Reference : A multi-epoch XMM-Newton campaign on the core of the massive Cygnus OB2 association
Scientific journals : Article
Physical, chemical, mathematical & earth Sciences : Space science, astronomy & astrophysics
A multi-epoch XMM-Newton campaign on the core of the massive Cygnus OB2 association
Rauw, Grégor mailto [Université de Liège - ULg > Département d'astrophys., géophysique et océanographie (AGO) > Sciences spatiales]
Astronomy and Astrophysics
EDP Sciences
Yes (verified by ORBi)
Les Ulis
[en] open clusters and associations: individual: Cyg OB2 ; stars: early-type ; stars: pre-main sequence ; stars: individual: Cyg OB2 #12 ; X-rays: stars
[en] Context. Cyg OB2 is one of the most massive associations of O-type stars in our Galaxy. Despite the large interstellar reddening towards Cyg OB2, many studies, spanning a wide range of wavelengths, have been conducted to more clearly understand this association. X-ray observations provide a powerful tool to overcome the effect of interstellar absorption and study the most energetic processes associated with the stars in Cyg OB2. <BR /> Aims: We analyse XMM-Newton data to investigate the X-ray and UV properties of massive O-type stars as well as low-mass pre-main sequence stars in Cyg OB2. <BR /> Methods: We obtained six XMM-Newton observations of the core of Cyg OB2. In our analysis, we pay particular attention to the variability of the X-ray bright OB stars, especially the luminous blue variable candidate Cyg OB2 #12. <BR /> Results: We find that X-ray variability is quite common among the stars in Cyg OB2. Whilst short-term variations are restricted mostly to low-mass pre-main sequence stars, one third of the OB stars display long-term variations. The X-ray flux of Cyg OB2 #12 varies by 37%, over timescales from days to years, whilst its mean log L[SUB]X[/SUB]/L[SUB]bol[/SUB] amounts to - 6.10. <BR /> Conclusions: These properties suggest that Cyg OB2 #12 is either an interacting-wind system or displays a magnetically confined wind. Two other X-ray bright O-type stars (MT91 516 and CPR2002 A11) display variations that suggest they are interacting wind binary systems. 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).Full Table 2 and Table 4 are only available in electronic form at the CDS via anonymous ftp to ( or via <A href=""></A>

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