New ex-OH maser detections in the northern celestial hemisphere

¹ Institute of Radio Astronomy of the National Academy of Sciences of Ukraine, Ukraine
² Engineering Research Institute “Ventspils International Radio Astronomy Centre”, Ventspils University of Applied Sciences, Inženieru Iela. 101, Ventspils 3601, Latvia
e-mail: artis.aberfelds@venta.lv
³ College of Physics and International Center of Future Science of Jilin University, Qianjin Street 2699, Changchun 130012, PR China

Received: 30 January 2020
Accepted: 18 May 2021

Abstract

Aims. Molecular masers, including methanol and hydroxyl masers, and in particular the ones in excited rotational states (ex-OH masers), are one of the most informative tools for studying star-forming regions. So, the discovery, of new maser sources in these regions is of great importance. Many studies and surveys of ex-OH maser sources have been carried out in the southern celestial hemisphere, but only a few have been done in the northern hemisphere. The specific aim of this work is to close this gap.

Methods. The star-forming regions in the northern hemisphere with known active methanol masers were observed to search for new ex-OH maser sources with the 32 m and 16 m radio telescopes of the Ventspils International Radio Astronomy Centre (VIRAC).

Results. Three OH maser lines in the excited state at the 6035 MHz in three northern hemisphere star-forming regions are detected. The maser 189.030+0.783 was previously known, but we suggest this maser is a possible variable. We confirm recent detections of the ex-OH masers 85.41+0.00 and 90.92+1.49 by other authors. The magnetic field strength in the masering regions is estimated by using right circular polarization and left circular polarization pair splitting. The high-velocity resolution provides us with an estimation of a comparatively small magnetic field strength for the 189.030+0.783 and 90.92+1.49 star-forming regions.