New Wolf-Rayet star and its circumstellar nebula in Aquila
V.V. Gvaramadze1, A.Y. Kniazev2,3 W.-R. Hamann4, L.N. Berdnikov1, S. Fabrica5, A.F. Valeev5,
2South African Astronomical Observatory, Cape Town, South Africa
3Southern African Large Telescope Foundation, Cape Town, South Africa
4Institut für Physik und Astronomie, Universität Potsdam, Germany
5Special Astrophysical Observatory, Nizhnij Arkhyz 369167, Russia
We report the discovery of a new Wolf-Rayet star in Aquila via detection of its circumstellar nebula (reminiscent of ring nebulae associated with late WN stars) using the Spitzer Space Telescope archival data. Our spectroscopic follow-up of the central point source associated with the nebula showed that it is a WN7h star (we named it WR121b). We analyzed the spectrum of WR121b by using the Potsdam Wolf-Rayet (PoWR) model atmospheres, obtaining a stellar temperature of ~50kK. The stellar wind composition is dominated by helium with ~20 per cent of hydrogen. The stellar spectrum is highly reddened (EB-V = 2.85mag). Adopting an absolute magnitude of Mv = -5.7, the star has a luminosity of log L/Lsun = 5.75 and a mass-loss rate of 10-4.7 Msun/yr, and resides at a distance of 6.3 kpc. We searched for a possible parent cluster of WR121b and found that this star is located at ~1 degree from the young star cluster embedded in the giant H II region W43 (containing a WN7+a/OB? star - WR121a). We also discovered a bow shock around the O9.5III star ALS9956, located at ~0.5 degree from the cluster. We discuss the possibility that WR121b and ALS9956 are runaway stars ejected from the cluster in W43.
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