Discovery of a new Wolf Rayet star and its ring nebula in Cygnus
V.V. Gvaramadze1, S. Fabrica2, W.-R. Hamann3, O. Sholukhova2, A.F. Valeev2, V.P. Goranskij1, A.M. Cherepashchuk1, D.J. Bomans4, L.M. Oskinova3
2Special Astrophysical Observatory, Nizhnij Arkhyz 369167, Russia
3Institut für Physik und Astronomie, Universität Potsdam, Germany
4Astronomical Institute, Ruhr-University Bochum, Universitätstr. 150, 44780 Bochum, Germany
We report the serendipitous discovery of a ring nebula around a candidate Wolf Rayet (WR) star, HBHA4202-22, in Cygnus using the Spitzer Space Telescope archival data. Our spectro-scopic 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 analysed 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 (EB-V = 2.4 mag, AV = 7.4 mag). Adopting a stellar luminosity of log L/L = 5.3, the star has a mass-loss rate of 10-4.7 Msun/yr, 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 WR 138a for constraining the mass of its progenitor star and understanding the origin of its ring nebula are discussed.
The full article is available as PDF or PostScript file via anonymous ftp.
user: anonymous or ftp; Password: your e-mail address;
files: as in the links listed below
Display PostScript file (local users only!)