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- Title
Does the Wolf-Rayet binary CQ Cephei undergo sporadic mass transfer events?
- Authors
Koenigsberger, Gloria; Schmutz, Werner; Skinner, Stephen L.
- Abstract
Context: Stellar wind mass-loss in binary systems carries away angular momentum causing a monotonic increase in the orbital period, P> 0. Despite possessing a significant stellar wind, the eclipsing Wolf-Rayet (WR) binary system CQ Cep does not show the expected monotonic period increase, in fact, it is sometimes reported to display the opposite behavior. Aims: The objective of this paper is to perform a new analysis of the rate of period change P and determine the conditions under which Roche-lobe overflow (RLO) mass-transfer combined with wind mass loss can explain the discrepant behavior. Methods: The historic records of times of light curve minima were reviewed and compared with the theoretical values of P for cases in which both wind mass-loss and RLO occur simultaneously. Results: The observational data indicate that P alternates between positive and negative values on a timescale of years. The negative values (P ~ -0.6 to -8.5 s yr-1) are significantly larger in absolute value than the positive ones (P ~ + 0.2 to +1.2 s yr-1). We find that a plausible scenario for CQ Cep is one in which the O star undergoes intense but sporadic RLO events that lead to accretion onto the WR star, at which times P< 0. At other times, P> 0 when the WR wind, and possibly material swept up from the O star, carries angular momentum away from the system. A scenario in which the WR star is the mass donor cannot be excluded, but requires that either the WR wind mass-loss rate undergoes large sporadic enhancements or that an additional process that removes angular momentum from the system be present.
- Subjects
BINARY stars; WOLF-Rayet stars; MASS transfer; STELLAR mass; BINARY systems (Astronomy); STELLAR winds; ANGULAR momentum (Nuclear physics)
- Publication
Astronomy & Astrophysics / Astronomie et Astrophysique, 2017, Vol 601, p1
- ISSN
0004-6361
- Publication type
Article
- DOI
10.1051/0004-6361/201630360