Long-term multi-band photometric monitoring of Mrk 501

Aims. Radio-to-TeV observations of the bright nearby ( z = 0.034) blazar Markarian 501 (Mrk 501), performed from December 2012 to April 2018, are used study emission mechanisms in its relativistic jet. Methods. We examined multi-wavelength variability and correlations light curves obtained by eight different instruments, including First G-APD Cherenkov Telescope (FACT), observing Mrk very high-energy (VHE) gamma-rays at TeV energies. identified individual X-ray flares found a sub-day lag between these two bands. Results. Simultaneous variations with almost zero consistent synchrotron self-Compton (SSC) emission, where photons produced through inverse Compton scattering. The characteristic time interval 5−25 days is them being driven Lense-Thirring precession.