Article (Scientific journals)
The massive star binary fraction in young open clusters - II. NGC6611 (Eagle Nebula)
Sana, H.; Gosset, Eric; Evans, C. J.
2009In Monthly Notices of the Royal Astronomical Society, 400, p. 1479-1492
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Keywords :
binaries: close; binaries: spectroscopic; stars: early-type; open clusters and associations: individual: NGC6611
Abstract :
[en] Based on a set of over 100 medium- to high-resolution optical spectra collected from 2003 to 2009, we investigate the properties of the O-type star population in NGC6611 in the core of the Eagle Nebula (M16). Using a much more extended data set than previously available, we revise the spectral classification and multiplicity status of the nine O-type stars in our sample. We confirm two suspected binaries and derive the first SB2 orbital solutions for two systems. We further report that two other objects are displaying a composite spectrum, suggesting possible long-period binaries. Our analysis is supported by a set of Monte Carlo simulations, allowing us to estimate the detection biases of our campaign and showing that the latter do not affect our conclusions. The absolute minimal binary fraction in our sample is f[SUB]min[/SUB] = 0.44 but could be as high as 0.67 if all the binary candidates are confirmed. As in NGC6231 (see Paper I), up to 75 per cent of the O star population in NGC6611 are found in an O+OB system, thus implicitly excluding random pairing from a classical IMF as a process to describe the companion association in massive binaries. No statistical difference could be further identified in the binary fraction, mass-ratio and period distributions between NGC6231 and NGC 6611, despite the difference in age and environment of the two clusters.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Sana, H.;  European Southern Observatory, Alonso de Cordova 1307, Casilla 19001, Santiago 19, Chile ; Sterrenkundig Instituut Anton Pannekoek, Universiteit van Amsterdam, Postbus 94249, 1098 XH Amsterdam, the Netherlands
Gosset, Eric ;  Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Groupe d'astrophysique des hautes énergies (GAPHE)
Evans, C. J.;  UK Astronomy Technology Centre, Royal Observatory Edinburgh, Blackford Hill, Edinburgh EH9 3HJ
Language :
English
Title :
The massive star binary fraction in young open clusters - II. NGC6611 (Eagle Nebula)
Publication date :
01 December 2009
Journal title :
Monthly Notices of the Royal Astronomical Society
ISSN :
0035-8711
eISSN :
1365-2966
Publisher :
Blackwell Publishing, Oxford, United Kingdom
Volume :
400
Pages :
1479-1492
Peer reviewed :
Peer Reviewed verified by ORBi
Commentary :
http://de.arxiv.org/abs/0909.0486
Available on ORBi :
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