Early CN Outgassing and Production Rates of C/2024 E1 (Wierzchos) at 4 au

The study of cometary activity at large heliocentric distances provides insights into the volatile release processes in the outer solar system. Early models predicted cometary activity was driven primarily by sublimation of water and therefore would cease beyond the water snowline (2.5–3.5 au). However, observations have revealed several comets active well beyond this limit, suggesting the presence of additional mechanisms. The recently discovered Oort Cloud comet C/2024 E1 (Wierzchos) represents an opportunity to investigate the onset of distant activity in a dynamically new comet, a topic of particular relevance for ESA’s Comet Interceptor mission. We conducted visible spectroscopic monitoring of comet E1 with the Multi-Object Double Spectrographs at the Large Binocular Telescope to follow it from 6.3 to 3.3 au preperihelium. In this work, we report the first detection of CN emission, with the B–X (0–0) band observed as far as 4.05 au. We computed molecular production rates in the Haser coma model approximation. We found the onset of the CN radical B–X band as far as ∼4 au from the Sun. We report the following production rates: (5.50 ± 1.43) · 1024 molec s−1 at 4.05 au; (6.77 ±1.43) · 1024 molec s−1 at 3.82 au; and (4.25 ± 0.83) · 1025 molec s−1 at 3.33 au. We measured upper limits on C2 and C3 at rh = 3.3 au and found ratios with CN of log(Q (Formula presented) C2 /Q (Formula presented) CN ) < −0.51 and log(Q (Formula presented) C3 /Q (Formula presented) CN ) < −1.66. These values tentatively classify this comet as carbon-chain depleted.