Time resolved spectroscopy of GRB 030501 using INTEGRAL*

The gamma-ray instruments on-board INTEGRAL offer an unique opportunity to perform time resolved analysis on GRBs. The imager IBIS allows accurate positioning of GRBs and broad band spectral analysis, while SPI provides high resolution spectroscopy. GRB 030501 was discovered by the INTEGRAL Burst Alert System in the ISGRI field of view. Although the burst was fairly weak (fluence $F_{20-200 \,{\rm keV} } \simeq 3.5 \times 10^{-6}\,\rm{erg\,cm}^{-2})$it was possible to perform time resolved spectroscopy with a resolution of a few seconds. The GRB shows a spectrum in the 20–400 keV range which is consistent with a spectral index $\Gamma = -1.8$. No emission line or spectral break was detectable in the spectrum. Although the flux seems to be correlated with the hardness of the GRB spectrum, there is no clear soft to hard evolution seen over the duration of the burst. The INTEGRAL data have been compared with results from the Ulysses and RHESSI experiments.