Long term 6.7 GHz methanol maser monitoring program

Abstract

The first long-term maser (mainly methanol) monitoring program is under way with the radio telescopes of Ventspils International Radio Astronomy Center. The first activity of this program was to develop an observations methodology and data registration and reduction software for the Ventspils telescopes. The developed routines are to be used for maser variability monitoring, investigating short bursts of intensity and a search for new, previously unknown, maser sources. Currently the program consists of 41 methanol masers observed at 6.7 GHz, while new ones are periodically added. The maser sources are observed at 3 – 5 day intervals. It was found that most the sources display a significant level of variability with time, ranging from a few days, up to several months and, perhaps, years. In addition to non-varying masers, several types of maser variability behavior were observed, including: monotonic increases or decreases, un-periodical, quasi-periodic and periodic variations.

First Galactic Maser Observations on Ventspils Radio Telescopes – Instrumentation and Data Reduction

“…The further data processing was done by program complex developed in VIRAC sprli.py with following steps shown in figures below: (i)converting data in Jy; (ii)cutting (under manual control) the spectral region with maser lines; (iii)the zero level of signal is found and gain dependence of system gain is compensated; (iv)averaging between left and right polarization channels; (v)noise filtering by using Gaussian 1DK kernel from Astropy program package. The overview of the CH 3 OH observation program and its first results is given at Aberfelds et al (2018).…”

VIRAC Maser Data Processing Suite

“…In the year 2017 Ventspils International Radio Astronomy Centre (VIRAC) team of astronomers and engineers started to work on the maser monitoring programme (Aberfelds et al, 2017). That included technical and scientific development.…”