000002015 001__ 2015
000002015 005__ 20160701171657.0
000002015 0247_ $$2DOI$$a10.1051/0004-6361:20054602
000002015 037__ $$aASTROimport-172
000002015 100__ $$aBlomme, R.
000002015 245__ $$aNon-thermal radio emission from O-type stars. II. HD 167971
000002015 260__ $$c2007
000002015 520__ $$aHD 167971 is a triple system consisting of a 3.3-day eclipsing binary (O5-8 V + O5-8 V) and an O8 supergiant. It is also a well known non-thermal radio emitter. We observed the radio emission of HD 167971 with the Very Large Array (VLA) and the Australia Telescope Compact Array (ATCA). By combining these data with VLA archive observations we constructed a radio lightcurve covering a 20-yr time-range. We searched for, but failed to find, the 3.3-day spectroscopic period of the binary in the radio data. This could be due to the absence of intrinsic synchrotron radiation in the colliding-wind region between the two components of the eclipsing binary, or due to the large amount of free-free absorption that blocks the synchrotron radiation. We are able to explain many of the observed characteristics of the radio data if the non-thermal emission is produced in a colliding-wind region between the supergiant and the combined winds of the binary. Furthermore, if the system is gravitationally bound, the orbital motion occurs over a period of ~20 years or longer, as suggested by the long-term variability in the radio data. We argue that the variability is due to the free-free absorption that changes with orbital phase or may also in part be due to changes in separation, should the orbit be eccentric. Table A.1 is only available in electronic form at http://www.aanda.org 
000002015 700__ $$a De Becker, M.
000002015 700__ $$a Runacres, M. C.
000002015 700__ $$a van Loo, S.
000002015 700__ $$a Setia Gunawan, D. Y. A.
000002015 773__ $$c701-708$$i2$$pAstronomy and Astrophysics$$v464$$y2007
000002015 85642 $$ahttp://esoads.eso.org/abs/2007A%26A...464..701B
000002015 905__ $$apublished in
000002015 980__ $$aREFERD