Constraining the Stellar Masses and Origin of the Protostellar VLA 1623 System

TL;DR

This study uses ALMA observations and radiative transfer modeling to precisely measure the stellar masses of the VLA 1623 protostellar system, revealing their likely formation through turbulent fragmentation.

Contribution

First mass measurements of all VLA 1623 components using consistent tracers and methods, constraining their origins and dynamics.

Findings

VLA 1623B and W show Keplerian rotation signatures.

Masses are 0.27, 1.9, and 0.64 solar masses for the system components.

VLA 1623W is likely a true companion, not ejected or unrelated.

Abstract

We present ALMA Band 7 molecular line observations of the protostars within the VLA 1623 system. We map C$^{17}$O (3 - 2) in the circumbinary disk around VLA 1623A and the outflow cavity walls of the collimated outflow. We further detect red-shifted and blue-shifted velocity gradients in the circumstellar disks around VLA 1623B and VLA 1623W that are consistent with Keplerian rotation. We use the radiative transfer modeling code, pdspy, and simple flared disk models to measure stellar masses of $0.27 \pm 0.03$ M$_\odot$, $1.9^{+0.3}_{-0.2}$ M$_\odot$, and $0.64 \pm 0.06$ M$_\odot$ for the VLA 1623A binary, VLA 1623B, and VLA 1623W, respectively. These results represent the strongest constraints on stellar mass for both VLA 1623B and VLA 1623W, and the first measurement of mass for all stellar components using the same tracer and methodology. We use these masses to discuss the relationship between the young stellar objects (YSOs) in the VLA 1623 system. We find that VLA 1623W is unlikely to be an ejected YSO, as has been previously proposed. While we cannot rule out that VLA 1623W is a unrelated YSO, we propose that it is a true companion star to the VLA 1623A/B system and that the these stars formed in situ through turbulent fragmentation and have had only some dynamical interactions since their inception.