Discovery of periodic class II methanol masers associated with G339.986-0.425 region

TL;DR

This study reports the discovery of periodic variability in class II methanol masers associated with G339.986-0.425, with a period of approximately 246 days, using multi-year radio observations and multiple analysis methods.

Contribution

It is the first to identify and characterize periodic variability in these specific masers, providing detailed timing and correlation analysis.

Findings

Periodic variability with a 246-day cycle was confirmed.

Strong correlations across velocity channels and frequencies were observed.

Time delays across channels reveal structured spectral behavior.

Abstract

Ten new class II methanol masers from the 6.7-GHz Methanol Multibeam survey catalogues III and IV were selected for a monitoring programme at both 6.7 and 12.2 GHz with the 26m Hartebeesthoek Radio Astronomy Observatory (HartRAO) radio telescope for two years and nine months, from August 2012 to May 2015. In the sample, only masers associated with G339.986-0.425 were found to show periodic variability at both 6.7 and 12.2 GHz. The existence of periodic variation was tested with four independent methods. The analytical method gave the best estimation of the period, which was 246 $\pm$ 1 days. The time series of G339.986-0.425 show strong correlations across velocity channels and between the 6.7 and 12.2 GHz masers. The time delay was also measured across channels and shows structure across the spectrum which is continuous between different maser components.