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X-ray variability in V444 Cygni: evidence for colliding winds

Published online by Cambridge University Press:  07 August 2017

M.F. Corcoran ,
I.R. Stevens ,
A.M.T. Pollock ,
J.H. Swank ,
S.N. Shore  and
G.L. Rawley
M.F. Corcoran
Affiliation:
1 Universities Space Research Association, Code 668, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.
I.R. Stevens
Affiliation:
2 Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, U.K.
A.M.T. Pollock
Affiliation:
3 Computer & Scientific Co., Ltd., 34 Westwood Rd., Sheffield S11 7EY, U.K.
J.H. Swank
Affiliation:
4 Laboratory for High Energy Astrophysics, Code 666, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, U.S.A.
S.N. Shore
Affiliation:
5 Department of Physics and Astronomy, Indiana University at South Bend 1700 Mishawaka Avenue, South Bend, IN 46634, U.S.A
G.L. Rawley
Affiliation:
6Applied Research Corporation, 8201 Corporate Dr., Landover, MD 20785, U.S.A.

Abstract

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Phase-resolved observations of the soft X-ray flux from the WN5+O6 binary V444 Cyg (WR139) have been obtained by ROSAT. The objective of these observations were: (1) to compare our results with previous observations made with the IPC (Moffat et at. 1982); (2) to explore the phase dependence of the X-ray variations; and (3) to look for evidence of the generation of X-rays from colliding winds in the system. ROSAT observed V444 Cygni with the PSPC five separate times, for a total integration time of about 20 ksec. Figure 1 shows the phase-binned light-curve along with archival IPC data. The observed X-ray variability can be modeled as a wind eclipse of an X-ray source by the WR wind. If most of the X-rays from the system are produced in a shock-heated region of wind interaction between the two stars, then the shocked gas has a large physical extent (r ≈ 140RW R) if the observed variability is produced solely by the eclipse of the region by the WR wind. However, since the O star makes a significant contribution to the total X-ray flux from the system, the actual size of the shocked interaction region is probably much smaller.

Type
Session IV - poster summaries
Information
Symposium - International Astronomical Union , Volume 163: Wolf-Rayet Stars: Binaries, Colliding Winds, Evolution , 1995 , pp. 250
Copyright
Copyright © Kluwer 1995 

References

Moffat, A.F.J., Firmani, C., McLean, I.S., Seggewiss, W. 1982, in: de Loore, C.W.H. & Willis, A. (eds.), Wolf-Rayet Stars: Observations, Physics, Evolution, Proc. IAU Symp. No. 99 (Dordrecht: Reidel), p. 577 Google Scholar