2005ApJ...627..926J -
Astrophys. J., 627, 926-932 (2005/July-2)
X-ray spectroscopy of candidate ultracompact X-ray binaries.
JUETT A.M. and CHAKRABARTY D.
Abstract (from CDS):
We present high-resolution spectroscopy of the neutron star/low-mass X-ray binaries (LMXBs) 4U 1850-087 and 4U 0513-40 as part of our continuing study of known and candidate ultracompact binaries. The LMXB 4U 1850-087 is one of four systems in which we had previously inferred an unusual Ne/O ratio in the absorption along the line of sight, most likely from material local to the binaries. However, our recent Chandra X-Ray Observatory LETGS spectrum of 4U 1850-087 finds a Ne/O ratio by number of 0.22±0.05, smaller than previously measured and consistent with the expected interstellar value. We propose that variations in the Ne/O ratio due to source variability, as previously observed in these sources, can explain the difference between the low- and high-resolution spectral results for 4U 1850-087. Our XMM-Newton RGS observation of 4U 0513-40 also shows no unusual abundance ratios in the absorption along the line of sight. We also present spectral results from a third candidate ultracompact binary, 4U 1822-000, whose spectrum is well fit by an absorbed power-law + blackbody model with absorption consistent with the expected interstellar value. Finally, we present the nondetection of a fourth candidate ultracompact binary, 4U 1905+000, with an upper limit on the source luminosity of <1x1032 ergs/s. Using archival data, we show that the source has entered an extended quiescent state.
Abstract Copyright:
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Journal keyword(s):
Stars: Binaries: Close - Stars: Individual: Alphanumeric: 4U 0513-40 - Stars: Individual: Alphanumeric: 4U 1822-000 - Stars: Individual: Alphanumeric: 4U 1850-087 - Stars: Individual: Alphanumeric: 4U 1905+000 (read: 2S 1905+00) - X-Rays: Binaries
Simbad objects:
12
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