Search Publications
Coronal Modulation in the Ultra-fast Rotator LO Peg
Pandey, Jeewan Chandra; Singh, Gurpreet; Yadava, Umesh
We present coronal imaging of the ultra-fast rotator, LO Peg, using the X-ray observations from XMM-Newton. The X-ray light curves show one strong flare at the end of observation, as reported in an earlier study. On removal of flaring events, the quiescent state light curve shows rotational modulations, which are modelled using a maximum likelihoo…
X-raying the wind-wind collisions in HD 168112 and HD 167971
Blomme, R.; Nazé, Y.; Rauw, G. +1 more
The O-type long-period binary HD 168112 and triple HD 167971 star systems have been known for several decades for their non-thermal synchrotron radio emission. This emission arises from relativistic electrons accelerated in the hydrodynamic shocks of the wind collisions in these systems. Such wind collisions are expected to produce a strong X-ray …
Results from the 2009 campaign on WR 140
Williams, Peredur
The archetypal Wolf-Rayet + O star colliding-wind binary WR 140 has a very elliptical orbit, so that maximum interaction between the WR and O winds, and the most rapid changes in configuration, occur around periastron passage. To exploit this laboratory for studying wind-collision and high-energy phenomena, several groups mounted campaigns to obse…
X-rays, clumping and wind structures
Ignace, Richard; Oskinova, Lidia; Hamann, Wolf-Rainer +1 more
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 absorption, which greatly simplifies the radiative transfer treatment. The small and large scale structures i…
The X-ray emission of the colliding wind binary V444 Cyg
Nazé, Yaël; De Becker, Michaël; Fauchez, Thomas
This paper presents the analysis of six XMM-Newton observations of the colliding wind system V444 Cyg. Unlike what one might have expected at first, it appears that the O star wind most probably dominates the WN wind: the bow shock is wide open, with the hard X-ray emission arising close to the WN star. An important radiative braking could partly …
The XMM-Newton view of the X-ray spectrum of WR140 across periastron passage
De Becker, Michaël; Pittard, Julian M.; Williams, Peredur. +1 more
An XMM-Newton campaign dedicated to the study of the X-ray emission of the colliding wind massive binary WR140 across its 2009 periastron passage has been undertaken. The high quality EPIC spectra revealed a strong phase-locked variability both in flux and in spectral shape. The observed variations are consistently explained by the varying emissio…
Multiwavelength study of the intriguing massive star CPD--59 2629 (Tr 16-22)
Gamen, R.; Combi, J. A.; Romero, G. E. +8 more
We report preliminary results of a multi-wavelength (radio-optical-X-ray) study of the massive star CPD -59 2629 (Tr 16-22) in the Carina Nebula (NGC 3372). This star has historically shown a large X-ray excess (log L_{X}/L_{bol} < -6 or even larger), which is one order of magnitude larger than expected from single massive O-type stars. A colli…
General X-ray properties of hot, massive stars
Nazé, Yaël
The recent X-ray observatories have not yet provided a large survey comparable (in sky coverage) to that based upon the ROSAT All-Sky Survey (RASS). However, two limited surveys exist : the 2XMM catalog for XMM-Newton (294 OB stars detected) and the Carina large-scale survey from Chandra (129 OB stars detected). Medium-resolution (CCD) spectra wer…
The X-ray emission of the WR+O binary WR 79
Sana, Hugues; Nazé, Yaël; Gosset, Eric +1 more
In the framework of our multiwavelength study of the open cluster NGC 6231, we observed the colliding-wind WR+O binary WR 79 at six different epochs with the XMM-Newton observatory. These pointings offer the possibility to study the X-ray spectrum of WR 79 and its possible variability. Our results are briefly discussed and compared with the X-ray …
A Multiwavelength Study of the Runaway Binaries HD 14633 and HD 15137
De Becker, Michaël; Boyajian, Tabetha S.; McSwain, M. Virginia +1 more
The runaway O-type binaries HD 14633 and HD 15137 were likely ejected from the cluster of their birth by supernovae explosions in close binaries. Here we present recent optical spectra to update the orbital solutions of the binaries and study the physical parameters of the O star primaries. We also present XMM-Newton observations of both systems t…