Докладчик: Jeewan Ch. Pandey (ARIES, Nainital, India)
Название доклада: “X-ray emission from massive colliding wind binaries”
Краткое содержание доклада:
In this talk, I will present an analysis of long-term X-ray and optical observations of massive Wolf-Rayet binaries: WR25, WR47 and WR139. Using archival data from observations with the XMM-Newton and the Swift observatories spanning over ~10 years, we show that WR25 is a periodic variable in X-rays with a period of 208 +/- 3 days. X-ray light curves in the 0.5-10.0 keV energy band show phase-locked variability, where the flux increased by a factor of ~2 from minimum to maximum, being maximum near periastron passage. The light curve in the soft energy band (0.5-2.0 keV) shows two minima indicating the presence of two eclipses. However, the light curve in the hard energy band (2.0-10.0 keV) shows only one minimum during the apastron passage. The X-ray spectra of all three WR stars were explained by a two-temperatures plasma model. The cool temeprature was constant at 0.628+/-0.008 and could be due to the small scale shocks in a radiation driven outflow. However, the high temperature plasma could be due to the collision of winds. For WR25, the column density varied with the orbital phase and was found to be maximum after the periastron passage, when the WR star is in front of O star. The abundances of WR25 were found to be non-solar. Optical V-band data of WR25 also show the phase-locked variability, being at maximum near periastron passage. The results based on the present analysis indicate that all three WR binaries are colliding wind binaries where the presence of soft X-rays is attributed to individual components; however, hard X-rays are due to the collision of winds.