H. Schild

Wind clumping and the wind-wind collision zone in the Wolf-Rayet binary gamma ² Velorum observations at high and low state. XMM-Newton observations at high and low state

We present XMM-Newton observations of γ 2 Velorum (WR 11, WC8+O7.5III, P = 78.53 d), a nearby Wolf-Rayet binary system, at its X-ray high and low states. At high state, emission from a hot collisional plasma dominates from about 1 to 8 keV. At low state, photons between 1 and 4 keV are absorbed. The hot plasma is identified with the shock zone between the winds of the primary Wolf-Rayet star and the secondary O giant. The absorption at low state is interpreted as photoelectric absorption in the Wolf-Rayet wind. This absorption allows us to measure the absorbing column density and to derive a mass loss rate . M = 8 × 10 −6 Myr −1 for the WC8 star. This mass loss rate, in conjunction with a previous Wolf-Rayet wind model, provides evidence for a clumped WR wind. A clumping factor of 16 is required. The X-ray spectra below 1 keV (12 A) show no absorption and are essentially similar in both states. There is a rather clear separation in that emission from a plasma hotter than 5 MK is heavily absorbed in low state while the cooler plasma is not. This cool plasma must come from a much more extended region than the hot material. The Neon abundance in the X-ray emitting material is 2.5 times the solar value. The unexpected detection of C  (25.3 A) and C  (31.6 A) radiative recombination continua at both phases indicates the presence of a cool (∼40 000 K) recombination region located far out in the binary system.We present XMM-Newton observations of 2 Velorum (WR11, WC8+O7.5III, P =78.53 d), a nearby Wolf-Ray binary system, at its X-ray high and low states. At high state, emission from a hot collisional plasma dominates from about 1 to 8 keV. At low state, photons between 1 and 4keV are absorbed. The hot plasma is identified with the shock zone between the winds of the primary Wolf-Rayet star and the secondary O giant. The absorption at low state is interpreted as photoelectric absorption in the Wolf-Rayet wind. This absorption allows us to measure the absorbing column density and to derive a mass loss rate . M =8×10 −6 M⊙yr −1 for the WC8 star. This mass loss rate, in conjunction with a previous Wolf-Rayet wind model, provides evidence for a clumped WR wind. A clumping factor of 16 is required. The X-ray spectra below 1 keV (12 u show no absorption and are essentially similar in both states. There is a rather clear separation in that emission from a plasma hotter than 5MK is heavily absorbed in low state while the cooler plasma is not. This cool plasma must come from a much more extended region than the hot material. The Neon abundance in the X-ray emitting material is 2.5 times the solar value. The unexpected detection of C v (25.3 u and C vi (31.6 u radiative recombination continua at both phases indicates the presence of a cool (�40,000 K) recombination region located far out in the binary system.

High resolution spectroscopy of symbiotic stars - VI. Orbital and stellar parameters for AR Pavonis

We present new dynamical parameters of the AR Pav binary system. Our observations consist of a series of high resolution optical/NIR spectra from which we derive the radial velocity curve of the red giant as well as its rotation velocity. Assuming co-rotation, we determine the stellar radius (130

The H2 structure of OMC-1

R_{\odot}

XMM-Newton X-ray observations of gamma2 Velorum (WC8 + O7.5III)

) of the red giant. Based on this we derive the red giants luminosity and mass (2.0

Circumstellar matter around M-giants in symbiotic binaries: SY Muscae and RW Hydrae ?

M_{\odot}

XMM-Newton Studies of the Wolf-Rayet Colliding-Wind Binaries WR 25 (WN6h+O4f) and WR 11 (WC8+O7.5III)

) as well as the distance of the system (4.9 kpc). The binary mass function finally yields the companions mass (0.75

High resolution spectroscopy of symbiotic stars. V. Orbital and stellar parameters for FG Ser (AS 296)

M_{\odot}

A wind accretion wake in RW Hydrae

) and the binary separation (1.95 AU). We find that the red giant does not fill its Roche lobe. We review the radial velocity data of Thackeray & Hutchings ([CITE]), and compare it with our red giants orbit. We find that their RV curves of the blue absorption system and the permitted emission lines are in anti-phase with the red giant, and that the forbidden emission lines are shifted by a quarter of a period. The blue absorptions and the permitted emission lines are associated with the hot companion but not in a straightforward way. The blue absorption system only tracks the hot components orbital motion whilst it is in front of the red giant, whereas at other phases line blanketing by interbinary material leads to perturbations. We finally present UV light curves based on IUE archive spectra. We clearly detect eclipses in the continuum at all wavelengths. The eclipse light curves are unusual in that they show a slow and gradual decline prior to eclipse which is followed by a sharp increase after eclipse.