List of Abstracts
(Alphabetical by Author / Presentor)
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B
| Bailyn, Charles |
"Optical/IR Monitoring of Transient X-ray Binaries" (Invited)
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I will review the expectations for optical/IR lightcurves from
the outbursts of soft X-ray transients that arise from theory
and previous observations. I then compare these expectations
with recent data from the YALO project, which has provided
daily OIR observations for a number of sources in outburst.
I conclude that a) whenever data are available, the OIR outburst
precedes the start of the X-ray outburst by about a week - OIR
monitoring thus provides an excellent trigger for X-ray outbursts;
2) there are a wide variety of OIR outburst morphologies, many of
which have no correlation with the X-ray flux - thus it appears
that effects beyond simple disk instabilities and X-ray irradiation
must be invoked to explain the OIR flux; c) a new kind of outburst,
dominated by IR flux, with no apparent X-ray response in the RXTE/ASM,
has been observed in two sources - in both cases these IR-dominated
events have significant radio flux, and thus may be related to jet
activity. If so, the IR could be used as a trigger for radio
observations. Finally, I will present our plans for more such
monitoring over the next few years.
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Optical/IR Monitoring of Transient X-ray Binaries |
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Butt, Yousaf, Maccarone, Thomas, and Prantzos, Nikos
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"Jet-Induced Nucleosynthesis in Misaligned Microquasars"
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The jet axes and the orbital planes of microquasar systems are usually assumed to be approximately perpendicular, eventhough this is not
currently an observational requirement. On the contrary, in one of the
few systems where the relative orientations are well-constrained,
V4641Sgr, the jet axis is known to lie not more than ~35 degrees from
the binary plane. Such a jet, lying close to the binary plane, and
traveling at a significant fraction of the speed of light may
periodically impact the secondary star initiating nuclear reactions on
its surface. The integrated yield of such nuclear reactions over the
age of the binary system (less the radiative mass loss) will
detectably alter the elemental abundances of the companion star. This
scenario may explain the anomalously high Li enhancements (roughly
~20-200 times the sun's photospheric value; or, equivalently, 0.1-1
times the average solar system value) seen in the companions of some
black-hole X-ray binary systems. Gamma-ray line signatures of the
proposed process could include the 2.22 MeV neutron capture line as
well as the 0.478 MeV 7Li* de-excitation line, both of which may be
discernable with the INTEGRAL satellite if produced in an optically
thin region during a large outburst. For very energetic jets, a
relatively narrow neutral pion gamma-decay signature at 67.5 MeV could
also be measurable with the GLAST satellite. We argue that about
10-20% of all microquasar systems ought to be sufficiently misaligned
as to be undergoing the proposed jet-secondary impacts.
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Jet-Induced Nucleosynthesis in Misaligned Microquasars |
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Buxton, Michelle
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"Why Spectroscopy is Important : Case of GX 339-4"
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Line profiles of emission lines provides a wealth of information about a
binary system such as the velocity and location of emitting line regions
and the structure of the accretion disk. Hence, it is a valuable
piece of the puzzle in understanding X-ray binaries.
I will present data obtained on GX 339-4 during the high
and low states in 1998 and 1999, respectively. The line profile
behaviour is rich and varied and raises many questions about the
sources of the optical emission lines and how the X-rays may be
affecting such emission.
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Charles, Phil
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"X-ray Binaries in the 21st Century" (Invited Introductory Talk)
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As the field of X-ray binaries celebrates its 40th anniversary, we
have the most powerful suite of space and ground-based telescopes
available for their study. Many of the major advances in our
understanding of X-ray binaries have come, not only from
multi-wavelength observing, but also from our ability to respond to
unpredictable phenomena with target-of-opportunity observing on very
short timescales. I will briefly summarise some of the key such
events in the history of X-ray binaries, as well as giving examples
from very recent campaigns which have yielded new insights.
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X-ray Bianries in the 21st Centrury |
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Cottam, Jean
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"Gravitationally redshifted absorption lines in the x-ray burst spectrum of the neutron star in EXO 0748-676"
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D, E, F, G
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Di Stefano, Rosanne, and Kong, Albert
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"Luminous Supersoft X-Ray Sources in External Galaxies"
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A total of more than 200 luminous supersoft X-ray sources (SSSs) have
been discovered in the spiral galaxies M31, M101, M83, M51 NGC 300 and
in the elliptical galaxies M87, NGC 4472, and NGC 4697. We have used
a set of uniform criteria to select the sources, making comparisons
among the galaxies possible. We will discuss our selection algorithm,
which will be made public for the analysis of Chandra and XMM data, as
well as the preliminary results we found by applying the algorithm to
data from the galaxies mentioned above. We find several interesting
trends, including indications of a large underlying SSS population in
each galaxy, the existence of SSSs among young stellar populations in
spirals, and a set of ultraluminous SSSs. We anticipate that the study
of SSSs in external galaxies by both Chandra and XMM will play a key
role in illuminating the physical natures of the sources.
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Ken Ebisawa (ISDC, NASA/GSFC), Piotr Zycki (Copernicus center),
A. Kubota (ISAS), T. Mizuno (Hiroshima Univ.) and K. Watarai
(Kyoto University)
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"Accretion Disk Spectra of Ultra-luminous X-ray Sources and Galactic Superluminal Jet Sources"
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The Ultra-luminous X-ray Sources (ULXs) in nearby spiral galaxies and Galactic
superluminal jet sources share a similar spectral property that they have
unusually high disk temperatures which cannot be explained in the framework of
the standard accretion disk model in the Schwarzschild metric. We have
calculated an extreme Kerr disk model to fit the observed spectra of ULXs and
superluminal jet sources, in order to examine the claim that the Kerr disk may
explain the observed high disk temperature, as the inner radius can be smaller
and the disk will be hotter than in the Schwarzschild case. We have found that
the observed Kerr disk spectra become significantly harder compared to the
Schwarzschild disk due to the Doppler boosts in the very vicinity of the black
hole, only when the disk is highly inclined. Consequently, the Kerr disk
model may be appropriate for superluminal jet sources, which are known to be
highly inclined systems. For ULXs, on the other hand, the Kerr disk
interpretation is problematic, as it is highly unlikely that their accretion
disks are preferentially inclined. Instead, the slim disk (advection dominated
optically thick disk) model is likely to explain the observed super-Eddington
luminosities and hard spectra of ULXs.
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Accretion Disk Spectra of Ultra-luminous X-ray Sources and Galactic Superluminal Jet Sources |
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Finger, Mark, Ghosh, K., Scott, D. M., Swartz, D., Wilson, C. A.,
and Wilson, R. B.
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"Chandra HETG Observations of the Transient Pulsar 2S 1845-024"
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2S 1845-024 is a transient Be/X-ray pulsar in a highly eccentric
orbit, that has outburst every periastron passage for at least the
last decade. Previous X-ray observations have shown that the outburst
light-curves have an unusual structure. They begin prior to periastron
passage with a short spike, which lasts 1-2 days. The flux on the tail
of the spike reaches a minimum near periastron passage, and then
rapidly rises into a more prolonged outburst, lasting 30-40 days. The
initial spike has been interpreted as direct wind accretion of
material from the Be star's equatorial disk during the pulsar's
passage through it. The following outburst has been interpreted as due
to accretion from a disk around the pulsar formed from higher angular
momentum material stripped from the Be star disk.
We have obtained four Chandra observations of this source near the
outburst that occurred this September. The first, prior to the
outburst, was made without gratings. This was followed by HETG
observations during the initial spike, in the dip between the spike
and main outburst, and during the main outburst. We present spectral
analyses of these observations.
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M.R. Garcia, J.E. McClintock, J.M. Miller
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"Do Large Scale Jets Arise Only in Long Period Black Hole X-ray Novae?"
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In this brief note we remark that the four spatially resolved relativistic
radio jets among the 14 dynamically confirmed black hole x-ray novae
are all in systems with long orbital periods.
Many shorter period systems show transient
radio outbursts which are attributed to jets, but
these jets have not been resolved. Super-Eddington
accretion has been suggested as required for jet formation, but the
apparent outburst luminosities of these 4~systems are not all super-Eddington
(and some Eddington outbursts did not form jets). We
speculate that some as yet unknown process favors formation of
substantially larger jets in these systems.
Two short period systems show evidence for extent, but
have not been resolved into multiple components as the long period
systems have.
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Gilfanov, Marat
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"HMXB, ULX and star formation"
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Based on Chandra and ASCA observations of the Milky Way, Magellanic
Clouds and nearby starburst galaxies we study population of high mass
X-ray binaries (HMXB), their connection with ultra-luminous X-ray
sources (ULX) and relation to the star formation.
We show that the number and/or the collective X-ray luminosity of
HMXBs in a galaxy can be used as an independent star formation rate
(SFR) indicator. Although more subtle SFR dependent effects are
likely to exist, the data in the log(LX) > 36 luminosity range
are broadly consistent with existence of a universal luminosity
function of HMXBs which can be roughly described as a power law with
differential slope of ~ 1.6, a cutoff at log(LX[erg/s])~
40.5 and the normalization proportional to the star formation
rate. The high luminosity part of this distribution corresponds to the
ULX sources found in many starburst galaxies.
Applying our results to high redshift (up to z~ 1.2) starburst
galaxies observed by CHANDRA in the Hubble Deep Field North we show
that the calibration of the collective luminosity of HMXBs as a SFR
indicator based on the local sample agrees well with the SFR estimates
obtained for these distant galaxies with conventional methods.
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HMXB, ULX and Star Formation |
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Gogus, Ersin, Finger, M., Kouveliotou, C., Woods, P., Patel, S.,
Rupen, M., Swank, J., Markwardt, C., and van der Klis, M.
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"Long-term Spectral and Timing Behavior of XTE J1908+094"
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The X-ray transient XTE J1908+094 was serendipitously discovered
during RXTE ToO observations of SGR 1900+14 in February 2002.
Following the discovery, RXTE routinely monitored the region. At the
onset, the source was found in a spectrally hard/low state lasting for
~40 days, followed by a quick transition to the soft/high state. At
the highest X-ray intensity level (seen on April 6), the source flux
(2-10 keV) reached ~105 mCrab, then decayed rapidly. Overall outburst
characteristics resemble the transient behavior of galactic black hole
candidates. Here, we present the long term light curves, and detailed
spectral and timing investigations of XTE J1908+094 using RXTE PCA
data. We also report the results of Chandra ACIS-S and BeppoSAX MECS
observations which were performed during the decay phase.
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H, I, J
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Hewitt, Jacqueline
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"LOFAR" (Invited)
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Hynes, Rob
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"Variability in Quiescent Black Holes"
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Multiwavelength studies of Galactic black holes have focussed upon
X-ray bright states when high quality data can be obtained. However,
with the advent of Chandra and XMM, and the increased availability of
large optical telescopes, we can also study properties of the
quiescent state, such as variability in some detail. I will discuss
what is known about variability in the quiescent state at different
energies, possible origins for it, and what may be learned with
multiwavelength studies.
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Variability in Quiescent Black Holes |
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In 't Zand, Jean
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"Six years of XRB monitoring by the BeppoSAX Wide Field Cameras"
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From August 1996 untill the switch off on April 30, 2002, the Wide
Field Cameras on the Italian-Dutch BeppoSAX satellite carried out
twelve campaigns on the Galactic center region, with a total exposure
time of over 6 Msec and covering half the low-mass X-ray binary
population in our galaxy. These observations, as well as others with
WFC, resulted in the discovery of 19 new faint transient X-ray
binaries, the discovery of superbursts, and the detection of type-I
bursts with very low persistent flux levels. Many of the new
discoveries were followed up with the Narrow Field Instruments on
BeppoSAX, and some with Chandra and XMM-Newton. We briefly review the
results of this succesful program, emphasizing recent findings.
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Jimenez-Garate, Mario
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"X-ray Spectroscopy and Modeling of Low-Mass X-ray Binaries"
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I discuss analysis and modeling techniques which are applicable to
line emission spectra from Low-Mass X-ray Binaries. Models can be used
to identify whether we are observing an accretion disk, an illuminated
companion, or some other structure. I discuss 'generic
photoionization' and 'accretion disk atmosphere' models which take us
a step further in identifying the emitter, measuring elemental
abundances, and exploiting plasma diagnostics. I review some LMXB
spectra observed with the Chandra HETG and the XMM-Newton RGS.
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X-ray Spectroscopy and Modeling of Low-Mass X-ray Binaries |
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Jonker, Peter
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"Chandra Observations of RX J170930.2-263927"
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We will present results from our Chandra DDT observations of the
neutron star Soft X--ray transient RX J170930.2-263927 carried out
last spring. We will show that the properties of this transient source
fit in with those of the recently described sub-class of faint Soft
X-ray transients. We will present evidence suggesting that RX
J170930.2-263927 may well be an ultra compact X-ray binary by analogy
with other suspected ultra compact sources.
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Chandra DDT Observations of the Soft X-ray transient RX J170930.2-263927 returning to Quiescence |
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Juett, Adrienne
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"High-Resolution Spectroscopy of Ultracompact Binaries"
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Observational evidence suggests that >10% of all known low-mass X-ray
binaries have orbital periods shorter than 1 hour. These so-called
ultracompact binaries require hydrogen-deficient or degenerate
companions, usually assumed to be He white dwarfs. However, the
Chandra spectrum of the ultracompact binary 4U 1626-67 revealed O and
Ne emission and absorption features which led the authors to conclude
that the donor is a carbon-oxygen WD. Unusual implied abundances from
neutral absorption edges have also been found in 4 candidate
ultracompact systems. I will present an overview of the Chandra and
XMM-Newton spectral results from the known and candidate ultracompact
binaries. In addition, I will address the implications of recent
results on the nature of the companions in these systems and the
formation of ultracompact binaries.
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High-Resolution Spectroscopy of Ultracompact Binaries |
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K
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Kaaret, Phil, Corbel, S., Tomsick, J. A., Fender, R., Miller, J. M.,
Orosz, J., Tzioumis, T., and Wijnands, R.
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"Decelerating relativistic jets from XTE J1550-564"
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We present the first direct evidence for gradual deceleration of
relativistic jets from an accreting compact object. Triggered by the
discovery of large-scale jet emission in the radio from the
microquasar XTE J1550-564, multiple Chandra images of the jets provide
a unique opportunity to study the dynamical evolution of relativistic
jets on time scales inaccessible for active galactic nuclei jets. The
broad band spectrum of the jets is consistent with synchrotron
emission from particles accelerated up to 10 TeV. The morphology of
the radio and X-ray emission is suggestive of interaction of the jets
with the interstellar medium.
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Kallman, Tim, Angelini, L., Cottam, J., and Boroson, B.
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"Chandra and XMM Observations of the ADC Source 0921-630"
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We analyze observations of the low mass X-ray binary 2S0921-63
obtained with the gratings and CCDs on Chandra and XMM. This object
is a high inclination system showing evidence for an accretion disk
corona (ADC). Such a corona has the potential to constrain the
properties of the heated accretion disk in this system, and other
LMXBs by extension. We find evidence for line emission which is
generally consistent with that found by previous experiments, although
we are able to detect more lines. For the first time in this source,
we find that the iron K line has multiple components. We set limits
on the line widths and velocity offsets, and we fit the spectra to
photoionization models and discuss the implications for accretion disk
corona models. For the first time in any ADC source we use these
fits, together with density constraints based on the O VII line ratio,
in order to constrain the flux in the medium-ionization region of the
ADC. Under various assumptions about the source luminosity this
constrains the location of the emitting region. These estimates,
together with estimates for the emission measure, favor a scenario in
which the intrinsic luminosity of the source is comparable to what we
observe.
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Chandra and XMM Observations of the ADC Source 2S0921- 63 |
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Kohmura, Takayoshi
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"The Hard X-ray Advance in the Centaurus X-3 and Its X-ray Emission Mechanism"
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Strong iron K lines observed from Centaurus X-3 (Cen~X-3) are
considered to come from a re-processing matter around the neutron
star, e.g. the Alfv'en shell. Thus the X-rays in the
energy band containing the iron K lines ("iron-band") is expected to
have a certain delay from the higher energy X-rays.
We discovered the significant time delay of temporal variation of
"iron-band" as compared with that of the other continuum X-rays by
(6.0 ± 2.4)~ms, (4.0 ± 3.8)~ms, and (10.1 ± 4.9)~ms, Appling
cross spectrum to all archival RXTE data of Cen~X-3. These
results lead to a determination of (1.8 ± 0.7) x 108 cm,
(1.2 ± 1.1) x 108 cm, and (3.0 ± 1.7) x 108
cm for the distance between the original X-ray source, neutron star,
and the reprocessor, which emits the iron lines.
From most of observation data, we also discovered the time difference
showed a general trend such that the higher energy X-rays advanced in
comparison with the lower energy X-rays. If this advance is originate
at the X-ray emission region around the neutron star polar cap, the
inverse Compton scattering is not the main process of the continuum
X-ray emission.
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The Hard X-ray Advance in the Centaurus X-3 and Its X-ray Emission Mechanism |
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Kong, Albert, Garcia, M. R., Primini, F. A., McClintock, J. E.,
Murray, S. S., and Di Stefano, R.
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"Chandra/HST Observations of X-ray Transients in M31"
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M31 has been monitored by the HRC and ACIS detectors aboard Chandra
from 1999 to 2002. We report here a summary of properties of X-ray
sources in M31 with a focus on an ongoing Chandra/HST program to
monitor X-ray transients in M31. By comparing individual X-ray images,
more than 100 sources were found to be variable (half the total number
observed) on a time scale of months. Combining our sample with all of
the available transients found in the literature, there are ~30
transients in M31 and M32 detected by Chandra and XMM. We also perform
follow-up observations with HST to search for the UV counterparts of
transient sources. While no definitive UV counterparts have been found
so far, the X-ray brightest of these transients has the strongest
candidate counterpart. The discovery of repeated outbursts from three
of the transients yields new direct information on duty cycles of
transients in M31.
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Chandra/HST Observations of X-ray Transients in M31 |
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Markwardt, Craig, on behalf of the Swift Team
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"Monitoring and Detecting X-ray Transients with the Swift Observatory" (Invited)
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Swift is a multi-wavelength observatory specifically designed to
detect transients sources in the gamma-ray energy band 15-200 keV.
The primary goals of the mission involve gamma ray burst (GRB)
astronomy, namely to determine the origin of GRBs and their
afterglows, and use bursts to probe the early Universe. However,
Swift will also discover new X-ray transient sources, and it will be
possible to bring Swift's considerable multi-wavelength capabilities
to bear on these sources, and those discovered by other means. The
Burst Alert Telescope (BAT) is a coded mask instrument sensitive to
15-200 keV gamma rays, and has a field of view which covers
approximately 1/8th of the sky in a single pointing. Over a typical
observing day, the almost the entire sky will be observed and
monitored for new transient sources. Sources will be detected within
several hours of observation. The two narrow field instruments, the
X-ray Telescope and Ultra-Violet Optical Telescope, can provide
sensitive simultaneous imaging and spectroscopy observations in the
optical through soft X-ray bands. The Swift science operations team
will entertain requests for targets of opportunity for sources which
are astrophysically significant. Swift will be ideally suited for the
detection of transients which produce hard X-rays, such as black hole
binaries and some neutron star systems.
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Monitoring and Detecting X-ray Transiants with the Swift Observatory |
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Marshall, Herman, Schulz, N. S., Fang, T., Cui, W., Canizares, C. R.,
Miller, J. M., and Lewin, W. H. G.
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"Highly Ionized Absorption in the X-ray Spectrum of Cyg X-1"
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Using the Chandra High Energy Transmission Grating Spectrometer
(HETGS), we have found significant absorption features in the X-ray
spectrum of Cyg X-1 taken in the continuous clocking mode. These
features include resonance lines of He-like ions of S, Si, and Mg; the
Ly alpha lines of H-like S, Si, Mg, and Ne; and several lower
ionization lines of Fe XX, XXII, and XXIV. The
lines are resolved in many cases, giving line widths of order 300 km/s
and the are redshifted by 460 ± 10 km/s. These features are
interpreted in the context of an accreting stellar wind model that is
ionized by the X-ray source. In addition, there are clear absorption
features due to neutral Mg, Fe, and O in the interstellar medium.
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McGowan, Katherine, Priedhorsky, William, and Trudolyubov, Sergey
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"On the Correlated X-ray and Optical Evolution of SS Cygni"
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We present an analysis of simultaneous RXTE/ASM and optical AAVSO
observations of SS Cygni over a ~5 yr period. By summing the X-ray flux
over multiple outbursts, phased using the optical light curve, we find
that the hard (3-12.2 keV) X-rays are suppressed during outburst.
This confirms the trend seen in the few outbursts previously observed.
The several outbursts of SS Cygni observed with the more sensitive
RXTE/PCA also show depression of the hard X-rays during optical
outburst. We quantify the time lags between the optical and X-ray
outbursts, and the time scales of the hard X-ray spectral recovery
from outburst. The optical light curve of SS Cygni exhibits anomalous
or "mini" outbursts. During these events, the hard X-ray and optical
flux increase is correlated. We also investigated the optical and
X-ray evolution of SS Cygni during quiescence using the RXTE/ASM and
AAVSO data. Our results suggest that the hard X-ray flux declines
between one outburst and the next. We discuss our observational
results in the framework of the theoretical models of the accretion
flow in dwarf novae systems.
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On the Correlated X-ray and Optical Evolution of SS Cygni |
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McSwain, Ginny
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"Wind Accretion in Cygnus X-1"
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The H-alpha emission strength in Cygnus X-1 provides an important
probe of the mass loss rate in the base of the stellar wind of the
supergiant star. Optical spectra of the system from 1998 to 2002 show
large variations in H-alpha over both long (years) and short (hours to
days) timescales. When the spectra are grouped by H-alpha equivalent
width, coherent orbital phase related variations in the profiles are
seen. There is also an anti-correlation between the H-alpha emission
strength and X-ray flux (from the Rossi X-ray Timing Explorer All Sky
Monitor instrument) in the sense that when the H-alpha emission is
strong the X-ray flux is weaker and the spectrum harder. On the other
hand, there is no correlation between H-alpha emission strength and
X-ray flux when H-alpha is weak. This relationship is not likely to
be caused by wind X-ray absorption nor by the reduction in H-alpha
emissivity by X-ray heating. Instead, the H-alpha variations probably
track changes in wind density and strength near the photosphere. The
density of the wind determines the size of X-ray ionization zones
surrounding the black hole, and these in turn control the acceleration
of the wind in the direction of the black hole. During the low/hard
X-ray state, the strong wind is fast and the accretion rate is
relatively low, while in the high/soft state the weaker, highly
ionized wind attains only a moderate velocity and the accretion rate
increases. It is also possible that X-rays from near the black hole
cause radiative driving away from the accretion disk, further slowing
the wind and enabling more accretion. The X-ray transitions from the
normal low/hard to the rare high/soft state are probably triggered by
episodes of decreased mass loss rate in the supergiant donor star.
High resolution Chandra spectra can help us understand the complex
relationship between the variable stellar winds from the supergiant
star and the X-ray flux from near the black hole. Schulz et
al. (2001) took the first high-resolution spectrum of Cygnus X-1, at
orbital phase phi = 0.93, during a transitional period of X-ray
flaring within its low/soft state. Miller et al. (2002) and Marshall
et al. (2001) also observed Cygnus X-1 at orbital phases phi = 0.76
and phi = 0.84 respectively, and they found distinct differences in
the X-ray spectrum that could be attributed to either orbital phase or
the longer term state of the system. Further observations during a
constant high/soft state and low/hard state, combined with
simultaneous H-alpha observations, would improve our knowledge of both
long and short term changes in the ionization structure of the wind
and accretion disk as the mass loss rate of the supergiant star
changes. Chandra spectra during the high/soft state would also allow
us to model the deceleration of the stellar winds due to X-ray
radiation driving as they approach the black hole.
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Miller, Jon
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"Diagnosing Spin in Galactic Black Holes"
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Our observations of Cygnus X-1 with Chandra and XTE J1650-500 with
XMM-Newton have revealed broad, skewed Fe K-alpha emission lines like
those seen in some AGN. These lines are likely produced at the inner
accretion disk, and may be used to constrain the inner radial extent
of the disk and thereby black hole spin. In the case of XTE
J1650-500, near-maximal spin may be required. Simultaneous
observations with RXTE are critical for understanding the underlying
spectrum, and for constraining the accretion flow geometry through
reflection models. Moreover, the detection of high-frequency QPOs in
simultaneous RXTE observations can provide a second spin constraint.
We will present the results of our work, and discuss our findings in
the context of other recent reports of broad Fe K lines and evidence
for black hole spin. Finally, we will comment on the prospects for
revealing black hole spin and accretion flow geometries with future
observations.
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Diagnosing Spin in Galactic Black Holes |
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Mukai, Koji, Pence, W. D., Snowden, S. L, and Kuntz, K. D.
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"X-ray Binaries in M101"
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We present the results of Chandra ACIS-S observations of the nearby
face-on spiral galaxy, M101. We present spectra and light curves of
five bright X-ray sources that can be described as bright black hole
binaries in M101. The brightest source detected (P098), however, does
not fit the norm, although it, too, is likely to be a black hole
binary in M101. We argue that the observed X-ray photons may have
been scattered in an outflow, rather than originating in the accretion
disk. We also compare the X-ray binary population of M101 with that
of the Milky Way.
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X-ray Binaries in M101 |
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Muno, Michael
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"X-ray Sources in the Chandra Deep Exposure of Sgr A*"
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We present the catalog of 2400 point sources detected during 600 ks of
Chandra observations of the 17 by 17 arcminute field around Sgr A*.
This field encompasses a physical area of 40 by 40 parsec at 8 kpc.
The completeness limit of the sample at the galactic center is 10^31
erg/s (2-8 keV), while the detection limit is a order of magnitude
lower. Fewer than 60 of the observed sources are background AGN. The
log(N)-log(L) distribution of the galactic center sources is extremely
steep, such that point sources can account for all of the previously
reported diffuse emission if it extends down to 10^29 erg/s. However,
there are numerous filamentary structures in the field that also
contribute to the total flux, which implies that the luminosity
distribution between 2-8 keV must turn over below our completeness
limit. The spectra of the majority of the galactic center sources are
very hard, and are best described by a powerlaw (E^Gamma) with photon
index Gamma > -1. Such hard spectra are only seen from magnetically
accreting white dwarfs (polars and intermediate polars) and neutron
stars (pulsars). Several interesting individual sources are also
present in the field, including three low-mass X-ray binaries in
quiescence, and five sources that vary with periodicities between 90
minutes and 5.4 hours.
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X-ray Sources in the Chandra Deep Exposure of Sgr A* |
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N, O, P, Q
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Orio, Marina
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"Peculiar post-novae and other supersoft X-ray sources as progenitors of type Ia supernovae: the observations we need"
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I will present some recent XMM-Newton observations of Nova LMC 1995,
and I will also review previous results on other sources, obtained by
my group and others, to show what clues we have at present to
understand the secular evolution of these systems and their possible
role as type Ia supernova progenitor. I will also illustrate what type
of observational results we need to achieve, in order to solve the
puzzles we are confronted with.
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Orosz, Jerome
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"Quiescent Optical Observations of V4641 Sgr"
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We present extensive photometry and echelle spectroscopy of V4641 Sgr
in quiescence. The photometric observations are in 7 filters (U, B,
V, R, I, J, and K), collected with four different 1m-class
telescopes. The phase coverage is nearly complete. The echelle
spectra, obtained with VLT/UVES, have a resolving power of R=33,000
and a signal-to-noise ratio of more than 100. From the spectra we
derive a projected rotational velocity of V_rot*sin(i) = 98.9 +/- 1.5
km/sec for the secondary star. The light curves are ellipsoidal with
large amplitudes (~0.4 mag in V). From detailed ellipsoidal modelling
of the light and velocity curves, and using the constraint that
V_rot*sin(i) = 98.9 +/- 1.5 km/sec, we find an inclination of 75 +/- 2
degrees (1 sigma), and a 1 sigma mass ratio range of 2.22 - 2.39. The
derived 1 sigma range for the black hole mass is than 6.82 < M_BH <
7.42
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Pooley, David
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"Globular Cluster X-ray Binaries"
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Globular clusters are a favored environment of X-ray binaries, with
formation rates per unit mass exceeding those in the Galactic disk by
orders of magnitude. There is now a wealth of Chandra data on
globular clusters, revealing hundreds of low-luminosity X-ray
sources, most of which are either quiescent low-mass X-ray binaries,
cataclysmic variables, or millisecond pulsars. There are also
thirteen bright X-ray sources known in globular clusters, but the
focus of my presentation will be on the more numerous population of
dim sources. In addition to their important role in globular cluster
evolution, these sources can also be studied for what they are,
namely, X-ray binaries. Globular cluster X-ray binaries have the
advantages of accurately known distances and numerous other sources
in the field for comparison. From neutron star radius measurements
to the L_x vs E-dot relation for millisecond pulsars, I will discuss
how the data are presently being used (with the hope of sparking new
ideas) and summarize the current state of affairs.
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Globular Cluster X-ray Binaries |
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Quaintrell, Hannah, Vrtilek, Saku, and Boroson, Bram
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"An Atlas of Chandra ACIS-S/HETG spectra of X-ray binaries"
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We are extracting all the ACIS-S/HETG data of black hole & neutron
star binaries from the Chandra archive, reprocessing them with
up-to-date calibration (where necessary) and collecting them together
with the other files necessary for the modeling of X-ray spectra. This
is being done to enable easy comparison of different X-ray binaries'
X-ray spectra and also to facilitate correlation studies with catalogs
at different wavelengths.
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R
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Remillard, Ron
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"Coordinated Chandra / RXTE Observations of Black Hole Binaries" (Invited)
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The science issues related to Chandra observations of X-ray binary
systems are briefly reviewed, with emphasis on TOOs triggered by
RXTE. The black hole binaries particularly illustrate the need for TOO
programs, since the accretion rate is extremely variable. Furthermore,
many of the outstanding science problems, such as jet formation, high
frequency oscillations, ghe canonical emission states, and broad Fe
emission, are transient phenomena within a given outburst.
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Revnivtsev, Mike
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"The Super-Eddington Outburst of V4641 Sgr"
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We would like to draw attention to super-eddington outburst in the
binary system V4641 Sgr. We show, that available optical and X-rays
data of its outburst in 1999 strongly suggest the of an extended
envelope surrounding the source which absorbs X--ray flux and reemits
it in the optical and UV. This envelope is likely the result of a
near- or super-Eddington rate of mass accretion onto the black
hole. The envelope vanishes during subsequent evolution of the source
when the apparent luminosity drops well below the Eddington
value. Thus this transient source provides us with direct proof of the
dramatic change in the character of an accretion flow at the mass
accretion rate near or above the critical Eddington value as predicted
long ago by the theoretical models. Super-eddington outbursts like
that was demonstrate by V4641 Sgr should be extremely interesting for
high presicion spectrocopy missions like CHANDRA and XMM - the
exanding envelope can provide a lot of lines that could be used for
its diagnostics.
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The Super-Eddington Outburst of V4641 Sgr |
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Rupen, Michael
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"Radio Monitoring and the Radio/X-ray Connection" (Invited)
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Rutledge, Robert
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"The Intensity Variability of Transiently Accreting Neutron Star Low Mass X-ray Binaries, in Quiescence"
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The thermal luminosities of quiescent neutron stars (qNSs) can be
predicted on the basis of outburst properties from deep crustal
heating (DCH), where reactions in the crust deposit energy in
proportion to the mass accreted. Observations of qNSs' luminosities
are in agreement with this hypothesis, although some (Cen X-4, KS
1731-260) require recurrence timescales of 100-1000 yr, or longer. In
addition, DCH places the energy source of the quiescent thermal
emission in the NS crust and core. Examination of the X-ray intensity
variability which can result from DCH shows that it is restricted in
the permissible timescales and magnitude. I will review the
predictions for intensity variability in qNSs, compare these with
observations of systems in quiescence -- in pariticular, Aql X-1 and
KS 1731-260 -- and discuss what has been and can be learned about the
mechanisms which power these systems in quiescence.
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S
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Schulz, Norbert
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"Highly Resolved X-ray Spectra from Galactic Objects with Chandra"
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The High Energy Transmission Grating Spectrometer (HETGS) onboard the
Chandra X- ray Observatory has so far produced a large number of high
resolution X-ray spectra providing us with unprecedented spectroscopic
details. Spectra of bright X-ray sources reveal plasmas with a wide
range of properties. Through the measurements of blue- and r edshifts
the complex dynamics of these plasmas is revealed. X-ray absorption
edges reveal structure of high complexity and the determination of
their peculiar shap es do not only improve spectral models but also
allow to draw conclusions on the chemical composition of the absorbing
medium. Line diagnostic tools and more accurate atomic data bas es now
also allow to model the properties of various plasmas in detail and to
constrain their spatial distribution and dynamics. In various
examples, i.e. plasmas from accret ion disks, winds, stationary clouds
as well as the ISM, the power of highly resolved X-ray spectra is
demonstrated.
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Shrader, Chris
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"Monitoring with INTEGRAL" (Invited)
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It is currently anticipated that the INTErnational Gamma-Ray
Astrophysics Laboratory (INTEGRAL) will have been launched, and
undergoing verification phase operations by the time of this
workshop. I will present a status report, in addition to an overview
of the observatory, drawing from pre-launch laboratory calibration
tests and simulations. Emphasis will be placed on its capabilities for
transient detection and monitoring, as well as its anticipated more
general contributions to X-Ray binary studies. As part of the Core
Observing Program, which comprises 35% of the available observation
time for the first year of the mission, weekly scans of the Galactic
plane will be conducted. The sensitivity for transient detection
should be ~20 mCrab at 100 keV and ~800 mCrab at 1 MeV. I will discuss
the prospects for this strategy and the planned followup (ToO)
studies, under both the Core and Open Time Programs.
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INTEGRAL: Summary & Status |
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Smith, David, Heindl, William, and Swank, Jean
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"Long-Term Hysteretic Behavior in Black-Hole Binaries: Galactic and Extragalactic Monitoring"
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Regular, frequent monitoring of the persistent black hole candidates
1E 1740.7-2942 and GRS 1758-258 has yielded two discoveries about
these systems: the complexity of the relationship between their
luminosity and spectral shape (in contrast to Cyg X-1, in which
brightness and softness correlate closely) and their orbital periods,
manifested in weak x-ray modulations. In addition, recent
observations of these sources and Cyg X-1 show that extreme but very
rare variations can take place in these systems on the scale of hours.
After reviewing these recent results, we will discuss the capabilities
of Chandra, Newton, and future missions to deduce the properties of
similar binaries in nearby galaxies via similar observations.
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Long-Term Hysteretic Behavior in Black-Hole Binaries: Galactic and Extragalactic Monitoring |
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Smith, Ian
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"Energy-Dependent Variability of Galactic Black Holes"
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Detailed studies of the energy dependence of the rapid X-ray
variability of Galactic Black Hole Candidates have provided important
insights into the plasma components that make up these complex
accretion-outflow systems. Here we will summarize some of our recent
studies and upcoming observations.
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Stark, Michael, and Saia, Malinda
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"Measuring the orbital parameters of Cygnus X-3"
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Using Chandra data, we have measured phase dependent Doppler shifts in
several emission lines in the spectrum of Cygnus X-3. These
measurements have enabled us to put an upper limit on the mass of the
system that constrains the compact object to < 3.6 MSun. The
companion is also constrained to < 7.3MSun. We also make indirect
measurements of the orbital distance of the system and the size of the
companion. Our analysis prefers models of the system with a small
inclination of the orbital plane to the line of sight and a small
nonzero eccentricity. Future observations ought to constrain this
system much more strongly.
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Orbital Modulation of Doppler Shifts of X-ray Spectral Features in Cygnus X-3 |
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Strohmayer, Tod
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"The promise of TOO observations of superbursts"
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Swank, Jean, and Markwardt, Craig
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"RXTE PCA Contributions to Monitoring Faint Transients"
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The RXTE PCA has monitored the galactic bulge for 4.6 years. MXB
1730-33 and the 12 hr eclipsing binary Terzan 6 have the shortest
recurrence periods, 150-200 days, and outburst durations of a few
weeks. The variations of their outbursts are well sampled. The 2-20
year recurrent transients like EXO 1745-248, SAX J1750.8-2900, and
SAXJ1747.0-2853 have generally fast rises and slow decays.
Oscillations in the decays and large differences in peak fluxes
prevent specific prediction of the course of a given outburst, but
there are predictive correlations, and subsidence below a flux of 1/2
mCrab can be certified fairly reliably. KS 1731-26 turned off after
being on at least 4.5 yr. 4U 1711-34 and XTE J1723-376 may have done
the same. On the other hand, XTE J1759-220 came on 1.6 yr ago, after
being off at least 2 years. These sources represent a range of source
types in which certain levels of mass exchange are currently being
driven. Of particular interest have been the millisecond pulsars SAX
J1808.4-3658 and XTE J1751-305 and the black hole candidate V4641 Sgr,
but better positions, spectroscopy, and timing begin to provide more
in depth information about some of the others.
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RXTE PCA Contributions to Monitoring Faint Transients |
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T, U, V
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Tiengo, Andrea
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"XMM-Newton observation of the millisecond x-ray pulsar XTE J1751-305 in outburst"
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XMM-Newton observed XTE J1751-305 for about 35 ksec just 3 days after
its discovery. No convincing emission or absorption features are
detected in the PN and RGS spectra. The broad band spectrum cannot be
fitted with a simple absorbed power-law model, but a blackbody
component is also required. The results of the pulse-phase
spectroscopy will also be discussed.
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Trudolyubov, Sergey, Priedhorsky, W. C., Borozdin, K. N., Mason,
K. O., Cordova, F. A., Osborne, J. P., and Watson, M. G.
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"XMM-Newton Survey of X-ray Binaries in M31"
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We present the results from XMM-Newton survey of M31. Nearly 400 out
of total 600 X-ray sources detected in the survey can be classified as
X-ray binary candidates. Unprecedented sensitivity of XMM-Newton
allowed a detailed study of spectral properties and variability of new
and previously known X-ray emitting binary systems. Correlation
between the spectral properties and level of X-ray flux has been found
for several sources. A short-term periodic variability of two X-ray
sources (a supersoft transient XMMU J004319.4+411759 and globular
cluster candidate Bo 158) has been discovered. We present luminosity
functions of X-ray binaries in the bulge and disk regions of M31,
providing the first convincing evidence for the difference between
these source populations. We discuss individual and group properties
of X-ray binaries of various classes (X-ray transients, globular
cluster sources, supersoft sources) detected in our survey.
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Uemura, Makoto
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"Optical rapid variations in the microquasar V4641 Sgr"
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V4641 Sgr is now widely known as a superluminal jet source which
experienced a luminous outburst lasting only a few hours in 1999
September. Here we report another outburst and active phase of V4641
Sgr detected in 2002 May-July. Our optical photometric campaign
through VSNET (Variable Star Network) revealed some unprecedented
variations which were not observed during the 1999 outburst. The most
impressive one is optical short-term fluctuations. The power spectra
of the fluctuations are characterized by a power law (index=-1.7).
During the most prominent "optical flash", the optical flux increased
by 1.2 mag only within 30 s, in other words, the energy release rate
reached over 5*10^36 erg/s. This strongly indicates the optical
emission source at the innermost part of accretion flow. We suggest
that, in such an inner region, the synchrotron emission from jets or
magnetic flares is the most promising radiation mechanism of the
optical emission. Since the discovery in 1999, V4641 Sgr has
experienced some distinct states. This behavior is reminiscent of GRS
1915+105 except for the strong optical emission in V4641 Sgr. We
review observational properties of these active states, and urge
international campaigns with TOO observations of Chandra and
XMM-Newton for coming events.
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Vilhu, Osmi, for the INTEGRAL collaboration
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"Bright LMXBs in INTEGRAL's Core Program"
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The collaboration is preparing a monitoring campaign of 'Bright Low
Mass X-ray Binaries' in the INTEGRAL core programme. At present, the
target list includes 72 sources with nine of them persistently
brighter than 100 mCrab. These will be observed during the weekly
Galactic Plane scans and less frequent Galactic Center Deep Exposures.
A special attention will be given to transients, ToO's
and other significant changes. We will attempt to provide on a
regular basis the fluxes, colors and light curves in our home page
http://isdc.unige.ch/~paizis/lmxrb (to be ready soon). This web-page
gives the target list and other useful information, including the
detailed scheduling when available. During the presentation I plan to
show some feasibility estimates and simulations.
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Bright LMXRBs in INTEGRAL's Core Program |
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Vrtilek, Saku, Leblang, A. B., Shields, M., Quaintrell, H., and
Boroson, B.
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"Coordinated Chandra/HST Studies of Stellar Wind X-ray Binaries"
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Chandra (ACIS-S) and HST Observations of SMC X-1 and LMC X-4 during
both high and low states will be discussed. The X-ray spectra are
dominated by continuum emission in the X-ray high state. A new
analysis, incorporating corrections for pile up of the high state
data, will be presented. During eclipse and during the X-ray low
state the continuum emission largely disappears and we see line
emission from O, Ne, Mg, and Fe and possibly from Si and S. The
emission lines are consistent with recombination lines from mostly
hydrogenic and helium-like species which could be produced by
photoionization in an extended stellar wind. The ultraviolet P-Cygni
lines show strong broad absorption near X-ray eclipse and only narrow
interstellar absorption when the X-ray source is in the line-of-sight.
We interpret this as a result of X-ray photoionization of the stellar
wind which renders the wind transparent in the vicinity of the X-ray
source. The UV continuum fluxes remain roughly constant in spite of
more than an order of magnitude change in X-ray flux between high and
low-states, as would be expected if the X-ray flux reduction is due to
occultation of the X-ray source (e.g., by a precessing disk) rather
than to an intrinsic change in X-ray luminosity.
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W, Z
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Wachter, Stefanie, and Smale, Alan
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"Precise Localizations of LMXBs with Chandra: The ``Big Dipper'' X1624-490"
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One major obstacle in the study of low mass X-ray binaries (LMXBs) is
the difficulty in identifying their optical/IR counterparts in the
heavily extincted and crowded regions of the Galactic plane. Chandra,
with its spatial resolution of < 1", is providing major advances for
this particular problem. We will present a precise position for the
dipping LMXB X1624-490 obtained with the Chandra HRC. X1624-490 stands
out among the currently known dipping sources: its persistent emission
is the brightest, its 20.88 hour orbital period the longest and its dip
profiles the most erratic in its class. We will also report on the
search for the optical/IR counterpart using our precise Chandra
localization.
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Wilms, Joern, on behalf of the Accreting Neutron Star Team of the
INTEGRAL GPS
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"Persistent Accreting Neutron Stars in the INTEGRAL Galactic Plane Survey"
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The INTEGRAL Galactic Plane Survey consists of weekly scans of the
galactic plane, during which a large number of different objects will
be observed. Our collaboration is responsible for the processing of
the data from the ~25 persistent accreting neutron stars. Our plan is
to provide the community with basic data (spectral shape, flux, pulse
period,...) from the INTEGRAL observations shortly after the data have
been taken. Furthermore, simultaneous observations with other
instruments are planned. All of these observations will be
supplemented with information on the past source behavior, building on
a database of earlier observations and fundamental parameters of these
sources. I will report on the status of these efforts and will present
information about the sensitivity of the plane survey for the class of
persistent accreting neutron stars.
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Wilson-Hodge, Colleen, for the BATSE team
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"9.1 Years of All-Sky Hard X-ray Monitoring with BATSE"
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The hard X-ray sky was continuously monitored with the BATSE
experiment on the Compton Gamma Ray Observatory using the Earth
Occultation method. Known sources were monitored twice every orbit
and transients could be detected at about the ~50 mCrab level on a
daily basis. Long-term, post-processing of the complete BATSE dataset
will produce all-sky, hard X-ray maps at a sensitivity level of ~5
mCrab in un-crowded regions. For long period pulsars (>1 second),
Fourier transforms and epoch-folded searches were used to measure
pulse frequency and pulsed flux. Using these methods, 3 black hole
candidates and 6 X-ray pulsars were discovered with BATSE during its 9
years in orbit. I will present highlights from BATSE observations of
X-ray binaries from 9 years of monitoring the hard X-ray sky.
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9.1 Years of All-Sky Hard X-ray Monitoring with BATSE |
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Wilson-Hodge, Colleen, Patel, S. K., Kouveliotou, C., van der Klis,
M., Belloni, T., and Lewin, W. H. G.
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"Chandra Observations of Faint LMXBs"
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There exists a group of persistently faint galactic X-ray sources that
based on their location in the galaxy, high Lx/Lopt, association with
X-ray bursts, and absence of X-ray pulsations are thought to be
low-mass X-ray binaries (LMXBs). We present results from Chandra
observations for 7 of these systems: 1708-408, 1711-339, 1735-269,
1736-297, 1746-331, 1746.7-3224, and 1812-12. Improved locations for
all sources, excluding 1736-297 and 1746-331 (which were not detected)
are presented. Our observations are consistent with previously
reported transient behavior of 1736-297, 1746-331, and 1711-339 (which
we detect in one of two observations). Energy and power spectra are
presented for 1735-269, 1711-339, and 1746.7-3224. The energy spectra
are hard, consistent with typical faint LMXB spectra. Further, we
present a newly discovered source, a very faint, soft, source,
separated by 2.7' from 1746.7-3224.
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Chandra Observations of Faint LMXBs |
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Wojdowski, Patrick
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"A Sobolev Monte Carlo Scattering Method from HMXB Winds"
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We present a method for a Monte Carlo calculation of resonant line
scattering in the supersonic wind of a HMXB. An analytic solution to
this problem is intractable because resonant line scattering is
anisotropic and polarizing, and, in the rest frame of the gas where a
photon is scattered, the frequency of the photon after scattering
depends on the frequency of the photon before scattering. In this
Monte Carlo calculation, we follow photons though individual "Sobolev
zones" which have small spatial extent. Because of the supersonic
expansion of the wind, photons of a given frequency interact in line
transitions only inside a single Sobolev zone and not elsewhere in the
wind. We assume that the wind velocity distribution is spherically
symmetric, implying that there are only three relevant parameters for
any Sobelev zone: the optical depth in directions parallel and
perpendicular to the wind motion, and the angle from the direction of
wind motion from which the Sobolev zone is illuminated by the compact
object. Therefore, if we simulate resonant line scattering in a
number of Sobolev zones with representative values of the three
parameters, we can construct line profiles for any HMXB as a weighted
sum of the from a number of Sobolev zones.
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A Sobolev Monte Carlo Scattering Method from HMXB Winds |
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Zdziarski, Andrzej
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"Variability patterns of black hole binaries"
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I present results of studies of the variability patterns of black-hole
binaries on long time scales (>1 day). The variability of Cyg X-1 in the
hard state consists mostly of pivoting with the pivot energy near 50 keV.
In the soft state, its variability is of a high-energy tail on top of a
constant blackbody. These patterns (as given directly by spectral
variability as well as by rms as function of energy) can be theoretically
interpretated as caused by variations of the flux of seed soft photons
incident on the hot plasma with a near-constant luminosity in the hard
state, and by variations of the luminosity of a hot plasma irradiated by
near-constant blackbody photons in the soft state. The two geometries
corresponding to the two patterns are an overlapping hot and cold
accretion flows, and nonthermal flares on top of a stable thin disk,
respectively. Notably, the overall power spectrum of Cyg X-1 has most
power at those long time scales. I also discuss the relationship to short
time scale variability in Cyg X-1, as well as the case of GX 339-4.
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