Abstract The stellar initial mass function (IMF) is among the most fundamental distributions in astrophysics, defined as the mass spectrum of stars produced in a single star-formation event. Even in the solar neighbourhood, where measurements can be conducted via star counting, disentangling the IMF from observational effects remains challenging. In this work we introduce a new parametrisation of the stellar IMF in the 100-pc solar neighbourhood, leveraging the high-precision astrometric and photometric data from Gaia DR3: we model the colour-magnitude diagram of the field star population while accounting for observational uncertainties, Malmquist bias, Lutz-Kelker bias, variations in the mass-luminosity relation arising from metallicity differences, and the effects of unresolved binaries. In particular, we synthesise the binary population with a process imitating the dynamical evolution observed in star clusters to enforce that all components are drawn from the same IMF, while simultaneously recovering the observed present-day mass-ratio distribution. We determine an averaged stellar IMF over 0. 25 m 1. 0 M⊙ that aligns with canonical IMFs but achieves significantly tighter constraints: ₁=0. 75^+0. 06-₀. ₀₄, ₂=2. 07^+0. 04-₀. ₀₃, and a break point at m₁ₑ₄₀₊=0. 40^+0. 01-₀. ₀₁ M. Our inference also yields an averaged binary fraction over 0. 25 m 1. 0 M⊙ of approximately 26%, and constrains the Gaia DR3 angular resolution to 1. 11^+0. 11-₀. ₀₈ arcsec. We also provide the ξ-parameter for our IMF, which is 0. 5070-₀. ₀₀₉₆^+0. 0068, to facilitate direct comparison with other IMF determinations.
Wang et al. (2026) studied this question.