Confirmation of the E_peak~src– Eiso (Amati) relation from the X-ray flash XRF 050416A observed by Swift/BAT

摘要

We report Swift Burst Alert Telescope (BAT) observations of the X-ray Flash (XRF) XRF 050416A. The fluence ratio between the 15–25 and 25–50 keV bands of this event is 1.1, thus making it the softest gamma-ray burst (GRB) observed by BAT so far. The spectrum is well fitted by the Band function with E_peak~obs of 15.6_-2.7~+2.3 keV. Assuming the redshift of the host galaxy (z=0.6535), the isotropic-equivalent energy E_iso and the E_peak energy at the GRB rest frame (E_peak~src) of XRF 050416A are not only consistent with the correlation found by Amati et al. and extended to XRFs by Sakamoto et al., but also fill-in the gap of this relation around 30–80 keV range of E_peak~src. This result tightens the validity of the E_peak~src–E_iso relation form XRFs to GRBs.