C/2020 F3 (NEOWISE) production rates from high-resolution TNG/HARPS-N spectra.

The composition of comets hold clues about the early stages of the formation and evolution of the Solar System. Being the brightest comet observed in the northern hemisphere since the passage of comet C/1995 O1 (Hale-Bopp) in 1997, comet C/2020 F3 (NEOWISE) represents an interesting target for studying its coma composition and the chemical inventory of its nucleus. We aim to estimate the production rate (mol/s) for the chemical species identified in the coma. By comparing with other comets, we aim to assess whether this comet is typical or peculiar, and investigate any distinctive feature. From high resolution (R ​= ​115000) spectra of C/2020 F3 at 0.72 AU from the Sun obtained with the HARPS-N instrument at the TNG, we measured the flux of selected C 2 , CN, C 3 , NH 3 and O(1D) bands and emission lines, that were converted to production rates (Q) through the Haser formalism. From O(1D) we derive the production rate of water molecules. These values are then normalized with respect to CN and water production rates and compared with results from other spectroscopic surveys. We estimate production rates Q (CN) = (1.55 ​± ​0.39) ⋅ 1026 ​mol/s, Q (C 2) = (1.76 ​± ​0.32) ⋅ 1026 ​mol/s, Q (C 3) = (0.32 ​± ​0.12) ⋅ 1026, Q (H 2 O) = (3481.32 ​± ​3.48) ⋅ 1026 ​mol/s and Q (NH 2) = (10.58 ​± ​3.64) ⋅ 1026 ​mol/s. With respect to water, we find relatively lower (by a factor of ≈ 4 − 5) CN and C 2 mixing ratios and a relatively high NH 2 mixing ratios than other comets, especially for heliocentric distances below 1 AU. The calculated production rates and their ratios highlight discrepancies in the sublimation of comet C/2020 F3 with respect to Solar System comets and are consistent with the presence of a nucleus with a heterogeneous composition, already proposed in literature. • We estimate production rates of C2, CN, C3 NH2 and water for comet C/2020 F2 (NEOWISE) at 0.72 AU through high-resolution spectroscopy and Haser modelling • We find significantly higher NH2based and water ice sublimation with respect to a sample of Solar System comets • We find significant depletion in C-based ices • We suggest that the cometary activity of C/2020 F3 can be explained by a nucleus of heterogeneous composition [ABSTRACT FROM AUTHOR]