Short-period variability in the Class II methanol maser source G12.89+0.49 (IRAS 18089-1732)

TL;DR

This study presents a nine-year time series of class II methanol masers in G12.89+0.49, revealing a stable 29.5-day periodic variability with correlated spectral features and measurable time delays, enhancing understanding of maser dynamics.

Contribution

It provides the first long-term, detailed analysis of periodic variability in methanol masers, identifying stable periodicity and spectral time delays in G12.89+0.49.

Findings

Periodic variability with a 29.5-day cycle was observed.

Spectral features show time delays up to 5.7 days.

Variability is stable over at least 110 cycles.

Abstract

Time series are presented for the class II methanol maser source G12.89+0.49, which has been monitored for nine years at the Hartebeesthoek Radio Astronomy Observatory. The 12.2 and 6.7 GHz methanol masers were seen to exhibit rapid, correlated variations on timescales of less than a month. Daily monitoring has revealed that the variations have a periodic component with a period of 29.5 days. The period seems to be stable over the 110 cycles spanned by the time series. There are variations from cycle to cycle, with the peak of the flare occurring anywhere within an eleven day window but the minima occur at the same phase of the cycle. Time delays of up to 5.7 days are seen between spectral features at 6.7 GHz and a delay of 1.1 day is seen between the dominant 12.2 GHz spectral feature and its 6.7 GHz counterpart.