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A Closer Look at Exoplanet Occurrence Rates: Considering the Multiplicity of Stars without Detected Planets

Savel, Arjun B. and Dressing, Courtney D. and Hirsch, Lea A. and Ciardi, David R. and Fleming, Jordan P. C. and Giacalone, Steven A. and Mayo, Andrew W. and Christiansen, Jessie L. (2020) A Closer Look at Exoplanet Occurrence Rates: Considering the Multiplicity of Stars without Detected Planets. Astronomical Journal, 160 (6). Art. No. 287. ISSN 1538-3881. doi:10.3847/1538-3881/abc47d.

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One core goal of the Kepler mission was to determine the frequency of Earth-like planets that orbit Sun-like stars. Accurately estimating this planet occurrence rate requires both a well-vetted list of planets and a clear understanding of the stars searched for planets. Previous ground-based follow-up observations have, through a variety of methods, sought to improve our knowledge of stars that are known to host planets. Kepler targets without detected planets, however, have not been subjected to the same intensity of follow-up observations. In this paper, we constrain better the stellar multiplicity for stars around which Kepler could have theoretically detected a transiting Earth-sized planet in the habitable zone. We subsequently aim to improve estimates of the exoplanet search completeness—the fraction of exoplanets that were detected by Kepler—with our analysis. By obtaining adaptive optics observations of 71 Kepler target stars from the Shane 3 m telescope at Lick Observatory, we detected 14 candidate stellar companions within 4'' of 13 target stars. Of these 14 candidate stellar companions, we determine through multiple independent methods that 3 are likely to be bound to their corresponding target star. We then assess the impact of our observations on exoplanet occurrence rate calculations, finding an increase in occurrence of 6% (0.9σ) for various estimates of the frequency of Earth-like planets and an increase of 26% (4.5σ) for super-Earths and sub-Neptunes. These occurrence increases are not entirely commensurate with theoretical predictions, though this discrepancy may be due to differences in the treatment of stellar binarity.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Savel, Arjun B.0000-0002-2454-768X
Dressing, Courtney D.0000-0001-8189-0233
Hirsch, Lea A.0000-0001-8058-7443
Ciardi, David R.0000-0002-5741-3047
Fleming, Jordan P. C.0000-0003-4625-9387
Giacalone, Steven A.0000-0002-8965-3969
Mayo, Andrew W.0000-0002-7216-2135
Christiansen, Jessie L.0000-0002-8035-4778
Additional Information:© 2020. The American Astronomical Society. Received 2020 June 12; revised 2020 October 20; accepted 2020 October 23; published 2020 November 26. This research has made use of the NASA Exoplanet Archive and ExoFOP, which are operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (, processed by the Gaia Data Processing and Analysis Consortium (DPAC, Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. A.W.M. is supported by the NSF Graduate Research Fellowship grant no. DGE 1752814. We acknowledge funding support from the Hellman Family Faculty Fund, the Sloan Foundation, and the David and Lucile Packard Foundation. We thank Ellianna S. Abrahams for helpful conversations and insights. We also thank the anonymous reviewer for their thoughtful and detailed comments. Facilities: ADS - , Exoplanet Archive - , Gaia - , Shane (ShARCS infrared camera). - Software: astropy (Price-Whelan et al. 2018), emcee (Foreman-Mackey et al. 2013), IPython (Pérez & Granger 2007), Matplotlib (Hunter 2007), NumPy (Harris et al. 2020), pandas (McKinney et al. 2010), photutils, (Bradley et al. 2019), SciPy (Virtanen et al. 2020), tqdm (da Costa-Luis 2019).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
NSF Graduate Research FellowshipDGE-1752814
Hellman Family Faculty FundUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
David and Lucile Packard FoundationUNSPECIFIED
Subject Keywords:Binary stars ; Near infrared astronomy ; Observational astronomy ; Exoplanet catalogs
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Binary stars (154); Near infrared astronomy (1093); Observational astronomy (1145); Exoplanet catalogs (488)
Record Number:CaltechAUTHORS:20201204-110358079
Persistent URL:
Official Citation:Arjun B. Savel et al 2020 AJ 160 287
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:106918
Deposited By: George Porter
Deposited On:05 Dec 2020 00:44
Last Modified:16 Nov 2021 18:57

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