An investigation into the variability of methanol and hydroxyl masers in the star-forming region G12.89+0.49

Abstract

It is now widely accepted that 6.7 GHz and 12.2 GHz class I1 methanol masers are signposts of very young high mass star-forming regions. The exact location of these masers is still a matter of debate, they may be in disks or shocks near these objects. Hydroxyl masers also show strong emission at 1665 MHz in these regions. They may be excited by the same mechanisms as the methanol masers. Both maser species sometimes show variability. The information from maser variability can be useful in determining conditions and physical changes occurring in these regions. A daily monitoring program was set up to study the variability of methanol and hydroxyl masers in the G12.89+0.49 star-forming region. G12.89+0.49 is one of the 54 sources monitored by Goedhart et al. (2004). It had shown a flickering behaviour which was not fully characterised, hence the current observations were undertaken. Methanol masers were observed at 6.7 GHz and 12.2 GHz and hydroxyl masers at 1665 MHz using the 26-m telescope at Hartebeesthoek. The results show that the methanol maser exhibits regular variability with a period between 29 and 30 days. The hydroxyl masers show a little variability.