Publication: A detailed analysis of the Gl 486 planetary system
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2022-09-20
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Caballero, J. A.
Tabernero Guzmán, Hugo Martín
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Abstract
Context. The Gl 486 system consists of a very nearby, relatively bright, weakly active M3.5 V star at just 8 pc with a warm transiting rocky planet of about 1.3 R_(⊕) and 3.0 M_(⊕). It is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets.
Aims. To prepare for future studies, we aim to thoroughly characterise the planetary system with new accurate and precise data collected with state-of-the-art photometers from space and spectrometers and interferometers from the ground.
Methods. We collected light curves of seven new transits observed with the CHEOPS space mission and new radial velocities obtained with MAROON-X at the 8.1 m Gemini North telescope and CARMENES at the 3.5 m Calar Alto telescope, together with previously published spectroscopic and photometric data from the two spectrographs and TESS. We also performed near-infrared interferometric observations with the CHARA Array and new photometric monitoring with a suite of smaller telescopes (AstroLAB, LCOGT, OSN, TJO). This extraordinary and rich data set was the input for our comprehensive analysis.
Results. From interferometry, we measure a limb-darkened disc angular size of the star Gl 486 at θ_(LDD) = 0.390 ± 0.018 mas. Together with a corrected Gaia EDR3 parallax, we obtain a stellar radius R_(*) = 0.339 ± 0.015 R_(ꙩ). We also measure a stellar rotation period at P_(rot) = 49.9 ± 5.5 days, an upper limit to its XUV (5–920 Å) flux informed by new Hubble/STIS data, and, for the first time, a variety of element abundances (Fe, Mg, Si, V, Sr, Zr, Rb) and C/O ratio. Moreover, we imposed restrictive constraints on the presence of additional components, either stellar or sub-stellar, in the system. With the input stellar parameters and the radial-velocity and transit data, we determine the radius and mass of the planet Gl 486 b at R_(p) = 1.343^(+0.063)_( −0.062) R_(⊕) and M_(p) = 3.00^(+0.13)_(−0.13) M_(⊕), with relative uncertainties of the planet radius and mass of 4.7% and 4.2%, respectively. From the planet parameters and the stellar element abundances, we infer the most probable models of planet internal structure and composition, which are consistent with a relatively small metallic core with respect to the Earth, a deep silicate mantle, and a thin volatile upper layer. With all these ingredients, we outline prospects for Gl 486 b atmospheric studies, especially with forthcoming James Webb Space Telescope (Webb) observations.
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© J. A. Caballero et al. 2022. Artículo firmado por 67 autores. We thank the reviewer for helpful comments, Kate Isaak for her support on CHEOPS observations, Mahmoudreza Oshagh for her preliminary transit-time variation analysis, David Ciardi for helpful comments on deep adaptive optics imaging, Vera M. Passegger for her Mg I fit, Sandra V. Jeffers for comments on stellar activity, and Joel Hartman, Greg W. Henry, Jonathan Irwin, and Chris G. Tinney for their information on HATNet, TSU, MEarth, and APT photometric data. CHEOPS is an ESA mission in partnership with Switzerland with important contributions to the payload and the ground segment from Austria, Belgium, France, Germany, Hungary, Italy, Portugal, Spain, Sweden and the United Kingdom. The development of the MAROONX spectrograph was funded by the David and Lucile Packard Foundation, the Heising-Simons Foundation, the Gemini Observatory, and the University of Chicago. This work was enabled by observations made from the Gemini North telescope, located within the Maunakea Science Reserve and adjacent to the summit of Maunakea. We are grateful for the privilege of observing the Universe from a place that is unique in both its astronomical quality and its cultural significance. CARMENES is an instrument at the Centro Astronómico Hispano en Andalucía (CAHA) at Calar Alto (Almería, Spain), operated jointly by the Junta de Andalucía and the Instituto de Astrofísica de Andalucía (CSIC). CARMENES was funded by the Max-Planck-Gesellschaft (MPG), the Consejo Superior de Investigaciones Científicas (CSIC), the Ministerio de Economía y Competitividad (MINECO) and the European Regional Development Fund (ERDF) through projects FICTS-2011-02, ICTS-2017-07-CAHA-4, and CAHA16-CE-3978, and the members of the CARMENES Consortium (Max-Planck-Institut für Astronomie, Instituto de Astrofísica de Andalucía, Landessternwarte Königstuhl, Institut de Ciències de l’Espai, Institut für Astrophysik Göttingen, Universidad Complutense de Madrid, Thüringer Landessternwarte Tautenburg, Instituto de Astrofísica de Canarias, Hamburger Sternwarte, Centro de Astrobiología and Centro Astronómico Hispano-Alemán), with additional contributions by the MINECO, the Deutsche Forschungsgemeinschaft (DFG) through the Major Research Instrumentation Programme and Research Unit FOR2544 “Blue Planets around Red Stars”, the Klaus Tschira Stiftung, the states of Baden-Württemberg and Niedersachsen, and by the Junta de Andalucía. This work is based upon observations obtained with the Georgia State University (GSU) Center for High Angular Resolution Astronomy Array at Mount Wilson Observatory. The CHARA Array is supported by the National Science Foundation under Grant No. AST-1636624 and AST-2034336. Institutional support has been provided from the GSU College of Arts and Sciences and the GSU Office of the Vice President for Research and Economic Development. We would like to recognise the observing team, scientists, and support staff at the CHARA Array. Observation time for this work was generously allocated via discretionary time from CHARA Array director Theo ten Brumelaar and via NOIRLab community access program (proposals 2021A-0247 and 2021A-0141). MIRC-X received funding from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation program (Grant No. 639889), as well as from NASA (XRP NNX16AD43G) and NSF (AST 1909165). Data were partly collected with the 90 cm telescope at the Observatorio de Sierra Nevada operated by the Instituto de Astrofífica de Andalucía (IAA-CSIC). This work made use of observations from the Las Cumbres Observatory Global Telescope network. LCOGT observations were partially acquired via program number TAU2021A-015 of the Wise Observatory, Tel-Aviv University, Israel. We acknowledge financial support from the Agencia Estatal de Investigación of the Ministerio de Ciencia, Innovación y Universidades and the ERDF through projects PID2019-109522GB-C5[1:4], PID2019-107061GBC64, PID2019-110689RB-100, PGC2018-095317-B-C21, PGC2018-102108-BI00, and the Centre of Excellence “Severo Ochoa” and “María de Maeztu” awards to the Instituto de Astrofísica de Canarias (CEX2019-000920-S), Instituto de Astrofísica de Andalucía (SEV-2017-0709), and Centro de Astrobiología (MDM2017-0737), DFG through FOR2544 (KU 3625/2-1) and Germany’s Excellence Strategy to the Excellence Cluster ORIGINS (EXC-2094 - 390783311), European Research Council (Starting Grant 639889), Bulgarian National Science Fund through VIHREN-2021 (KP-06-DB/5), Schweizerischer Nationalfonds zur Förderung der wissenschaftlichen Forschung / Fonds national suisse de la recherche scientifique (PZ00P2_174028), United Kingdom Science Technology and Facilities Council (630008203), NASA (80NSSC22K0117), National Science Foundation (2108465 and Graduate Research Fellowship DGE 1746045), Princeton University through the Henry Norris Russell Fellowship, Universidad La Laguna through the Margarita Salas Fellowship from the Spanish Ministerio de Universidades and under the EU Next Generation funds (UNI/551/2021- May 26), and the Generalitat de Catalunya (CERCA programme). We used the NASA Exoplanet Archive, which is operated by the California Institute of Technology, under contract with the National Aeronautics and Space Administration under the Exoplanet Exploration Program, and Uncertainties, a Python package for calculations with uncertainties developed by E. O. Lebigot (https://pythonhosted.org/uncertainties).