Article (Scientific journals)
Phase resolved X-ray spectroscopy of HDE 228766: Probing the wind of an extreme Of+/WNLha star
Rauw, Grégor; Mahy, Laurent; Nazé, Yaël et al.
2014In Astronomy and Astrophysics, 566, p. 107
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Keywords :
binaries: spectroscopic; stars: early-type; stars: mass-loss; stars: winds; outflows; X-rays: stars
Abstract :
[en] Context. HDE 228766 is a very massive binary system hosting a secondary component, which is probably in an intermediate evolutionary stage between an Of supergiant and an WN star. The wind of this star collides with the wind of its O8 II companion, leading to relatively strong X-ray emission. <BR /> Aims: Measuring the orbital variations of the line-of-sight absorption toward the X-ray emission from the wind-wind interaction zone yields information on the wind densities of both stars. <BR /> Methods: X-ray spectra have been collected at three key orbital phases to probe the winds of both stars. Optical photometry has been gathered to set constraints on the orbital inclination of the system. <BR /> Results: The X-ray spectra reveal prominent variations of the intervening column density toward the X-ray emission zone, which are in line with the expectations for a wind-wind collision. We use a toy model to set constraints on the stellar wind parameters by attempting to reproduce the observed variations of the relative fluxes and wind optical depths at 1 keV. <BR /> Conclusions: The lack of strong optical eclipses sets an upper limit of ~ 68° on the orbital inclination. The analysis of the variations of the X-ray spectra suggests an inclination in the range 54-61° and indicates that the secondary wind momentum ratio exceeds that of the primary by at least a factor 5. Our models further suggest that the bulk of the X-ray emission arises from the innermost region of the wind interaction zone, which is from a region whose outer radius, as measured from the secondary star, lies between 0.5 and 1.5 times the orbital separation. Based on observations collected with XMM-Newton, an ESA science mission with instruments and contributions directly funded by ESA member states and the USA (NASA), and on data collected at the San Pedro Mártir observatory (Mexico).
Research center :
LiSRI - Liège Space Research Institute - ULiège
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Rauw, Grégor  ;  Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Mahy, Laurent ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astroph. extragalactique et observations spatiales (AEOS)
Nazé, Yaël  ;  Université de Liège - ULiège > Groupe d'astrophysique des hautes énergies (GAPHE)
Eenens, P.;  Departamento de Astronomia, Universidad de Guanajuato, Apartado 144, 36000 Guanajuato, GTO, Mexico
Manfroid, Jean  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)
Flores, C. A.;  Departamento de Astronomia, Universidad de Guanajuato, Apartado 144, 36000 Guanajuato, GTO, Mexico)
Language :
English
Title :
Phase resolved X-ray spectroscopy of HDE 228766: Probing the wind of an extreme Of+/WNLha star
Publication date :
01 June 2014
Journal title :
Astronomy and Astrophysics
ISSN :
0004-6361
eISSN :
1432-0746
Publisher :
EDP Sciences, Les Ulis, France
Volume :
566
Pages :
107
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 31 July 2014

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