# Summary of K2 Program GO16089

Title: Kepler lightcurves of hot subdwarf stars

PI: Kupfer, Thomas (Caltech)
CoIs: Schaffenroth, Veronika; Ziegerer, Eva; Prince, Thomas A; Heber, Ulrich; Geier, Stephan

Hot subdwarf B (sdB) stars are core-helium burning stars that have evolved from the red giant stage to the extreme blue end of the horizontal branch in a process where almost the entire envelope has been lost through interactions with a companion. Many sdBs are known to have close companions with periods ranging from 0.05 to 10 days, and must have evolved through the common-envelope-ejection (CEE) process. The closest systems are quite easy to study from the ground, but Kepler observations have opened the door for precise studies of the population of systems with periods between 0.5 and and 10 days. 

Several close binary sdB stars were discovered by the original Kepler mission. The excellent Kepler light curves show photometric signals from Doppler beaming, ellipsoidal deformations and mutual irradiation effects. Long-cadence K2 observations presents us with an unique opportunity to accumulate a larger sample of post-common envelope sdB binaries that can shed light on the statistics of the CEE process, and thereby constrain the long sought after efficiency parameters that govern the common envelope stage of evolution. In the process we hope to find new particularly interesting binary systems, such as the eclipsing cases and those with extraordinary masses that could be progenitors of type-Ia supernovae.

# Targets requested by this program that have been observed (26)
EPIC ID, RA (J2000) [deg], Dec (J2000) [deg], magnitude, Investigation IDs
211421561, 135.177809, 11.963889, 14.902, GO16016_LC|GO16051_LC|GO16080_LC|GO16089_LC|GO16051_SC|GO16080_SC
211433013, 137.605977, 12.140855, 14.017, GO16016_LC|GO16065_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16099_LC|GO16080_SC
211437457, 136.420494, 12.207815, 14.729, GO16016_LC|GO16051_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16051_SC|GO16080_SC
211460944, 134.616317, 12.566363, 15.362, GO16016_LC|GO16065_LC|GO16089_LC
211495446, 130.432738, 13.074995, 14.03, GO16016_LC|GO16051_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16099_LC|GO16051_SC|GO16080_SC
211552072, 131.486854, 13.869807, 17.498, GO16016_LC|GO16051_LC|GO16080_LC|GO16089_LC|GO16051_SC|GO16080_SC
211559083, 131.087953, 13.968805, 18.18, GO16016_LC|GO16089_LC
211720816, 129.756278, 16.196671, 16.709, GO16016_LC|GO16065_LC|GO16089_LC|GO16901_LC
211727748, 130.344641, 16.292858, 14.99, GO16051_LC|GO16089_LC|GO16051_SC
211765471, 133.348574, 16.826456, 14.035, GO16016_LC|GO16065_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16080_SC
211881419, 132.935287, 18.456246, 13.302, GO16089_LC|GO16096_LC|GO16096_SC
211904152, 138.779593, 18.787895, 15.932, GO16016_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16080_SC
211910684, 137.221641, 18.886145, 15.985, GO16016_LC|GO16080_LC|GO16089_LC|GO16080_SC
211930840, 138.800257, 19.1874, 19.13, GO16016_LC|GO16089_LC
212034957, 135.759977, 20.835825, 18.615, GO16016_LC|GO16046_LC|GO16089_LC
212126168, 127.068229, 22.540674, 12.613, GO16089_LC
212204284, 131.549977, 24.41959, 15.639, GO16016_LC|GO16051_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16051_SC|GO16080_SC
212212793, 132.907585, 24.697301, 14.296, GO16016_LC|GO16051_LC|GO16080_LC|GO16089_LC|GO16096_LC|GO16051_SC|GO16080_SC
228682339, 127.100853, 21.4324303, 17.73, GO16016_LC|GO16046_LC|GO16089_LC
228682488, 133.0733337, 21.2769394, 16.0, GO16016_LC|GO16051_LC|GO16065_LC|GO16080_LC|GO16089_LC|GO16051_SC|GO16080_SC
251335876, 139.329751, 19.910696, 16.763, GO16016_LC|GO16046_LC|GO16062_LC|GO16089_LC|GO16096_LC
251344281, 141.021882, 20.596246, 14.75, GO16016_LC|GO16051_LC|GO16062_LC|GO16089_LC|GO16096_LC|GO16051_SC|GO16062_SC
251357585, 140.690827, 21.710833, 19.01, GO16016_LC|GO16046_LC|GO16089_LC
251372905, 138.066949, 22.914687, 15.301, GO16016_LC|GO16080_LC|GO16089_LC|GO16080_SC
251383153, 137.687095, 23.679069, 18.267, GO16016_LC|GO16089_LC
251410019, 134.537897, 25.359623, 18.871, GO16016_LC|GO16089_LC