TOI-503: The first known brown dwarf-Am star binary from the TESS mission
Creators: name: Šubjak, Ján
name: Sharma, Rishikesh
name: Carmichael, Theron W.
name: Johnson, Marshall C.
name: Gonzales, Erica J.
name: Matthews, Elisabeth
name: Boffin, Henri M. J.
name: Brahm, Rafael
name: Chaturvedi, Priyanka
name: Chakraborty, Abhijit
name: Ciardi, David R.
name: Collins, Karen A.
name: Esposito, Massimiliano
name: Fridlund, Malcolm
name: Gan, Tianjun
name: Gandolfi, Davide
name: García, Rafael A.
name: Guenther, Eike
name: Hatzes, Artie
name: Latham, David W.
name: Persson, Carina M.
name: Relles, Howard M.
name: Schlieder, Joshua E.
name: Barclay, Thomas
name: Dressing, Courtney
name: Crossfield, Ian
name: Howard, Andrew W.
name: Rodler, Florian
name: Zhou, George
name: Quinn, Samuel N.
name: Esquerdo, Gilbert A.
name: Calkins, Michael L.
name: Berlind, Perry
name: Stassun, Keivan G.
name: Albrecht, Simon
name: Sobrino, Roi Alonso
name: Beck, Paul
name: Blažek, Martin
name: Cabrera, Juan
name: Carleo, Ilaria
name: Cochran, William D.
name: Csizmadia, Szilard
name: Dai, Fei
name: Deeg, Hans J.
name: de Leon, Jerome P.
name: Eigmüller, Philipp
name: Endl, Michael
name: Erikson, Anders
name: Fukui, Akai
name: Georgieva, Iskra
name: González-Cuesta, Lucía
name: Grziwa, Sascha
name: Hidalgo, Diego
name: Hirano, Teruyuki
name: Hjorth, Maria
name: Knudstrup, Emil
name: Korth, Judith
name: Lam, Kristine W. F.
name: Livingston, John H.
name: Lund, Mikkel N.
name: Luque, Rafael
name: Mathur, Savita
name: Rodríguez, Pilar Montanes
name: Murgas, Felipe
name: Narita, Norio
name: Nespral, David
name: Niraula, Prajwal
name: Nowak, Grzegorz
name: Pallé, Enric
name: Pätzold, Martin
name: Prieto-Arranz, Jorge
name: Rauer, Heike
name: Redfield, Seth
name: Ribas, Ignasi
name: Skarka, Marek
name: Smith, Alexis M. S.
name: Špoková, Magdalena
name: Van Eylen, Vincent
name: Kabáth, Petr
Publisher: name: arXiv
Year: 2019
Subjects: subject: Solar and Stellar Astrophysics (astro-ph.SR)
subject: Earth and Planetary Astrophysics (astro-ph.EP)
subject: FOS: Physical sciences
subject: FOS: Physical sciences

description: We report the discovery of an intermediate-mass transiting brown dwarf, TOI-503b, from the TESS mission. TOI-503b is the first brown dwarf discovered by TESS and orbits a metallic-line A-type star with a period of $P=3.6772 \pm 0.0001$ 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 brown dwarf's radius ($R_b = 1.34^{+0.26}_{-0.15} R_J$). We obtained high-resolution spectroscopic observations with the FIES, Ondřejov, PARAS, Tautenburg, and TRES spectrographs and measured the mass of TOI-503b to be $M_b = 53.7 \pm 1.2 M_J$. The host star has a mass of $M_\star = 1.80 \pm 0.06 M_\odot$, a radius of $R_\star = 1.70 \pm 0.05 R_\odot$, an effective temperature of $T_{\rm eff} = 7650 \pm 160$K, and a relatively high metallicity of $0.61\pm 0.07$ dex. We used stellar isochrones to derive the age of the system to be $\sim$180 Myr, which places its age between that of RIK 72b (a $\sim$10 Myr old brown dwarf in the Upper Scorpius stellar association) and AD 3116b (a $\sim$600 Myr old brown dwarf in the Praesepe cluster). We argue that this brown dwarf formed in-situ, based on the young age of the system and the long circularization timescale for this brown dwarf around its host star. TOI-503b joins a growing number of known short-period, intermediate-mass brown dwarfs orbiting main sequence stars, and is the second such brown dwarf known to transit an A star, after HATS-70b. With the growth in the population in this regime, the driest region in the brown dwarf desert ($35-55 M_J \sin{i}$) is reforesting and its mass range shrinking.
description: 26 pages, 14 figures, 6 tables. Accepted to AJ