Insights from the stability of methanol maser flare properties. I. G9.62+0.20E
Year: 2026
Type: article
Abstract: The brightest 6.7 GHz methanol maser in the Galaxy is associated with the high-mass star-forming region (HMSFR) G009.62+0.20E. Additionally, this methanol maser shows periodic flaring observed at 6.7 and 12.2 gigahertz (GHz). Several models have been hypothesised to explain the periodicity, including periodic accretion, spiral shocks in the gaps of circumbinary disks, pulsating stars, Dicke's superradiance, and a colliding-wind-binary (CWB) system. We aim to analyse the time series of the 1.22 km s -1 $ feature of the 6.7 GHz methanol maser spectrum and the 1.25 km s$^ -1 feature of the 12.2 GHz methanol maser spectrum over the monitoring duration of roughly 20 years; we in turn intend to determine an updated period and analyse the stability and repeatability of the flares, the temporal behaviour of the flare profile, and the duty cycle of the flare profile based on the updated period. Based on these results, we argue for or against any of the mechanisms that have been proposed to explain the periodicity. Lomb--Scargle (LS) and phase-dispersion-minimalisation (PDM) methods were used to determine the methanol maser period at 6.7 and 12.2 GHz. Once the period had been determined, phase-folding or period-folding was used to analyse the flare shape, flare stability, and duty cycle of the flares. The periods of the 6.7 and 12.2 GHz methanol masers were determined to be ∼ 243.0 ± 0.3 days. The flares are highly repeatable and stable, and they show almost identical shapes, as do their duty cycles. A replicated kernel density estimator (KDE) of the flare shape reproduces the time series very well over a time span of ∼ 8000 days. After careful consideration of the proposed mechanisms for periodic methanol masers, we conclude that all but one (the CWB model) can be ruled out as a possible driver of this flare profile. It has also been established that the CWB model can qualitatively explain the flare profile of the periodic methanol masers.
Source: Astronomy and Astrophysics
Authors: S.P. van den Heever, D.J. van der Walt
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: gold
Estimated APC paid: $1,865
OpenAlex ID: W7223093555