IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023B983 PROGRAM_TITLE Comet 12P Outburst Number 2 PROGRAM_INV1 Michael Disanti PROGRAM_INV2 PROGRAM_INV3 PROGRAM_INV4 PROGRAM_INV5 PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG Halley-Type Comet 12P/Pons-Brooks is currently in outburst, having brightened by more than 4 magnitudes over the past 2 days or so, and persisting through last night. We are requesting use of iSHELL on 12P. We have identified IR Flux Standard HR6324 (Lmag 3.92, spectral class A0V), which could be measured at the beginning and during evening twilight. Given these circumstances, we note that IRTF is the only facility that can make these measurements of parent volatiles in 12P. 12P is currently around 2.55 au (heliocentric). Our plan is to concentrate on the hyper-volatiles CO, CH4, and C2H6, which requires sampling the comet in 2 settings (M2, which includes CO and H2O, and Lp1, which includes C2H6 and CH4 as well as OH emissions), although getting even 1 setting on 12P would aid in planning and interpreting our (proposed/pending) serial observations in 2024A (PI Gibb), in the context of the comet in an outbursting state. The geocentric velocity is -16 to -17 km/s, which makes measuring/constraining both CO and CH4 feasible. Furthermore, sampling C2H6 will help tie to future abundances of all species, as it is relatively easy to detect in comets and is independent of any particular geocentric Doppler shift. PROGRAM_ABSTRACT_END