Study of the massive O- and WR- stars and their associated winds
Date & Time :
Massive stars are important objects within a galaxy, impacting their environments via their radiation fields and dense, supersonic winds and then via subsequent supernova explosions. Within our own galaxy there are many examples of early type stars, both single objects and binary stars lying in young star clusters. The aim of this thesis is to explore the massive O- and WR- stars and their associated winds in detail using multiwavelength data sets. To accomplish this goal, deep X-ray study of the colliding wind binary WR 25 using long-term (∼16 yrs) archival X-ray data has been carried out. WR 25 is among the very few binary systems with a long orbital period of 208 d which shows the presence of a strong hysteresis effect in its X-ray emission. Moreover, no significant X-ray emission is measured in 10.0−79.0 keV energy range from WR 25 by NuSTAR. We have also investigated a deeply embedded Wolf-Rayet star WR 121a using Chandra and XMM-Newton data. For the first time, phase-locked variations has been seen in its X-ray emission with a period of ∼4.1 d. The X-ray spectrum of WR 121a below 10.0 keV presents the typical features of an optically thin thermal plasma emission at high temperature (above 30 Million K). The current study suggested that it belongs to the category of massive colliding wind binaries. In a similar line, the X-ray emission from an O+O binary HD 93205 showed typical features of a wind interacting system. There is another class of massive binaries which form dust in the hydrogen-poor atmospheres. To understand dust formation, a particle accelerating and dust making system WR 125 has been monitored in infra-red and X-ray wavelengths. In the present analysis, we have clearly found the periastron passage of this extremely long period binary (>28.3 years). This signature in seen in the X-ray data where the X-ray flux decreases sharply. Further, enhanced emission in the NIR K-band assures this feature indicating another dust formation episode in WR 125 close to the periastron passage. A brief description of each chapter of my thesis is presented in this report.