* Astronomy

Title: SDSS J1152+0248: An eclipsing double white dwarf from the Kepler K2 campaign
Author: N. Hallakoun, D. Maoz, M. Kilic, T. Mazeh, E. Agol, K. J. Bell, S. Bloemen, W. R. Brown, J. Debes, S. Faigler, A. Gianninas, I. Kull, T. Kupfer, A. Loeb, B. M. Morris, F. Mullally

We report the discovery of the sixth known eclipsing double white dwarf (WD) system, SDSS J1152+0248, with a 2.39677 ± 0.00001 h orbital period, in data from the Kepler Mission's K2 continuation. Analysing and modelling the K2 data together with ground-based fast photometry, spectroscopy, and radial-velocity measurements, we determine that the primary is a DA-type WD with mass M1 = 0.378 ± 0.047 Msun, radius R1 = 0.0209 ± 0.0021 Rsun, and cooling age t1 = 65 ± 34 Myr. No lines are detected, to within our sensitivity, from the secondary WD, but it is likely also of type DA. Its central surface flux, as measured from the secondary eclipse, is 0.31 of the primary flux. Its mass, radius, and cooling age, respectively, are M2 = 0.226 +0.073 -0.052 Msun, R2 = 0.0235 +0.0055 -0.0044 Rsun, and 220 ± 100 Myr. SDSS J1152+0248 is almost a twin of the double-lined eclipsing WD system CSS 41177.

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