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A Close-in Puffy Neptune with Hidden Friends: The Enigma of TOI 620

Reefe, Michael A. and Luque, Rafael and Gaidos, Eric and Beard, Corey and Plavchan, Peter P. and Cointepas, Marion and Cale, Bryson L. and Palle, Enric and Parviainen, Hannu and Feliz, Dax L. and Eastman, Jason and Stassun, Keivan and Gagné, Jonathan and Jenkins, Jon M. and Boyd, Patricia T. and Kidwell, Richard C. and McDermott, Scott and Collins, Karen A. and Fong, William and Guerrero, Natalia and Almenara-Villa, Jose-Manuel and Bean, Jacob and Beichman, Charles A. and Berberian, John and Bieryla, Allyson and Bonfils, Xavier and Bouchy, François and Brady, Madison and Bryant, Edward M. and Cacciapuoti, Luca and Cañas, Caleb I. and Ciardi, David R. and Collins, Kevin I. and Crossfield, Ian J. M. and Dressing, Courtney D. and Eigmüller, Philipp and El Mufti, Mohammed and Esparza-Borges, Emma and Fukui, Akihiko and Gao, Peter and Geneser, Claire and Gnilka, Crystal L. and Gonzales, Erica and Gupta, Arvind F. and Halverson, Sam and Hearty, Fred and Howell, Steve B. and Irwin, Jonathan and Kanodia, Shubham and Kasper, David and Kodama, Takanori and Kostov, Veselin and Latham, David W. and Lendl, Monika and Lin, Andrea and Livingston, John H. and Lubin, Jack and Mahadevan, Suvrath and Matson, Rachel and Matthews, Elisabeth and Murgas, Felipe and Narita, Norio and Newman, Patrick and Ninan, Joe and Osborn, Ares and Quinn, Samuel N. and Robertson, Paul and Roy, Arpita and Schlieder, Joshua and Schwab, Christian and Seifahrt, Andreas and Smith, Gareth D. and Sohani, Ahmad and Stefánsson, Guðmundur and Stevens, Daniel and Stürmer, Julian and Tanner, Angelle and Terrien, Ryan and Teske, Johanna and Vermilion, David and Wang, Sharon X. and Wittrock, Justin and Wright, Jason T. and Zechmeister, Mathias and Zohrabi, Farzaneh (2022) A Close-in Puffy Neptune with Hidden Friends: The Enigma of TOI 620. Astronomical Journal, 163 (6). Art. No. 269. ISSN 0004-6256. doi:10.3847/1538-3881/ac658b.

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We present the validation of a transiting low-density exoplanet orbiting the M2.5 dwarf TOI 620 discovered by the NASA Transiting Exoplanet Survey Satellite (TESS) mission. We utilize photometric data from both TESS and ground-based follow-up observations to validate the ephemerides of the 5.09 day transiting signal and vet false-positive scenarios. High-contrast imaging data are used to resolve the stellar host and exclude stellar companions at separations ≳0.″2. We obtain follow-up spectroscopy and corresponding precise radial velocities (RVs) with multiple precision radial velocity (PRV) spectrographs to confirm the planetary nature of the transiting exoplanet. We calculate a 5σ upper limit of Mₚ < 7.1M_⊕ and ρₚ < 0.74 g cm⁻³, and we identify a nontransiting 17.7 day candidate. We also find evidence for a substellar (1–20 Mⱼ) companion with a projected separation ≲20 au from a combined analysis of Gaia, adaptive optics imaging, and RVs. With the discovery of this outer companion, we carry out a detailed exploration of the possibilities that TOI 620 b might instead be a circum-secondary planet or a pair of eclipsing binary stars orbiting the host in a hierarchical triple system. We find, under scrutiny, that we can exclude both of these scenarios from the multiwavelength transit photometry, thus validating TOI 620 b as a low-density exoplanet transiting the central star in this system. The low density of TOI 620 b makes it one of the most amenable exoplanets for atmospheric characterization, such as with the James Webb Space Telescope and Ariel, validated or confirmed by the TESS mission to date.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Reefe, Michael A.0000-0003-4701-8497
Luque, Rafael0000-0002-4671-2957
Gaidos, Eric0000-0002-5258-6846
Beard, Corey0000-0001-7708-2364
Plavchan, Peter P.0000-0002-8864-1667
Cale, Bryson L.0000-0001-6279-0595
Palle, Enric0000-0003-0987-1593
Parviainen, Hannu0000-0001-5519-1391
Feliz, Dax L.0000-0002-2457-7889
Eastman, Jason0000-0003-3773-5142
Stassun, Keivan0000-0002-3481-9052
Gagné, Jonathan0000-0002-2592-9612
Jenkins, Jon M.0000-0002-4715-9460
Boyd, Patricia T.0000-0003-0442-4284
Collins, Karen A.0000-0001-6588-9574
Fong, William0000-0003-0241-2757
Guerrero, Natalia0000-0002-5169-9427
Almenara-Villa, Jose-Manuel0000-0003-3208-9815
Bean, Jacob0000-0003-4733-6532
Beichman, Charles A.0000-0002-5627-5471
Berberian, John0000-0003-1466-8389
Bieryla, Allyson0000-0001-6637-5401
Bonfils, Xavier0000-0001-9003-8894
Bouchy, François0000-0002-7613-393X
Brady, Madison0000-0003-2404-2427
Bryant, Edward M.0000-0001-7904-4441
Cacciapuoti, Luca0000-0001-8266-0894
Cañas, Caleb I.0000-0003-4835-0619
Ciardi, David R.0000-0002-5741-3047
Collins, Kevin I.0000-0003-2781-3207
Crossfield, Ian J. M.0000-0002-1835-1891
Dressing, Courtney D.0000-0001-8189-0233
Eigmüller, Philipp0000-0003-4096-0594
El Mufti, Mohammed0000-0001-8364-2903
Esparza-Borges, Emma0000-0002-2341-3233
Fukui, Akihiko0000-0002-4909-5763
Gao, Peter0000-0002-8518-9601
Geneser, Claire0000-0001-9596-8820
Gnilka, Crystal L.0000-0003-2519-6161
Gonzales, Erica0000-0002-9329-2190
Gupta, Arvind F.0000-0002-5463-9980
Halverson, Sam0000-0003-1312-9391
Hearty, Fred0000-0002-1664-3102
Howell, Steve B.0000-0002-2532-2853
Kanodia, Shubham0000-0001-8401-4300
Kasper, David0000-0003-0534-6388
Kodama, Takanori0000-0001-9032-5826
Kostov, Veselin0000-0001-9786-1031
Latham, David W.0000-0001-9911-7388
Lendl, Monika0000-0001-9699-1459
Lin, Andrea0000-0002-9082-6337
Livingston, John H.0000-0002-4881-3620
Lubin, Jack0000-0001-8342-7736
Mahadevan, Suvrath0000-0001-9596-7983
Matson, Rachel0000-0001-7233-7508
Matthews, Elisabeth0000-0003-0593-1560
Murgas, Felipe0000-0001-9087-1245
Narita, Norio0000-0001-8511-2981
Newman, Patrick0000-0003-3848-3418
Ninan, Joe0000-0001-8720-5612
Osborn, Ares0000-0002-5899-7750
Quinn, Samuel N.0000-0002-8964-8377
Robertson, Paul0000-0003-0149-9678
Roy, Arpita0000-0001-8127-5775
Schlieder, Joshua0000-0001-5347-7062
Schwab, Christian0000-0002-0091-7105
Seifahrt, Andreas0000-0003-4526-3747
Sohani, Ahmad0000-0002-6141-1669
Stefánsson, Guðmundur0000-0001-7409-5688
Stevens, Daniel0000-0002-5951-8328
Stürmer, Julian0000-0002-4410-4712
Tanner, Angelle0000-0002-2903-2140
Terrien, Ryan0000-0002-4788-8858
Vermilion, David0000-0002-4501-564X
Wang, Sharon X.0000-0002-6937-9034
Wittrock, Justin0000-0002-7424-9891
Wright, Jason T.0000-0001-6160-5888
Zechmeister, Mathias0000-0002-6532-4378
Zohrabi, Farzaneh0000-0003-2872-9883
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 October 23; revised 2022 March 11; accepted 2022 April 6; published 2022 May 16. M.A.R. and P.P.P. acknowledge support from NASA (Exoplanet Research Program Award #80NSSC20K0251, TESS Cycle 3 Guest Investigator Program Award #80NSSC21K0349, JPL Research and Technology Development, and Keck Observatory Data Analysis) and the NSF (Astronomy and Astrophysics grant Nos. 1716202 and 2006517), and the Mt Cuba Astronomical Foundation. R.L. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación, through project PID2019-109522GB-C52, and the Centre of Excellence "Severo Ochoa" award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). This work is partly supported by JSPS KAKENHI grant No. P17H04574, JP18H05439, JP20K14518, JP21K13975, JST CREST grant No. JPMJCR1761, and the Astrobiology Center of National Institutes of Natural Sciences (NINS) (grant Nos. AB022006, AB031010, AB031014). This work is partly financed by the Spanish Ministry of Economics and Competitiveness through grant No. PGC2018-098153-B-C31. The development of the MAROON-X spectrograph was funded by the David and Lucile Packard Foundation, the Heising-Simons Foundation, the Gemini Observatory, and the University of Chicago. We thank the staff of the Gemini Observatory for their assistance with the commissioning and operation of the instrument. The MAROON-X observing program is supported by NSF grant No. 2108465. This work was enabled by observations made from the Gemini North telescope, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the universe from a place that is unique in both its astronomical quality and its cultural significance. Some of the observations in the paper made use of the High-Resolution Imaging instrument Zorro obtained under Gemini LLP Proposal Number GN/S-2021A-LP-105. Zorro was 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. Zorro was mounted on the Gemini South telescope of the international Gemini Observatory, a program of NSF's OIR Lab, 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). V.K. gratefully acknowledges support from NASA via grant No. NNX17AF81G. Based on data collected under the NGTS project at the ESO La Silla Paranal Observatory. The NGTS facility is operated by the consortium institutes with support from the UK Science and Technology Facilities Council (STFC) projects ST/M001962/1 and ST/S002642/1. 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. M.L. acknowledges support from the Swiss National Science Foundation under grant No. PCEFP2_194576. The contribution of M.L. has been carried out within the framework of the NCCR PlanetS supported by the Swiss National Science Foundation. C.I.C. acknowledges support by NASA Headquarters under the NASA Earth and Space Science Fellowship Program through grant No. 80NSSC18K1114. NEID is funded by NASA/JPL under contract 1547612. Observations in this 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. This paper is based on observations obtained from the Las Campanas Remote Observatory, which is a partnership between Carnegie Observatories, The Astro-Physics Corporation, Howard Hedlund, Michael Long, Dave Jurasevich, and SSC Observatories. We acknowledge support from NSF grant Nos. AST-190950 and 1910954. This article is based on observations made with the MuSCAT2 instrument, developed by ABC, at Telescopio Carlos Sánchez, operated on the island of Tenerife by the IAC in the Spanish Observatorio del Teide. This material is based upon work supported by the National Science Foundation Graduate Research Fellowship under grant No. DGE 1746045. We acknowledge the use of public TESS data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. Based on data collected under the ExTrA project at the ESO La Silla Paranal Observatory. ExTrA is a project of Institut de Planétologie et d'Astrophysique de Grenoble (IPAG/CNRS/UGA), funded by the European Research Council under the ERC Grant Agreement No. 337591-ExTrA. This work has been supported by a grant from Labex OSUG@2020 (Investissements d'avenir—ANR10 LABX56). Facilities: NASA IRTF - , Calar Alto Observatory - , Gemini North - , Gemini South - , Fred L. Whipple Observatory - , TESS - , ESO La Silla Paranal Observatory - , Las Cumbres Observatory - , Teide Observatory - , Lick Observatory - , WIYN Observatory - . Software: Python: pychell (Cale et al. 2019), EDI-Vetter Unplugged (Zink et al. 2020), DAVE (Kostov et al. 2019), tpfplotter (Aller et al. 2020), emcee (Foreman-Mackey et al. 2013), NumPy (Harris et al. 2020), SciPy (Virtanen et al. 2020), Matplotlib (Hunter 2007), AstroPy (Robitaille et al. 2013), corner (Foreman-Mackey et al. 2020), barycorrpy (Kanodia & Wright 2018), Numba (Lam et al. 2015), PyTransit (Parviainen 2015), serval (Zechmeister et al. 2018), IDL: EXOFASTv2 (Eastman et al.2013).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
JPL Research and Technology Development FundUNSPECIFIED
Mt. Cuba Astronomical FoundationUNSPECIFIED
Ministerio de Ciencia, Innovación y Universidades (MCIU)PID2019-109522GB-C52
Severo OchoaSEV-2017-0709
Japan Society for the Promotion of Science (JSPS)P17H04574
Japan Society for the Promotion of Science (JSPS)JP18H05439
Japan Society for the Promotion of Science (JSPS)JP20K14518
Japan Society for the Promotion of Science (JSPS)JP21K13975
Japan Science and Technology AgencyJPMJCR1761
National Institutes of Natural Sciences of JapanAB022006
National Institutes of Natural Sciences of JapanAB031010
National Institutes of Natural Sciences of JapanAB031014
Ministerio de Economía, Industria y Competitividad (MINECO)PGC2018-098153-B-C31
Gemini PartnershipUNSPECIFIED
Science and Technology Facilities Council (STFC)ST/M001962/1
Science and Technology Facilities Council (STFC)ST/S002642/1
Gaia Multilateral AgreementUNSPECIFIED
Swiss National Science Foundation (SNSF)PCEFP2_194576
NASA Earth and Space Science Fellowship80NSSC18K1114
NSF Graduate Research FellowshipDGE-1746045
Agence Nationale pour la Recherche (ANR)ANR10 LABX56
Subject Keywords:Near infrared astronomy; Optical astronomy; Radial velocity; Transit photometry; Astronomy data analysis
Issue or Number:6
Classification Code:Unified Astronomy Thesaurus concepts: Near infrared astronomy (1093); Optical astronomy (1776); Radial velocity (1332); Transit photometry (1709); Astronomy data analysis (1858)
Record Number:CaltechAUTHORS:20220608-849600000
Persistent URL:
Official Citation:Michael A. Reefe et al 2022 AJ 163 269
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:115091
Deposited By: George Porter
Deposited On:08 Jun 2022 22:25
Last Modified:08 Jun 2022 22:25

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