Simulations of observations with the Optical Monitor of the X-ray Multi-Mirror Satellite

in Astronomy and Astrophysics. Supplement Series (2000), 145

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric ... [more ▼]

This paper addresses the question of the observations to be performed with the Optical Monitor (OM) of the X-ray Multi-Mirror Satellite (XMM) under several aspects. First, we discuss XMM-OM's photometric system and its colour transformations towards the standard U BV system. Second, we establish a set of procedures to determine the temperature and the amount of interstellar absorption affecting the observed stars. Last, we address the possibility of isolating quasars in multidimensional colour diagrams based on the XMM-OM filter set. [less ▲]

The Interacting Early-Type Binary BD +40°4220 (V729 Cyg): Modeling the Colliding Winds Region

in Astrophysical Journal (1999), 517

We present an analysis of an extensive set of spectroscopic observations of the mysterious early-type binary BD +40 deg4220. A new orbital solution is derived from the radial velocities of the absorption ... [more ▼]

We present an analysis of an extensive set of spectroscopic observations of the mysterious early-type binary BD +40 deg4220. A new orbital solution is derived from the radial velocities of the absorption lines. We confirm that the secondary star is highly overluminous for its mass. The absorption lines of both components display phase-locked profile variations, with some of the secondary's lines going into emission between phi=0.20 and phi=0.55. A detailed investigation of the profile variability of the He II lambda4686 emission line reveals that the pattern of variability of this line is very stable. We show that part of the He II lambda4686 emission is produced in the wind interaction region between the stars. Most of the emission lines in the visual spectrum of BD +40 deg4220 display variations that are reminiscent of those observed on the He II lambda4686 line, pointing toward a similar origin. We present numerical simulations of emission-line profiles in a colliding winds binary, showing that an important part of the variability observed in BD +40 deg4220 can be explained by a colliding winds phenomenon. The properties of the wind interaction region can be accounted for if we assume that the secondary star is an evolved object, most probably some kind of Ofpe/WN9 transition star, with a mass loss rate of ~5.5x10^-6 M_solar yr^-1. We finally discuss the fundamental parameters of the binary, concluding that mass transfer must have played a crucial role in the evolution of this system. [less ▲]

New observational results on the colliding wind WR+O binary WR 30a

in Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies (1999)

Line profile variability in the spectrum of the O(f) supergiant HD 192639

in Astronomy and Astrophysics (1998), 335

We report the results of a medium-resolution spectroscopic investigation of the O(f) supergiant HD 192639. Particular attention is paid to the He {ii}\ lambda 4686 line. This line displays strong profile ... [more ▼]

We report the results of a medium-resolution spectroscopic investigation of the O(f) supergiant HD 192639. Particular attention is paid to the He {ii}\ lambda 4686 line. This line displays strong profile variability on time scales of a few days, changing from a P-Cygni profile with a double-peaked emission component to a pure blue-shifted emission line. It appears that the variability of most of the absorption lines present in our spectra is correlated to the deformation of the He {ii}\ lambda 4686 line and arises probably from a large scale structure in the low-velocity part of the stellar wind rather than from a photospheric phenomenon. We find that the time scale of the variability could be consistent with the estimated rotational period of HD 192639. Based on observations collected at the Observatoire de Haute Provence, France. [less ▲]

X-Ray Spectroscopy with XMM: A New Powerful Tool to Determine Fundamental Parameters of Early-type Stars

(1998)

Not Available

Search for Interacting Winds in the WN7 + O Binary WR 22

in Revista Mexicana de Astronomia y Astrofisica Conference Series (1996, December 01)

We present new spectroscopic observations of the He I Lambda5876 line in WR22 which were obtained around periastron. These data show strong line profile variability. We use recently determined orbital ... [more ▼]

We present new spectroscopic observations of the He I Lambda5876 line in WR22 which were obtained around periastron. These data show strong line profile variability. We use recently determined orbital elements of WR22 to discuss the possibility of tidal interactions or of a colliding wind phenomenon affecting the outer parts of the Wolf-Rayet atmosphere. [less ▲]

WR22: the most massive Wolf-Rayet star ever weighed.

in Astronomy and Astrophysics (1996), 306

The results of an extensive spectroscopic campaign on the eclipsing binary WR22 are presented. A new radial velocity curve is deduced for the WN7 component, allowing us to improve the parameters of the ... [more ▼]

The results of an extensive spectroscopic campaign on the eclipsing binary WR22 are presented. A new radial velocity curve is deduced for the WN7 component, allowing us to improve the parameters of the orbit, formerly determined on the basis of photographic spectra. The high signal-to-noise ratio of our data also allows the detection of some weak absorption lines which, for the first time, can definitely be attributed to the companion. A study of their radial velocities gives a mass ratio of m_WR_/m_O_=2.78 leading to a minimum mass of 72M[SUB]sun[/SUB]_ for the WN7 star. The companion can be classified as a "late O" (O6.5-O8.5) star with a luminosity ratio of the system q=L_WR_^y^/L_O_^y^ at 5500A of about 8. The exceptionally high mass of the WN7 star and its high hydrogen mass-fraction suggest that WR22 is at the beginning of its Wolf-Rayet evolution. As a matter of fact, with such a high mass, WR22 most probably is still a hydrogen burning object. Therefore, the WN7 component is much closer to a main sequence O star with a "Wolf-Rayet clothing" than to the other members of the Wolf-Rayet family, which are rather highly evolved He-burning descendants of massive progenitors. [less ▲]

WR 134 line-profile variability : preliminary results of the 1994 campaign

in Vreux, J.-M.; Detal, Alain; Fraipont-Caro, Denise (Eds.) et al Wolf-Rayet stars in the framework of stellar evolution (1996)

Not Available

A new orbital solution for the WNL binary system WR12

in Liege International Astrophysical Colloquia (1996)

Not Available

Line-profile variablity in the spectrum of WR22 around periastron: binary interaction or intrinsic variability ?

in Liege International Astrophysical Colloquia (1996)

Not Available