IRTF Data Archive Program Information

# # Program information file # PROGRAM_ID 2023A051 PROGRAM_TITLE Characterizing the Parent Volatile Composition and Outgassing of a Target-of-Opportunity Comet PROGRAM_INV1 Michael DiSanti PROGRAM_INV2 Boncho Bonev PROGRAM_INV3 Neil Dello Russo PROGRAM_INV4 Erika Gibb PROGRAM_INV5 Nathan Roth PROGRAM_SCICAT comets PROGRAM_ABSTRACT_BEG We propose using iSHELL to study parent volatile abundances, coma spatial distributions and dynamics in an appropriate ToO comet discovered [or becoming known] during 2023A. Recent surveys have increased the number and rate of comet discoveries [and outbursts], suggesting that comets with sufficient brightness to be measurable with iSHELL are increasingly likely to become available after normal observing proposal deadlines. Potential types of ToO comets that are important to study are: [1] Newly discovered comets [mostly long-period Oort cloud comets] that are sufficiently bright to chemically characterize [e.g. C/1996 B2 Hyakutake; recently C/2020 F3 NEOWISE]. [2] Comets at large heliocentric distances showing unexpected high activity indicative of hypervolatile [CO, CO2, CH4]-driven activity [e.g., C/2016 R2 PanSTARRS], but which are not traditionally proposed for in regular calls due to their insufficient expected brightness. [3] Known comets that undergo unexpected brightening due to outbursts [e.g., 17P/Holmes] or splitting/fragmentation [73P/Schwassmann-Wachmann 3]. We will determine abundances for 'core' parent volatiles having more intense emissions [H2O, HCN, CH3OH, and C2H6], and also for more traditionally difficult-to-detect species [H2CO, C2H2, NH3, OCS]. For core volatiles, we will also determine spatial distributions and temperature variations in the coma. Provided one becomes available, we will target any sufficiently bright comet having large enough geocentric Doppler-shift [15-20 km/s, or higher], to determine abundances and spatial distributions of the hypervolatiles CO and CH4. We will utilize our collaborations to explore relationships between parent volatiles [C2H2, HCN, NH3], and product species [C2, CN, NH, NH2] from optical observations [McDonald, TRAPPIST, APO]. The IR studies can only be done with iSHELL, utilizing the high sensitivity and efficiency of iSHELL together with flexible IRTF scheduling including the ability for rapid ToO turn around and daytime observing. PROGRAM_ABSTRACT_END