KIC 10449976: discovery of an extreme helium subdwarf in the Kepler field
Abstract
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.
- Publication:
-
Monthly Notices of the Royal Astronomical Society
- Pub Date:
- March 2013
- DOI:
- 10.1093/mnras/sts579
- arXiv:
- arXiv:1212.1358
- Bibcode:
- 2013MNRAS.429.3207J
- Keywords:
-
- stars: abundances;
- stars: chemically peculiar;
- stars: individual: KIC 10449976;
- subdwarfs;
- Astrophysics - Solar and Stellar Astrophysics
- E-Print:
- Accepted by MNRAS