2,974 research outputs found
Spitzer Space Telescope Observations of Low Mass X-ray Binaries
We present preliminary results from our archival Spitzer Space Telescope
program aimed at characterizing the mid-IR properties of compact objects, both
isolated and in binary systems, i.e. white dwarfs, X-ray binaries, cataclysmic
variables, and magnetars. Most of these sources are too faint at mid-IR
wavelengths to be observable from the ground, so this study provides the very
first comprehensive look at the mid-IR emission of these objects. Here we
present our results for the low mass X-ray binaries. We considered all of the
systems listed in the most recent catalog of Liu et al. (2007) that have known
optical counterparts. The particular goals of our projects encompass: to
establish the mid-IR spectral energy distribution, to search for the signatures
of jets, circumbinary disks, low mass or planetary companions and debris disks,
and to study the local environment of these sources.Comment: 6 pages, updated and expanded version of article to appear in
Proceedings of "A Population Explosion: The Nature and Evolution of X-ray
Binaries in Diverse Environments", 28 Oct - 2 Nov, St. Pete Beach, FL; eds.
R.M. Bandyopadhyay, S. Wachter, D. Gelino, C.R. Gelino; AIP Conference
Proceedings Serie
X-Ray Binaries and the Dynamical States of Globular Clusters
We summarize and discuss recent work (Fregeau 2007) that presents the
confluence of three results suggesting that most Galactic globular clusters are
still in the process of core contraction, and have not yet reached the thermal
equilibrium phase driven by binary scattering interactions: that 1) the three
clusters that appear to be overabundant in X-ray binaries per unit encounter
frequency are observationally classified as "core-collapsed," 2) recent
numerical simulations of cluster evolution with primordial binaries show that
structural parameters of clusters in the binary-burning phase agree only with
"core-collapsed" clusters, and 3) a cluster in the binary-burning phase for the
last few Gyr should have about 5 times more dynamically formed X-ray sources
than if it were in the core contraction phase for the same time.Comment: Conference proceedings from "A Population Explosion: The Nature and
Evolution of X-ray Binaries in Diverse Environments," 28 Oct - 2 Nov, St.
Petersburg Beach, FL. 4 page
INTEGRAL and New Classes of High-Mass X-ray Binaries
The gamma-ray observatory INTEGRAL, launched in October 2002, produces a
wealth of discoveries and new results on compact high energy Galactic objects,
nuclear gamma-ray line emission, diffuse line and continuum emission, cosmic
background radiation, AGN and high energy transients. Two important
serendipitous discoveries made by the INTEGRAL mission are new classes of X-ray
binaries, namely the highly-obscured high-mass X-ray binaries, and the
super-giant fast transients. In this paper I will review the current status of
these discoveries.Comment: 3 pages, 1 figure, submitted; Proceedings "The nature and evolution
of X-ray binaries in diverse environments", St Petersburg/FL, USA, 28 Oct -
02 Nov 200
Probing Clumpy Stellar Winds in SFXTs
Quantitative constraints on the wind clumping of massive stars can be
obtained from the study of the hard X-ray variability of SFXTs. In these
systems, a large fraction of the hard X-ray emission is emitted in the form of
flares with typical duration of 3 ksec, frequency of 7 days and luminosity of
ergs/s. Such flares are most probably emitted by the interaction of a
compact object orbiting at R with wind clumps ( g).
The density ratio between the clumps and the inter-clump medium is .
The parameters of the clumps and of the inter-clump medium are in good
agreement with macro-clumping scenario and line-driven instability simulations.Comment: 3 pages, A Population Explosion: The Nature and Evolution of X-ray
Binaries in Diverse Environment
Multiwavelength Studies of X-ray Binaries
Simultaneous multiwavelength studies of X-ray binaries have been remarkably
successful and resulted in improved physical constraints, a new understanding
of the dependence of mass accretion rate on X-ray state, as well as insights on
the time-dependent relationship between disk structure and mass-transfer rate.
I will give some examples of the tremendous gains we have obtained in our
understanding of XRBs by using multiwavelength observations. I will end with an
appeal that while Spitzer cryogens are still available a special effort be put
forth to obtaining coordinated observations including the mid-infrared: Whereas
the optical and near-IR originate as superpositions of the secondary star and
of accretion processes, the mid-IR crucially detects jet synchrotron emission
from NSs that is virtually immeasurable at other wavelengths. A further benefit
of Spitzer observations is that mid-infrared wavelengths can easily penetrate
regions that are heavily obscured. Many X-ray binaries lie in the Galactic
plane and as such are often heavily obscured in the optical by interstellar
extinction. The infrared component of the SED, vital to the study of jets and
dust, can be provided {\it only} by Spitzer; in the X-rays we currently have an
unprecedented six satellites available and in the optical and radio dozens of
ground-based facilities to complement the Spitzer observations.Comment: 5 pages including figures, in conference proceedings A Population
Explosion: The Nature and Evolution of X-ray Binaries in Diverse
Environments, eds. Bandyopadhyay, Wachter, Gelino, & Gelin
The Galactic population of HMXBs as seen with INTEGRAL during its four first years of activity
We collected the parameters (position, absorption, spin, orbital period,
etc..), when known, of all Galactic sources detected by INTEGRAL during its
four first years of activity. We use these parameters to test theoretical
predictions. For example, it is clear that HMXBs tend to be found mostly in the
tangential direction of the Galactic arms, while LMXBs tend to be clustered in
the Galactic bulge. We then focus on HMXBs and present two possible new tools,
in addition to the well-known ``Corbet-diagram'', to distinguish between
Be-HMXBs and Sg-HMXBsComment: 5 pages, 3 figures proceedings of "A population explosion: the nature
and evolution of X-ray binaries in diverse environments", conference held in
St.Petersburg Beach, Florida; R.M.Bandyopadhyay, S.Wachter, D.Gelino,
C.R.Gelino, ed
Beyond Search: Information Literacy, Special Collections, and the First Year
Recent research in information literacy (IL) suggests librarians should shift the emphasis of IL instruction toward higher-level concepts rather than search mechanics. This session describes how the Augustana library drew upon the results of local assessments and national research to re-imagine its first-year learning outcomes so as to focus on higher-level skills and recognize the importance of special collections in teaching IL in the college’s required first-year sequence. We address transforming IL pedagogy throughout the library as well as designing special collections as a hands-on learning laboratory
Counterparts to the Nuclear Bulge X-ray source population
We present an initial matching of the source positions of the Chandra Nuclear
Bulge X-ray sources to the new UKIDSS-GPS near-infrared survey of the Nuclear
Bulge. This task is made difficult by the extremely crowded nature of the
region, despite this, we find candidate counterparts to ~50% of the X-ray
sources. We show that detection in the J-band for a candidate counterpart to an
X-ray source preferentially selects those candidate counterparts in the
foreground whereas candidate counterparts with only detections in the H and
K-bands are more likely to be Nuclear Bulge sources. We discuss the planned
follow-up for these candidate counterparts.Comment: 5 pages, 2 figures, 1 table, published in the proceedings of "A
population Explosion", AIP Conference Proceedings Volume 1010, pp. 117-12
The Nuclear Bulge extinction
We present a new, high resolution (5" per pixel) near-infrared extinction map
of the Nuclear Bulge using data from the UKIDSS-GPS. Using photometry from the
J, H and K-bands we show that the extinction law parameter is also highly
variable in this region on similar scales to the absolute extinction. We show
that only when this extinction law variation is taken into account can the
extinction be measured consistently at different wavelengths.Comment: 3 pages, 2 figures, published in the proceedings of "A population
Explosion", AIP Conference Proceedings Volume 1010, pp. 168-17
Monitoring LMXBs with the Faulkes Telescopes
We have been undertaking a monitoring project of 13 low-mass X-ray binaries
(LMXBs) using FT North since early 2006. The introduction of FT South has
allowed us to extend this monitoring to include 15 southern hemisphere LMXBs.
With new instrumentation, we also intend to expand this monitoring to include
both infrared wavelengths and spectroscopy.Comment: Conference proceedings from 'A Population Explosion: The Nature and
Evolution of X-ray Binaries in Diverse Environments', 28 Oct - 2 Nov, St.
Petersburg Beach, FL. 3 pages, 3 figure
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