Reference : XMM-Newton observation of the enigmatic object WR 46
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
http://hdl.handle.net/2268/56760
XMM-Newton observation of the enigmatic object WR 46
English
Gosset, Eric mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)]
De Becker, Michaël mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Département d'astrophys., géophysique et océanographie (AGO)]
Nazé, Yaël mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique observationnelle (sol et espace) >]
Carpano, S. [Research and Scientific Support Department, ESTEC/ESA, PO Box 299, 2200, AG Noordwijk, The Netherlands; European Space Agency, XMM-Newton Science Operations Centre, ESAC, Apartado 78, 28691, Madrid, Spain]
Rauw, Grégor mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales]
Antokhin, I. I. [Sternberg Astronomical Institute, Moscow University, Universitetskij Prospect 13, Moscow, 119992, Russia]
Vreux, Jean-Marie mailto [Université de Liège - ULg > > Département d'astrophys., géophysique et océanographie (AGO)]
Pollock, A. M. T. [European Space Agency, XMM-Newton Science Operations Centre, ESAC, Apartado 78, 28691, Madrid, Spain]
1-Mar-2011
Astronomy and Astrophysics
EDP Sciences
527
66
Yes (verified by ORBi)
International
0004-6361
1432-0746
Les Ulis
France
[en] stars: individual: WR 46 ; stars: Wolf-Rayet ; X-rays: stars
[en] Aims: To further investigate the nature of the enigmatic object WR 46 and better understand the X-ray emission in massive stars and in their evolved descendants, we observed this variable object for more than two of its supposed cycles. The X-ray emission characteristics are appropriate indicators of the difference between a genuine Wolf-Rayet star and a specimen of a super soft source as sometimes suggested in the literature. The X-ray emission analysis might contribute to understanding the origin of the emitting plasma (intrinsically shocked wind, magnetically confined wind, colliding winds, and accretion onto a white dwarf or a more compact object) and to substantiating the decision about the exact nature of the star. <BR /> Methods: The X-ray observations of WR 46 were performed with the XMM-Newton facility over an effective exposure time of about 70 ks. <BR /> Results: Both the X-ray luminosity of WR 46, typical of a Wolf-Rayet star, and the existence of a relatively hard component (including the Fe-K line) rule out the possibility that WR 46 could be classified as a super soft source, and instead favour the Wolf-Rayet hypothesis. The X-ray emission of the star turns out to be variable below 0.5 keV but constant at higher energies. The soft variability is associated to the Wolf-Rayet wind, but revealing its deep origin necessitates additional investigations. It is the first time that such a variability is reported for a Wolf-Rayet star. Indeed, the X-ray emission exhibits a single-wave variation with a typical timescale of 7.9 h which could be related to the period observed in the visible domain both in radial velocities (single-wave) and in photometry (double-wave). The global X-ray emission seems to be dominated by lines and is closely reproduced by a three-temperature, optically thin, thermal plasma model. The derived values are 0.1-0.2 keV, 0.6 keV, and ~4 keV, which indicates that a wide range of temperatures is actually present. The soft emission part could be related to a shocked-wind phenomenon. The hard tail of the spectrum cannot presently be explained by such an intrinsic phenomenon as a shocked wind and instead suggests there is a wind-wind collision zone, as does the relatively high L[SUB]X[/SUB]/L[SUB]bol[/SUB] ratio. We argue that this scenario implies the existence of an object farther away from the WN3 object than any possible companion in an orbit related to the short periodicity. Based on observations with XMM-Newton, an ESA Science Mission with instruments and contributions directly funded by ESA Member States and the USA (NASA).
Researchers
http://hdl.handle.net/2268/56760
10.1051/0004-6361/200912510
http://cdsads.u-strasbg.fr/abs/2011A%26A...527A..66G

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