Letter to the Editor

The X-ray emission mechanism in the protostellar jet HH 154

¹ Dip. Scienze Fisiche ed Astronomiche, Sez. Astronomia, Università di Palermo, P.zza del Parlamento 1, 90134 Palermo, Italy e-mail: sbonito@oapa.astropa.unipa.it
² INAF - Osservatorio Astronomico di Palermo, P.zza del Parlamento 1, 90134 Palermo, Italy
³ Astrophys. Div. – Res. and Science Support Dept. of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
⁴ Dept. of Astronomy and Astrophysics, Univ. of Chicago, Chicago, IL 60637, USA
⁵ Center for Astrophysical Thermonuclear Flashes, University of Chicago, 5640 S. Ellis Avenue, Chicago, IL 60637, USA

Received: 7 May 2004
Accepted: 24 June 2004

Abstract

We study the mechanism causing the X-ray emission recently detected in protostellar jets, by performing a detailed modeling of the interaction between a supersonic jet originating from a young stellar object and the ambient medium, for various values of density contrast, ν, between the ambient density and the jet, and of Mach number, M; radiative losses and thermal conduction have been taken into account. Here we report a representative case which reproduces, without any ad hoc assumption, the characteristics of the X-ray emission recently observed in the protostellar jet HH 154. We find that the X-ray emission originates from a localized blob, consistent with observations, which moves with velocity  km s^-1; we therefore predict the X-ray source to have a detectable proper motion.