Ariel stellar characterisation

III. Fast rotators and new FGK stars in the Ariel mission candidate sample

¹ INAF – Osservatorio Astrofisico di Arcetri, Largo E. Fermi 5, 50125 Firenze, Italy
² Department of Physics and Astronomy G. Galilei, University of Padova, Vicolo dell’Osservatorio 3, 35122 Padova, Italy
³ INAF – Osservatorio Astronomico di Padova, Vicolo dell’Osservatorio 5, 35122, Padova, Italy
⁴ INAF – Osservatorio Astrofisico di Torino, via Osservatorio 20, 10025 Pino Torinese, Italy
⁵ INAF – IAPS, Via Fosso del Cavaliere 100, 00133 Rome, Italy
⁶ Tartu Observatory, University of Tartu, Observatooriumi 1, Tõravere, 61602 Tartumaa, Estonia
⁷ INAF – Osservatorio Astronomico di Roma, Via Frascati 33, 00040 Monte Porzio Catone (RM), Italy
⁸ Instituto de Astrofísica e Ciências do Espaço, Universidade do Porto, CAUP, Rua das Estrelas, 4150-762 Porto, Portugal
⁹ Departamento de Física e Astronomia, Faculdade de Ciências da Universidade do Porto, Rua do Campo Alegre, s/n, 4169-007 Porto, Portugal
¹⁰ Centro de Astrobiología (CAB), CSIC-INTA, Camino Bajo del Castillo s/n, 28692 Villanueva de la Cañada (Madrid), Spain
¹¹ Agenzia Spaziale Italiana, Space Science Data Center, via del Politecnico snc, 00133 Rome, Italy
¹² INAF – Osservatorio Astronomico di Palermo, Piazza del Parlamento, 1, 90134 Palermo, Italy
¹³ Research School of Astronomy & Astrophysics, Australian National University, Cotter Rd., Weston, ACT 2611, Australia
¹⁴ ARC Centre of Excellence for All Sky Astrophysics in 3 Dimensions (ASTRO 3D), Stromlo, Australia
¹⁵ INAF – Osservatorio di Astrofisica e Scienza dello Spazio di Bologna, via P. Gobetti 93/3, 40129 Bologna, Italy
¹⁶ Nicolaus Copernicus Astronomical Center, Polish Academy of Sciences, ul. Rabiańska 8, 87-100 Toruń, Poland
¹⁷ INAF – Osservatorio Astronomico di Brera, Via E. Bianchi 46, 23807 Merate (LC), Italy

^★ Corresponding author; maria.tsantaki@inaf.it

Received: 18 November 2024
Accepted: 8 March 2025

Abstract

Context. The next mission dedicated to the study of planetary atmospheres is the Ariel space mission, planned for launch in 2029, which will observe a variety of planetary systems belonging to different classes around stars with spectral types from M to A. To optimise the scientific outcome of the mission, such stars need to be homogeneously characterised beforehand.

Aims. In this work, we focus on a methodology based on spectral synthesis for the characterisation of FGK-type stars from the Ariel Tier 1 mission candidate sample (MCS) that exhibit fast rotation. In addition, we analyse 108 slow-rotating FGK-type stars, with either new observations or archival spectra available, consistently as in our previous work using the equivalent width (EW) analysis.

Methods. To ensure consistency between our methods, we re-analysed a sample of FGK-type stars with the spectral synthesis method and compared it to our previous work. The results of our analysis show excellent agreement with the previous set of derived parameters.

Results. We provide homogeneous effective temperature, surface gravity, metallicity, projected rotational velocity, and stellar mass for a sample of 36 fast rotators with the spectral synthesis technique, and we include 108 FGK-type dwarfs with the EW analysis. An additional 25 stars were analysed with the spectral synthesis method because their EW analysis did not converge on the final parameters. We computed their orbital parameters establishing whether they belong to the Galactic thin or thick discs. With the current set of stellar parameters, we almost double the analysed hosts in the Ariel MCS to 353 stars in total.

Conclusions. Using our homogeneous set of stellar parameters, we studied the correlations between stellar and planetary properties for the Ariel MCS analysed so far. We confirmed a close relationship between stellar mass (up to 1.8 M_⊙) and giant planet radius, with more inflated planets at lower metallicity. We confirm that giant planets are more frequent around more metal-rich stars that belong to the thin disc, while lower-mass planets are also found in more metal-poor environments, and are more frequent than giant planets in the thick disc as also seen in other works in the literature.