High-J v=0 SiS Maser Emission in IRC+10216: A New Case of Infrared Overlaps

TL;DR

This paper reports the first detection of specific SiS maser emissions in IRC+10216, revealing inhomogeneous regions near the star and proposing IR line overlaps as the pumping mechanism, indicating potential for more maser lines in high-J transitions.

Contribution

It presents the first observation of SiS masers in multiple high-J transitions and suggests a new IR overlap pumping mechanism in a C-rich star environment.

Findings

Detected SiS masers in J=11-10, 14-13, 15-14 transitions

Identified IR line overlaps as the pumping mechanism

Predicted existence of more maser lines in high-J SiS transitions

Abstract

We report on the first detection of maser emission in the J=11-10, J=14-13 and J=15-14 transitions of the v=0 vibrational state of SiS toward the C-rich star IRC+10216. These masers seem to be produced in the very inhomogeneous region between the star and the inner dust formation zone, placed at 5-7 R*, with expansion velocities below 10 km/s. We interpret the pumping mechanism as due to overlaps between v=1-0 ro-vibrational lines of SiS and mid-IR lines of C2H2, HCN and their 13C isotopologues. The large number of overlaps found suggests the existence of strong masers for high-J v=0 and v=1 SiS transitions, located in the submillimeter range. In addition, it could be possible to find several rotational lines of the SiS isotopologues displaying maser emission.