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X-ray evidence for wind-wind collision in the Wolf-Rayet binary V444 Cygni

Published online by Cambridge University Press:  25 May 2016

Jun Yokogawa ,
Katsuji Koyama ,
Yoshitomo Maeda  and
Steve L. Skinner
Jun Yokogawa
Affiliation:
Department of Physics, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
Katsuji Koyama
Affiliation:
Department of Physics, Kyoto University, Sakyo-ku, Kyoto, 606-8502, Japan
Yoshitomo Maeda
Affiliation:
Department of Astronomy & Astrophysics, Pennsylvania State Univ., University Park, PA 16802-6305, USA
Steve L. Skinner
Affiliation:
JILA, University of Colorado, Boulder, CO 80309-0440, USA

Abstract

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We present results on the eclipsing binary V444 Cyg (WN5+O6) with the X-ray satellite ASCA. The observations were performed at orbital phases 0.0, 0.25 and 0.5 (the 06 star is in front at phase 0.5 and vice versa at phase 0.0). Two-temperature plasma model could reproduce X-ray spectra in each phase. The temperature of the soft component is lower (kT ≃ 0.6 keV), which is attributed to the individual O6/WN5 stars. The temperature of the hard component is higher (kT ≃ 2 keV), which exhibited phase-related time-variabilities in absorption column NH and luminosity LX; NH was maximal at phase 0.0 while LX was minimal at phase 0.5. These variabilities are consistent with the scenario that X-rays are emitted from plasma heated-up by wind-wind collision near the surface of the O6 star.

Type
Part 3. Interaction of Wolf-Rayet stars and other hot massive stars with their environment: colliding winds and ring nebulae
Information
Symposium - International Astronomical Union , Volume 193: Wolf-Rayet Phenomena in Massive Stars and Starburst Galaxies , 1999 , pp. 398 - 399
Copyright
Copyright © Astronomical Society of the Pacific 1999 

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