Temporary EHBL-like behavior of Markarian 501 during July 2014 VHE flaring

Temporary EHBL-like behavior of Markarian 501 during July 2014 VHE flaring
Sarira Sahu, A. U. Puga Oliveros, D. I. P’aez-S’anchez, G. S’anchez-Col’on, Subhash Rajpoot, M. E. Iglesias Mart’inez, Jos’e Guerra Carmenate, P. Fern’andez de C’ordoba, Gaetano Lambiase
arXiv:2502.07940v2 Announce Type: replace
Abstract: Markarian 501, a BL Lac object well-known as a high energy gamma-ray source, has exhibited several epochs of very high energy (VHE) gamma-ray flaring events when its synchrotron peak frequency shifted above $10^{17}$ Hz, a signature of extreme behavior. From July 16 to July 31, 2014 such flaring events were observed for 15 days by various telescopes. On July 19 (MJD 56857.98), the X-ray outburst from the source was at its highest and on the same day an intriguing narrow peak-like feature around 3 TeV was observed by the MAGIC telescopes, a feature inconsistent with standard interpretations. Using the well-known two-zone photohadronic model, we study these VHE gamma-ray spectra on a day-by-day basis and offer explanation. Our two-zone photohadronic scenario shows that, on MJD 56857.98, the peak-like feature appears at a cutoff energy of $E^c_{gamma}=3.18$ TeV. Below this energy the VHE spectrum increases slowly and is in high emission state. However, for $E^c_{gamma}, > 3.18$ TeV, the spectrum falls faster, resulting in a mild peak-like feature, not prominent enough as claimed by the MAGIC collaboration.arXiv:2502.07940v2 Announce Type: replace
Abstract: Markarian 501, a BL Lac object well-known as a high energy gamma-ray source, has exhibited several epochs of very high energy (VHE) gamma-ray flaring events when its synchrotron peak frequency shifted above $10^{17}$ Hz, a signature of extreme behavior. From July 16 to July 31, 2014 such flaring events were observed for 15 days by various telescopes. On July 19 (MJD 56857.98), the X-ray outburst from the source was at its highest and on the same day an intriguing narrow peak-like feature around 3 TeV was observed by the MAGIC telescopes, a feature inconsistent with standard interpretations. Using the well-known two-zone photohadronic model, we study these VHE gamma-ray spectra on a day-by-day basis and offer explanation. Our two-zone photohadronic scenario shows that, on MJD 56857.98, the peak-like feature appears at a cutoff energy of $E^c_{gamma}=3.18$ TeV. Below this energy the VHE spectrum increases slowly and is in high emission state. However, for $E^c_{gamma}, > 3.18$ TeV, the spectrum falls faster, resulting in a mild peak-like feature, not prominent enough as claimed by the MAGIC collaboration.