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

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

Abstract

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.

Additional Information

© The Authors 2023. Open Access article, published by EDP Sciences, under the terms of the Creative Commons Attribution License (https://creativecommons.org/licenses/by/4.0), which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. This article is published in open access under the Subscribe to Open model. Subscribe to A&A to support open access publication. The authors gratefully thank the anonymous referee for his corrections and suggestions that led to improve the content of this article. The authors wish to recognize and acknowledge the very significant cultural role and reverence that the summit of MaunaKea has always had within the indigenous Hawaiian community. We are most fortunate to have the opportunity to conduct observations from this mountain. This paper includes data collected by the TESS mission, which are publicly available from the Mikulski Archive for Space Telescopes (MAST). Funding for the TESS mission is provided by NASA's Science Mission directorate. S.T.Sc.I. is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 5-26555. We acknowledge funding from the French National Research Agency (ANR) under contract number ANR18CE310019 (SPlaSH). F.K. acknowledges support from the Université Paris Sciences et Lettres under the DIM-ACAV program Origines et conditions d'apparition de la vie. E.M. acknowledges funding from the Fundaçâo de Amparo à Pesquisa do Estado de Minas Gerais (FAPEMIG) under the project number APQ-02493-22. J.-F.D. acknowledges funding from the European Research Council (ERC) under the H2020 research & innovation programme (grant agreement #740651 NewWorlds). This work is partly supported by the French National Research Agency in the framework of the Investissements d'Avenir program (ANR-15-IDEX-02), through the funding of the "Origin of Life" project of the Grenoble-Alpes University. J.H.C.M. is supported in the form of a work contract funded by Fundaçâo para a Ciência e Tecnologia (FCT) with the reference DL 57/2016/CP1364/CT0007; and also supported from FCT through national funds and by FEDER-Fundo Europeu de Desenvolvimento Regional through COMPETE2020-Programa Operacional Competitividade e Internacionalização for these grants UIDB/04434/2020 & UIDP/04434/2020, PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113, PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953, PTDC/FIS-AST/29942/2017. J.H.C.M. also acknowleges the support from FCT – Fundaçâo para a Ciência e a Tecnologia through national funds and by FEDER through COMPETE2020 – Programa Operacional Competitividade e Internacionalizaçâo by these grants: UID/FIS/04434/2019; UIDB/04434/2020; UIDP/04434/2020; PTDC/FIS-AST/32113/2017 & POCI-01-0145-FEDER-032113; PTDC/FIS-AST/28953/2017 & POCI-01-0145-FEDER-028953.

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