The nature of the Cygnus extreme B supergiant 2MASS J20395358+4222505. Issue 3 (22nd February 2022)

• Record Type: Journal Article
• Authors: Herrero, A; Berlanas, S R; Gil de Paz, A; Comerón, F; Puls, J; Ramírez Alegría, S; Garcia, M; Lennon, D J; Najarro, F; Simón-Díaz, S; Urbaneja, M A; Gallego, J; Carrasco, E; Iglesias, J; Cedazo, R; García Vargas, M L; Castillo-Morales, Á; Pascual, S; Cardiel, N; Pérez-Calpena, A; Gómez-Alvarez, P; Martínez-Delgado, I
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 511:Issue 3(2022)
• Page Start: 3113
• Page End: 3124
• Publication Date: 2022-02-22
• Subjects: stars: evolution -- stars: individual: 2MASS J20395358+4222505 -- stars: massive -- supergiants -- stars: winds, outflows; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stab3660
• Languages: English
• ISSNs: 0035-8711

Abstract

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 Hα 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 gc = 2.88 ± 0.15. The rotational velocity found is large for a B supergiant, $v$ sin i = 110 ± 25 $\rm km\, s^{-1}$ . 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⊙, log( L /L⊙ ) = 5.71 ± 0.04 and a spectroscopic mass of 46.5 ± 15.0 M⊙ . The clumped mass-loss rate (clumping factor 10) is very high for the spectral type, $\dot{M}$ = 2.4 × 10 −6 M⊙ 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.