Related papers: X-ray Emission from Isolated Be Stars
We study the influence of X-ray radiation on the wind parameters of O stars. For this purpose we use our own NLTE wind code. The X-ray emission (assumed to be generated in wind shocks) is treated as an input quantity. We study its influence…
X-ray emission is ubiquitous among massive stars. In the last decade, X-ray observations revolutionized our perception of stellar winds but opened a Pandora's box of urgent problems. X-rays penetrating stellar winds suffer mainly continuum…
Massive stars are known X-ray emitters and those belonging to the Be category are no exception. One type of X-ray emission even appears specific to that category, the gamma Cas phenomenon. Its actual incidence has been particularly…
Since Be stars belong to the high velocity tail of a single B star velocity distribution, the appearance of the Be phenomenon must be independent of the stellar mass. In the present paper we show that the shape of the distribution of the…
Massive runaway stars produce bow shocks through the interaction of their winds with the interstellar medium, with the prospect for particle acceleration by the shocks. These objects are consequently candidates for non-thermal emission. Our…
We present the results of a ROSAT Position Sensitive Proportional Counter observation of the variable radio star \ls. The source has a power law spectrum with photon index 1.1 +/- 0.3 and a luminosity of 5.9 x 10^{33} erg/s in the 0.1 -2.4…
Using observations from Chandra, Swift and XMM-Newton, we investigate the high-energy properties of all known (18) Be+sdO systems as well as 7 additional Be binaries suspected to harbour stripped stars. The observed X-ray properties are…
Young O stars are strong, hard, and variable X-ray sources, properties which strongly affect their circumstellar and galactic environments. After ~1 Myr, these stars settle down to become steady sources of soft X-rays. I use high-resolution…
The Be stars display variable optical emission lines originating in the circumstellar disc. Here we analyse high resolution spectroscopic observations of Be stars and the distance between the peaks of H-alpha, H-beta, and H-gamma emission…
Some early-type stars are detectable radio emitters; their spectra can present both thermal and non-thermal contributions. Here I review the public radio data on OB stars, focusing on the non-thermal sources. The analysis of the statistical…
We present a comparative study of the circumstellar disks in Be/X-ray binaries and isolated Be stars based upon the H-alpha emission line. From this comparison it follows that the overall structure of the disks in the Be/X-ray binaries is…
Be X-ray binaries are among the best known transient high-energy sources. Their outbursts are commonly classified into a simple scheme of 'normal' and 'giant' outbursts, but a closer look shows that actual outbursts do not always follow…
B[e] stars are among the most peculiar objects in the sky. This spectral type, characterised by allowed and forbidden emission lines, and a large infrared excess, does not represent an homogenous class of objects, but instead, a mix of…
I discuss the empirical properties of diffuse X-ray emitting gas in the halos of both nearby starburst galaxies and normal spiral galaxies, based on high resolution X-ray spectral imaging with the Chandra X-ray Observatory. Diffuse thermal…
We present a comprehensive study of X-ray emission and wind properties of massive magnetic early B-type stars. Dedicated XMM-Newton observations were obtained for three stars xi1 CMa, V2052 Oph, and zeta Cas. We report the first detection…
We review some of the ways that X-ray observations provide unique information on radio galaxies. Thermal bremsstrahlung X-ray emission provides detailed data on ambient densities and temperatures. These parameters in turn can be used for…
The characteristics of the various types of B[e] stars are discussed and compared with those of classical Be stars. Both groups of stars are characterized by the presence of emission lines in their spectra, in particular of hydrogen.…
Wind-blown bubbles, from those around massive O and Wolf-Rayet stars, to superbubbles around OB associations and galactic winds in starburst galaxies, have a dominant role in determining the structure of the Interstellar Medium. X-ray…
In the era of Chandra and XMM-Newton, the detection (or nondetection) of diffuse and/or point-like X-ray sources within planetary nebulae (PNe) yields important, unique insight into PN shaping processes. Diffuse X-ray sources, whether due…
Planetary nebulae (PNe) are an exciting addition to the zoo of X-ray sources. Recent Chandra and XMM-Newton observations have detected diffuse X-ray emission from shocked fast winds in PN interiors as well as bow-shocks of fast collimated…