Orientation effect on the light-curve shape of periodic methanol maser sources

Abstract

ABSTRACT We report the results of our pilot millimeter observations of periodic maser sources. Using SMA, we carried out 1.3-mm observations of G22.357+0.066 and G25.411+0.105, while ALMA 1.3-mm archival data were used in the case of G9.62+0.19E. Two continuum cores (MM1 and MM2) were detected in G22.357+0.066, while three cores (MM1 – MM3) detected in G25.411 + 0.105. Assuming dust-to-gas ratio of 100, we derived the masses of the detected cores. Using the 12CO (2–1) and 13CO (2–1) line emission, we observed gas kinematics tracing the presence of bipolar outflows in all three star-forming regions. In the cases of G22.357+0.066 and G9.62+0.19E, both with similar periodic maser light-curve profiles, the outflowing gas is seen in the north-west south-east direction. This suggest edge-on view of the two sources. G25.411+0.105, with a contrasting light-curve profile, show a spatially collocated blue and red outflow lobes, suggesting a face-on view. Our results suggest that orientation effects may play a role in determining the characteristics of the light curves of periodic methanol masers.