Long-term monitoring of a dynamically new comet C/2020 V2 (ZTF)

ABSTRACT Comet C/2020 V2 (ZTF, Zwicky Transient Facility) is categorized as a dynamically new long-period comet, making its first approach to the inner Solar system. We have observed this comet for around 32 months (from 2022 January to 2024 July) at heliocentric distances from 5.41 au (pre-perihelion) to 5.26 au (post-perihelion) through various telescopes, employing photometric (60 epochs) and spectroscopic techniques (5 epochs). Using these observations, we derived the production rates of different molecules such as CN$(0-0)$, C$_2(\Delta \nu =0)$, and C$_3$ and calculated the production rate ratios. The values of the ratios closest to the perihelion are found to be $\log$ (C$_2/$CN) $= -0.04 \pm 0.03$ and $\log$ (C$_3/$CN) $= -0.70 \pm 0.04$, which implies a typical carbon composition. The mean photometric broad-band colours are found to be $B-V = 0.77\pm 0.04$, $V-R = 0.43\pm 0.04$, $R-I = 0.42\pm 0.06$, and $B-R = 1.19\pm 0.04$. The stability of the molecular production rate ratios and mean photometric broad-band colours, pre- and post-perihelion, implies a homogeneous composition. The mean reflectivity gradient for $B-V$ colour is $10.90 \pm 3.62 \,\mathrm{ per\,cent}/1000$ Å; $V-R$ colour is $6.15 \pm 3.51 \,\mathrm{ per\,cent}/1000$ Å; and for $R-I$ colour is $4.94 \pm 3.56 \,\mathrm{ per\,cent}/1000$ Å which is similar to the mean value of the dynamically new comets. Additionally, using an asymmetric non-gravitational force model, we report the comet’s nuclear radius to be $1.1 \pm 0.1$ km. Our results are expected to provide inputs to the selection of a potential dynamically new comet as a target for the Comet Interceptor mission.