Free access article

A&A 432, L5-L8 (2005)
DOI: 10.1051/0004-6361:200500009

Letter

Isotopic abundance of nitrogen and carbon in distant comets

J. Manfroid¹, E. Jehin², D. Hutsemékers¹, A. Cochran³, J.-M. Zucconi⁴, C. Arpigny¹, R. Schulz⁵ and J. A. Stüwe<sup>6

1</sup>  Institut d'Astrophysique et de Géophysique, Université de Liège, Allée du 6 Août 17, 4000 Liège, Belgium
    e-mail: manfroid@astro.ulg.ac.be
²  European Southern Observatory, Casilla 19001, Santiago, Chile
³  Department of Astronomy and McDonald Observatory, University of Texas at Austin, C-1400 Austin, USA
⁴  Observatoire de Besançon, 25010 Besançon Cedex, France
⁵  ESA/RSSD, ESTEC, PO Box 299, 2200 AG Noordwijk, The Netherlands
⁶  Leiden Observatory, 2300 RA Leiden, The Netherlands

(Received 13 December 2004 / Accepted 20 January 2005)

Abstract
The ¹²C ¹⁴N/ ¹²C ¹⁵N and ¹²C ¹⁴N/ ¹³C ¹⁴N isotopic ratios have been determined in comets C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT) and C/2003 K4 (LINEAR) at heliocentric distances of, respectively, 2.7, 3.7 and 2.6 AU. These ratios have also been measured at AU. No significant differences were found between all determinations, nor with the value obtained for other comets. If confirmed, the discrepancy between the nitrogen isotopic ratios from optical and millimeter measurements on CN and HCN would rule out HCN as a major parent of the cometary CN radicals.

Key words: comets: abundances -- comets: individual: C/1995 O1 (Hale-Bopp), C/2001 Q4 (NEAT), C/2003 K4 (LINEAR)

© ESO 2005

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