Variability monitoring of the hydroxyl maser emission in G12.889+0.489

TL;DR

This study monitored hydroxyl maser emission variability in G12.889+0.489 over 16 months, revealing ~20% flux variation, weak periodicity, and stable polarization, providing the first such observational data for this source.

Contribution

First long-term monitoring of hydroxyl maser emission in G12.889+0.489, showing variability and potential periodicity linked to methanol maser activity.

Findings

Hydroxyl maser flux varies by ~20% over time.

No significant flaring activity observed.

Weak indication of periodic variability similar to methanol masers.

Abstract

Through a series of observations with the Australia Telescope Compact Array we have monitored the variability of ground-state hydroxyl maser emission from G12.889+0.489 in all four Stokes polarisation products. These observations were motivated by the known periodicity in the associated 6.7-GHz methanol maser emission. A total of 27 epochs of observations were made over 16 months. No emission was seen from either the 1612 or 1720 MHz satellite line transitions (to a typical five sigma upper limit of 0.2 Jy). The peak flux densities of the 1665 and 1667 MHz emission were observed to vary at a level of ~20% (with the exception of one epoch which dropped by <40%). There was no distinct flaring activity at any epoch, but there was a weak indication of periodic variability, with a period and phase of minimum emission similar to that of methanol. There is no significant variation in the polarised properties of the hydroxyl, with Stokes Q and U flux densities varying in accord with the Stokes I intensity (linear polarisation, P, varying by <20%) and the right and left circularly polarised components varying by <33% at 1665-MHz and <38% at 1667-MHz. These observations are the first monitoring observations of the hydroxyl maser emission from G12.889+0.489.