Understanding the effects of stellar multiplicity on the derived planet radii from transit surveys: implications for Kepler, K2, and TESS

Ciardi, David R. and Beichman, Charles A. and Horch, Elliott P. and Howell, Steve B. (2015) Understanding the effects of stellar multiplicity on the derived planet radii from transit surveys: implications for Kepler, K2, and TESS. The Astrophysical Journal, 805 (1). pp. 1-9. ISSN 0004-637X

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We present a study on the effect of undetected stellar companions on the derived planetary radii for Kepler Objects of Interest (KOIs). The current production of the KOI list assumes that each KOI is a single star. Not accounting for stellar multiplicity statistically biases the planets toward smaller radii. The bias toward smaller radii depends on the properties of the companion stars and whether the planets orbit the primary or the companion stars. Defining a planetary radius correction factor, XR, we find that if the KOIs are assumed to be single, then, on average, the planetary radii may be underestimated by a factor of 〈XR〉 ≈ 1.5. If typical radial velocity and high-resolution imaging observations are performed and no companions are detected, then this factor reduces to 〈XR〉 ≈ 1.2. The correction factor 〈XR〉 is dependent on the primary star properties and ranges from 〈XR〉 ≈ 1.6 for A and F stars to 〈XR〉 ≈ 1.2 for K and M stars. For missions like K2 and TESS where the stars may be closer than the stars in the Kepler target sample, observational vetting (primary imaging) reduces the radius correction factor to 〈XR〉 ≈ 1.1. Finally, we show that if the stellar multiplicity rates are not accounted for correctly, then occurrence rate calculations for Earth-sized planets may overestimate the frequency of small planets by as much as 15%-20%.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Additional Information: Access to published version in accordance with the copyright policy of the publisher.
Faculty/School / Institute/Centre: Current - USQ Other
Faculty/School / Institute/Centre: Current - USQ Other
Date Deposited: 26 May 2017 06:20
Last Modified: 07 Mar 2018 01:09
Uncontrolled Keywords: binaries: general; planetary systems
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Identification Number or DOI: https://doi.org/10.1088/0004-637X/805/1/16
URI: http://eprints.usq.edu.au/id/eprint/32438

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