Kepler Object of Interest (KOI) Catalog - Q1-Q8

First delivery date: Jan. 7, 2013
Last delivery date: Jan. 7, 2014
Status: done

Contents

  1. Triage of Q1-Q8 TCEs for new KOIs
  2. Vetting of Q1-Q8 KOIs
  3. Stellar and Planet Parameters
  4. Activity Table Advisory

1. Triage of Q1-Q8 TCEs for new KOIs

An instance of the SOC 7.0 Kepler pipeline code base was run on the Q1-Q8 data set to empirically determine the noise in the flux time series - the so-called Combined Differential Photometric Precision (CDPP; Christiansen et al. 2012) - and search for potential planet candidates (Jenkins 2002). Potential planet candidates delivered by the Kepler pipeline are termed Threshold Crossing Events (TCEs; Tenenbaum et al. 2012). The Multiple Event Statistic (MES) is defined as the combined signal-to-noise ratio (SNR) from multiple transit events in a Kepler light curve. For a transit-like signal in the Q1-Q8 data to be defined as a TCE, its MES must exceeed 7.1σ. In addition, a TCE transit signal must have a ratio of the MES to the strongest single transit event SNR greater than √2. These criteria for defining a TCE are specific to the SOC 7.0 version of the Kepler pipeline code and differ in different versions of the code.

Each TCE is designated by the target hosting the potential planet candidate and its orbital ephemeris. For the Q1-Q8 pipeline run, one or more TCEs were generated for approximately 13,400 Kepler targets. A majority of the TCEs are not valid planet candidates; most are induced by uncorrected instrumental instabilities or astrophysical variability within the photometric pixel aperture. The Photometric Analysis (PA) flux time series (Fanelli et al. 2011, Thompson and Fraquelli 2012) is median detrended with a moving window of two-day duration and the resulting relative flux time series is phase folded on the TCE ephemeris. TCEs in this phase-folded form are assessed visually for their potential as planet candidates. During this "triage" stage, 480 promising new signatures were identified and assigned KOI numbers (KOIs 2669-3148).

2. Vetting of Q1-Q8 KOIs

The purpose of vetting is to disposition KOIs into planet candidates and false positives using diagnostic information extracted from the Kepler data. KOI vetting examines the Kepler flux time series data for consistency with the expectation of a transiting planet signal and the Kepler pixel-level time series data for consistency with the expectation that the signal originates from the target of interest in the aperture. The vetting process follows the procedures outlined in Batalha et al. (2013). The vetting updates to the KOI catalog presented here result from two groups of Kepler targets. The first group are new KOI targets that were identified in the SOC 7.0 pipeline run with Q1-Q8 data (KOIs 2669-3148). The second group are a re-vetting of KOIs (≤1609) from the first two Kepler planet candidate catalogs (Borucki et al. 2011a and Borucki et al. 2011b) in order to take advantage of the substantially increased data baseline, pipeline maturity and the more developed vetting methods of Batalha et al. (2013). The intermediate range (KOIs 1610-2668) were recently vetted by Batalha et al. (2013) and were not revisited.

Vetting diagnostics provided in this KOI table are extracted from a subsequent pipeline run using Q1-Q10 data and SOC 8.2 pipeline code, taking advantage of the longer baseline and additional pipeline algorithm development after Q8. We also vetted any new TCEs that were found by the Q1-Q10 pipeline run around previously existing KOIs in the ranges 1-1609, 2669-3148.

KOI vetting is primarily conducted using a standardized one-page report summary that is generated in the Data Validation (DV) module of the pipeline (Fanelli et al. 2011). The report summarizes the Kepler flux time series and pixel-level data tests most relevant for dispositioning a KOI into one of three categories: planet candidate (PC), inconclusive (blank), or false positive (FP). Most targets were dispositioned using the standard DV one page summary, some required the full DV report analysis, and a few underwent additional scrutiny using offline data analysis when the standard data products were inconclusive.

3. Stellar and Planet Parameters

A majority of the KOI stellar parameters in this catalog are modified from the Kepler Input Catalog (KIC) (Brown et al. 2011; Batalha et al. 2012). For some Kepler targets, the stellar radius derived from the combination of KIC effective temperature (Teff), surface density (logg) and metallicity ([Fe/H]) is inconsistent with theoretical stellar evolution calculations. The stellar parameters adopted for transit model fits to the data were revised to be consistent with the Yale-Yonsei stellar isochrones (Demarque et al. 2004) as described in Batalha et al. (2013) and the Q1-Q12 TCE release notes. Additionally, some targets have stellar parameters based upon ground based high-resolution spectroscopy taken as part of the Kepler Follow-up Observation Program (Valenti and Fischer 2005; Buchhave et al. 2012). Planetary parameters are based upon fitting the Mandel & Agol (2002) transit model to the Q1-Q10 Kepler flux time series data. All KOIs 1-3148 are fit. The Kepler aperture photometry output from PA is median detrended before fitting the model using the Levenberg-Marquardt minimization routine. The resulting error bars represent statistical uncertainty based upon the diagonal elements of the numerical covariance matrix estimated at the best fit parameters. The errors do not include the systematic uncertainties that results from the uncertainties in the stellar parameters.

4. Activity Table Advisory

This KOI activity table comes with important caveats:
  1. The table is not suitable for statistical population studies because it is not an exhaustive reporting of all the planet candidates from the Kepler pipeline runs under investigation.
  2. All table entries are subject to change until the table is designated as 'closed'.
  3. As of January 7, 2014, the Kepler project has closed the KOI activity table for Q1-Q8. Therefore, no further changes will be made to the data set. For more information, see the associated paper (Burke et al 2013).
The Q1-Q8 table does however provide a well vetted catalog of individual candidates and multiple planet systems that are worthy of follow up observations and scientific study.