H2O masers in a jet-driven bowshock: Episodic ejection from a massive young stellar object

TL;DR

This study uses VLBI water maser observations to measure the distance and motion of a massive young stellar object, revealing episodic jet-driven outflows with bowshock morphology occurring approximately every 1000 years.

Contribution

First detailed VLBI water maser study of S255IR-SMA1, providing precise distance, motion, and evidence of episodic jet-driven outflows in a massive young stellar object.

Findings

Distance to S255IR-SMA1 is 1.78 kpc.

Masers trace a bow shock consistent with jet-driven outflow.

Episodic ejections occur roughly every 1000 years.

Abstract

We report the results of VERA multi-epoch VLBI 22 GHz water maser observations of S255IR-SMA1, a massive young stellar object located in the S255 star forming region. By annual parallax the source distance was measured as D = 1.78 +-0.12 kpc and the source systemic motion was (u alpha cos d, u d) = (-0.13 +- 0.20, -0.06 +- 0.27) mas yr-1. Masers appear to trace a U-shaped bow shock whose morphology and proper motions are well reproduced by a jet-driven outflow model with a jet radius of about 6 AU. The maser data, in the context of other works in the literature, reveal ejections from S255IR-SMA1 to be episodic, operating on timescales of ~1000 years.