6.7 GHz variability characteristics of new periodic methanol maser sources. Issue 1 (1st April 2019)

• Record Type: Journal Article
• Authors: Olech, M; Szymczak, M; Wolak, P; Sarniak, R; Bartkiewicz, A
• Is Part Of: Monthly notices of the Royal Astronomical Society. Volume 486:Issue 1(2019)
• Page Start: 1236
• Page End: 1254
• Publication Date: 2019-04-01
• Subjects: masers -- stars: formation -- ISM: clouds -- radio lines:ISM; Astronomy -- Periodicals; Periodicals; 520.5
• DOI: 10.1093/mnras/stz926
• Languages: English
• ISSNs: 0035-8711

Abstract

ABSTRACT: Discovery of periodic maser emission was an unexpected result from monitoring observations of methanol transitions in high-mass young stellar objects. We report on the detection of five new periodic sources from a monitoring program with the Torun 32 m telescope. Variability with a period of 149 to 540 d and different patterns from sinusoidal-like to intermittent was displayed. Three-dimensional structure of G59.633−0.192 determined from the time delays of burst peaks of the spectral features and high angular resolution map implies that the emission traces a disc. For this source the 6.7 GHz light curve followed the infrared variability supporting a radiative scheme of pumping. An unusual time delay of ∼80 d occurred in G30.400−0.296 could not be explained by the light travel time and may suggest a strong differentiation of physical conditions and excitation in this deeply embedded source. Our observations suggest the intermittent variability may present a simple response of maser medium to the underlying variability induced by the accretion luminosity while other variability patterns may reflect more complex changes in the physical conditions.