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Cited by 27Stellar, planetary, and galactic studiesAstrophysical Phenomena and ObservationsAstronomy and Astrophysical Research

The Cessation of Eclipses in SS Lacertae: The Mystery Solved

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Torres, Guillermo, Stefanik, Robert P.·2000·The Astronomical Journal
DOI 10.1086/301290
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Abstract

The 14.4 day period eclipsing binary SS Lacertae in the open cluster NGC 7209 is unusual in that the eclipses stopped completely about the middle of this century, giving rise to considerable speculation as to the cause. Disruption of the binary through a collision with another member of the cluster and, more likely, gravitational perturbations from a third star in the system have been proposed to explain the phenomenon. We present here the results of our intensive radial velocity monitoring of the object, which show clearly that there is indeed a third star in the system in a slightly eccentric orbit with a period of about 679 days. We also reanalyze the historical light curves of SS Lac to determine the properties of the system early in the century. We discuss the implications of our findings in terms of changes in the inclination angle of the close pair. An analysis of available times of eclipse for SS Lac together with the new velocity information has also revealed apsidal motion in the system, = 0 0137 cycle -1 , corresponding to an apsidal period of about 1000 yr. We argue that the third star is probably responsible for this effect also.

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  1. [21]21. Gime nez, Gray, D. F. 1992, The Observation and Analysis of Stellar Photospheres (2d ed. ; Cambridge : Cambridge Univ. Press)
  2. [35]35. Latham, D. W. 1992, in IAU Colloq. 135, Complementary Approaches to Double and Multiple Star Research, ed. H. A. McAlister & W. I. Hart- kopf (ASP Conf. Ser. 32) (San Francisco : ASP), 110
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  4. [55]55. Schiller, S. J. 1996, Astronomy, 24(7), 46
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  6. [57]57. Schiller, S. J., & Milone, E. F. 1996, in ASP Conf. Ser. 90, The Origins, Evolutions, and Destinies of Binary Stars in Clusters, ed. E. F. Milone & J.-C. Mermilliod (San Francisco : ASP), 120

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Authors
Torres, G., & Stefanik, R. P.
Affiliations
Center for Astrophysics Harvard & Smithsonian (US)
ORCID
Torres, Guillermo
Venue
The Astronomical Journal
Publisher
American Astronomical Society
Published
2000-04
Volume
119
Issue
4
Pages
1914-1929
ISSN
0004-6256 (ISSN-L)
DOI
10.1086/301290
OpenAlex
W1992458446
Semantic Scholar
890e6509e38ec881ac84c7aa9c3ec01e64123ef1
Cited by
27
References
33
Citations by year
2026: 1 · 2025: 2 · 2023: 1 · 2022: 1 · 2019: 3 · 2018: 1 · 2017: 2 · 2016: 1 · 2012: 1
FWCI
1.24
Type
journal article
Language
en
Open access
Locations
The Astronomical Journal (publishedVersion)
Topics
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Stellar, planetary, and galactic studies
  • Physical Sciences › Physics and Astronomy › Astronomy and Astrophysics › Astrophysical Phenomena and Observations
  • Physical Sciences › Physics and Astronomy › Instrumentation › Astronomy and Astrophysical Research
Keywords
eclipsing binaries, open clusters, radial velocity monitoring, orbital eccentricity, orbital inclination change, apsidal motion, gravitational perturbations, binary disruption

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