Blazar Variability Workshop II: Entering the GLAST Era

10-12 April, 2005

Florida International University

Miami, Florida

 

 

 

 

 

Blazar Variability Workshop II: Entering the GLAST Era

In Honor of Dr. Hugh Aller

University of Michigan

 

Hugh Duncan Aller has spent his entire life immersed in the sometimes frustrating, often puzzling, but always fascinating field of astronomy. He was born in 1942 in Cambridge, Massachusetts where his father, Lawrence, who later became renowned for his work in the areas of planetary nebulae and stellar atmospheres, had accepted a junior level position on the Harvard faculty. Hugh spent his early years as part of the family of an itinerant astronomer, traveling from such diverse locations as Pasadena, California to remote observing sites, as his father's work dictated. The family finally settled in Ann Arbor, Michigan when Lawrence joined the faculty there, and Hugh spent many of his grammar school years living in an apartment that physically adjoined the Observatory itself. The building at that time contained the University's primary telescope, and the building itself and the people who worked there were all well known to and by him in his childhood years.  All of this contributed to making astronomy the focus of his world.

            Hugh's interests, even in his high school years, included both electrical engineering and astronomy, so it was quite natural that he found his life's occupation in radio astronomy. Except for a short time in Australia, he spent his college and post grad years as a student at the University of Michigan, and subsequently went on to faculty positions there ranging from lecturer to department chairman. His primary mentor during his grad school years was Fred Haddock, who directed the Radio Astronomy group, and who was responsible for the construction of the Michigan 26-meter radio telescope in the late 1950s; this facility subsequently became known as UMRAO. Fred supervised and encouraged the thesis work by Bill Dent using this instrument which identified the presence of large variations in the radio flux of extragalactic sources, and shortly thereafter the thesis work by Hugh himself leading to the discovery of polarization variability in these objects. Hugh's career has subsequently been devoted to the study of radioband variability, and his work has, without question, enhanced our understanding of the objects that form the focus of this conference.

             

Local Organizing Committee

Scientific Organizing Committee

 

Held at the Kovens Conference Center

Florida International University

Miami, Florida

 

 

Blazar Variability Workshop II: Entering the GLAST ERA

Saturday April 9

 

18:00 – 22:00 Registration / Hotel Lobby

18:00 - 21:00 Reception / Hotel

 

Sunday April 10

 

8:00-9:00 Shuttle transportation to Conference Center

9:00          Introductory Remarks and Welcome – Webb                                         10 min.

9:10          Opening Address – Dr. Mark Rosenberg, Provost FIU                         15 min.

9:30          Multifrequency Observations of Blazars - Webb                                30 min

                 Discussion (10 min)

10:10        Multiwavelength Observations of 3C 66A in 2003/2004 – Boettcher20 min

                 Discussion (5 min)

10:35        Modeling the SED variability of 3C 66A in 2003/2004 – Joshi         10 min

                 Discussion (5 min)

10:50        Coffee Break/Posters                                                                              45 min

11:35        Variable Sources in Active Galactic Nuclei – Hagen-Thorn               20 min

                 Discussion (5 min)

12:00        Lunch/Posters                                                                                         90 min

  1:30        Radio-Band Variability  - M. Aller                                                       30 min.

                 Discussion (10 min)

  2:10        Blazar Optical Variability: Past, Present and Future – Miller          30 min

                 Discussion (10 min)

  2:50        The Next Outburst of OJ 287  - Nilsson                                               10 min

                 Discussion (5 min)

  3:05        Caveats and Pitfalls in AGN Light Curve Analysis - Markowitz       10 min

                 Discussion (5 min)

  3:20        Multicolor Microvariability in 0716+17 in 2003 – Carini                   10 min

                 Discussion (5 min)

  3:35        Coffee Break/Posters                                                                              30 min

  4:05        QSO Astrophysics with the Space Interferometry Mission

                                                                                                                – Londish  10 min

                 Discussion (5 min)

  4:20        Search for a Seasonal Cycle in the Intraday Variability of Blazar

                                                                                      0954+658– Fuhrman         10 min

                 Discussion (5 min)                        

  4:35        X-Ray Variability of Blazars - Sambruna                                            30 min

                 Discussion (10 min)

  5:15        Adjourn Meeting

  5:30       Shuttle to hotel

                Dinner/Evening Free       

 

Monday April 11

 

8:00-9:00 Shuttle transportation to Conference Center

9:00          Conference announcements etc.           – Webb                                       10 min.

9:10          3C 273: Long time X-Ray Variability – McHardy                               10 min

                 Discussion (5 min)

9:25          HXMT- A Chinese High Energy Astrophysics Mission – Li              10 min

                 Discussion (5 min)

9:40          Gamma-Ray Observations of Blazars – Thompson                             30 min

                 Discussion (10 min)

10:20        Coffee Break/Posters                                                                               40 min

11:00        AGN Variability and the Emerging AGN/BHXRB Paradigm

                                                                                                     – Uttley                 10 min       

                 Discussion (5 min)                                  

11:15        Blazars at MeV Energies: An Update – Collmar                                 10 min

                 Discussion (5 min)

11:30        Decelerating Flows and the Spectra of TeV Blazars – Kazanas         10 min

                 Discussion (5 min)    

11:45        Lunch/Posters/Conference Picture                                                        95 min

  1:20        Ground-Based GeV and TeV Gamma-Rays Observations of Blazars

                                                                                            - Krawcynski                  30 min

                 Discussion (10 min)     

  2:00        High Energy Observations of Blazars with HESS – Wagner              20 min

                 Discussion (5 min)

  2:30        Coffee Break/Posters                                                                               30 min

  3:00        Structure and Evolution of Blazar Jets: Recent Results from VLBI

                                                                       Surveys - Lister                                  30 min

                 Discussion (10 min)     

  3:40        Fine-Scale Structure of Blazars - Kovalev                                            10 min

                 Discussion (5 min)

  3:55         Jet Kinematics of AGNs at High Frequencies - Jorstad                     15 min

                  Discussion (5 min)

  4:15        Probing the Compact Jets of Blazars with Imaging – Marscher        30 min.

                 Discussion (10 min)

  5:00-5:15 Poster Viewing                                                                                      

 

DINNER – AT CONFERENCE CENTER

 

  5:15 – 5:30     Shuttle transportation to Hotel

  7:15 – 7:30     Shuttle Transportation Between Hotel and Conference Center

  7:30 – 8:00     Reception –Conference Center

  8:00 -              Banquet – Conference Center

  9:00 – 10:20   Program Events

10:30 – 10:45   Shuttle Transportation to Hotel

 

 

Tuesday April 12

 

8:00-9:00 Shuttle transportation to Conference Center                                                   

9:00-9:05 Announcements – Webb                                                                     5 min

9:05          Disk-Jet Connection – Vlahakis                                                    30 min

                 Discussion (10 min)

9:45          Inverse Compton Models: Richer than We Thought

                                                                                 - Georganopoulos           10 min 

                 Discussion (5 min)

10:00        The Capabilities of the GLAST LAT for Blazar Variability

                                                                          Studies – McInery                10 min

                 Discussion (5 min)

10:15        Coffee Break/Posters                                                                      30 min

10:45        Instabilities in Disks and Jets - Wiita                                          30 min

                 Discussion (10 min)

11:25        Intrinsic Curvature in the X-Ray Spectrum of BL Lac Objects

                                                                             - Perlman                           10 min

                 Discussion (5 min)

11:40        Lunch/Posters/                                                                               90 min

  1:10        Magnetically Dominated Accretion and Jet Flows – Meier      30 min

                 Discussion (10 min)

  1:50        Instabilities and Structure in Astrophysical Jets - Hardee       30 min

                 Discussion (10 min)

  2:40         Discussion (5 min)                                           

  2:45        High Energy Observations of Blazars: The Future                 30 min

                                                                                    - Madejski 

                 Discussion (10 min)

  3:25        Coffee Break/Posters                                                                     35 min

  4:00        Conference Summary – Hugh Aller                                            30 min

                 Discussion (10 min)

  4:40        Conference Wrap-up,Final Poster Viewing/Poster Removal/Discussion

  4:45        Shuttle Transportation to Hotel

 

 

 

Invited Abstracts

1.

Multi-frequency Observations of Blazars

James R. Webb

Director, SARA Observatory

Dept. of Physics

Florida International University

 

We will attempt to condense 25 years of multi-frequency observations of blazars into 20 minutes.  We examine sources observed, observational triggers, collaborations, and multi-frequency results.  Especially, what these results have in common, and what sources show disparate behavior.  We will also propose strategies and methods for future collaboration and discuss sticking points for large consortia. I will summarize the work of the WEBT collaboration of which many of you are contributors.   Finally, we will attempt to frame the MW results in terms of generic jet models. This work was supported by NSF grant # AST-0324238.

 

 

2.

Radio-Band Variability

M. F Aller, H. D. Aller, P. A Hughes, & M. Zhao

University of Michigan

 

We describe the characteristic properties of centimeter-band flux and linear polarization variability, with emphasis on results obtained from the long-term UMRAO monitoring program. We discuss these data within the context of current competing theories to interpret variability measurements, and illustrate how such data, combined with supplementary circular polarization observations and centimeter-band VLBA monitoring of highly active sources, can be used to probe jet physics and place constraints on model parameters. The well-sampled radio-band variability is temporally associated with high energy outbursts (X-ray to TeV) in some, but not all, objects, and examples are shown. Attempts to relate the jet properties revealed by the monitoring data to the powering SMBH and associated accretion disk are briefly discussed. This work was supported in part by NSF grants AST-0307629 and AST-0205105, and by a series of supplementary grants for ground-based support from NASA.

 

3.

Blazar Optical Variability: Past, Present and Future

H. Richard Miller

Georgia State University

 

A review of the successes (and failures) of blazar optical monitoring programs will be presented. The value of these past efforts will be discussed.  Recent results from

several different campaigns will be presented along with the implications for different models for the mechanisms responsible for these variations.   Possible future directions for investigating the nature of the optical variability will be presented.

 

4.

X-ray Variability of Blazars

Rita Sambruna,

George Mason University

 

High-energy X-ray emission from blazars probes the site(s) in the relativistic jet with the most energetic particles and fields. X-ray variability, and correlated X-ray and gamma-ray TeV variability, is an important tool to investigate the structure of the pc-scale jet and to discriminate among models for the production of the emission at the

highest energies. In this talk, I will review results from various multifrequency campaigns of blazars at X-rays from RXTE and SAX, and summarize recent observations with XMM-Newton which are shedding new light on our understanding of these sources. In particular, I will review recent work on correlated X-ray and TeV variability of Mrk~501,

based on archival RXTE, Whipple, and HEGRA data. The main results of this work are: 1) Long-term (~ monthly-yearly) correlation between X-ray and TeV variability is confirmed. However, the correlation is present only when the source is in a high X-ray state and absent during low states; and 2) "Orphan" flares are observed at TeV energies, with no counterparts at X-rays.   Support from an NSF CAREER grant is acknowledged.

 

5.

Gamma-Ray Observations of Blazars

David Thompson
  NASA Goddard Space Flight Center
 Code 661, NASA/GSFC
Greenbelt, MD 20771

 

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

 

6.

Ground Based GeV and TeV Gamma-Ray Observations of Blazars

H. Krawczynski,

Phys. Dept. Washington University in St. Louis (MO)

 

In this talk, I will summarize the status of ground based GeV and TeV gamma-ray observatories, i.e., small field of view solar array type experiments and imaging atmospheric Cherenkov telescopes, and wide field of view shower front sampling experiments. After highlighting the relative strengths and weaknesses of these telescopes, I will discuss the science topics that can be addressed with GeV and TeV gamma-ray observations of blazars, and give an overview over recent observational and theoretical

results.

 

7. 

Structure and Evolution of Blazar Jets: Recent Results from VLBI Surveys
Matt Lister
Purdue University
 

            Blazars are an unusually rare type of AGN that are subject to a variety of complex selection biases as a result of their relativistic jet speeds and end-on orientations. Although much insight into jet physics can be gained from studying small numbers of individual AGN at high resolution with VLBI techniques, there are many issues that can

only be addressed via large, statistical studies of blazars. Since 1994 we have been using the VLBA to observe the brightest, most compact blazars in the northern sky at 15 GHz. Our current program (MOJAVE), is obtaining multi-epoch linear and circular polarization VLBA images of 133 AGN in order to better understand long-term jet kinematics and magnetic field evolution. We discuss several recent findings from MOJAVE and other VLBI surveys, including evidence strongly confirming the connection between the broad-line properties of blazars and their pc-scale magnetic field structure.

8.

Probing the Compact Jets of Blazars with Imaging and Variability

Alan Marscher
 Institute for Astrophysical Research
Boston University

 

Intensive multiwavelength monitoring of blazars probes the regions of the jets where the most exciting action is taking place. Combining light curves of total and polarized flux with sequences of VLBI images provides as complete a picture as possible of the nonthermal activity. I will show results of recent programs that use this technique and will discuss both what we have learned and what the prospects are for enhancing such programs.

 

9.

Disk-Jet Connection

Nektarios Vlahakis

University of Athens, Greece


            AGN jets are collimated, ultra-relativistic flows that emanate from accretion disks around super-massive black holes. Electromagnetic stresses are the most plausible candidate for extracting energy at the source and converting it into outflow kinetic energy. They also extract angular momentum from the disk contributing to the accretion. Among the questions that need to be answered in order for these processes to be well understood are: How the conditions near the disk determine the terminal Lorentz factor of the jet? What is the asymptotic value of the Poynting-to-matter energy flux ratio? Can we
explain the apparent kinematics of the observed jet components? Is the disk stable in the case when the outflow is the dominant mode of angular momentum transport? I review new developments that help to shed light on these questions.

10.

Instabilities in Disks and Jets

Paul Wiita
 Dept. Physics & Astronomy
Georgia State University

 

Although shocks in jets probably dominate the major flares seen in Blazars, various processes in accretion disks can produce variability on a wide range of timescales. The relevance of these processes to observations across different wavebands will be discussed.

 

11.

Magnetically-Dominated Jets and Accretion Flows

David Meier

California Institute of Technology/Jet Propulsion
Laboratory

 

I will discuss two aspects of blazars and blazar-like sources that involve
magnetically-dominated magnetohydrodynamics flows: Poynting-flux-dominated
jets and the magnetically-dominated accretion flows (MDAFs) that may create them. Three-dimensional simulations of Poynting jets show that they produce distinctive observational signatures: helical kinks or wiggles, with plasma flowing along the helical magnetic backbone.  The instability that creates kinked jets is current-driven (related to the strong-field pinch), rather than Kelvin-Helmholtz driven, and saturates into laminar helical flow rather than turbulence. Identification of plasma blobs traveling along a helical pattern would be an indication that the helical kink instability is the main driver creating helical jets and that strong magnetic fields may be at work in such sources.

It is widely believed that jets in blazars are launched by magnetic processes in plasma that is accreting onto black holes. While numerical simulations of turbulent MHD accretion flows have begun to show some jet launching, the properties of these simulated jets and disks do not yet explain those in extensively-observed, jet-producing black hole systems. The galactic black hole candidates, in particular, provide a wealth of time-dependent information on how accretion flows behave when jets are, or are not, launched. Based on these observations, I have proposed a new type of accretion flow (the MDAF) that unites current theories of black hole accretion, magnetospheres, and jet-production. The model explains qualitatively and quantitatively the behavior of both disks and jets
and has implications for black hole systems of any size, including blazars.

 

 

 

 

 

 

 

 

12.

Instability and Structure in Astrophysical Jets

Philip Hardee
 Dept. Physics & Astronomy
University of Alabama

            The basic current driven (CD) and surface driven (KH) stability properties of jets and the expected resulting astrophysical jet structures will be reviewed. The motion and appearance of the resulting structures and the uses of observed structure will be explored. Observed structure and motion may indicate whether or where jets are magnetically or kinetically dominated.

 

13.

High Energy Observations of Blazars: The Future

Greg Madejski
 Stanford Linear Accelerator Center

 

In my talk, I will discuss the current status and progress of Blazar research that resulted from observations in the high energy band. I also will give the prospects for the future observations with the upcoming satellite-based X-ray and gamma-ray sensitive instruments.

 

 

 

 

 

Contributed Orals

 

1.                                                                                                                             

Multiwavelength Observations of 3C66A in 2003/2004

Markus Boettcher

Physics and Astronomy

Ohio University

 

        The BL Lac object 3C66A was the target of an intensive multiwavelength campaign in 2003/2004. Major results of this campaign included the characterization of optical intraday variability and peculiar optical spectral variability, reminiscent of spectral hysteresis, as well as the extraction of several snapshot SEDs which confirm the intermediate BL Lac nature of the source. Here, we describe the observational results and model independent constraints derived from them.

 

2.                                                                                                                            

Modeling the SED and Variability of 3C66A in 2003/2004
Manasvita Joshi
 Department of Physics and Astronomy
Ohio University

 
            The BL Lac object 3C66A was the target of an intensive multiwavelength campaign in 2003/2004. As a result of  this campaign, peculiar optical spectral variability, reminiscent of spectral hysteresis, was observed. Here, we use a time-dependent leptonic jet model to reproduce simultaneously the SED and optical spectral variability observed during our multiwavelength campaign. Predictions concerning potentially observable X-ray spectral variability and gamma-ray emission will be presented.

 

3.                                                                                                                              

Variable Sources in Active Galactic Nuclei

Vladimir Hagen-Thorn

Astronomical Department
 St.-Petersburg State University


            The method of separation of the variable component radiation from summary observed flux of AGN is descrbed. The advantage of the method based on studying of photometric variability is that information about spectral energy distribution of the variable source may be found without knowledge of its contribution to summary radiation. The results of application of the method to several blazars are given.

 

 

 

 

 

 

4.                                                                                                                          

The Next Outburst of OJ 287

Kari Nilsson

Tuorla Observatory Finland

 

The BL Lac object OJ 287 (z=0.306) shows double peaked outbursts roughly every 12 years indicating a possible double black hole system. The next outburst is expected to happen during 2006. We will shortly describe the planned observations for 2005-2008 to test the various models proposed for OJ 287.

 

5.                                                                                                                               

Caveats and Pitfalls in AGN Light Curve Variability Analysis

Alex Markowitz
 X-ray Astrophysics Branch,
NASA/Goddard Space Flight Center


            I will review caveats and pitfalls associated with timing analysis of light curves, such as those to be obtained by GLAST. This will include characterization of "red-noise" variability, proper QPO searches and use of tools such as the structure function, AGN
stationarity, and using Monte Carlo simulations to assess statistical significance of results.

 

6.

Multicolor Microvariability in 0716+714 in 2003

Michael Carini

Western Kentucky University

 

The Blazar S5 0716+714 was the subject of an intensive 5 night multicolor observing campaign in March, 2003. Observations in the B and I filter were obtained with the 42 Hall telescope at Lowell Observatory. Light curves with duration of 8-10 hours and sampling rates of approximately 8 minutes in each filter were obtained. Variations were observed with timescales ranging from days to 1 hour and amplitudes

ranging from 0.8 magnitudes to 0.03 magnitudes. No evidence for lags greater than 10 minutes between wavebands was found. Evidence for color dependence was found in some, but not all of the observed variations, with the shortest timescale variations showing the greatest evidence for color dependent variability.

 

7.                                                                                                                              

Quasar Astrophysics with the Space Interferometry Mission

Diana Londish
JPL /Caltech,

The Space Interferometry Mission (SIM) will be the first optical
interferometer capable of precision astrometry on quasars.Blazars brighter than 15th mag will be used as targets to answer questions such as: Does the most compact optical emission come from an accretion disk or from a relativistic jet? Is the separation of the radio core and optical photocentre stable at the level of a few micorarcseconds or does it change? Is there a shift in the optical photocentre as a function of color? We are gathering results from variability studies to select the best and brightest SIM targets.

 

8.

Search for a Seasonal Cycle in the Intraday Variability of Blazar
0954+658

Lars Fuhrmann
Institute/Department: Physics Department and Astronomical Observatory,
University of Perugia

 

9.

3C273: Long Timescale X-ray Variability and (possibly) new INTEGRAL observations

Ian McHardy

 University of Southampton,
School of Physics and Astronomy
 UK

10.

HXMT — A Chinese High Energy Astrophysics Mission

Tipei Li
 Institute of High Energy Physics, Chinese Academy of  Sciences
Department of Physics and Center for Astrophysics, Tsinghua University

Beijing, China


          The high sensitivity and high resolution imaging of hard X-rays is a difficult task in high-energy astronomy, which is currently undertaken by position-sensitive detectors and coded masks. A new inversion technique, the direct demodulation method, has been developed. With this technique, wide field and high-resolution images can be derived from scanning data of a simple collimated detector. Experiment, balloon-borne observation and analyzing simulated and real astronomical data have confirmed the feasibility of this technique. Based the development of methodology and instrumentation, a high energy astrophysics mission — Hard X-ray Modulation Telescope (HXMT) has been proposed and selected as a project under the Major State Basic Research Program in China for Phase-A study. In the energy range of 20 - 250 keV, HXMT can perform full-sky hard X-ray survey with angular resolution < 5 and sensitivity much better than
Integral/IBIS and Swift/BAT, and can make high signal-to-noise ratio pointing observations of scientific hot spot sources, including Blazars, with sensitivity ~3.0Χ10-7 ph cm-2 s-1 keV-1 for detailed temporal and spectral studies. Hopefully the HXMT mission will be launched before 2010.

 

 

 

 

 

 

11.                                                                                                                              

AGN Variability and the Emerging AGN/BHXRB Paradigm

Phil Uttley

NASA Goddard Space Flight Center
Code 662, Greenbelt, MD 20815

 I will briefly review the results of 9 years of RXTE monitoring which
show the deep similarities between variability of radio-quiet AGN and black
hole X-ray binaries (BHXRBs). Based on these results, I will consider what we
might expect to see with GLAST if blazar jet variability is ultimately driven
by the same process that seems to drive X-ray variations in radio-quiet AGN and
BHXRBs, namely fluctuations in a turbulent accretion flow.

 

12.                                                                                                                             

Blazars at MeV Energies: An Update
W. Collmar (MPE)

The first COMPTEL source catalog (Schoenfelder et al. 2000), covering the first

4-5 years of the 9-year COMPTEL mission, lists 32 steady sources at soft Gamma-ray energies (0.75-30 MeV). We are currently working towards the second and final COMPTEL source catalog by carrying out all-sky point source analyses in different energy bands for different time periods (sum of all data as well as subintervals). Up to now, we found evidence for several new MeV source detections. Some of them we identify as blazars due to their spatial coincidence with EGRET-detected blazars.
These sources will be reported and their combined EGRET-COMPTEL spectra will be shown. Additionally we will report the results of a multifrequency campaign on the blazar 3C 279 centered on an INTEGRAL observation in June 2003.

 

13.                                                                                                                           

Decelerating Flows and the Spectra of TeV Blazars

Demosthenes Kazanas
 NASA/GSFC

We show how consideration of decelerating relativistic flows can
reproduce the TeV blazar spectra without the need to assume Lorentz factors as
large as Gamma = 50.

 

14.                                                                                                                        

High-Energy Observations of Blazars with HESS

Stefan Wagner
LSW Heidelberg
Koenigstuhl, Germany


 HESS is a new-generation facility for ground-based high energy gamma-ray

 studies which became fully operational in January 2004. The talk reports on results of the Blazar observing program with HESS during its first year of operation. This involved a series of multifrequency campaigns covering a wide range of other wavebands. Bright TeV Blazars permit variability studies on intraday time-scales and well-resolved spectral coverage. This enables time-dependent spectral studies of the high-energy emission from Blazars. Implications on Blazar models and pair-absorption will be discussed.

 

15.                                                                                                                             


 Fine Scale Structure of Blazars

Yuri Kovalev
Greenbank/ NRAO


           We have used interferometer fringe visibility data obtained with the VLBA at 15 GHz to examine the compact structure in 250 flat-spectrum extragalactic radio sources. For about 60% of the sources, at least at one epoch, the core component appears unresolved (less than 0.05 mas) preferably along the direction transverse to the jet direction. BL Lacs, on average, appear more compact than quasars. The most variable blazars tend to have the most compact structure. The gamma-ray loud blazars appear to have more compact structure than the gamma-ray quiet ones. This suggests that the mechanism of radio emission of compact components and the mechanism of gamma-ray emission are related. Typical estimates or lower limits to the brightness temperature of the jet cores are in the range of 1011 to 5x1012  K but extend up to 4x1013 K, apparently in excess of the equipartition rightness temperature, or the inverse Compton limit for stationary synchrotron sources. There is some evidence that the largest component speeds are observed only in radio sources with high observed brightness temperatures as would be expected from relativistic beaming. We will also discuss fine scale characteristics of the IDV sources as well as.the variable broad-band radio spectra of blazers

 

16.                                                                                                                      

Jet Kinematics of AGNs at High Radio Frequencies

Svetlana Jorstad
Institute for Astrophysical
Research Boston University

 I will review the results of our bimonthly monitoring of 15 AGNs with the

VLBA at 7mm from March 1998 to April 2001. These include analysis of fast and slow, ballistic and curved motion in the jet flow, computation of physical parameters
for both individual jet features and entire parsec-scale jets, and comparison
of the results across different classes of AGNs.

 

17.                                                                                                                            

Inverse Compton models: richer than we thought?

Markos Georganopoulos
University of Maryland, Baltimore County

We present some case studies of SSC/EC models that reveal some very
interesting behavior, such as superquadratic variations of the Compton component relative to the Synchrotron one. This work is based on a recently developed code that treats the electron Compton losses as a discrete process.

 

18.                                                                                                                             

Intrinsic Curvature in the X-ray Spectra of BL Lac Objects

Eric Perlman

University of Maryland


            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 either curvature or line features in the X-ray spectra. Previous data had suggested absorption features in the X-ray spectra of some BL Lacs; however, none of our spectra show convincing examples of lines, either in absorption or emission. We find significant evidence for intrinsic curvature (typically, steepening by

dg / d(log E) = 0.3 +/- 0.1) in 14 of 17 X-ray spectra. This is difficult to explain via excess absorption, since essentially constant curvature from 0.5-6 keV would require columns significantly greater than evidenced by optical/UV observations of these objects. A more likely interpretation is intrinsic curvature, which we model as resulting from episodic particle acceleration

 

19.

The Capabilities of the GLAST LAT for Blazar Variability Studies

 Julie McInery

NASA/GSFC

   

One of the more notable features of the Large Area Telescope (LAT) on GLAST is its extremely large field of view, which covers more than 20% of the sky at any instant. In survey mode the LAT will be rocked about the orbital plane to provide coverage of the entire gamma-ray sky above 20 MeV every three hours. This will be the default observing mode for the first year of operations and is likely to be the dominant observing mode throughout the rest of the mission. Thus the LAT will provide long, evenly sampled, gamma-ray lightcurves for a large number of sources. In this talk we describe the nature and quality of the data that will be provided by the LAT and use simulated

lightcurves to illustrate some of the scientific questions that can be addressed with LAT observations.

Contributed poster

 

1.                                                                                                                         

Long Term X-ray Monitoring of Markarian 509

Kevin Marshall

Georgia State University

 

We present the results of a long-term X-ray monitoring campaign of the Seyfert 1 galaxy Markarian 509, using the Rossi X-ray Timing Explorer. Mkn 509 has been observed every 3 days for roughly 2 years, and shows significant variability at X-ray wavelengths. A detailed analyis of variability properties is given, including fractional variability, structure function, and the power density spectrum. Comparisons are made between the X-ray variability of Mkn 509, and the variability of other galaxies such as 3C 120 and Akn 120. Conclusions are drawn regarding the nature of variability in these objects, and the relation with black hole mass and accretion rate.

 

2.                                                                                                                    

Confirmation of Apparent Speeds Exceeding 25c in the Jets of Three EGRET Blazars
B. G. Piner, D. Bhattarai (Whittier College), P.G. Edwards (ISAS,/JAXA), D.L. Jones (JPL)


We present multi-epoch Very Long Baseline Array (VLBA) dual-polarization

 observations at 22 and 43 GHz of the three EGRET blazars 0235+164, 0827+243, and 1406-076. These three blazars had been identified as potentially having apparent speeds exceeding ~40c in the snapshot VLBA survey of EGRET blazars by Jorstad et al. (2001). Based on six epochs of full-track VLBA observations of each source during 2002 and 2003, we have measured apparent speeds of 31+/-6 c, 26 +/- 4 c, and 30 +/- 9c$ in the jets of 0235+164, 0827+243, and 1406-076, respectively (for Ho=71 km s-1 Mpc-1, Wm=0.27, and WL=0.73). We therefore confirm the presence of at least ultra-relativistic pattern speeds in these three sources, with the implied lower limit to the bulk Lorentz factor from the observed apparent speeds being G > ~25-30 if the pattern speed equals the bulk flow speed. This material is based upon work supported by the National Science Foundation under Grant No. 0305475 and by a Cottrell College Science Award from Research Corporation.

3.                                                                                                                           

Six Years of 0.85mm Blazar Monitoring at the JCMT

Ian Robson
 UK ATC
 Royal Observatory Edinburgh

            We present data from the JCMT archive of 0.85mm observations of a
sample of over 100 blazars. Some have excellent sampling while others are more
sparse. These data will help assemble multifrequency light curves to
investigate the temporal behaviour of the jet emission.

 

4.                                                                                                                          

Multi-frequency Optical/Near-IR SMARTS Monitoring of Southern Sky
Blazars
John P. McFarland
Departemnt of Physics and Astronomy

Georgia State University

 

The                  The SMARTS (Small and Moderate Aperture Research Telescope System) Consortium's 1.3m telescope was used to monitor 11 blazars at multiple frequencies simultaneously. The 1.3m telescope is equipped with the ANDICAM (A Novel Double-Imaging CAMera) instrument capable of simultaneous observations in the optical and near-IR. Observations were taken at an interval of every 3 days for 2 years. The results of the campaign will be discussed as they relate to constraints on the physical processes in jet propagation models.

 

5.                                                                                                                       

Optical Variability of the Blazar PKS 2155-304

Wes  Ryle
 Dept. of Physics and Astronomy

Georgia State University

            The blazar PKS 2155-304 has been heavily monitored for over two
decades from the optical to gamma rays. The object is highly variable at all
wavelengths and has changed by up ~0.75 magnitudes over long term periods.
This paper discusses an eleven night period during which PKS 2155-304 was
heavily monitored with the 0.9-meter telescope at Cerro Tololo Interamerican
Observatory. During this time period, PKS 2155-304 varied by as much as 0.3
magnitudes in R. The most rapid variation was seen during an 8 hour period with an increase in brightness of ~0.026 mag/hr.

 

6.                                                                                                                             

Analysis of Simultaneous Observations of the BL Lac Object PG 1553+11 in the Radio, Optical, and X-ray Regimes

M. A. Osterman, H. R. Miller (Georgia State U.), H. Aller, M. Aller (U. of

Michigan), R. Fried (Arizona State U.), O. Kurtanidze (Abastumani

Observatory), M. Tornikoski (Helsinki U. of Technology)

 

PG 1553+11 was first identified as a blazar in 1977. It is a BL Lac object with z = 0.36 and its optical magnitude varies from about 13 to 15.5. Subsequent observations revealed that this object is rather weak in the radio for a blazar, exhibiting fluxes of a few tenths of a Jy. It hasn't been studied well in the X-ray regime. We chose PG 1553+11 as the target of a multi-wavelength campaign covering about three weeks during April and May of 2003. The radio observations were obtained at 37 GHz at the Metsahovi Radio observatory in Finland and at 14.5 GHz at the University of Michigan. Optical (R and B band) observations were obtained at the Abastumani Observatory in Georgia and at Braeside Observatory in Arizona. The X-ray observations were performed with RXTE. We present the results from our multi-frequency campaign and attempt to constrain various models for blazars, e.g. shock in jet, synchrotron self-Compton, external

Compton, etc.

 

7.                                                                                                                   

Optical Behaviour of Microvariability in Quasars

Antonio Ramνrez
 Instituto de Astronomia
Unversidad Nacional Autonoma de Mexico 
 

We have performed photometric optical (BVR) observations of a sample
of radio-loud (RLQ) and radio-quiet (RQQ) quasars. In a previous work (de Diego
et al. 1998) we found that flux microvariability is present both in RLQ and RQQ. Now, the aim is to disclose the origin of microvariations through the study of the spectral shape variability. This work is based on the idea that the spectral behaviour could be different whether the origin of these variations is located in the accretion disk or in the relativistic jet. We report preliminary results.

 

8.                                                                                                                

An Investigation of Intermediate-Mass Black Hole Candidates

Alberto Sadun
 Institute/Department: University of Colorado at Denver

            Typically, AGN have in their center a supermassive black hole (of one million to one billion solar masses). We may infer the mass and size of such an AGN from the often highly variable light curve, through the use of light travel time arguments. We are only just now finding that there may be another class of objects, intermediate-mass black hole candidates, which are galaxies purported to harbor a more moderate size black hole in its center. The masses of these black holes are merely eighty thousand to a million solar masses. We have just begun to study this new class of object, mainly because only recently have the appropriate spectroscopy and high energy X-ray observations been made. Indeed, Greene & Ho (2004) have compiled a list of 19 objects, which due to their spectroscopic and X-ray signatures make them good candidates as intermediate-mass black holes. Our project is to confirm the existence of such black holes in many of these objects and others through optical flux variability measurements.

 

9.                                                                                                                

Intraday Polarization Variability of Blazars at 43 GHz

Francesca D'Arcangelo
 Institute for Astrophysical Research
Boston University

I will show VLBA total and polarized intensity images of several blazars that show rapid variability. By splitting the data at a given epoch into two halves and differencing the images, variations in linear polarization on timescales of about 0.25 days is apparent.

10.                                                                                                              

Variability of X-rays from the Jet and Central Engine of 3C 273
 Suwicha Wannawichian
Institute for Astrophysical Research
Boston University

We separate the RXTE light curve of 3C 273 into jet and central-engine components following the analysis of Grandi and Palumbo. This allows us to determine whether there is a relationship between the X-ray variations and other events such as ejections of superluminal radio knots.

 

11.

 

Optical Intraday Variability of BL Lac: Slope-Steepening During

A Brightness Increment?

E. Benitez and A. Ramirez

UNAM, Mexico

 

Broad band BVRI (Johnson-Cousins) observations of BL Lac were done as part of the optical WEBT 2000 monitoring Campaign at San San Pedro M'artir's Observatory (Mexico). Using the 1.5m telescope (3 runs), and later the 1.5m and 2.1m telescopes

for the last run, a sample of 237, 129, and 230 points in B,V,R filters respectively during 11 nights was collected. Intranight and intraday variations during the four runs in B,V,R filters were observed.  Preliminar analysis performed to the July 2001 data will be presented in this poster. During the intraday variations, DB ~ 0.3 mag, DV ~ 0.31 mag, and DR ~ 0.3 mag, that were estimated after subtracting the host galaxy contribution, a clear change in the optical slope is observed. The slope tends to steepen while the object is diminishing its brightness. This behavior is not detected if we consider only B and R filters for the intraday analysis.  We will discuss the results in terms of proposed models for intraday variations in BL Lac objects.

 

12.

KVA Optical Monitoring of PKS 2155-304 in August-September 2005
Stefano Ciprini
 Tuorla Observatory, University of Turku, FINLAND
Vaisalantie Piikkio, Finland

 Preliminary data (optical R-band light curves and polarimetry measurements) on PKS 2155-304 are presented. The data have been obtained during a RXTE-HESS multifrequency campaign with the KVA telescope at La Palma.

 

 

 

 

 

 

13.                                                                                                               

Survey of Potentital Counterparts to EGRET Unidentified Sources
above the Galactic Plane

Steve Bloom


            We will present our most recent findings regarding potential counterparts to EGRET unidentified sources at mid to high Galactic latitudes. These results will include our most recent findings from WIRO and Tenagra.

 

14.                                                                                                                   

Collaborative Microvariability Observations of 0716+714
Joe Pollock,

Dark Sky Observatory, Appalachian State University
and
James Webb, Greg Azarnia,

SARA observatory, Florida International University

 

The microvariability of the highly active object 0716+714 has been the subject of

 a cooperative monitoring program at the Dark Sky Observatory and the SARA facility on Kitt Peak.  Presented are the initial results of more than a dozen full nights of continuous, high time resolution observations conducted to attempt to better characterize these variations.  On one night simultaneous observations at both locations were conducted for over seven hours showing correlated variations at levels down to 0.01 magnitudes, establishing that these are real changes and not due to local observing conditions.

 

15.                                                                                                                 

INTEGRAL Observations of PKS2155-30: Testing

Decelerating-Jet Models

C. Shrader, D. Kazanas (Exploration of the Universe Division,

NASA/GSFC) & M. Georganopolous (Dept. of Physics, UMBC)

 

The TeV blazar PKS 2155-30 was observed with INTEGRAL by our group in

November 2004. We review the capablities of INTERGAL, and its contributions to the

field as well as present the results of those observations  and our analysis.  In particular, a ~100-keV spectral determination can provide the break energy and the emission peak (in n*Fn of the synchrotron spectra. Used in conjunction ground observations, meaningful constraints on the physical parameters  that determine the broad band emission can plausibly be obtained.  By modeling the spectra within the context of

uniform and  decelerating relativistic flows and examining the impact of deceleration one can, in that context, assess the global power requirements. One could also possibly resolve the discrepancy between the excessively large Lorentz  factors generally

required to fit the broad band  spectra of TeV blazars and  the apparent absence of relativistic speeds in VLBI radio observations.

 

 

16.                                                                                                               

The Blazar Optical Monitoring Program at Colgate University's Foggy Bottom

Observatory

Thomas J. Balonek

Colgate University

 

An ongoing study of the optical variability of two dozen blazars has been conducted since 1989 at the Colgate University Foggy Bottom Observatory (FBO) using Photometrics CCDs mounted on the campus 16-inch Ferson Newtonian / Cassegrain telescope.  Although the observatory is located in a region (central New York) with poor climatic conditions, the observatory is used on up to 120 nights per year for research and teaching.  While many programs of blazar variability investigate either the long term variability of a large sample of objects (with less frequent time resolution) or the short term variability of a small sample of objects (with less extensive time coverage), our program investigates a small, but representative, sample of objects with both good time resolution and long term coverage.  Objects are typically observed at R at least once or twice per week, weather permitting, to study the long term variability characteristics.  Some objects are also observed at V and I to study the spectral evolution of outbursts.  In addition to the long term variability coverage, microvariability studies have been undertaken of two blazars (3C 279, BL Lac) during periods of intense activity.  Results from this study have also been combined with observations at other wavebands (from radio to gamma ray) in collaborative programs.

The FBO database consists of nearly 50,000 images on more than 1600 nights over the last sixteen years.  Typically half a dozen two-minute images are taken for each object on each night and added together to improve signal to noise.  They are reduced using IRAF and customized scripts written specifically for Colgate's system.  We have good coverage of 0235+164, OJ 287, 1156+295, 3C 273, 3C 279, 1510-089, 3C 345, BL Lac, CTA 102 and 3C 454.3; less extensive coverage of 3C 66A, 0420-01, 0735+17, 0736+01, 0754+10, 1308+326, 1418+546, 1749+09 and 3C 446; and occasional observations of a half-dozen other blazars.

 

17.

FIU-NSF Correlative Study Progress Report: Microvariability and ShortTterm Variations in Blazars.

Gregory Azarnia, James Webb and Humberto Velazquez

Florida International University and the SARA Observatory

 

We present a general overview and status report of our correlative study which seeks to discover possible correlations between microvariations and short term variations.   Microvariability is defined as the rapid magnitude variations on timescales of minutes to hours and short-term variability that occurs on timescales of weeks to several months.  We employ optical techniques to study a sample of 14 radio-loud quasars and BL Lac objects and make monthly observations throughout the year.

The data are primarily obtained through the SARA 0.9-meter telescope located atop Kitt Peak, Arizona. Observing runs are typically about 6-7 hours long and image sets may run from 100 to 700 images with integration times of a few minutes.  Calibration and reduction of the optical images are conducted through the Image Reduction and Analysis Facility (IRAF) software platform and resultant data plots are generated with IDL.  Investigations into the correlative relationships that may exist between occurances of microvariability and short term light curve variations may allow us to better understand the physical origin of both types of variations.

 

18.

 

Calculation of Blazar Luminosities in New Cosmologies.

Humberto Velasquez and James Webb

Physics Department
Florida International University and the SARA Observatory


            We use updated cosmological models incorporating non-zero cosmological constant to calculate Blazar luminosities. We use several previously published outburst data and compare energetics in the old and new cosmologies.

 

19.

Blazar Observations with VERITAS

Diedre Horan

Smithsonian Astrophysical Observatory

 

Many of the confirmed detections at Very High Energies (VHE; E > 300

GeV) are members of the blazar class of active galactic nuclei. The number of blazar detections should increase dramatically as the next generation of VHE observatories, such as VERITAS, comes on-line. These detectors must be operated on clear, moonless nights leading to a duty cycle of < 10. They use pointed instruments that do not have

all-sky monitoring capabilities and thus require a predetermined target for observation. Therefore, in order to use VERITAS efficiently to study blazars it is important to prepare a list of prime targets and to devise strategies that can be used to trigger target of opportunity observations when a blazar enters an elevated emission state.  Multiwavelength observations of VERITAS blazars will also be an important component of the observing program. In this poster, the current observational status of blazars at very high energies is reviewed briefly and the derivation of the VERITAS observing program

is discussed.

 

20.

The Western Kentucky University Blazar Monitoring Program: The First

Four Years.

Richard Walters, David Barnaby, Michael Carini

Western Kentucky University

 

In 2000, we began a Blazar monitoring program utilizing the 0.6m telescope of the Bell Observatory at Western Kentucky University. We chose a sample of objects from across the ?ro  ?ox plane in order to characterize the variability characteristics of HBLs, IBLs and LBLs. The most rapid timescale variations, known as microvariability provide information on differences in jet characteristics and observations of

microvariability at different colors will provide insights into the nature of the particle acceleration mechanisms in the different subclasses of BL Lacs and during different activity levels. On longer timescales(days to weeks) multiwavelength observations (via our participation in WEBT campaigns, VERITAS campaigns, etc) will be used to

confront models describing the origin of the seed photons responsible for the observed high energy emission in these objects. At the longest timescales(weeks to decades), we will establish the differences in the variability properties between different sub-classes, and make a significant contribution to the body of knowledge concerning the variability of these objects on the longest variability timescales via our ability to provide well sampled light curves. We present here the results of the first fours years of this program, lessons learned, and future plans.

 

21.

Radio-quiet BL Lac objects from the 2dF QSO Redshift

Survey

Londish D., Boyle B.J., Croom S.M., Heidt J.

 

We present further studies of the 2dF BL Lac sample (the 2BL, Londish et al.,2002 MNRAS 334,941), the first optically selected sample of BL Lac objects identified from scrutiny of over 8000 spectra in two redshift surveys, the 2QZ and 6QZ

(Croom et al.,2001, MNRAS, 325, 483; MNRAS, 2004, 349, 1397). BL Lac objects are thought to be the beamed counterparts of FRI/FRII radio galaxies (cf. review by Urry & Padovani 1995, PASP, 107,803); at optical wavelengths these objects are dominated by Doppler boosted, synchrotron radiation, the resultant featureless continuum making them all but impossible to target in optical surveys. To date, therefore, all BL Lac samples have been initially identified in radio and/or X-ray surveys, with obvious bias against radio-quiet objects. In contrast the majority of 2BL objects (38/52) are radio-quiet.

Recent high signal-to-noise VLT spectra of 33 2BL objects has led us to re-classify 12 objects as weak-lined QSOs and a further 6 as white dwarfs/stars. Seven of the 15 remaining continuum objects are undetected at radio and X-ray frequencies. The puzzle remains as to why these radio-quiet QSOs are lineless, or why these beamed continuum objects are radio-quiet - is there a mechanism that produces radio-quiet jets?