An analysis of the light curve of the post common envelope binary MT Serpentis

Citation
A. Bruch et al., An analysis of the light curve of the post common envelope binary MT Serpentis, ASTRON ASTR, 377(3), 2001, pp. 898-910
Citations number
23
Categorie Soggetti
Space Sciences
Journal title
ASTRONOMY & ASTROPHYSICS
ISSN journal
14320746 → ACNP
Volume
377
Issue
3
Year of publication
2001
Pages
898 - 910
Database
ISI
SICI code
1432-0746(200110)377:3<898:AAOTLC>2.0.ZU;2-7
Abstract
Photometric observations of MT Ser, the central star of the planetary nebul a Abell 41 are presented. The periodic modulations detected by Grauer & Bon d (1983) are confirmed, thus firmly establishing the binary nature of MT Se r. The significantly enlarged time base permits us to derive more accurate ephemeris. The orbital period is either P-1 = 0.113226533 days or twice tha t value, P-2 = 0.226453066 days. We analyze the light curve (after a carefu l subtraction of the nebular contribution) with the Wilson-Devinney light c urve synthesis routine. Since it is not a priori clear which is the true or bital period of MT Ser, two radically different models, one based on P-1 th e other on P-2 are considered: (1) A low temperature component orbiting aro und a hot sub-dwarf. The variability is then due to a reflection effect tog ether with ellipsoidal variations of one or both components. (2) Two hot su b-dwarfs of similar temperature and luminosity, partially eclipsing each ot her and exhibiting ellipsoidal variations. In both models, the primary as w ell as the secondary component are required to almost fill their respective Roche lobes. A contact configuration is possible. Pros and cons can be fou nd for either of the two models. A final decision between them has to await the observations of a radial velocity curve. The orbital period is current ly decreasing at a rate of (P) over dot/P = -1.15 x 10(-9) d(-1). Interpret ing this as due to mass loss via a stellar winds permits us to estimate mas s loss rates depending on the different model assumptions.