6.7GHz methanol maser variability in Cepheus A

Abstract

6.7 GHz methanol maser emission from the well-studied star-forming region Cepheus A was monitored with the Torun 32 m radio telescope. We found synchronized and anticorrelated changes of the flux density of the two blueshifted and one redshifted maser features for ~30 per cent of 1340 d of our observations. Two of those features exhibited high amplitude flux density variations with periods of 84-87 d over the last 290 d interval of the monitoring. We also report on two flares of emission at two different redshifted velocities completely covered during the whole outburst. These flare events lasted 510-670 d and showed a very rapid linear rise and slow exponential decline, which may be caused by variability of the seed flux density. The flux density of the two strongest features dropped by a factor of 2-5 on a time-scale ~22 yr, while other features have not changed significantly during this period, but showed strong variability on time-scales <5 yr.

9 pages, 11 figures

References in corpus (3)

• A new probe of magnetic fields during high-mass star formation: Zeeman splitting of 6.7 GHz methanol masers
• A Photoevaporating Rotating Disk in the Cepheus A HW2 Star Cluster
• A GLIMPSE-based search for 6.7-GHz Methanol Masers and the lifetime of their spectral features

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• 6.7 GHz variability characteristics of new periodic methanol maser sources
• Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639
• New evidence for Dicke's superradiance in the 6.7 GHz methanol spectral line in the interstellar medium
• Detection of the longest periodic variability in 6.7 GHz methanol masers G5.900-0.430
• Milliarcsecond structure and variability of methanol maser emission in three high-mass protostars
• Massive Protocluster of a Periodic Maser Source G188.95+0.89
• Discovery of recurrent flares of 6.7 GHz methanol maser emission in Cepheus A HW2