Hot planets around cool stars – two short-period mini-Neptunes transiting the late K-dwarf TOI-1260

Creators: Georgieva, I. Y.; Persson, C. M.; Barragán, O.; Nowak, G.; Fridlund, M.; Locci, D.; Palle, E.; Luque, R.; Carleo, I.; Gandolfi, D.; Kane, S. R.; Korth, J.; Stassun, K. G.; Livingston, J.; Matthews, E. C.; Collins, K. A.; Howell, S. B.; Serrano, L. M.; Albrecht, S.; Bieryla, A.; Brasseur, C. E.; Ciardi, D. R.; Cochran, W. D.; Colón, K. D.; Crossfield, I. J. M.; Csizmadia, Sz.; Deeg, H. J.; Esposito, M.; Furlan, E.; Gan, T.; Goffo, E.; Gonzales, E.; Grziwa, S.; Guenther, E. W.; Guerra, P.; Hirano, T.; Jenkins, J. M.; Jensen, E. L. N.; Kabáth, P.; Knudstrup, E.; Lam, K. W. F.; Latham, D. W.; Levine, A. M.; Matson, R. A.; McDermott, S.; Osborne, H. L. M.; Paegert, M.; Quinn, S. N.; Redfield, S.; Ricker, G. R.; Schlieder, J. E.; Scott, N. J.; Seager, S.; Smith, A. M. S.; Tenenbaum, P.; Twicken, J. D.; Vanderspek, R.; Van Eylen, V.; Winn, J. N.

Abstract

We present the discovery and characterization of two sub-Neptunes in close orbits, as well as a tentative outer planet of a similar size, orbiting TOI-1260 – a low metallicity K6 V dwarf star. Photometry from Transiting Exoplanet Survey Satellite(TESS) yields radii of R_b = 2.33 ± 0.10 and R_c = 2.82 ± 0.15 R⊕, and periods of 3.13 and 7.49 d for TOI-1260 b and TOI-1260 c, respectively. We combined the TESS data with a series of ground-based follow-up observations to characterize the planetary system. From HARPS-N high-precision radial velocities we obtain M_b = 8.6^(+1.4)_(−1.5) and M_c = 11.8^(+3.4)_(−3.2) M⊕. The star is moderately active with a complex activity pattern, which necessitated the use of Gaussian process regression for both the light-curve detrending and the radial velocity modelling, in the latter case guided by suitable activity indicators. We successfully disentangle the stellar-induced signal from the planetary signals, underlining the importance and usefulness of the Gaussian process approach. We test the system's stability against atmospheric photoevaporation and find that the TOI-1260 planets are classic examples of the structure and composition ambiguity typical for the 2–3 R⊕ range.

Additional Information

© 2021 The Author(s). Published by Oxford University Press on behalf of Royal Astronomical Society. This article is published and distributed under the terms of the Oxford University Press, Standard Journals Publication Model (https://academic.oup.com/journals/pages/open_access/funder_policies/chorus/standard_publication_model). Accepted 2021 May 15. Received 2021 May 6; in original form 2020 December 18. Published: 22 May 2021. This work is done under the framework of the KESPRINT collaboration (http://kesprint.science). KESPRINT is an international consortium devoted to the characterization and research of exoplanets discovered with space-based missions. IYG, CMP, MF, and JK gratefully acknowledge the support of the Swedish National Space Agency (DNR 174/18, 65/19, 2020-00104). KWFM and ME acknowledge the support of the German Research Foundation (DFG) priority program SPP 1992 'Exploring the Diversity of Extrasolar Planets' (RA714/14-1, HA3279/12-1). HD acknowledges support from the Spanish Research Agency of the Ministry of Science and Innovation (AEI-MICINN) under grant PID2019-107061GB-C66, DOI: 10.13039/501100011033. This work was supported by the Thüringer Ministerium für Wirtschaft, Wissenschaft und Digitale Gesellschaft. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work makes use of observations from the LCOGT network. Some of the Observations in the paper made use of the High-Resolution Imaging instrument 'Alopeke. '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 is mounted on the Gemini North telescope of the international Gemini Observatory, a program of NOIRLab, 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), Ministerio de Ciencia, Tecnología e Innovación (Argentina), Ministério da Ciência, Tecnologia, Inovações e Comunicações (Brazil), and Korea Astronomy and Space Science Institute (Republic of Korea). This paper includes data collected by the TESS mission. Funding for the TESS mission is provided by the NASA Explorer Program. We acknowledge the use of public TOI Release data from pipelines at the TESS Science Office and at the TESS Science Processing Operations Center. Resources supporting this work were provided by the NASA High-End Computing (HEC) Program through the NASA Advanced Supercomputing (NAS) Division at Ames Research Center for the production of the SPOC data products. This research has made use of the Exoplanet Follow-up Observation Program website, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program. This work has made use of data from the European Space Agency (ESA) mission Gaia (https://www.cosmos.esa.int/gaia), processed by the Gaia Data Processing and Analysis Consortium (DPAC, https://www.cosmos.esa.int/web/gaia/dpac/consortium). Funding for the DPAC has been provided by national institutions, in particular the institutions participating in the Gaia Multilateral Agreement. This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI: 10.26093/cds/vizier). The original description of the VizieR service was published in Ochsenbein, Bauer & Marcout (2000). Based on observations made with the Italian Telescopio Nazionale Galileo (TNG) operated on the island of La Palma by the Fundación Galileo Galilei of the INAF (Istituto Nazionale di Astrofisica) at the Spanish Observatorio del Roque de los Muchachos of the Instituto de Astrofisica de Canarias under programmes CAT19A_162, ITP19_1 and A41TAC_49. Facility: TESS, Gaia, TNG/HARPS-N, LCOGT. Software:EXOTRANS, lightkurve, citlalicue, george, pytransit, IRAF, PARAM 1.5, SME, SpecMatch-emp, AstroImageJ, pyaneti, juliet, pyTTV. Data Availability: The data underlying this article are available in the article and in its online supplementary material, as well as ExoFOP-TESS.

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