Dynamical Masses for 23 Pre-main-sequence Stars in Upper Scorpius: A Critical Test of Stellar Evolutionary Models

We present dynamical masses for 23 pre-main-sequence (PMS) K- and M-type stars in the Upper Scorpius star-forming region. These masses were derived from the Keplerian rotation of CO disk gas using the Markov Chain Monte Carlo radiative-transfer package pdspy and a flared-disk model with 15 free parameters. We compare our dynamical masses to those derived from five PMS evolutionary models, and find that most models consistently underestimate stellar mass by ≳25%. Models with updated treatment of stellar magnetic fields are a notable exception—they consistently return stellar masses in good agreement with the dynamical results. We find that the magnetic models’ performance is valid even at low masses, in contrast with some literature results suggesting they may overestimate stellar mass for M_⋆ ≲ 0.6 M_⊙. Our results are consistent with dynamical versus isochronal evaluations for younger samples (e.g., Taurus, 1–3 Myr), and extend the systematic evaluation of stellar evolutionary models up to stars ∼11 Myr in age. Finally, we derive disk dust masses to evaluate whether using dynamical masses versus isochronal masses changes the slope of the log(M_dust)−log(M_⋆) relation. We derive a slightly shallower relation using dynamical masses versus isochronal masses, but the slopes of these relations agree within uncertainties. In all cases, we derive a steeper than linear relation for log(M_dust)−log(M_⋆), consistent with previous literature results for Upper Sco.