A Study of Hydroxyl (Oh) Maser Variability in Ngc 6334I

Abstract

The Cat’s Paw Nebula is part of our host Milky Way galaxy which experienced a significant assumed accretion event resulting in highly variable hydroxyl, water and methanol masers. Not only were these masers variable in intensity but also velocity. The source NGC 6334I was included on the long-term observational program at Hartebeesthoek Radio Astronomy Observatory and we report some of the findings. We find that the peak velocity of some OH maser features varied periodically and experienced a maximum velocity variance of about 8 ð€€€10 %. The variance was observed in both the LCP and RCP of the OH maser dynamic spectra. In LCP, the variation was observed at -10.6 km sð€€€1, and -10.2 km sð€€€1 and the period of variability was 366.01 3.33 and 365.89 1.28 days respectively. In RCP, the velocity only varied periodically at -6.7 km sð€€€1 and its period was found to be 366.69 1.38 days. The period is within the error of one Earth year (365 days). A source identified as NGC 6334-V south of NGC6334I, which is not at the beam center of the telescope, has 1665 MHz OH masers that were detected while observing those from NGC 6334I. As a result of its large angular distance from the beam center (NGC 6334I), the applied local standard of rest velocity (Vlsr ) correction introduced a periodic variation for OH masers originating from NGC 6334-V. Masers from this source whose Earth-Sun motion was not corrected are roughly at angular separation of 500 corresponding to the velocity of -10.2 km/s, 42.50 corresponding to the velocity of -6.7 km sð€€€1 and 400 corresponding to the velocity of -10.6 km sð€€€1. We attempted to determine the magnetic field strength by firstly identifying Zeeman pairs based on the fact that they have similar variability. The magnetic field corresponding to 1665 MHz OH masers from NGC 6334I was found to be -5.8 0.5mG The five years of data used for this study were provided by Hartesbeesthoek Radio Astronomy Observatory (HartRAO) in South Africa. The data was processed and reduced using an in-house program called lines which run on Linux and the analysis was done using a program called Period04 and also using python scripts in Jupyter Notebook. The period of variation was obtained by fitting a sine function to the observational data.