A Measurement of Proper Motions of SiO Maser Sources in the Galactic Center with the VLBA

TL;DR

This study uses VLBA to measure proper motions of SiO maser sources near the Galactic Center, revealing precise stellar motions and potential binary nature of IRS 10EE, enhancing understanding of Galactic Center dynamics.

Contribution

First high-precision VLBA astrometric measurements of SiO masers near the Galactic Center, providing detailed proper motions and insights into stellar motions relative to Sgr A*.

Findings

IRS 10EE has a proper motion of 76+-3 km/s southward.

The infrared reference frame moves westward by about 30+-9 km/s relative to Sgr A*.

IRS 10EE is likely an astrometric binary with an unseen companion.

Abstract

We report on the high-precision astrometric observations of maser sources around the Galactic Center in the SiO J=1--0 v=1 and 2 lines with the VLBA during 2001 -- 2004. With phase-referencing interferometry referred to the radio continuum source Sgr A*, accurate positions of masers were obtained for three detected objects: IRS 10 EE (7 epochs), IRS 15NE (2 epochs), and SiO 6 (only 1 epoch). Because circumstellar masers of these objects were resolved into several components, proper motions for the maser sources were derived with several different methods. Combining our VLBA results with those of the previous VLA observations, we obtained the IRS 10EE proper motion of 76+-3 km s^{-1} (at 8 kpc) to the south relative to Sgr A*. Almost null proper motion of this star in the east--west direction results in a net transverse motion of the infrared reference frame of about 30+-9 km s^{-1} to the west relative to Sgr A*. The proper-motion data also suggests that IRS 10EE is an astrometric binary with an unseen massive companion.