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A sub-Neptune planet around TOI-1695 discovered and characterized with SPIRou and TESS

F. Kiefer, G. Hébrard, E. Martioli, E. Artigau, R. Doyon, J.-F. Donati, C. Cadieux, A. Carmona, D. Ciardi, P. Cristofari, Leandro de Almeida, P. Figueira, E. Gaidos, E. J. Gonzales, A. Lecavelier Des Etangs, K. G. Stassun, L. Arnold, B. Benneke, I. Boisse, X. Bonfils, N. J. Cook, P. Cortés-Zuleta, X. Delfosse, J. D. do Nascimento Jr., M. M. Fausnaugh, W. Fong, P. Fouqué, T. Forveille, J. Gomes da Silva, K. Hesse, Á. Kóspál, H. Lewis, C. -F. Liu, J. H. C. Martins, M. Paegert, S. Seager, H. Shang, J. D. Twicken, T. Vandal, S. Vinatier, T. Widemann, J. N. Winn

TOI-1695 is a V-mag = 13 M-dwarf star from the northern hemisphere at 45 pc from the Sun, around which a 3.134-day periodic transit signal from a super-Earth candidate was identified in TESS photometry. With a transit depth of 1.3 mmag, the radius of candidate TOI-1695.01 was estimated by the TESS pipeline to be 1.82 R with an equilibrium temperature of ~620 K. We successfully detected a reflex motion of the star and establish that it is due to a planetary companion at an orbital period consistent with the photometric transit period, thanks to a year-long radial-velocity monitoring of TOI-1695 by the SPIRou infrared spectropolarimeter. We used and compared different methods to reduce and analyze those data. We report a 5.5σ detection of the planetary signal, giving a mass of 5.5±1.0 M and a radius of 2.03±0.18 R. We derive a mean equilibrium planet temperature of 590±90 K. The mean density of this small planet of 3.6±1.1 g cm−3 is similar (1.7σ lower) than that of the Earth. It leads to a nonnegligible fraction of volatiles in its atmosphere with fH,He = 0.28−0.23+0.46% or fwater = 23±12%. TOI-1695 b is a new sub-Neptune planet at the border of the M-dwarf radius valley that can help test formation scenarios for super-Earth and sub-Neptune-like planets.

planets and satellites: detection / planets and satellites: fundamental parameters / planets and satellites: individual: TOI-1695 b / techniques: photometric / techniques: radial velocities

Astronomy & Astrophysics
Volume 670, Article Number A136, Number of pages 28
2023 February

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Faculdade de Ciências da Universidade de Lisboa Universidade do Porto Faculdade de Ciências e Tecnologia da Universidade de Coimbra
Fundação para a Ciência e a Tecnologia COMPETE 2020 PORTUGAL 2020 União Europeia