Related papers: Soft X-ray spectral variability of AM Herculis

Her X-1, one of the brightest and best studied X-ray binaries, shows a cyclotron resonant scattering feature (CRSF) near 37 keV. This makes it an ideal target for detailed study with the Nuclear Spectroscopic Telescope Array (NuSTAR),…

During the low optical brightness states of AM Herculis systems (polars) when accretion has declined to a very low value, the underlying magnetic white dwarf photosphere can be modelled without the complication of thermal bremstrahlung and…

Blazars are the most luminous and variable AGNs, and thus excellent probes of accretion and emission processes close to the central engine. We focus on PKS 1510-089 ($z=0.36$), one of the brightest gamma-ray sources in the Fermi LAT…

RS Cae is the third target in our series of XMM-Newton observations of soft X-ray-dominated polars. Our observational campaign aims to better understand and describe the multiwavelength data, the physical properties of the system…

We report the discovery of a new catacysmic variable system, RXJ051541+0104.6. The optical spectrum has a blue continuum with superposed H~I and He~I and II emission lines. The soft X-ray spectrum is well fit with a 50~eV black body. The…

We present X-ray data of RX J1802.1+1804 obtained by ASCA. Although it shows a clear orbital intensity modulation with an amplitude of nearly 100% below 0.5 keV in ROSAT data, the ASCA light curves are nearly flat except for a possible dip…

We present ROSAT All-Sky Survey and ROSAT pointed observations (PSPC and HRI) of a complete sample of 113 bright soft X-ray AGN selected from the ROSAT Bright Source Catalog. We compare these observations in order to search for extreme…

We present spatial, temporal and spectral analyses of ROSAT Position Sensitive Proportional Counter (PSPC) observations of the infrared loud quasar IRAS 13349+2438. IRAS 13349+2438 is the archetypal highly-polarized radio-quiet QSO and has…

We have analysed the soft X-ray emission from the nuclear source of the nearby spiral galaxy M81, using the available data collected with ROSAT, ASCA, BeppoSAX and Chandra. The source flux is highly variable, showing (sometimes dramatic: a…

We present spatially-resolved spectroscopy of the galaxy cluster Abell S1101, also known as Sersic 159-03, with Chandra, XMM-Newton and ROSAT, and investigate the presence of soft X-ray excess emission above the contribution from the hot…

We present phase-resolved spectroscopy of the bright, eclipsing polar HU Aqr obtained with high time (~30sec) and spectral (1.6 A) resolution when the system was in a high accretion state. The trailed spectrograms reveal clearly the…

eROSITA (extended ROentgen Survey with an Imaging Telescope Array) instrument onboard the Russian-German `Spectrum-Roentgen-Gamma' (SRG) mission observed the Her X-1/HZ Her binary system in multiple scans over the source during the first…

We present RXTE observations of the eclipsing X-ray binary Hercules X-1 conducted during an anomalous low state. Data reduction reveals a light curve over 2.7 orbital cycles remarkably similar to optical and UV light curves which are…

We make a systematic analysis of the XMM-Newton X-ray spectra of intermediate polars (IPs) and find that, contrary to the traditional picture, most show a soft blackbody component. We compare the results with those from AM Her stars and…

We present Keck II spectroscopy of an optical mHz quasi-periodic oscillations (QPOs) in the lightcurve of the X-ray pulsar binary Her X-1. In the power spectrum it appears as `peaked noise', with a coherency $\sim$2, a central frequency of…

Using archival ASCA observations of TT Arietis, X-ray energy spectra and power spectra of the intensity time series are presented for the first time. The energy spectra are well-fitted by a two continuum plasma emission model with…

We present the analysis of the X-ray data of the young active star HD35850 obtained with ASCA and ROSAT. Our main goal was to see if there is a difference in the elemental abundances of active stars between young and more evolved objects. A…

The Imaging X-ray Polarimetry Explorer (IXPE) measured with high significance the X-ray polarization of the brightest Z-source Scorpius X-1, resulting in the nominal 2-8 keV energy band in a polarization degree of 1.0(0.2)% and a…

Long uninterrupted observations of the X-ray binary system Her X-1 were performed with the Mikhail Pavlinsky ART-XC telescope of the Spectrum-R\"ontgen-Gamma (SRG) X-ray Observatory in the 4--25 keV energy range with a total exposure of…

I have collected all available ROSAT observations of VY Scl stars including those during the all-sky survey to investigate the presence, strength and spectrum of soft X-ray emission (0.1-2.4 keV) of this group of nova-like variables. A…