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Hot Stars with Kepler Planets Have High Obliquities

Louden, Emma M. and Winn, Joshua N. and Petigura, Erik A. and Isaacson, Howard and Howard, Andrew W. and Masuda, Kento and Albrecht, Simon and Kosiarek, Molly R. (2021) Hot Stars with Kepler Planets Have High Obliquities. Astronomical Journal, 161 (2). Art. No. 68. ISSN 1538-3881. https://resolver.caltech.edu/CaltechAUTHORS:20210208-101412864

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Abstract

It has been known for a decade that hot stars with hot Jupiters tend to have high obliquities. Less is known about the degree of spin–orbit alignment for hot stars with other kinds of planets. Here, we reassess the obliquities of hot Kepler stars with transiting planets smaller than Neptune, based on spectroscopic measurements of their projected rotation velocities (ν sin i). The basis of the method is that a lower obliquity—all other things being equal—causes sin i to be closer to unity and increases the value of ν sin i. We sought evidence for this effect using a sample of 150 Kepler stars with effective temperatures between 5950 and 6550 K and a control sample of 101 stars with matching spectroscopic properties and random orientations. The planet hosts have systematically higher values of ν sin i than the control stars, but not by enough to be compatible with perfect spin–orbit alignment. The mean value of sin i is 0.856 ± 0.036, which is 4σ away from unity (perfect alignment), and 2σ away from π/4 (random orientations). There is also evidence that the hottest stars have a broader obliquity distribution: when modeled separately, the stars cooler than 6250 K have〈sin i〉= 0.928 ± 0.042 while the hotter stars are consistent with random orientations. This is similar to the pattern previously noted for stars with hot Jupiters. Based on these results, obliquity excitation for early-G and late-F stars appears to be a general outcome of star and planet formation, rather than being exclusively linked to hot Jupiter formation.


Item Type:Article
Related URLs:
URLURL TypeDescription
https://doi.org/10.3847/1538-3881/abcebdDOIArticle
https://arxiv.org/abs/2012.00776arXivDiscussion Paper
ORCID:
AuthorORCID
Winn, Joshua N.0000-0002-4265-047X
Petigura, Erik A.0000-0003-0967-2893
Isaacson, Howard0000-0002-0531-1073
Howard, Andrew W.0000-0001-8638-0320
Masuda, Kento0000-0003-1298-9699
Albrecht, Simon0000-0003-1762-8235
Kosiarek, Molly R.0000-0002-6115-4359
Additional Information:© 2021 The American Astronomical Society. Received 2020 August 31; revised 2020 November 18; accepted 2020 November 28; published 2021 January 14. The data presented herein were obtained at the W. M. Keck Observatory, which is operated as a scientific partnership among the California Institute of Technology, the University of California, and the National Aeronautics and Space Administration. The Observatory was made possible by the generous financial support of the W. M. Keck Foundation. We are grateful to the anonymous referee for a helpful critique of the manuscript, and to Subo Dong for providing the LAMOST data in a convenient format. J.N.W. thanks the members of the Princeton exoplanet discussion group and Heather Knutson's group for useful feedback, and Geoff Marcy for input at the outset of this project. J.N.W. also acknowledges support from a NASA Keck PI Data Award, administered by the NASA Exoplanet Science Institute. S.A. acknowledges support from the Danish Council for Independent Research through the DFF Sapere Aude Starting Grant No. 4181-00487B, and the Stellar Astrophysics Centre for which funding is provided by The Danish National Research Foundation (Grant agreement no. DNRF106). M.R.K. is supported by the NSF Graduate Research Fellowship grant No. DGE 1339067. This work made use of data from the LAMOST (Guoshoujing) Telescope, a National Major Scientific Project built by the Chinese Academy of Sciences, for which funding was provided by the National Development and Reform Commission. LAMOST is operated and managed by the National Astronomical Observatories, Chinese Academy of Sciences. We 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. Facilities: Keck:I (HIRES) - , LAMOST. -
Group:Astronomy Department
Funders:
Funding AgencyGrant Number
W. M. Keck FoundationUNSPECIFIED
Danish Council for Independent Research4181-00487B
Danish National Research FoundationDNRF106
NSF Graduate Research FellowshipDGE-1339067
National Development and Reform CommissionUNSPECIFIED
National Astronomical Observatories, Chinese Academy of SciencesUNSPECIFIED
Subject Keywords:Exoplanets ; Stellar rotation
Issue or Number:2
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanets (498); Stellar rotation (1629)
Record Number:CaltechAUTHORS:20210208-101412864
Persistent URL:https://resolver.caltech.edu/CaltechAUTHORS:20210208-101412864
Official Citation:Emma M. Louden et al 2021 AJ 161 68
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:107946
Collection:CaltechAUTHORS
Deposited By: Tony Diaz
Deposited On:08 Feb 2021 18:40
Last Modified:08 Feb 2021 18:40

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