# Summary of K2 Program GO14089

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 (25)
EPIC ID, RA (J2000) [deg], Dec (J2000) [deg], magnitude, Investigation IDs
201535046, 163.117447, 1.062752, 14.439, GO14016_LC|GO14096_LC|GO14089_LC|GO14080_LC|GO14096_SC|GO14080_SC
201640895, 165.564386, 2.676184, 17.597, GO14016_LC|GO14051_LC|GO14089_LC|GO14051_SC
248411044, 162.511777, -0.010237, 13.555, GO14096_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14099_LC|GO14096_SC|GO14051_SC|GO14080_SC
248422838, 158.803172, 0.458058, 16.272, GO14016_LC|GO14096_LC|GO14089_LC|GO14080_LC|GO14080_SC
248467942, 157.591995, 2.090087, 17.244, GO14016_LC|GO14089_LC|GO14080_LC|GO14080_SC
248513530, 160.703944, 3.565382, 17.634, GO14016_LC|GO14089_LC|GO14046_LC
248520995, 165.223133, 3.773014, 17.252, GO14016_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14051_SC|GO14080_SC
248588851, 155.836676, 5.57942, 16.331, GO14016_LC|GO14096_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14046_LC|GO14051_SC|GO14080_SC
248619861, 155.365136, 6.376164, 19.17, GO14016_LC|GO14089_LC
248682887, 161.33209, 7.932435, 19.42, GO14016_LC|GO14089_LC|GO14046_LC
248685347, 155.836116, 7.992797, 16.989, GO14016_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14065_LC|GO14051_SC|GO14080_SC
248748173, 158.957034, 9.431051, 16.378, GO14016_LC|GO14096_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14065_LC|GO14051_SC|GO14080_SC
248751673, 163.857822, 9.515651, 17.436, GO14016_LC|GO14089_LC|GO14016_SC
248761152, 161.912937, 9.740084, 17.093, GO14016_LC|GO14096_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14051_SC|GO14080_SC
248767552, 154.637975, 9.893379, 14.965, GO14016_LC|GO14089_LC|GO14080_LC|GO14080_SC
248783069, 161.583956, 10.274946, 18.645, GO14016_LC|GO14089_LC
248783744, 158.076676, 10.290505, 18.816, GO14016_LC|GO14089_LC
248807515, 154.316956, 10.856649, 16.4, GO14016_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14065_LC|GO14051_SC|GO14080_SC
248810568, 165.233142, 10.928443, 14.223, GO14016_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14051_SC|GO14080_SC
248840987, 155.212445, 11.673449, 18.148, GO14016_LC|GO14051_LC|GO14089_LC|GO14051_SC
248912731, 159.635051, 13.646746, 17.35, GO14016_LC|GO14089_LC
248915544, 159.527679, 13.736695, 17.209, GO14016_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14051_SC|GO14080_SC
251457058, 163.6202, 1.087444, 17.1, GO14016_LC|GO14051_LC|GO14089_LC|GO14080_LC|GO14051_SC|GO14080_SC
251457060, 161.8546, 1.146439, 17.8, GO14016_LC|GO14089_LC
251458111, 161.465042, 9.34775, 20.432, GO14089_LC