Dust and coma radicals in C/2024 E1 (Wierzchos): evolution of the activity

Abstract

We present multi-epoch R-band imaging and long-slit spectroscopy of the dynamically new comet C/2024 E1 (Wierzchos) during its pre-perihelion phase, spanning heliocentric distances from 4.5 to 2.3 au. The most prominent fluorescence emissions in the visible wavelength range are detected. We measure production rates of CN, C${}_2$, and C${}_3$, while no significant NH${}_2$ signal is identified. In our dataset, CN became detectable at 3.48 au, and C${}_3$ and C${}_2$ at 2.80 au. The mean ratios $\log {\mathrm{C}}_2/\mathrm{CN}=0.00\pm 0.07$ and $\log {\mathrm{C}}_3/\mathrm{CN}=-1.03\pm 0.09$ place the comet in an intermediate taxonomic regime between typical and carbon-depleted populations. Dust production rates, ejection velocities, and particle size distributions are constrained using a Monte Carlo dust tail model that reproduces the observed coma morphology. The dust population is characterized by a power-law size distribution with an exponent of $\sim -3.5$, and particle sizes ranging from 1~$\mu$m to 4~mm. The inferred initial ejection velocities span from $\sim$20$m$s${}^{-1}$ to $\sim$100$m$s${}^{-1}$. We use the empirical relation between CN and OH to estimate the water production rate and derive the dust-to-gas mass ratio for heliocentric distances $r_{\mathrm{h}}\lesssim 3$ au, where water sublimation is expected to dominate the activity regime. The dust-to-gas mass ratio remains consistently above unity, ranging from $\sim$1 to 3 depending on the choice of scale lengths and the CN--OH conversion factor. This result characterizes C/2024 E1 as a ``dust-rich'' comet, where the mass loss is dominated by the refractory component rather than volatiles.

13 pages, 10 figures, (accepted for publication in MNRAS)

References in corpus (7)

• CO-Driven Activity in Comet C/2017 K2 (PANSTARRS)
• A study of the distant activity of comet C/2006 W3 (Christensen) using Herschel and ground-based radio telescopes
• Visible and near-infrared observations of interstellar comet 2I/Borisov with the 10.4-m GTC and the 3.6-m TNG telescopes
• Coma composition and profiles of comet 12P/Pons-Brooks using long-slit spectroscopy
• Photometry and Long-Slit Spectroscopy of Split Comet C/2019 Y4 (ATLAS)
• Long-term monitoring of a dynamically new comet C/2020 V2 (ZTF)
• Activity of comet 7P/Pons-Winnecke during the 2021 apparition