Dynamical masses, absolute radii and 3D orbits of the triply eclipsing star HD 181068 from Kepler photometry

Borkovits, Tamás and Derekas, Aliz and Kiss, L. László and Király, A. and Forgácsné Dajka, Emese and Bíró, Imre Barna and Bedding, TR and Bryson, ST and Huber, D and Szabó, Róbert (2013) Dynamical masses, absolute radii and 3D orbits of the triply eclipsing star HD 181068 from Kepler photometry. MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY, 428 (2). pp. 1656-1672. ISSN 0035-8711

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Abstract

HD 181068 is the brighter of the two known triply eclipsing hierarchical triple starsin the Kepler field. It has been continuously observed for more than 2 years with theKepler space telescope. Of the nine quarters of the data, three have been obtained inshort-cadence mode, that is one point per 58.9 s. Here we analyse this unique datasetto determine absolute physical parameters (most importantly the masses and radii)and full orbital configuration using a sophisticated novel approach. We measure eclipsetiming variations (ETVs), which are then combined with the single-lined radial velocitymeasurements to yield masses in a manner equivalent to double-lined spectroscopicbinaries. We have also developed a new light curve synthesis code that is used tomodel the triple, mutual eclipses and the effects of the changing tidal field on the stellarsurface and the relativistic Doppler-beaming. By combining the stellar masses from theETV study with the simultaneous light curve analysis we determine the absolute radiiof the three stars. Our results indicate that the close and the wide subsystems revolvein almost exactly coplanar and prograde orbits. The newly determined parametersdraw a consistent picture of the system with such details that have been beyond reachbefore.

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