Revised Stellar Properties of Kepler Targets for the Quarter 1-16 Transit Detection Run

Abstract: We present revised properties for 196,468 stars observed by the NASA Kepler Mission and used in the analysis of Quarter 1-16 (Q1-Q16) data to detect and characterize transiting exoplanets. The catalog is based on a compilation of literature values for atmospheric properties (temperature, surface gravity, and metallicity) derived from different observational techniques (photometry, spectroscopy, asteroseismology, and exoplanet transits), which were then homogeneously fitted to a grid of Dartmouth stellar isochrones. We use broadband photometry and asteroseismology to characterize 11,532 Kepler targets which were previously unclassified in the Kepler Input Catalog (KIC). We report the detection of oscillations in 2,762 of these targets, classifying them as giant stars and increasing the number of known oscillating giant stars observed by Kepler by ~20% to a total of ~15,500 stars. Typical uncertainties in derived radii and masses are ~40% and ~20%, respectively, for stars with photometric constraints only, and 5-15% and ~10% for stars based on spectroscopy and/or asteroseismology, although these uncertainties vary strongly with spectral type and luminosity class. A comparison with the Q1-Q12 catalog shows a systematic decrease in radii for M dwarfs, while radii for K dwarfs decrease or increase depending on the Q1-Q12 provenance (KIC or Yonsei-Yale isochrones). Radii of F-G dwarfs are on average unchanged, with the exception of newly identified giants. The Q1-Q16 star properties catalog is a first step towards an improved characterization of all Kepler targets to support planet occurrence studies.

• The paper’s main contribution is a comprehensive update of stellar properties, reducing uncertainties in temperature, gravity, and metallicity for Kepler stars.
• It employs diverse methodologies including photometry, spectroscopy, asteroseismology, and isochrone fitting, which notably increased detected oscillating giants by 20%.
• The refined catalog significantly improves exoplanet characterization and stellar evolution analyses by providing more consistent and accurate data.

Revised Stellar Properties of Kepler Targets for the Quarter 1–16 Transit Detection Run

This paper presents a comprehensive revision of the stellar properties for 196,468 stars observed over a span from Quarter 1 to Quarter 16 by NASA's Kepler Mission. The substantial work aimed to update the foundational catalog with more homogenous and precise data. By consolidating existing literature values for atmospheric properties—stellar temperature, surface gravity, and metallicity—derived from photometry, spectroscopy, asteroseismology, and exoplanet transits, the authors fit these to a grid of Dartmouth stellar isochrones to provide recalibrated stellar parameters.

Key Findings and Results

The work covers a significant expansion of stellar classifications, notably identifying additional oscillating giant stars. Specifically, oscillations were detected in 2,762 previously unclassified targets, thereby increasing the number of known oscillating giants by approximately 20%. This addition brings the total to around 15,500 stars. These findings play a crucial role in enhancing our understanding of the planet-hosting potential of these stars. Uncertain classifications previously present in the Kepler Input Catalog (KIC) are significantly mitigated with this update.

The uncertainties in derived stellar parameters such as radii and masses vary considerably based on the methodologies—between approximately 40% and 20% for initial photometric-derived values and decreasing to about 5-15% and ~10% for spectroscopic or asteroseismic determinations. The revision process also addressed systematic overestimates in the KIC for certain spectral classes, indicating a shift in the classification of some M and K dwarfs. These adjustments hold significant implications for exoplanet radius calculations and planetary detection thresholds.

Implications of the Revised Catalog

The revision of the Kepler star properties significantly impacts our understanding of stellar hosts within the Kepler field and directly influences studies on planetary occurrence rates. Accurate stellar parameters are vital, as errors in host star properties could propagate into errors in exoplanetary parameters, leading to misinterpretations in habitability and frequency of Earth-sized planets.

Moreover, the catalog serves as a pivotal resource for understanding the broader stellar population in the galaxy. The homogeneity of cataloging methodologies allows for more consistent comparison across different spectral types and offers a robust data set suitable for both stellar evolution modeling and improving the accuracy of star-planet interpretation.

Future Implications and Directions

While the paper constitutes a significant advancement in standardizing the properties of Kepler targets, further refinements are anticipated with ongoing developments in related fields. Future spectroscopic surveys, like the APOGEE, and advances in photometric calibration will enhance the catalog further, potentially augmenting its accuracy and usability. The anticipated inclusion of additional constraints from proper motion measurements and improved empirical relations will further increase reliability and guidance in stellar studies. Moreover, fine-tuning adjustments to models based on empirical observations, such as granulation time scales' correlations to surface gravity, may offer novel insights into stellar characterization.

In summary, the revised Kepler catalog is an essential advancement seen as foundational groundwork for both existing and future exoplanetary and stellar studies. This revision represents a significant step towards correcting earlier biases and uncertainties, and it will enable a clearer interpretation of Kepler's monumental data set in years to come.