Antoranz Canales, PedroBarrio Uña, Juan AbelContreras González, José LuisFonseca González, María VictoriaMiranda Pantoja, José MiguelLópez Moya, Marcos2023-06-202023-06-202007-09-200004-637X10.1086/520761https://hdl.handle.net/20.500.14352/50900© The American Astronomical Society. The construction of the MAGIC telescope was mainly made possible by the support of the German BMBF and MPG, the Italian INFN, and the Spanish CICYT, to whom goes our grateful acknowledgment. We would also like to thank the IAC for the excellent working conditions at the Observatorio del Roque de los Muchachos in La Palma. This work was further supported by ETH Research Grant TH 34/04 3 and Polish MNiI Grant 1P03D01028.During its first data cycle, between 2005 and the beginning of 2006, the fast repositioning system of the MAGIC telescope allowed the observation of nine different gamma-ray bursts as possible sources of very high energy gamma-rays. These observations were triggered by alerts from Swift, HETE-2, and INTEGRAL; they started as quickly as possible after the alerts and lasted for several minutes, with an energy threshold varying between 80 and 200 GeV, depending on the zenith angle of the burst. No evidence for gamma signals was found, and upper limits for the flux were derived for all events using the standard analysis chain of MAGIC. For the bursts with measured redshifts, the upper limits are compatible with a power-law extrapolation, when the intrinsic fluxes are evaluated taking into account the attenuation due to the scattering in the metagalactic radiation field.engjournal articlehttp://dx.doi.org/10.1086/520761http://iopscience.iop.orghttp://arxiv.org/abs/astro-ph/0612548open access537539.1GRB 050713ACompton EmissionLong-DurationTEV EmissionAfterglowsSpectraSynchrotronComponentFireballsSearch.Electrónica (Física)ElectricidadFísica nuclear2202.03 Electricidad2207 Física Atómica y Nuclear