EDP Sciences
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Volume 386, Number 1, April IV 2002
Page(s) 204 - 210
Section Formation, structure and evolution of stars
DOI http://dx.doi.org/10.1051/0004-6361:20011387

A&A 386, 204-210 (2002)
DOI: 10.1051/0004-6361:20011387

Discovery of X-ray emission from the protostellar jet L1551 IRS5 (HH 154)

F. Favata1, C. V. M. Fridlund1, G. Micela2, S. Sciortino2 and A. A. Kaas3

1  Astrophysics Division - Space Science Department of ESA, ESTEC, Postbus 299, 2200 AG Noordwijk, The Netherlands
2  Osservatorio Astronomico di Palermo, Piazza del Parlamento 1, 90134 Palermo, Italy
3  Nordic Optical Telescope, Apartado 474, 38700 Santa Cruz de la Palma, Canarias, Spain

(Received 20 July 2001 / Accepted 27 September 2001 )

We have for the first time detected X-ray emission associated with a protostellar jet, on the jet emanating from the L1551 IRS5 protostar. The IRS5 protostar is hidden behind a very large absorbing column density, making the direct observation of the jet's emission possible. The observed X-ray emission is likely associated with the shock "working surface", i.e. the interface between the jet and the circumstellar medium. The X-ray luminosity emanating from the jet is, at $L_{\rm X} \simeq 3 \times 10^{29}$ erg s -1, a significant fraction of the luminosity normally associated with the coronal emission from young stars. The spectrum of the X-ray emission is compatible with thermal emission from a hot plasma, with a temperature of $\simeq$4 MK, higher than the temperature expected (on the basis of the jet's velocity) for the shock front produced by the jet hitting the circumstellar medium.

Key words: ISM: clouds -- ISM: individual objects: L1551: HH 454 -- ISM: jets and outflows -- stars: formation -- stars: pre-main sequence -- radio lines: ISM

Offprint request: F. Favata, Fabio.Favata@rssd.esa.int

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© ESO 2002

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