Detalles de publicación
PP 013003
KIC 10449976: discovery of an extreme helium subdwarf in the Kepler field
(1) Armagh Observatory, College Hill, Armagh BT61 9DG, UK (2) Instituto de Astrofísica de Canarias, La Laguna E-3200, Tenerife, Spain (3) Departamento de Astrofísica, Universidad de La Laguna, La Laguna E-38205, Tenerife, Spain (4) Department of Physics, University of Warwick, Coventry CV4 7AL, UK (5) NASA Ames Research Center, M/S 244-40, Moffett Field, CA 94035, USA (6) Bay Area Environmental Research Institute, Inc., 560 Third St. West, Sonoma, CA 95476, USA (7) Isaac Newton Group of Telescopes, Apartado de Correos 321, E-38700 Santa Cruz de la Palma, Canary Islands, Spain (8) Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK (9) Finnish Centre for Astronomy with ESO (FINCA), University of Turku, Väisäl äntie 20, FI-21500 PIIKKIÖ, Finland
Optical spectroscopy of the blue star KIC 10449976 shows that it is an extremely helium-rich subdwarf with effective temperature Teff = 40 000 ± 300 K and surface gravity log g = 5.3 ± 0.1. Radial-velocity measurements over a 5 d time-scale show an upper variability limit of ≈50 ± 20 km s−1. Kepler photometry of KIC 10449976 in both long and short cadence modes shows evidence for a periodic modulation on a time-scale of ≈3.9 d. We have examined the possibility that this modulation is not astrophysical but conclude that it is most likely real. We discuss whether the modulation could be caused by a low-mass companion, by stellar pulsations or by spots. The identification of any one of these as cause has important consequences for understanding the origin of helium-rich subdwarfs.