Astrophysics Science Colloquium Series
Schedule: January - March, 2005

Astrophysics Science Colloquium Series
Schedule: January - March, 2005

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

Future schedules:

  • Second quarter of 2005
  • Past schedules:

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

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


    Sunday Monday Tuesday Wednesday Thursday Friday Saturday
    2 3 4 5 6 7 8
    9 10 11 - AAS Meeting, No Seminar 12 13 14 15
    16 17 18 - Gamil Cassam-Chenai, Thermal and Nonthermal X-ray Emission in Supernova Remnants 19 20 21 22
    23 24 25 - Michael Watson, Fisk University, Development of a General Relativistic Particle-in-Cell (GRPIC) Code 26 27 - Dr. Reba Bandyopadhyay, Oxford University, Exploring the Nature of Weak Chandra Sources near the Galactic Centre 28 29
    30 31      


    Sunday Monday Tuesday Wednesday Thursday Friday Saturday
       1 2 3 4 5
    6 7 8 - ASD Colloquium: Party and Poster Session 9 10 11 12
    13 14 15 Colin Norman (JHU) The Hubble Origins Probe 16 - Norman Grogin, Johns Hopkins Univ. Highlights of AGN Science from GOODS: 1:15pm, Bldg2, Rm8 17 - Mario Gliozzi, George Mason Univ. An X-ray view of radio-loud Active Galactic Nuclei: 2pm Bldg 2, Rm8 18 - Andreas Eckart, Univ. of Cologne, Variable Emission from Sgr A*: 2:15pm, Bldg 21, Rm8 19
    20 21 22 - Robert Rutledge, McGill Measuring Radii of Neutron Stars 23 24 25 26
    27 28 - Ravi Sankrit, Johns Hopkins Univ. Supernova Remnant Shocks in the Far-Ultraviolet: 2pm Bldg2, Rm8      


    Sunday Monday Tuesday Wednesday Thursday Friday Saturday
       1 - Charles Dermer (NRL), TeV Emission from the Galactic Center Black Hole Plerion 2 3 4 5
    6 7 8 - John Mather (NASA), JWST and the Future of Space Astronomy 9 10 11 12
    13 14 15 - Wim de Boer (Univ. Karlsruhe), Indirect Evidence for Dark Matter Annihilation from the EGRET Excess of Diffuse Galactic Gamma Rays 16 17 - Katherine Blundell (Oxford Univ.), Jet Physics from SS433 18 19
    20 21 22 -
    Colloquium: John Clem (Bartol Inst.), Charge-Sign Dependence in Solar Modulation
    Seminar: Tomaso Belloni (INAF-OAB) Black-Hole Transients
    23 24 25 26
    27 28 29 - No Colloquium 30 31 Kirsty Grosart (Univ. Southampton), Oscillations and Stability of Superfluids   

    Thermal and Nonthermal X-ray Emission in Supernova Remnants

    Dr. Gamil Cassam-Chenai

    Tuesday, 18 January 2005


    In supernova remnants (SNRs), the matter heated to millions of degrees produces X-ray thermal emission. This emission contains information on the chemical composition of the ejected matter and on the ambient medium, as well as on the hydrodynamical evolution of the SNR. Besides, the SNR shocks are believed to accelerate particles to very high energy (at least to the knee of the cosmic-ray spectrum). X-ray synchrotron radiation from accelerated electrons is then expected. We have investigated the X-ray thermal and nonthermal components in SNRs by an observational and a modelling approaches The observational part will deal with two SNRs - Kepler and G347.3-0.5 - observed by the European satellite XMM-Newton. The modelling part will emphasize on synchrotron emission obtained from a hydrodynamical model coupled with a nonlinear particle acceleration model which takes into account energy losses of the accelerated electrons.

    Development of a General Relativistic Particle-in-Cell (GRPIC) Code

    Dr. Michael Watson

    Fisk University

    Tuesday, 25 January 2005


    The jets observed to emanate from many compact objects arise from the twisting of a magnetic field threading a rotating accretion disk. Angular momentum and energy is magnetically extracted from the particle disk. Currently, magnetohydrodynamic (MHD) code is used to simulate the disk-jet connection. This presentation will describe a new general relativistic, fully-electromagnetic, particle-in-cell (GRPIC) simulation of astrophysical objects. We compare the results of the code with the standard TRISTAN code. It is expected that the use of a particle code will provide further insight into the non-force free regimes of accretion disks.

    Exploring the Nature of Weak Chandra Sources near the Galactic Centre

    Dr. Reba Bandyopadhyay

    Oxford University

    Note Special Date: Thursday, 27 January 2005
    Special Time: 1:30 pm


    We present results from the first near-IR imaging of the weak X-ray sources discovered the Chandra/ACIS-I survey (Wang et al. 2002) towards the Galactic Centre (GC). These ~800 discrete sources, which contribute significantly to the GC X-ray emission, represent an important and previously unknown population within the Galaxy. From our VLT observations we will identify likely IR counterparts to a sample of the hardest sources, which are most likely X-ray binaries. With these data we can place constraints on the nature of the discrete weak X-ray source population of the GC.

    ASD Poster Presentations

    Tuesday, 8 February 2005

    3:30 - 4:30pm; Bldg 21, Rm 183

    Presenter: Title

    Yuxuan Yang: Spatial 2-Point Correlation Function of X-ray selected AGNs
    Ted Gull: ... on Eta Carinae
    Krister Nielsen: The Presence of UV Absorption ... on Eta Carinae
    Steve Ritz: GLAST mission
    Joe Dolan: Upper Limits on Dying Pulse Train Events from Cygnus XR-1
    Darian Boggs: Numerical Relativity Group software demo 1
    Darian Boggs: Numerical Relativity Group software demo 2
    Neil Gehrels: Swift mission
    Dominic Benford: New Approaches for SAFIR
    Bill Danchi: Fourier-Kelvin Stellar Interferometer
    Stephen Rinehart: Wide-field Imaging Interferometry Testbed
    Jean Cottam: The Astro-E2 mission
    Dirk Petry: Earth Gamma-Ray Albedo
    Johannes Staguhn: Near-Infrared Photometry of the High-Redshift Quasar RDJ030117+002025: Evidence for a Massive Starburst at z=5.5
    Harvey Moseley: Microshutter Arrays for JWST NIRSpec
    Alexander Kutyrev: First Results on the Diffuse Ionized Hydrogen Emission from the Galactic Plane with Cryogenic Solid Fabry-Perot Spectrometer
    Julie McEnery: The GLAST Large Area Telescope
    Jay Norris: Long-Lag, Wide-Pulse, Gamma-Ray Bursts
    David Band: Supporting the GLAST User Community
    Ann Hornschemeier: The X-Ray Luminosity Function of Normal Galaxies in the GOODS
    Dave Leisawitz: Space Infrared Imaging Telescope
    Dominic Benford: Rapid-Turnaround Cryogenic Detector Characterization System
    Randy Smith: Interstellar Dust and Gas with Chandra and XMM

    The Hubble Origins Probe (HOP)

    Dr. Colin Norman

    Johns Hopkins University

    Tuesday, 15 February 2005


    The Hubble Origins Probe (HOP) concept is to replicate the design of the Hubble Space Telescope with a much lighter, unaberrated mirror and associated lightweight optical telescope, and a modern spacecraft enabling a rapid path to launch, significant cost savings and risk mitigation. Launch would be on an Atlas 521 rocket or Delta IV(H). In addition to hosting the powerful new instruments COS and WFC3, a Very Wide Field Imager (VWFI) will be built in collaboration with our Japanese international partners. The cost of VWFI will be borne by Japan. The scientific enhancement of the mission comes from the fact that the field of view of the VWFI is 17 times that of the Advanced Camera currently flying on Hubble and the VWFI is 3-4 times more sensitive at critical wavelengths. The conservative estimate of the cost of the HOP project is approximately $1 Billion. We have developed a detailed schedule for HOP and reasonably estimate that, from the time of the authority to proceed, it will take 65 months to a successful launch. We envisage that HOP is an important fallback option (the third way) if manned or robotic servicing of HST cannot be undertaken.

    Highlights of AGN Science from GOODS

    Dr. Norman Grogin

    Johns Hopkins University

    Note Special Date: Wednesday, 16 February 2005
    Special Time: 1:15 pm
    Location: Bldg 2, Rm 8


    The multi-wavelength observations of the Great Observatories Origins Deep Survey (GOODS), having targeted the Chandra Deep Fields with deep HST imaging and the deepest available Spitzer imaging at 3.6 to 24um, are uniquely suited to probing the nature of moderate luminosity AGN at cosmological distances. In this talk, I will highlight what we are learning from the several hundred GOODS AGN in recent and ongoing studies of; host galaxies and their local environments; X-ray and optical variability; the newfound exotic population of "EXOs"; and SEDs and multi-wavelength number counts as compared with predictions from the AGN unification paradigm.

    An X-ray view of radio-loud Active Galactic Nuclei

    Dr. Mario Gliozzi

    George Mason University

    Note Special Date: Thursday, 17 February 2005
    Special Time: 2:00 pm
    Location: Bldg 2, Rm 8


    One of the outstanding open questions of the extragalactic astronomy is the dichotomy between radio-loud and radio-quiet AGN, which previous studies have suggested to originate in the central engine. The X-rays, with their higher penetrating power, represent the ideal tool to shed light on this issue. First, using archival and proprietary XMM-Newton and Chandra data, we investigate the origin of the X-rays and the nature of accretion in low-power FRI radio galaxies, by studying their spatial and spectral properties. Secondly, making use of XMM-Newton archival data, we present the spectral results of FRII galaxies with different optical classification. Finally, we study the long-term properties of broad-line radio galaxies and jet-dominated sources monitored with RXTE, showing that the spectral variability provides useful information to constrain the origin of X-rays, and that a thorough temporal analysis can possibly strengthen the link between AGN and Galactic BHs.

    Variable Emission from Sgr A*

    Dr. Andreas Eckart

    Univ. of Cologne

    Note Special Date: Friday, 18 February 2005
    Special Time: 2:15 pm

    Location: Building 21, Room 183


    It is reported on recent simultaneous near-infrared/X-ray observations of the SgrA* counterpart which is associated with the massive 3 to 4 million solar mass black hole at the center of the Milky Way. Special emphasis is put on a flare that was detected in the X-domain with an excess 2 - 8 keV luminosity of about 6x10^33erg/s. A fading flare of SgrA* with >2 times the interim-quiescent flux was also detected at the beginning of the NIR observations, that overlapped with the fading part of the X-ray flare. Compared to 8-9 hours before the NIR/X-ray flare a marginally significant increase in the millimeter flux density (measured with BIMA) of Sgr A* was detected during measurements about 7-9 hours afterwards. It is found that the flaring state can be conveniently explained with a synchrotron self-Compton model involving up-scattered sub-millimeter photons from a compact source component, possibly with modest bulk relativistic motion. In addition the properties of the stellar cluster including the cusp around the black hole are summarized. Special emphasis will be put on the distribution and dynamics of different stellar populations as well as a most recent detection of IRS3 with the VLT interferometer using MIDI at 8-12microns.

    Measuring Radii of Neutron Stars

    Dr. Robert Rutledge


    Tuesday, 22 February 2005


    The primary obstacle for understanding the nuclear density equation of state is observing matter at nuclear densities, but with zero temperature. One place where this occurs naturally is in neutron stars. While the masses of neutron stars have been measured with great precision for 3 decades through radio pulsar doppler-shift measurements, we have only just begun to directly measure the radii of neutron stars. Neutron star radii are now being measured using broad-band x-ray spectroscopy in the 0.3-10 keV energy range with XMM and Chandra, with a few outstanding examples with uncertainties of < 10 per cent. I will review the observational scenario for these sources; present the status of neutron star radius measurements today; cover the contributing uncertainties to the neutron star radius measurements; mention the possibility of simultaneous mass-radius measurements; and expound upon prospects for future measurements of neutron star radii.

    Supernova Remnant Shocks in the Far-Ultraviolet

    Dr. Ravi Sankrit

    Johns Hopkins University

    Monday, 28 February 2005

    Building 2, Room 8 at 2pm


    The far-ultraviolet flux of a typical supernova remnant (SNR) is dominated by shock interactions between the blast wave and surrounding clouds. A significant fraction of the energy generated in the supernova explosion is radiated away in these interactions. Therefore far-ultraviolet observations of SNRs are important for understanding the processes by which supernovae energize and chemically enrich the interstellar medium. Multi-wavelength studies of SNRs that include far-ultraviolet and X-ray observations are required to reveal the relationship between the hot regions within remnants and the cooler ambient gas around them.

    We have used the Far Ultraviolet Spectroscopic Explorer (FUSE) to observe several Galactic and Magellanic Cloud SNRs. Because of the high spectral resolution, sensitivity and wavelength coverage of FUSE, the spectra allow a great advance in our knowledge of SNR shocks. I will review the results of the FUSE SNR program, present specific examples of shocks observed in the Cygnus Loop and Vela SNRs, outline the potential diagnostic power of the spectral line fluxes and velocity profiles, and discuss ongoing multi-wavelength studies and the need for a new theoretical framework to interpret the wealth of data we have obtained in recent years.

    TeV Emission from the Plerion Formed by the
    Supermassive Black Hole at the Galactic Center

    Dr. Charles Dermer

    US Naval Research Laboratory

    Tuesday, 1 March 2005


    The High Energy Stereoscopic System collaboration recently reported highly significant detection of TeV gamma-rays coincident with Sgr A*. After briefly reviewing this and other Galactic center (GC) observations, we suggest the following scenario: In the extreme advection-dominated accretion flow (ADAF) regime of the GC black hole (GCBH), synchrotron radio/submillimeter emission of ~100 MeV electrons emanates from a magnetized corona within ~ 20 Schwarzschild radii of the GCBH. Close to the innermost stable orbit of the ADAF, instabilities and shocks within the flow inject electrons through first-order Fermi acceleration to make synchrotron X-ray flares observed with Chandra, XMM, and INTEGRAL. A subrelativistic MHD wind powered by the ADAF forms a termination shock (as in pulsar-powered plerions) at ~0.01 pc from the GCBH that accelerates electrons which Compton-scatter the ADAF and far-infrared dust radiation to TeV energies. The synchrotron radiation of these electrons forms the quiescent X-ray source resolved by Chandra. GLAST should be able to map the gamma-ray plerion. The concept of a plerion formed by an ADAF wind could explain unidentified gamma-ray sources. Isolated, accreting black holes could be detected by their plerionic radiation halos.

    The James Webb Space Telescope and the
    Future of Space Astronomy

    Dr. John Mather


    Tuesday, 8 March 2005


    The James Webb Space Telescope (JWST) is the first in a possible series of deployable infrared to millimeter wave space telescopes. The design process for JWST has already produced ultra-light mirrors, deployment methods, and cooling approaches that could lead to much larger and more capable equipment in the future. We will describe the progress on JWST in the context of its history and illustrate some new concepts for future missions that spring from it. These include the SAFIR (Single Aperture Far Infrared) telescope and the SPECS (Submillimeter Probe of the Evolution of Cosmic Structure). The JWST will operate at the Sun-Earth Lagrange point L2, where radiative cooling lowers the telescope and instrument temperatures to about 35 K. It will have an 18-segment beryllium primary mirror with a 25 m2 area fitting inside a 6.6 m circumscribed circle, and will provide spectroscopy and imaging over the wavelength range from 0.6 to 28 ┬Ám. It is planned for launch in 2011 on an Ariane 5 rocket. The project is a partnership of NASA, ESA, and CSA, and the prime contractor is Northrop Grumman. See for more details on JWST.

    Missions to follow JWST will be able to draw on a greatly expanded technological base. Other uses ranging from Earth sciences to surveillance demand large space telescopes and interferometric systems, and the infrastructure for remote assembly and astronaut servicing will continue to improve as the Space Station is completed and experience is gained.

    The SAFIR (, and ) and SPECS ( ) missions have been approved by NASA for Vision Mission studies, now in progress. SAFIR was mentioned prominently in the 2000 NRC Decadal Report on Astronomy as "the recommended next step in exploring the cosmos at far-infrared wavelengths." The report furthermore states that SAFIR could "form the basis for developing a far-infrared interferometer in the succeeding decade." I will summarize both of these concepts and the unique science capabilities enabled by these missions as well as outline how they might further develop as other projects come on line, scientific priorities evolve, and technological capabilities expand.

    Indirect Evidence for Dark Matter Annihilation from the
    EGRET Excess of Diffuse Galactic Gamma Rays

    Dr. Wim de Boer

    University of Karlsruhe

    Tuesday, 15 March 2005


    The excess of diffuse galactic gamma rays in the range between 1 and 100 GeV, as observed by the EGRET telescope on the NASA Compton Gamma Ray Observatory, shows all the key features from Dark Matter (DM) annihilation:
    1) the energy spectrum of the excess is the same in all sky directions and is consistent with the gammas from the fragmentation of monoenergetic quarks, as expected from DM annihilation; From the excess the DM particle mass is estimated between 50-100 GeV;
    2) the intensity distribution of the excess in the sky is used to determine the halo profile, which, outside the plane of the galaxy, is found to correspond to an isothermal (cored) profile falling as 1/r2;
    3) in the plane of the galaxy the excess shows a strong substructure: two doughnut-shaped rings at radii of 4 and 14 kpc, which are correlated with the ring of molecular hydrogen at 4 kpc and the ring of stars at 14 kpc, thought to originate from the infall of a dwarf galaxy;
    4) the mass in these rings is estimated from the intensity of the excess of gamma rays and is used to explain the hitherto mysterious change of slope of the outer rotation curve of our galaxy;
    5) all features and cross sections are consistent with DM being the supersymmetric partner of the Cosmic Microwave Background. Prospects for direct DM detection and finding the predicted supersymmetric particles at colliders will be discussed.

    Jet physics from SS433

    Dr. Katherine Blundell

    Oxford University

    Thursday, 17 March 2005

    Bldg 2, Rm 8 at 1:00pm


    Jets in microquasars evolve much more rapidly than do the jets of extragalactic quasars and so offer much potential for learning about jet physics. I will present new results on two relativistic radio jet sources in the Galaxy, SS433 and Cygnus X-3, and show how after properly accounting for the effects of light-travel time they reveal important behaviour in their jet evolution. I will also present a powerful new diagnostic of jet speeds recently discovered for SS433.

    Black-hole Transients: From QPOs To Relativistic Jets

    Dr. Tomaso Belloni

    INAF-OAB, Merate, Italy

    Tuesday, 22 March 2005

    Bldg 2, Rm 8 @ 11:00am


    Due to the impressive amount of new data provided by the RXTE satellite in the past decade, our knowledge of the phenomenology of accretion onto black holes has increased considerably. In particular, it has been possible to classify the outburst evolution of transient systems on the basis of their spectral and timing properties, and link them to the ejection of relativistic jets as observed in the radio. I will present this scheme, concentrating on the properties of the quasi-periodic oscillations observed in the light curves and on the link with jet ejection.

    Observations of the Charge-Sign Dependence in Solar Modulation

    Dr. John Clem

    Bartol Institute

    Tuesday, 22 March 2005


    Anti-correlation between cosmic ray fluxes and the level of solar activity (solar modulation) is caused by magnetic field fluctuations carried by the solar wind that scatter and/or decelerate Galactic cosmic rays. Cosmic ray electrons and nuclei respond differently to solar modulation, with the differences being clearly related to reversals of the solar magnetic field which occur every eleven years. If the heliospheric magnetic field has certain types of large scale order, the charge sign of cosmic ray particles can affect their propagation. Since electrons and nuclei have greatly different charge/mass ratios, the relation of velocity and magnetic rigidity (momentum/charge) is very different for these two particle species. Consequently a fully quantitative determination of the charge sign dependent component of solar modulation has yet to be made. Careful study of the behavior of the small flux of cosmic ray positrons relative to negative electrons (which have an identical relationship between velocity and rigidity) will allow a definitive separation of charge sign effects from those arising from velocity differences.

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