TOI-503: The First Known Brown-dwarf Am-star Binary from the TESS Mission

Ján Šubjak, Ján Šubjak, Rishikesh Sharma, Theron W. Carmichael, Theron W. Carmichael, Marshall C. Johnson, Erica J. Gonzales, Elisabeth Matthews, Henri M.J. Boffin, Rafael Brahm, Rafael Brahm, Rafael Brahm, Priyanka Chaturvedi, Abhijit Chakraborty, David R. Ciardi, Karen A. Collins, Massimiliano Esposito, Malcolm Fridlund, Malcolm Fridlund, Tianjun GanDavide Gandolfi, Rafael A. Garciá, Rafael A. Garciá, Eike Guenther, Artie Hatzes, David W. Latham, Stéphane Mathis, Stéphane Mathis, Savita Mathur, Savita Mathur, Carina M. Persson, Howard M. Relles, Joshua E. Schlieder, Thomas Barclay, Courtney D. Dressing, Ian Crossfield, Andrew W. Howard, Florian Rodler, George Zhou, Samuel N. Quinn, Gilbert A. Esquerdo, Michael L. Calkins, Perry Berlind, Keivan G. Stassun, Keivan G. Stassun, Martin Blažek, Martin Blažek, Marek Skarka, Marek Skarka, Magdalena Špoková, Magdalena Špoková, Jirí Žák, Simon Albrecht, Roi Alonso Sobrino, Roi Alonso Sobrino, Paul Beck, Paul Beck, Paul Beck, Juan Cabrera, Ilaria Carleo, William D. Cochran, Szilard Csizmadia, Fei Dai, Fei Dai, Hans J. Deeg, Hans J. Deeg, Jerome P. De Leon, Philipp Eigmüller, Michael Endl, Anders Erikson, Akihiko Fukui, Akihiko Fukui, Akihiko Fukui, Iskra Georgieva, Luciá González-Cuesta, Luciá González-Cuesta, Sascha Grziwa, Diego Hidalgo, Diego Hidalgo, Teruyuki Hirano, Maria Hjorth, Emil Knudstrup, Judith Korth, Kristine W.F. Lam, John H. Livingston, Mikkel N. Lund, Rafael Luque, Rafael Luque, Pilar Montanes Rodríguez, Pilar Montanes Rodríguez, Felipe Murgas, Felipe Murgas, Norio Narita, David Nespral, David Nespral, Prajwal Niraula, Grzegorz Nowak, Grzegorz Nowak, Enric Pallé, Enric Pallé, Martin Pätzold, Jorge Prieto-Arranz, Jorge Prieto-Arranz, Heike Rauer, Heike Rauer, Heike Rauer, Seth Redfield, Ignasi Ribas, Ignasi Ribas, Alexis M.S. Smith, Vincent Van Eylen, Petr Kabáth

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28 Scopus citations


We report the discovery of an intermediate-mass transiting brown dwarf (BD), TOI-503b, from the TESS mission. TOI-503b is the first BD discovered by TESS, and it has circular orbit around a metallic-line A-type star with a period of P = 3.6772 ± 0.0001 days. The light curve from TESS indicates that TOI-503b transits its host star in a grazing manner, which limits the precision with which we measure the BD's radius . We obtained high-resolution spectroscopic observations with the FIES, Ondrejov, PARAS, Tautenburg, and TRES spectrographs, and measured the mass of TOI-503b to be M b = 53.7 ± 1.2 a radius of R = 1.70 ± 0.05R o, an effective temperature of T eff = 7650 ± 160 K, and a relatively high metallicity of 0.61 ± 0.07 dex. We used stellar isochrones to derive the age of the system to be ∼180 Myr, which places its age between that of RIK 72b (a ∼10 Myr old BD in the Upper Scorpius stellar association) and AD 3116b (a ∼600 Myr old BD in the Praesepe cluster). Given the difficulty in measuring the tidal interactions between BDs and their host stars, we cannot precisely say whether this BD formed in situ or has had its orbit circularized by its host star over the relatively short age of the system. Instead, we offer an examination of plausible values for the tidal quality factor for the star and BD. TOI-503b joins a growing number of known short-period, intermediate-mass BDs orbiting main-sequence stars, and is the second such BD known to transit an A star, after HATS-70b. With the growth in the population in this regime, the driest region in the BD desert is reforesting.

Original languageEnglish
Article number151
JournalAstronomical Journal
Issue number4
StatePublished - Apr 2020
Externally publishedYes


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