Bibcode
Howarth, I. D.; Dufton, P. L.; Dunstall, P. R.; Evans, C. J.; Almeida, L. A.; Bonanos, A. Z.; Clark, J. S.; Langer, N.; Sana, H.; Simón-Díaz, S.; Soszyński, I.; Taylor, W. D.
Bibliographical reference
Astronomy and Astrophysics, Volume 582, id.A73, 19 pp.
Advertised on:
10
2015
Journal
Citations
12
Refereed citations
11
Description
Aims: We investigate the characteristics of two newly discovered
short-period, double-lined, massive binary systems in the Large
Magellanic Cloud, VFTS 450 (O9.7 II-Ib + O7::) and VFTS 652 (B1 Ib + O9:
III:). Methods: We perform model-atmosphere analyses to
characterise the photospheric properties of both members of each binary
(denoting the "primary" as the spectroscopically more conspicuous
component). Radial velocities and optical photometry are used to
estimate the binary-system parameters. Results: We estimate
Teff = 27 kK, log g = 2.9 (cgs) for the VFTS 450 primary
spectrum (34 kK, 3.6: for the secondary spectrum); and Teff =
22 kK, log g = 2.8 for the VFTS 652 primary spectrum (35 kK, 3.7: for
the secondary spectrum). Both primaries show surface nitrogen
enrichments (of more than 1 dex for VFTS 652), and probable moderate
oxygen depletions relative to reference LMC abundances. We determine
orbital periods of 6.89 d and 8.59 d for VFTS 450 and VFTS 652,
respectively, and argue that the primaries must be close to filling
their Roche lobes. Supposing this to be the case, we estimate component
masses in the range ~20-50 M⊙. Conclusions: The
secondary spectra are associated with the more massive components,
suggesting that both systems are high-mass analogues of classical Algol
systems, undergoing case-A mass transfer. Difficulties in reconciling
the spectroscopic analyses with the light-curves and with evolutionary
considerations suggest that the secondary spectra are contaminated by
(or arise in) accretion disks.
Based on observations obtained at the European Southern Observatory Very
Large Telescope (VLT) as part of programmes 182.D-0222 and
090.D-0323.Tables 2, 3, and 8 are available in electronic form at http://www.aanda.org
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