KEPLER INPUT CATALOG: PHOTOMETRIC CALIBRATION AND STELLAR CLASSIFICATION

By T. Brown, D. Latham, Mark E. Everett, G. Esquerdo. 2011

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We describe the photometric calibration and stellar classification methods used by the Stellar Classification Project to produce the Kepler Input Catalog (KIC). The KIC is a catalog containing photometric and physical data for sources in the Kepler mission field of view; it is used by the mission to select optimal targets. Four of the visible-light (g, r, i, z) magnitudes used in the KIC are tied to Sloan Digital Sky Survey magnitudes; the fifth (D51) is an AB magnitude calibrated to be consistent with Castelli & Kurucz (CK) model atmosphere fluxes. We derived atmospheric extinction corrections from hourly observations of secondary standard fields within the Kepler field of view. For these filters and extinction estimates, repeatability of absolute photometry for stars brighter than magnitude 15 is typically 2%. We estimated stellar parameters {Teff, log (g), log (Z), EB − V} using Bayesian posterior probability maximization to match observed colors to CK stellar atmosphere models. We applied Bayesian priors describing the distribution of solar-neighborhood stars in the color–magnitude diagram, in log (Z), and in height above the galactic plane. Several comparisons with samples of stars classified by other means indicate that for 4500 K ⩽Teff ⩽ 6500 K, our classifications are reliable within about ±200 K and 0.4 dex in log (g) for dwarfs, with somewhat larger log (g) uncertainties for giants. It is difficult to assess the reliability of our log (Z) estimates, but there is reason to suspect that it is poor, particularly at extreme Teff. Comparisons between the CK models and observed colors are generally satisfactory with some exceptions, notably for stars cooler than 4500 K. Of great importance for the Kepler mission, for Teff ⩽ 5400 K, comparison with asteroseismic results shows that the distinction between main-sequence stars and giants is reliable with about 98% confidence. Larger errors in log (g) occur for warmer stars, for which our filter set provides inadequate gravity diagnostics. The KIC is available through the MAST data archive.

Subfields: Astronomy and Astrophysics

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Citations in the corpus

STELLAR AND PLANETARY PROPERTIES OF K2 CAMPAIGN 1 CANDIDATES AND VALIDATION OF 17 PLANETS, INCLUDING A PLANET RECEIVING EARTH-LIKE INSOLATION (2015, background): “We include a prior on stellar metallicity representative of the observed metallicities of stars within 1 kpc of the Sun, following the results of Hayden et al. (2015), and a Salpeter-slope prior on mass up to the maximum mass available in the model grids of M3.”
PLANETARY CANDIDATES FROM THE FIRST YEAR OF THE K2 MISSION (2015, background): “…stellar parameters is difficult for K2 host stars because unlike the original Kepler mission, which had an input catalog produced using uniform and high quality photometry (Brown et al. 2011), K2’s Ecliptic Plane Input Catalog (EPIC7) was compiled from heterogenous sources of archival photometry.”
The Revised TESS Input Catalog and Candidate Target List (2019, background): “…from broadband photometry (and spectroscopy in a tiny minority of cases) on the basis of a complex set of logic rules, algorithms, and empirical relations (see also Brown et al. 2011; Huber et al. 2016; Berger et al. 2018; Deacon et al. 2019) customized for the TESS bandpass (Stassun et al. 2018).”
Optimized transit detection algorithm to search for periodic transits of small planets (2019, background): “The KIC and EPIC catalogs (Brown et al. 2011; Huber et al. 2016) typically have relative mass and radius uncertainties of 5 %, so that a range of ±0.1 ρ (±0.2 ρ) gives a 2σ (4σ) confidence interval.”
REVEALING A UNIVERSAL PLANET–METALLICITY CORRELATION FOR PLANETS OF DIFFERENT SIZES AROUND SOLAR-TYPE STARS (2013, methodology): “Similarly, for Teff and log(g), we also found a positive correlation between SPC and KIC values, Teff,SPC = 1194 + 0.78 × Teff,KIC, and log(g)SPC = 1.97 + 0.54 × log(g) SPC, respectively.”
SOPHIE velocimetry of Kepler transit candidates XVII. The physical properties of giant exoplanets within 400 days of period (2015, methodology): “Note that Wang & Fischer (2015) proposed a correction of the metallicities from the Kepler input catalog (Brown et al. 2011) using the spectroscopic data from Buchhave et al. (2014).”
The California-Kepler Survey. I. High-resolution Spectroscopy of 1305 Stars Hosting Kepler Transiting Planets (2017, methodology): “Huber et al. (2014) Huber et al. (2014) provided a comprehensive update to the KIC by compiling literature measurements of stellar properties from different observational techniques (photometry, spectroscopy, asteroseismology, and exoplanet transits) and homogeneously fitting them to a grid of Dartm”
Characterization of the power excess of solar-like oscillations in red giants with Kepler (2011, methodology): “The variation of V 21 with metallicity shows no significant correlation, but this result may be due to the very uncertain metallicity determinations in the Kepler Input Catalog.”
LARGER PLANET RADII INFERRED FROM STELLAR “FLICKER” BRIGHTNESS VARIATIONS OF BRIGHT PLANET-HOST STARS (2014, methodology): “This is the most efficient method for estimating stellar parameters, but with uncertainties in log g of 0.35– 0.6 dex (Brown et al. 2011).”
CHARACTERIZING THE COOL KOIs. IV. KEPLER-32 AS A PROTOTYPE FOR THE FORMATION OF COMPACT PLANETARY SYSTEMS THROUGHOUT THE GALAXY (2012, methodology): “It was originally listed in the Kepler Input Catalog (KIC) with an effective temperature of 3911K, below the 4500K threshold where the photometric method for determining stellar parameters is deemed reliable (Brown et al. 2011).”
DENSITY AND ECCENTRICITY OF KEPLER PLANETS (2012, background): “The first group are stars that are hotter than 5400 K – their stellar log g values from KIC (Brown et al. 2011) are fairly uncertain as these stars can be subgiants impersonating main-sequence stars.”
THE OCCURRENCE RATE OF SMALL PLANETS AROUND SMALL STARS (2013, methodology): “In this paper, we characterize the coolest Kepler target stars by revisiting the approach used to create the Kepler Input Catalog (Brown et al. 2011) and tailoring that method for application to cool stars.”
Target Selection for the SDSS-IV APOGEE-2 Survey (2017, methodology): “The non-host “control sample” was drawn from the Kepler Input Catalog (Brown et al. 2011), using the same H < 14 magnitude limit and selected to provide the same Teff–log g joint density distribution as in the host+KOI sample.”
THE APOGEE RED-CLUMP CATALOG: PRECISE DISTANCES, VELOCITIES, AND HIGH-RESOLUTION ELEMENTAL ABUNDANCES OVER A LARGE AREA OF THE MILKY WAY'S DISK (2014, methodology): “The APOKASC asteroseismic analysis uses spectroscopic Teff from APOGEE rather than Teff from the Kepler Input Catalog (Brown et al. 2011).”
STELLAR ROTATION PERIODS OF THE KEPLER OBJECTS OF INTEREST: A DEARTH OF CLOSE-IN PLANETS AROUND FAST ROTATORS (2013, methodology): “The mass range (from KIC Teff using stellar evolution models of Baraffe et al. 1998) covered in this periodic sample is 0.3 – 1.5M⊙, leading to a wide range of spin-down rates.”
The connection between stellar granulation and oscillation as seen by the Kepler mission (2014, methodology): “Effective temperatures are taken from the Kepler Input Catalog (KIC; Brown et al. 2011) and corrected according to Thygesen et al. (2012).”
Asteroseismology of 16,000 Kepler Red Giants: Global Oscillation Parameters, Masses, and Radii (2018, background): “…analysis are believed to be more precise (∼ 2%, Hekker et al. 2013b), compared to the time scale technique (∼ 4%, Kallinger et al. 2016), the 8 hr “flicker” method (∼ 25%, Bastien et al. 2013), spectroscopy (∼ 50%, Valenti & Fischer 2005), and photometric colors (∼ 100%, Brown et al. 2011).”