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Ultra-short-period Planets in K2. III. Neighbors are Common with 13 New Multiplanet Systems and 10 Newly Validated Planets in Campaigns 0–8 and 10

Adams, Elisabeth R. and Jackson, Brian and Johnson, Samantha and Ciardi, David R. and Cochran, William D. and Endl, Michael and Everett, Mark E. and Furlan, Elise and Howell, Steve B. and Jayanthi, Prasanna and MacQueen, Phillip J. and Matson, Rachel A. and Partyka-Worley, Ciera and Schlieder, Joshua and Scott, Nicholas J. and Stanton, Sevio M. and Ziegler, Carl (2021) Ultra-short-period Planets in K2. III. Neighbors are Common with 13 New Multiplanet Systems and 10 Newly Validated Planets in Campaigns 0–8 and 10. Planetary Science Journal, 2 (4). Art. No. 152. ISSN 2632-3338. doi:10.3847/PSJ/ac0ea0.

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Using the EVEREST photometry pipeline, we have identified 74 candidate ultra-short-period planets (USPs; orbital period P < 1 day) in the first half of the K2 data (Campaigns 0–8 and 10). Of these, 33 candidates have not previously been reported. A systematic search for additional transiting planets found 13 new multiplanet systems containing a USP, doubling the number known and representing a third (32%) of USPs in our sample from K2. We also identified 30 companions, which have periods from 1.4 to 31 days (median 5.5 days). A third (36 of 104) of the candidate USPs and companions have been statistically validated or confirmed in this work, 10 for the first time, including 7 USPs. Almost all candidates, and all validated planets, are small (radii R_p ≤ 3 R_⊕) with a median radius of R_p = 1.1 R_⊕; the validated and confirmed USP candidates have radii between 0.4 R_⊕ and 2.4 R_⊕ and periods from P = 0.18 to 0.96 days. The lack of candidate (a) ultra-hot-Jupiter (R_p > 10 R_⊕) and (b) short-period-desert (3 ≤ R_p ≤ 10 R_⊕) planets suggests that both populations are rare, although our survey may have missed some of the very deepest transits. These results also provide strong evidence that we have not reached a lower limit on the distribution of planetary radius values for planets at close proximity to a star and suggest that additional improvements in photometry techniques would yield yet more USPs. The large fraction of USPs in known multiplanet systems supports origins models that involve dynamical interactions with exterior planets coupled to tidal decay of the USP orbits.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper ItemData products
Adams, Elisabeth R.0000-0002-9131-5969
Jackson, Brian0000-0002-9495-9700
Ciardi, David R.0000-0002-5741-3047
Cochran, William D.0000-0001-9662-3496
Endl, Michael0000-0002-7714-6310
Everett, Mark E.0000-0002-0885-7215
Furlan, Elise0000-0001-9800-6248
Howell, Steve B.0000-0002-2532-2853
Matson, Rachel A.0000-0001-7233-7508
Schlieder, Joshua0000-0001-5347-7062
Scott, Nicholas J.0000-0003-1038-9702
Ziegler, Carl0000-0002-0619-7639
Alternate Title:Ultra Short Period Planets in K2 III: Neighbors are Common with 12 New Multi-Planet Systems and 26 Newly Validated Planets in Campaigns 0-8, 10, Ultra Short Period Planets in K2 III: Neighbors are Common with 13 New Multi-Planet Systems and 10 Newly Validated Planets in Campaigns 0-8, 10
Additional Information:© 2021. The Author(s). Original content from this work may be used under the terms of the Creative Commons Attribution 4.0 licence. Any further distribution of this work must maintain attribution to the author(s) and the title of the work, journal citation and DOI. Received 2020 November 19; revised 2021 May 14; accepted 2021 May 19; published 2021 August 6. Data products produced as part of this work, including the transit light curves and fitting images, are available at our repository at Thanks to Rodrigo Luger, Tim Morton, Katja Poppenhaeger, Joe Renaud, Ethan Kruse, and Dan Foreman-Mackey for helpful discussions during the preparation of this manuscript. The two anonymous reviewers also greatly improved the quality of this paper and their thorough reviews are much appreciated. 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. This research made use of lightkurve, a Python package for Kepler and TESS data analysis (Barentsen et al. 2019); Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013, 2018); Scipy (Virtanen et al. 2020); PyMC (Salvatier et al. 2016); Batman (Kreidberg 2015); and Matplotlib (Hunter 2007). This study is based upon work supported by NASA under grant No. NNX15AB78G issued through the Astrophysical Data Analysis Program by Science Mission Directorate and under grant No. NNX17AB94G through the Exoplanets Research Program. M.E. and W.D.C. were supported by NASA K2 Guest Observer grants NNX15AV58G, NNX16AE70G, and NNX16AE58G to The University of Texas at Austin. This research was supported in part by the National Science Foundation under grant No. NSF PHY-1748958 under the auspices of UC Santa Barbara's Kavli Institute for Theoretical Physics. Some of the data analyzed in this paper were collected by the K2 mission, funding for which is provided by the NASA Science Mission Directorate. The data were obtained from the Mikulski Archive for Space Telescopes (MAST). STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS5-26555. Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX09AF08G and by other grants and contracts. Some of 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. 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. Facility: Kepler, Keck:II (NIRC2), Gemini:South, Gemini:Gillett, SOAR, Hale, WIYN. Software: Batman 2.1.0 (Kreidberg 2015); pymodelfit 0.1.2 (Tollerud 2011); PyMC 2.3.4 (Fonnesbeck et al. 2015); PyLightCurve 2.3.2 (Tsiaras et al. 2016); Emcee 2.2.1 (Foreman-Mackey et al. 2013); Kea (Endl & Cochran 2016), Uncertainties, vespa 0.4.9 (Morton 2012); astropy 3.1.1 (Astropy Collaboration et al. 2013, 2018); scipy 1.2.1 (Virtanen et al. 2020); matplotlib 3.0.2 (Hunter 2007)
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Gaia Multilateral AgreementUNSPECIFIED
W. M. Keck FoundationUNSPECIFIED
Subject Keywords:Transit photometry; Exoplanet catalogs; Exoplanet formation; Exoplanet evolution
Issue or Number:4
Classification Code:Unified Astronomy Thesaurus concepts: Transit photometry (1709); Exoplanet catalogs (488); Exoplanet formation (492); Exoplanet evolution (491)
Record Number:CaltechAUTHORS:20210813-181203178
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Official Citation:Elisabeth R. Adams et al 2021 Planet. Sci. J. 2 152
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110256
Deposited By: George Porter
Deposited On:13 Aug 2021 23:21
Last Modified:18 Aug 2021 18:49

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