Periodic variation in the water production of comet C/2001 Q4 (NEAT) observed with the Odin satellite

Nicolas Biver (1) , Dominique Bockelée-Morvan (1) , Pierre Colom (1) , Jacques Crovisier (1) , Alain Lecacheux (1) , Urban Frisk (2) , Åke Hjalmarson (3) , Michael Olberg (3) , Aage Sandqvist (4)

1 LESIA - Laboratoire d'études spatiales et d'instrumentation en astrophysique
2 SSC - Swedish Space Corporation
3 OSO - Onsala Space Observatory, Chalmers University of Technology
4 Stockholm Observatory, AlbaNova University Center

Context: Comet C/2001 Q4 (NEAT) was extensively studied with the 1.1-m submillimetre telescope of the Odin satellite. The H2O line at 557 GHz was regularly observed from 6 March to 16 May 2004 and nearly continuously monitored during 3 periods between 26 April and 2 May 2004.
Aims: This last set of data shows periodic variations in the line intensity, and we looked for characterising the long- and short-term behaviour of this comet.
Methods: We used the variance ratio method and chi² minimization to find the period of variation in the water production rate and simulations to infer its amplitude at the nucleus surface.
Results: A 40% periodic variation in the water production rate is measured with a period of 0.816±0.004 day (19.58±0.1 h). The comet also exhibits a seasonal effect with a mean peak of outgassing around 2.7×10²⁹ molec. s^-1 taking place about 18 days before perihelion.

Domaines: Astrophysique [astro-ph]; Planète et Univers [physics]

Nicolas Biver, Dominique Bockelée-Morvan, Pierre Colom, Jacques Crovisier, Alain Lecacheux, et al.. Periodic variation in the water production of comet C/2001 Q4 (NEAT) observed with the Odin satellite. Astronomy and Astrophysics - A&A, 2009, 501, pp.359-366. ⟨10.1051/0004-6361/200911790⟩. ⟨hal-03786112⟩