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Session 62 - Comet Hyakutake Encounter.
Display session, Wednesday, June 12
Great Hall,

[62.05] Connexion between C2 Emission and Condensation Knot in Hyakutake's Coma

C. Laffont, P. Rousselot, J. Clairemidi, G. Moreels (Observatoire de Besancon)

Images of Comet Hyakutake were taken at Observatoire de Haute-Provence on March 30.0 and 31.0. Narrow spectral bands were selected at 513 nm: C2 (1,1); 516 nm: C2 (0,0); 527 nm: mid-continuum and 682 nm: red continuum. The condensation detected on March 25 by several observers (Lecacheux et al., IAUC 6354; Tozzi et al., IAUC 6357) is apparent in the images on March 31.0. After subtraction of the continuum, the C2 emission shows two components: i) a main one that radially decreases from the nucleus ii) a secondary one having a crescent shape located between the nucleus and the condensation. The ratio of narrow-band images in the (1,1) and (0,0) bands of C2 shows that both components of the C2 emission have different excitation temperatures. Given the long time needed by the C2 molecules to reach their fluorescent equilibrium, the initial population distributions for both C2 components are not the same. It may thus be proposed that the C2 crescent-shaped emission is due to the ejection of the fragment. This assumption is supported by the Monte-Carlo model of C2 developed by Rousselot et al. (Aamp;A 1994, 286, 645; Icarus 1995, 114, 341).

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