1,586 research outputs found
The X-ray Properties of M101 ULX-1 = CXOKM101 J140332.74+542102
We report our analysis of X-ray data on M101 ULX-1, concentrating on high
state Chandra and XMM-Newton observations. We find that the high state of M101
ULX-1 may have a preferred recurrence timescale. If so, the underlying clock
may have periods around 160 or 190 days, or possibly around 45 days. Its
short-term variations resemble those of X-ray binaries at high accretion rate.
If this analogy is correct, we infer that the accretor is a 20-40 Msun object.
This is consistent with our spectral analysis of the high state spectra of M101
ULX-1, from which we find no evidence for an extreme (> 10^40 ergs/s)
luminosity. We present our interpretation in the framework of a high mass X-ray
binary system consisting of a B supergiant mass donor and a large stellar-mass
black hole.Comment: 23 pages, 7 figures, accepted for publication in the Astrophysical
Journa
Global Hot Gas in and around the Galaxy
The hot interstellar medium traces the stellar feedback and its role in
regulating the eco-system of the Galaxy. I review recent progress in
understanding the medium, based largely on X-ray absorption line spectroscopy,
complemented by X-ray emission and far-UV OVI absorption measurements. These
observations enable us for the first time to characterize the global spatial,
thermal, chemical, and kinematic properties of the medium. The results are
generally consistent with what have been inferred from X-ray imaging of nearby
galaxies similar to the Galaxy. It is clear that diffuse soft X-ray
emitting/absorbing gas with a characteristic temperature of K
resides primarily in and around the Galactic disk and bulge. In the solar
neighborhood, for example, this gas has a characteristic vertical scale height
of kpc. This conclusion does not exclude the presence of a
larger-scale, probably much hotter, and lower density circum-Galactic hot
medium, which is required to explain observations of various high-velocity
clouds. This hot medium may be a natural product of the stellar feedback in the
context of the galaxy formation and evolution.Comment: 11 pages, invited talk in the workshop "The Local Bubble and Beyond
II
A Catalog of Galaxy Clusters Observed by XMM-Newton
Aims: We present a uniform catalog of the images and radial profiles of the
temperature, abundance, and brightness for 70 clusters of galaxies observed by
XMM-Newton.
Methods: We use a new "first principles" approach to the modeling and removal
of the background components; the quiescent particle background, the cosmic
diffuse emission, the soft proton contamination, and the solar wind charge
exchange emission. Each of the background components demonstrate significant
spectral variability, several have spatial distributions that are not described
by the photon vignetting function, and all except for the cosmic diffuse
emission are temporally variable. Because these backgrounds strongly affect the
analysis of low surface brightness objects, we provide a detailed description
our methods of identification, characterization, and removal.
Results: We have applied these methods to a large collection of XMM-Newton
observations of clusters of galaxies and present the resulting catalog. We find
significant systematic differences between the Chandra and XMM-Newton
temperatures.Comment: Accepted for publication in A&A, 55 pages with 42 figure
DISCOVERY OF X-RAY EMISSION FROM SUPERNOVA 1970G WITH CHANDRA: FILLING THE VOID BETWEEN SUPERNOVAE AND SUPERNOVA REMNANTS
We report the discovery of X-ray emission from SN 1970G in M101, 35 yr after its outburst, using deep X-ray imaging with the Chundra X-Ray Observatory. The Chandra ACIS spectrum shows that the emission is soft (52 keV) and characteristic of the reverse-shock region. The X-ray luminosity, Lo,,, = (1.1 3 0.2) x lo3# ergs s-1, is likely caused by the interaction of the supernova shock with dense circumstellar matter. If the material was deposited by the stellar wind from the progenitor, a mass-loss rate of M = (2.6 ? 0.4) x M, yr-I (v,/lO km s-I) is inferred. Utilizing the high-resolution Chandra ACIS data of SN 1970G and its environment, we reconstruct the X-ray lightcurve from previous ROSAT HRI, PSPC, and XMM-Newton EPIC observations, and find a best-fit linear rate of decline of L cc t-# with index s = 2.7 t 0.9 over a period of -20-35 yr after the outburst. As the oldest supernova detected in X-rays, SN 1970G allows, for the first time, direct observation of the transition from a supenova to its supernova remnant phase
The EPIC-MOS Particle-Induced Background Spectrum
We have developed a method for constructing a spectrum of the particle-induced instrumental background of the XMM-Newton EPIC MOS detectors that can be used for observations of the diffuse background and extended sources that fill a significant fraction of the instrument field of view. The strength and spectrum of the particle-induced background, that is, the background due to the interaction of particles with the detector and the detector surroundings, is temporally variable as well as spatially variable over individual chips. Our method uses a combination of the filter-wheel-closed data and a database of unexposed-region data to construct a spectrum of the "quiescent" background. We show that, using this method of background subtraction, the differences between independent observations of the same region of "blank sky" are consistent with the statistical uncertainties except when there is clear evidence of solar wind charge exchange emission. We use the blank sky observations to show that contamination by SWCX emission is a strong function of the solar wind proton flux, and that observations through the flanks of the magnetosheath appear to be contaminated only at much higher solar wind fluxes. We have also developed a spectral model of the residual soft proton flares, which allows their effects to be removed to a substantial degree during spectral fitting
The Chandra M10l Megasecond: Diffuse Emission
Because MIOl is nearly face-on, it provides an excellent laboratory in which to study the distribution of X-ray emitting gas in a typical late-type spiral galaxy. We obtained a Chandra observation with a cumulative exposure of roughly 1 Ms to study the diffuse X-ray emission in MlOl. The bulk of the X-ray emission is correlated with the star formation traced by the FUV emission. The global FUV/Xray correlation is non-linear (the X-ray surface brightness is roughly proportional to the square root of the FUV surface brightness) and the small-scale correlation is poor, probably due to the delay between the FUV emission and the X-ray production ill star-forming regions. The X-ray emission contains only minor contributions from unresolved stars (approximates less than 3%), unresolved X-ray point sources (approximates less than 4%), and individual supernova remnants (approximates 3%). The global spectrum of the diffuse emission can be reasonably well fitted with a three component thermal model, but the fitted temperatures are not unique; many distributions of emission measure can produce the same temperatures when observed with the current CCD energy resolution. The spectrum of the diffuse emission depends on the environment; regions with higher X-ray surface brightnesses have relatively stronger hard components, but there is no significant evidence that the temperatures of the emitting components increase with surface brightness
Modeling the Local Warm/Hot Bubble
In this paper we review the modeling of the Local Bubble (LB) with special
emphasis on the progress we have made since the last major conference "The
Local Bubble and Beyond (I)" held in Garching in 1997. Since then new insight
was gained into the possible origin of the LB, with a moving group crossing its
volume during the last 10 - 15 Myr being most likely responsible for creating a
local cavity filled with hot recombining gas. Numerical high resolution 3D
simulations of a supernova driven inhomogeneous interstellar medium show that
we can reproduce both the extension of the LB and the OVI column density in
absorption measured with FUSE for a LB age of 13.5 - 14.5 Myr. We further
demonstrate that the LB evolves like an ordinary superbubble expanding into a
density stratified medium by comparing analytical 2D Kompaneets solutions to
NaI contours, representing the extension of the local cavity. These results
suggest that LB blow-out into the Milky Way halo has occurred roughly 5 Myr
ago.Comment: 8 pages, 3 figures, to appear in the proceedings of "The Local Bubble
and Beyond II", Philadelphia, USA, April 21-24, 200
The X-ray Emitting Components towards l = 111 deg: The Local Hot Bubble and Beyond
We have obtained an XMM-Newton spectrum of the diffuse X-ray emission towards (l, b) = (111.14,1.11), a line of sight with a relatively simple distribution of absorbing clouds; > 9 x 10(exp 19)/sq cm at R>170 pc, a 6 x 10(exp 21)/sq cm molecular cloud at 2.5-3.3 kpc, and a total column of 1.2 x 10(exp 22)/sq cm. We find that the analysis of the XMM-Newton spectrum in conjunction with the RASS spectral energy distribution for the same direction requires three thermal components to be well fit: a "standard" Local Hot Bubble component with kT = 0.089, a component beyond the molecular cloud with kT = 0.59, and a component before the molecular cloud with kT = 0.21. The strength of the O VII 0.56 keV line from the Local Hot Bubble, 2.1+/-0.7 photons/sq cm/s/sr, is consistent with other recent measures. The 0.21 keV component has an emission measure of 0.0022+/-0.0006 pc and is not localized save as diffuse emission within the Galactic plane; it is the best candidate for a pervasive hot medium. The spatial separation of the approx. 0.2 keV component from the approx. 0.6 keV component suggests that the spectral decompositions of the emission from late-type spiral disks found in the literature do represent real temperature components rather than reflecting more complex temperature distributions
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