{sup 14}NH{sub 2}/{sup 15}NH{sub 2} RATIO IN COMET C/2012 S1 (ISON) OBSERVED DURING ITS OUTBURST IN 2013 NOVEMBER
- Koyama Astronomical Observatory, Kyoto Sangyo University, Motoyama, Kamitamo, Kita, Kyoto 603-8555 (Japan)
We performed high-dispersion optical spectroscopic observations of comet C/2012 S1 (ISON) using the High Dispersion Spectrograph (R = 72,000) at the Subaru Telescope on UT 2013 November 15.6, during an outburst that started on UT 2013 November 14. Due to the high gas-production rate of NH{sub 2} during the outburst, we successfully detected weak emission lines of {sup 15}NH{sub 2} and many strong emission lines of {sup 14}NH{sub 2} in the optical wavelength region from 5500 to 8200 Å. The ratio of {sup 14}NH{sub 2}/{sup 15}NH{sub 2} is derived to be 139 ± 38 in comet C/2012 S1 (ISON). This ratio is close to that recently revealed based on the averaged spectrum of 12 comets, ∼130. This is also comparable to the typical cometary isotopic ratio of CN ({sup 12}C{sup 14}N/{sup 12}C{sup 15}N, observed in optical) and HCN (H{sup 12}C{sup 14}N/H{sup 12}C{sup 15}N, observed in radio), ∼150. However, these ratios are much smaller than the protosolar value, {sup 14}N/{sup 15}N = 441 ± 5. Because NH{sub 2} is considered to be a photodissociation product of NH{sub 3} in cometary coma, our result implies the occurrence of {sup 15}N fractionation of NH{sub 3} in the solar nebula or in the presolar molecular cloud.
- OSTI ID:
- 22363987
- Journal Information:
- Astrophysical Journal Letters, Vol. 782, Issue 2; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 2041-8205
- Country of Publication:
- United States
- Language:
- English
Similar Records
IMAGING COMET ISON C/2012 S1 IN THE INNER CORONA AT PERIHELION
CHANDRA OBSERVATIONS OF COMETS C/2012 S1 (ISON) AND C/2011 L4 (PanSTARRS)