Astron. Astrophys. 331, L17-L20 (1998)

Letter to the Editor

ISO Detection of CO⁺ toward the protostar IRAS 16293-2422  ^*

C. Ceccarelli ^{1, 2}, E. Caux ³, M. Wolfire ^{4, 5}, A. Rudolph ⁶, B. Nisini ², P. Saraceno ² and G.J. White <sup>7

1</sup> Laboratoire d'Astrophysique, Observatoire de Grenoble - BP 53, F-38041 Grenoble cedex 09, France
² CNR-IFSI Area di Ricerca Roma - Tor Vergata, I-00133 Roma, Italy
³ CESR CNRS-UPS, BP 4346, F-31028 Toulouse cedex 04, France
⁴ University of Maryland, College Park, MD, 20742, USA
⁵ Towson University, Department of Physics, Towson, MD 21252 USA
⁶ Harvey Mudd College, Department of Physics, Claremont, CA 91711 USA
⁷ Queen Mary and Westfield College - University of London, Mile End Road - London E1 4NS, UK

Received 7 November 1997 / Accepted 9 December 1997

Abstract

In this letter we report the detection of eight high-N rotational transitions of towards a low mass protostar, IRAS 16293-2422. The source was observed with the Long Wavelength Spectrometer on board the Infrared Space Observatory. This is the first time that has been detected in a low luminosity source and the first time that high-N lines have been detected in any source. The detection of these lines was not predicted by models and consequently, their interpretation is a challenge. We discuss the possibility that the observed emission originates in the dense inner regions illuminated by the UV field created in the accretion shock (formed by infalling material), and conclude that this is an improbable explanation. We have also considered the possibility that a strong, dissociative J-shock at 500 AU from the star is the origin of the emission. This model predicts column densities in rough agreement with the observations if the magnetic field is 1 mG and the shock velocity is 100 km s^-1.

Key words: ISM: jets and outflows ISM: individual: IRAS 16293-2422 stars: formation infrared: ISM: lines

* 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) with the participation of ISAS and NASA.

Send offprint requests to: Cecilia.Ceccarelli@obs.ujf-grenoble.fr

© European Southern Observatory (ESO) 1998

Online publication: February 16, 1998
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