The nature of the Cygnus extreme B supergiant 2MASS J20395358+4222505

Herrero, A.; Berlanas, S. R.; de Paz, A. Gil; Comeron, F.; Puls, J.; Ramirez Alegria, S.; Garcia, M.; Lennon, D. J.; Najarro, F.; Simon-Diaz, S.; Urbaneja, M. A.; Gallego, J.; Carrasco, E.; Iglesias, J.; Cedazo, R.; Garcia Vargas, M. L.; Castillo-Morales, A.; Pascual, S.; Cardiel, N.; Perez-Calpena, A.; Gomez-Alvarez, P. und Martinez-Delgado, I (2022): The nature of the Cygnus extreme B supergiant 2MASS J20395358+4222505. In: Monthly Notices of the Royal Astronomical Society, Bd. 511, Nr. 3: S. 3113-3124

Abstract

2MASS J20395358+4222505 is an obscured early B supergiant near the massive OB star association Cygnus OB2. Despite its bright infrared magnitude (K-s = 5.82) it has remained largely ignored because of its dim optical magnitude (B = 16.63, V = 13.68). In a previous paper, we classified it as a highly reddened, potentially extremely luminous, early B-type supergiant. We obtained its spectrum in the U, B and R spectral bands during commissioning observations with the instrument MEGARA at the Gran Telescopio CANARIAS. It displays a particularly strong H-alpha emission for its spectral type, B1 Ia. The star seems to be in an intermediate phase between supergiant and hypergiant, a group that it will probably join in the near (astronomical) future. We observe a radial velocity difference between individual observations and determine the stellar parameters, obtaining T-eff = 24 000 K and log g(c) = 2.88 +/- 0.15. The rotational velocity found is large for a B supergiant, v sin i = 110 +/- 25 km s(-1). The abundance pattern is consistent with solar, with a mild C underabundance (based on a single line). Assuming that J20395358+4222505 is at the distance of Cyg OB2, we derive the radius from infrared photometry, finding R = 41.2 +/- 4.0 R-circle dot, log(L/L-circle dot) = 5.71 +/- 0.04 and a spectroscopic mass of 46.5 +/- 15.0 M-circle dot. The clumped mass-loss rate (clumping factor 10) is very high for the spectral type, (M) over dot = 2.4 x10(-6) M-circle dot a(-1). The high rotational velocity and mass-loss rate place the star at the hot side of the bi-stability jump. Together with the nearly solar CNO abundance pattern, they may also point to evolution in a binary system, J20395358+4222505 being the initial secondary.

• Dokumententyp: Zeitschriftenartikel
• Fakultät: Physik
• Themengebiete: 500 Naturwissenschaften und Mathematik > 530 Physik
• ISSN: 0035-8711
• Sprache: Englisch