Astron. Astrophys. 343, L87-L90 (1999)

Letter to the Editor

Infrared spectral observations of comet 103P/Hartley 2 by ISOPHOT ^*

L. Colangeli ¹, E. Epifani ^1,2, J.R. Brucato ¹, E. Bussoletti ³, C. DeSanctis ⁴, M. Fulle ⁵, V. Mennella ¹, E. Palomba ^1,6, P. Palumbo ³ and A. Rotundi <sup>3

1</sup> Osservatorio Astronomico di Capodimonte, via Moiariello 16, I-80131 Napoli, Italy
² Dipartimento di Ingegneria Aerospaziale, Università degli Studi "Federico II", P.le Tecchio, I-80100 Napoli, Italy
³ Istituto Universitario Navale, via A. De Gasperi 5, I-80133 Napoli, Italy
⁴ IAS - CNR, Via del Fosso del Cavaliere, I-00133 Roma, Italy
⁵ Osservatorio Astronomico di Trieste, Via Tiepolo 11, I-34131 Trieste, Italy
⁶ Observatoire de Haute Provence de CNRS, F-04870 Saint Michel l'Observatoire, France

Received 15 December 1998 / Accepted 14 February 1999

Abstract

Spectral observations in the 2.5-12 µm range of comet 103P/Hartley 2 were performed on 1 Jan. 1998 by the ISOPHOT instrument, on board the Infrared Space Observatory. The obtained spectrum evidences intense bands at 2.66 and 4.26 µm, attributable to H₂O and CO₂, respectively. The derived molecular production rates are Q(H₂O) = (3.1 0.2) 10²⁸ molec. s^-1 and Q(CO₂) = (2.5 0.3) 10²⁷ molec. s^-1. This leads to a CO₂/H₂O abundance ratio of 8%, showing that P/Hartley 2 is a relatively CO₂ abundant comet, with respect to 1P/Halley and several other comets. A feature has been detected at 3.69 µm, whose attribution is rather puzzling. The long wavelength part of the spectrum is well fitted by a black-body profile at 285 K colour temperature. No significant silicate emission feature around 10 µm is observed, within observation errors.

Key words: comets: individual: 103P/Hartley 2 infrared: solar system

* Based on observations with ISO, an ESA project with instruments funded by ESA Member States (especially the PI countries: France, Germany, the Netherlands and the United Kingdom) and with participation of ISAS and NASA.

Send offprint requests to: L. Colangeli

This article contains no SIMBAD objects.

Contents

• 1. Introduction
• 2. Observations
• 3. Discussion
• 4. Conclusions
• Acknowledgements
• References

© European Southern Observatory (ESO) 1999

Online publication: March 1, 1999
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