M87 is a nearby radio galaxy situated close to the center of the Virgo Cluster. It emits radiation across the entire electromagnetic spectrum, extending up to TeV energies, and has experienced several TeV flares detected by H.E.S.S., MAGIC, and VERITAS. The precise location of the TeV gamma-ray emission remains uncertain, mainly due to the limited angular resolution of Imaging Cherenkov Telescopes (IACTs).
In this talk, we examine both the low and high emission states of M87 using H.E.S.S. Our findings indicate the absence of extended emission concealed in the low state, leading to an upper limit on the contribution of a hadronic component to the overall emission. Conversely, our investigation of a stacked high emission state has uncovered a curved VHE spectrum. This curvature is unrelated to either the absorption by the starlight from the galaxy or the absorption by extragalactic background light (EBL) photons.
While the origin of the curvature in the spectrum of M87 remains unidentified, information about the acceleration process is concealed behind it. Subsequent studies will soon provide insights into the acceleration mechanism and the location(s) of the VHE gamma-ray emission of M87.
