planets and satellites: detection; stars: individual: TOI-2406; techniques: photometric; Astrophysics - Earth and Planetary Astrophysics
Abstract :
[en] Context. Large sub-Neptunes are uncommon around the coolest stars in the Galaxy and are rarer still around those that are metal-poor. However, owing to the large planet-to-star radius ratio, these planets are highly suitable for atmospheric study via transmission spectroscopy in the infrared, such as with JWST. Aims: Here we report the discovery and validation of a sub-Neptune orbiting the thick-disk, mid-M dwarf star TOI-2406. The star's low metallicity and the relatively large size and short period of the planet make TOI-2406 b an unusual outcome of planet formation, and its characterisation provides an important observational constraint for formation models. Methods: We first infer properties of the host star by analysing the star's near-infrared spectrum, spectral energy distribution, and Gaia parallax. We use multi-band photometry to confirm that the transit event is on-target and achromatic, and we statistically validate the TESS signal as a transiting exoplanet. We then determine physical properties of the planet through global transit modelling of the TESS and ground-based time-series data. Results: We determine the host to be a metal-poor M4 V star, located at a distance of 56 pc, with properties Teff = 3100 ± 75 K, M* = 0.162 ± 0.008M⊙, R* = 0.202 ± 0.011R⊙, and [Fe∕H] = −0.38 ± 0.07, and a member of the thick disk. The planet is a relatively large sub-Neptune for the M-dwarf planet population, with Rp = 2.94 ± 0.17R⊕ and P= 3.077 d, producing transits of 2% depth. We note the orbit has a non-zero eccentricity to 3σ, prompting questions about the dynamical history of the system. Conclusions: This system is an interesting outcome of planet formation and presents a benchmark for large-planet formation around metal-poor, low-mass stars. The system warrants further study, in particular radial velocity follow-up to determine the planet mass and constrain possible bound companions. Furthermore, TOI-2406 b is a good target for future atmospheric study through transmission spectroscopy. Although the planet's mass remains to be constrained, we estimate the S/N using amass-radius relationship, ranking the system fifth in the population of large sub-Neptunes, with TOI-2406 b having a much lower equilibrium temperature than other spectroscopically accessible members of this population.
Disciplines :
Space science, astronomy & astrophysics
Author, co-author :
Wells, R. D.; Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Rackham, B. V.; Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA ; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Schanche, N.; Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Petrucci, R.; Universidad Nacional de Córdoba - Observatorio Astronómico de Córdoba, Laprida 854, X5000BGR, Córdoba, Argentina ; Consejo Nacional de Investigaciones Cientf́icas y Técnicas (CONICET), Buenos Aires, Argentina
Gómez Maqueo Chew, Y.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 70-264, CDMX, 04510, México
Demory, B.-O.; Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Burgasser, A. J.; Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093, USA
Burn, R.; Max Planck Institute for Astronomy (MPIA), Koenigstuhl 17, 69117, Heidelberg, Germany
Pozuelos Romero, Francisco José ; Astrobiology Research Unit, Université de Liège, Allée du 6 Août 19C, 4000, Liège, Belgium ; Space Sciences, Technologies and Astrophysics Research (STAR) Institute, Universitďe Liège, Allée du 6 Août 19C, 4000, Liège, Belgium
Günther, M. N.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Sabin, L.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Schroffenegger, U.; Center for Space and Habitability, University of Bern, Gesellschaftsstrasse 6, 3012, Bern, Switzerland
Gómez-Muñoz, M. A.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Stassun, K. G.; Department of Physics & Astronomy, Vanderbilt University, 6301 Stevenson Center Ln., Nashville, TN 37235, USA
Van Grootel, Valérie ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Astrophysique stellaire théorique et astérosismologie
Howell, S. B.; NASA Ames Research Center, Moffett Field, CA 94035, USA
Sebastian, Daniel ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Triaud, A. H. M. J.; School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmimgham, B15 2TT, UK
Apai, D.; Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA ; Lunar and Planetary Laboratory, The University of Arizona, 1639 E. University Boulevard, Tucson, AZ 85721, USA
Plauchu-Frayn, I.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Guerrero, C. A.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Guillén, P. F.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Landa, A.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Melgoza, G.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Montalvo, F.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Serrano, H.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Riesgo, H.; Universidad Nacional Autónoma de México, Instituto de Astronomía, AP 106, Ensenada, 22800, BC, México
Barkaoui, Khalid ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Bixel, A.; Steward Observatory, The University of Arizona, 933 N. Cherry Avenue, Tucson, AZ 85721, USA
Burdanov, A.; Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
Chen, W. P.; Graduate Institute of Astronomy, National Central University, 300 Jhongda Road, Zhongli, Taoyuan, 32001, Taiwan
Chinchilla, P.; Astrobiology Research Unit, Université de Liège, Allée du 6 Août 19C, 4000, Liège, Belgium ; Instituto de Astrofísica de Canarias (IAC), Calle Vía Láctea s/n, 38200, La Laguna, Tenerife, Spain
Collins, K. A.; Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA, 02138, USA
Daylan, T.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
de Wit, J.; Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
Delrez, Laetitia ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Dévora-Pajares, M.; Dpto. Física Teórica y del Cosmos, Universidad de Granada, 18071, Granada, Spain
Dietrich, Jérémy
Dransfield, G.; School of Physics & Astronomy, University of Birmingham, Edgbaston, Birmimgham, B15 2TT, UK
Ducrot, Elsa ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Fausnaugh, M.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Furlan, E.; NASA Exoplanet Science Institute, Caltech/IPAC, Mail Code 100-22, 1200 E. California Blvd., Pasadena, CA 91125, USA
Gabor, P.; Vatican Observatory Research Group, University of Arizona, 933 N Cherry Ave., Tucson AZ, 85721-0065, USA
Gan, T.; Department of Astronomy, Tsinghua University, Beijing, 100084, PR China
Garcia, Lionel ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Ghachoui, M.; Oukaimeden Observatory, High Energy Physics and Astrophysics Laboratory, Cadi Ayyad University, Marrakech, Morocco
Giacalone, S.; Department of Astronomy, 501 Campbell Hall, University of California at Berkeley, Berkeley, CA, 94720, USA
Gibbs, A. B.; Department of Physics & Astronomy, University of California, Los Angeles, Los Angeles, CA 90095, USA
Gillon, Michaël ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Exotic
Gnilka, C.; NASA Ames Research Center, Moffett Field, CA 94035, USA
Gore, R.; Department of Astronomy, 501 Campbell Hall, University of California at Berkeley, Berkeley, CA, 94720, USA
Guerrero, N.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Henning, T.; Max Planck Institute for Astronomy (MPIA), Koenigstuhl 17, 69117, Heidelberg, Germany
Hesse, K.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Jehin, Emmanuel ; Université de Liège - ULiège > Département d'astrophys., géophysique et océanographie (AGO) > Origines Cosmologiques et Astrophysiques (OrCa)
Jenkins, J. M.; NASA Ames Research Center, Moffett Field, CA 94035, USA
Latham, D. W.; Center for Astrophysics, Harvard & Smithsonian, 60 Garden Street, Cambridge, MA, 02138, USA
Lester, K.; NASA Ames Research Center, Moffett Field, CA 94035, USA
McCormac, J.; Department of Physics, University of Warwick, Coventry, CV4 7AL, UK
Murray, C. A.; Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
Niraula, P.; Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA
Pedersen, P. P.; Cavendish Laboratory, JJ Thomson Avenue, Cambridge, CB3 0HE, UK
Ricker, G.; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
Rodriguez, D. R.; Space Telescope Science Institute, 3700 San Martin Drive, Baltimore, MD, 21218, USA
Schroeder, A.; Department of Astronomy, 501 Campbell Hall, University of California at Berkeley, Berkeley, CA, 94720, USA
Schwarz, R. P.; Patashnick Voorheesville Observatory, Voorheesville, NY 12186, USA
Scott, N.; NASA Ames Research Center, Moffett Field, CA 94035, USA
Seager, S.; Department of Earth, Atmospheric and Planetary Science, Massachusetts Institute of Technology, 77 Massachusetts Avenue, Cambridge, MA, 02139, USA ; Kavli Institute for Astrophysics and Space Research, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Physics, Massachusetts Institute of Technology, Cambridge, MA 02139, USA ; Department of Aeronautics and Astronautics, MIT, 77 Massachusetts Avenue, Cambridge, MA 02139, USA
Theissen, C. A.; Center for Astrophysics and Space Science, University of California San Diego, La Jolla, CA 92093, USA
Newton, E. R., Charbonneau, D., Irwin, J., et al. 2014, AJ, 147, 20
Ning, B., Wolfgang, A., & Ghosh, S. 2018, ApJ, 869, 5
Nutzman, P., & Charbonneau, D. 2008, PASP, 120, 317
Ormel, C. W., & Klahr, H. H. 2010, A&A, 520, A43
Parviainen, H. 2015, MNRAS, 450, 3233
Parviainen, H., & Aigrain, S. 2015, MNRAS, 453, 3821
Pascucci, I., Testi, L., Herczeg, G. J., et al. 2016, ApJ, 831, 125
Pepe, F. A., Cristiani, S., Rebolo Lopez, R., et al. 2010, SPIE Conf. Ser., 7735, 77350F
Petigura, E. A., Marcy, G. W., Winn, J. N., et al. 2018, AJ, 155, 89
Pollack, J. B., Hubickyj, O., Bodenheimer, P., et al. 1996, Icarus, 124, 62
Pozuelos, F. J., Suárez, J. C., de Eliá, G. C., et al. 2020, A&A, 641, A23
Rayner, J. T., Toomey, D. W., Onaka, P. M., et al. 2003, PASP, 115, 362
Rayner, J. T., Cushing, M. C., & Vacca, W. D. 2009, ApJS, 185, 289
Reid, I. N., Brewer, C., Brucato, R. J., et al. 1991, PASP, 103, 661
Reiners, A., Zechmeister, M., Caballero, J. A., et al. 2018, A&A, 612, A49
Ribas, I., Font-Ribera, A., & Beaulieu, J.-P. 2008, ApJ, 677, L59
Ribas, I., Font-Ribera, A., Beaulieu, J.-P., Morales, J. C., & Garciá-Melendo, E. 2009, IAU Symp., 253, 149
Ricker, G. R., Winn, J. N., Vanderspek, R., et al. 2015, J. Astron. Teles. Instrum. Syst., 1, 014003
Rodriguez, J. E., Becker, J. C., Eastman, J. D., et al. 2018, AJ, 156, 245
Sabin, L., Gómez Maqueo Chew, Y., Demory, B.-O., Petrucci, R., & Saint-Ex Consortium 2018, in 20th Cambridge Workshop on Cool Stars, Stellar Systems and the Sun, Cambridge Workshop on Cool Stars, Stellar Systems, and the Sun, 59
Santos, N. C., Israelian, G., & Mayor, M. 2004, A&A, 415, 1153
Schoonenberg, D., Liu, B., Ormel, C. W., & Dorn, C. 2019, A&A, 627, A149
Seager, S., & Sasselov, D. D. 2000, ApJ, 537, 916
Sebastian, D., Pedersen, P. P., Murray, C. A., et al. 2020, SPIE Conf. Ser., 11445, 1144521
Skrutskie, M. F., Cutri, R. M., Stiening, R., et al. 2006, AJ, 131, 1163
Smith, J. C., Stumpe, M. C., Van Cleve, J. E., et al. 2012, PASP, 124, 1000
Stassun, K. G., & Torres, G. 2016, AJ, 152, 180
Stassun, K. G., & Torres, G. 2021, ApJ, 907, L33
Stassun, K. G., Collins, K. A., & Gaudi, B. S. 2017, AJ, 153, 136
Stassun, K. G., Corsaro, E., Pepper, J. A., & Gaudi, B. S. 2018, AJ, 155, 22
Stassun, K. G., Oelkers, R. J., Paegert, M., et al. 2019, AJ, 158, 138
Stumpe, M. C., Smith, J. C., Van Cleve, J. E., et al. 2012, PASP, 124, 985
Stumpe, M. C., Smith, J. C., Catanzarite, J. H., et al. 2014, PASP, 126, 100
Twicken, J. D., Catanzarite, J. H., Clarke, B. D., et al. 2018, PASP, 130, 064502
Tychoniec, L., Tobin, J. J., Karska, A., et al. 2018, ApJS, 238, 19
Van Grootel, V., Fernandes, C. S., Gillon, M., et al. 2018, ApJ, 853, 30
Virtanen, P., Gommers, R., Oliphant, T. E., et al. 2020, Nat. Methods, 17, 261
Waskom, M., & The Seaborn Development Team 2021, J. Open Source Softw., 6, 3021
Wes McKinney. 2010, in Proceedings of the 9th Python in Science Conference, eds. S. van der Walt & J. Millman, 56
Wu, Y., Murray, N. W., & Ramsahai, J. M. 2007, ApJ, 670, 820
Zhang, K., & Hamilton, D. P. 2008, Icarus, 193, 267
