Letter to the Editor

Benchmarking pre-main sequence stellar evolutionary tracks using disk-based dynamical stellar masses

¹ Dipartimento di Fisica ‘Aldo Pontremoli’, Università degli Studi di Milano, via G. Celoria 16, I-20133, Milano, Italy
² European Southern Observatory, Karl-Schwarzschild-Strasse 2, D-85748, Garching bei München, Germany
³ Center for Astrophysics | Harvard & Smithsonian, 60 Garden Street, Cambridge, MA 02138, USA
⁴ University College Dublin (UCD), Department of Physics, Belfield, Dublin 4, Ireland
⁵ Joint ALMA Observatory, Avenida Alonso de Córdova 3107, Vitacura, Santiago, Chile
⁶ Lunar and Planetary Laboratory, the University of Arizona, Tucson, AZ 85721, USA
⁷ Max Planck Institute for Extraterrestrial Physics, Giessenbachstrasse 1, D-85748, Garching, Germany
⁸ Max-Planck-Institut fur Astronomie (MPIA), Konigstuhl 17, 69117, Heidelberg, Germany
⁹ Department of Astronomy, University of Virginia, Charlottesville, VA 22904, USA
¹⁰ Institute of Astronomy, University of Cambridge, Madingley Road, Cambridge CB3 0HA, UK
¹¹ Department of Astronomy, University of Michigan, 1085 South University Avenue, Ann Arbor, MI 48109, USA
¹² Department of Earth, Atmospheric, and Planetary Sciences, Massachusetts Institute of Technology, Cambridge, MA 02139, USA
¹³ Univ. Grenoble Alpes, CNRS, IPAG, F-38000, Grenoble, France
¹⁴ Academia Sinica Institute of Astronomy and Astrophysics, 11F of Astronomy-Mathematics Building, AS/NTU, No.1, Sec 4, Roosevelt Rd, Taipei 106216, Taiwan

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Received: 17 November 2025
Accepted: 3 March 2026

Abstract

Stellar masses are a fundamental property to understand models of pre-main sequence evolution, but their values derived from Hertzsprung–Russell (HR) diagrams are strongly model dependent. We benchmark pre-main sequence stellar evolutionary tracks using stellar masses dynamically estimated by fitting a parametric model to ALMA observations of the ¹²CO (J = 3 − 2) line transition emitted by the disks orbiting 20 sources in the old (4 − 14 Myr) Upper Scorpius star forming region. We derive stellar masses from HR diagram fitting for ten different stellar evolutionary models, which we then compare with their stellar dynamical masses for comparison in the stellar mass range 0.1 − 1.3 M_⊙. Models with a moderate-to-low fraction of cold stellar spots (f = 17%) most accurately reproduce the dynamical stellar masses (100% of the targets agree within ±1σ). While a higher spot coverage (f = 34%) provides similar stellar mass predictions similar to magnetic equipartition models, larger fractions (f ≥ 51%) significantly disagree with dynamical masses. Magnetic equipartition models overestimate stellar masses up to a factor ∼20%, whereas non-magnetic models underestimate them up to ∼12%. For some models, there is evidence that the stellar mass discrepancies are anticorrelated with dynamical stellar masses. When stellar dynamical mass priors are considered in HR diagram fitting, the median age of a single source can change up to ∼25%, while the median ages inferred across different tracks become consistent, with the age scatter decreasing by ≳77%. These results provide strong empirical constraints for testing and developing evolutionary models of pre-main sequence stars.