Modelling the asymmetric wind of the luminous blue variable binary MWC 314
Abstract
Aims: We present a spectroscopic analysis of MWC 314, a luminous blue variable (LBV) candidate with an extended bipolar nebula. The detailed spectroscopic variability is investigated to determine if MWC 314 is a massive binary system with a supersonically accelerating wind or a low-mass B[e] star. We compare the spectrum and spectral energy distribution to other LBVs (such as P Cyg) and find very similar physical wind properties, indicating strong kinship.
Methods: We combined long-term high-resolution optical spectroscopic monitoring and V-band photometric observations to determine the orbital elements and stellar parameters and to investigate the spectral variability with the orbital phases. We developed an advanced model of the large-scale wind-velocity and wind-density structure with 3-D radiative transfer calculations that fit the orbitally modulated P Cyg profile of He i λ5876, showing outflow velocities above 1000 km s-1.
Results: We find that MWC 314 is a massive semi-detached binary system of ≃1.22 AU, observed at an inclination angle of i = 72.8° with an orbital period of 60.8 d and e = 0.23. The primary star is a low-vsini LBV candidate of m1 = 39.6 M⊙ and R1 = 86.8 R⊙. The detailed radiative transfer fits show that the geometry of wind density is asymmetric around the primary star with increased wind density by a factor of 3.3, which leads the orbit of the primary. The variable orientation causes the orbital modulation that is observed in absorption portions of P Cyg wind lines. Wind accretion in the system produces a circumbinary disc.
Conclusions: MWC 314 is in a crucial evolutionary phase of close binary systems, when the massive primary star has its H envelope being stripped and is losing mass to a circumbinary disc. MWC 314 is a key system for studying the evolutionary consequences of these effects.
- Publication:
-
Astronomy and Astrophysics
- Pub Date:
- November 2013
- DOI:
- 10.1051/0004-6361/201220421
- arXiv:
- arXiv:1308.4638
- Bibcode:
- 2013A&A...559A..16L
- Keywords:
-
- stars: emission-line;
- Be;
- binaries: spectroscopic;
- stars: massive;
- stars: winds;
- outflows;
- line: profiles;
- radiative transfer;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- 14 pages, 25 figures, 4 tables, Accepted for Astronomy and Astrophysics