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Two white dwarfs in ultrashort binaries with detached, eclipsing, likely substellar companions detected by K2

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posted on 2017-08-14, 16:23 authored by S. G. Parsons, J. J. Hermes, T. R. Marsh, B. T. Gänsicke, P.-E. Tremblay, S. P. Littlefair, D. I. Sahman, R. P. Ashley, M. Green, S. Rattanasoon, V. S. Dhillon, M. R. Burleigh, S. L. Casewell, D. A. H. Buckley, I. P. Braker, P. Irawati, E. Dennihy, P. Rodríguez-Gil, D. E. Winget, K. I. Winget, Keaton J. Bell, Mukremin Kilic
Using data from the extended Kepler mission in K2 Campaign 10, we identify two eclipsing binaries containing white dwarfs with cool companions that have extremely short orbital periods of only 71.2 min (SDSS J1205−0242, a.k.a. EPIC 201283111) and 72.5 min (SDSS J1231+0041, a.k.a. EPIC 248368963). Despite their short periods, both systems are detached with small, low-mass companions, in one case a brown dwarf and in the other case either a brown dwarf or a low-mass star. We present follow-up photometry and spectroscopy of both binaries, as well as phase-resolved spectroscopy of the brighter system, and use these data to place preliminary estimates on the physical and binary parameters. SDSS J1205−0242 is composed of a 0.39 ± 0.02 M⊙ helium-core white dwarf that is totally eclipsed by a 0.049 ± 0.006 M⊙ (51 ± 6MJ) brown-dwarf companion, while SDSS J1231+0041 is composed of a 0.56 ± 0.07 M⊙ white dwarf that is partially eclipsed by a companion of mass ≲0.095  M⊙. In the case of SDSS J1205−0242, we look at the combined constraints from common-envelope evolution and brown-dwarf models; the system is compatible with similar constraints from other post-common-envelope binaries, given the current parameter uncertainties, but has potential for future refinement.


SGP acknowledges the support of the Leverhulme Trust. The research leading to these results has received funding from the European Research Council under the European Union's Seventh Framework Programme (FP/2007-2013)/ERC Grant Agreement numbers 340040 (HiPERCAM) and 320964 (WDTracer), as well as the European Union's Horizon 2020 Research and Innovation Programme/ERC Grant Agreement number 677706 (WD3D). ULTRACAM, and TRM, VSD and SPL are supported by the Science and Technology Facilities Council (STFC) under grants ST/L000733 and ST/M001350. DAHB is supported by the National Research Foundation of South Africa. Support for this work was provided by NASA through Hubble Fellowship grant #HST-HF2-51357.001-A, by NASA K2 Cycle 4 Grant NNX17AE92G, as well as NSF grants AST-1413001 and AST-1312983. This work has made use of data obtained at the Thai National Observatory on Doi Inthanon, operated by NARIT; the Southern Astrophysical Research (SOAR) telescope, which is a joint project of the Ministério da Ciência, Tecnologia, e Inovação da República Federativa do Brasil, the U.S. National Optical Astronomy Observatory, the University of North Carolina at Chapel Hill and the Michigan State University; and the McDonald Observatory of the University of Texas at Austin; as well as the SALT, through DDT programme 2016-2-DDT-006, where the assistance of Marissa Kotze is acknowledged. Data for this paper have been obtained under the International Time Programme of the CCI (International Scientific Committee of the Observatorios de Canarias of the IAC) with the GTC operated on the island of La Palma in the Observatorio del Teide/Roque de los Muchachos.



Monthly Notices of the Royal Astronomical Society, 2017, 471(1), pp. 976–986,

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/Organisation/COLLEGE OF SCIENCE AND ENGINEERING/Department of Physics and Astronomy


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