Discovery of four periodic methanol masers and updated light curve for a further one

Abstract

We report the discovery of 6.7 GHz methanol maser periodic flares in four massive star forming regions and the updated light curve for the known periodic source G22.357+0.066. The observations were carried out with the Torun 32 m radio telescope between June 2009 and April 2014. Flux density variations with period of 120 to 245 d were detected for some or all spectral features. A variability pattern with a fast rise and relatively slow fall on time-scale of 30-60 d dominated. A reverse pattern was observed for some features of G22.357+0.066, while sinusoidal-like variations were detected in G25.411+0.105. A weak burst lasting ~520 d with the velocity drift of 0.24 km/s/yr occurred in G22.357+0.066. For three sources for which high resolution maps are available, we found that the features with periodic behaviour are separated by more than 500 au from those without any periodicity. This suggests that the maser flares are not triggered by large-scale homogeneous variations in either the background seed photon flux or the luminosity of the exciting source and a mechanism which is able to produce local changes in the pumping conditions is required.

12 pages, 15 figures. Accepted in MNRAS

References in corpus (5)

• Trigonometric Parallaxes of Massive Star Forming Regions: VI. Galactic Structure, Fundamental Parameters and Non-Circular Motions
• The UKIDSS Galactic Plane Survey
• The Arecibo Methanol Maser Galactic Plane Survey--I: Data
• On the Class II Methanol Maser Periodic Variability due to the Rotating Spiral Shocks in the Gaps of Disks Around Young Binary Stars
• Periodic Flare of the 6.7 GHz Methanol Maser in IRAS22198+6336

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• Long-term multi-frequency maser observations of the intermediate-mass young stellar object G107.298+5.639
• Detection of periodic flares in 6.7 GHz methanol masers G45.804-0.356 and G49.043-1.079
• Periodic variability of the mainline hydroxyl masers in G9.62+0.20E
• Orientation effect on the ligh curve shape of periodic methanol maser sources
• Detection of the longest periodic variability in 6.7 GHz methanol masers G5.900-0.430
• Maser Flares Driven by Variations in Pumping and Background Radiation
• Massive Protocluster of a Periodic Maser Source G188.95+0.89
• On the pumping of the CS($v=0$) masers in W51 e2e