TOI 694b and TIC 220568520b: Two Low-mass Companions near the Hydrogen-burning Mass Limit Orbiting Sun-like Stars

Mireles, Ismael and Shporer, Avi and Grieves, Nolan and Zhou, George ORCID: and Gunther, Maximilian N. and Brahm, Rafael and Ziegler, Carl and Stassun, Keivan G. and Huang, Chelsea X. ORCID: and Nielsen, Louise and Dos Santos, Leonardo A. and Udry, Stephane and Bouchy, Francois and Ireland, Michael and Wallace, Alexander and Sarkis, Paula and Henning, Thomas and Jordan, Andres and Law, Nicholas and Mann, Andrew W. and Paredes, Leonardo A. and James, Hodari-Sadiki and Jao, Wei-Chun and Henry, Todd J. and Butler, R. Paul and Rodriguez, Joseph E. and Yu, Liang and Flowers, Erin and Ricker, George R. and Latham, David W. and Vanderspek, Roland and Seager, Sara and Winn, Joshua N. and Jenkins, Jon M. and Furesz, Gabor and Hesse, Katharine and Quintana, Elisa V. and Rose, Mark E. and Smith, Jeffrey C. and Tenenbaum, Peter and Vezie, Michael and Yahalomi, Daniel A. and Zhan, Zhuchang (2020) TOI 694b and TIC 220568520b: Two Low-mass Companions near the Hydrogen-burning Mass Limit Orbiting Sun-like Stars. The Astronomical Journal, 160 (3):133. pp. 1-13. ISSN 0004-6256

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We report the discovery of TOI 694 b and TIC 220568520 b, two low-mass stellar companions in eccentric orbits around metal-rich Sun-like stars, first detected by the Transiting Exoplanet Survey Satellite (TESS). TOI 694 b has an orbital period of 48.05131 ± 0.00019 days and eccentricity of 0.51946 ± 0.00081, and we derive a mass of 89.0 ± 5.3 MJup (0.0849 ± 0.0051 M⊙) and radius of 1.111 ± 0.017 RJup (0.1142 ± 0.0017 R⊙). TIC 220568520 b has an orbital period of 18.55769 ± 0.00039 days and eccentricity of 0.0964 ± 0.0032, and we derive a mass of 107.2 ± 5.2 MJup (0.1023 ± 0.0050 M⊙) and radius of 1.248 ± 0.018 RJup (0.1282 ± 0.0019 R⊙). Both binary companions lie close to and above the hydrogen-burning mass threshold that separates brown dwarfs and the lowest-mass stars, with TOI 694 b being 2σ above the canonical mass threshold of 0.075 M⊙. The relatively long periods of the systems mean that the magnetic fields of the low-mass companions are not expected to inhibit convection and inflate the radius, which according to one leading theory is common in similar objects residing in short-period tidally synchronized binary systems. Indeed we do not find radius inflation for these two objects when compared to theoretical isochrones. These two new objects add to the short but growing list of low-mass stars with well-measured masses and radii, and highlight the potential of the TESS mission for detecting such rare objects orbiting bright stars.

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Item Type: Article (Commonwealth Reporting Category C)
Refereed: Yes
Item Status: Live Archive
Faculty/School / Institute/Centre: No Faculty
Faculty/School / Institute/Centre: No Faculty
Date Deposited: 10 Feb 2022 03:56
Last Modified: 04 Apr 2022 07:34
Uncontrolled Keywords: Low mass stars; M dwarf stars; Eclipsing binary stars; Astrophysics - Solar and Stellar Astrophysics; Astrophysics - Earth and Planetary Astrophysics
Fields of Research (2008): 02 Physical Sciences > 0201 Astronomical and Space Sciences > 020110 Stellar Astronomy and Planetary Systems
Fields of Research (2020): 51 PHYSICAL SCIENCES > 5101 Astronomical sciences > 510109 Stellar astronomy and planetary systems
Socio-Economic Objectives (2008): E Expanding Knowledge > 97 Expanding Knowledge > 970102 Expanding Knowledge in the Physical Sciences
Socio-Economic Objectives (2020): 28 EXPANDING KNOWLEDGE > 2801 Expanding knowledge > 280120 Expanding knowledge in the physical sciences
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