Variations in Volatile-Driven Activity of Comet C/2017 K2 (PanSTARRS) Revealed by Long-Term Multi-Wavelength Observations
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| Main Authors: | , , , , , , , , , |
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| Format: | Preprint |
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2025
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| _version_ | 1866915474131910656 |
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| author | Hmiddouch, S. Jehin, E. Lippi, M. Donckt, M. Vander Aravind, K. Hutsemékers, D. Manfroid, J. Jabiri, A. Moulane, Y. Benkhaldoun, Z. |
| author_facet | Hmiddouch, S. Jehin, E. Lippi, M. Donckt, M. Vander Aravind, K. Hutsemékers, D. Manfroid, J. Jabiri, A. Moulane, Y. Benkhaldoun, Z. |
| contents | Context. A comprehensive study of comets over a wide heliocentric distance range helps us understand the physical processes driving their activity and reveals compositional differences across dynamical groups. C/2017 K2 (PANSTARRS) is a Dynamically New Oort Cloud comet (DNC) that showed activity as far as 23.75 au and displayed a CO-rich coma at 6.72 au, making it a key object to investigate pre- and post-perihelion behavior.
Aims. We aim to study the long-term activity evolution and chemical composition of C/2017 K2 using photometry and spectroscopy, from October 2017 (r$_h$ = 15.18 au) pre-perihelion to April 2025 (r$_h$ = 8.46 au) post-perihelion.
Methods. Broad-band and narrow-band imaging from both TRAPPIST telescopes enabled us to produce an 8-year light curve, color analysis, and derivation of activity slopes. Production rates of OH, NH, CN, C$_3$, and C$_2$ were computed using a Haser model, along with the dust proxy A(0)f$ρ$. High-resolution spectra from CRIRES$^+$ and UVES at three epochs (May - September 2022) provided simultaneous observations of parent and daughter species as the comet crossed the water sublimation zone.
Results. The light curve of C/2017 K2 shows a complex evolution with varying slopes and a brightness plateau around perihelion, indicating multiple active species. Coma colors remained constant, suggesting uniform dust properties and similarity to other active long-period comets. Gas production rates indicate a typical C$_2$/CN composition with a high dust-to-gas ratio. Analysis of forbidden oxygen lines shows a transition from CO and CO$_2$-driven activity to water-driven sublimation inside 3 au. Infrared spectra reveal C/2017 K2 as a typical-to-enriched comet, with HCN identified as the main parent of CN, and C$_2$ likely originating from C$_2$H$_2$ rather than C$_2$H$_6$. |
| format | Preprint |
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arxiv_https___arxiv_org_abs_2507_13451 |
| institution | arXiv |
| publishDate | 2025 |
| record_format | arxiv |
| spellingShingle | Variations in Volatile-Driven Activity of Comet C/2017 K2 (PanSTARRS) Revealed by Long-Term Multi-Wavelength Observations Hmiddouch, S. Jehin, E. Lippi, M. Donckt, M. Vander Aravind, K. Hutsemékers, D. Manfroid, J. Jabiri, A. Moulane, Y. Benkhaldoun, Z. Earth and Planetary Astrophysics Context. A comprehensive study of comets over a wide heliocentric distance range helps us understand the physical processes driving their activity and reveals compositional differences across dynamical groups. C/2017 K2 (PANSTARRS) is a Dynamically New Oort Cloud comet (DNC) that showed activity as far as 23.75 au and displayed a CO-rich coma at 6.72 au, making it a key object to investigate pre- and post-perihelion behavior. Aims. We aim to study the long-term activity evolution and chemical composition of C/2017 K2 using photometry and spectroscopy, from October 2017 (r$_h$ = 15.18 au) pre-perihelion to April 2025 (r$_h$ = 8.46 au) post-perihelion. Methods. Broad-band and narrow-band imaging from both TRAPPIST telescopes enabled us to produce an 8-year light curve, color analysis, and derivation of activity slopes. Production rates of OH, NH, CN, C$_3$, and C$_2$ were computed using a Haser model, along with the dust proxy A(0)f$ρ$. High-resolution spectra from CRIRES$^+$ and UVES at three epochs (May - September 2022) provided simultaneous observations of parent and daughter species as the comet crossed the water sublimation zone. Results. The light curve of C/2017 K2 shows a complex evolution with varying slopes and a brightness plateau around perihelion, indicating multiple active species. Coma colors remained constant, suggesting uniform dust properties and similarity to other active long-period comets. Gas production rates indicate a typical C$_2$/CN composition with a high dust-to-gas ratio. Analysis of forbidden oxygen lines shows a transition from CO and CO$_2$-driven activity to water-driven sublimation inside 3 au. Infrared spectra reveal C/2017 K2 as a typical-to-enriched comet, with HCN identified as the main parent of CN, and C$_2$ likely originating from C$_2$H$_2$ rather than C$_2$H$_6$. |
| title | Variations in Volatile-Driven Activity of Comet C/2017 K2 (PanSTARRS) Revealed by Long-Term Multi-Wavelength Observations |
| topic | Earth and Planetary Astrophysics |
| url | https://arxiv.org/abs/2507.13451 |