A detailed analysis of the Gl 486 planetary system

Publication date: 
Main author: 
Caballero, J. A.
IAA authors: 
Rodríguez, E.;Amado, P. J.;López González, M. J.;Luque, R.;Rodríguez-López, C.;Shulyak, D.
Caballero, J. A.;González-Álvarez, E.;Brady, M.;Trifonov, T.;Ellis, T. G.;Dorn, C.;Cifuentes, C.;Molaverdikhani, K.;Bean, J. L.;Boyajian, T.;Rodríguez, E.;Sanz-Forcada, J.;Zapatero Osorio, M. R.;Abia, C.;Amado, P. J.;Anugu, N.;Béjar, V. J. S.;Davies, C. L.;Dreizler, S.;Dubois, F.;Ennis, J.;Espinoza, N.;Farrington, C. D.;López, A. García;Gardner, T.;Hatzes, A. P.;Henning, Th.;Herrero, E.;Herrero-Cisneros, E.;Kaminski, A.;Kasper, D.;Klement, R.;Kraus, S.;Labdon, A.;Lanthermann, C.;Le Bouquin, J. -B.;López González, M. J.;Luque, R.;Mann, A. W.;Marfil, E.;Monnier, J. D.;Montes, D.;Morales, J. C.;Pallé, E.;Pedraz, S.;Quirrenbach, A.;Reffert, S.;Reiners, A.;Ribas, I.;Rodríguez-López, C.;Schaefer, G.;Schweitzer, A.;Seifahrt, A.;Setterholm, B. R.;Shan, Y.;Shulyak, D.;Solano, E.;Sreenivas, K. R.;Stefánsson, G.;Stürmer, J.;Tabernero, H. M.;Tal-Or, L.;ten Brummelaar, T.;Vanaverbeke, S.;von Braun, K.;Youngblood, A.;Zechmeister, M.
Astronomy and Astrophysics
Publication type: 
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<SUB>⊕</SUB> and 3.0 M<SUB>⊕</SUB>. It is ideal for both transmission and emission spectroscopy and for testing interior models of telluric planets. <BR /> 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. <BR /> 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. <BR /> Results: From interferometry, we measure a limb-darkened disc angular size of the star Gl 486 at θ<SUB>LDD</SUB> = 0.390 ± 0.018 mas. Together with a corrected Gaia EDR3 parallax, we obtain a stellar radius R<SUB>*</SUB> = 0.339 ± 0.015 R<SUB>⊕</SUB>. We also measure a stellar rotation period at P<SUB>rot</SUB> = 49.9 ± 5.5 days, an upper limit to its XUV (5-920 A) 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<SUB>p</SUB> = 1.343<SUB>−0.062</SUB><SUP>+0.063</SUP> R<SUB>⊕</SUB> and M<SUB>p</SUB> = 3.00<SUB>−0.12</SUB><SUP>+0.13</SUP> M<SUB>⊕</SUB>, 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.
ADS Bibcode: 
planetary systems;techniques: photometric;techniques: radial velocities;stars: individual: Gl 486;stars: late-type;Astrophysics - Earth and Planetary Astrophysics;Astrophysics - Solar and Stellar Astrophysics