Blazar Times - No. 60 - December 2003
The Blazar Times
A Research Newsletter Dedicated to the BL Lac and Blazar Phenomena
No. 60 - December 2003 Editor: Travis A. Rector (


Journal Abstracts 1

Abstract Guidelines 4

Journal Abstracts

Radio Identification of the X-ray Jet in the z=4.3 Quasar GB 1508+5714

C. C. Cheung1

1 Department of Physics, MS 057, Brandeis University, Waltham, MA 02454

The recent discovery of an X-ray jet in the z=4.3 quasar GB 1508+5714 by Yuan et al. (astro-ph/0309318) and Siemiginowska et al. (astro-ph/0310241) prompted a search for its radio counterpart. Here, we report the successful discovery of faint radio emission from the jet at 1.4 GHz using archival VLA data. The X-ray emission is best interpreted as inverse Compton (IC) emission off the CMB as discussed by the previous investigators. In this scenario, its high X-ray to radio monochromatic luminosity ratio, compared to previously detected IC/CMB X-ray jets at lower redshift, is a natural consequence of its high redshift.

Accepted by ApJL

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BeppoSAX Observations of 1-Jy BL Lacertae Objects - II

Paolo Padovani1,2, Luigi Costamante3,4, Paolo Giommi5, Gabriele Ghisellini6, Annalisa Celotti7, and Anna Wolter8

1 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore MD 21218, USA
2 Affiliated with the Space Telescope Division of the European Space Agency, ESTEC, Noordwijk, The Netherlands
3 Università degli Studi di Milano, Via Celoria 16, I-20133 Milano, Italy
4 Max-Planck Institute für Kernphysik, Postfach 10 39 80, D-69029 Heidelberg (current address)
5 ASI Science Data Center, c/o ESRIN, Via G. Galilei, I-00044 Frascati, Italy
6 Osservatorio Astronomico di Brera, Via Bianchi 46, I-23807 Merate, Italy
7 SISSA, via Beirut 2-4, I-34014 Trieste, Italy
8 Osservatorio Astronomico di Brera, Via Brera 28, I-20121 Milano, Italy

We present new BeppoSAX LECS and MECS observations, covering the energy range 0.1- 10 keV (observer's frame), of four BL Lacertae objects selected from the 1 Jy sample. All sources display a flat (ax ~ 0.7) X-ray spectrum, which we interpret as inverse Compton emission. One object shows evidence for a low-energy steepening (Dax ~ 0.9) which is likely due to the synchrotron component merging into the inverse Compton one around ~ 2 keV. A variable synchrotron tail would explain why the ROSAT spectra of our sources are typically steeper than the BeppoSAX ones (Dax ~ 0.7). The broad-band spectral energy distributions fully confirm this picture and model fits using a synchrotron inverse Compton model allow us to derive the physical parameters (intrinsic power, magnetic field, etc.) of our sources. By combining the results of this paper with those previously obtained on other sources we present a detailed study of the BeppoSAX properties of a well-defined sub-sample of 14 X-ray bright (fx(0.1 - 10 keV) > 3 ×10-12 erg cm-2 s-1) 1-Jy BL Lacs. We find a very tight proportionality between nearly simultaneous radio and X-ray powers for the 1-Jy sources in which the X-ray band is dominated by inverse Compton emission, which points to a strong link between X-ray and radio emission components in these objects.

Accepted by The Monthly Notices of the Royal Astronomical Society

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Constraints on the Very High Energy Emission from BL Lacertae Objects

D. Horan1, H. M. Badran2, I. H. Bond3, P. J. Boyle4, S. M. Bradbury3, J. H. Buckley5, D. A. Carter-Lewis6, M. Catanese1, O. Celik7, W. Cui8, M. Daniel8, M. D'Vali3, I. de la Calle Perez3, C. Duke9, A. Falcone8, D. J. Fegan10, S. J. Fegan1, J. P. Finley8, L. F. Fortson4, J. A. Gaidos8, S. Gammell10, K. Gibbs1, G. H. Gillanders11, J. Grube3, J. Hall12, T. A. Hall13, D. Hanna14, A. M. Hillas3, J. Holder3, A. Jarvis7, M. Jordan5, G. E. Kenny11, M. Kertzman15, D. Kieda12, J. Kildea15, J. Knapp3, K. Kosack5, H. Krawczynski5, F. Krennrich6, M. J. Lang11, S. Le Bohec6, E. Linton4, J. Lloyd-Evans3, A. Milovanovic3, P. Moriarty16, D. Muller4, T. Nagai12, S. Nolan8, R. A. Ong7, R. Pallassini3, D. Petry17, B. Power-Mooney10, J. Quinn10, M. Quinn16, K. Ragan14, P. Rebillot5, P. T. Reynolds18, H. J. Rose3, M. Schroedter1, G. H. Sembroski8, S. P. Swordy4, A. Syson3, V. V. Vassiliev12, S. P. Wakely4, G. Walker12, T. C. Weekes1 and J. Zweerink7

1 Fred Lawrence Whipple Observatory, Harvard-Smithsonian CfA, P.O. Box 97, Amado, AZ 85645-0097
2 Physics Department, Tanta University, Tanta, Egypt
3 Department of Physics, University of Leeds, Leeds, LS2 9JT, Yorkshire, England, UK
4 Enrico Fermi Institute, University of Chicago, Chicago, IL 60637, USA
5 Department of Physics, Washington University, St. Louis, MO 63130, USA
6 Department of Physics and Astronomy, Iowa State University, Ames, IA 50011-3160, USA
7 Department of Physics, University of California, Los Angeles, CA 90095-1562, USA
8 Department of Physics, Purdue University, West Lafayette, IN 47907, USA
9 Department of Physics, Grinnell College, Grinnell, IA 50112-1690, USA
10 Experimental Physics Department, National University of Ireland, Belfield, Dublin 4, Ireland
11 Department of Physics, National University of Ireland, Galway, Ireland
12 High Energy Astrophysics Institute, University of Utah, Salt Lake City, UT 84112, USA
13 Department of Physics and Astronomy, University of Arkansas at Little Rock, Little Rock, AR 72204-1099, USA
14 Physics Department, McGill University, Montreál, QC H3A 2T8, Canada
15 Department of Physics and Astronomy, DePauw University, Greencastle, IN 46135-0037, USA
16 School of Science, Galway-Mayo Institute of Technology, Galway, Ireland
17 University of Maryland, Baltimore County and NASA/GSFC, USA
18 Department of Applied Physics and Instrumentation, Cork Institute of Technology, Cork, Ireland

We present results from observations of 29 BL Lacertae objects, taken with the Whipple Observatory 10 m Gamma-Ray Telescope between 1995 and 2000. The observed objects are mostly at low redshift (z < 0.2) but observations of objects of z up to 0.444 are also reported. Five of the objects are EGRET sources and two are unconfirmed TeV sources. Three of the confirmed sources of extragalactic TeV gamma rays were originally observed as part of this survey and have been reported elsewhere. No significant excesses are detected from any of the other objects observed, on time scales of days, months or years. We report 99.9% confidence level flux upper limits for the objects for each observing season. The flux upper limits are typically 20% of the Crab flux although, for some sources, limits as sensitive as 6% of the Crab flux were derived. The results are consistent with the synchrotron-self-Compton (SSC) model predictions considered in this work.

Accepted by ApJ

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Jet Formation in BL Lacertae Objects with Different Accretion Modes

Xinwu Cao

Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China

We estimate the masses of massive black holes in BL Lac objects from their host galaxy luminosity. The power of jets and central optical ionizing luminosity for a sample of BL Lac objects are derived from their extended radio emission and the narrow-line emission, respectively. The maximal jet power can be extracted from a standard thin accretion disk/spinning black hole is calculated as a function of dimensionless accretion rate [m\dot] ([m\dot] = [M\dot]/[M\dot]Edd). Comparing with the derived jet power, we find that the accretion disks in most BL Lac objects should not be standard accretion disks. For a pure advection dominated accretion flow (ADAF), there is an upper limit on its optical continuum luminosity due to the existence of an upper limit [m\dot]crit on the accretion rate. It is found that a pure ADAF is too faint to produce the optical ionizing luminosity of BL Lac objects derived from their narrow-line luminosity. We propose that an ADAF is present in the inner region of the disk and it becomes a standard thin disk in the outer region in most BL Lac objects, i.e., ADAF+SD(standard disk) scenario. This ADAF+SD scenario can explain both the jet power and optical ionizing continuum emission of these BL Lac objects. The inferred transition radii between the inner ADAF and outer SD are in the range of 40-150 GMbh/c2, if the disks are accreting at the rate [m\dot] = 0.01.

Accepted by ApJ

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Black Hole Masses and Doppler Factors of g-ray Active Galactic Nuclei

Zhong-Hui Fan, Xinwu Cao

Shanghai Astronomical Observatory, Chinese Academy of Sciences, Shanghai 200030, China

The sizes of the broad-line regions (BLRs) in g-ray active galactic nuclei (AGNs) are estimated from their optical continuum luminosity by using the empirical relation between RBLR and Ll,opt. Using the broad emission line data, we derive the photon energy density in the relativistic blobs near the massive black holes in AGNs. We calculate the power of the broad-line photons Compton up-scattered by the relativistic electrons in the blobs. Compared with observed g-ray emission data, the Doppler factors d of the blobs for a sample of 36 g-ray AGNs are derived, which are in the range of ~ 3-17. We estimate the central black hole masses of these g-ray AGNs from the sizes of the BLR and the broad line widths. It is found that the black hole masses are in the range of ~ 108-1010M\odot. A significant correlation is found between the Doppler factor d and the core dominance parameter R. The results are consistent with the external radiation Compton (ERC) models for g-ray emission from AGNs. The soft seed photons are probably from the broad-line regions.

Accepted by ApJ

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Abstract Guidelines

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On 1 Dec 2003, 16:31.