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Planetary candidates transiting cool dwarf stars from campaigns 12 to 15 of K2

Castro González, A. and Díez Alonso, E. and Menéndez Blanco, J. and Livingston, John H. and de Leon, Jerome P. and Suárez Gómez, S. L. and González Gutiérrez, C. and García Riesgo, F. and Bonavera, L. and Iglesias Rodríguez, F. J. and Muñiz, R. and Everett, Mark E. and Scott, N. and Howell, Steve B. and Ciardi, David R. and Gonzales, Erica J. and Schlieder, Joshua E. and de Cos Juez, F. J. (2020) Planetary candidates transiting cool dwarf stars from campaigns 12 to 15 of K2. Monthly Notices of the Royal Astronomical Society, 499 (4). pp. 5416-5441. ISSN 0035-8711. doi:10.1093/mnras/staa2353.

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We analysed the photometry of 20 038 cool stars from campaigns 12, 13, 14, and 15 of the K2 mission in order to detect, characterize, and validate new planetary candidates transiting low-mass stars. We present a catalogue of 25 new periodic transit-like signals in 22 stars, of which we computed the parameters of the stellar host for 19 stars and the planetary parameters for 21 signals. We acquired speckle and AO images, and also inspected archival Pan-STARRS1 images and Gaia DR2 to discard the presence of close stellar companions and to check possible transit dilutions due to nearby stars. False positive probability (FPP) was computed for 22 signals, obtaining FPP < 1 per cent for 17. We consider 12 of them as statistically validated planets. One signal is a false positive and the remaining 12 signals are considered as planet candidates. 20 signals have an orbital period of P_(orb) < 10 d⁠, 2 have 10 d < P_(orb) < 20 d⁠, and 3 have P_(orb) > 20 d⁠. Regarding radii, 11 candidates and validated planets have computed radius R < 2R_⊕, 9 have 2R⊕ < R < 4R_⊕, and 1 has R > 4R_⊕. Two validated planets and two candidates are located in moderately bright stars (⁠m_(kep) < 13 and two validated planets and three candidates have derived orbital radius within the habitable zone according to optimistic models. Of special interest is the validated warm super-Earth K2-323 b (EPIC 248616368 b) with T_(eq) = 318⁺²⁴₋₄₃⁠, S_p = 1.7±0.2 S_⊕⁠, and R_p = 2.1±0.1, located in an m_(kep)= 14.13 star.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Livingston, John H.0000-0002-4881-3620
Everett, Mark E.0000-0002-0885-7215
Howell, Steve B.0000-0002-2532-2853
Ciardi, David R.0000-0002-5741-3047
Gonzales, Erica J.0000-0002-9329-2190
Schlieder, Joshua E.0000-0001-5347-7062
Additional Information:© 2020 The Author(s). Published by Oxford University Press on behalf of the Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model ( Accepted 2020 July 24. Received 2020 June 26; in original form 2019 December 17. Published: 05 November 2020. ACG, EDA, SLSG, CGG, FGR, and JCJ would like to acknowledge Spanish ministry project MINECO AYA2017-89121-Pystems. LB acknowledges financial support from the PGC 2018 project PGC2018-101948-B-I00 (MICINN and FEDER). This paper includes data collected by the Kepler mission and obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the Kepler mission is provided by the NASA Science Mission Directorate. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. The Pan-STARRS1 Surveys (PS1) and the PS1 public science archive have been made possible through contributions by the Institute for Astronomy, the University of Hawaii, the Pan-STARRS Project Office, the Max-Planck Society and its participating institutes, the Max Planck Institute for Astronomy, Heidelberg and the Max Planck Institute for Extraterrestrial Physics, Garching, The Johns Hopkins University, Durham University, the University of Edinburgh, the Queen’s University Belfast, the Harvard-Smithsonian Center for Astrophysics, the Las Cumbres Observatory Global Telescope Network Incorporated, the National Central University of Taiwan, the Space Telescope Science Institute, the National Aeronautics and Space Administration under Grant No. NNX08AR22G issued through the Planetary Science Division of the NASA Science Mission Directorate, the National Science Foundation Grant No. AST-1238877, the University of Maryland, Eotvos Lorand University (ELTE), the Los Alamos National Laboratory, and the Gordon and Betty Moore Foundation. This research has made use of the Exoplanet Follow-up Observation Programme website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Programme. This research has made use of the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Programme. 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. The Digitized Sky Surveys were produced at the Space Telescope Science Institute under U.S. Government grant NAG W-2166. The images of these surveys are based on photographic data obtained using the Oschin Schmidt Telescope on Palomar Mountain and the UK Schmidt Telescope. The plates were processed into the present compressed digital form with the permission of these institutions. Some of the observations in the paper made use of the NN-EXPLORE Exoplanet and Stellar Speckle Imager (NESSI). NESSI was funded by the NASA Exoplanet Exploration Programme and the NASA Ames Research Center. NESSI was built at the Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. We thank Joaquin González-Nuevo for useful discussions. Data Availability: The data underlying this article will be shared on reasonable request to the corresponding author.
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Ministerio de Economía, Industria y Competitividad (MINECO)AYA2017-89121-Pystems
Ministerio de Ciencia e Innovación (MCINN)PGC2018-101948-B-I00
Fondo Europeo de Desarrollo Regional (FEDER)UNSPECIFIED
NASANAS 5-26555
University of MarylandUNSPECIFIED
Eotvos Lorand University (ELTE)UNSPECIFIED
Los Alamos National LaboratoryUNSPECIFIED
Gordon and Betty Moore FoundationUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:methods: data analysis – techniques: photometric – planets and satellites: detection – stars: low mass – techniques: image processing.
Issue or Number:4
Record Number:CaltechAUTHORS:20200818-070220300
Persistent URL:
Official Citation:A Castro González, E Díez Alonso, J Menéndez Blanco, John H Livingston, Jerome P de Leon, S L Suárez Gómez, C González Gutiérrez, F García Riesgo, L Bonavera, F J Iglesias Rodríguez, R Muñiz, Mark E Everett, N J Scott, Steve B Howell, David R Ciardi, Erica J Gonzales, Joshua E Schlieder, F J de Cos Juez, Planetary candidates transiting cool dwarf stars from campaigns 12 to 15 of K2, Monthly Notices of the Royal Astronomical Society, Volume 499, Issue 4, December 2020, Pages 5416–5441,
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:104986
Deposited By: Tony Diaz
Deposited On:18 Aug 2020 15:36
Last Modified:16 Nov 2021 18:38

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