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NGC6231: X-ray Properties of the Early-Type Star Population
Sana, H.; Nazé, Yaël; Gosset, Eric et al.
2007In Massive Stars in Interactive Binaries
 

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Abstract :
[en] Based on a deep XMM-Newton observation of the young open cluster NGC6231, we derive the main X-ray properties of its early-type star population. Among the 610 X-ray sources detected in the field, 42 are associated with early-type stars. We investigate their L[SUB]X[/SUB]/L[SUB]bol[/SUB] relationship and confirm the clear dichotomy between O- and B-type stars. The cut-off line between the two behaviours occurs at L[SUB]bol[/SUB] ~ 10[SUP]38[/SUP] erg s[SUP]-1[/SUP] as previously proposed by Berghöfer et al. (1997). The distinction between single and binary stars is not clear cut, except for the colliding wind system HD152248. The X-ray detected B-stars in NGC6231 appear to be more luminous than predicted from the Berghöfer et al. relation. Though this suggests a bimodal distribution of the B-star X-ray emission, we caution however that these results might be biased by detection limits. Finally we investigate the X-ray variability of the detected sources and we find that about 40% of the X-ray emitters in the field of view present consistent signs of variability in the EPIC instruments. This fraction is much larger than previously thought. About one third of the early-type star population, either singles or binaries, further show variability. These variations do not seem to be exclusively related to binarity and could thus not be systematically interpreted in the framework of a wind-wind collision phenomenon.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Sana, H.
Nazé, Yaël  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales
Gosset, Eric ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Rauw, Grégor  ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE) - Sciences spatiales
Sung, H.
Vreux, Jean-Marie ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO)
Language :
English
Title :
NGC6231: X-ray Properties of the Early-Type Star Population
Publication date :
2007
Audience :
International
Main work title :
Massive Stars in Interactive Binaries
Pages :
109
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