The discovery of two pulsating subdwarf B stars in NGC 6791 using Kepler data

摘要: We report the discovery of two new pulsating subdwarf B (sdB) stars in open cluster NGC 6791 using data from Kepler spacecraft. Three sdB were observed for one month short-cadence (1 min) mode and three months long-cadence (30 min) during Quarter 11 (fall 2011). The have Input Catalogue numbers 2437937, 2569576 2569583 with previous designations B5, B3 B6, respectively. Another star exists it is also known to be a pulsator. obtained Nordic Optical Telescope spectra update effective temperatures, surface gravities helium abundances compare spectroscopic properties all four on uniform model grid. We detect periodicities between 0.9 2.4 h above detection limit 0.53 parts per thousand (ppt) nine 1.1 2.2 h B5 0.37 ppt. No pulsations detected B6 threshold 0.29 ppt. less useful as few observations are pulsation period, yet they do indicate that variable month. spacings periods similar other g-mode by Kepler, indicating can associated witquals; 1 modes. A fit give 234.6 ± 0.6 242.6 1.5 s