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Characterizing six solar analogues observed by Kepler/K2 and Hermes Rafael A. García1, Savita Mathur2,3 , George T. Hookway4, Diego Godoy-Rivera2,3, Thomas Masseron2,3, Christopher J. Lindsay5, Travis S. Metcalfe6, Amalie Stokholm4, Paul G. Beck3,2, Guy R. Davies4, Antonio Jiménez2,3, Jaroslav Merc2,3, Martin B. Nielsen4, Eva Panetier1, Fernando Pérez Hernàndez2,3, Sylvain N. Breton7, Lina Borg1,8, Desmond H. Grossmann2,3, Bastien Liagre9,1,2,3, and Mikkel N. Lund10 Tasc0/KASC16 Workshop July 7 -11 2025 1AIM, CEA, CNRS, U. Paris-Saclay, U. Paris Diderot, Sorbonne Paris Cité, France, 2IAC, Spain, 3U. La Laguna, Spain, 4School of Physics and Astronomy, U. Birmingham, UK, 5Department of Astronomy, Yale, USA, 6Center for Solar-Stellar Connections, White Dwarf Research Corporation, USA, 7INAF – Osservatorio Astrofisico di Catania, Italy, 8INSA Lyon, France, 9ENS Paris-Saclay, U. Paris-Saclay, France, 10Stellar Astrophysics Centre, Department of Physics and Astronomy, Aarhus, Denmark The Sun is a cornerstone of stellar astrophysics, offering a uniquely detailed benchmark due to its proximity. However, our ability to observe it spans only a brief window of its 4.5-billion-year evolution, raising the question: how typical is the Sun among solar-type stars? This has led to the identification of solar twins—stars nearly identical to the Sun in parameters such as effective temperature, gravity, metallicity, age, luminosity, and magnetic activity—and solar analogues, which broadly resemble the Sun but allow for greater variation. Recent advances in asteroseismology have transformed stellar characterisation by detecting solar-like oscillations in hundreds of mainsequence stars. These oscillations allow precise measurements of stellar masses, radii, and ages. When combined with high-resolution spectroscopy, they yield the most accurate fundamental parameters to date and have led to the identification of seismic solar analogues: stars that resemble the Sun in both atmospheric properties and internal structure. This work presents a combined seismic and spectroscopic analysis of six solar analogues observed by Kepler/K2, HERMES, and Gaia. By integrating individual oscillation frequencies, high-resolution spectroscopic abundances, and precise astrometric data, we derive detailed stellar structure and evolution models. This approach enables unprecedented insight into the internal properties of these stars and helps place the Sun within a broader evolutionary framework. Abstract Acknowledgements: This paperincludes data collected by the Kepler mission and obtained from the MAST data archive at the Space Telescope Science Institute (STScI). Funding for the Kepler mission is provided by the NASA Science Mission Directorate. STScI is operated by the Association of Universities for Research in Astronomy, Inc., under NASA contract NAS 526555. R.A.G. and S.N.B. acknowledge the support from the CNES GOLF and PLATO grants. S.M. acknowledges support by the Spanish Ministry of Science and Innovation with the Ramon y Cajal fellowship number RYC-2015-17697 and the grant number PID2019107187GBI00. A.R.G.S. acknowledges the support of the STFC consolidated grant ST/T000252/1 and NASA grant No. NNX17AF27. Observations & Data Analysis Results & Discussion Fig.3: Comparison of the masses, radii, and ages of the 6 targets from the different modeling teams. Seismic Analysis Spectroscopic Analysis •Global parameters: A2Z pipeline •Detailed peak-bagging: Apollinaire + PBJam (see poster by G. T. Hookway) •Nested sample and MCMC-based fitting of individual mode profiles •Sampled mode frequencies, heights, widths, splittings, and inclination angle •Mode identification using asymptotic relations and priors from stellar models. •Final mode selection based on the proper retrieval by the 2 codes •High-resolution spectra: HERMES spectrograph (R~85,000) on Mercator •BACCHUS code: 1d LTE analysis using MARCS atmosphere models: •Teff: Derived from the excitation balance of Fe I lines. •log g: Ionization balance between Fe I and Fe II. •[Fe/H]: Averaged from Fe I lines. •Vsini: Derived from line broadening •including instrumental and macroturbulence contributions. •Cross-checks and consistency: •Comparison with SED-derived temperatures (VOSA tool). •Visual validation using Hα and Mg triplet line profiles. •5 K2 (EVEREST data) and 1 Kepler main mission (KEPSEISMIC data) stars •Four out of the six target stars are reported to be members of binary or multiple systems. Fig.1: Echelle diagram of EPIC 206245055.•Modeling by 4 different teams: • IACgrid based on MESA models •AS based on GARSTEC models •AMP v1.3 based on ASTEC models •CL based on MESA models They all used as inputs the spectroscopic parameters, the individual frequencies of the modes and the luminosity derived from Gaia DR3. References •Borucki, W. J., et al. 2010, Sci, 327, 977 •Breton, S. N., et al. 2021, A&A, 663,118 •Christensen-Dalsgaard J. 2008, Ap&SS, 316,13 •Howell, S. et al. 2014, •Lindsay, C. et al. 2024, ApJ, 965, 171 •Luger, R. et al., 2018, AJ....156...99L •Masseron, T. et al. 2016, BACCHUS ascl:1605.004 •Mathur, S. et al., 2010, A&A 511, A46 •Metcalfe, T. S. et al. 2009, ApJ, 699, 373 •Nielsen, M. B. et al. 2025, AJ, 169, 322 •Raskin, G., et al. 2011, A&A, 526, 6 •Weeks, A. et al. 2025, MNRAS, 539, 405 Fig. 2: Comparison between PBJam and apollinaire
