HEAD 2003 Meeting
Session 17. X-ray Binaries III
Poster, Sunday-Wednesday, March 23, 2003, Duration of Meeting

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[17.33] XTE J1739-302: a new kind of transient?

D. M. Smith (U. C. Berkeley), W. A. Heindl (U. C. San Diego), T. E. Harrison (New Mexico State University), J. H. Swank, C. B. Markwardt (NASA/Goddard)

XTE J1739-302 has been seen in at least five very brief outbursts by the Rossi X-ray Timing Explorer. Although it is located only two degrees from the Galactic Center and has a high x-ray absorption column, a Chandra observation in quiescence shows that its counterpart is a bright, highly reddened star much closer than the Galactic bulge. A K-band spectrum of this star suggests that it is an O supergiant without emission lines from an equatorial wind. The x-ray spectrum in outburst is similar to that of x-ray pulsars, very hard below 20 keV and rolling off rapidly above that energy, and is unlike any spectrum produced by black-hole binaries. The spectrum in quiescence is similarly hard. Pulsations with a period shorter than 300 s have been ruled out in outburst for amplitudes greater than 2% at 99% confidence. A search for longer periods is still in progress.

The typical duration of the outbursts is constrained to be more than a few hours but less than a few days, making them significantly shorter than the outbursts of Be/NS binaries. We will discuss the status of observations of this system and possible interpretations of its nature. XTE J1739-302 resides squarely in the most heavily-observed part of the x-ray sky yet was not discovered until 1997 due to the brevity of its outbursts; it therefore seems plausible that many such systems wait to be discovered elsewhere in the Galaxy.

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Bulletin of the American Astronomical Society, 35#2
© 2003. The American Astronomical Soceity.