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Institut für Astronomie und Astrophysik

Abteilung Astronomie

Sand 1, D-72076 Tübingen, Germany

Preprint 11e/98


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 80309440, U.S.A.
(3) CASA, University of Colorado, Boulder, CO 80309389, U.S.A.
(4) CASS, University of California, San Diego, La Jolla, CA 92093, U.S.A.

3rd Integral Symposium - The Extreme Universe, in press

Abstract. LMC X-1 and LMC X-3 are the only two black holes that are consistently seen in the soft X-ray state. We present the results from the spectral and temporal analysis of a long (150 ksec) observation of these two objects. The spectra can be well described by a disk black body plus a high energy power-law, which extends to at least 50 keV.
Starting in December 1996 we have also monitored these objects with RXTE in about three to four week intervals. We present the evolution of the spectral parameters of the sources from the first twenty pointings. LMC X-1 has a very stable spectrum and does not exhibit any large scale variability. On the other hand, the appearance of LMC X-3 changes considerably over its 200d 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: xrays; neutron stars; cyclotron lines; magnetic fields

Paper (37k gzip'ed Postscript including figures)

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