Free access article

A&A 394, 517-523 (2002)
DOI: 10.1051/0004-6361:20021133

COMPTEL upper limits for the Co -ray emission from SN1998bu

R. Georgii^{1, 2}, S. Plüschke¹, R. Diehl¹, G. G. Lichti¹, V. Schönfelder¹, H. Bloemen³, W. Hermsen³, J. Ryan⁴ and K. Bennett<sup>5

1</sup>  Max-Planck-Institut für extraterrestrische Physik, Postfach 1312, 85741 Garching, Germany
²  FRM-II, Technische Universität München, Lichtenbergstr. 1, 85747 Garching, Germany
³  SRON Institute for Space Research, Sorbonnelaan 2, 3584 CA Utrecht, The Netherlands
⁴  Space Science Center, University of New Hampshire, Durham, NH 03824, USA
⁵  Science Division, ESTEC, ESA, 2200 AG Noordwijk, The Netherlands

(Received 20 February 2002 / Accepted 1 August 2002 )

Abstract
Supernova 1998bu in the galaxy M 96 was observed by COMPTEL for a total of 88 days starting 17 days after the explosion. We searched for a signal in the 847 keV and 1238 keV lines of radioactive ⁵⁶Co from this type Ia supernova. Using several different analysis methods, we did not detect SN1998bu. Our measurements should have been sensitive enough to detect ⁶⁰Co gamma-rays as predicted from supernova models. Our flux limit is  photons cm ^-2 s ^-1; this would correspond to 0.35   of ejected ⁵⁶Ni, if SN1998bu were at a distance of 11.3 Mpc and transparent to MeV gamma rays for the period of our measurements. We discuss our measurements in the context of common supernova models, and conclude disfavoring a supernova event with large mixing and major parts of the freshly-generated radioactivity in outer layers.

Key words: stars: supernovae: individual: SN1998bu -- gamma-rays: observations -- nucleosynthesis

Offprint request: R. Georgii, rgeorgii@frm2.tum.de

© ESO 2002

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