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          Institute: MPI für Astronomie     Collection: Publikationen_mpia     Display Documents

ID: 308624.0, MPI für Astronomie / Publikationen_mpia
The birth-cluster of the galactic luminous blue variable WRA 751
Authors:Pasquali, A.; Comerón, F.; Nota, A.
Date of Publication (YYYY-MM-DD):2006
Journal Abbrev.:Astronomy and Astrophysics
Start Page:589
End Page:596
Audience:Not Specified
Abstract / Description:We present the results of NTT/VLT UBV imaging of a 260 arcmin2 region containing the Galactic Luminous Blue Variable WRA 751, in search for its birth-cluster, i.e. a cluster of young and massive stars spatially and physically associated with it. On the basis of the classical reddening-free parameter Q, we have identified a sample of 24 early-type stars with colours typical of spectral types earlier than B3. Interestingly, these stars are clustered within a radius of 1' from WRA 751, corresponding to about 1% of the imaged field. These stars tightly distribute around (B-V) ≃ 1.67, which in turn defines a mean extinction AV ≃ 6.1 mag. The 5 brighter (V ≤ 16.2) and bluer (Q ≤ -0.9) stars of the sample have been subsequently observed with FORS1 and classified as 3 late O- and 2 early B-stars. The absence of stars earlier than O8 indicates an age of the cluster older than 4 Myr, although it could be due to an incomplete sampling of the upper end of the main sequence. Nevertheless, the detection of OB stars of class I certainly indicates an age of a few million years. At an assumed distance of 6 kpc, we estimate a cluster radius of 3.4 pc and a total mass of 2.2 × 103 Mo. Our discovery is only the second known instance of a Galactic Luminous Blue Variable associated with its birth-cluster.
Free Keywords:stars: early-type; stars: evolution; stars: fundamental parameters; stars: Hertzsprung-Russell (HR); and C-M diagrams
External Publication Status:published
Document Type:Article
Communicated by:N. N.
Affiliations:MPI für Astronomie
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