Antoranz Canales, PedroBarrio Uña, Juan AbelContreras González, José LuisFonseca González, Mª VictoriaLópez Moya, MarcosMiranda Pantoja, José Miguel2023-06-202023-06-202006-04-10Atkins, R., et al. 2005, ApJ, 630, 996. Band, D., et al. 1993, ApJ, 413, 281 Breiman, L. 2001, Machine Learning, 45, 5. Bretz, T., Dorner, D., Wagner, R. 2003, Proc. 28th Int. Cosmic Ray Conf. (Tsukuba), 5, 2943. Bretz, T., et al. 2005, Proc. 29th Int. Cosmic Ray Conf. (Pune), 4, 315. Connaughton, V., et al. 1997, ApJ, 479, 859. de Jager, O. C., Stecker, F. W. 2002, ApJ, 566, 738. Dermer, C. D., Atoyan, A. 2004, A&A, 418, L5. Dingus, B. L. 1995, Ap&SS, 231, 187. Falcone, A., et al. 2005, GCN Circ. 3581, http://gcn.gsfc.nasa.gov/gcn/gcn3/3581.gcn3. Fegan, D. J. 1997, J. Phys. G, 23, 1013. Galante, N., Bastieri, D., Gaug, M., Garczarczyk, M., Peruzzo, L. 2003, Proc. 28th Int. Cosmic Ray Conf. (Tsukuba), 5, 2753. Galante, N., et al. 2005, GCN Circ. 3747, http://gcn.gsfc.nasa.gov/gcn/gcn3/3747.gcn3. Gaug, M., Bartko, H., Cortina, J., Rico, J. 2005, Proc. 29th Int. Cosmic Ray Conf. (Pune), 5, 375. Götting, N., Horns, D. G. 2003, GCN Circ. 1007, http://gcn.gsfc.nasa.gov/gcn/gcn3/1007.gcn3. González, M. M., Dingus, B. L., Kaneko, Y., Preece, R. D., Dermer, C. D., Briggs, M. S. 2003, Nature, 424, 749. Golenetskii, S., Aptekar, R., Mazets, E., Pal’shin, V., Frederiks, D., Cline, T. 2005, GCN Circ. 3619, http://gcn.gsfc.nasa.gov/gcn/gcn3/3619.gcn3. Goodman, J. 1986, ApJ, 308, L47. Hillas, A. M. 1985, Proc. 19th Int. Cosmic Ray Conf. (La Jolla), 3, 445. Hurley, K., et al. 1994, Nature, 372, 652. Jarvis, A., et al. 2005, Proc. 29th Int. Cosmic Ray Conf. (Pune), 4, 455. Kneiske, T. M., Bretz, T., Mannheim, K., Hartmann, D. H. 2004, A&A, 413, 807. Lazzati, D., Rossi, E., Ghisellini, G., Rees, M. J. 2004, MNRAS, 347, L1. Mészáros, P., Rees, M. J. 1993, ApJ, 418, L59. Mirzoyan, R. 2005, Proc. 29th Int. Cosmic Ray Conf. (Pune), 4, 23. Nikishov, A. I. 1961, Zh. Eksp. Teor. Fiz., 41, 549 (English transl. Soviet Phys.–JETP Lett., 14, 392 [1962]). Paczyn´ski, B. 1986, ApJ, 308, L43. Palmer, D., et al. 2005, GCN Circ. 3597, http://gcn.gsfc.nasa.gov/gcn/gcn3/3597.gcn3 Pe’er, A., Waxman, E. 2004, ApJ, 603, L1. Preece, R. D., Briggs, M. S., Mallozzi, R. S., Pendleton, G. N., Paciesas, W. S., Band, D. L. 2000, ApJS, 126, 19. Ryde, F. 2004, ApJ, 614, 827. Rolke, W., López, A., Conrad, J. 2005, Nucl. Instrum. Meth. Phys. Res. A, 551, 493. Stern, B. E., Poutanen, J. 2004, MNRAS, 352, L35. Vietri, M. 1995, ApJ, 453, 883. Waxman, E. 1995, Phys. Rev. Lett., 75, 386. Zhou, X. 2003, Proc. 28th Int. Cosmic Ray Conf. (Tsukuba), 5, 2757.0004-637X10.1086/503767https://hdl.handle.net/20.500.14352/50934© The American Astronomical Society. The construction of the MAGIC Telescope was mainly made possible by the support of the German Bundesministerium für Bildung und Forschung and Max-Planck-Gesellschaft, the Italian Istituto Nazionale de Fisica Nucleare, and the Spanish Comisión Interministerial de Ciencias y Tecnología, to whom goes our grateful acknowledgement. We are grateful for all the hard work done by the GCN team, especially Scott Barthelmy, and to all the people of the Swift Science Center, who kindly provided us with data and the tools to analyze them. In particular, we are indebted to Professor Guido Chincarini, Abe Falcone, and Professor David Burrows from the Swift collaboration. We are also grateful to Nicola Omodei for fruitful discussions on the physics of GRBs. We would also like to thank the Instituto de Astrofísica de Canarias 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 grant 1P03D01028 from the Polish Ministerstwo Nauki i Informatyzacji.The long-duration gamma-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 approximate to 175 GeV. Using standard MAGIC analysis, no evidence of a gamma-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.engjournal articlehttp://dx.doi.org/10.1086/503767http://iopscience.iop.orghttp://arxiv.org/abs/astro-ph/0602231open access537539.1Energy Cosmic-RaysVery-High-EnergyBurstsBatseGRS-941017AbsorptionComponentSpectraModel.Electrónica (Física)ElectricidadFísica nuclear2202.03 Electricidad2207 Física Atómica y Nuclear