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Astronomy & Astrophysics manuscript no. 17043 c ESO 2011 May 11, 2011

Summary: Astronomy & Astrophysics manuscript no. 17043 c ESO 2011
May 11, 2011
The VLT-FLAMES Tarantula Survey III: A very massive star in
apparent isolation from the massive cluster R136
Joachim M. Bestenlehner1, Jorick S. Vink1, G. Gršafener1, F. Najarro2, C. J. Evans3, N. Bastian4,5, A. Z. Bonanos6,
E. Bressert5,7,8, P. A. Crowther9, E. Doran9, K. Friedrich10, V. HŽenault-Brunet11, A. Herrero12,13, A. de Koter14,15,
N. Langer10, D. J. Lennon16, J. MaŽiz ApellŽaniz17, H. Sana14, I. Soszynski18, and W. D. Taylor11
(Affiliations can be found after the references)
Received 7 April 2011 / Accepted 2 May 2011
VFTS 682 is located in an active star-forming region, at a projected distance of 29 pc from the young massive cluster R136 in the Tarantula Nebula
of the Large Magellanic Cloud. It was previously reported as a candidate young stellar object, and more recently spectroscopically revealed as a
hydrogen-rich Wolf-Rayet (WN5h) star. Our aim is to obtain the stellar properties, such as its intrinsic luminosity, and to investigate the origin
of VFTS 682. To this purpose, we model optical spectra from the VLT-FLAMES Tarantula Survey with the non-LTE stellar atmosphere code
cmfgen, as well as the spectral energy distribution from complementary optical and infrared photometry. We find the extinction properties to be
highly peculiar (RV 4.7), and obtain a surprisingly high luminosity log(L/L) = 6.5 ± 0.2, corresponding to a present-day mass of 150M.
The high effective temperature of 52.2 ± 2.5kK might be explained by chemically homogeneous evolution ­ suggested to be the key process in
the path towards long gamma-ray bursts. Lightcurves of the object show variability at the 10% level on a timescale of years. Such changes are
unprecedented for classical Wolf-Rayet stars, and are more reminiscent of Luminous Blue Variables. Finally, we discuss two possibilities for the
origin of VFTS 682: (i) the star either formed in situ, which would have profound implications for the formation mechanism of massive stars, or


Source: Armagh Observatory
Armagh Observatory Meteorology Databank


Collections: Geosciences; Physics