Related papers: A new candidate Wolf-Rayet X-ray binary in NGC 253
Aims. What is the origin of the large-amplitude variability in Wolf-Rayet WN8 stars in general and WR123 in particular? A dedicated spectroscopic campaign targets the ten-hour period previously found in the high-precision photometric data…
We describe here results of a photometric time-sequence survey of the globular cluster M3 (NGC 5272), in a search for contact and detached eclipsing binary stars. We have discovered only one likely eclipsing binary and one SX Phe type star…
We report on two XMM-Newton observations performed in 2006 of the luminous low-mass X-ray binary XB1832-330 which is located in the galactic globular cluster NGC 6652 and is probably an ultracompact binary (orbital period less than 1 hour).…
We model the evolution of the selected types of X-ray sources (both with BHs and NSs) for the star formation burst at the Galactic center. For the currently assumed starburst age of 4-7 millions years, our results are consistent with the…
22 GHz water vapor emission was observed toward the central region of the spiral starburst galaxy NGC 253. Monitoring observations with the 100-m telescope at Effelsberg and measurements with the BnC array of the VLA reveal three distinct…
Using simultaneous optical (VLT/FORS2) and X-ray (XMM-Newton) data of NGC 5408, we present the first ever attempt to search for a reverberation signal in an ultraluminous X-ray source (NGC 5408 X-1). The idea is similar to AGN broad line…
The variable gamma-ray source HESS J0632+057 is an excellent candidate for a gamma-ray binary. The putative binary system was discovered as a point-like VHE gamma-ray source by HESS. Later measurements by VERITAS yielding no detection,…
An X-ray flaring source was found near the galaxy NGC 4697. Two flares were seen, separated by four years. The flux increased by a factor of 90 on a timescale of about one minute. Both flares were very brief. There is no optical counterpart…
The Wolf-Rayet (WR) nebula NGC3199 has been suggested to be a bow shock around its central star WR18, presumably a runaway star, because optical images of the nebula show a dominating arc of emission south-west of the star. We present the…
We present a summary of our ongoing efforts to study one of the brightest ultraluminous X-ray source, NGC 1313 X-2. Despite a large coverage in the X-rays, much of the information we have about the source and its environment comes from…
We report the results of an optical campaign carried out by the XMM-Newton Survey Science Centre with the specific goal of identifying the brightest X-ray sources in the XMM-Newton Galactic Plane Survey of Hands et al. (2004). In addition…
We have observed four low-luminosity active galactic nuclei classified as Type 1 LINERs with the X-ray Telescope (XRT) and the UltraViolet-Optical Telescope (UVOT) onboard Swift, in an attempt to clarify the main powering mechanism of this…
In recent years, much studies have focused on determining the origin of the large-scale line-profile and/or photometric patterns of variability displayed by some apparently single Wolf-Rayet stars, with the existence of an unseen…
We present new identifications of infrared counterparts to the population of hard X-ray sources near the Galactic center detected by the Chandra X-ray Observatory. We have confirmed 16 new massive stellar counterparts to the X-ray…
We carry out classification of 4330 X-ray sources in the 2XMMi-DR3 catalog. They are selected under the requirement of being a point source with multiple XMM-Newton observations and at least one detection with the signal-to-noise ratio…
Strongly magnetized, accreting neutron stars show periodic and aperiodic variability over a wide range of time scales. By obtaining spectral and timing information on these different time scales, we can have a closer look into the physics…
The black-hole binary LMC X-3 is known to be variable on time scales of days to years. We investigate X-ray and ultraviolet variability in the system as a function of the 1.7 day binary phase using a 6.4 day observation with the Rossi X-ray…
The Seyfert 1 galaxy NGC 5548 was observed for a week by Chandra using both the HETGS and LETGS spectrometers. In this paper we study the time variability of the continuum radiation. During our observation, the source showed a gradual…
The nature of the hard X-ray source XSSJ12270-4859 is still unclear though it was claimed to be a magnetic Cataclysmic Variable. We here present a broad-band X-ray and gamma ray study based on a recent XMM-Newton observation and archival…
Massive stars are powerful cosmic engines. In the phases immediately preceding core-collapse, massive stars in the Galaxy with $M_i \gtrsim 20$ $M_{\odot}$ may appear as classical Wolf-Rayet (WR) stars. As the final contribution of a…