@article{GvaramadzeFabrikaHamannetal.2009,
  author    = {Gvaramadze, Vasily V. and Fabrika, Sergei Nikolaevich and Hamann, Wolf-Rainer and Sholukhova, Olga N. and Valeev, Azamat F. and Goranskij, Vitaly P. and Cherepashchuk, Anatol M. and Bomans, Dominik J. and Oskinova, Lida},
  title     = {Discovery of a new Wolf-Rayet star and its ring nebula in Cygnus},
  issn      = {0035-8711},
  doi       = {10.1111/j.1365-2966.2009.15492.x},
  year      = {2009},
  abstract  = {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 WR 138a) 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 WR 138a 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, A(V) = 7.4 mag). Adopting a stellar luminosity of log L/L-circle dot = 5.3, the star has a mass-loss rate of 10-4.7 M- circle dot yr-1, and resides in a distance of 4.2 kpc. We measured the proper motion for WR 138a and found that it is a runaway star with a peculiar velocity of similar or equal to 50 km s-1. 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.},
  language  = {en}
}