Flicker as a Tool for Characterizing Planets Through Asterodensity Profiling
Abstract
Variability in the time series brightness of a star on a timescale of 8 hr, known as "flicker," has been previously demonstrated to serve as a proxy for the surface gravity of a star by Bastien et al. Although surface gravity is crucial for stellar classification, it is the mean stellar density that is most useful when studying transiting exoplanets, due to its direct impact on the transit light curve shape. Indeed, an accurate and independent measure of the stellar density can be leveraged to infer subtle properties of a transiting system, such as the companion's orbital eccentricity via asterodensity profiling (AP). We here calibrate flicker to the mean stellar density of 439 Kepler targets with asteroseismology, allowing us to derive a new empirical relation given by log_{10}(ρ_{sstarf} (kg m^{3})) = 5.413  1.850log_{10}(F _{8} (ppm)). The calibration is valid for stars with 4500 < T _{eff} < 6500 K, K_{P} < 14, and flicker estimates corresponding to stars with 3.25 < log g _{sstarf} < 4.43. Our relation has a model error in the stellar density of 31.7% and so has ~8 times lower precision than that from asteroseismology but is applicable to a sample ~40 times greater. Flicker therefore provides an empirical method to enable AP on hundreds of planetary candidates from present and future missions.
 Publication:

The Astrophysical Journal
 Pub Date:
 April 2014
 DOI:
 10.1088/20418205/785/2/L32
 arXiv:
 arXiv:1403.5264
 Bibcode:
 2014ApJ...785L..32K
 Keywords:

 planetary systems;
 stars: activity;
 stars: solartype;
 techniques: photometric;
 Astrophysics  Earth and Planetary Astrophysics;
 Astrophysics  Solar and Stellar Astrophysics
 EPrint:
 6 pages, 3 figures, 1 table. Accepted to ApJ Letters. Code available at https://www.cfa.harvard.edu/~dkipping/flicker.html