Speaker
Description
In April 2013, the TeV blazar Mrk421 underwent one of its most powerful emission outbursts to date. An extensive multi-instrument campaign, which included MAGIC, VERITAS, and NuSTAR, provided comprehensive VHE and X-ray coverage over nine consecutive days.
In this talk I will present a detailed spectral analysis of the X-ray and VHE emissions on sub-hour timescales throughout the flare. We identify several clockwise spectral hysteresis loops in the X-rays. The VHE spectrum extends above 10 TeV, and its temporal evolution closely mirrors the behavior in the X-rays, thus revealing the first evidence of VHE spectral hysteresis simultaneous with the X-rays.
We apply a time-dependent leptonic model to 240 broadband SEDs binned at 15-minute intervals, allowing us to self-consistently track the particle distribution's history on sub-hour scales. The majority of the sub-hour flux and spectral variations are well reproduced by evolving the luminosity and slope of the injected electron distribution. To capture the VHE spectra at the highest energies, a Doppler factor of ~100 is needed, implying relativistic motion of the emitting plasma in the jet frame. While this could be realized in plasmoid chains formed in current sheets during magnetic reconnection, the particle hardness evolution would require significant changes in the plasma magnetization during the flare.
We release the entire MAGIC dataset (~40hrs) to the community in DL3 file format, together with the large sample of broadband SEDs.
