Related papers: Diffuse X-ray emission in the Cygnus OB2 associati…
The accretion onto the black hole in the system HDE 226868/Cygnus X-1 is powered by the strong line driven stellar wind of the O-type donor star. We study the X-ray properties of the stellar wind in the hard state of Cyg X-1 as determined…
We present almost-simultaneous detections of Cygnus X-1 in the radio and mm regimes, obtained during the low/hard X-ray state. The source displays a flat spectrum between 2 and 220 GHz, with a spectral index flatter than 0.15 (3sigma).…
We have analyzed a Chandra HETGS spectrum of the Galactic black hole Cygnus X-1, obtained at a source flux which is approximately twice that commonly observed in its persistent low-intensity, spectrally-hard state. We find a myriad of…
We analyze the optical, UV, and X-ray microlensing variability of the lensed quasar SDSS J0924+0219 using six epochs of Chandra data in two energy bands (spanning 0.4-8.0 keV, or 1-20 keV in the quasar rest frame), 10 epochs of F275W…
The Galactic diffuse soft gamma-ray (30-800 keV) emission has been measured from the Galactic Center by the HIREGS balloon-borne germanium spectrometer to determine the spectral characteristics and origin of the emission. The resulting…
We present e-MERLIN 21 cm (L-band) observations of single luminous OB stars in the Cygnus OB2 association, from the COBRaS Legacy programme. The radio observations potentially offer the most straightforward, least model-dependent,…
We have used the transition disk model to fit the simultaneous broad band ($2-500$ keV) spectrum of Cygnus X-1 from OSSE and Ginga observations. In this model, the spectrum is produced by saturated Comptonization within the inner region of…
We present here the analysis of X-rays point sources detected in several observations available in the XMM-Newton public archive. We focused, in particular, on energies below 1 keV, which are of particular relevance to the understanding of…
Aims: We characterize individual and ensemble properties of X-ray flares from stars in the CygOB2 and ONC star-forming regions. Method: We analyzed X-ray lightcurves of 1003 CygOB2 sources observed with Chandra for 100 ksec and of 1616 ONC…
Dust grains scatter X-ray light through small angles, producing a diffuse halo image around bright X-ray point sources situated behind a large amount of interstellar material. We present analytic solutions to the integral for the dust…
X-ray mosaics of the Large Magellanic Cloud (LMC) taken with the ROSAT Position Sensitive Proportional Counter (PSPC) have revealed extensive diffuse X-ray emission, indicative of hot >= 10^6 K gas associated with this irregular galaxy on…
Observations of the hot X-ray emitting interstellar medium in the Milky Way are important for studying the stellar feedback and understanding the formation and evolution of galaxies. We present measurements of the soft X-ray background…
Orbital variability has been found in the X-ray hardness of the black hole candidate Cygnus X-1 during the soft/high X-ray state using light curves provided by the Rossi X-ray Timing Explorer's All Sky Monitor. We are able to set broad…
Stellar winds of massive stars are known to be driven by line absorption of UV photons, a mechanism which is prone to instabilities, causing the wind to be clumpy. The clumpy structure hampers wind mass-loss estimates, limiting our…
We analyze orbital solutions for 48 massive multiple-star systems in the Cygnus OB2 Association, 23 of which are newly presented here, to find that the observed distribution of orbital periods is approximately uniform in log P for P<45 d,…
The origins of all extra-solar cosmic rays -- both the ultra high-energy and lower energy Galactic variety -- remain unclear. It has been argued that the large scale shocks and turbulence induced by the multiple interacting supersonic winds…
We report the X-ray population study in the giant molecular cloud Sagittarius B2 (SgrB2). More than a dozen of X-ray cloud members (and candidates) are discovered with Chandra. Two bright X-ray sources are located near Sgr B2 Main, the most…
The ubiquitous diffuse soft (1/4 keV) X-ray background was one of the earliest discoveries of X-ray astronomy. At least some of the emission may arise from charge exchange between solar wind ions and neutral atoms in the heliosphere, but no…
The spectrum of any star viewed through a sufficient quantity of diffuse interstellar material reveals a number of absorption features collectively called diffuse interstellar bands (DIBs). The first DIBs were reported 90 years ago, and…
We present the results of a J, H, and K photometric variability survey of the central 0.78 square degrees of the young OB association Cygnus OB2. We used data observed with the Wide-Field CAMera at the United Kingdom Infrared Telescope in…