  Markarian 501 is a high-peaked BL Lacertae object and has undergone many
major outburst since its discovery in 1996. As a part of the multiwavelength
campaign, in the year 2009 this blazar was observed for 4.5 months from March 9
to August 1 and during the period April 17 to May 5 it was observed by both
space and ground based observatories covering the entire electromagnetic
spectrum. A very strong high energy $\gamma$-ray flare was observed on May 1 by
Whipple telescope in the energy range 317 GeV to 5 TeV and the flux was about
10 times higher than the baseline flux. We use the photohadronic model
complimented by the extragalactic background radiation (EBL) correction to this
very high state flare and have shown that the EBL plays an important role in
attenuating the very high energy flux even though Markarian 501 is in the local
Universe.
