Is there any evidence for extra-dimensions or quantum gravity effects from the delayed MeV-.pdf

a r X i v : a s t r o - p h / 0 4 0 7 4 1 6 v 1 2 0 J u l 2 0 0 4 Is there any evidence for extra-dimensions or quantum gravity effects from the delayed MeV-GeV photons in GRB 940217? K. S. Cheng? and T. Harko? Department of Physics, The University of Hong Kong, Pokfulam Road, Hong Kong (Dated: July 20, 2004) The discovery of X-ray afterglows of GRBs, and the identification of host galaxies of GRBs, confirm the cosmological origin of GRBs. However, the discovery of the delayed MeV-GeV photons in GRB940217 imposes serious challenges for the standard emission model of GRB. Although the delayed MeV-GeV photons might be explained by some some radiation emission mechanisms, the mystery of detecting an 18 GeV photon still remains unsolved. We suggest that the detection of the 18-GeV photon ～4500 s after the keV/MeV burst in GRB 940217 provides a strong evidence for the existence of extra-dimensions and/or quantum gravity effects. The delay scale of the 18-GeV photon leads to an estimation of the fundamental energy scale, associated with the linear energy dependence of the speed of light, of the order of 2.1× 1015 GeV, which is consistent with the results obtained by another independent analysis on the data of OSSE and BATSE. PACS numbers: 04.50.+h, 98.70.Rz, 95.30.Cq, 95.55.Ka I. INTRODUCTION Delayed high-energy photon emissions from gamma-ray burst (GRBs) sources can be considered a well-established fact. In 1994 Hurley et al. [1] observed a particularly energetic burst, GRB 940217, with a duration of around 90 minutes. GRB 940217 is a very strong burst, with a total fluence above 20 keV of (6.6 ± 2.7) × 10?4 erg cm?2 and a duration of ～180 s in the BATSE range. It has the third largest fluence of around 800 BATSE bursts up to the detection time of this burst. During the period of low energy emission, i.e., in the first ～180 s, EGRET detected 10 photons, with energies ranging from a few tens of MeV to a few GeV, with the fluence in this range of ～ 2× 10?5 erg cm?2.