Astrophysics Science Colloquium Series
Schedule: January - March, 2005
Astrophysics Science Colloquium Series
Schedule: January - March, 2005
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.
January |
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| Sunday | Monday | Tuesday | Wednesday
| Thursday | Friday | Saturday |
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| | | | | | | 1 |
| 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 | | | | | |
February |
|---|
| 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 |
| | | | |
March |
|---|
| 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
Abstract
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
Abstract
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.
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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
Abstract
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.
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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
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The Hubble Origins Probe (HOP)
Dr. Colin Norman
Johns Hopkins University
Tuesday, 15 February 2005
Abstract
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.
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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
Abstract
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.
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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
Abstract
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.
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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
Abstract
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.
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Measuring Radii of Neutron Stars
Dr. Robert Rutledge
McGill
Tuesday, 22 February 2005
Abstract
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.
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Supernova Remnant Shocks in the Far-Ultraviolet
Dr. Ravi Sankrit
Johns Hopkins University
Monday, 28 February 2005
Building 2, Room 8 at 2pm
Abstract
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
Abstract
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.
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The James Webb Space Telescope and the
Future of Space Astronomy
Dr. John Mather
NASA/GSFC
Tuesday, 8 March 2005
Abstract
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 µm. 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
http://www.jwst.nasa.gov
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 (
http://safir.jpl.nasa.gov/,
and
http://safir.gsfc.nasa.gov/
) and SPECS ( http://space.gsfc.nasa.gov/astro/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
Abstract
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
Abstract
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
Abstract
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
Abstract
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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