We report on the analysis of the Chandra-ACIS data of O, B, and WR stars in the young association Cyg OB2. X-ray spectra of 49 O-stars, 54 B-stars, and 3 WR-stars are analyzed and for the brighter sources, the epoch dependence of the X-ray fluxes is investigated. The O-stars in Cyg OB2 follow a well-defined scaling relation between their X-ray and

Context. Classical novae (CNe) have recently been reported to represent the major class of supersoft X-ray sources (SSSs) in the central region of our neighbour galaxy M 31. Aims: We carried out a dedicated monitoring of the M 31 central region with XMM-Newton and Chandra in order to find SSS counterparts of CNe, determine the duration of their SSS

Optical novae have recently been identified as the major class of supersoft X-ray sources in M 31 based on ROSAT and early XMM-Newton and Chandra observations. This paper reports on a search for X-ray counterparts of optical novae in M 31 based on archival Chandra HRC-I and ACIS-I as well as XMM-Newton observations of the galaxy center region

NGC 2808 was observed with the Chandra X-ray Observatory and the Chandra Advanced CCD Imaging Spectrometer-Imager (ACIS-I) at its focus on 2007 June 19-21 (28 months after the XMM-Newton observation) for two distinct exposures of 46 and 11 kiloseconds (ks). (1 data file).

Compact binary millisecond pulsars with main-sequence donors, often referred to as "redbacks," constitute the long-sought link between low-mass X-ray binaries and millisecond radio pulsars and offer a unique probe of the interaction between pulsar winds and accretion flows. We present a systematic study of eight nearby redbacks, using more than 100

A recent merger of two supermassive black holes (BH) or the presence of a second active BH in the galactic nucleus are two of the main scenarios proposed to explain the X-shaped morphology observed in X-shaped radio galaxies. We test these scenarios by studying the BH mass, radio and optical luminosity, starburst history and dynamic age of radio