期刊
ASTROPHYSICAL JOURNAL
卷 753, 期 1, 页码 -出版社
IOP PUBLISHING LTD
DOI: 10.1088/0004-637X/753/1/90
关键词
planetary systems; planets and satellites: detection; stars: abundances; stars: fundamental parameters; stars: late-type
资金
- NSF [AST-0908419, AST 06-07757, AST 09-08419]
- NASA [NNX10AI90G, NNX11AC33G, NAS5-26555]
- NASA Office of Space Science [NNX09AF08G]
- Alfred P. Sloan Foundation
- National Science Foundation
- U.S. Department of Energy
- National Aeronautics and Space Administration
- Japanese Monbukagakusho
- Max Planck Society
- Higher Education Funding Council for England
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [908406] Funding Source: National Science Foundation
- Direct For Mathematical & Physical Scien
- Division Of Astronomical Sciences [0908419] Funding Source: National Science Foundation
We estimate the stellar parameters of late K- and early M-type Kepler target stars. We obtain medium-resolution visible spectra of 382 stars with K-P - J > 2 (similar or equal to K5 and later spectral type). We determine luminosity class by comparing the strength of gravity-sensitive indices (CaH, K I, Ca II, and Na I) to their strength in a sample of stars of known luminosity class. We find that giants constitute 96% +/- 1% of the bright (K-P < 14) Kepler target stars, and 7% +/- 3% of dim (K-P > 14) stars, significantly higher than fractions based on the stellar parameters quoted in the Kepler Input Catalog (KIC). The KIC effective temperatures are systematically (110(-35)(+15) K) higher than temperatures we determine from fitting our spectra to PHOENIX stellar models. Through Monte Carlo simulations of the Kepler exoplanet candidate population, we find a planet occurrence of 0.36 +/- 0.08 when giant stars are properly removed, somewhat higher than when a KIC log g > 4 criterion is used (0.27 +/- 0.05). Last, we show that there is no significant difference in g - r color (a probe of metallicity) between late-type Kepler stars with transiting Earth-to-Neptune-size exoplanet candidates and dwarf stars with no detected transits. We show that a previous claimed offset between these two populations is most likely an artifact of including a large number of misidentified giants.
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