2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/6132We report on observations of Markarian 421 made with the Whipple 10m Cerenkov telescope and the RXTE satellite during a multi-wavelength campaign in December 2002 and January 2003, initiated by a Whipple target of opportunity. The observations revealed several flares with flux levels between 1 and 2 times the flux of the Crab Nebula. We will discuss the temporal properties, including evidence of X-ray/TeV gamma-ray flux correlation.4 pages to be published in the Proceedings of the 28th International Cosmic Ray Conference (Tsukuba, Japan 2003)Astrophysicstext