Kepler Cool Dwarfs


APOGEE spectra of bright, cool dwarf stars with Kepler lightcurves were taken to measure stellar parameters, in particular, metallicity and abundance ratios, with the goals of estimating rotation-based ages and deriving the age-metallicity relation for low-mass stars in the Kepler field.

Finding Targets

An object whose APOGEE_TARGET2 value includes one or more of the bitmasks in the following table was targeted for spectroscopy as part of this ancillary target program. See SDSS bitmasks to learn how to use these values to identify objects in this ancillary target program.

APOGEE_TARGET2 bit name Bit Target Description
APOGEE_KEPLER_COOLDWARF 16 Kepler cool dwarf or subgiant


The Kepler mission has obtained high-precision photometry for ~150,000 stars, which will provide information on transiting planetary companions, starspots and rotation rates, and stellar pulsations. However, metallicities are largely unavailable for most of the Kepler targets. This project aims to obtain spectra for ~1200 cool dwarfs for which long or short-cadence data is available from the Kepler satellite.  Stars with these parameters have not been targeted by other APOGEE programs in the Kepler field, as they are not seismic targets, eclipsing binaries, or (usually) planet hosts. By combining such spectroscopic information with Kepler photometry, we will estimate rotation-based ages and examine the age-metallicity relation within the cool subset of Kepler stars, and its implications for chemical evolution models and galactic history. Furthermore, this sample will provide a useful comparison set against stars found to host planets, providing a reference metallicity distribution for use in investigating the planet-metallicity correlation.

Primary contacts

Jennifer van Saders
University of Hawaii
jvansaders -at-

Other contacts

Marc Pinsonneault

Target Selection Details

Stars with photometric data that have log(g) > 4.0 , 7 < Hmag < 11, according to the Kepler Input Catalog (Brown et al. 2011) , and effective temperature < 5500 K, according to Pinsonneault et al. 2012, were targeted. In addition, 48 M dwarfs that have extensive photometric data, but were slightly fainter than H=11, were included in the sample.


Brown et al. 2011, AJ, 142, 112
Pinsonneault et al. 2012, ApJS, 199, 30