Letter to the Editor

No evidence yet for hadronic TeV gamma-ray emission from SNR RX J1713.7-3946

Institut für Theoretische Physik, Lehrstuhl IV: Weltraum-und Astrophysik, Ruhr-Uni ver si tät Bochum, 44780 Bochum, Germany

Corresponding author: O. Reimer, olr@tp4.ruhr-uni-bochum.de

Received: 7 May 2002
Accepted: 11 June 2002

Abstract

Recent TeV-scale observations with the CANGAROO II telescope have led to the claim that the multi-band spectrum of RX J1713.7-3946 cannot be explained as the composite of a synchrotron and an inverse Compton component emitted by a population of relativistic electrons. It was argued that the spectrum of the high-energy emission is a good match to that predicted by pion decay, thus providing observational evidence that protons are accelerated in SNR to at least TeV energies. In this Letter we discuss the multi-band spectrum of RX J1713.7-3946 under the constraint that the GeV-scale emission observed from the closely associated EGRET source 3EG J1714-3857 is either associated with the SNR or an upper limit to the gamma-ray emission of the SNR. We find that the pion-decay model adopted by Enomoto et al. is in conflict with the existing GeV data. We have examined the possibility of a modified proton spectrum to explain the data, and find that we cannot do so within any existing theoretical framework of shock acceleration models.