Discovery of four water masers in the Small Magellanic Cloud

TL;DR

This paper reports the discovery and monitoring of four water masers in the Small Magellanic Cloud, highlighting their variability, potential for proper motion measurements, and the absence of associated methanol or OH masers.

Contribution

The study presents the first detection and detailed characterization of four water masers in the SMC, including their positions, variability, and potential for VLBI-based proper motion measurements.

Findings

Four water masers detected in the SMC.

Water masers show higher variability than Galactic counterparts.

No methanol or OH masers detected in the observed regions.

Abstract

We report the detection of four water masers within the Small Magellanic Cloud (SMC); two discovered with the 70-m Tidbinbilla radio telescope, and two discovered with the Australia Telescope Compact Array (ATCA). Precise positions of all four masers have been derived from ATCA observations, and the characteristics of each water maser have been monitored over a period of several years. Sensitive observations towards two previously detected water masers reported in the literature failed to detect any emission. The detected water masers show evidence of higher levels of temporal variability than equivalent Galactic sources, and one of the features associated with NGC346 IR1 shows an acceleration of 9.6 km/s yr^-1 over a 31 day period. Sensitive targeted observations for methanol and OH masers failed to detect any accompanying emission - in the case of methanol perhaps highlighting an under abundance in the SMC, consistent with expectations due to lower metallicity. The water masers are both bright and compact making them excellent targets for Very Long Baseline Interferometry (VLBI) observations, which can potentially measure the proper motion of the SMC (~1 - 2 mas yr^-1) with temporal baselines of ~12 months. Such observations would utilise sources associated with only the current epoch of star formation and hence have several advantages over alternative methods.