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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308803.0, MPI für Astronomie / Publikationen_mpia
G76.188+0.098: a newly born massive binary star
Authors:Comerón, F.; Pasquali, A.; Torra, J.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:Astronomy and Astrophysics
Start Page:553
End Page:559
Audience:Not Specified
Abstract / Description:Context: .We present observations of <ASTROBJ>G76.188+0.098</ASTROBJ>, an object classified in the literature as an ultracompact HII region (UCHIIR) based on its far-infrared and radio continuum characteristics.<BR /> Aims: .To investigate the nature of this object on the basis of the combination of radio observations existing in the literature and the new observations in the near-infrared presented here, with particular attention to the direct detection of the central ionizing source.<BR /> Methods: .Near-infrared narrow-band imaging and low resolution spectroscopy in the 2 mum region.<BR /> Results: .The new observations clearly reveal the central source, which turns out to be a resolved binary system obscured by AK &simeq; 4.4 mag. A general agreement is found between the morphology of the region as outlined by narrow-band, near-infrared imaging, and existing VLA radio continuum maps. Indirect evidence based on the low HeI (2.058 mum) / Brgamma intensity ratio of the compact nebula suggests that the binary system is composed of two stars with spectral types O9 and B0 at a distance of ~2.4 kpc, somewhat closer to the Sun than commonly assumed in the literature.<BR /> Conclusions: .The size of the central cavity of the compact nebula, the low electron densities derived from radio continuum measurements, and the moderate extinction towards the central source by UCHIIR standards suggest that G76.188+0.098 is a very young massive binary observed near the end of the embedded, ultracompact phase, adding one example to the rare cases in which the central source of an ultracompact HII region is detected.
Free Keywords:ISM: individual objects: G76.188+0.098; stars: early-type; binaries: general; HII region
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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