ACES Submillimetre HCN masers in carbon-rich AGB stars - Ka Tat Wong (Uppsala University, Sweden)
Hydrogen cyanide (HCN) is one of the most abundant molecules in the circumstellar envelopes of carbon-rich AGB stars. Recent single-dish observations have revealed the widespread presence of its emission lines in vibrationally excited states. HCN is also known to have two highly excited
masers at 805 and 891 GHz, which can be observed with ALMA in its highest frequency band. We have observed these submillimetre lines in several carbon-rich stars with ALMA and detected intense maser emission in the inner regions of the envelopes. Thermal emission from ground-state
and vibrationally excited lines is also observed, allowing us to trace the kinematics of the inner wind. These targets will be ideal for long-baseline observations that achieve angular resolutions of less than 10 mas, as recently demonstrated in an ALMA commissioning test.
