# High Precision Dynamical Masses of Pre-Main Sequence Stars with ALMA and Gaia

## TL;DR

This paper demonstrates how combining ALMA and Gaia data allows for highly precise dynamical mass measurements of pre-main sequence stars, providing critical tests for stellar evolutionary models.

## Contribution

It introduces a method using ALMA and Gaia data to measure stellar masses with ~2% precision, and compares these with model predictions for young stars.

## Key findings

- Masses of three young stars measured with ~2% accuracy.
- Broad consistency found between dynamical and evolutionary model masses.
- Potential discrepancies suggest areas for refinement in models.

## Abstract

The Keplerian rotation in protoplanetary disks can be used to robustly measure stellar masses at very high precision if the source distance is known. We present Atacama Large Millimeter/submillimeter Array (ALMA) observations of spatially and spectrally resolved $^{12}$CO (2--1) emission towards the disks around 2MASS J16262774--2527247 (the tertiary companion to ROXs 12 at 5100 au), CT Cha, and DH Tau. We employ detailed modeling of the Keplerian rotation profile, coupled with accurate distances from $Gaia$, to directly measure the stellar masses with $\sim$2\% precision. We also compare these direct mass measurements with the masses inferred from evolutionary models, determined in a statistically rigorous way. We find that 2MASS J16262774--2527247 has a mass of $0.535^{+0.006}_{-0.007}~M_{\odot}$ and CT Cha has a mass of $0.796^{+0.015}_{-0.014}~M_{\odot}$, broadly consistent with evolutionary models, although potentially significant differences remain. DH Tau has a mass of $0.101^{+0.004}_{-0.003}~M_{\odot}$, but it suffers from strong foreground absorption that may affect our mass estimate. The combination of ALMA, $Gaia$, and codes like \texttt{pdspy}, presented here, can be used to infer the dynamical masses for large samples of young stars and substellar objects, and place constraints on evolutionary models.