High velocity water maser emission from the Post-AGB star OH 009.1-0.4

TL;DR

This study reports the discovery of the largest velocity spread in water maser emission from the post-AGB star OH 009.1-0.4, revealing extreme kinematic activity and spatial confinement of the masers.

Contribution

First detailed high-velocity water maser observations of OH 009.1-0.4, expanding understanding of maser dynamics in post-AGB stars and water fountain sources.

Findings

Velocity spread of nearly 400 km/s, the largest known in our Galaxy.

Maser emission confined to a 0.3 arcsecond region.

Weak evidence for separation of red- and blueshifted maser spots.

Abstract

Observations of H$_2$O masers towards the post-AGB star and water fountain source OH 009.1--0.4 were made as part of HOPS (The H$_2$O southern galactic Plane Survey), with the Mopra radiotelescope. Together with followup observations using the Australia Telescope Compact Array (ATCA), we have identified H$_2$O maser emission over a velocity spread of nearly 400km/s (--109 to +289km/s). This velocity spread appears to be the largest of any known maser source in our Galaxy. High resolution observations with the ATCA indicate the maser emission is confined to a region $0\farcs3 \times 0\farcs3$ and shows weak evidence for a separation of the red- and blueshifted maser spots. We are unable to determine if the water fountain is projected along the line of sight, or is inclined, but either way OH 009.1--0.4 is an interesting source, worthy of followup observations.