Coma composition and profiles of comet 12P/Pons-Brooks using long-slit spectroscopy

Abstract

Comet 12P/Pons-Brook exhibited multiple large and minor outbursts in 2023 on its way to its 2024 perihelion, as it has done during its previous apparitions. We obtained long-slit optical spectra of the comet in 2023 August and 2023 November with the INT-IDS, and in 2023 December with NOT-ALFOSC. Using a standard Haser model in a 10000km-radius aperture and commonly used empirical parent and daughter scale-lengths, our calculated abundance ratios show a constant "typical" composition throughout the period with a C${}_2$/CN ratio of about 90 per cent. Molecular density profiles of different species along the slit show asymmetries between opposite sides of the coma and that C${}_2$ seems to behave differently than CN and C${}_3$. Comparing the coma profiles to a standard Haser model shows that this model cannot accurately reproduce the shape of the coma, and therefore that the calculated production rates cannot be deemed as accurate. We show that an outburst Haser model is a {slightly} better match to the C${}_3$ and CN profile shapes, but the model still does not explain the shape of the C${}_2$ profiles and requires equal parent and daughter scale-lengths. Our results suggest that the coma morphology could be better explained by extended sources, and that the nature of 12P's activity introduces bias in the determination of its composition.

arXiv comment11 pages, 7 figures, accepted for publication in MNRAS

References in corpus (6)

• Summer fireworks on comet 67P
• Thirty Years of Cometary Spectroscopy from McDonald Observatory
• Rotation of Cometary Nuclei: New Lightcurves and an Update of the Ensemble Properties of Jupiter-Family Comets
• Evidence of sub-surface energy storage in comet 67P from the outburst of 2016 July 3
• Long-term activity and outburst of comet C/2013 A1 (Siding Spring) from narrow-band photometry and long-slit spectroscopy
• Near-UV and optical spectroscopy of comets using the ISIS spectrograph on the WHT

Cited by in corpus (5)

• A D/H Ratio Consistent with Earth's Water in Halley-type Comet 12P from ALMA HDO Mapping
• Pre-perihelion radio observations of comet 12P/Pons-Brooks with Tianma radio telescope
• Optical and Near-Infrared Spectroscopy of the Outbursting Comet 12P/Pons-Brooks
• Activity of comet 7P/Pons-Winnecke during the 2021 apparition
• Dust and coma radicals in C/2024 E1 (Wierzchos): evolution of the activity