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HD 191939: Three Sub-Neptunes Transiting a Sun-like Star Only 54 pc Away

Badenas-Agusti, Mariona and Günther, Maximilian N. and Daylan, Tansu and Mikal-Evans, Thomas and Vanderburg, Andrew and Huang, Chelsea X. and Matthews, Elisabeth and Rackham, Benjamin V. and Bieryla, Allyson and Stassun, Keivan G. and Kane, Stephen R. and Shporer, Avi and Fulton, Benjamin J. and Hill, Michelle L. and Nowak, Grzegorz and Ribas, Ignasi and Pallé, Enric and Jenkins, Jon M. and Latham, David W. and Seager, Sara and Ricker, George R. and Vanderspek, Roland K. and Winn, Joshua N. and Abril-Pla, Oriol and Collins, Karen A. and Guerra Serra, Pere and Niraula, Prajwal and Rustamkulov, Zafar and Barclay, Thomas and Crossfield, Ian J. M. and Howell, Steve B. and Ciardi, David R. and Gonzales, Erica J. and Schlieder, Joshua E. and Caldwell, Douglas A. and Fausnaugh, Michael and McDermott, Scott and Paegert, Martin and Pepper, Joshua and Rose, Mark E. and Twicken, Joseph D. (2020) HD 191939: Three Sub-Neptunes Transiting a Sun-like Star Only 54 pc Away. Astronomical Journal, 160 (3). Art. No. 113. ISSN 1538-3881.

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We present the discovery of three sub-Neptune-sized planets transiting the nearby and bright Sun-like star HD 191939 (TIC 269701147, TOI 1339), a K_s = 7.18 mag G8 V dwarf at a distance of only 54 pc. We validate the planetary nature of the transit signals by combining 5 months of data from the Transiting Exoplanet Survey Satellite with follow-up ground-based photometry, archival optical images, radial velocities, and high angular resolution observations. The three sub-Neptunes have similar radii (R_b = 3.42^(+0.11)_(-0.11), R_c = 3.23^(+0.11)_(-0.11), R_d = 3.16^(+0.11)_(-0.11) R⊕), and their orbits are consistent with a stable, circular, and coplanar architecture near mean-motion resonances of 1:3 and 3:4 (P_b = 8.88, P_c = 28.58, and P_d = 38.35 days). The HD 191939 system is an excellent candidate for precise mass determinations of the planets with high-resolution spectroscopy due to the host star's brightness and low chromospheric activity. Moreover, the system's compact and near-resonant nature can provide an independent way to measure planetary masses via transit timing variations while also enabling dynamical and evolutionary studies. Finally, as a promising target for multiwavelength transmission spectroscopy of all three planets' atmospheres, HD 191939 can offer valuable insight into multiple sub-Neptunes born from a protoplanetary disk that may have resembled that of the early Sun.

Item Type:Article
Related URLs:
URLURL TypeDescription Paper
Günther, Maximilian N.0000-0002-3164-9086
Daylan, Tansu0000-0002-6939-9211
Mikal-Evans, Thomas0000-0001-5442-1300
Vanderburg, Andrew0000-0001-7246-5438
Huang, Chelsea X.0000-0003-0918-7484
Matthews, Elisabeth0000-0003-0593-1560
Rackham, Benjamin V.0000-0002-3627-1676
Bieryla, Allyson0000-0001-6637-5401
Stassun, Keivan G.0000-0002-3481-9052
Kane, Stephen R.0000-0002-7084-0529
Shporer, Avi0000-0002-1836-3120
Fulton, Benjamin J.0000-0003-3504-5316
Hill, Michelle L.0000-0002-0139-4756
Jenkins, Jon M.0000-0002-4715-9460
Latham, David W.0000-0001-9911-7388
Seager, Sara0000-0002-6892-6948
Ricker, George R.0000-0003-2058-6662
Vanderspek, Roland K.0000-0001-6763-6562
Winn, Joshua N.0000-0002-4265-047X
Collins, Karen A.0000-0001-6588-9574
Barclay, Thomas0000-0001-7139-2724
Crossfield, Ian J. M.0000-0002-1835-1891
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
Caldwell, Douglas A.0000-0003-1963-9616
Pepper, Joshua0000-0002-3827-8417
Rose, Mark E.0000-0003-4724-745X
Twicken, Joseph D.0000-0002-6778-7552
Additional Information:© 2020 The American Astronomical Society. Received 2020 February 10; revised 2020 June 19; accepted 2020 June 25; published 2020 August 14. Funding for this research is provided by the Massachusetts Institute of Technology, the MIT Torres Fellow Program, and the MIT Kavli Institute. We acknowledge the use of public TESS Alert data from pipelines at the TESS Science Office and the TESS Science Processing Operations Center. Funding for the TESS mission is provided by NASA's Science Mission directorate. This research has 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. 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. This paper includes data collected by the TESS mission that are publicly available from the Mikulski Archive for Space Telescopes (MAST). The STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. 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. 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. The National Geographic Society—Palomar Observatory Sky Atlas (POSS-I) was made by the California Institute of Technology with grants from the National Geographic Society. The Second Palomar Observatory Sky Survey (POSS-II) was made by the California Institute of Technology with funds from the National Science Foundation, the National Geographic Society, the Sloan Foundation, the Samuel Oschin Foundation, and the Eastman Kodak Corporation. 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 paper used data retrieved from the SOPHIE archive at Observatoire de Haute-Provence (OHP), available at The AO images presented in this paper were obtained at the Gemini Observatory (Program ID: GN-2019B-LP-101), which is operated by the Association of Universities for Research in Astronomy, Inc., under a cooperative agreement with the NSF on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), CONICYT (Chile), Ministerio de Ciencia, Tecnología e Innovación Productiva (Argentina), Ministério da Ciência, Tecnologia e Inovação (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). The authors thank Amanda Bosh (MIT), Tim Brothers (MIT Wallace Astrophysical Observatory), Julien de Wit (MIT), Artem Burdanov (MIT), Songhu Wang (Yale University), Enrique Herrero (IEEC/OAdM), Jonathan Irwin (Harvard-CfA), Samuel Hadden (Harvard-CfA), Özgür Baştürk (Ankara University), Ergün Ege (Istanbul University), and Brice-Olivier Demory (University of Bern) for helping to coordinate follow-up observations. We thank the anonymous referee for helpful comments and suggestions that greatly improved this work. M.N.G. and C.X.H. acknowledge support from MIT's Kavli Institute as Juan Carlos Torres Fellows. T.D. acknowledges support from MIT's Kavli Institute as a Kavli postdoctoral fellow. A.V.'s work was performed under contract with the California Institute of Technology/Jet Propulsion Laboratory, funded by NASA through the Sagan Fellowship Program executed by the NASA Exoplanet Science Institute. I.R. acknowledges support from the Spanish Ministry of Science, Innovation and Universities (MCIU) and the Fondo Europeo de Desarrollo Regional (FEDER) through grant PGC2018-098153-B-C33, as well as the support of the Generalitat de Catalunya/CERCA program. B.V.R. and J.N.W. thank the Heising-Simons Foundation for support. I.J.M.C. acknowledges support from the NSF through grant AST-1824644 and NASA through Caltech/JPL grant RSA-1610091. Facilities: TESS - , FLWO: 1.5 m (TRES) - , LCO: 1 m (NRES) - , OHP: 1.93 m (SOPHIE) - , Gemini/NIRI - , OAA: 0.4 m. - Software: Python (van Rossum 1995), numpy (Oliphant 2006), scipy (Virtanen et al. 2020), matplotlib (Hunter 2007), astropy (Price-Whelan et al. 2018), pandas (McKinney 2010), allesfitter (Günther & Daylan 2020, and in preparation) emcee (Foreman-Mackey et al. 2013), corner (Foreman-Mackey 2016), tqdm (da Costa-Luis et al. 2020), lightkurve (Lightkurve Collaboration et al. 2018), Transit Least Squares (Hippke & Heller 2019), vespa (Morton 2012), isochrones (Morton 2015), isoclassify (Huber et al. 2017), forecaster (Chen & Kipping 2017), exoplanet (Foreman-Mackey et al. 2019), starry (Luger et al. 2019), pymc3 (Salvatier et al. 2016), theano (Theano Development Team et al. 2016), rebound (Rein & Liu 2012).
Group:Infrared Processing and Analysis Center (IPAC)
Funding AgencyGrant Number
MIT Kavli Institute for Astrophysics and Space ResearchUNSPECIFIED
NASANAS 5-26555
National Geographic SocietyUNSPECIFIED
Alfred P. Sloan FoundationUNSPECIFIED
Samuel Oschin FoundationUNSPECIFIED
Eastman Kodak CompanyUNSPECIFIED
Gaia Multilateral AgreementUNSPECIFIED
Ministerio de Ciencia, Innovación y Universidades (MICIU)UNSPECIFIED
Fondo Europeo de Desarrollo Regional (FEDER)PGC2018-098153-B-C33
Generalitat de CatalunyaUNSPECIFIED
Heising-Simons FoundationUNSPECIFIED
Subject Keywords:Exoplanet systems ; Exoplanets ; Transit photometry ; Exoplanet detection methods ; Astronomical techniques
Issue or Number:3
Classification Code:Unified Astronomy Thesaurus concepts: Exoplanet systems (484); Exoplanets (498); Transit photometry (1709); Exoplanet detection methods (489); Astronomical techniques (1684)
Record Number:CaltechAUTHORS:20200611-113704025
Persistent URL:
Official Citation:Mariona Badenas-Agusti et al 2020 AJ 160 113
Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:103846
Deposited By: George Porter
Deposited On:12 Jun 2020 14:27
Last Modified:14 Aug 2020 17:54

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