%0 Journal Article %A Antoranz Canales, Pedro %A Barrio Uña, Juan Abel %A Contreras González, José Luis %A Fonseca González, María Victoria %A Miranda Pantoja, José Miguel %A Nieto Castaño, Daniel %T Simultaneous multiwavelength observations of Markarian 421 during outburst %D 2009 %@ 0004-637X %U https://hdl.handle.net/20.500.14352/43954 %X We report on the results of two coordinated multiwavelength campaigns that focused on the blazar Markarian 421 during its 2006 and 2008 outbursts. These campaigns obtained UV and X-ray data using the XMM-Newton satellite, while the gamma-ray data were obtained utilizing three imaging atmospheric Cerenkov telescopes, the Whipple 10 m telescope and VERITAS, both based in Arizona, as well as the MAGIC telescope, based on La Palma in the Canary Islands. The coordinated effort between the gamma-ray groups allowed for truly simultaneous data in UV/X-ray/gamma-ray wavelengths during a significant portion of the XMM-Newton observations. This simultaneous coverage allowed for a reliable search for correlations between UV, X-ray, and gamma-ray variability over the course of the observations. Investigations of spectral hysteresis and modeling of the spectral energy distributions are also presented. %~