Very Long Baseline Array astrometry of low-mass young stellar objects

TL;DR

This paper demonstrates that Very Long Baseline Array astrometry can measure distances and motions of young stellar objects with unprecedented precision, significantly improving our understanding of nearby star-forming regions.

Contribution

It introduces a high-precision astrometric method using VLBA for young stars, enabling accurate distance and motion measurements within star-forming regions.

Findings

Achieved better than 50 micro-arcsecond accuracy in astrometry.

Measured distances to stars in Taurus and Ophiuchus with over tenfold improvement.

Provided new insights into the orbital dynamics of the T Tauri system.

Abstract

Multi-epoch radio-interferometric observations of young stellar objects can be used to measure their displacement over the celestial sphere with a level of precision that currently cannot be attained at any other wavelength. In particular, the accuracy achieved using carefully calibrated, phase-referenced observations with the Very Long Baseline Array is better than 50 micro-arcseconds. This is sufficient to measure the trigonometric parallax and the proper motion of any radio-emitting young star within several hundred parsecs of the Sun with an accuracy better than a few percents. Taking advantage of this situation, we have initiated a large project aimed mainly at measuring the distance to the nearest regions of star-formation (Taurus, Ophiuchus, Perseus, etc.). Here, we will present the results for several stars in Taurus and Ophiuchus, and show that the accuracy obtained is already more than one order of magnitude better than that of previous estimates. The proper motion obtained from the data can also provide important information, particularly in multiple stellar systems. To illustrate this point, we will present the case of the famous system T Tauri, where the VLBA data provide crucial information for the characterization of the orbital path.