Interacting binaries W Serpentids and double periodic variables

W Serpentids and double periodic variables (DPVs) are candidates for close interacting binaries in a non-conservative evolutionary stage; while W Serpentids are defined by high-excitation ultraviolet emission lines present during most orbital phases, and by usually showing variable orbital periods,...

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Bibliographic Details
Published in:Monthly notices of the Royal Astronomical Society 2016-01, Vol.455 (2), p.1728-1745
Main Authors: Mennickent, R. E., Otero, S., Kołaczkowski, Z.
Format: Article
Language:English
Subjects:
Accretion disks
Binary stars
Constants
Discs
Evolutionary
Mass transfer
Orbitals
Photometry
Star & galaxy formation
Symbols
Ultraviolet astronomy
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Summary:W Serpentids and double periodic variables (DPVs) are candidates for close interacting binaries in a non-conservative evolutionary stage; while W Serpentids are defined by high-excitation ultraviolet emission lines present during most orbital phases, and by usually showing variable orbital periods, DPVs are characterized by a long photometric cycle lasting roughly 33 times the (practically constant) orbital period. We report the discovery of seven new Galactic DPVs, increasing the number of known DPVs in our Galaxy by 50 per cent. We find that DPVs are tangential-impact systems, i.e. their primaries have radii barely larger than the critical Lubow–Shu radius. These systems are expected to show transient discs, but we find that they host stable discs with radii smaller than the tidal radius. Among tangential-impact systems including DPVs and semi-detached Algols, only DPVs have primaries with masses between 7 and 10 M⊙. We find that DPVs are in a Case-B mass transfer stage with donor masses between 1 and 2 M⊙ and with primaries resembling Be stars. W Serpentids are impact and non-impact systems, their discs extend until the last non-intersecting orbit and show a larger range of stellar mass and mass ratio than DPVs. Infrared photometry reveals significant colour excesses in many DPVs and W Serpentids, usually larger for the latter ones, suggesting variable amounts of circumstellar matter.
ISSN:0035-8711
1365-2966
DOI:10.1093/mnras/stv2433