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

N. Schanche; F. J. Pozuelos; M. N. Günther; R. D. Wells; A. J. Burgasser; P. Chinchilla; L. Delrez; E. Ducrot; L. J. Garcia; Y. Gómez Maqueo Chew; E. Jofré; B. V. Rackham; D. Sebastian; K. G. Stassun; D. Stern; M. Timmermans; K. Barkaoui; A. Belinski; Z. Benkhaldoun; W. Benz; D. Charbonneau; Jessie L. Christiansen; Karen A. Collins; B. -O. Demory; M. Dévora-Pajares; J. de Wit; D. Dragomir; G. Dransfield; E. Furlan; M. Ghachou; M. Gillon; C. Gnilka; M. A. Gómez-Muñoz; N. Guerrero; M. Harris; K. Heng; C. E. Henze; K. Hesse; S. B. Howell; E. Jehin; J. Jenkins; Eric L. N. Jensen; M. Kunimoto; D. W. Latham; K. Lester; Kim K. McLeod; I. Mireles; C. A. Murray; P. Niraula; P. P. Pedersen; D. Queloz; E. V. Quintana; G. Ricker; A. Rudat; L. Sabin; B. Safonov; U. Schroffenegger; N. Scott; S. Seager; I. Strakhov; A. H. M. J. Triaud; R. Vanderspek; M. Vezie; J. Winn

doi:10.1051/0004-6361/202142280

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

N. Schanche, F. J. Pozuelos, M. N. Günther, R. D. Wells, A. J. Burgasser, P. Chinchilla, L. Delrez, E. Ducrot, L. J. Garcia, Y. Gómez Maqueo Chew, E. Jofré, B. V. Rackham, D. Sebastian, K. G. Stassun, D. Stern, M. Timmermans, K. Barkaoui, A. Belinski, Z. Benkhaldoun, W. BenzD. Charbonneau, Jessie L. Christiansen, Karen A. Collins, B. -O. Demory, M. Dévora-Pajares, J. de Wit, D. Dragomir, G. Dransfield, E. Furlan, M. Ghachou, M. Gillon, C. Gnilka, M. A. Gómez-Muñoz, N. Guerrero, M. Harris, K. Heng, C. E. Henze, K. Hesse, S. B. Howell, E. Jehin, J. Jenkins, Eric L. N. Jensen, M. Kunimoto, D. W. Latham, K. Lester, Kim K. McLeod, I. Mireles, C. A. Murray, P. Niraula, P. P. Pedersen, D. Queloz, E. V. Quintana, G. Ricker, A. Rudat, L. Sabin, B. Safonov, U. Schroffenegger, N. Scott, S. Seager, I. Strakhov, A. H. M. J. Triaud, R. Vanderspek, M. Vezie, J. Winn

Physics and Astronomy

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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 (K_mag = 10.7) make it a suitable candidate for atmospheric exploration via transmission spectroscopy.

Original language	English
Article number	A45
Journal	Astronomy and Astrophysics
Volume	657
DOIs	https://doi.org/10.1051/0004-6361/202142280
Publication status	Published - 7 Jan 2022

Keywords

astro-ph.EP

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

@article{0734e5b78ddc419493ffa1a8f5194701,

title = "TOI-2257 b: a highly eccentric long-period sub-Neptune transiting a nearby M dwarf",

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{\textquoteright}s low equilibrium temperature (~256 K), its host star{\textquoteright}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.",

keywords = "astro-ph.EP",

author = "N. Schanche and Pozuelos, {F. J.} and G{\"u}nther, {M. N.} and Wells, {R. D.} and Burgasser, {A. J.} and P. Chinchilla and L. Delrez and E. Ducrot and Garcia, {L. J.} and Chew, {Y. G{\'o}mez Maqueo} and E. Jofr{\'e} and Rackham, {B. V.} and D. Sebastian and Stassun, {K. G.} and D. Stern and M. Timmermans and K. Barkaoui and A. Belinski and Z. Benkhaldoun and W. Benz and D. Charbonneau and Christiansen, {Jessie L.} and Collins, {Karen A.} and Demory, {B. -O.} and M. D{\'e}vora-Pajares and Wit, {J. de} and D. Dragomir and G. Dransfield and E. Furlan and M. Ghachou and M. Gillon and C. Gnilka and G{\'o}mez-Mu{\~n}oz, {M. A.} and N. Guerrero and M. Harris and K. Heng and Henze, {C. E.} and K. Hesse and Howell, {S. B.} and E. Jehin and J. Jenkins and Jensen, {Eric L. N.} and M. Kunimoto and Latham, {D. W.} and K. Lester and McLeod, {Kim K.} and I. Mireles and Murray, {C. A.} and P. Niraula and Pedersen, {P. P.} and D. Queloz and Quintana, {E. V.} and G. Ricker and A. Rudat and L. Sabin and B. Safonov and U. Schroffenegger and N. Scott and S. Seager and I. Strakhov and Triaud, {A. H. M. J.} and R. Vanderspek and M. Vezie and J. Winn",

year = "2022",

month = jan,

day = "7",

doi = "10.1051/0004-6361/202142280",

language = "English",

volume = "657",

journal = "Astronomy and Astrophysics",

issn = "0004-6361",

publisher = "EDP Sciences",

}

Schanche, N, Pozuelos, FJ, Günther, MN, Wells, RD, Burgasser, AJ, Chinchilla, P, Delrez, L, Ducrot, E, Garcia, LJ, Chew, YGM, Jofré, E, Rackham, BV, Sebastian, D, Stassun, KG, Stern, D, Timmermans, M, Barkaoui, K, Belinski, A, Benkhaldoun, Z, Benz, W, Charbonneau, D, Christiansen, JL, Collins, KA, Demory, B-O, Dévora-Pajares, M, Wit, JD, Dragomir, D, Dransfield, G, Furlan, E, Ghachou, M, Gillon, M, Gnilka, C, Gómez-Muñoz, MA, Guerrero, N, Harris, M, Heng, K, Henze, CE, Hesse, K, Howell, SB, Jehin, E, Jenkins, J, Jensen, ELN, Kunimoto, M, Latham, DW, Lester, K, McLeod, KK, Mireles, I, Murray, CA, Niraula, P, Pedersen, PP, Queloz, D, Quintana, EV, Ricker, G, Rudat, A, Sabin, L, Safonov, B, Schroffenegger, U, Scott, N, Seager, S, Strakhov, I, Triaud, AHMJ, Vanderspek, R, Vezie, M & Winn, J 2022, 'TOI-2257 b: a highly eccentric long-period sub-Neptune transiting a nearby M dwarf', Astronomy and Astrophysics, vol. 657, A45. https://doi.org/10.1051/0004-6361/202142280

TY - JOUR

T1 - TOI-2257 b

T2 - a highly eccentric long-period sub-Neptune transiting a nearby M dwarf

AU - Schanche, N.

AU - Pozuelos, F. J.

AU - Günther, M. N.

AU - Wells, R. D.

AU - Burgasser, A. J.

AU - Chinchilla, P.

AU - Delrez, L.

AU - Ducrot, E.

AU - Garcia, L. J.

AU - Chew, Y. Gómez Maqueo

AU - Jofré, E.

AU - Rackham, B. V.

AU - Sebastian, D.

AU - Stassun, K. G.

AU - Stern, D.

AU - Timmermans, M.

AU - Barkaoui, K.

AU - Belinski, A.

AU - Benkhaldoun, Z.

AU - Benz, W.

AU - Charbonneau, D.

AU - Christiansen, Jessie L.

AU - Collins, Karen A.

AU - Demory, B. -O.

AU - Dévora-Pajares, M.

AU - Wit, J. de

AU - Dragomir, D.

AU - Dransfield, G.

AU - Furlan, E.

AU - Ghachou, M.

AU - Gillon, M.

AU - Gnilka, C.

AU - Gómez-Muñoz, M. A.

AU - Guerrero, N.

AU - Harris, M.

AU - Heng, K.

AU - Henze, C. E.

AU - Hesse, K.

AU - Howell, S. B.

AU - Jehin, E.

AU - Jenkins, J.

AU - Jensen, Eric L. N.

AU - Kunimoto, M.

AU - Latham, D. W.

AU - Lester, K.

AU - McLeod, Kim K.

AU - Mireles, I.

AU - Murray, C. A.

AU - Niraula, P.

AU - Pedersen, P. P.

AU - Queloz, D.

AU - Quintana, E. V.

AU - Ricker, G.

AU - Rudat, A.

AU - Sabin, L.

AU - Safonov, B.

AU - Schroffenegger, U.

AU - Scott, N.

AU - Seager, S.

AU - Strakhov, I.

AU - Triaud, A. H. M. J.

AU - Vanderspek, R.

AU - Vezie, M.

AU - Winn, J.

PY - 2022/1/7

Y1 - 2022/1/7

N2 - 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.

AB - 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.

KW - astro-ph.EP

UR - http://www.scopus.com/inward/record.url?scp=85122883933&partnerID=8YFLogxK

U2 - 10.1051/0004-6361/202142280

DO - 10.1051/0004-6361/202142280

M3 - Article

SN - 0004-6361

VL - 657

JO - Astronomy and Astrophysics

JF - Astronomy and Astrophysics

M1 - A45

ER -

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

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