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Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany

Preprint Kc/98

RXTE Observations of LMC X-1 and LMC X-3

J. Wilms(1), M.A. Nowak(2), J.B. Dove(3), K. Pottschmidt(1), W.A. Heindl(4), M.C. Begelman(2), R. Staubert(1)

(1)Institut für Astronomie und Astrophysik, Astronomie, Universität Tübingen, Waldhäuser Str. 64, D-72076 Tübingen, Germany
(2)JILA, University of Colorado, Boulder, CO 80309-440, U.S.A.
(3)CASA, University of Colorado, Boulder, CO 80309-389, U.S.A.
(4)CASS, University of California, San Diego, La Jolla, CA 92093, U.S.A.

1999, Highlights in X-ray Astronomy, ed. B. Aschenbach, MPE Report, in press

Abstract. Of all known persistent stellar-mass black hole candidates, only LMC X-1 and LMC X-3 consistently show spectra that are dominated by a soft, thermal component. We present results from long (170 ksec) Rossi X-ray Timing Explorer (RXTE) observations of LMC X-1 and LMC X-3 made in 1996 December. The spectra can be described by a multicolor disk blackbody plus an additional high-energy power-law. Even though the spectra are very soft (Gamma ~ 2.5), RXTE detected a significant signal from LMC X-3 up to energies of 50 keV, the hardest energy at which the object was ever detected.
Focusing on LMC X-3, we present results from the first year of an ongoing monitoring campaign with RXTE which started in 1997 January. We show that the appearance of the object changes considerably over its ~200 d long cycle. This variability can either be explained by periodic changes in the mass transfer rate or by a precessing accretion disk analogous to Her X-1.

Key words: -

Paper (89k gzip'ed Postscript including figures)

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Jürgen Barnstedt (barnstedt AT astro.uni-tuebingen.de)
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