Validation and atmospheric exploration of the sub-Neptune TOI-2136b around a nearby M3 dwarf

Full list of authors: Kawauchi, K.; Murgas, F.; Palle, E.; Narita, N.; Fukui, A.; Hirano, T.; Parviainen, H.; Ishikawa, H. T.; Watanabe, N.; Esparaza-Borges, E.; Kuzuhara, M.; Orell-Miquel, J.; Krishnamurthy, V; Mori, M.; Kagetani, T.; Zou, Y.; Isogai, K.; Livingston, J. H.; Howell, S. B.; Crouzet, N.; de Leon, J. P.; Kimura, T.; Kodama, T.; Korth, J.; Kurita, S.; Laza-Ramos, A.; Luque, R.; Madrigal-Aguado, A.; Miyakawa, K.; Morello, G.; Nishiumi, T.; Rodriguez, G. E. F.; Sanchez-Benavente, M.; Stangret, M.; Teng, H.; Terada, Y.; Gnilka, C. L.; Guerrero, N.; Harakawa, H.; Hodapp, K.; Hori, Y.; Ikoma, M.; Jacobson, S.; Konishi, M.; Kotani, T.; Kudo, T.; Kurokowa, T.; Kusakabe, N.; Nishikawa, J.; Omiya, M.; Serizawa, T.; Tamura, M.; Ueda, A.; Vievard, S.--This is an 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.
Context. The NASA space telescope TESS is currently in the extended mission of its all-sky search for new transiting planets. Of the thousands of candidates that TESS is expected to deliver, transiting planets orbiting nearby M dwarfs are particularly interesting targets since they provide a great opportunity to characterize their atmospheres by transmission spectroscopy. Aims. We aim to validate and characterize the new sub-Neptune-sized planet candidate TOI-2136.01 orbiting a nearby M dwarf (d = 33.36 ± 0.02pc, Teff = 3373 ± 108 K) with an orbital period of 7.852 days. Methods. We use TESS data, ground-based multicolor photometry, and radial velocity measurements with the InfraRed Doppler (IRD) instrument on the Subaru Telescope to validate the planetary nature of TOI-2136.01, and estimate the stellar and planetary parameters. We also conduct high-resolution transmission spectroscopy to search for helium in its atmosphere. Results. We confirm that TOI-2136.01 (now named TOI-2136b) is a bona fide planet with a planetary radius of Rp = 2.20 ± 0.07R⊕ and a mass of Mp = 4.7−2.6+3.1 M⊕. We also search for helium 10830 Å absorption lines and place an upper limit on the equivalent width of
The MEarth Project acknowledges funding from the David and Lucile Packard Fellowship for Science and Engineering, the National Science Foundation under grants AST-0807690, AST-1109468, AST-1616624 and AST-1004488 (Alan T. Waterman Award), the National Aeronautics and Space Administration under Grant No. 80NSSC18K0476 issued through the XRP Program, and the John Templeton Foundation. Based on observations obtained with the Samuel Oschin 48-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. Z.T.F. is supported by the National Science Foundation under Grant No. AST-1440341 and a collaboration including Caltech, IPAC, the Weizmann Institute for Science, the Oskar Klein Center at Stockholm University, the University of Maryland, the University of Washington, Deutsches Elektronen-Synchrotron and Humboldt University, Los Alamos National Laboratories, the TANGO Consortium of Taiwan, the University of Wisconsin at Milwaukee, and Lawrence Berkeley National Laboratories. Operations are conducted by COO, IPAC, and UW. Our data reductions benefited from PyRAF and PyFITS that are the products of the Space Telescope Science Institute, which is operated by AURA for NASA. G.M. has received funding from the European Union’s Horizon 2020 research and innovation programme under the Marie Sklodowska-Curie grant agreement No. 895525. R.L. acknowledges financial support from the Spanish Ministerio de Ciencia e Innovación, through project PID2019-109522GB-C52, and the Centre of Excellence “Severo Ochoa” award to the Instituto de Astrofísica de Andalucía (SEV-2017-0709). J.K. gratefully acknowledge the support of the Swedish National Space Agency (SNSA; DNR 2020-00104). This work is partly supported by JSPS KAKENHI Grant Numbers JP21K20376, JP21K13975, JP21H00035, JP21K20388, JP20K14518, JP20K14521, JP19K14783, JP18H05439, JP17H04574, by Grant-in-Aid for JSPS Fellows Grant Number JP20J21872, by JST CREST Grant Number JPMJCR1761, by Astrobiology Center PROJECT Research AB031014, by Astrobiology Center SATELLITE Research project AB022006, and the Astrobiology Center of National Institutes of Natural Sciences (NINS) (Grant Number AB031010). M.T. is supported by MEXT/JSPS KAKENHI grant Nos. 18H05442, 15H02063, and 22000005. Some of the observations in the paper made use of the High-Resolution Imaging instrument Alopeke obtained under Gemini LLP Proposal Number: GN/S-2021A-LP-105. Alopeke was funded by the NASA Exoplanet Exploration Program and built at the NASA Ames Research Center by Steve B. Howell, Nic Scott, Elliott P. Horch, and Emmett Quigley. Alopeke was mounted on the Gemini North (and/or South) telescope of the international Gemini Observatory, a program of NSF’s OIR Lab, which is managed by the Association of Universities for Research in Astronomy (AURA) under a cooperative agreement with the National Science Foundation, on behalf of the Gemini partnership: the National Science Foundation (United States), National Research Council (Canada), Agencia Nacional de Investigación y Desarrollo (Chile), Mnisterio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea).