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Scaling K2. V. Statistical Validation of 60 New Exoplanets From K2 Campaigns 2–18

Christiansen, Jessie L. and Bhure, Sakhee and Zink, Jon K. and Hardegree-Ullman, Kevin K. and Adkins, Britt Duffy and Hedges, Christina and Morton, Timothy D. and Bieryla, Allyson and Ciardi, David R. and Cochran, William D. and Dressing, Courtney D. and Everett, Mark E. and Isaacson, Howard and Livingston, John H. and Ziegler, Carl and Berlind, Perry and Calkins, Michael L. and Esquerdo, Gilbert A. and Latham, David W. and Endl, Michael and MacQueen, Phillip J. and Fulton, Benjamin J. and Hirsch, Lea A. and Howard, Andrew W. and Weiss, Lauren M. and Allen, Bridgette E. and Berberyann, Arthur and Ciardi, Krys N. and Dunlavy, Ava and Glassford, Sofia H. and Dai, Fei and Hirano, Teruyuki and Tamura, Motohide and Beichman, Charles and Gonzales, Erica J. and Schlieder, Joshua E. and Barclay, Thomas and Crossfield, Ian J. M. and Gilbert, Emily A. and Matthews, Elisabeth C. and Giacalone, Steven and Petigura, Erik A. (2022) Scaling K2. V. Statistical Validation of 60 New Exoplanets From K2 Campaigns 2–18. Astronomical Journal, 163 (6). Art. No. 244. ISSN 0004-6256. doi:10.3847/1538-3881/ac5c4c.

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The NASA K2 mission, salvaged from the hardware failures of the Kepler telescope, has continued Kepler’s planet-hunting success. It has revealed nearly 500 transiting planets around the ecliptic plane, many of which are the subject of further study, and over 1000 additional candidates. Here we present the results of an ongoing project to follow-up and statistically validate new K2 planets, in particular to identify promising new targets for further characterization. By analyzing the reconnaissance spectra, high-resolution imaging, centroid variations, and statistical likelihood of the signals of 91 candidates, we validate 60 new planets in 46 systems. These include a number of planets amenable to transmission spectroscopy (K2-384 f, K2-387 b, K2-390 b, K2-403 b, and K2-398 c), emission spectroscopy (K2-371 b, K2-370 b, and K2-399 b), and both (K2-405 b and K2-406 b); several systems with planets in or close to mean motion resonances (K2-381 and K2-398) including a compact, TRAPPIST-1-like system of five small planets orbiting a mid-M dwarf (K2-384); an ultra-short-period sub-Saturn in the hot Saturn desert (K2-399 b); and a super-Earth orbiting a moderately bright (V = 11.93), metal-poor ([Fe/H] = −0.579 ± 0.080) host star (K2-408 b). In total we validate planets around four F stars, 26 G stars, 13 K stars, and three M dwarfs. In addition, we provide a list of 37 vetted planet candidates that should be prioritized for future follow-up observation in order to be confirmed or validated.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper apertures target pixel files data products
Christiansen, Jessie L.0000-0002-8035-4778
Bhure, Sakhee0000-0002-6673-8206
Zink, Jon K.0000-0003-1848-2063
Hardegree-Ullman, Kevin K.0000-0003-3702-0382
Hedges, Christina0000-0002-3385-8391
Morton, Timothy D.0000-0002-8537-5711
Bieryla, Allyson0000-0001-6637-5401
Ciardi, David R.0000-0002-5741-3047
Cochran, William D.0000-0001-9662-3496
Dressing, Courtney D.0000-0001-8189-0233
Everett, Mark E.0000-0002-0885-7215
Isaacson, Howard0000-0002-0531-1073
Livingston, John H.0000-0002-4881-3620
Ziegler, Carl0000-0002-0619-7639
Calkins, Michael L.0000-0002-2830-5661
Esquerdo, Gilbert A.0000-0002-9789-5474
Latham, David W.0000-0001-9911-7388
Endl, Michael0000-0002-7714-6310
Fulton, Benjamin J.0000-0003-3504-5316
Hirsch, Lea A.0000-0001-8058-7443
Howard, Andrew W.0000-0001-8638-0320
Weiss, Lauren M.0000-0002-3725-3058
Dai, Fei0000-0002-8958-0683
Hirano, Teruyuki0000-0003-3618-7535
Tamura, Motohide0000-0002-6510-0681
Beichman, Charles0000-0002-5627-5471
Gonzales, Erica J.0000-0002-9329-2190
Schlieder, Joshua E.0000-0001-5347-7062
Barclay, Thomas0000-0001-7139-2724
Crossfield, Ian J. M.0000-0002-1835-1891
Gilbert, Emily A.0000-0002-0388-8004
Matthews, Elisabeth C.0000-0003-0593-1560
Giacalone, Steven0000-0002-8965-3969
Petigura, Erik A.0000-0003-0967-2893
Additional Information:© 2022. The Author(s). Published by the American Astronomical Society. 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 2021 December 21; revised 2022 February 1; accepted 2022 February 8; published 2022 May 9. The analyses described here were performed on the UCLA Hoffman2 shared computing cluster and using the resources provided by the Bhaumik Institute. This research has made use of the NASA Exoplanet Archive and the Exoplanet Follow-up Observation Program website, which are operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This publication makes use of data products collected by the Kepler mission and obtained from the MAST data archive at the Space Telescope Science Institute (STScI); the K2SFF apertures can be accessed via, and the K2 target pixel files via STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS526555. Support to MAST for these data is provided by the NASA Office of Space Science via grant NAG57584 and by other grants and contracts. Funding for the Kepler mission was provided by the NASA Science Mission Directorate. This publication makes use of data products from the Two Micron All Sky Survey, which is a joint project of the University of Massachusetts and the Infrared Processing and Analysis Center/California Institute of Technology, funded by the National Aeronautics and Space Administration and the National Science Foundation. This data set is made available by the Infrared Science Archive (IRSA) at IPAC, which is operated by the California Institute of Technology under contract with the National Aeronautics and Space Administration. The specific data products can be accessed via Funding for this work for C.H. is provided by grant No. 80NSSC20K0874, through NASA ROSES. M.T. is supported by JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. Support for this work was provided by NASA through the NASA Hubble Fellowship grant #51497.001 awarded by the Space Telescope Science Institute, which is operated by the Association of Universities for Research in Astronomy, Inc., for NASA, under contract NAS5-26555. The material is based upon work supported by NASA under award number 80GSFC21M0002 and by the GSFC Sellers Exoplanet Environments Collaboration (SEEC), which is funded by the NASA Planetary Science Divisions Internal Scientist Funding Mode. 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 Program 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. The authors are honored to be permitted to conduct observations on Iolkam Du'ag (Kitt Peak), a mountain within the Tohono O'odham Nation with particular significance to the Tohono O'odham people. 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 work made use of the crossmatch database created by Megan Bedell. Software: EVEREST (Luger et al. 2016, 2018), TERRA (Petigura et al. 2013), EDI-Vetter (Zink et al. 2020a), K2SFF (Vanderburg & Johnson 2014), PyMC3 (Salvatier et al. 2015), Exoplanet (Foreman-Mackey et al. 2019), RoboVetter (Thompson et al. 2018), batman Kreidberg (2015), emcee (Foreman-Mackey et al. 2013).
Group:Astronomy Department, Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Japan Society for the Promotion of Science (JSPS)18H05442
Japan Society for the Promotion of Science (JSPS)15H02063
Japan Society for the Promotion of Science (JSPS)22000005
NASA Hubble Fellowship51497.001
NASA Ames Research CenterUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Subject Keywords:Exoplanet catalogs; Exoplanet systems
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet catalogs (488); Exoplanet systems (484)
Record Number:CaltechAUTHORS:20220722-769478000
Persistent URL:
Official Citation:Jessie L. Christiansen et al 2022 AJ 163 244
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115795
Deposited By: George Porter
Deposited On:26 Jul 2022 17:47
Last Modified:26 Jul 2022 17:47

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