A planetary system with two transiting mini-Neptunes near the radius valley transition around the bright M dwarf TOI-776
(2021) In Astronomy and Astrophysics 645.- Abstract
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 Pb = 8.25 d, a radius of Rb = 1.85 ± 0.13 R⊙, and a mass of Mb = 4.0 ± 0.9 M⊙; and for the outer planet, TOI-776 c, a period of Pc = 15.66 d, a radius of Rc = 2.02 ± 0.14 R⊙, and a mass of Mc = 5.3 ± 1.8 M⊙. The Doppler data shows one additional signal, with a period of ~34 d, associated... (More)
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 Pb = 8.25 d, a radius of Rb = 1.85 ± 0.13 R⊙, and a mass of Mb = 4.0 ± 0.9 M⊙; and for the outer planet, TOI-776 c, a period of Pc = 15.66 d, a radius of Rc = 2.02 ± 0.14 R⊙, and a mass of Mc = 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.
(Less)
- author
- publishing date
- 2021-01-01
- type
- Contribution to journal
- publication status
- published
- keywords
- Planetary systems, Stars: individual: LP 961-53, Stars: low-mass, Techniques: photometric, Techniques: radial velocities
- in
- Astronomy and Astrophysics
- volume
- 645
- article number
- A41
- publisher
- EDP Sciences
- external identifiers
-
- scopus:85099057388
- ISSN
- 0004-6361
- DOI
- 10.1051/0004-6361/202039455
- language
- English
- LU publication?
- no
- additional info
- Publisher Copyright: © ESO 2021.
- id
- 0c3d19ad-ca69-49b8-9c28-30895a1f63d8
- date added to LUP
- 2023-02-01 10:35:32
- date last changed
- 2023-02-21 10:18:24
@article{0c3d19ad-ca69-49b8-9c28-30895a1f63d8,
abstract = {{<p>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 Pb = 8.25 d, a radius of Rb = 1.85 ± 0.13 R⊙, and a mass of Mb = 4.0 ± 0.9 M⊙; and for the outer planet, TOI-776 c, a period of Pc = 15.66 d, a radius of Rc = 2.02 ± 0.14 R⊙, and a mass of Mc = 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.</p>}},
author = {{Luque, R. and Serrano, L. M. and Molaverdikhani, K. and Nixon, M. C. and Livingston, J. H. and Guenther, E. W. and Pallé, E. and Madhusudhan, N. and Nowak, G. and Korth, J. and Cochran, W. D. and Hirano, T. and Chaturvedi, P. and Goffo, E. and Albrecht, S. and Barragán, O. and Briceño, C. and Cabrera, J. and Charbonneau, D. and Cloutier, R. and Collins, K. A. and Collins, K. I. and Colón, K. D. and Crossfield, I. J.M. and Csizmadia, Sz and Dai, F. and Deeg, H. J. and Esposito, M. and Fridlund, M. and Gandolfi, D. and Georgieva, I. and Glidden, A. and Goeke, R. F. and Grziwa, S. and Hatzes, A. P. and Henze, C. E. and Howell, S. B. and Irwin, J. and Jenkins, J. M. and Jensen, E. L.N. and Kábath, P. and Kidwell, R. C. and Kielkopf, J. F. and Knudstrup, E. and Lam, K. W.F. and Latham, D. W. and Lissauer, J. J. and Mann, A. W. and Matthews, E. C. and Mireles, I. and Narita, N. and Paegert, M. and Persson, C. M. and Redfield, S. and Ricker, G. R. and Rodler, F. and Schlieder, J. E. and Scott, N. J. and Seager, S. and Šubjak, J. and Tan, T. G. and Ting, E. B. and Vanderspek, R. and Van Eylen, V. and Winn, J. N. and Ziegler, C.}},
issn = {{0004-6361}},
keywords = {{Planetary systems; Stars: individual: LP 961-53; Stars: low-mass; Techniques: photometric; Techniques: radial velocities}},
language = {{eng}},
month = {{01}},
publisher = {{EDP Sciences}},
series = {{Astronomy and Astrophysics}},
title = {{A planetary system with two transiting mini-Neptunes near the radius valley transition around the bright M dwarf TOI-776}},
url = {{http://dx.doi.org/10.1051/0004-6361/202039455}},
doi = {{10.1051/0004-6361/202039455}},
volume = {{645}},
year = {{2021}},
}