Solar twins in Gaia DR3 GSP-Spec

I. Building a large catalog of solar twins with ages

¹ Department of Physics, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan
² National Astronomical Observatory of Japan, 2-21-1 Osawa, Mitaka, Tokyo 181-8588, Japan
³ Université Côte d’Azur, Observatoire de la Côte d’Azur, CNRS, Laboratoire Lagrange, Bd de l’Observatoire, CS 34229, 06304 Nice cedex 4, France

^★★ Corresponding author: This email address is being protected from spambots. You need JavaScript enabled to view it.

Received: 10 January 2026
Accepted: 28 January 2026

Abstract

Context. Solar twins, stars whose stellar parameters (effective temperature, T_eff; surface gravity, log g; and metallicity, [M/H]) are very close to those of the Sun, offer a unique opportunity to investigate Galactic archaeology with very high accuracy and precision. However, most previous catalogs of solar twins contain only a small number of objects (typically a few dozen), and their selection functions are poorly characterized.

Aims. Our aim is to build a large catalog of solar twins from Gaia DR3 GSP-Spec data, providing stellar parameters and ages determined using a model-driven (rather than a data-driven) method, together with a well-characterized selection function.

Methods. Using stellar parameters from the Gaia DR3 GSP-Spec catalog, we selected solar twin candidates whose parameters lie within ±200 K in T_eff, ±0.2 in log g, and ±0.1 dex in [M/H] of the solar values. Candidates unlikely to be genuine solar twins were removed using Gaia flags and photometric constraints. We determined accurate ages for individual twins with a Bayesian isochroneprojection method by considering three combinations of parameters: T_eff and [M/H] combined with either log g, M_G, or M_Ks. We also constructed a mock catalog to characterize the properties and selection function of our observed sample.

Results. Our final GSP-Spec solar twin catalog contains 6594 stars. The mock catalog consisting of 75 588 artificial twins reproduces the main characteristics of the observed catalog well, especially for ages determined with M_G or M_Ks. To demonstrate the usefulness of our catalog, we compared chemical abundances [X/Fe] with age. We statistically confirmed the age-[X/Fe] relations for several species (e.g., Al, Si, Ca, and Y), demonstrating that trends previously identified in small but very high precision samples persist in a much larger, independent sample.

Conclusions. Our study bridges small high-precision solar twin samples and large data-driven ones by providing a large sample with model-driven stellar parameters and a quantified selection function, enabling demographic studies of solar twins.