16,026 research outputs found
Observations of Binary and Single Wolf-Rayet Stars with XMM-Newton and Chandra
We present an overview of recent X-ray observations of Wolf-Rayet (WR) stars
with XMM-Newton and Chandra. A new XMM spectrum of the nearby WN8 + OB binary
WR 147 shows hard absorbed X-ray emission, including the Fe K-alpha line
complex, characteristic of colliding wind shock sources. In contrast, sensitive
observations of four of the closest known single WC (carbon-rich) WR stars have
yielded only non-detections. These results tentatively suggest that single WC
stars are X-ray quiet. The presence of a companion may thus be an essential
factor in elevating the X-ray emission of WC + OB stars to detectable levels.Comment: To appear in conf. proceedings: Close Binaries in the 21st Century -
New Opportunities and Challenges, eds. A. Gimenez, E. Guinan, P. Niarchos, S.
Rucinski; Astrophys. and Space Sci. (special issue), 2006. 4 pages, 2 figure
Passive instrumentation and stimuli generation for Saturn IB equipment checkout. Volume I - Summary technical report Final technical report, 26 Jun. 1965 - 31 May 1966
Passive instrumentation and stimuli generation for Saturn IB equipment checkout - nondestructive testin
A Rich Population of X-ray Emitting Wolf-Rayet Stars in the Galactic Starburst Cluster Westerlund 1
Recent optical and IR studies have revealed that the heavily-reddened
starburst cluster Westerlund 1 (Wd 1) contains at least 22 Wolf-Rayet (WR)
stars, comprising the richest WR population of any galactic cluster. We present
results of a senstive Chandra X-ray observation of Wd 1 which detected 12 of
the 22 known WR stars and the mysterious emission line star W9. The fraction of
detected WN stars is nearly identical to that of WC stars. The WN stars WR-A
and WR-B as well as W9 are exceptionally luminous in X-rays and have similar
hard heavily-absorbed spectra with strong Si XIII and S XV emission lines. The
luminous high-temperature X-ray emission of these three stars is characteristic
of colliding wind binary systems but their binary status remains to be
determined. Spectral fits of the X-ray bright sources WR-A and W9 with
isothermal plane-parallel shock models require high absorption column densities
log N = 22.56 (cm) and yield characteristic shock temperatures
kT_shock ~ 3 keV (T ~ 35 MK).Comment: ApJL, 2006, in press (3 figures, 1 table
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