Flux Upper Limit on Gamma-Ray Emission by GRB 050713a from MAGIC Telescope Observations

The long-duration γ-ray burst GRB 050713a was observed by the MAGIC Telescope 40 s after the burst onset and followed up for 37 minutes, until twilight. The observation, triggered by a Swift alert, covered energies above ≈175 GeV. Using standard MAGIC analysis, no evidence of a γ-ray signal was found. As the redshift of the GRB was not measured directly, the flux upper limit estimated by MAGIC is still compatible with the assumption of an unbroken power-law spectrum extending from a few hundred keV to our energy range.