TOI-2257 b: A highly eccentric long-period sub-Neptune transiting a nearby M dwarf

Schanche, N.; Pozuelos, F. J.; Günther, M. N.; Wells, R. D.; Burgasser, A. J.; Chinchilla, P.; Delrez, L.; Ducrot, E.; Garcia, L. J.; Gómez Maqueo Chew, Y.; Jofré, E.; Rackham, B. V.; Sebastian, D.; Stassun, K. G.; Stern, D.; Timmermans, M.; Barkaoui, K.; Belinski, A.; Benkhaldoun, Z.; Benz, W.; ... (2022). TOI-2257 b: A highly eccentric long-period sub-Neptune transiting a nearby M dwarf. Astronomy and astrophysics, 657(A45), A45. EDP Sciences 10.1051/0004-6361/202142280

[img]
Preview
Text
2111.01749.pdf - Accepted Version
Available under License Publisher holds Copyright.

Download (2MB) | Preview
[img] Text
aa42280-21.pdf - Published Version
Restricted to registered users only
Available under License Publisher holds Copyright.

Download (2MB) | Request a copy

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 make such objects particularly compelling as they provide clues about the formation and evolution of these systems. 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 57.8pc. 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 that is known to be transiting an M-dwarf star. We combined TESS and ground-based data obtained with the 1.0-m SAINT-EX, 0.60-m TRAPPIST-North and 1.2-m 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. With its long period and high eccentricity, TOI-2257 b falls in 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 (Original Article)

Division/Institute:

10 Strategic Research Centers > Center for Space and Habitability (CSH)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences > Theoretical Astrophysics and Planetary Science (TAPS)
08 Faculty of Science > Physics Institute > Space Research and Planetary Sciences
08 Faculty of Science > Physics Institute
08 Faculty of Science > Physics Institute > NCCR PlanetS

UniBE Contributor:

Schanche, Nicole Elizabeth; Wells, Robert Donald; Benz, Willy; Demory, Brice-Olivier and Heng, Kevin

Subjects:

500 Science > 520 Astronomy
500 Science
500 Science > 530 Physics
600 Technology > 620 Engineering

ISSN:

0004-6361

Publisher:

EDP Sciences

Language:

English

Submitter:

Janine Jungo

Date Deposited:

23 Mar 2022 15:55

Last Modified:

27 Mar 2022 01:56

Publisher DOI:

10.1051/0004-6361/202142280

BORIS DOI:

10.48350/166568

URI:

https://boris.unibe.ch/id/eprint/166568

Actions (login required)

Edit item Edit item
Provide Feedback