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Aims. Soft X-ray excesses have been detected in several Be/X-ray binaries and interpreted as the signature of hard X-ray reprocessing in the inner accretion disk. The system XMMU J054134.7-682550, located in the LMC, featured a giant Type II outburst in August 2007. The geometry of this system can be understood by studying the response of the soft excess emission to the hard X-ray pulses. Methods. We have analyzed series of simultaneous observations obtained with XMM-Newton/EPIC-MOS and RXTE/PCA in order to derive spectral and temporal characteristics of the system, before, during and after the giant outburst. Spectral fits were performed and a timing analysis has been carried out. Spectral variability, spin period evolution and energy dependent pulse shapes are analysed. Results. The outburst (L_X = 3* 10^38 erg/s \approx L_EDD) spectrum could be modeled successfully using a cutoff powerlaw, a cold disk emission, a hot blackbody, and a cyclotron absorption line. The magnetic field and magnetospheric radius could be constrained. The thickness of the inner accretion disk is broadened to a width of 75 km. The hot blackbody component features sinusoidal modulations indicating that the bulk of the hard X-ray emission is emitted preferentially along the magnetic equator. The spin period of the pulsar decreased very significantly during the outburst. This is consistent with a variety of neutron star equations of state and indicates a very high accretion rate., 6 pages. Accepted for publication in A&A

We present selected results from an investigation that is currently underway to determine the abundances of light and Fe group elements in early B stars and assess the extent to which contemporary NLTE and LTE models represent their atmospheres. Spectral data of B stars that display ultrasharp lines, obtained with HST, FUSE, and the KPNO Coude Feed Telescope, are compared with computations from TLUSTY/SYNSPEC and SYNTHE. The B stars include the abundance standards ι Her (B3V), HR 1886 (B1V), and HR 1887 (B0.5V).

We have obtained Chandra HRC‐S/LETG spectroscopy of the prototypical supersoft source CAL 83 in the Large Magellanic Cloud. The data reveal a very rich absorption line spectrum from the hot white dwarf photosphere. We have recently completed the analysis of the Chandra spectrum and of an earlier XMM‐Newton RGS spectrum of CAL 83 with new non‐LTE line‐blanketed model atmospheres that explicitly include 74 ions of the 11 most abundant species. We have successfully matched the Chandra and XMM‐Newton spectra, and have thus derived the basic stellar parameters of the hot white dwarf. In particular, we have obtained the first direct spectroscopic evidence that the white dwarf is massive (M > 1M⊙). We also found no spectral signatures of a wind from the white dwarf. These results provide direct support for supersoft sources as likely progenitors of SN Ia.

The study of polarized light is a powerful tool for the determination of magnetic fields in stellar objects. The most used methods are the so-called “photographic” method [1] and Balmer line photopolarimetry [2]. However, in various cases these two methods give different results for the same star. To assess the validity of the interpretation of photopolarimetric measurements of Balmer lines, we have developed a new model of the formation of these lines in a magnetized plasma. This model is based on the Simplified Unified Theory (SUT) for the computation of the line shape [3–5]. We present this model, some numerical results computed with it, and conclusions drawn from consideration of there results [6]. We discuss the prospects for future developments in continuation of this work.