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Planetary system around LTT 1445A unveiled by ESPRESSO: Multiple planets in a triple M-dwarf system

Journal
Date Issued
2023
Author(s)
Lavie, B.
•
Bouchy, F.
•
Lovis, C.
•
Zapatero Osorio, M.
•
Deline, A.
•
Barros, S.
•
Figueira, P.
•
•
González Hernández, J. I.
•
Lillo-Box, J.
•
Rodrigues, J.
•
Mehner, A.
•
•
Adibekyan, V.
•
Alibert, Y.
•
Allende Prieto, C.
•
•
•
•
Ehrenreich, D.
•
Génova Santos, R.
•
Lo Curto, G.
•
Martins, C. J. A. P.
•
•
•
Nunes, N.
•
Palle, E.
•
Pepe, F.
•
•
Rebolo, R.
•
Santos, N.
•
Sousa, S.
•
Suárez Mascareño, A.
•
Tabrenero, H.
•
Udry, S.
DOI
Abstract
We present radial velocity follow-up obtained with ESPRESSO of the M-type star LTT 1445A (TOI-455), for which a transiting planet b with an orbital period of 5.4 days was detected by TESS. We report the discovery of a second transiting planet (LTT 1445A c) and a third non-transiting candidate planet (LTT 1445A d) with orbital periods of 3.12 and 24.30 days, respectively. The host star is the main component of a triple M-dwarf system at a distance of 6.9 pc. We used 84 ESPRESSO high-resolution spectra to determine accurate masses of 2.3 ± 0.3 M⊕ and 1.0 ± 0.2 M⊕ for planets b and c and a minimum mass of 2.7 ± 0.7 M⊕ for planet d. Based on its radius of 1.43 ± 0.09 R⊕ as derived from the TESS observations, LTT 1445A b has a lower density than the Earth and may therefore hold a sizeable atmosphere, which makes it a prime target for the James Webb Space Telescope (JWST). We used a Bayesian inference approach with the nested sampling algorithm and a set of models to test the robustness of the retrieved physical values of the system. There is a probability of 85% that the transit of planet c is grazing, which results in a retrieved radius with large uncertainties at 1.60−0.34+0.67 R⊕. LTT 1445A d orbits the inner boundary of the habitable zone of its host star and could be a prime target for the JWST.

RV and activity indices for ESPRESSO are only available at the CDS via anonymous ftp to cdsarc.cds.unistra.fr (ftp://130.79.128.5) or via https://cdsarc.cds.unistra.fr/viz-bin/cat/J/A+A/673/A69

Volume
673
Start page
A69
Uri
Url
Issn Identifier
0004-6361
Ads BibCode
2023A&A...673A..69L
Rights
open.access
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