A planetary system with two transiting mini-Neptunes near the radius valley transition around the bright M dwarf TOI-776

Luque, R.; Serrano, L. M.; Molaverdikhani, K.; Nixon, M. C.; Livingston, J. H.; Guenther, E. W.; Pallé, E.; Madhusudhan, N.; Nowak, G.; Korth, J.; Cochran, W. D.; Hirano, T.; Chaturvedi, P.; Goffo, E.; Albrecht, S.; Barragán, O.; Briceño, C.; Cabrera, J.; Charbonneau, D.; Cloutier, R.; Collins, K. A.; Collins, K. I.; Colón, K. D.; Crossfield, I. J. M.; Csizmadia, Sz.; Dai, F.; Deeg, H. J.; Esposito, M.; Fridlund, M.; Gandolfi, D.; Georgieva, I.; Glidden, A.; Goeke, R. F.; Grziwa, S.; Hatzes, A. P.; Henze, C. E.; Howell, S. B.; Irwin, J.; Jenkins, J. M.; Jensen, E. L. N.; Kábath, P.; Kidwell, R. C.; Kielkopf, J. F.; Knudstrup, E.; Lam, K. W. F.; Latham, D. W.; Lissauer, J. J.; Mann, A. W.; Matthews, E. C.; Mireles, I.; Narita, N.; Paegert, M.; Persson, C. M.; Redfield, S.; Ricker, G. R.; Rodler, F.; Schlieder, J. E.; Scott, N. J.; Seager, S.; Šubjak, J.; Tan, T. G.; Ting, E. B.; Vanderspek, R.; Van Eylen, V.; Winn, J. N.; Ziegler, C.
Referencia bibliográfica

Astronomy and Astrophysics

Fecha de publicación:
1
2021
Número de autores
66
Número de autores del IAC
5
Número de citas
40
Número de citas referidas
39
Descripción
We report the discovery and characterization of two transiting planets around the bright M1 V star LP 961-53 (TOI-776, J = 8.5 mag, M = 0.54 ± 0.03 M ☉) detected during Sector 10 observations of the Transiting Exoplanet Survey Satellite (TESS). Combining the TESS photometry with HARPS radial velocities, as well as ground-based follow-up transit observations from the MEarth and LCOGT telescopes, for the inner planet, TOI-776 b, we measured a period of P b = 8.25 d, a radius of R b = 1.85 ± 0.13 R ⊕, and a mass of M b = 4.0 ± 0.9 M ⊕; and for the outer planet, TOI-776 c, a period of P c = 15.66 d, a radius of R c = 2.02 ± 0.14 R ⊕, and a mass of M c = 5.3 ± 1.8 M ⊕. The Doppler data shows one additional signal, with a period of ~34 d, associated with the rotational period of the star. The analysis of fifteen years of ground-based photometric monitoring data and the inspection of different spectral line indicators confirm this assumption. The bulk densities of TOI-776 b and c allow for a wide range of possible interior and atmospheric compositions. However, both planets have retained a significant atmosphere, with slightly different envelope mass fractions. Thanks to their location near the radius gap for M dwarfs, we can start to explore the mechanism(s) responsible for the radius valley emergence around low-mass stars as compared to solar-like stars. While a larger sample of well-characterized planets in this parameter space is still needed to draw firm conclusions, we tentatively estimate that the stellar mass below which thermally-driven mass loss is no longer the main formation pathway for sculpting the radius valley is between 0.63 and 0.54 M ☉. Due to the brightness of the star, the TOI-776 system is also an excellent target for the James Webb Space Telescope, providing a remarkable laboratory in which to break the degeneracy in planetary interior models and to test formation and evolution theories of small planets around low-mass stars.

Based on observations made with ESO Telescopes at the La Silla Observatory under programs ID 1102.C-0923 and 60.A-9709.

Proyectos relacionados
Helio and Asteroseismologia
Sismología Solar y Estelar y Búsqueda de Exoplanetas
Los objetivos genéricos de este Proyecto son: 1) el estudio de la estructura y dinámica del interior solar, 2) la extensión de dicho estudio al caso de otras estrellas, 3) la búsqueda y caracterización de planetas extrasolares por métodos fotométricos (principalmente mediante el método de tránsitos) y espectroscópico (variaciones en la velocidad
Savita
Mathur
Image withthe projects' name
Exoplanetas y Astrobiología
La búsqueda de vida en el Universo se ha visto impulsada por los recientes descubrimientos de planetas alrededor de otras estrellas (los llamados exoplanetas), convirtiéndose en uno de los campos más activos dentro de la Astrofísica moderna. En los últimos años los descubrimientos cada vez más numerosos de nuevos exoplanetas y los últimos avances
Enric
Pallé Bago