Pre-perihelion production rates of C2 (upper) and CN (lower) in 2I/Borisov in 2019 September–November; its perihelion is 2019 December 8. The left two panels show the measurements and upper limits in Fitzsimmons et al. (2019), Kareta et al. (2019), Opitom et al. (2019b), Lin et al. (2019), and this work. The dark blue shaded region in the bottom left panel shows the continuous upper and lower limit measurements provided in Kareta et al. (2019) for the production of CN during this period. The right two panels show our observations with MUSE, Trappist North and Trappist South.
Pre-perihelion ratio of the production rates of C2 and CN in 2I/Borisov in 2019 September–November; its perihelion is 2019 December 8. We show the measurements and upper limits in Fitzsimmons et al. (2019), Kareta et al. (2019), Opitom et al. (2019b), Lin et al. (2019), and this work as a function of 2I/Borisov’s heliocentric distance in the left panel. The two black points show the ratios measured with the observations with MUSE on November 14-15 and November 25, when both CN and C2 are detected at high SNR. In the right panel, the purple histograms show the ratio of production rates for comets in the sample presented in A’Hearn et al. (1995). The solid lines indicate the measured values and upper limits for Borisov, with the same color scheme as in the left panel. The black dashed line indicates the commonly accepted definition for carbon depleted comets, log[Q(C2)/Q(CN)]≤ −0.18
The full paper is Bannister, M., Opitom, C., Fitzsimmons, A., and 11 coauthors including Seligman, D. "Interstellar comet 2I/Borisov as seen by MUSE: first C2, NH2 and red CN detections." ApJL, 2020.