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TOI-1231 b: A Temperate, Neptune-sized Planet Transiting the Nearby M3 Dwarf NLTT 24399

Burt, Jennifer A. and Dragomir, Diana and Mollière, Paul and Youngblood, Allison and García Muñoz, Antonio and McCann, John and Kreidberg, Laura and Huang, Chelsea X. and Collins, Karen A. and Eastman, Jason D. and Abe, Lyu and Almenara, Jose M. and Crossfield, Ian J. M. and Ziegler, Carl and Rodriguez, Joseph E. and Mamajek, Eric E. and Stassun, Keivan G. and Halverson, Samuel P. and Villanueva, Steven and Butler, R. Paul and Wang, Sharon Xuesong and Schwarz, Richard P. and Ricker, George R. and Vanderspek, Roland and Latham, David W. and Seager, S. and Winn, Joshua N. and Jenkins, Jon M. and Agabi, Abdelkrim and Bonfils, Xavier and Ciardi, David and Cointepas, Marion and Crane, Jeffrey D. and Crouzet, Nicolas and Dransfield, Georgina and Feng, Fabo and Furlan, Elise and Guillot, Tristan and Gupta, Arvind F. and Howell, Steve B. and Jensen, Eric L. N. and Law, Nicholas and Mann, Andrew W. and Marie-Sainte, Wenceslas and Matson, Rachel A. and Matthews, Elisabeth C. and Mékarnia, Djamel and Pepper, Joshua and Scott, Nic and Shectman, Stephen A. and Schlieder, Joshua E. and Schmider, François-Xavier and Stevens, Daniel J. and Teske, Johanna K. and Triaud, Amaury H. M. J. and Charbonneau, David and Berta-Thompson, Zachory K. and Burke, Christopher J. and Daylan, Tansu and Barclay, Thomas and Wohler, Bill and Brasseur, C. E. (2021) TOI-1231 b: A Temperate, Neptune-sized Planet Transiting the Nearby M3 Dwarf NLTT 24399. Astronomical Journal, 162 (3). Art. No. 87. ISSN 0004-6256. doi:10.3847/1538-3881/ac0432.

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We report the discovery of a transiting, temperate, Neptune-sized exoplanet orbiting the nearby (d = 27.5 pc), M3V star TOI-1231 (NLTT 24399, L 248-27, 2MASS J10265947-5228099). The planet was detected using photometric data from the Transiting Exoplanet Survey Satellite and followed up with observations from the Las Cumbres Observatory and the Antarctica Search for Transiting ExoPlanets program. Combining the photometric data sets, we find that the newly discovered planet has a radius of 3.65_(-0.15)^(+0.16) R_⊕ and an orbital period of 24.246 days. Radial velocity measurements obtained with the Planet Finder Spectrograph on the Magellan Clay telescope confirm the existence of the planet and lead to a mass measurement of 15.5 ± 3.3 M_⊕. With an equilibrium temperature of just 330 K, TOI-1231 b is one of the coolest small planets accessible for atmospheric studies thus far, and its host star's bright near-infrared brightness (J = 8.88, K_s = 8.07) makes it an exciting target for the Hubble Space Telescope and the James Webb Space Telescope. Future atmospheric observations would enable the first comparative planetology efforts in the 250–350 K temperature regime via comparisons with K2-18 b. Furthermore, TOI-1231's high systemic radial velocity (70.5 km s⁻¹) may allow for the detection of low-velocity hydrogen atoms escaping the planet by Doppler, shifting the H i Lyα stellar emission away from the geocoronal and interstellar medium absorption features.

Item Type:Article
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URLURL TypeDescription Paper
Burt, Jennifer A.0000-0002-0040-6815
Dragomir, Diana0000-0003-2313-467X
Mollière, Paul0000-0003-4096-7067
Youngblood, Allison0000-0002-1176-3391
García Muñoz, Antonio0000-0003-1756-4825
McCann, John0000-0002-5155-6645
Kreidberg, Laura0000-0003-0514-1147
Huang, Chelsea X.0000-0003-0918-7484
Collins, Karen A.0000-0001-6588-9574
Eastman, Jason D.0000-0003-3773-5142
Crossfield, Ian J. M.0000-0002-1835-1891
Ziegler, Carl0000-0002-0619-7639
Rodriguez, Joseph E.0000-0001-8812-0565
Mamajek, Eric E.0000-0003-2008-1488
Stassun, Keivan G.0000-0002-3481-9052
Halverson, Samuel P.0000-0003-1312-9391
Villanueva, Steven0000-0001-6213-8804
Butler, R. Paul0000-0003-1305-3761
Wang, Sharon Xuesong0000-0002-6937-9034
Schwarz, Richard P.0000-0001-8227-1020
Ricker, George R.0000-0003-2058-6662
Vanderspek, Roland0000-0001-6763-6562
Latham, David W.0000-0001-9911-7388
Seager, S.0000-0002-6892-6948
Winn, Joshua N.0000-0002-4265-047X
Jenkins, Jon M.0000-0002-4715-9460
Bonfils, Xavier0000-0001-9003-8894
Ciardi, David0000-0002-5741-3047
Crane, Jeffrey D.0000-0002-5226-787X
Crouzet, Nicolas0000-0001-7866-8738
Dransfield, Georgina0000-0002-3937-630X
Feng, Fabo0000-0001-6039-0555
Furlan, Elise0000-0001-9800-6248
Guillot, Tristan0000-0002-7188-8428
Gupta, Arvind F.0000-0002-5463-9980
Howell, Steve B.0000-0002-2532-2853
Jensen, Eric L. N.0000-0002-4625-7333
Law, Nicholas0000-0001-9380-6457
Mann, Andrew W.0000-0003-3654-1602
Matson, Rachel A.0000-0001-7233-7508
Mékarnia, Djamel0000-0001-5000-7292
Pepper, Joshua0000-0002-3827-8417
Scott, Nic0000-0003-1038-9702
Shectman, Stephen A.0000-0002-8681-6136
Schlieder, Joshua E.0000-0001-5347-7062
Schmider, François-Xavier0000-0003-3914-3546
Stevens, Daniel J.0000-0002-5951-8328
Triaud, Amaury H. M. J.0000-0002-5510-8751
Charbonneau, David0000-0002-9003-484X
Berta-Thompson, Zachory K.0000-0002-3321-4924
Burke, Christopher J.0000-0002-7754-9486
Daylan, Tansu0000-0002-6939-9211
Barclay, Thomas0000-0001-7139-2724
Wohler, Bill0000-0002-5402-9613
Brasseur, C. E.0000-0002-9314-960X
Additional Information:© 2021. The American Astronomical Society. Received 2020 November 18; revised 2021 May 13; accepted 2021 May 20; published 2021 August 3. This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by NASA's Science Mission directorate. We acknowledge the use of public TESS alert data from pipelines at the TESS Science Office and the TESS Science Operations Center. This paper includes data gathered with the 6.5 meter Magellan Telescopes located at Las Campanas Observatory, Chile. This work makes use of observations from the LCOGT network and from the ASTEP telescope. ASTEP benefited from the support of the French and Italian polar agencies IPEV and PNRA in the framework of the Concordia Station program. 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. Some of the observations in the paper made use of the high-resolution-imaging instrument Zorro. 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). 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. Some of the data presented in this paper were obtained from the Mikulski Archive for Space Telescopes (MAST). Support for MAST for non-HST data is provided by the NASA Office of Space Science via grant NNX13AC07G and by other grants and contracts. 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 Program. This research has made use of NASA's Astrophysics Data System. This research has also made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This research made use of Astropy, a community-developed core Python package for Astronomy (Astropy Collaboration et al. 2013). Part of this research was carried out at the Jet Propulsion Laboratory, California Institute of Technology, under a contract with the National Aeronautics and Space Administration (NASA). D.D. acknowledges support from the TESS Guest Investigator Program grant 80NSSC19K1727 and NASA Exoplanet Research Program grant 18-2XRP18_2-0136. TD acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow. E.M. acknowledges support from NASA award 17-K2G06-0030. P.M. acknowledges support from the European Research Council under the European Union's Horizon 2020 research and innovation program under grant agreement No. 832428. T.G., A.A., L.A., D.M., F.-X.S. acknowledge support from Idex UCAJEDI (ANR-15-IDEX-01). D.J.S. acknowledges funding support from the Eberly Research Fellowship from The Pennsylvania State University Eberly College of Science. The Center for Exoplanets and Habitable Worlds is supported by the Pennsylvania State University, the Eberly College of Science, and the Pennsylvania Space Grant Consortium. This research received funding from the European Research Council (ERC) under the European Union's Horizon 2020 research and innovation program (grant agreement No. 803193/BEBOP), and from the Science and Technology Facilities Council (STFC; grant No. ST/S00193X/1). This publication makes use of VOSA, developed under the Spanish Virtual Observatory project supported by the Spanish MINECO through grant AyA2017-84089. VOSA has been partially updated by using funding from the European Union's Horizon 2020 Research and Innovation Programme, under grant agreement no 776403 (EXOPLANETS-A). Facilities: TESS - , Magellan: Clay (Planet Finder Spectrograph) - , Gemini-South (Zorro) - , SOAR - , LCOGT - , ASTEP. - Software: AstroImageJ (Collins et al. 2017), TAPIR (Jensen 2013), EXOFASTv2 (Eastman et al. 2019), petitCODE (Mollière et al. 2017), PyMultiNest (Buchner 2016), MultiNest (Feroz et al. 2009), Astropy (Astropy Collaboration et al. 2013).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
Institut polaire français Paul-Émile Victor (IPEV)UNSPECIFIED
Programma Nazionale di Ricerche in Antartide (PNRA)UNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Gemini PartnershipUNSPECIFIED
MIT Kavli Institute for Astrophysics and Space ResearchUNSPECIFIED
European Research Council (ERC)832428
Agence Nationale pour la Recherche (ANR)ANR-15-IDEX-01
Eberly College of ScienceUNSPECIFIED
Pennsylvania State UniversityUNSPECIFIED
Pennsylvania Space Grant ConsortiumUNSPECIFIED
European Research Council (ERC)803193
Science and Technology Facilities Council (STFC)ST/S00193X/1
Ministerio de Economía, Industria y Competitividad (MINECO)AyA2017-84089
European Research Council (ERC)776403
Subject Keywords:Exoplanet astronomy; Transit photometry; Radial velocity; Mini Neptunes
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet astronomy (486); Transit photometry (1709); Radial velocity (1332); Mini Neptunes (1063)
Record Number:CaltechAUTHORS:20210813-181159969
Persistent URL:
Official Citation:Jennifer A. Burt et al 2021 AJ 162 87
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:110247
Deposited By: George Porter
Deposited On:16 Aug 2021 15:49
Last Modified:16 Aug 2021 15:49

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