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

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 0.0...

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Bibliographic Details
Published in:The Astronomical journal 2020-09, Vol.160 (3), p.133
Main Authors: Mireles, Ismael, Shporer, Avi, Grieves, Nolan, Zhou, George, Günther, Maximilian N., Brahm, Rafael, Ziegler, Carl, Stassun, Keivan G., Huang, Chelsea X., Nielsen, Louise, dos Santos, Leonardo A., Udry, Stéphane, Bouchy, François, Ireland, Michael, Wallace, Alexander, Sarkis, Paula, Henning, Thomas, Jordán, Andrés, Law, Nicholas, Mann, Andrew W., Paredes, Leonardo A., James, Hodari-Sadiki, Jao, Wei-Chun, Henry, Todd J., Butler, R. Paul, Rodriguez, Joseph E., Yu, Liang, Flowers, Erin, Ricker, George R., Latham, David W., Vanderspek, Roland, Seager, Sara, Winn, Joshua N., Jenkins, Jon M., Furesz, Gabor, Hesse, Katharine, Quintana, Elisa V., Rose, Mark E., Smith, Jeffrey C., Tenenbaum, Peter, Vezie, Michael, Yahalomi, Daniel A., Zhan, Zhuchang
Format: Article
Language:English
Subjects:
Astronomy
ASTROPHYSICS, COSMOLOGY AND ASTRONOMY
Binary stars
COMPARATIVE EVALUATIONS
Convection
COSMOLOGICAL INFLATION
Eccentric orbits
Eclipsing binary stars
Extrasolar planets
Hydrogen
HYDROGEN BURNING
Low mass stars
M dwarf stars
MAGNETIC FIELDS
Object recognition
ORBITS
Planet detection
Transit
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Summary: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 (0.0849 0.0051 ) and radius of 1.111 0.017 (0.1142 0.0017 ). 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 (0.1023 0.0050 ) and radius of 1.248 0.018 (0.1282 0.0019 ). 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 2 above the canonical mass threshold of 0.075 . 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.
ISSN:0004-6256
1538-3881
1538-3881
DOI:10.3847/1538-3881/aba526