One, two or three stars? An investigation of an unusual eclipsing binary candidate undergoing dramatic period changes

Abstract

We report our investigation of 1SWASP J234401.81-212229.1, a variable with a 18461.6 s period. After identification in a 2011 search of the SuperWASP archive for main-sequence eclipsing binary candidates near the distribution's short-period limit of approx. 0.20 d, it was measured to be undergoing rapid period decrease in our earlier work, though later observations supported a cyclic variation in period length. Spectroscopic data obtained in 2012 with the Southern African Large Telescope did not, however, support the interpretation of the object as a normal eclipsing binary. Here, we consider three possible explanations consistent with the data: a single-star oblique rotator model in which variability results from stable cool spots on opposite magnetic poles; a two-star model in which the secondary is a brown dwarf; and a three-star model involving a low-mass eclipsing binary in a hierarchical triple system. We conclude that the latter is the most likely model.

8 pages, 20 figures. Accepted for publication at Astronomy & Astrophysics. After publication, table 2 will appear at the CDS via anonymous ftp to cdsarc.u-strasbg.fr (130.79.128.5) or via http://cdsweb.u-strasbg.fr/cgi-bin/qcat?J/A+A/

References in corpus (3)

• Period and period change measurements for 143 SuperWASP eclipsing binary candidates near the short-period limit and discovery of a doubly eclipsing quadruple system
• Period decrease in three SuperWASP eclipsing binary candidates near the short-period limit
• A young hierarchical triple system harbouring a candidate debris disc

Cited by in corpus (8)

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• Contact binaries at the short period cut-off I. statistics and the first photometric investigations of ten totally eclipsing systems
• CoBiToM Project -- I. Contact Binaries Towards Merging
• Orbital period changes and the higher-order multiplicity fraction amongst SuperWASP eclipsing binaries
• CoBiToM Project -- II: Evolution of contact binary systems close to the orbital period cut-off
• The doubly eclipsing quintuple low-mass star system 1SWASP J093010.78+533859.5
• Photometric study of three ultrashort-period contact binaries
• On the Nature of Long-Period Dwarf Novae with Rare and Low-Amplitude Outbursts