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Speckle Observations of TESS Exoplanet Host Stars. II. Stellar Companions at 1–1000 au and Implications for Small Planet Detection

Lester, Kathryn V. and Matson, Rachel A. and Howell, Steve B. and Furlan, Elise and Gnilka, Crystal L. and Scott, Nicholas J. and Ciardi, David R. and Everett, Mark E. and Hartman, Zachary D. and Hirsch, Lea A. (2021) Speckle Observations of TESS Exoplanet Host Stars. II. Stellar Companions at 1–1000 au and Implications for Small Planet Detection. Astronomical Journal, 162 (2). Art. No. 75. ISSN 0004-6256. doi:10.3847/1538-3881/ac0d06.

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We present high-angular-resolution imaging observations of 517 host stars of TESS exoplanet candidates using the 'Alopeke and Zorro speckle cameras at Gemini North and South. The sample consists mainly of bright F, G, K stars at distances of less than 500 pc. Our speckle observations span angular resolutions of ~20 mas out to 1."2, yielding spatial resolutions of <10–500 au for most stars, and our contrast limits can detect companion stars 5–9 mag fainter than the primary at optical wavelengths. We detect 102 close stellar companions and determine the separation, magnitude difference, mass ratio, and estimated orbital period for each system. Our observations of exoplanet host star binaries reveal that they have wider separations than field binaries, with a mean orbital semimajor axis near 100 au. Other imaging studies have suggested this dearth of very closely separated binaries in systems which host exoplanets, but incompleteness at small separations makes it difficult to disentangle unobserved companions from a true lack of companions. With our improved angular resolution and sensitivity, we confirm that this lack of close exoplanet host binaries is indeed real. We also search for a correlation between planetary orbital radii versus binary star separation; but, given the very short orbital periods of the TESS planets, we do not find any clear trend. We do note that in exoplanet systems containing binary host stars, there is an observational bias against detecting Earth-size planet transits due to transit depth dilution caused by the companion star.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Lester, Kathryn V.0000-0002-9903-9911
Matson, Rachel A.0000-0001-7233-7508
Howell, Steve B.0000-0002-2532-2853
Furlan, Elise0000-0001-9800-6248
Gnilka, Crystal L.0000-0003-2519-6161
Scott, Nicholas J.0000-0003-1038-9702
Ciardi, David R.0000-0002-5741-3047
Everett, Mark E.0000-0002-0885-7215
Hartman, Zachary D.0000-0003-4236-6927
Hirsch, Lea A.0000-0001-8058-7443
Additional Information:© 2021. The American Astronomical Society. Received 2021 April 13; revised 2021 May 31; accepted 2021 June 17; published 2021 July 29. The authors would like to thank the Gemini staff for their help during our observing runs, as well as the anonymous referee for the thoughtful comments. Kathryn Lester's research is supported by an appointment to the NASA Postdoctoral Program at the NASA Ames Research Center administered by Universities Space Research Association under contract with NASA. This work made use of the High-Resolution Imaging instruments 'Alopeke and Zorro, which were funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. 'Alopeke and Zorro were mounted on the Gemini North and South telescopes of the international Gemini Observatory, a program of NSF's NOIRLab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of Maunakea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This work also made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. Facilities: Gemini North ('Alopeke) - , Gemini South (Zorro). - Software: astropy (Astropy Collaboration et al. 2013, 2018), Matplotlib (Hunter 2007), NumPy (Harris et al. 2020), SciPy (Virtanen et al. 2020).
Funding AgencyGrant Number
NASA Postdoctoral ProgramUNSPECIFIED
Gemini PartnershipUNSPECIFIED
Subject Keywords:Speckle interferometry; High angular resolution; Exoplanets; Binary stars
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Speckle interferometry (1552); High angular resolution (2167); Exoplanets (498); Binary stars (154)
Record Number:CaltechAUTHORS:20210813-181157853
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Official Citation:Kathryn V. Lester et al 2021 AJ 162 75
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110244
Deposited By: George Porter
Deposited On:14 Aug 2021 21:58
Last Modified:14 Aug 2021 21:58

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