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Title: AL Cassiopeiae: An F-type contact binary system with a cool stellar companion

According to the general catalog of variable stars, AL Cas was classified as an EW-type eclipsing binary with a spectral type of B and an orbital period of P = 0.5005555 days. The first photometric light curves of the close binary in the B, V, R, and I bands are presented. New low-resolution spectra indicate that its spectral type is about F7 rather than B-type. A photometric analysis with the Wilson-Devinney method suggests that it is a contact binary (f = 39.3%) with a mass ratio of 0.61. Using 17 newly determined eclipse times together with those collected from the literature, we found that the observed–calculated (O – C) curve of AL Cas shows a cyclic change with a period of 86.6 yr and an amplitude of 0.0181 days. The periodic variation was analyzed for the light-travel time effect via the presence of a third body. The mass of the third body was determined to be M {sub 3}sin i' = 0.29(± 0.05) M {sub ☉} when a total mass of 2.14 M {sub ☉} for AL Cas is adopted. It is expected that the cool companion star may have played an important role in the origin and evolution ofmore » the system by removing angular momentum from the central binary system during early dynamical interaction and/or late dynamical evolution. This causes the original detached system to have a low angular momentum and a short initial orbital period. Then it can evolve into the present contact configuration via a case A mass transfer.« less
Authors:
; ; ; ;  [1] ;  [2] ;  [3]
  1. Yunnan Observatories, Chinese Academy of Sciences (CAS), P.O. Box 110, 650011 Kunming (China)
  2. Mt. Suhora Observatory, Cracow Pedagogical University, ul. Podchorazych 2, 30-084 Krakow (Poland)
  3. Department of Physics and Astronomy, University of Nebraska, Lincoln, NE 68588-0111 (United States)
Publication Date:
OSTI Identifier:
22342232
Resource Type:
Journal Article
Resource Relation:
Journal Name: Astronomical Journal (New York, N.Y. Online); Journal Volume: 148; Journal Issue: 5; Other Information: Country of input: International Atomic Energy Agency (IAEA)
Country of Publication:
United States
Language:
English
Subject:
79 ASTROPHYSICS, COSMOLOGY AND ASTRONOMY; AMPLITUDES; ANGULAR MOMENTUM; BINARY STARS; CATALOGS; ECLIPSE; INTERACTIONS; MASS TRANSFER; PERIODICITY; RESOLUTION; SPECTRA; STAR EVOLUTION; VARIABLE STARS; VISIBLE RADIATION