SDSS J1152+0248: an eclipsing double white dwarf from the Kepler K2 campaign

We report the discovery of the sixth known eclipsing double white dwarf (WD) system, SDSS J1152+0248, with a 2.3968 ± 0.0003 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 M 1 = 0.47 ± 0.11 M⊙, radius R 1 = 0.0197 ± 0.0035 R⊙, and cooling age t 1 = 52 ± 36 Myr. No lines are detected, to within our sensitivity, from the secondary WD, but it is likely also of type DA. Its central surface brightness, as measured from the secondary eclipse, is 0.31 of the primary's surface brightness. Its mass, radius, and cooling age, respectively, are M 2 = 0.44 ± 0.09 M⊙, $R_2=0.0223^{+0.0064}_{-0.0050}\,\mathrm{R}_{\odot }$ , and t 2 = 230 ± 100 Myr. SDSS J1152+0248 is a near twin of the double-lined eclipsing WD system CSS 41177.