Astrophysics Science Colloquium Series
Schedule: January - March 2006

Astrophysics Science Colloquium Series
Schedule: January - March 2006

Through the courtesy of the speakers since 2004, most presentations are available on line.

Future schedules:

  • 2006, Second Quarter
  • Past schedules:

  • 2005, Fourth Quarter
  • 2005, Third Quarter
  • 2005, Second Quarter
  • 2005, First Quarter
  • 2004, Fourth Quarter
  • 2004, Third Quarter
  • 2004, Second Quarter
  • 2004, First Quarter
  • 2003, Fourth Quarter

  • Time: 3:45 pm (Meet the Speaker at 3:30 pm) - Location: Bldg 21, Room 183 - unless otherwise noted.
    To view the abstract of a seminar, click on the title.


    Sunday Monday Tuesday Wednesday Thursday Friday Saturday
    1 2 3 4 5 6 7
    8 9 10 No Colloquium (AAS Meeting) 11 12 13 14
    15 16 17 Pierre Cox (Inst. of Millimeterwave Radio Astronomy) - Dust and Molecular Gas in High-Redshift Galaxies and Quasars 18 19 20 21
    22 23 24 25 26 27 28
    29 30 31


    Sunday Monday Tuesday Wednesday Thursday Friday Saturday
        1 2 3 4
    5 6 7 Robert Gehrz (Univ. Minnesota) - Infrared Astronomy with NASA's New Spitzer Space Telescope 8 9 Ira Thorpe (Univ. Florida) - Bench-top Simulations of LISA Interferometry 10 11
    12 13 14 15 16 17 18
    19 20 21 Derek Hullinger (U.Maryland) Early Afterglow Evolution of X-Ray Flashes Observed by Swift 22 23 24 25
    26 27 28 C. Markwardt / J. Tueller (GSFC) - Swift BAT AGN Survey Results (postponed to Tues. March 14)


    Sunday Monday Tuesday Wednesday Thursday Friday Saturday
        1 2 3 4
    5 6 7 Li Ji (Univ. of Massachusetts, Amherst) - A Non-Equilibrium Ionization Code and its Application 8 9 10 11
    12 13 Michael Stamatikos (U.Wisconsin) - The Search for Neutrinos from GRBs using Antarctic Cherenkov Telescopes 14 C. Markwardt / J. Tueller (GSFC) - Swift BAT AGN Survey Results 15 16 17 18
    19 20 21 Rachel Osten (GSFC) - Signatures of Electron Acceleration from Nearby Stars 22 23 24 25
    26 27 28 Robert Benjamin (Univ. of Wisconsin, Whitewater) - New GLIMPSE Results on the Stellar Structure of the Galaxy**POSTPONED** 29 30 Remo Ruffini (U. Rome La Sapienza) - GRB 050315: A step in the proof of the uniqueness of the overall GRB structure **POSTPONED to April 26** 31

    Connecting Galaxy Evolution, Star Formation and the X-ray Background

    Pierre Cox

    Institute of Millimeterwave Radio Astronomy, Grenoble, France

    Tuesday, January 17, 2006


    The study of the molecular gas in quasars and submillimeter galaxies at high redshift has significantly progressed during the last few years. From the current detection of CO emission in 38 sources spanning a range in redshift from $1
    For information, the current developments and plans for the IRAM telescopes will be presented at the end of this talk.

    Infrared Astronomy with NASA's New Spitzer Space Telescope

    Robert D. Gehrz

    University of Minnesota

    Tuesday, February 7, 2006


    Launched from Kennedy Spaceflight Center in the early morning of August 25, 2003, NASA's Spitzer Space Telescope (formerly Space Infrared Telescope Facility, SIRTF) is the fourth and final facility in the Great Observatories Program, joining Hubble Space Telescope (HST, 1990), the Compton Gamma-Ray Observatory (CGRO, 1991-2000), and the Chandra X-Ray Observatory(CXO, 1999). Spitzer, with a sensitivity that is orders of magnitude higher than that of any previous ground-based and space-based infrared (IR)observatories, is expected to revolutionize our understanding of the creation of the universe, the formation and evolution of primitive galaxies, the genesis of stars and planets, and the chemical evolution of the universe. A brief overview of infrared (IR) astronomy and of Spitzer's role in the NASA's Space IR Astronomy program for the New Millennium will be given. The construction, launch, and in-orbit checkout of the observatory will be reviewed. Science highlights from the first several years of observations will be presented. Special emphasis will be given to the speaker's GTO and GO observations of classical novae, SN 1987a, and the Crab Nebula.

    Further information about the Spitzer can be found on the WEB at

    The speaker's biography and CV may be viewed at

    Bench-top Simulations of LISA Interferometry

    Ira Thorpe

    University of Florida

    Thursday, February 9, 2006

    *** 1:30 PM ***

    *** Bldg 2, Rm 8 ***


    The proposed space-based interferometric gravitational wave detector LISA will be used to study gravitational waves in the mHz regime. It consists of three spacecraft located at the vertices of a 5 Gm triangle, each containing two freely-falling proof masses. The distances between the proof masses will be monitored using laser interferometry in an effort to detect modulations due to gravitational waves. Our group is in the process of developing a bench-top model of LISA interferometry that includes lasers with LISA-like noise characteristics as well as realistic light travel delays achieved using an electronic phase delay method [Class. Quantum Grav. 22 (2005) S227-S234]. The initial goal of this simulator is to test time-delay interferometry (TDI) and arm-locking, two laser frequency noise reduction techniques that have been proposed for LISA. The model could also be expanded to include other aspects of LISA including gravitational-wave signals, thereby providing a source of mock LISA data streams with realistic technical noise. Current progress and results will be presented.

    Early Afterglow Evolution of X-Ray Flashes Observed by Swift

    Derek Hullinger

    University of Maryland

    Tuesday, February 21, 2006

    *** 11:00 AM ***

    *** Bldg 21, Rm 191 ***


    Gamma-ray bursts (GRBs) are bright flashes of gamma-ray energy that originate in distant galaxies and last only a matter of seconds before fading away, never to appear again. They are accompanied by "afterglows" made up of longer wavelength radiation that fades away much more gradually and can be detected for up to several days or even weeks after the gamma-ray burst has vanished. In recent years, another phenomenon has been discovered that resembles gamma-ray bursts in almost every way, except that the radiated energy comes mostly from x-rays instead of gamma rays. This new class of bursts have been dubbed "x-ray flashes" (XRFs). There is strong evidence to suggest that GRBs and XRFs are closely-related phenomena. The Swift mission, launched in November of 2004, is designed to answer many questions about GRBs and their cousins, XRFs-where they come from, what causes them, and why gamma-ray bursts and x-ray flashes differ. Swift's ability to study the very early afterglow emission provides an important key to distinguishing between different theories that seek to explain the differences between XRFs and GRBs. I'll describe a study of XRFs and GRBs detected by Swift, including the first analysis and comparison of the early afterglow properties of these phenomena. This study reveals interesting differences between the temporal properties of GRB and XRF afterglows and sets strong constraints on some theories that seek to explain XRF origins.

    Swift BAT AGN Survey Results

    Craig Markwardt and Jack Tueller

    University of Maryland, NASA/GSFC

    Tuesday, March 14, 2006


    We present results from the the Swift Burst Alert Telescope (BAT) high galactic latitude survey in the 14--200 keV band. The survey reaches a flux of ~10^{-11} erg cm^{-2} s^{-1} and has ~2.7' (90% confidence) positional uncertainties for the faintest sources. This represents the most sensitive survey to date (by a factor of ~10) in this energy band. At 9.5 months, the survey is complete (90% of the sky) to a sensitivity of <2 milliCrab. At these energies, NH > ~10^{24} is required to absorb the BAT flux. We have detected 147 AGN, and after three years of exposure, we expect ~450. Most of the AGN are local (median redshift ~0.025), although there are some high redshift blazars. The Swift XRT telescope is used to identify BAT survey sources that cannot be identified from catalog searches, and to directly measure NH for sources without previousy x-ray spectra. We will present x-ray measurements for some of the AGN identified by Swift. The distributions of NH column densities, luminosities, and the Log N vs. Log S functions will be presented. We will present the distributions of Lopt/LBAT, Lx/LBAT, and the hard x-ray spectral index for the BAT detected AGN. This is a critical test of the completeness of AGN surveys at other wavelengths. These surveys are the basis for understanding the evolution of AGN and the origin of the cosmic x-ray background.

    A Non-Equilibrium Ionization Code and its Application

    Li Ji

    University of Massachusetts, Amherst

    Tuesday, March 7, 2006


    I will introduce a non-equilibrium ionization code which we developed based on updated atomic data . A version of the code has been optimized so that the calculation can be done efficiently and accurately enough for comparison with X-ray CCD spectra and the coloumn densities of UV interstellar/intergalactic medium. The atomic process of recombination into highly excited levels has been self-consistently included, which is important in some non-equilibrium cases but has generally been ignored in the past. I will show example applications to illustrate the characteristics of the code and its combination with various models of gas dynamics. In particular, I will mainly present results from applications to massive stellar cluster winds. And I will briefly present other applications to galactic winds and the UV absorption/emission study with the radiative cooling scenario.

    A New Search Paradigm for Correlated Neutrino Emission from Discrete GRBs using Antarctic Cherenkov Telescopes in the Swift Era

    Michael Stamatikos

    University of Wisconsin

    Monday, March 13, 2006

    *** 1:30 PM ***

    *** Bldg 2, Rm 8 ***


    Intrinsic neutrino properties qualify them as unique cosmic messengers. Canonical fireball phenomenology, in the context of hadronic acceleration, predicts correlated MeV to EeV neutrinos from gamma-ray bursts (GRBs). The Antarctic Muon and Neutrino Detector Array (AMANDA), has demonstrated the viability of high energy neutrino astronomy by using the ice at the geographic South Pole as a Cherenkov medium. Ideal for detection are TeV-PeV neutrinos, which are expected to be in coincidence with prompt gamma-ray emission, resulting in a nearly background-free search that may possibly reveal an acceleration mechanism for the highest energy cosmic rays. We describe the theoretical modeling and analysis associated with a search for correlated neutrino emission from a subset of GRBs detected by the Burst and Transient Source Experiment (BATSE) and High Energy Transient Explorer-II (HETE-II) burst GRB030329, based upon each burst's individual (discrete) set of observed electromagnetic parameters, in the context of constraints on astrophysical models. The effects of anisotropic emission geometry and non-trivial neutrino mass are addressed. Implications for future correlated neutrino searches in the era of Swift and IceCube, AMANDA's km-scale successor, will be discussed.

    Signatures of Electron Acceleration from Nearby Stars

    Rachel Osten


    Tuesday, March 21, 2006


    Electron acceleration plays in important role in the energetics of solar and (by implication) stellar flares. Observational signatures of accelerated electrons appear directly at radio and hard X-ray wavelengths, and indirectly at optical wavelengths; most stellar work has concentrated on radio and optical wavelengths due to sensitivity issues. Finding correspondences in the behavior of accelerated electrons during solar and stellar flares is important to understanding the physical processes at work in a variety of stellar environments. New instruments have expanded the capacity for studying electron acceleration in stars through both sensivitiy and serendipity. I will review recent results concerning observational signatures of electron acceleration in solar neighborhood cool stars at radio and hard X-ray wavelengths, and discuss the implications for the physics of stellar coronae.

    New GLIMPSE results on the Stellar Structure of the Galaxy

    Robert A. Benjamin

    University of Wisconsin-Whitewater



    I present Spitzer/GLIMPSE (Galactic Legacy Infrared Midplane Survey Extraordinaire) results on the global variation of the mid-infrared stellar and diffuse emission over 220 square degrees of the inner Galactic plane from 0<|l|<65 degrees and |b|< 1 degree using IRAC. Principal results include the following: (1) variation of source counts indicate the Galaxy has a radial scale length of H_*= 3.9 +/- 0.6 kpc; (2) there is strong evidence for a Galactic bar with half-length R_bar=4.4 +/- 0.5 kpc, oriented at phi=44 +/- 10 degrees; (3) a major spiral arm of the Galaxy appears to be missing, (4) source counts are depressed even at 4.5 microns by extinction associated with molecular gas; (5) diffuse emission in all four bands is dominated by star formation regions; and (6) there is a significant range in diffuse band ratios: [4.5]/[3.6] varies by a factor of ~10 along the Galactic plane, while [8.0]/[5.8] (the most tightly correlated bands) only varies by a factor of ~2.

    GRB 050315: A step in the proof of the uniqueness of the overall GRB structure

    Remo Ruffini

    Universit'a di Roma "La Sapienza"

    POSTPONED TO April 26

    *** 1:30 PM ***

    *** Bldg 2, Rm 8 ***


    Using the Swift data of GRB 050315, we progress in proving the uniqueness of our theoretically predicted Gamma-Ray Burst (GRB) structure as composed by a proper-GRB, emitted at the transparency of an electron-positron plasma with suitable baryon loading, and an afterglow comprising the "prompt radiation" as due to external shocks. Detailed light curves for selected energy bands are theoretically fitted in the entire temporal region of the Swift observations ranging over 10^6 seconds. The theoretically predicted instantaneous spectral distribution is presented, confirming a clear hard-to-soft behavior.

    Jerry Bonnell

    NASA Logo, National Aeronautics and Space Administration