Related papers: Soft X-ray emission of VY Scl stars during optical…

In a recent ROSAT observation, taken during its optical low state, we found that the VY Scl star V751 Cyg was a highly luminous source of soft X-rays. The ROSAT HRI count rate of V751 Cyg was a factor of 10-20 higher than upper limits…

Four VY Scl-type nova-like systems were observed in X-rays both during the low and the high optical states. They are BZ Cam, MV Lyr, TT Ari, and V794 Aql. Using archival ROSAT, Swift and SUZAKU observations we found that the X-ray flux for…

Four VY Scl-type nova-like systems were observed in X-rays during both the low and the high optical states. We examined Chandra, ROSAT, Swift and Suzaku archival observations of BZ Cam, MV Lyr, TT Ari, and V794 Aql. The X-ray flux of BZ Cam…

The ROSAT mission gave us the unique possibility to study the galactic interstellar medium by ``shadowing'' observations on arcmin angular resolution level. The high sensitivity of the ROSAT PSPC in combination with the large field of view…

We summarize our optical monitoring program of VY Scl stars with the SMARTS telescopes, and triggered X-ray as well as optical observations after/during state transitions of V504 Cen and VY Scl.

We investigate the ROSAT X-ray properties of V Sge, which has been proposed to be related to supersoft X-ray binaries. During optical bright states, V Sge is a faint hard X-ray source, while during optical faint states (V >=12 mag), V Sge…

We have observed V751 Cyg with the ROSAT HRI during its recent optical low state and clearly detect it at a count rate of 0.015 cts/s. The X-ray intensity is a factor of ~20 higher than the upper limit obtained with the ROSAT PSPC during…

We have analysed 350 pointed and serendipitous observations of 108 different classical and recurrent novae in outburst and in quiescence, contained in the ROSAT archive. One aim was to search for super-soft X-ray sources and we found only 3…

Decades of astrophysical observations have convincingly shown that soft X-ray (SXR; ~0.1--10 keV) emission provides unique diagnostics for the high temperature plasmas observed in solar flares and active regions. SXR observations critical…

We have searched the entire ROSAT archive for useful observations to study X-ray emission from Galactic planetary nebulae (PNs). The search yields a sample of 63 PNs, which we call the ROSAT PN sample. About 20-25% of this sample show X-ray…

We describe the highly variable X-ray and UV emission of V458 Vul (Nova Vul 2007), observed by Swift between 1 and 422 days after outburst. Initially bright only in the UV, V458 Vul became a variable hard X-ray source due to optically thin…

We present the results of soft X-ray studies of the classical nova V2491 Cygni using the Suzaku observatory. On day 29 after outburst, a soft X-ray component with a peak at ~0.5 keV has appeared, which is tantalising evidence for the…

Observations of cooling neutron stars allow to measure photospheric radii and to constrain the equation of state of nuclear matter at high densities. In this paper we concentrate on neutron stars, which show thermal (photospheric) X-ray…

We present a consistent model for the UV and supersoft X-ray emission from the symbiotic nova SMC3 (=RX J0048.4-7332). Following the present picture of symbiotic stars, the model consists of radiation from a hot star and an emission nebula…

We use the ROSAT public data archive to study the X-ray emission of a sample of supposedly single A0-F6 spectral type stars from the Bright Star Catalogue. We detected X-ray emission from 19 A and 33 F-type stars. However, our results are…

Super-Soft-Source (SSS) X-ray spectra are blackbody-like spectra with effective temperatures ~3-7x10^5 K and luminosities of 10^{35-38} erg/s. SSS grating spectra display atmospheric absorption lines. Radiation transport atmosphere models…

A wide variety of solar system bodies are now known to radiate in the soft x-ray energy (<5 keV) regime. These include planets (Earth, Jupiter, Venus, Saturn, Mars): bodies having thick atmospheres, with or without intrinsic magnetic field;…

The study of soft X-ray emission of 38 X-ray selected galaxy clusters observed by ROSAT PSPC indicates that the soft excess phenomenon may be a common occurrence in galaxy clusters. Excess soft X-ray radiation, above the contribution from…

The optical identification of large number of X-ray sources such as those from the ROSAT All-Sky Survey is challenging with conventional spectroscopic follow-up observations. We investigate two ROSAT All-Sky Survey fields of size 10 * 10…

BeppoSAX detected luminous 0.2-2.0 keV supersoft X-ray emission from the recurrent nova U Sco ~19-20 days after the peak of the optical outburst in February 1999. U Sco is the first recurrent nova to be observed during a luminous supersoft…