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A census of the Wolf–Rayet content in Westerlund 1 from near-infrared imaging and spectroscopy
New NTT/SOFI imaging and spectroscopy of the Wolf-Rayet population in Westerlund 1 are presented. Narrow-band near-IR imaging together with follow up spectroscopy reveals four new Wolf-Rayet stars,Expand
On the massive stellar population of the super star cluster Westerlund 1
We present new spectroscopic and photometric observations of the young Galactic open cluster Westerlund 1 (Wd 1) that reveal a unique population of massive evolved stars. We identify ∼200 clusterExpand
Astrophysical Parameters of LS 2883 and Implications for the PSR B1259-63 Gamma-ray Binary
This research is partially supported by the Spanish MICINN (grants FPA2010-22056-C06-02, AYA2008-06166-C03-01/03, AYA2010-21697-C05-04/05, and CSD2006-70 and FEDER funds); and by the GeneralitatExpand
We report the discovery of an X-ray pulsar in the young, massive Galactic star cluster Westerlund 1. We detected a coherent signal from the brightest X-ray source in the cluster, CXOExpand
The distances to the X-ray binaries LSI +61° 303 and A0535+262
Chevalier & Ilovaisky use Hipparcos data to show that the X-ray binary systems LSI+61° 303 and A0535+262 are a factor of 10 closer (i.e. d ∼ few hundred pc) than previously thought (d ∼ kpc). WeExpand
Intermediate to low-mass stellar content of Westerlund 1
We have analysed near-infrared NTT/SofI observations of the starburst cluster Westerlund 1, which is among the most massive young clusters in the Milky Way. A comparison of colour-magnitude diagramsExpand
On the binary nature of the γ-ray sources AGL J2241+4454 (= MWC 656) and HESS J0632+057 (= MWC 148)
We present optical spectroscopy of MWC 656 and MWC 148, the proposed optical counterparts of the γ -ray sources AGL J2241+4454 and HESS J0632+057, respectively. The main parameters of the Hα emissionExpand
A Be-type star with a black-hole companion
Observations of an accretion disk line mirroring the orbit of MWC 656, the candidate counterpart of the γ-ray source AGL J2241+4454, indicates that a black hole of 3.8 to 6.9 solar masses orbits the star, implying that Be binaries with black-hole companions are difficult to detect in conventional X-ray surveys. Expand
The population of OB supergiants in the starburst cluster Westerlund 1
Context. After leaving the main sequence, massive stars undergo complex evolution, a process that is still poorly understood. With a population of hundreds of OB stars, the starburst clusterExpand
A search for counterparts to massive X-ray binaries using photometric catalogues ,⋆
School of Physics and Astronomy, University of Southampton, Southampton SO17 1BJ, United KingdomReceivedABSTRACTContext.The X-ray andγ-ray observatoryINTEGRAL has discovered large numbers of new hardExpand