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Astron. Astrophys. 330, 321-326 (1998)


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COMPTEL -ray study of the Crab nebula

R.D. van der Meulen 2, 5, H. Bloemen  2, 5, K. Bennett  4, W. Hermsen  2, L. Kuiper  2, R.P. Much  4, J. Ryan  3, V. Schönfelder 1 and A. Strong  1

1 Max-Planck-Institut für Extraterrestrische Physik, P.O. Box 1603, D-85740 Garching, Germany
2 SRON-Utrecht, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
3 Space Science Center, University of New Hampshire, Durham, NH 03824, USA
4 Astrophysics Division, ESTEC, 2200 AG Noordwijk, The Netherlands
5 Leiden Observatory, P.O. Box 9513, 2300 RA Leiden, The Netherlands

Received 19 December 1996 / Accepted 11 September 1997

Abstract

We report on a study of the [FORMULA] -ray continuum emission from the Crab supernova nebula and on a search for nuclear de-excitation [FORMULA] -ray lines. Crab is the brightest continuum source in the 1-10 MeV [FORMULA] -ray sky, and its continuum radiation is most likely of synchrotron origin. It is a likely source of cosmic rays through shock acceleration and thus a potential candidate for [FORMULA] -ray line emission from nuclear interactions. Five years of COMPTEL observations enable a fine spectral binning to investigate the behaviour of the 0.75-30 MeV emission in detail and to search for nuclear de-excitation lines on top of the continuum. The nebular spectrum shows a break at the edge of the COMPTEL energy range and connects well to the EGRET spectrum, probably reflecting electron energy losses in the synchrotron emission scenario. Such a smooth continuum model alone may not be sufficient to explain the observations. A weak bump in the spectrum at 1-2 MeV may be present. No significant evidence for distinct line emission is seen, but the presence of a blend of line features or another synchrotron component cannot be excluded.

Key words: ISM: Crab nebula – cosmic rays – ISM: supernova remnants – gamma-rays: observations

Send offprint requests to: R.D. van der Meulen
(R.vanderMeulen@sron.ruu.nl)

© European Southern Observatory (ESO) 1998

Online publication: January 8, 1998
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