The N${}_2$ Production Rate in Comet C/2016 R2 (PanSTARRS)

Abstract

Observations of comet C/2016 R2 (PanSTARRS) have revealed exceptionally bright emission bands of N${}_2^{+}$, the strongest ever observed in a comet spectrum. Alternatively, it appears to be poor in CN compared to other comets, and remarkably depleted in H${}_2$O. Here we quantify the N${}_2$ production rate from N${}_2^{+}$ emission lines using the Haser model. We derived effective parent and daughter scalelengths for N2 producing N2+. This is the first direct measurement of such parameters. Using a revised fluorescence efficiency for N2+, the resulting production rate of molecular nitrogen is inferred to be Q(N${}_2$) ~ 1 $\times 10^{28}$ molecules.s-1 on average for 11, 12, and 13 Feb. 2018, the highest for any known comet. Based on a CO production rate of Q(CO) ~ 1.1 $\times 10^{29}$ molecules.s-1, we find Q(N$-2$)/Q(CO)~0.09, which is consistent with the N${}_2^{+}$/CO${}^{+}$ ratio derived from the observed intensities of N${}_2^{+}$ and CO${}^{+}$ emission lines. We also measure significant variations in this production rate between our three observing nights, with Q(N${}_2$) varying by plus or minus 20% according to the average value

8 pages, 6 figures

References in corpus (4)

• Unusually High CO Abundance of the First Active Interstellar Comet
• High resolution optical spectroscopy of the ${\mathrm{N}}_2$-rich comet C/2016 R2 (PanSTARRS)
• Photometric and spectroscopic analysis of Comet 29P/Schwassmann-Wachmann 1 activity
• A physico-chemical model to study the ion densitydistribution in the inner coma of comet C/2016 R2(Pan-STARRS)