of polarization were recorded. A TeV (VHE) detection was also reported by the MAGIC consortium during this flaring episode. Two prominent sub-flares, peaking about five days apart, were seen in almost all of the energy bands. The multi-wavelength light curves, spectral energymore » distribution, and polarization are modeled using the time-dependent code developed by Zhang et al. This model assumes a straight jet threaded by large-scale helical magnetic fields taking into account the light travel time effects, incorporating synchrotron flux and polarization in 3D geometry. Furthermore, the rapid variation in PD and rotation in PA are most likely due to reconnections happening in the emission region in the jet, as suggested by the change in the ratio of toroidal to poloidal components of the magnetic field during the quiescent and flaring states.« less

  4. Multi-wavelength Study of Flaring Activity in BL Lac Object S5 0716+714 during the 2015 Outburst

    NASA Astrophysics Data System (ADS)

    Chandra, Sunil; Zhang, Haocheng; Kushwaha, Pankaj; Singh, K. P.; Bottcher, M.; Kaur, Navpreet; Baliyan, K. S.

    2015-08-01

    We present a detailed investigation of the flaring activity observed from a BL Lac object, S5 0716+714 , during its brightest ever optical state in the second half of 2015 January. Observed almost simultaneously in the optical, X-rays, and γ-rays, a significant change in the degree of optical polarization (PD) and a swing in the position angle (PA) of polarization were recorded. A TeV (VHE) detection was also reported by the MAGIC consortium during this flaring episode. Two prominent sub-flares, peaking about five days apart, were seen in almost all of the energy bands. The multi-wavelength light curves, spectral energy distribution, and polarization are modeled using the time-dependent code developed by Zhang et al. This model assumes a straight jet threaded by large-scale helical magnetic fields taking into account the light travel time effects, incorporating synchrotron flux and polarization in 3D geometry. The rapid variation in PD and rotation in PA are most likely due to reconnections happening in the emission region in the jet, as suggested by the change in the ratio of toroidal to poloidal components of the magnetic field during the quiescent and flaring states.

  5. On the redshift of the very high-energy gamma-ray BL Lac object S2 0109+22

    NASA Astrophysics Data System (ADS)

    Paiano, S.; Landoni, M.; Falomo, R.; Scarpa, R.; Treves, A.

    2016-05-01

    The determination of the redshift of extragalactic gamma-ray sources is of fundamental importance for the interpretation of their emission models and extragalactic population studies, active galactic nuclei classification schemes, and to study the interaction with the extragalactic background light. Here we focus on the BL Lac S2 0109+22, recently detected at very high energies. We obtained a high signal-to-noise optical spectrum at Gran Telescopio Canarias for the source over the spectral range 4000-10 000 Å, to search for spectral features of the host galaxy and/or of the nuclear source and it was compared with previous observations in order to confirm and/or dispute its redshift determination. We find the S2 0109+22 optical spectrum is well represented by a power-law continuum without any absorption or emission feature of equivalent width >0.1 Å. Based on the new optical spectrum, we are able to set a redshift lower limit z > 0.35, assuming the source is hosted by a massive elliptical galaxy typical for this class of sources. The redshift z = 0.265 proposed in the literature for this object is most probably referred to a r = 18.3 galaxy at 15 arcsec from S2 0109. This galaxy could belong to a group of faint galaxies located at z ˜ 0.26.

  6. HUBBLE/COS OBSERVATIONS OF THE Ly{alpha} FOREST TOWARD THE BL Lac OBJECT 1ES 1553+113

    SciTech Connect

    Danforth, Charles W.; Keeney, Brian A.; Stocke, John T.; Shull, J. Michael; Yao Yangsen

    2010-09-01

    We present new moderate-resolution, far-ultraviolet spectra from the Hubble Space Telescope/Cosmic Origins Spectrograph (HST/COS) of the BL Lac object 1ES 1553+113 covering the wavelength range 1135 A < {lambda} < 1795 A. The data show a smooth continuum with a wealth of narrow (b < 100 km s{sup -1}) absorption features arising in the interstellar medium and intergalactic medium. These features include 41 Ly{alpha} absorbers at 0 < z{sub abs} < 0.43, 14 of which are detected in multiple Lyman lines and 6 of which show absorption in one or more metal lines. We analyze a metal-rich triplet ({Delta}cz {approx} 1000 km s{sup -1}) of Ly{alpha} absorbers at z{sub abs} {approx} 0.188 in which O VI, N V, and C III absorption is detected. Silicon ions (Si III, Si IV) are not detected to fairly strong upper limits and we use the measured Si III/C III upper limit to derive an abundance limit (C/Si) {>=} 4(C/Si){sub sun} for the strongest component of the absorber complex. Galaxy redshift surveys show a number of massive galaxies at approximately the same redshift as this absorption complex, suggesting that it arises in a large-scale galaxy filament. As one of the brightest extragalactic X-ray and {gamma}-ray sources, 1ES 1553+113 is of great interest to the high-energy astrophysics community. With no intrinsic emission or absorption features, 1ES 1553+113 has no direct redshift determination. We use intervening Ly{alpha} absorbers to place a direct limit on the redshift: z{sub em}>0.395 based on a confirmed Ly{alpha}+O VI absorber and z{sub em}>0.433 based on a single-line detection of Ly{alpha}. The current COS data are only sensitive to Ly{alpha} absorbers at z < 0.47, but we present statistical arguments that z{sub em} {approx}< 0.58 (at a 1{sigma} confidence limit) based on the non-detection of any Ly{beta} absorbers at z>0.4.

  7. Fermi LAT detection of increasing GeV gamma-ray activity from the high-energy peaked BL Lac object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Ciprini, Stefano; Fermi Large Area Telescope Collaboration

    2015-10-01

    The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray emission from a source positionally consistent with the very-high energy peaked BL Lac object 1ES 1959+650 (also known as TXS 1959+650 and 3FGL J2000.0+6509, Acero et al. 2015, ApJS 218, 23) with radio coordinates (J2000) R.A.: 299.999384 deg, Dec.: 65.148514 deg (Beasley et al. 2002, ApJS, 141, 13). This source has a redshift z=0.047 (Schachter et al. 1993, ApJ, 412, 541).

  8. Fermi-LAT, FACT, MAGIC and VERITAS detection of increasing gamma-ray activity from the high-energy peaked BL Lac object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Buson, S.; Magill, J. D.; Dorner, D.; Biland, A.; Mirzoyan, R.; Mukherjee, R.

    2016-04-01

    The Fermi-LAT, FACT, MAGIC and VERITAS collaborations report the detection of enhanced gamma-ray activity from a source positionally consistent with the very-high-energy peaked BL Lac object 1ES 1959+650 (a.k.a 3FGL J2000.0+6509, in the 3rd LAT source catalog, 3FGL, Acero et al. 2015, ApJS 218, 23) with radio coordinates (J2000) R.A.: 299.999384 deg, Dec.: 65.148514 deg (Beasley et al. 2002, ApJS, 141, 13). This source has a redshift z=0.047 (Schachter et al. 1993, ApJ, 412, 541).

  9. Fermi LAT detection of the first GeV gamma-ray flare from the BL Lac object TXS 2241+406

    NASA Astrophysics Data System (ADS)

    Buson, Sara

    2015-02-01

    The Large Area Telescope (LAT) onboard the Fermi Gamma-ray Space Telescope, has observed for the first time on daily timescales gamma-ray outburst activity from a source positionally consistent with the BL Lac object TXS 2241+406 (a.k.a.3FGL J2244.1+4057, Acero et al. 2015, arXiv:1501.02003) at RA=341.05305 deg, Dec=40.95378 deg (J2000, Beasley et al. 2002, ApJS, 141, 13) with redshift z=1.171 (Shaw et al. 2012, ApJ, 748, 49).

  10. Fermi-LAT detection of hard spectrum and enhanced gamma-ray emission from the BL Lac object PKS 1717+177

    NASA Astrophysics Data System (ADS)

    Ciprini, Stefano

    2015-12-01

    The Large Area Telescope (LAT), one of two instruments on the Fermi Gamma-ray Space Telescope, has observed a gamma-ray flare from a source positionally consistent with the BL Lac object PKS 1717+177 (also known as S3 1717+17, OT 129, and 3FGL J1719.2+1744, Acero et al. 2015, ApJS, 218, 23), with radio coordinates (J2000.0), R.A.: 259.804368 deg, Dec.: 17.751788 deg (Johnston et al. 1995, AJ, 110, 880).

  11. Systemic L-Kynurenine sulfate administration disrupts object recognition memory, alters open field behavior and decreases c-Fos immunopositivity in C57Bl/6 mice.

    PubMed

    Varga, Dániel; Herédi, Judit; Kánvási, Zita; Ruszka, Marian; Kis, Zsolt; Ono, Etsuro; Iwamori, Naoki; Iwamori, Tokuko; Takakuwa, Hiroki; Vécsei, László; Toldi, József; Gellért, Levente

    2015-01-01

    L-Kynurenine (L-KYN) is a central metabolite of tryptophan degradation through the kynurenine pathway (KP). The systemic administration of L-KYN sulfate (L-KYNs) leads to a rapid elevation of the neuroactive KP metabolite kynurenic acid (KYNA). An elevated level of KYNA may have multiple effects on the synaptic transmission, resulting in complex behavioral changes, such as hypoactivity or spatial working memory deficits. These results emerged from studies that focused on rats, after low-dose L-KYNs treatment. However, in several studies neuroprotection was achieved through the administration of high-dose L-KYNs. In the present study, our aim was to investigate whether the systemic administration of a high dose of L-KYNs (300 mg/bwkg; i.p.) would produce alterations in behavioral tasks (open field or object recognition) in C57Bl/6j mice. To evaluate the changes in neuronal activity after L-KYNs treatment, in a separate group of animals we estimated c-Fos expression levels in the corresponding subcortical brain areas. The L-KYNs treatment did not affect the general ambulatory activity of C57Bl/6j mice, whereas it altered their moving patterns, elevating the movement velocity and resting time. Additionally, it seemed to increase anxiety-like behavior, as peripheral zone preference of the open field arena emerged and the rearing activity was attenuated. The treatment also completely abolished the formation of object recognition memory and resulted in decreases in the number of c-Fos-immunopositive-cells in the dorsal part of the striatum and in the CA1 pyramidal cell layer of the hippocampus. We conclude that a single exposure to L-KYNs leads to behavioral disturbances, which might be related to the altered basal c-Fos protein expression in C57Bl/6j mice. PMID:26136670

  12. Kepler Observations of Rapid Optical Variability in the BL Lac Object W2r192+42

    NASA Technical Reports Server (NTRS)

    R.Edelson; Mushotzky, R.; Vaughn, S.; Scargle, J.; Gandhi, P.; Malkan, M.; Baumgartner, W.

    2013-01-01

    We present the first Kepler monitoring of a strongly variable BL Lac, W2R1926+42. The light curve covers 181 days with approx. 0.2% errors, 30 minute sampling and >90% duty cycle, showing numerous delta-I/I > 25% flares over timescales as short as a day. The flux distribution is highly skewed and non-Gaussian. The variability shows a strong rms-flux correlation with the clearest evidence to date for non-linearity in this relation. We introduce a method to measure periodograms from the discrete autocorrelation function, an approach that may be well-suited to a wide range of Kepler data. The periodogram is not consistent with a simple power-law, but shows a flattening at frequencies below 7x10(exp -5) Hz. Simple models of the power spectrum, such as a broken power law, do not produce acceptable fits, indicating that the Kepler blazar light curve requires more sophisticated mathematical and physical descriptions than currently in use.

  13. Time Series Photometry of KZ Lacertae

    NASA Astrophysics Data System (ADS)

    Joner, Michael D.

    2016-01-01

    We present BVRI time series photometry of the high amplitude delta Scuti star KZ Lacertae secured using the 0.9-meter telescope located at the Brigham Young University West Mountain Observatory. In addition to the multicolor light curves that are presented, the V data from the last six years of observations are used to plot an O-C diagram in order to determine the ephemeris and evaluate evidence for period change. We wish to thank the Brigham Young University College of Physical and Mathematical Sciences as well as the Department of Physics and Astronomy for their continued support of the research activities at the West Mountain Observatory.

  14. MAGIC detection of short-term variability of the high-peaked BL Lac object 1ES 0806+524

    NASA Astrophysics Data System (ADS)

    Aleksić, J.; Ansoldi, S.; Antonelli, L. A.; Antoranz, P.; Babic, A.; Bangale, P.; Barrio, J. A.; Becerra González, J.; Bednarek, W.; Bernardini, E.; Biasuzzi, B.; Biland, A.; Blanch, O.; Bonnefoy, S.; Bonnoli, G.; Borracci, F.; Bretz, T.; Carmona, E.; Carosi, A.; Colin, P.; Colombo, E.; Contreras, J. L.; Cortina, J.; Covino, S.; Da Vela, P.; Dazzi, F.; De Angelis, A.; De Caneva, G.; De Lotto, B.; de Oña Wilhelmi, E.; Delgado Mendez, C.; Di Pierro, F.; Dominis Prester, D.; Dorner, D.; Doro, M.; Einecke, S.; Eisenacher, D.; Elsaesser, D.; Fernández-Barral, A.; Fidalgo, D.; Fonseca, M. V.; Font, L.; Frantzen, K.; Fruck, C.; Galindo, D.; García López, R. J.; Garczarczyk, M.; Garrido Terrats, D.; Gaug, M.; Godinović, N.; González Muñoz, A.; Gozzini, S. R.; Hadasch, D.; Hanabata, Y.; Hayashida, M.; Herrera, J.; Hose, J.; Hrupec, D.; Idec, W.; Kadenius, V.; Kellermann, H.; Knoetig, M. L.; Kodani, K.; Konno, Y.; Krause, J.; Kubo, H.; Kushida, J.; La Barbera, A.; Lelas, D.; Lewandowska, N.; Lindfors, E.; Lombardi, S.; Longo, F.; López, M.; López-Coto, R.; López-Oramas, A.; Lorenz, E.; Lozano, I.; Makariev, M.; Mallot, K.; Maneva, G.; Mannheim, K.; Maraschi, L.; Marcote, B.; Mariotti, M.; Martínez, M.; Mazin, D.; Menzel, U.; Miranda, J. M.; Mirzoyan, R.; Moralejo, A.; Munar-Adrover, P.; Nakajima, D.; Neustroev, V.; Niedzwiecki, A.; Nievas Rosillo, M.; Nilsson, K.; Nishijima, K.; Noda, K.; Orito, R.; Overkemping, A.; Paiano, S.; Palatiello, M.; Paneque, D.; Paoletti, R.; Paredes, J. M.; Paredes-Fortuny, X.; Persic, M.; Poutanen, J.; Prada Moroni, P. G.; Prandini, E.; Puljak, I.; Reinthal, R.; Rhode, W.; Ribó, M.; Rico, J.; Rodriguez Garcia, J.; Saito, T.; Saito, K.; Satalecka, K.; Scalzotto, V.; Scapin, V.; Schultz, C.; Schweizer, T.; Shore, S. N.; Sillanpää, A.; Sitarek, J.; Snidaric, I.; Sobczynska, D.; Stamerra, A.; Steinbring, T.; Strzys, M.; Takalo, L.; Takami, H.; Tavecchio, F.; Temnikov, P.; Terzić, T.; Tescaro, D.; Teshima, M.; Thaele, J.; Torres, D. F.; Toyama, T.; Treves, A.; Vogler, P.; Will, M.; Zanin, R.; Berger, K.; Buson, S.; D'Ammando, F.; Gasparrini, D.; Hovatta, T.; Max-Moerbeck, W.; Readhead, A.; Richards, J.

    2015-07-01

    The high-frequency-peaked BL Lac (HBL) 1ES 0806+524 (z = 0.138) was discovered in very high energy (VHE) γ-rays in 2008. Until now, the broad-band spectrum of 1ES 0806+524 has been only poorly characterized, in particular at high energies. We analysed multiwavelength observations from γ-rays to radio performed from 2011 January to March, which were triggered by the high activity detected at optical frequencies. These observations constitute the most precise determination of the broad-band emission of 1ES 0806+524 to date. The stereoscopic Major Atmospheric Gamma-Ray Imaging Cherenkov (MAGIC) observations yielded a γ-ray signal above 250 GeV of (3.7 ± 0.7) per cent of the Crab Nebula flux with a statistical significance of 9.9σ. The multiwavelength observations showed significant variability in essentially all energy bands, including a VHE γ-ray flare that lasted less than one night, which provided unprecedented evidence for short-term variability in 1ES 0806+524. The spectrum of this flare is well described by a power law with a photon index of 2.97 ± 0.29 between ˜150 GeV and 1 TeV and an integral flux of (9.3 ± 1.9) per cent of the Crab nebula flux above 250 GeV. The spectrum during the non-flaring VHE activity is compatible with the only available VHE observation performed in 2008 with VERITAS when the source was in a low optical state. The broad-band spectral energy distribution can be described with a one-zone synchrotron self-Compton model with parameters typical for HBLs, indicating that 1ES 0806+524 is not substantially different from the HBLs previously detected.

  15. Fermi and Swift observations of a rapid flare in the BL Lac object SDSS J084411.67+531250.7 (NVSS J084411+531250)

    NASA Astrophysics Data System (ADS)

    Ciprini, Stefano

    2015-04-01

    The Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, has observed increasing gamma-ray flux from a source positionally consistent with the optically-selected and polarized (Smith et al. 2007, ApJ, 663, 118) BL Lac object SDSS J084411.67+531250.7 (also known as NVSS J084411+531250, BZB J0844+5312, and 3FGL J0843.9+5311, Acero et al. 2015, arXiv:1501.02003), with optical counterpart coordinates (J2000.0) R.A.: 131.04872 deg, Dec.: 53.21407 deg (Adelman-McCarthy et. al 2008, ApJS, 175, 297).

  16. X-ray detection of the old nova DK Lacertae

    NASA Astrophysics Data System (ADS)

    Boardman, S. F.; Takei, D.; Drake, J. J.; Sakamoto, T.; Fruscione, A.

    2016-01-01

    We report the detection of the old nova DK Lacertae with Chandra X-Ray Observatory's ACIS-S CCD imaging spectrometer on 3 February 2015. DK Lacertae, located at (J2000) 22:49:46.970 +53:17:19.66, was discovered in 1950 at a brightness of 6 mag (Bertaud, C., 1950, IAUC, 1254, 1). Chandra detected 92.5 +/- 9.6 net counts from the source at a count rate of 0.0306 +/- 0.0032 c/s over an exposure time of 3025.6 s. No significant variability was observed during the length of the observation.

  17. The ultrastructure of the tracheal epithelium in European common lizard (Lacerta agilis L.) and in sand lizard (Lacerta vivipara Jacq.).

    PubMed

    Tĕsík, I

    1984-01-01

    This study describes the ultrastructure of the tracheal epithelium in the European Common lizard (Lacerta agilis L.) and in the Sand lizard (Lacerta vivipara Jacq .). The main attention is paid to the granular cells of secret-producing type, which form the substantial part of this epithelium and which were observed for the first time in the house gekko . Contrary to the findings in house gekko , in the representatives of the genus Lacerta 2 types of electrondense granules were observed. One type is homogeneous and lighter in colour, the other is darker with lamellar pattern. Among other elements, the ciliated cells as well as basal and plasmatic cells were found. In both species we also succeeded in proving the presence of isolated neurosecret -producing cells. PMID:6721200

  18. VERITAS Detection of γ-Ray Flaring Activity From the BL Lac Object 1ES 1727+502 During Bright Moonlight Observations

    NASA Astrophysics Data System (ADS)

    Archambault, S.; Archer, A.; Beilicke, M.; Benbow, W.; Bird, R.; Biteau, J.; Bouvier, A.; Bugaev, V.; Cardenzana, J. V.; Cerruti, M.; Chen, X.; 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.; Fortin, P.; Fortson, L.; Furniss, A.; Gillanders, G. H.; Griffin, S.; Griffiths, S. T.; Grube, J.; Gyuk, G.; Håkansson, N.; Hanna, D.; Holder, J.; Humensky, T. B.; Johnson, C. A.; Kaaret, P.; Kar, P.; Kertzman, M.; Khassen, Y.; Kieda, D.; Krause, M.; Krennrich, F.; Kumar, S.; Lang, M. J.; Maier, G.; McArthur, S.; McCann, A.; Meagher, K.; Millis, J.; Moriarty, P.; Mukherjee, R.; Nieto, D.; O'Faoláin de Bhróithe, A.; Ong, R. A.; Otte, A. N.; Park, N.; Pohl, M.; Popkow, A.; Prokoph, H.; Pueschel, E.; Quinn, J.; Ragan, K.; Reyes, L. C.; Reynolds, P. T.; Richards, G. T.; Roache, E.; Santander, M.; Sembroski, G. H.; Shahinyan, K.; Smith, A. W.; Staszak, D.; Telezhinsky, I.; Tucci, J. V.; Tyler, J.; Varlotta, A.; Vincent, S.; Wakely, S. P.; Weinstein, A.; Welsing, R.; Wilhelm, A.; Williams, D. A.; Zitzer, B.; Veritas Collaboration; Hughes, Z. D.

    2015-08-01

    During moonlit nights, observations with ground-based Cherenkov telescopes at very high energies (VHEs, E\\gt 100 GeV) are constrained since the photomultiplier tubes (PMTs) in the telescope camera are extremely sensitive to the background moonlight. Observations with the VERITAS telescopes in the standard configuration are performed only with a moon illumination less than 35% of full moon. Since 2012, the VERITAS collaboration has implemented a new observing mode under bright moonlight, by either reducing the voltage applied to the PMTs (reduced-high-voltage; RHV configuration), or by utilizing UV-transparent filters. While these operating modes result in lower sensitivity and increased energy thresholds, the extension of the available observing time is useful for monitoring variable sources such as blazars and sources requiring spectral measurements at the highest energies. In this paper we report the detection of γ-ray flaring activity from the BL Lac object 1ES 1727+502 during RHV observations. This detection represents the first evidence of VHE variability from this blazar. The integral flux is (1.1+/- 0.2)× {10}-11 {{cm}}-2 {{{s}}}-1 above 250 GeV, which is about five times higher than the low-flux state. The detection triggered additional VERITAS observations during standard dark-time. Multiwavelength observations with the FLWO 48″ telescope, and the Swift and Fermi satellites are presented and used to produce the first spectral energy distribution (SED) of this object during γ-ray flaring activity. The SED is then fitted with a standard synchrotron-self-Compton model, placing constraints on the properties of the emitting region and of the acceleration mechanism at the origin of the relativistic particle population in the jet.

  19. Long-term spectral and temporal behavior of the high-frequency peaked BL LAC object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Backes, M.; Uellenbeck, M.; Hayashida, M.; Satalecka, K.; Tescaro, D.; Terzić, T.; MAGIC Collaboration; Fuhrmann, L.; Nestoras, I.; F-GAMMA project; Lähteenmäki, A.; Tornikoski, M.; Nieppola, E.; Metsähovi; Böttcher, M.; Collmar, W.; Weidinger, M.

    2012-12-01

    The high-frequency peaked BL Lac object 1ES 1959+650 is well-known for an exceptional outburst, which was observed at very high energy (VHE) γ-rays by the Whipple 10m and HEGRA telescopes in 2002. Remarkably, this outburst lacked associated X-ray emission (a socalled "orphan flare") and by this cannot easily be described by standard Synchrotron Self Compton (SSC) models. Models based on hadronic emission processes have also been proposed to explain the observed behavior. Subsequent multi-wavelength observations during a low flux state at TeV energies in 2006 can, instead, be explained by a standard single-zone SSC model. In this context, 1ES 1959+650 has been regularly monitored by the MAGIC telescope since 2005. During these years, no significant variation in the VHE γ-ray flux has been observed. The low energy part of this is in very good agreement with the high-energy part of the time-integrated energy spectrum as measured by Fermi-LAT. Based on this constant flux level in VHE γ-rays, we assembled the time-integrated spectral energy distribution (SED) of 1ES 1959+650 from radio to VHE γ-rays. Despite the non-variability at very high energies, significant flux and spectral variations have been observed at optical and X-ray frequencies in the meanwhile. Furthermore, the shape of the SED at high energy γ-rays as measured by Fermi-LAT is essentially flat which cannot be explained by either conventional single-zone SSC models, or models invoking external radiation fields (EC).

  20. The WEBT campaign on the BL Lac object PG 1553+113 in 2013. An analysis of the enigmatic synchrotron emission

    NASA Astrophysics Data System (ADS)

    Raiteri, C. M.; Stamerra, A.; Villata, M.; Larionov, V. M.; Acosta-Pulido, J. A.; Arévalo, M. J.; Arkharov, A. A.; Bachev, R.; Benítez, E.; Bozhilov, V. V.; Borman, G. A.; Buemi, C. S.; Calcidese, P.; Carnerero, M. I.; Carosati, D.; Chigladze, R. A.; Damljanovic, G.; Di Paola, A.; Doroshenko, V. T.; Efimova, N. V.; Ehgamberdiev, Sh. A.; Giroletti, M.; González-Morales, P. A.; Grinon-Marin, A. B.; Grishina, T. S.; Hiriart, D.; Ibryamov, S.; Klimanov, S. A.; Kopatskaya, E. N.; Kurtanidze, O. M.; Kurtanidze, S. O.; Kurtenkov, A. A.; Larionova, L. V.; Larionova, E. G.; Lázaro, C.; Lähteenmäki, A.; Leto, P.; Markovic, G.; Mirzaqulov, D. O.; Mokrushina, A. A.; Morozova, D. A.; Mújica, R.; Nazarov, S. V.; Nikolashvili, M. G.; Ohlert, J. M.; Ovcharov, E. P.; Paiano, S.; Pastor Yabar, A.; Prandini, E.; Ramakrishnan, V.; Sadun, A. C.; Semkov, E.; Sigua, L. A.; Strigachev, A.; Tammi, J.; Tornikoski, M.; Trigilio, C.; Troitskaya, Yu. V.; Troitsky, I. S.; Umana, G.; Velasco, S.; Vince, O.

    2015-11-01

    A multifrequency campaign on the BL Lac object PG 1553+113 was organized by the Whole Earth Blazar Telescope (WEBT) in 2013 April-August, involving 19 optical, two near-IR, and three radio telescopes. The aim was to study the source behaviour at low energies during and around the high-energy observations by the Major Atmospheric Gamma-ray Imaging Cherenkov telescopes in April-July. We also analyse the UV and X-ray data acquired by the Swift and XMM-Newton satellites in the same period. The WEBT and satellite observations allow us to detail the synchrotron emission bump in the source spectral energy distribution (SED). In the optical, we found a general bluer-when-brighter trend. The X-ray spectrum remained stable during 2013, but a comparison with previous observations suggests that it becomes harder when the X-ray flux increases. The long XMM-Newton exposure reveals a curved X-ray spectrum. In the SED, the XMM-Newton data show a hard near-UV spectrum, while Swift data display a softer shape that is confirmed by previous Hubble Space Telescope/Cosmic Origins Spectrograph and International Ultraviolet Explorer observations. Polynomial fits to the optical-X-ray SED show that the synchrotron peak likely lies in the 4-30 eV energy range, with a general shift towards higher frequencies for increasing X-ray brightness. However, the UV and X-ray spectra do not connect smoothly. Possible interpretations include: (i) orientation effects, (ii) additional absorption, (iii) multiple emission components, and (iv) a peculiar energy distribution of relativistic electrons. We discuss the first possibility in terms of an inhomogeneous helical jet model.

  1. X-ray intensity and spectral variations in the BL Lac sources H2155-304 and PKS0548-322

    NASA Technical Reports Server (NTRS)

    Agrawal, P. C.; Singh, K. P.; Riegler, G. R.

    1987-01-01

    The results from the X-ray observations of two BL Lacertae objects, H2155-304 and PKS0548-322, are presented. The observations were carried out with the HEAO-1 A2 Low Energy Detectors, the High Resolution Imager, and the Monitor Proportional Counter aboard the Einstein Observatory. Correlated X-ray intensity variations of about 20 percent in the 0.15-3.5 keV energy band and about 40 percent in the 1.5-10 keV energy band are observed in H2155-304 over a period of about 8 hr. A factor of two change in the intensity of PKS0548-322 in the 3.5-10 keV energy interval is also detected over a time interval of 1 hr. Variations in the X-ray intensity over a timescale of months and the hardening of the spectrum with increasing intensity are seen in the HEAO-1 A2 data on H2155-304. The shortest observed timescale for the variability is used to derive an upper limit on the mass of the central accreting source in the two BL Lac objects studied here.

  2. Application of the MST clustering to the high energy γ-ray sky. I—New possible detection of high-energy γ-ray emission associated with BL Lac objects

    NASA Astrophysics Data System (ADS)

    Campana, R.; Massaro, E.; Bernieri, E.; D'Amato, Q.

    2015-12-01

    In this paper we show an application of the Minimum Spanning Tree (MST) clustering method to the high-energy γ-ray sky observed at energies higher than 10 GeV in 6.3 years by the Fermi-Large Area Telescope. We report the detection of 19 new high-energy γ-ray clusters with good selection parameters whose centroid coordinates were found matching the positions of known BL Lac objects in the 5th Edition of the Roma-BZCAT catalogue. A brief summary of the properties of these sources is presented.

  3. Examination of the hippocampal contribution to serotonin 5-HT2A receptor-mediated facilitation of object memory in C57BL/6J mice.

    PubMed

    Zhang, Gongliang; Cinalli, David; Cohen, Sarah J; Knapp, Kristina D; Rios, Lisa M; Martínez-Hernández, José; Luján, Rafael; Stackman, Robert W

    2016-10-01

    The rodent hippocampus supports non-spatial object memory. Serotonin 5-HT2A receptors (5-HT2AR) are widely expressed throughout the hippocampus. We previously demonstrated that the activation of 5-HT2ARs enhanced the strength of object memory assessed 24 h after a limited (i.e., weak memory) training procedure. Here, we examined the subcellular distribution of 5-HT2ARs in the hippocampal CA1 region and underlying mechanisms of 5-HT2AR-mediated object memory consolidation. Analyses with immuno-electron microscopy revealed the presence of 5-HT2ARs on the dendritic spines and shafts of hippocampal CA1 neurons, and presynaptic terminals in the CA1 region. In an object recognition memory procedure that places higher demand on the hippocampus, only post-training systemic or intrahippocampal administration of the 5-HT2AR agonist TCB-2 enhanced object memory. Object memory enhancement by TCB-2 was blocked by the 5-HT2AR antagonist, MDL 11,937. The memory-enhancing dose of systemic TCB-2 increased extracellular glutamate levels in hippocampal dialysate samples, and increased the mean in vivo firing rate of hippocampal CA1 neurons. In summary, these data indicate a pre- and post-synaptic distribution of 5-HT2ARs, and activation of 5-HT2ARs selectively enhanced the consolidation of object memory, without affecting encoding or retrieval. The 5-HT2AR-mediated facilitation of hippocampal memory may be associated with an increase in hippocampal neuronal firing and glutamate efflux during a post-training time window in which recently encoded memories undergo consolidation. PMID:27114257

  4. Doppler imaging of AR Lacertae at three epochs

    NASA Technical Reports Server (NTRS)

    Walter, Frederick M.; Neff, James E.; Linsky, Jeffrey L.; Rodono, Marcello

    1988-01-01

    Observations from IUE were used to study the structure of the lower chromosphere of AR Lacertae in the light of Mg II k. Sequences of LWR/P-HI images distributed around the binary period at three epochs were obtained. Discrete plage-like regions of enhanced Mg II surface flux in this system are identified. There are temporal variations in the Mg II flux on timescales of hours as well as substantial changes in chromospheric morphology on timescales of years. Even with the limited S/N attainable with the IUE, one can map the gross structures of active stellar atmospheres. With such information, one can begin to study the true 3-D structure of the atmospheres of late-type stars.

  5. [Searching for Rare Celestial Objects Automatically from Stellar Spectra of the Sloan Digital Sky Survey Data Release Eight].

    PubMed

    Si, Jian-min; Luo, A-li; Wu, Fu-zhao; Wu, Yi-hong

    2015-03-01

    There are many valuable rare and unusual objects in spectra dataset of Sloan Digital Sky Survey (SDSS) Data Release eight (DR8), such as special white dwarfs (DZ, DQ, DC), carbon stars, white dwarf main-sequence binaries (WDMS), cataclysmic variable (CV) stars and so on, so it is extremely significant to search for rare and unusual celestial objects from massive spectra dataset. A novel algorithm based on Kernel dense estimation and K-nearest neighborhoods (KNN) has been presented, and applied to search for rare and unusual celestial objects from 546 383 stellar spectra of SDSS DR8. Their densities are estimated using Gaussian kernel density estimation, the top 5 000 spectra in descend order by their densities are selected as rare objects, and the top 300 000 spectra in ascend order by their densities are selected as normal objects. Then, KNN were used to classify the rest objects, and simultaneously K nearest neighbors of the 5 000 rare spectra are also selected as rare objects. As a result, there are totally 21 193 spectra selected as initial rare spectra, which include error spectra caused by deletion, redden, bad calibration, spectra consisting of different physically irrelevant components, planetary nebulas, QSOs, special white dwarfs (DZ, DQ, DC), carbon stars, white dwarf main-sequence binaries (WDMS), cataclysmic variable (CV) stars and so on. By cross identification with SIMBAD, NED, ADS and major literature, it is found that three DZ white dwarfs, one WDMS, two CVs with company of G-type star, three CVs candidates, six DC white dwarfs, one DC white dwarf candidate and one BL Lacertae (BL lac) candidate are our new findings. We also have found one special DA white dwarf with emission lines of Ca II triple and Mg I, and one unknown object whose spectrum looks like a late M star with emission lines and its image looks like a galaxy or nebula. PMID:26117907

  6. The BL LAC phenomenon: X-ray observations of transition objects and determination of the x-ray spectrum of a complete sample of flat-spectrum radio sources

    NASA Technical Reports Server (NTRS)

    Worrall, Diana M.

    1994-01-01

    This report summarizes the activities related to two ROSAT investigations: (1) x-ray properties of radio galaxies thought to contain BL Lac type nuclei; and (2) x-ray spectra of a complete sample of flat-spectrum radio sources. The following papers describing the research are provided as attachments: Multiple X-ray Emission Components in Low Power Radio Galaxies; New X-ray Results on Radio Galaxies; Analysis Techniques for a Multiwavelength Study of Radio Galaxies; Separation of X-ray Emission Components in Radio Galaxies; X-ray Emission in Powerful Radio Galaxies and Quasars; Extended and Compact X-ray Emission in Powerful Radio Galaxies; and X-ray Spectra of a Complete Sample of Extragalactic Core-dominated Radio Sources.

  7. Additional photoelectric observations and analysis of the variability of the beta Cephei stars 12 and 16 Lacertae

    NASA Astrophysics Data System (ADS)

    Jarzebowski, T.; Jerzykiewicz, M.; Rios Herrera, M.; Rios Berumen, M.

    1980-04-01

    We present photoelectric observations of two Cephei variables - 12 and 16 Lacertae- made in 1977 in the Observatory of Zacatecas. The results of a frequency analysis made with these data and with the data obtained in the same year at the San Pedro Martir, Chiran and Bialkow Observatories are also given.

  8. Spectroscopy of the Three Distant Andromedan Satellites Cassiopeia III, Lacerta I, and Perseus I

    NASA Astrophysics Data System (ADS)

    Martin, Nicolas F.; Chambers, Kenneth C.; Collins, Michelle L. M.; Ibata, Rodrigo A.; Rich, R. Michael; Bell, Eric F.; Bernard, Edouard J.; Ferguson, Annette M. N.; Flewelling, Heather; Kaiser, Nicholas; Magnier, Eugene A.; Tonry, John L.; Wainscoat, Richard J.

    2014-09-01

    We present Keck II/DEIMOS spectroscopy of the three distant dwarf galaxies of M31 Lacerta I, Cassiopeia III, and Perseus I, recently discovered within the Pan-STARRS1 3π imaging survey. The systemic velocities of the three systems (v r, helio = -198.4 ± 1.1 km s-1, -371.6 ± 0.7 km s-1, and -326 ± 3 km s-1, respectively) confirm that they are satellites of M31. In the case of Lacerta I and Cassiopeia III, the high quality of the data obtained for 126 and 212 member stars, respectively, yields reliable constraints on their global velocity dispersions (σvr = 10.3 ± 0.9 km s-1 and 8.4 ± 0.6 km s-1, respectively), leading to dynamical-mass estimates for both of ~4 × 107 M ⊙ within their half-light radius. These translate to V-band mass-to-light ratios of 15+12-9 and 8+9-5 in solar units. We also use our spectroscopic data to determine the average metallicity of the three dwarf galaxies ([Fe/H] = -2.0 ± 0.1, -1.7 ± 0.1, and -2.0 ± 0.2, respectively). All these properties are typical of dwarf galaxy satellites of Andromeda with their luminosity and size.

  9. One-milliarsecond precision parallax studies in the regions of Delta Cephei and EV Lacertae

    NASA Technical Reports Server (NTRS)

    Gatewood, George; De Jonge, Kiewiet Joost; Stephenson, Bruce

    1993-01-01

    Trigonometric parallaxes for stars in the regions of the variable stars delta Cephei and EV Lacertae are derived from data collected with the Multichannel Astrometric Photometer (MAP) and the Thaw Refractor of the University of Pittsburgh's Allegheny Observatory. The weighted mean parallax of all trigonometric studies of delta Cephei is now + 0.0030 sec + or - 0.00093 sec, corresponding to a distance modulus of 7.61 + or - 0.67 mag. This indicates that this luminosity standard star is approximately one standard deviation more distance than has been generally accepted. The weighted mean trigonometric parallax of all studies of the variable star EV Lacertae (BD + 43 deg 4305) is + 0.1993 sec + or - 0.00093 sec, implying a distance modulus of - 1.498 + or - 0.0010 mag. The calculated absolute magnitude of this star is almost exactly that predicted by its (R-I)(sub Kron) magnitude and by the Gliese (R-I) main-sequence value for stars in the solar neighborhood. We also find a parallax of 0.0189 sec + or - 0.0008 sec for the FO IVn star, HR 8666 (BD + 43 sec 4300). The derived luminosity of this star is midway between that expected for luminosity class IV and V stars at the indicated temperature.

  10. DISCOVERY OF X-RAY EMISSION IN THE OLD CLASSICAL NOVA DK LACERTAE

    SciTech Connect

    Takei, D.; Drake, J. J.; Sakamoto, T.

    2013-01-01

    We report the discovery of X-ray emission at the position of the old classical nova DK Lacertae using the Swift satellite. Three observations were conducted using the X-Ray Telescope 62 years after the discovery of the nova, yielding 46 source signals in an exposure time of 4.8 ks. A background-subtracted count rate was 9 {+-} 2 Multiplication-Sign 10{sup -3} counts s{sup -1}, corresponding to a detection significance level of 5{sigma}. The X-ray spectrum was characterized by a continuum extending up to about 7 keV, which can be modeled by a power-law component with a photon index of 1.4-5.6, or by a thermal bremsstrahlung component with a temperature of 0.7-13.3 keV, convolved with interstellar absorption with an equivalent hydrogen column density of 0.3-2.4 Multiplication-Sign 10{sup 22} cm{sup -2}. Assuming a distance of 3900 pc to the source, the luminosity was 10{sup 32}-10{sup 34} erg s{sup -1} in the 0.3-10 keV energy band. The origin of X-rays is considered to be either mass accretion on the white dwarf or adiabatic shocks in nova ejecta, with the former appearing much more likely. In either case, DK Lacertae represents a rare addition to the exclusive club of X-ray emitting old novae.

  11. LHEA contributions to the Future of Ultraviolet Astronomy Based on Six Years of IUE Research

    NASA Technical Reports Server (NTRS)

    Mushotzky, R. F.; Urry, C. M.

    1984-01-01

    Astronomical models of galactic nuclei emission spectra are reassessed in light of ultraviolet and X-ray spectroscopic observations. Spectral analysis of BL Lacertae objects using data collected by the International Ultraviolet Explorer (IUE) and other astronomical observatories is presented.

  12. SPECTROSCOPY OF THE THREE DISTANT ANDROMEDAN SATELLITES CASSIOPEIA III, LACERTA I, AND PERSEUS I

    SciTech Connect

    Martin, Nicolas F.; Ibata, Rodrigo A.; Chambers, Kenneth C.; Flewelling, Heather; Kaiser, Nicholas; Magnier, Eugene A.; Tonry, John L.; Wainscoat, Richard J.; Collins, Michelle L. M.; Rich, R. Michael; Bell, Eric F.; Bernard, Edouard J.; Ferguson, Annette M. N.

    2014-09-20

    We present Keck II/DEIMOS spectroscopy of the three distant dwarf galaxies of M31 Lacerta I, Cassiopeia III, and Perseus I, recently discovered within the Pan-STARRS1 3π imaging survey. The systemic velocities of the three systems (v {sub r,} {sub helio} = –198.4 ± 1.1 km s{sup –1}, –371.6 ± 0.7 km s{sup –1}, and –326 ± 3 km s{sup –1}, respectively) confirm that they are satellites of M31. In the case of Lacerta I and Cassiopeia III, the high quality of the data obtained for 126 and 212 member stars, respectively, yields reliable constraints on their global velocity dispersions (σ{sub vr} = 10.3 ± 0.9 km s{sup –1} and 8.4 ± 0.6 km s{sup –1}, respectively), leading to dynamical-mass estimates for both of ∼4 × 10{sup 7} M {sub ☉} within their half-light radius. These translate to V-band mass-to-light ratios of 15{sub −9}{sup +12} and 8{sub −5}{sup +9} in solar units. We also use our spectroscopic data to determine the average metallicity of the three dwarf galaxies ([Fe/H] = –2.0 ± 0.1, –1.7 ± 0.1, and –2.0 ± 0.2, respectively). All these properties are typical of dwarf galaxy satellites of Andromeda with their luminosity and size.

  13. IDV Observations of BL 0716+714 at 5 GHz

    NASA Astrophysics Data System (ADS)

    Song, H.-G.; Liu, X.; Liu, J.; Marchili, N.; Krichbaum, T. P.

    2011-06-01

    A selected sample of intra-day variable AGN had been observed for 3-4 days per month at the Urumqi Observatory. The sample includes 7 target sources and 7 calibrators. The BL Lac object B0716+ 714 shows prominent intraday and long term variations.

  14. Dynamical analyses of the companions orbiting eclipsing binaries - I. SW Lacertae

    NASA Astrophysics Data System (ADS)

    Yuan, Jinzhao; Şenavci, Hakan Volkan

    2014-03-01

    New mid-eclipse times of the short-period eclipsing binary SW Lacertae are reported, and two cyclical variations are found in the corresponding O - C diagram. The proposed light-travel time model is refined. The best fit suggests that two possible circumbinary companions are in a near 3:1 mean-motion resonance with periods of 27.01 and 82.61 yr. Based on the best-fitting solution, we have studied the stabilities of the two companions moving on a series of mutually inclined orbits. The results show that no orbital configurations can survive for >1000 yr. Then, non-Keplerian corrections to the initial conditions and the more distant K-dwarf companion discovered by Ruciński, Pribulla & van Kerkwijk, moving on assumed circular orbits with wide ranges of orbital inclinations, are considered in our numerical simulations. The outcome similarly reveals that the whole system is yet short-term unstable. Perhaps, one or both cyclical variations in the mid-eclipse times are attributed to irregular mass exchange and/or magnetic cycles in the magnetically active W UMa system. Despite this, the instability of the system may also arise from the large uncertainties in orbital parameters. So, secular observations of this target are needed to determine the eccentricity of the outmost companion and the orbital period of the middle companion with much higher precision. Our results suggest that, if the two inner companions do exist, they should be on mutually inclined orbits of >100°, with the minimum masses of 0.62 and 1.94 M⊙ for the innermost and middle components, respectively. Our work demonstrates that it is important and necessary to perform dynamical analyses before a discovery of two or more circumbinary companions is announced.

  15. Varicus lacerta, a new species of goby (Teleostei, Gobiidae, Gobiosomatini, Nes subgroup) from a mesophotic reef in the southern Caribbean

    PubMed Central

    Tornabene, Luke; Robertson, D. Ross; Baldwin, Carole C.

    2016-01-01

    Abstract We describe a new species of goby, Varicus lacerta sp. n., which was collected from a mesophotic reef at Curacao, southern Caribbean. The new species is the tenth species of Varicus, all of which occur below traditional SCUBA depths in the wider Caribbean area. Its placement in the genus Varicus is supported by a molecular phylogenetic analysis of three nuclear genes and the mitochondrial gene cytochrome b. In addition, the new species has one anal-fin pterygiophore inserted anterior to the first haemal spine, which distinguishes Varicus species from most species in the closely related and morphologically similar genus Psilotris. Varicus lacerta sp. n. is distinguished from all other named species of Varicus by the absence of scales, having highly branched, feather-like pelvic-fin rays, and in its live coloration. We provide the cytochrome c oxidase I DNA barcode of the holotype and compare color patterns of all species of Varicus and Psilotris for which color photographs or illustrations are available. This study is one of several recent studies demonstrating the utility of manned submersibles in exploring the diversity of poorly studied but species-rich deep-reef habitats. PMID:27408581

  16. Varicus lacerta, a new species of goby (Teleostei, Gobiidae, Gobiosomatini, Nes subgroup) from a mesophotic reef in the southern Caribbean.

    PubMed

    Tornabene, Luke; Robertson, D Ross; Baldwin, Carole C

    2016-01-01

    We describe a new species of goby, Varicus lacerta sp. n., which was collected from a mesophotic reef at Curacao, southern Caribbean. The new species is the tenth species of Varicus, all of which occur below traditional SCUBA depths in the wider Caribbean area. Its placement in the genus Varicus is supported by a molecular phylogenetic analysis of three nuclear genes and the mitochondrial gene cytochrome b. In addition, the new species has one anal-fin pterygiophore inserted anterior to the first haemal spine, which distinguishes Varicus species from most species in the closely related and morphologically similar genus Psilotris. Varicus lacerta sp. n. is distinguished from all other named species of Varicus by the absence of scales, having highly branched, feather-like pelvic-fin rays, and in its live coloration. We provide the cytochrome c oxidase I DNA barcode of the holotype and compare color patterns of all species of Varicus and Psilotris for which color photographs or illustrations are available. This study is one of several recent studies demonstrating the utility of manned submersibles in exploring the diversity of poorly studied but species-rich deep-reef habitats. PMID:27408581

  17. BL Herculis stars - Theoretical models for field variables

    NASA Technical Reports Server (NTRS)

    Carson, R.; Stothers, R.

    1982-01-01

    Type II Cepheids with periods between 1 and 3 days, commonly designated as Bl Herculis stars, have been modeled here with the aim of interpreting the wide variety of light curves observed among the field variables. Previously modeled globular cluster members are used as standard calibration objects. The major finding is that only a small range of luminosities is capable of generating a large variety of light curve types at a given period. For a mass of approximately 0.60 solar mass, the models are able to reproduce the observed mean luminosities, dispersion of mean luminosities, periods, light amplitudes, light asymmetries, and phases of secondary features in the light curves of known BL Her stars. It is possible that the metal-rich variables (which are found only in the field) have luminosities lower than those of most metal-poor variables. The present revised mass for BL Her, a metal-rich object, is not significantly different from the mean mass of the metal-poor variables.

  18. On the magnetization of BL Lac jets

    NASA Astrophysics Data System (ADS)

    Tavecchio, F.; Ghisellini, G.

    2016-03-01

    The current paradigm foresees that relativistic jets are launched as magnetically dominated flows, whose magnetic power is progressively converted to kinetic power of the matter of the jet, until equipartition is reached. Therefore, at the end of the acceleration phase, the jet should still carry a substantial fraction (≈half) of its power in the form of a Poynting flux. It has been also argued that, in these conditions, the best candidate particle acceleration mechanism is efficient reconnection of magnetic field lines, for which it is predicted that magnetic field and accelerated relativistic electron energy densities are in equipartition. Through the modelling of the jet non-thermal emission, we explore if equipartition is indeed possible in BL Lac objects, i.e. low-power blazars with weak or absent broad emission lines. We find that one-zone models (for which only one region is involved in the production of the radiation we observe) the particle energy density is largely dominating (by 1-2 orders of magnitude) over the magnetic one. As a consequence, the jet kinetic power largely exceeds the magnetic power. Instead, if the jet is structured (i.e. made by a fast spine surrounded by a slower layer), the amplification of the inverse Compton emission due to the radiative interplay between the two components allows us to reproduce the emission in equipartition conditions.

  19. A Catalogue of XMM-Newton BL Lacs

    NASA Astrophysics Data System (ADS)

    Racero, E.; De la Calle, I.; Rouco Escorial, A.

    2015-05-01

    A catalogue of XMM-Newton BL Lac is presented based on a cross-correlation with the 1374 BL Lac objects listed in the 13th edition of the Veron-Cetty and Veron (2010) catalogue. X-ray counterparts were searched for in the field of view of more than 10000 pointed observations available in the XMM-Newton Archive (XSA) that were public before June 2012. The cross-correlation yielded around 250 XMM-Newton observations, which correspond to 162 different sources. X-ray data from the three EPIC cameras and Optical Monitor data were uniformly analyzed using the latest XMM-Newton Science Analysis System (SAS) version. The catalogue collects X-ray spectral properties, including flux variability, of the sample in the 0.2--10 KeV energy band. All the catalogue products will be made publicly available to the scientific community.

  20. A Catalogue of XMM-Newton BL Lacs

    NASA Astrophysics Data System (ADS)

    Rouco Escorial, A.; de la Calle, I.; Held, J.; Racero, E.

    2014-07-01

    A catalogue of XMM-Newton BL Lac is presented based on a cross-correlation with the 1374 BL Lac objects listed in the 13th edition of the Veron-Cetty and Veron (2010) catalogue. X-ray counterparts were searched for in the field of view of more than 10000 pointed observations available in the XMM-Newton Archive (XSA) that were public before June 2012. The cross-correlation yielded around 250 XMM-Newton observations, which correspond to 162 different sources. X-ray data from the three EPIC cameras and Optical Monitor data were uniformly analyzed using the latest XMMNewton Science Analysis System (SAS) version. The catalogue collects X-ray spectral properties, including flux variability, of the sample in the 0.2 - 10 keV energy band.

  1. Galactic membership of BL Her type variable stars

    NASA Astrophysics Data System (ADS)

    Jurkovic, M. I.; Stojanovic, M.; Ninkovic, S.

    2016-05-01

    As the RR Lyrae stars evolve on the Hertzsprung-Russell diagram they are believed to become short period Type II Cepheids, known as BL Her type (with a pulsation period from 1 to 3-8 days). Assuming that their mass is around 0.5-0.6M_Sol, and that they are low metallicity objects, they were thought to belong to the halo of the Milky Way. We investigated seven Galactic short period Type II Cepheids (BL Her, SW Tau, V553 Cen, DQ And, BD Cas, V383 Cyg, and KT Com) in order to establish their membership within the Galactic structure using the kinematic approach. Gaia should provide us with more data needed to conduct the study of the whole sample.

  2. Multiband Microvariability of BL Lac During Outburst

    NASA Astrophysics Data System (ADS)

    Clements, S. D.; Carini, M. T.; Noble, J. C.

    1998-01-01

    The blazar BL Lac recently underwent a major outburst. A search for microvariability was made with the 0.76 m telescope at the University of Florida's Rosemary Hill Observatory. Nearly 300 CCD observations in V and R were made over ten nights in July. During that time, BL Lac varied by more than 1.5 magnitudes and exhibited substantial microvariability. In fact, it exhibited microvariability each of the eight nights multiple exposures were made, being most active when brightest on July 29. On this night, four mini-flares were seen within 7 hours. During one of these flares, BL Lac brightened by more than 0.5 magnitude in less than 2.5 hours. The variations in V and R were simultaneous within the limits of the observations. However, the V and R magnitudes did not always change at the same rate. On July 3, BL Lac brightened in R faster than in V. Then on July 4, it dimmed in V faster than in R. Yet over the ten nights observed, BL Lac became bluer as it brightened. Another interesting difference between the V and R data was seen on July 4 when a mini-flare was seen in V but not in R. Clearly, while the V and R variations are highly correlated, there are compelling differences. Here we present these observations and discuss them in relation to models intended to explain microvariability. The authors gratefully acknowledge the support of NASA grant NCC5-228.

  3. [INJECTING MATERIAL FOR SKIN REGENERATION LACERTA APPLICATION IN TREATMENT OF TROPHIC ULCERS IN PATIENTS WITH DIABETIC FOOT SYNDROME].

    PubMed

    Pavlovich, K V; Sydorchuk, R I

    2015-07-01

    Examined 22 patients with diabetes mellitus (DM) type II of neuropathic form of diabetic foot syndrome (DFS). In 12 patients (comparison group) local povidone-iodine was used main in 10 (study group), except povidone-iodine, in the phase of exudation used tyrothricin in gel form, the granulation and epithelization phase, after cleaning the wounds, were injected intradermally 1 ml of injecting material for skin regeneration Lacerta. Trophic defects in 9 (90%) patients of the main group during the observation period healed completely, in the comparison group complete healing of the ulcer reached in 2 (16.7%) patients, the rest-wounds, although purified, however, were lethargic granulation, epithelization occurred very slowly. Consequently, the use of the proposed method allows to achieve more rapid healing of trophic ulcers that do not heal continued in patients of neuropathic forms of DFS. PMID:26591219

  4. Long-term behaviour of starspots. III - Active longitudes on the long-period RS CVn star HK Lacertae

    NASA Technical Reports Server (NTRS)

    Olah, K.; Hall, D. S.; Henry, G. W.

    1991-01-01

    Thirteen years of photometry were used to study active longitudes on the surface of HK Lacertae. The decaying and forming phenomena of active areas in the years of 1980-1981, 1983-1984, and 1988-1989 are shown. New activity centers suddenly occur near the same orbital phase (0.6) and have lifetimes of several (greater than 6) years. The average rotational period of HK Lac is 24.2852 d; compared to the orbital period of 24.4284 d, this implies a 32 degree/year drift of the active areas on the stellar surface. Two possible interpretations for the period difference are discussed: pseudosynchronism and rigidity of magnetic patterns. The active longitudes on HK Lac are compared with similar phenomena found on the sun.

  5. On fuzzy ideals of BL-algebras.

    PubMed

    Meng, Biao Long; Xin, Xiao Long

    2014-01-01

    In this paper we investigate further properties of fuzzy ideals of a BL-algebra. The notions of fuzzy prime ideals, fuzzy irreducible ideals, and fuzzy Gödel ideals of a BL-algebra are introduced and their several properties are investigated. We give a procedure to generate a fuzzy ideal by a fuzzy set. We prove that every fuzzy irreducible ideal is a fuzzy prime ideal but a fuzzy prime ideal may not be a fuzzy irreducible ideal and prove that a fuzzy prime ideal ω is a fuzzy irreducible ideal if and only if ω(0) = 1 and |Im(ω)| = 2. We give the Krull-Stone representation theorem of fuzzy ideals in BL-algebras. Furthermore, we prove that the lattice of all fuzzy ideals of a BL-algebra is a complete distributive lattice. Finally, it is proved that every fuzzy Boolean ideal is a fuzzy Gödel ideal, but the converse implication is not true. PMID:24892085

  6. Object Oriented Learning Objects

    ERIC Educational Resources Information Center

    Morris, Ed

    2005-01-01

    We apply the object oriented software engineering (OOSE) design methodology for software objects (SOs) to learning objects (LOs). OOSE extends and refines design principles for authoring dynamic reusable LOs. Our learning object class (LOC) is a template from which individualised LOs can be dynamically created for, or by, students. The properties…

  7. B-L mediated SUSY breaking with radiative B-L symmetry breaking

    SciTech Connect

    Kikuchi, Tatsuru; Kubo, Takayuki

    2008-11-23

    We explore a mechanism of radiative B-L symmetry breaking in analogous to the radiative electroweak symmetry breaking. The breaking scale of B-L symmetry is related to the neutrino masses through the see-saw mechanism. Once we incorporate the U(1){sub B-L} gauge symmetry in SUSY models, the U(1){sub B-L} gaugino, Z-tilde{sub B-L} appears, and it can mediate the SUSY breaking (Z-prime mediated SUSY breaking) at around the scale of 10{sup 6} GeV. Then we find a links between the neutrino mass (more precisly the see-saw or B-L scale of order 10{sup 6} GeV) and the Z-prime mediated SUSY breaking scale. It is also very interesting that the gluino at the weak scale becomes relatively light, and almost compressed mass spectra for the gaugino sector can be realized in this scenario, which is very interesting in scope of the LHC.

  8. Indomethacin treatment prevents diet-induced obesity and insulin resistance, but not glucose intolerance in C57BL/6J mice

    Technology Transfer Automated Retrieval System (TEKTRAN)

    OBJECTIVE: We performed experiments to examine the metabolic consequences of inhibition of cyclooxygenase (COX) activity in obesity-prone C57BL/6J mice fed a high fat/high sucrose (HF/HS) diet. RESEARCH DESIGN AND METHODS: C57BL/6J mice were fed a HF/HS diet for 7 weeks under thermoneutral conditio...

  9. C57BL/6J male offspring exposed "in utero" and during weaning to a maternal low protein diet have reduced muscle weight by 12 months of age

    Technology Transfer Automated Retrieval System (TEKTRAN)

    Objective: C57BL/6J mice are predisposed to obesity and type 2 diabetes (T2DM) and may be a sensitive model for fetal programming of T2DM. The "maternal low protein diet" (MLP) rat model is well established to study fetal growth restriction effects on programming of T2DM. How data from C57BL/6J mice...

  10. Far-infrared photometry of compact extragalactic sources: OJ 187 and BL Lac

    NASA Technical Reports Server (NTRS)

    Harvey, P. M.; Joy, M.; Lester, D. F.; Wilking, B. A.

    1984-01-01

    The 50 and 100 micron emissions of OJ 287 were detected and upper limits for BL Lac were obtained. These first measurements of two BL Lac objects in the far-infrared show them to be similar to the few quasars previously observed in the far-infrared. In particular, there is no evidence for significant dust emission, and the lambda approximately 100 micron flux density fits on a smooth line joining the near-infrared and millimeter continuum fluxes. The implications of the results for models of the sources are discussed briefly.

  11. A search for microvariability in five OVV quasars

    NASA Technical Reports Server (NTRS)

    Miller, H. R.; Noble, J. C.; Carini, M. T.; Urry, C. M.; Sokoloski, J.; Howell, S. B.

    1992-01-01

    We present results of monitoring a sample of five OVV qausars in an effort to determine if these types of AGNs exhibit microvariability similar to that detected for BL Lacertae objects. Three of the five quasars investigated clearly exhibited microvariability. The timescales for the variations for both BL Lacertae objects and OVV quasars are similar which suggests that the radiation is generated in similar spatial volumes. These variations are consistent with the results of models which explain the observed microvariability as the result of excess emission produced by flares or hot spots randomly appearing and disappearing on the accretion disks around supermassive black holes.

  12. Design of Beamline BL9 at Saga Light Source

    SciTech Connect

    Tanaka, Tooru; Ogawa, Hiroshi; Kamada, Masao; Nishio, Mitsuhiro; Guo, Qixin; Masuda, Masataka; Motooka, Teruaki; Kondo, Yuzi; Hayashida, Kazuki; Yoshimura, Daisuke; Setoyama, Hiroyuki; Okajima, Toshihiro

    2007-01-19

    Saga Light Source (SAGA-LS), which has been constructed at Tosu city in Saga prefecture, is a compact synchrotron light source with storage electron energy of 1.4 GeV. A new beamline for the development of advanced materials and processing has been designed, and is now under construction at BL9 of SAGA-LS. This beamline is one of the three bending magnet beamlines (BL9, BL12, and BL15) constructed by Saga Prefectural Government. In this paper, we describe the design and the expected optical performance of the beamline BL9 at SAGA-LS.

  13. Iridophores and not carotenoids account for chromatic variation of carotenoid-based coloration in common lizards (Lacerta vivipara).

    PubMed

    San-Jose, Luis M; Granado-Lorencio, Fernando; Sinervo, Barry; Fitze, Patrick S

    2013-03-01

    Abstract Carotenoids typically need reflective background components to shine. Such components, iridophores, leucophores, and keratin- and collagen-derived structures, are generally assumed to show no or little environmental variability. Here, we investigate the origin of environmentally induced variation in the carotenoid-based ventral coloration of male common lizards (Lacerta vivipara) by investigating the effects of dietary carotenoids and corticosterone on both carotenoid- and background-related reflectance. We observed a general negative chromatic change that was prevented by β-carotene supplementation. However, chromatic changes did not result from changes in carotenoid-related reflectance or skin carotenoid content but from changes in background-related reflectance that may have been mediated by vitamin A1. An in vitro experiment showed that the encountered chromatic changes most likely resulted from changes in iridophore reflectance. Our findings demonstrate that chromatic variation in carotenoid-based ornaments may not exclusively reflect differences in integumentary carotenoid content and, hence, in qualities linked to carotenoid deposition (e.g., foraging ability, immune response, or antioxidant capacity). Moreover, skin carotenoid content and carotenoid-related reflectance were related to male color polymorphism, suggesting that carotenoid-based coloration of male common lizards is a multicomponent signal, with iridophores reflecting environmental conditions and carotenoids reflecting genetically based color morphs. PMID:23448888

  14. European green lizard (Lacerta viridis) personalities: Linking behavioural types to ecologically relevant traits at different ontogenetic stages.

    PubMed

    Bajer, Katalin; Horváth, Gergely; Molnár, Orsolya; Török, János; Garamszegi, László Zsolt; Herczeg, Gábor

    2015-02-01

    Consistent individual differences within (animal personality) and across (behavioural syndrome) behaviours became well recognized during the past decade. Nevertheless, our knowledge about the evolutionary and developmental mechanisms behind the phenomena is still incomplete. Here, we explored if risk-taking and exploration were consistent and linked to different ecologically relevant traits in wild-caught adult male European green lizards (Lacerta viridis) and in their 2-3 weeks old laboratory-reared offspring. Both adults and juveniles displayed animal personality, consistency being higher in juveniles. We found correlation between risk-taking and exploration (suggestive of a behavioural syndrome) only in adults. Juveniles were more explorative than adults. Large or ectoparasite-free adult males were more explorative than small or parasitized males. Juvenile females tended to be more risk-taking than males. Behaviour of fathers and their offspring did not correlate. We conclude that European green lizards show high behavioural consistency and age is an important determinant of its strength and links to traits likely affecting fitness. PMID:25475912

  15. The gBL transport equations

    SciTech Connect

    Mynick, H.E.

    1989-05-01

    The transport equations arising from the ''generalized Balescu- Lenard'' (gBL) collision operator are obtained, and some of their properties examined. The equations contain neoclassical and turbulent transport as two special cases, having the same structure. The resultant theory offers potential explanation for a number of results not well understood, including the anomalous pinch, observed ratios of Q/GAMMAT on TFTR, and numerical reproduction of ASDEX profiles by a model for turbulent transport invoked without derivation, but by analogy to neoclassical theory. The general equations are specialized to consideration of a number of particular transport mechanisms of interest. 10 refs.

  16. High-energy cosmic neutrinos from spine-sheath BL Lac jets

    NASA Astrophysics Data System (ADS)

    Tavecchio, F.; Ghisellini, G.

    2015-08-01

    We recently proposed that structured (spine-sheath) jets associated with BL Lac objects could offer a suitable environment for the production of the extragalactic high-energy (E > 100 TeV) neutrino recently revealed by IceCube. Our previous analysis was limited to low-power BL Lac objects. We extend our preliminary study to the entire BL Lac population, assuming that the entire diffuse emission is accounted for by these sources. The neutrino output from a single source depends on a relatively large number of parameters. However, for several of them we have constraints coming from observations and previous application of the structured jet model to blazar and radiogalaxy emission. The observed neutrino spectrum then fixes the remaining free parameters. We assume that the power of cosmic rays as well as the radiative luminosity of the sheath depends linearly on the jet power. In turn, we assume that the latter is well traced by the γ-ray luminosity. We exploit the BL Lac γ-ray luminosity function and its cosmic evolution as recently inferred from Fermi-LAT data to derive the expected neutrino cumulative intensity from the entire BL Lac population. When considering only the low-power BL Lacs, a large cosmic ray power for each source is required to account for the neutrino flux. Instead, if BL Lacs of all powers produce neutrinos, the power demand decreases, and the required cosmic ray power becomes of the same order of the radiative jet power. In our scheme, the maximum energy of cosmic rays is constrained to be ≲ few PeV by the lack of events above few PeV. Although such a value is obtained through a fine-tuning with the data, we show that it could be possibly related to the equilibrium between cooling and acceleration processes for high-energy cosmic rays. We also discuss the prospects for the direct association of IceCube events with BL Lacs, providing an estimate of the expected counts for the most promising sources.

  17. Galaxies

    SciTech Connect

    Not Available

    1981-01-01

    Normal galaxies, radio galaxies, and Seyfert galaxies are considered. The large magellanic cloud and the great galaxy in Andromedia are highlighted. Quasars and BL lacertae objects are also discussed and a review of the spectral observations of all of these galaxies and celestial objects is presented.

  18. Geographic variation of life-history traits in the sand lizard, Lacerta agilis: testing Darwin's fecundity-advantage hypothesis.

    PubMed

    Roitberg, E S; Eplanova, G V; Kotenko, T I; Amat, F; Carretero, M A; Kuranova, V N; Bulakhova, N A; Zinenko, O I; Yakovlev, V A

    2015-03-01

    The fecundity-advantage hypothesis (FAH) explains larger female size relative to male size as a correlated response to fecundity selection. We explored FAH by investigating geographic variation in female reproductive output and its relation to sexual size dimorphism (SSD) in Lacerta agilis, an oviparous lizard occupying a major part of temperate Eurasia. We analysed how sex-specific body size and SSD are associated with two putative indicators of fecundity selection intensity (clutch size and the slope of the clutch size-female size relationship) and with two climatic variables throughout the species range and across two widespread evolutionary lineages. Variation within the lineages provides no support for FAH. In contrast, the divergence between the lineages is in line with FAH: the lineage with consistently female-biased SSD (L. a. agilis) exhibits higher clutch size and steeper fecundity slope than the lineage with an inconsistent and variable SSD (L. a. exigua). L. a. agilis shows lower offspring size (egg mass, hatchling mass) and higher clutch mass relative to female mass than L. a. exigua, that is both possible ways to enhance offspring number are exerted. As the SSD difference is due to male size (smaller males in L. a. agilis), fecundity selection favouring larger females, together with viability selection for smaller size in both sexes, would explain the female-biased SSD and reproductive characteristics of L. a. agilis. The pattern of intraspecific life-history divergence in L. agilis is strikingly similar to that between oviparous and viviparous populations of a related species Zootoca vivipara. Evolutionary implications of this parallelism are discussed. PMID:25627276

  19. Phylogeography and demographic history of Lacerta lepida in the Iberian Peninsula: multiple refugia, range expansions and secondary contact zones

    PubMed Central

    2011-01-01

    Background The Iberian Peninsula is recognized as an important refugial area for species survival and diversification during the climatic cycles of the Quaternary. Recent phylogeographic studies have revealed Iberia as a complex of multiple refugia. However, most of these studies have focused either on species with narrow distributions within the region or species groups that, although widely distributed, generally have a genetic structure that relates to pre-Quaternary cladogenetic events. In this study we undertake a detailed phylogeographic analysis of the lizard species, Lacerta lepida, whose distribution encompasses the entire Iberian Peninsula. We attempt to identify refugial areas, recolonization routes, zones of secondary contact and date demographic events within this species. Results Results support the existence of 6 evolutionary lineages (phylogroups) with a strong association between genetic variation and geography, suggesting a history of allopatric divergence in different refugia. Diversification within phylogroups is concordant with the onset of the Pleistocene climatic oscillations. The southern regions of several phylogroups show a high incidence of ancestral alleles in contrast with high incidence of recently derived alleles in northern regions. All phylogroups show signs of recent demographic and spatial expansions. We have further identified several zones of secondary contact, with divergent mitochondrial haplotypes occurring in narrow zones of sympatry. Conclusions The concordant patterns of spatial and demographic expansions detected within phylogroups, together with the high incidence of ancestral haplotypes in southern regions of several phylogroups, suggests a pattern of contraction of populations into southern refugia during adverse climatic conditions from which subsequent northern expansions occurred. This study supports the emergent pattern of multiple refugia within Iberia but adds to it by identifying a pattern of refugia coincident

  20. Intranight Variability During the 1997 Outburst of BL Lac

    NASA Astrophysics Data System (ADS)

    Clements, Sandra D.; Carini, Michael T.; Noble, John C.

    1998-02-01

    The blazar BL Lac underwent a major outburst this summer. To search for intranight variability during the outburst, observations of BL Lac were made with the 30 inch telescope at the University of Florida's Rosemary Hill Observatory. During ten nights in July, nearly 300 CCD observations were made. BL Lac was seen to vary by more than 1.5 magnitudes over those ten nights. Substantial intranight variability was also observed. For example, on July 29, BL Lac increased in brightness by more than 0.5 magnitude in less than 2.5 hours. The observations of BL Lac taken in July are reported here and discussed in relation to the models intended to explain intranight variability.

  1. Structure of Yin Yang 1 Oligomers That Cooperate with RuvBL1-RuvBL2 ATPases*

    PubMed Central

    López-Perrote, Andrés; Alatwi, Hanan E.; Torreira, Eva; Ismail, Amani; Ayora, Silvia; Downs, Jessica A.; Llorca, Oscar

    2014-01-01

    Yin Yang 1 (YY1) is a transcription factor regulating proliferation and differentiation and is involved in cancer development. Oligomers of recombinant YY1 have been observed before, but their structure and DNA binding properties are not well understood. Here we find that YY1 assembles several homo-oligomeric species built from the association of a bell-shaped dimer, a process we characterized by electron microscopy. Moreover, we find that YY1 self-association also occurs in vivo using bimolecular fluorescence complementation. Unexpectedly, these oligomers recognize several DNA substrates without the consensus sequence for YY1 in vitro, and DNA binding is enhanced in the presence of RuvBL1-RuvBL2, two essential AAA+ ATPases. YY1 oligomers bind RuvBL1-RuvBL2 hetero-oligomeric complexes, but YY1 interacts preferentially with RuvBL1. Collectively, these findings suggest that YY1-RuvBL1-RuvBL2 complexes could contribute to functions beyond transcription, and we show that YY1 and the ATPase activity of RuvBL2 are required for RAD51 foci formation during homologous recombination. PMID:24990942

  2. Reduction of fear-potentiated startle by benzodiazepines in C57BL/6J mice

    PubMed Central

    Smith, Kiersten S.; Meloni, Edward G.; Myers, Karyn M.; Veer, Ashlee Van't; Carlezon, William A.; Rudolph, Uwe

    2011-01-01

    Rationale Anxiety disorders affect 18% of the United States adult population annually. Recent surges in the diagnosis of posttraumatic stress disorder (PTSD) from combat-exposed veterans have prompted an urgent need to understand the pathophysiology underlying this debilitating condition. Objectives Anxiety and fear responses are partly modulated by gamma aminobutyric acid type A (GABAA) receptor-mediated synaptic inhibition; benzodiazepines potentiate GABAergic inhibition and are effective anxiolytics. Many genetically modified mouse lines are generated and/or maintained on the C57BL/6J background, a strain where manipulation of anxiety-like behavior using benzodiazepines is difficult. Fear-potentiated startle (FPS), a test of conditioned fear, is a useful preclinical tool to study PTSD-like responses but has been difficult to establish in C57BL/6J mice. Methods We modified several FPS experimental parameters and developed a paradigm to assess conditioned fear in C57BL/6J mice. The 6-day protocol consisted of three startle Acclimation days, a Pre-Test day followed by Training and Testing for FPS. Subject responses to the effects of three benzodiazepines were also examined. Results C57BL/6J mice had low levels of unconditioned fear assessed during Pre-Test (15–18%) but showed robust FPS (80–120%) during the Test session. Conditioned fear responses extinguished over repeated test sessions. Administration of the benzodiazepines alprazolam (0.5 and 1 mg/kg, i.p.), chlordiazepoxide (5 and 10 mg/kg, i.p.), and diazepam (1, 2, and 4 mg/kg, i.p.) significantly reduced FPS to Pre-Test levels. Conclusions We used a modified and pharmacologically-validated paradigm to assess FPS in mice thereby providing a powerful tool to examine the neurobiology of PTSD in genetic models of anxiety generated on the C57BL/6J background. PMID:20922362

  3. Dark matter in B-L extended MSSM models

    SciTech Connect

    Khalil, S.; Okada, H.

    2009-04-15

    We analyze the dark matter problem in the context of the supersymmetric U(1){sub B-L} model. In this model, the lightest neutralino can be the B-L gaugino Z-tilde{sub B-L} or the extra Higgsinos {chi}-tilde{sub 1,2} dominated. We compute the thermal relic abundance of these particles and show that, unlike the lightest neutralino in the MSSM, they can account for the observed relic abundance with no conflict with other phenomenological constraints. The prospects for their direct detection, if they are part of our galactic halo, are also discussed.

  4. Intense X-ray flares from active stellar systems - EV Lacertae and HD 8357

    NASA Technical Reports Server (NTRS)

    Ambruster, C.; Snyder, W. A.; Wood, K. S.

    1984-01-01

    The HEAO A-1 Sky Survey Experiment included X-ray data used to define light curves for the flare star EV Lac and for X-ray flares observed in the binary system HD 8357. The data were taken during flare events and were detailed enough to calculate the flare rates and flaring luminosities. The peak luminosities during flares were several times the luminosities in normal X-ray flares emitted by the objects. Peak luminosities reached 30-50 times the normal variations and were associated with an order of magnitude increase in energy output. EV Lac was sufficiently active to be recommended for inclusion in future X-ray monitoring programs.

  5. Characterization of (357439) 2004 BL86 on its close approach to Earth in 2015

    NASA Astrophysics Data System (ADS)

    Birlan, M.; Popescu, M.; Nedelcu, D. A.; Turcu, V.; Pop, A.; Dumitru, B.; Stevance, F.; Vaduvescu, O.; Moldovan, D.; Rocher, P.; Sonka, A.; Mircea, L.

    2015-09-01

    Context. The potentially hazardous asteroid (PHA) (357439) 2004 BL86 grazed Earth on January 26, 2015 at a distance of about 1.2 million km. This favorable geometry allowed observing it to derive its physical and dynamical parameters. (357439) 2004 BL86 was previously estimated to be a 500-m body. We study it also considering possible mechanisms that might mitigate the effect of asteroids that might become dangerous for Earth. Aims: Physical and dynamical investigations of this peculiar object were performed to be able to characterize this object. Methods: We used spectral observations obtained in the visible (V) using the Isaac Newton Telescope and in the near-infrared (NIR) using the InfraRed Telescope Facility. A complementary photometric survey during two nights was also provided by the Astronomical Observatory Cluj-Feleacu station in Romania. We anlyzed the data using reliable mathematical tools that were previously published under the acronym M4AST. Results: VNIR spectral observations classify (357439) 2004 BL86 as V-type asteroid. The mineralogical analysis reveals its similarities to howardite-eucrite-diogenite meteorites. The band analysis reveals that the object is more similar to a eucritic and howarditic composition, and that it originated from the crust of a large parent body. The analysis yields a mineralogical solution of Wo17Fs39 with an error bar of 4%. Based on the average value of the thermal albedo for V-type objects, its diameter was re-estimated to a value of 290 ± 30 m. The dynamical analysis shows a chaotical behavior of (357439) 2004 BL86. The statistics on meteorite falls show that (357439) 2004 BL86 does not appear to significantly contribute to the current howardite-eucrite-diogenite meteorite flux. For the two photometrical observing runs the following values of the rotational period and peak-to-peak amplitude were estimated for the light curves: 2.637 ± 0.024 h, 0.105 ± 0.007 mag, and 2.616 ± 0.061 h, 0.109 ± 0.018 mag

  6. Radar Imaging of Binary Near-Earth Asteroid (357439) 2004 BL86

    NASA Astrophysics Data System (ADS)

    Benner, Lance AM; Brozovic, Marina; Giorgini, Jon D.; Jao, Joseph S.; Lee, Clement G.; Taylor, Patrick A.; Howell, Ellen S.; Busch, Michael W.; Ford, H. Alyson; Ghigo, Frank; Nolan, Michael C.; Slade, Martin A.; Lawrence, Kenneth J.; Richardson, James E.; Rivera-Valentin, Edgard G.; Rozek, Agata

    2015-08-01

    We report radar observations of near-Earth asteroid 2004 BL86 obtained during 2015 Jan. 26-31 at the 70 m and 34 m Goldstone facilities, Arecibo, Green Bank, and elements of the Very Long Baseline Array. 2004 BL86 approached within 0.0080 au (3.1 lunar distances) on Jan. 26, the closest known approach by any object with an absolute magnitude brighter than ~19 until 2027. Prior to the encounter, virtually nothing was known about its physical properties other than its absolute magnitude of 19, which suggested a diameter within a factor of two of 500 m. Due to its size and the extremely close approach, 2004 BL86 was a very strong radar target that provided an outstanding opportunity for radar imaging and physical characterization. The radar images confirmed photometric results reported by Pravec et al. (2015, CBET 4063) that 2004 BL86 is a binary system. This is the 43rd near-Earth asteroid binary detected by radar. Delay-Doppler images placed thousands of 3.75 m-resolution pixels on the object and reveal a rounded and oblate primary with an equatorial diameter of ~300 m, suggesting it is optically-bright, evidence for ridges, small-scale topography including boulders, and a large angular feature near one of the poles. A preliminary estimate for the diameter of the secondary is ~70 m. The images hint that the secondary’s rotation is synchronous with its orbital period. The observations also yielded the first detection of an asteroid with a new 80 kW C-band radar (7190 MHz, 4.2 cm) at the 34 m DSS-13 antenna at the Goldstone Deep Space Communications Complex. This new radar can achieve a range resolution up to 1.875 m/pixel that is twice as fine as the highest resolution previously achievable.

  7. HYDROGEOLOGIC CHARACTERIZATION OF THE U-3bl COLLAPSE ZONE

    SciTech Connect

    Bechtel Nevada and National Security Technologies, LLC

    2006-09-01

    The U-3bl collapse crater was formed by an underground nuclear test in August 1962. This crater and the adjoining U-3ax crater were subsequently developed and used as a bulk low-level radioactive waste disposal cell (U-3ax/bl), which is part of the Area 3 Radioactive Waste Management Site at the Nevada Test Site (NTS). Various investigations have been conducted to assess the hydrogeologic characteristics and properties in the vicinity of the U-3ax/bl waste disposal cell. This report presents data from one of these investigations, conducted in 1996. Also included in this report is a review of pertinent nuclear testing records, which shows that the testing operations and hydrogeologic setting of the U-3ax/bl site were typical for the period and location of testing.

  8. A comparative phenotypic and genomic analysis of C57BL/6J and C57BL/6N mouse strains

    PubMed Central

    2013-01-01

    Background The mouse inbred line C57BL/6J is widely used in mouse genetics and its genome has been incorporated into many genetic reference populations. More recently large initiatives such as the International Knockout Mouse Consortium (IKMC) are using the C57BL/6N mouse strain to generate null alleles for all mouse genes. Hence both strains are now widely used in mouse genetics studies. Here we perform a comprehensive genomic and phenotypic analysis of the two strains to identify differences that may influence their underlying genetic mechanisms. Results We undertake genome sequence comparisons of C57BL/6J and C57BL/6N to identify SNPs, indels and structural variants, with a focus on identifying all coding variants. We annotate 34 SNPs and 2 indels that distinguish C57BL/6J and C57BL/6N coding sequences, as well as 15 structural variants that overlap a gene. In parallel we assess the comparative phenotypes of the two inbred lines utilizing the EMPReSSslim phenotyping pipeline, a broad based assessment encompassing diverse biological systems. We perform additional secondary phenotyping assessments to explore other phenotype domains and to elaborate phenotype differences identified in the primary assessment. We uncover significant phenotypic differences between the two lines, replicated across multiple centers, in a number of physiological, biochemical and behavioral systems. Conclusions Comparison of C57BL/6J and C57BL/6N demonstrates a range of phenotypic differences that have the potential to impact upon penetrance and expressivity of mutational effects in these strains. Moreover, the sequence variants we identify provide a set of candidate genes for the phenotypic differences observed between the two strains. PMID:23902802

  9. Color Variations of Two Blazars: BL Lac and PKS 0736+017

    NASA Astrophysics Data System (ADS)

    Clements, S. D.

    2002-12-01

    Multi-night campaigns to monitor sources for microvariability were undertaken in the summer of 1997 for BL Lac and in early 2002 for PKS 0736+017. BL Lac was observed at Rosemary Hill Observatory in Bronson, Florida and PKS 0736+017 was observed with the SARA telescope on Kitt Peak in Arizona. Both sources underwent dramatic flares and exhibited substantial microvariability. During each campaign, the source was observed alternately through V and R filters so that color variations could be monitored as well. The most commonly reported behavior for such objects is that they become redder when fainter. This is observed in the BL Lac data. These data do not indicate that the point source varies in color however. Instead, they support the notion that the underlying host galaxy contributes a larger fraction of the total flux when the source is faint than when it is bright. More unusual was the observation that PKS 0736+017 was observed to be redder when brighter. The data support the notion that the observed color variation may be related more to the nature of the variation (flaring, subsiding, or quiescent) than to the flux level.

  10. Separating the BL Lac and cluster X-ray emissions in Abell 689 with Chandra

    NASA Astrophysics Data System (ADS)

    Giles, P. A.; Maughan, B. J.; Birkinshaw, M.; Worrall, D. M.; Lancaster, K.

    2012-01-01

    We present the results of a Chandra observation of the galaxy cluster Abell 689 (z = 0.279). Abell 689 is one of the most luminous clusters detected in the ROSAT All Sky Survey (RASS), but was flagged as possibly including significant point source contamination. The small point spread function of the Chandra telescope allows us to confirm this and separate the point source from the extended cluster X-ray emission. For the cluster, we determine a bolometric luminosity of Lbol= (3.3 ± 0.3) × 1044 erg s-1 and a temperature of kT = 5.1+2.2- 1.3 keV when including a physically motivated background model. We compare our measured luminosity for A689 to that quoted in the RASS, and find L0.1-2.4 keV= 2.8 × 1044 erg s-1, a value ˜10 times lower than the ROSAT measurement. Our analysis of the point source shows evidence for significant pile-up, with a pile-up fraction of ≃60 per cent. Sloan Digital Sky Survey spectra and Hubble Space Telescope (HST) images lead us to the conclusion that the point source within Abell 689 is a BL Lac object. Using radio and optical observations from the Very Large Array and HST archives, we determine αro= 0.50, αox= 0.77 and αrx= 0.58 for the BL Lac, which would classify it as being of 'high-energy peak BL Lac' type. Spectra extracted of A689 show a hard X-ray excess at energies above 6 keV that we interpret as inverse-Compton emission from aged electrons that may have been transported into the cluster from the BL Lac.

  11. Adaptive Objectness for Object Tracking

    NASA Astrophysics Data System (ADS)

    Liang, Pengpeng; Pang, Yu; Liao, Chunyuan; Mei, Xue; Ling, Haibin

    2016-07-01

    Object tracking is a long standing problem in vision. While great efforts have been spent to improve tracking performance, a simple yet reliable prior knowledge is left unexploited: the target object in tracking must be an object other than non-object. The recently proposed and popularized objectness measure provides a natural way to model such prior in visual tracking. Thus motivated, in this paper we propose to adapt objectness for visual object tracking. Instead of directly applying an existing objectness measure that is generic and handles various objects and environments, we adapt it to be compatible to the specific tracking sequence and object. More specifically, we use the newly proposed BING objectness as the base, and then train an object-adaptive objectness for each tracking task. The training is implemented by using an adaptive support vector machine that integrates information from the specific tracking target into the BING measure. We emphasize that the benefit of the proposed adaptive objectness, named ADOBING, is generic. To show this, we combine ADOBING with seven top performed trackers in recent evaluations. We run the ADOBING-enhanced trackers with their base trackers on two popular benchmarks, the CVPR2013 benchmark (50 sequences) and the Princeton Tracking Benchmark (100 sequences). On both benchmarks, our methods not only consistently improve the base trackers, but also achieve the best known performances. Noting that the way we integrate objectness in visual tracking is generic and straightforward, we expect even more improvement by using tracker-specific objectness.

  12. Love Objects.

    ERIC Educational Resources Information Center

    Cusack, Lynne

    1998-01-01

    Discusses the role of "security" or "transition" objects, such as a blanket or stuffed toy, in children's development of self-comfort and autonomy. Notes the influence of parents in the child-object relationship, and discusses children's responses to losing a security object, and the developmental point at which a child will give up such an…

  13. Fractal Property in the Light Curve of BL Lac Object S5 0716 + 714

    NASA Astrophysics Data System (ADS)

    Ou, J. W.; Zheng, Y. G.

    2014-09-01

    In this paper, we compile the historical R-band data of S5 0716 + 714 from literature and obtain its fractal dimension by using a fractal method and then simulate the data with the Weierstrass-Mandelbrot (W-M) function. It is considered that the light curve has a fractal property.

  14. INTEGRAL source IGR J16562-3301 --- a new BL Lac object

    NASA Astrophysics Data System (ADS)

    Burenin, R.; Revnivtsev, M.; Mescheryakov, A.; Bikmaev, I.; Pavlinsky, M.; Sunyaev, R.

    2007-11-01

    The accurate position of the hard X-ray source IGR J16562-3301/SWIFT J1656.3-3302 (Okajima et al. 2006, ATel #799, Krivonos et al. 2007, astro-ph/0701836) was determined earlier by Tueller et al. (2006, ATEL #835) using SWIFT/XRT observation of this field. We found that more accurate position of this source can be derived from the same data when the systematics of SWIFT/XRT astrometry is corrected using the other two bright X-ray sources identified with relatively bright optical stars.

  15. Estimation of the extragalactic background light using TeV observations of BL Lac objects

    SciTech Connect

    Sinha, Atreyee; Acharya, B. S.; Sahayanathan, S.; Godambe, S.; Misra, R. E-mail: acharya@tifr.res.in E-mail: gsagar@barc.ernet.in

    2014-11-01

    The very high-energy (VHE) gamma-ray spectral index of high-energy peaked blazars correlates strongly with its corresponding redshift, whereas no such correlation is observed in the X-ray or GeV bands. We attribute this correlation to photon-photon absorption of TeV photons with the extragalactic background light (EBL), and utilizing this we compute the allowed flux range for the EBL, which is independent of previous estimates. The observed VHE spectrum of the sources in our sample can be well approximated by a power law, and if the de-absorbed spectrum is also assumed to be a power law, then we show that the spectral shape of EBL will be εn(ε) ∼ klog (ε/ε {sub p}). We estimate the range of values for the parameters defining the EBL spectrum, k and ε {sub p}, such that the correlation of the intrinsic VHE spectrum with redshift is nullified. The estimated EBL depends only on the observed correlation and the assumption of a power-law source spectrum. Specifically, it does not depend on the spectral modeling or radiative mechanism of the sources or on any theoretical shape of the EBL spectrum obtained through cosmological calculations. The estimated EBL spectrum is consistent with the upper and lower limits imposed by different observations. Moreover, it also agrees closely with the theoretical estimates obtained through cosmological evolution models.

  16. The long-term variability of BL Lac object PKS 0735+178

    NASA Astrophysics Data System (ADS)

    Fan, J. H.; Xie, G. Z.; Lin, R. G.; Qin, Y. P.; Li, K. H.; Zhang, X.

    1997-11-01

    The long-term variability of PKS 0735+178 in B band is shown with some new data presented and discussed by means of Jurkevich's method. The results show with good possibility the presence of a period of 14.2 years. The period of 4.89 years found by \\cite[Webb et al. (1988)]{web88} and \\cite[Smith et al. (1987)]{smi87} might be confirmed with more observations, and their period of 1.2 years can be ruled out.

  17. Optical Photometry of the BL Lac Object 1ES 1959+650

    NASA Astrophysics Data System (ADS)

    Yuan, Y. H.; Fan, J. H.; Pan, H. J.

    2015-09-01

    Using the 1.56 m telescope at Shanghai Observatory, China, we present the photometric results of 1ES 1959+650, which cover from 2006 June 11 to 2014 July 31. The maximum variabilities are {{Δ }}{m}V| {max}=1.74+/- 0.02 mag in the V band, {{Δ }}{m}R| {max}=0.97+/- 0.02 mag in the R band, and {{Δ }}{m}I| {max}=1.15+/- 0.03 mag in the I band. During the monitoring period, we obtain intraday variabilities on 2009 September 2 (JD 2455077) and 2009 September 3 (JD 2455078). On 2009 September 2, the intraday variabilities are {{Δ }}{m}V=0.36+/- 0.08 mag within 1.56 hr, {{Δ }}{m}R=0.21+/- 0.04 mag within 23 minutes, and {{Δ }}{m}I=0.53+/- 0.03 mag within 45 minutes. On 2009 September 3, the intraday variabilities are {{Δ }}{m}V=0.40+/- 0.10 mag within 27 minutes, {{Δ }}{m}R=0.48+/- 0.04 mag within 3.24 hr, and {{Δ }}{m}I=0.68+/- 0.06 mag within 3.72 hr. The two intraday variabilities occur in 24 hr, which may occur in the same variable phase. Other results show that (1) no quasi-periodicity is found in the long-term light curve and (2) the correlations between the brightness and the spectrum show obvious anti-correlation, α =-(0.18+/- 0.02){F}V+(2.33+/- 0.12), with the correlation coefficient r = -0.74 and the chance probability p < 0.01%.

  18. New ways to leptogenesis with gauged B-L symmetry

    DOE PAGESBeta

    Babu, K.S.; Meng, Yanzhi; Tavartkiladze, Zurab

    2009-10-01

    We show that in supersymmetric models with gauged B-L symmetry, there is a new source for cosmological lepton asymmetry. The Higgs bosons responsible for B-L gauge symmetry breaking decay dominantly into right-handed sneutrinos N~ and N~* producing an asymmetry in N~ over N~*. This can be fully converted into ordinary lepton asymmetry in the decays of N~. In simple models with gauged B-L symmetry we show that resonant/soft leptogenesis is naturally realized. Supersymmetry guarantees quasi-degenerate scalar states, while soft breaking of SUSY provides the needed CP violation. Acceptable values of baryon asymmetry are obtained without causing serious problems with gravitinomore » abundance.« less

  19. Sex differences in memory for landmark arrays in C57BL/J6 mice.

    PubMed

    Bettis, Tania J; Jacobs, Lucia F

    2013-11-01

    The most robust sex differences in cognition across polygynous mammalian species are the sex-specific patterns of the use of spatial cues during encoding and orientation. In laboratory rats, wild rodents, and humans, females orient preferentially to the features and arrangement of local landmarks, while males preferentially attend to distant landmarks. Yet this sex-specific pattern is often absent or reversed in the laboratory mouse, a species representing a major laboratory model of neural mechanisms. We explored sex differences in the C57BL/J6 strain of laboratory mouse by employing tasks that were motivated by the natural patterns of exploration. We predicted that such tasks would unmask the predicted default polygynous patterns of cue use by females and males. We used two standard tasks, a novel object recognition task and a five-stage serial object dishabituation task. On the first task, the results showed a female advantage in detecting the novel object, as predicted by prior results from other polygynous species. In the second task, we found, also as predicted, a male advantage in performance when the polarization of the array was distorted and a female advantage in performance when the local array was re-arranged. The pattern of sex-specific advantages in performance in C57BL/J6 mouse is thus concordant with that found in other polygynous mammals. PMID:23526160

  20. Objective lens

    NASA Technical Reports Server (NTRS)

    Olczak, Eugene G. (Inventor)

    2011-01-01

    An objective lens and a method for using same. The objective lens has a first end, a second end, and a plurality of optical elements. The optical elements are positioned between the first end and the second end and are at least substantially symmetric about a plane centered between the first end and the second end.

  1. Proteomic Analysis on Acetate Metabolism in Citrobacter sp. BL-4

    PubMed Central

    Kim, Young-Man; Lee, Sung-Eun; Park, Byeoung-Soo; Son, Mi-Kyung; Jung, Young-Mi; Yang, Seung-Ok; Choi, Hyung-Kyoon; Hur, Sung-Ho; Yum, Jong Hwa

    2012-01-01

    Mass production of glucosamine (GlcN) using microbial cells is a worthy approach to increase added values and keep safety problems in GlcN production process. Prior to set up a microbial cellular platform, this study was to assess acetate metabolism in Citrobacter sp. BL-4 (BL-4) which has produced a polyglucosamine PGB-2. The LC-MS analysis was conducted after protein separation on the 1D-PAGE to accomplish the purpose of this study. 280 proteins were totally identified and 188 proteins were separated as acetate-related proteins in BL-4. Acetate was converted to acetyl-CoA by acetyl-CoA synthetase up-regulated in the acetate medium. The glyoxylate bypass in the acetate medium was up-regulated with over-expression of isocitrate lyases and 2D-PAGE confirmed this differential expression. Using 1H-NMR analysis, the product of isocitrate lyases, succinate, increased about 15 times in the acetate medium. During acetate metabolism proteins involved in the lipid metabolism and hexosamine biosynthesis were over-expressed in the acetate medium, while proteins involved in TCA cycle, pentose phosphate cycle and purine metabolism were down-regulated. Taken together, the results from the proteomic analysis can be applied to improve GlcN production and to develop metabolic engineering in BL-4. PMID:22211106

  2. The gravitational wave spectrum from cosmological B-L breaking

    SciTech Connect

    Buchmüller, W.; Domcke, V.; Kamada, K.; Schmitz, K. E-mail: valerie.domcke@desy.de E-mail: kai.schmitz@ipmu.jp

    2013-10-01

    Cosmological B-L breaking is a natural and testable mechanism to generate the initial conditions of the hot early universe. If B-L is broken at the grand unification scale, the false vacuum phase drives hybrid inflation, ending in tachyonic preheating. The decays of heavy B-L Higgs bosons and heavy neutrinos generate entropy, baryon asymmetry and dark matter and also control the reheating temperature. The different phases in the transition from inflation to the radiation dominated phase produce a characteristic spectrum of gravitational waves. We calculate the complete gravitational wave spectrum due to inflation, preheating and cosmic strings, which turns out to have several features. The production of gravitational waves from cosmic strings has large uncertainties, with lower and upper bounds provided by Abelian Higgs strings and Nambu-Goto strings, implying Ω{sub GW}h{sup 2} ∼ 10{sup −13}–10{sup −8}, much larger than the spectral amplitude predicted by inflation. Forthcoming gravitational wave detectors such as eLISA, advanced LIGO, ET, BBO and DECIGO will reach the sensitivity needed to test the predictions from cosmological B-L breaking.

  3. Scalar dark matter in the B-L model

    NASA Astrophysics Data System (ADS)

    Rodejohann, Werner; Yaguna, Carlos E.

    2015-12-01

    The U(1)B-L extension of the Standard Model requires the existence of right-handed neutrinos and naturally realizes the seesaw mechanism of neutrino mass generation. We study the possibility of explaining the dark matter in this model with an additional scalar field, phiDM, that is a singlet of the Standard Model but charged under U(1)B-L. An advantage of this scenario is that the stability of phiDM can be guaranteed by appropriately choosing its B-L charge, without the need of an extra ad hoc discrete symmetry. We investigate in detail the dark matter phenomenology of this model. We show that the observed dark matter density can be obtained via gauge or scalar interactions, and that semi-annihilations could play an important role in the latter case. The regions consistent with the dark matter density are determined in each instance and the prospects for detection in future experiments are analyzed. If dark matter annihilations are controlled by the B-L gauge interaction, the mass of the dark matter particle should lie below 5 TeV and its direct detection cross section can be easily probed by XENON1T; if instead they are controlled by scalar interactions, the dark matter mass can be much larger and the detection prospects are less certain. Finally, we show that this scenario can be readily extended to accommodate multiple dark matter particles.

  4. Multimodal sexual signals in male ocellated lizards Lacerta lepida: vitamin E in scent and green coloration may signal male quality in different sensory channels

    NASA Astrophysics Data System (ADS)

    Martín, José; López, Pilar

    2010-06-01

    The mechanisms that confer honesty to multiple sexual signals of vertebrates remain less known. We suggest that vitamin E in the scent (femoral secretions) and carotenoids in coloration of Lacerta lepida lizards might advertise quality because they are relevant in metabolism as major antioxidants and have a dietary origin. Results showed that there may be similar trade-offs between immunity and both chemical and visual signaling, as males with more vitamin E in secretions and those with more greenish, darker, and saturated carotenoid-dependent colorations had a higher immune response. This suggests that only high-quality males can divert from metabolism and allocate enough vitamin E to secretions and enough carotenoids to coloration. Therefore, information provided by visual and chemical signals is congruent. The use of multiple sensory channels may allow signaling a male quality under different circumstances or reinforce the reliability of the signal when both signals are perceived simultaneously. However, we also found that characteristics of carotenoid-dependent coloration mirror the amounts of vitamin E in secretions. This might support that carotenoids, which are not true antioxidants in the organism, would just reflect and “inform” on the actual contents of metabolic antioxidant vitamin E, which is part of the true system that prevent oxidation. We suggest that the metabolic roles of vitamins might be the actual basis of honesty of many sexual displays, and that carotenoid-based signals might be just the visible part of the whole system.

  5. Interrenal activity in the female lizard Lacerta vivipara J.: in vitro response to ACTH 1-39 and to [Sar1, Val5] angiotensin II (ANG II).

    PubMed

    Dauphin-Villemant, C; Leboulenger, F; Xavier, F; Vaudry, H

    1988-01-01

    A perifusion system technique was developed in order to determine in vitro the respective roles of ACTH and ANG II in the regulation of adrenal steroidogenesis in the lizard Lacerta vivipara. Synthetic human ACTH 1-39, administered as 20-min pulses, stimulated corticosterone (B) and aldosterone (A) release in a dose-dependent manner. The increase in corticosterone output was higher than that in aldosterone output, leading to an enhancement of the B/A ratio. Iterative stimulations with 1 nM ACTH (20-min pulses every 120 min) led to reproducible increases in corticosterone and aldosterone release. Prolonged stimulation with 1 nM ACTH (up to 240 min) caused a sustained increase in corticosteroid release, suggesting that, in the lizard, ACTH does not induce any desensitization phenomenon. The angiotensin II analogue [Sar1, Val5] ANG II also stimulated corticosterone and aldosterone release in a dose-dependent manner; the stimulatory effects of ANG II on both steroids were very similar. These results indicate that, in lizards, ACTH plays a major role in the regulation of adrenal steroidogenesis. Since ANG II stimulates the production of gluco- and mineralocorticoids, our data raise the question of the existence of two cell types synthesizing corticosterone and aldosterone, respectively, in reptiles. PMID:2838698

  6. Ultrastructural features of the differentiating thyroid primordium in the sand lizard (Lacerta agilis L.) from the differentiation of the cellular cords to the formation of the follicular lumen.

    PubMed

    Rupik, Weronika; Kowalska, Magdalena; Swadźba, Elwira; Maślak, Robert

    2016-04-01

    The differentiation of the thyroid primordium of lacertilian species is poorly understood. The present study reports on the ultrastructural analysis of the developing thyroid primordium in the sand lizard (Lacerta agilis) during the early stages of differentiation. The early thyroid primordium of sand lizard embryos was composed of cellular cords that contained single cells with a giant lipid droplet, which were eliminated by specific autophagy (lipophagy). The follicular lumens at the periphery of the primordium differentiated even before the division of the cellular cords. When the single cells within the cords started to die through paraptosis, the adjacent cells started to polarise and junctional complexes began to form around them. After polarisation and clearing up after the formation of the lumens, the cellular cords divided into definitive follicles. The cellular cords in the central part of the primordium started to differentiate later than those at the periphery. The cellular cords divided into presumptive follicles first and only later differentiated into definitive follicles. During this process, a population of centrally located cells was removed through apoptosis to form the lumen. Although the follicular lumen in sand lizard embryos is differentiated by cavitation similar to that in the grass snake, there were very important differences during the early stages of the differentiation of the cellular cords and the formation of the thyroid follicles. PMID:26966051

  7. Trusted Objects

    SciTech Connect

    CAMPBELL,PHILIP L.; PIERSON,LYNDON G.; WITZKE,EDWARD L.

    1999-10-27

    In the world of computers a trusted object is a collection of possibly-sensitive data and programs that can be allowed to reside and execute on a computer, even on an adversary's machine. Beyond the scope of one computer we believe that network-based agents in high-consequence and highly reliable applications will depend on this approach, and that the basis for such objects is what we call ''faithful execution.''

  8. Radar imaging of binary near-Earth asteroid (357439) 2004 BL86

    NASA Astrophysics Data System (ADS)

    Benner, Lance A. M.; Brozovic, Marina; Giorgini, Jon D.; Taylor, Patrick A.; Howell, Ellen S.; Busch, Michael W.; Nolan, Michael C.; Jao, Joseph S.; Lee, Clement G.; Ford, H. Alyson; Ghigo, Frank D.

    2015-11-01

    We report radar imaging of near-Earth asteroid 2004 BL86 obtained at Goldstone, Arecibo, Green Bank, and elements of the Very Long Baseline Array between 2015 January 26-31. 2004 BL86 approached within 0.0080 au on January 26, the closest known approach by any object with an absolute magnitude brighter than ~19 until 2027. Prior to the encounter, virtually nothing was known about its physical properties other than its absolute magnitude of 19, which suggested a diameter within a factor of two of 500 m. 2004 BL86 was a very strong radar target that provided an outstanding opportunity for radar imaging and physical characterization. Delay-Doppler images with range resolutions as fine as 3.75 m placed thousands of pixels on the object and confirmed photometric results reported by Pravec et al. (2015, CBET 4063) that 2004 BL86 is a binary system. During the observations, the asteroid moved more than 90 deg and provided a range of viewing geometries. The bandwidth was relatively narrow on Jan. 26, reached a maximum on Jan. 27, and then narrowed on Jan. 28, a progression indicating that the subradar latitude moved across the equator during those days. The images reveal a rounded primary with an equatorial diameter of ~350 m, evidence for ridges, possible boulders, and a pronounced angular feature ~100 m in diameter near one of the poles. Images from Jan. 26 show arcs of radar-bright pixels on the approaching and receding limbs that extend well behind the trailing edge in the middle of the echo. This is the delay-Doppler signature of an oblate shape seen at least a few tens of degrees off the equator. A rough estimate for the diameter of the secondary is ~70 m and its narrow bandwidth is consistent with the 14-h orbital period reported by Pravec et al. (2015). The images are suitable for 3D shape, pole, orbit, and mass estimation. The observations utilized new data taking equipment at Green Bank to receive X-band (8560 MHz, 3.5 cm) transmissions from the 70 m DSS-14

  9. Catalog of SAS-2 gamma-ray observations (Fichtel, et al. 1990)

    NASA Technical Reports Server (NTRS)

    Warren, Wayne H., Jr.

    1990-01-01

    The machine-readable version of the catalog, as it is currently being distributed from the Astronomical Data Center, is described. The SAS-2 gamma ray catalog contains fluxes measured with the high energy gamma ray telescope flown aboard the second NASA Small Astronomy Satellite. The objects measured include various types of galaxies, quasi-stellar, and BL Lacertae objects, and pulsars. The catalog contains separate files for galaxies, pulsars, other objects, notes, and references.

  10. Complete Genome Sequence of the Probiotic Lactobacillus casei Strain BL23▿

    PubMed Central

    Mazé, Alain; Boël, Grégory; Zúñiga, Manuel; Bourand, Alexa; Loux, Valentin; Yebra, Maria Jesus; Monedero, Vicente; Correia, Karine; Jacques, Noémie; Beaufils, Sophie; Poncet, Sandrine; Joyet, Philippe; Milohanic, Eliane; Casarégola, Serge; Auffray, Yanick; Pérez-Martínez, Gaspar; Gibrat, Jean-François; Zagorec, Monique; Francke, Christof; Hartke, Axel; Deutscher, Josef

    2010-01-01

    The entire genome of Lactobacillus casei BL23, a strain with probiotic properties, has been sequenced. The genomes of BL23 and the industrially used probiotic strain Shirota YIT 9029 (Yakult) seem to be very similar. PMID:20348264