Blazar Times - No. 67 - March 2005
The Blazar Times
A Research Newsletter Dedicated to the BL Lac and Blazar Phenomena
No. 67 - March 2005 Editor: Travis A. Rector (


Journal Abstracts 1
Abstract Guidelines 4

Journal Abstracts
Intrinsic Curvature in the X-ray Spectra of BL Lacertae Objects
Eric S. Perlman1,2, Greg Madejski3,4, Markos Georganopoulos1,5, Karl Andersson3,6, Timothy Daugherty1, Julian H. Krolik2, Travis Rector7,8, John T. Stocke9, Paolo Padovani10,11, Anuradha Koratkar10,12, Stefan Wagner13, Margo Aller14, Hugh Aller14, Mark G. Allen15
1 Department of Physics, Joint Center for Astrophysics, University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
2 Department of Physics and Astronomy, Johns Hopkins University, 3400 North Charles Street, Baltimore, MD 21218, USA
3 Stanford Linear Accelerator Center, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
4 Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, Stanford, CA 94305, USA
5 NASA's Goddard Space Flight Center, Mail Code 660, Greenbelt, MD, 20771, USA
6 Cosmology, Particle Astrophysics & String Theory (CoPS), AlbaNova University Center, Department of Physics, Stockholm University, Roslagstullsbacken 21, S-10691, Stockholm, Sweden
7 National Radio Astronomy Observatory, P. O. Box O, Socorro, NM 87801, USA
8 Current Address: Department of Physics and Astronomy, University of Alaska - Anchorage, 3211 Providence Drive, Anchorage, AK 99508, USA
9 Center for Astrophysics and Space Astronomy, University of Colorado, Campus Box 389, Boulder, CO 80309, USA
10 Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD 21218, USA
11 Current Address: European Southern Observatory, Karl-Schwarzchild Strasse 2, D-85748 Garching bei Munchen, Germany
12 Current Address: Goddard Earth Sciences and Technology Center, 3.002 South Campus, University of Maryland-Baltimore County, 1000 Hilltop Circle, Baltimore, MD 21250, USA
13 Landessternwarte Heidelberg, Koenigstuhl, Heidelberg, 69117, Germany
14 Department of Astronomy, University of Michigan, Ann Arbor, MI, 48109, USA
15 Centre de Donnees Astronomique, 11 Rue de l'Universite, 67000 Strasbourg, France
We report results from XMM-Newton observations of thirteen X-ray bright BL Lacertae objects, selected from the Einstein Slew Survey sample. The survey was designed to look for evidence of departures of the X-ray spectra from a simple power law shape (i.e., curvature and/or line features), and to find objects worthy of deeper study. Our data are generally well fit by power-law models, with three cases having hard (G < 2; dN/dE E-G) spectra that indicate synchrotron peaks at E \mathrel\rlap ~ > 5 keV. Previous data had suggested a presence of absorption features in the X-ray spectra of some BL Lacs. In contrast, none of these spectra show convincing examples of line features, either in absorption or emission, suggesting that such features are rare amongst BL Lacs, or, more likely, artifacts caused by instrumental effects. We find significant evidence for intrinsic curvature (steepening by dG/ d(log E) = 0.4 0.15) in fourteen of the seventeen X-ray spectra. This cannot be explained satisfactorily via excess absorption, since the curvature is essentially constant from 0.5-6 keV, an observation which is inconsistent with the modest amounts of absorption that would be required. We use the XMM-Newton Optical Monitor data with concurrent radio monitoring to derive broadband spectral energy distributions and peak frequency estimates. From these we examine models of synchrotron emission and model the spectral curvature we see as the result of episodic particle acceleration.
Accepted by ApJ, to appear 1 June 2005
For preprints contact:

Are Quasar Jets Dominated by Poynting Flux?
Marek Sikora1, Mitchell C. Begelman2,  Greg Madejski3, and Jean-Pierre Lasota4
1 Nicolaus Copernicus Astronomical Center, Bartycka 18, 00-716 Warsaw, Poland
2 JILA, Campus Box 440, Univ. of Colorado, Boulder, CO 80309 USA
3 Stanford Linear Accelerator Center and Kavli Institute for Particle Astrophysics and Cosmology, Stanford University, 2575 Sand Hill Road, Menlo Park, CA 94025, USA
4 Institut d'Astrophysique de Paris, 98bis boulevard Arago, 75014 Paris, France
The formation of relativistic astrophysical jets is presumably mediated by magnetic fields threading accretion disks and central, rapidly rotating objects. As it is accelerated by magnetic stresses, the jet's kinetic energy flux grows at the expense of its Poynting flux. However, it is unclear how efficient is the conversion from magnetic to kinetic energy and whether there are any observational signatures of this process. We address this issue in the context of jets in quasars. Using data from all spatial scales, we demonstrate that in these objects the conversion from Poynting-flux-dominated to matter-dominated jets is very likely to take place closer to the black hole than the region where most of the Doppler boosted radiation observed in blazars is produced. We briefly discuss the possibility that blazar activity can be induced by global MHD instabilities, e.g., via the production of localized velocity gradients that lead to dissipative events such as shocks or magnetic reconnection, where acceleration of relativistic particles and production of non-thermal flares is taking place.
Accepted by ApJ
For preprints contact:

A Northern Survey of Gamma-Ray Blazar Candidates
David Sowards-Emmerd1,2, Roger W. Romani1, Peter F. Michelson1,2, Stephen E. Healey1,2  and Patrick L. Nolan1
1 Department of Physics, Stanford University, Stanford, CA 94305
2 Stanford Linear Accelerator Center, Stanford, CA 94039-4349
In preparation for GLAST, we have compiled a sample of blazar candidates to increase the pool of well studied AGN from which GLAST counterparts will be drawn. Sources were selected with our Figure of Merit (FoM) ranking; thus, they have radio and X-ray properties very similar to the EGRET blazars. Spectroscopic confirmation of these candidates is in progress, and more than 70% of these objects have been identified as flat spectrum radio quasars and BL Lac objects. We present ~ 250 new optical blazar identifications based on McDonald Observatory spectroscopy, 224 with redshifts. Of these, 167 are in our FoM-selected set.
To motivate the g-ray nature of these objects, we analyzed the current release of the EGRET data for possible point sources at their radio positions. We develop two distinct methods to combine multiple EGRET observations of a sky position into a single detection significance. We report a detection of the signal of the set of blazar candidates in the EGRET data at the > 3s level by both techniques. We predict that the majority of these blazar candidates will be found by GLAST due to its increased sensitivity, duty cycle and resolving power.
Accepted by ApJ
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For preprints via ftp or WWW:
Abstract Guidelines
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