A comparative study of gas activity in the long-period comet C/1977 R1 (Kohler)
Abstract
To support and complement space-based measurements of the gas and dust productivity of comets, we have made a study of the coma activity of comet C/1977 R1 (Kohler). Comet Kohler was the brightest comet of 1977 with an extremely long period of over 100,000 years. The observed spectrum revealed emissions from $NH$, $CN$, $C_2$ and possibly $C_3$, but nothing from $OH$, $CH$, $NH_2$ or $CO^+$. The continuum was very weak implying that the comet was considerably depleted in dust production. Here, we deduce water production rates from the photometric observations taken from COBS semi-empirically, using the Semi-Empirical Method of Visual Magnitudes (SEMVM) model. Our results are consistent with complementary radio observations of the $OH$ radical and narrow-band photometry. We determine water release rates and find an effective radius of $3.0 \pm 1.5$ $km$ and a minimum nucleus radius of $\sim 0.9 \pm 0.45$ $km$. A fraction of minimum active surface area of the order of $10-11$% on the sunlit hemisphere, is necessary to explain the rate of water production sublimated by the nucleus of the comet. In addition, these rates were compared with that of the compounds present in the comet spectrum, with results that led to the classification of it as depleted in carbon, contrary to previous studies.
Acknowledgements: We greatly appreciate support from FAPESP (Grant No. 2015/03176-8, Brazil) and the NSF Planetary Astronomy Program (Grant No. 0908529, USA).- Publication:
-
43rd COSPAR Scientific Assembly. Held 28 January - 4 February
- Pub Date:
- January 2021
- Bibcode:
- 2021cosp...43E.309D