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TOI-2257 b : a highly eccentric long-period sub-Neptune transiting a nearby M dwarf
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(2022) TOI-2257 b : a highly eccentric long-period sub-Neptune transiting a nearby M dwarf. Astronomy & Astrophysics, 657 . A45. doi:10.1051/0004-6361/202142280 ISSN 0004-6361.
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Official URL: http://dx.doi.org/10.1051/0004-6361/202142280
Abstract
Context. Thanks to the relative ease of finding and characterizing small planets around M-dwarf stars, these objects have become cornerstones in the field of exoplanet studies. The current paucity of planets in long-period orbits around M dwarfs makes such objects particularly compelling as they provide clues about the formation and evolution of these systems.
Aims. In this study we present the discovery of TOI-2257 b (TIC 198485881), a long-period (35 d) sub-Neptune orbiting an M3 star at 57.8 pc. Its transit depth is about 0.4%, large enough to be detected with medium-size, ground-based telescopes. The long transit duration suggests the planet is in a highly eccentric orbit (e ~ 0.5), which would make it the most eccentric planet known to be transiting an M-dwarf star.
Methods. We combined TESS and ground-based data obtained with the 1.0-meter SAINT-EX, 0.60-meter TRAPPIST-North, and 1.2-meter FLWO telescopes to find a planetary size of 2.2 R⊕ and an orbital period of 35.19 days. In addition, we make use of archival data, high-resolution imaging, and vetting packages to support our planetary interpretation.
Results. With its long period and high eccentricity, TOI-2257 b falls into a novel slice of parameter space. Despite the planet’s low equilibrium temperature (~256 K), its host star’s small size (R* = 0.311 ± 0.015) and relative infrared brightness (Kmag = 10.7) make it a suitable candidate for atmospheric exploration via transmission spectroscopy.
Item Type: | Journal Article | ||||||||||||||||||||||||||||||||||||||||||||||||
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Subjects: | Q Science > QB Astronomy | ||||||||||||||||||||||||||||||||||||||||||||||||
Divisions: | Faculty of Science, Engineering and Medicine > Science > Physics | ||||||||||||||||||||||||||||||||||||||||||||||||
Library of Congress Subject Headings (LCSH): | Stars -- Formation, Extrasolar planets -- Detection, Photometry, Astrophysics, Dwarf stars | ||||||||||||||||||||||||||||||||||||||||||||||||
Journal or Publication Title: | Astronomy & Astrophysics | ||||||||||||||||||||||||||||||||||||||||||||||||
Publisher: | EDP Sciences | ||||||||||||||||||||||||||||||||||||||||||||||||
ISSN: | 0004-6361 | ||||||||||||||||||||||||||||||||||||||||||||||||
Official Date: | 7 January 2022 | ||||||||||||||||||||||||||||||||||||||||||||||||
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Volume: | 657 | ||||||||||||||||||||||||||||||||||||||||||||||||
Page Range: | A45 | ||||||||||||||||||||||||||||||||||||||||||||||||
DOI: | 10.1051/0004-6361/202142280 | ||||||||||||||||||||||||||||||||||||||||||||||||
Status: | Peer Reviewed | ||||||||||||||||||||||||||||||||||||||||||||||||
Publication Status: | Published | ||||||||||||||||||||||||||||||||||||||||||||||||
Access rights to Published version: | Open Access (Creative Commons) | ||||||||||||||||||||||||||||||||||||||||||||||||
Date of first compliant deposit: | 2 March 2022 | ||||||||||||||||||||||||||||||||||||||||||||||||
Date of first compliant Open Access: | 2 March 2022 | ||||||||||||||||||||||||||||||||||||||||||||||||
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