The Kepler Follow-Up Observation Program. I. A Catalog of Companions to Kepler Stars From High-Resolution Imaging

Abstract

We present results from high-resolution, optical to near-IR imaging of host stars of Kepler Objects of Interest (KOIs), identified in the original Kepler field. Part of the data were obtained under the Kepler imaging follow-up observation program over six years (2009)(2010)(2011)(2012)(2013)(2014)(2015). Almost 90% of stars that are hosts to planet candidates or confirmed planets were observed. We combine measurements of companions to KOI host stars from different bands to create a comprehensive catalog of projected separations, position angles, and magnitude differences for all detected companion stars (some of which may not be bound). Our compilation includes 2297 companions around 1903 primary stars. From high-resolution imaging, we find that ∼10% (∼30%) of the observed stars have at least one companion detected within 1″ (4″). The true fraction of systems with close (4″) companions is larger than the observed one due to the limited sensitivities of the imaging data. We derive correction factors for planet radii caused by the dilution of the transit depth: assuming that planets orbit the primary stars or the brightest companion stars, the average correction factors are 1.06 and 3.09, respectively. The true effect of transit dilution lies in between these two cases and varies with each system. Applying these factors to planet radii decreases the number of KOI planets with radii smaller than 2 Å R by ∼2%-23% and thus affects planet occurrence rates. This effect will also be important for the yield of small planets from future transit missions such as TESS.

Average Albedos of Close-in Super-Earths and Super-Neptunes from Statistical Analysis of Long-cadence Kepler Secondary Eclipse Data

“…(Thus an albedo of 0.10 would be inferred as 0.096). However, adopting a one-third companion fraction somewhat exaggerates the effect: The compilation of high-resolution imaging by Furlan et al (2017) shows companions associated with only 10 of 40 stars in our shortened 1 to 2 R ⊕ group, less than the onethird from Hirsch et al (2017). Therefore this source of bias is not important for our results, and that is also true for our other planet groups, which have similar companion rates.…”

“…Therefore this source of bias is not important for our results, and that is also true for our other planet groups, which have similar companion rates. Furthermore, we conclude that dilution does not have a significant effect on which radius bin the candidates fall in, because the radius correction factors in Furlan et al (2017) suggest that only 1 candidate (KOI-2797.01) in the 1 to 2 R ⊕ bin would move up to the larger 2 to 4 R ⊕ group, while 2 of the 2 to 4 R ⊕ candidates would move up to the larger 4 to 6 R ⊕ group, and 3 members of the 4 to 6 R ⊕ group are over 6 R ⊕ by only a few percent.…”

The California-Kepler Survey. V. Peas in a Pod: Planets in a Kepler Multi-planet System Are Similar in Size and Regularly Spaced*

“…From these, we discarded the known false positives, removing 59 nonplanetary signals as determined in CKS I. We then discarded stars that were diluted by at least 5% by a second star in the Kepler aperture (as determined in the stellar companion catalog of Furlan et al 2017), removing 30 stars hosting 69 planet candidates. We discarded planets for which Mullally et al (2015) measured b>0.9, for which the high impact parameters adversely affected our ability to determine accurate planet radii, removing 75 planet candidates.…”

KELT-20b: A Giant Planet with a Period of P ∼ 3.5 days Transiting the V ∼ 7.6 Early A Star HD 185603

“…09  (FWHM). The sensitivity of the AO data was determined by injecting simulated sources into the final combined images with separations from the primary targets in integer multiples of the central source's FWHM (Furlan et al 2017). The sensitivity curve shown in Figure 4 represents the 5σ limits of the imaging data.…”