Astronomy and Astrophysics – Astrophysics – Solar and Stellar Astrophysics
Scientific paper
2009-09-03
MNRAS, 2009, 400, 524-530
Astronomy and Astrophysics
Astrophysics
Solar and Stellar Astrophysics
8 pages, 4 figures, MNRAS, in press
Scientific paper
We report the serendipitous discovery of a ring nebula around a candidate Wolf-Rayet (WR) star, HBHA 4202-22, in Cygnus using the Spitzer Space Telescope archival data. Our spectroscopic follow-up observations confirmed the WR nature of this star (we named it WR138a) and showed that it belongs to the WN8-9h subtype. We thereby add a new example to the known sample of late WN stars with circumstellar nebulae. We analyzed the spectrum of WR138a by using the Potsdam Wolf-Rayet (PoWR) model atmospheres, obtaining a stellar temperature of 40 kK. The stellar wind composition is dominated by helium with 20 per cent of hydrogen. The stellar spectrum is highly reddened and absorbed (E_{B-V} = 2.4 mag, A_V = 7.4 mag). Adopting a stellar luminosity of log L/Lsun = 5.3, the star has a mass-loss rate of 10^{-4.7} Msun yr^{-1}, and resides in a distance of 4.2 kpc. We measured the proper motion for WR138a and found that it is a runaway star with a peculiar velocity of ~50 km/s. Implications of the runaway nature of WR138a for constraining the mass of its progenitor star and understanding the origin of its ring nebula are discussed.
Bomans Dominik J.
Cherepashchuk Anatol M.
Fabrika Sergei
Goranskij Vitalij P.
Gvaramadze Vasilii V.
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