INTEGRAL and XMM-Newton observations of the low-luminosity and X-ray-rich burst GRB 040223

GRB 040223 was observed by INTEGRAL and XMM-Newton. GRB 040223 has a peak flux of (1.6 ±0.13)×10−8 ergs cm−2 s−1, a fluence of(4.4±0.4)×10−7 ergs cm−2 and a steep photon power law index of −2.3±0.2, in the energy range 20–200 keV. The steep spectrum implies it is an X-ray–rich GRB with emission up to 200 keV and Epeak < 20 keV. If Epeak is < 10 keV, it would qualify as an X-ray flash with high-energy emission. The X-ray data has a spectral index βx = −1.7 ± 0.2, a temporal decay of t−0.75±0.25 and a large column density of 1.8 × 1022 cm−2. The luminosity-lag relationship was used to obtain a redshift z = 0.1+0.04−0.02 . The isotropic energy radiated in γ-rays and X-ray luminosity after 10 hours are factors of 1000 and 100 less than classical GRBs. GRB 040223 is consistent with the extrapolation of the Amati relation into the region that includes XRF 030723 and XRF 020903.