Speaker
Description
Blazars are a sub-class of Active Galactic Nuclei (AGN) and constitute the most populous class of sources in the extragalactic very-high-energy (VHE) sky. They are characterized by rapid variability that spans from radio to VHE gamma rays (E > 100 GeV), whose origin remains under debate. Detecting more VHE blazars at different energies and distances is crucial for a better understanding of their emission mechanisms.
The Large-Sized Telescope prototype (LST-1) of the Cherenkov Telescope Array Observatory (CTAO) is located on the Roque de los Muchachos in La Palma, Spain. With its high sensitivity down to tens of GeV, it is the best suited instrument to observe gamma-ray sources such as AGN due to lack of absorption from photon-photon interactions with the extragalactic background light. From 2020 to 2022, we accumulated more than 150 hours of data of several well-known AGN with redshifts in the range 0.03 to 0.45: Mrk 421, Mrk 501, 1ES 1959+650, 1ES 0647+250, PG 1553+113. In this contribution, we will present the results on the spectral variability from these observations, including the Mrk 421 flare with sub-hour timescale variability as measured in May 2022. We also report the Fermi-LAT spectra simultaneous to LST-1 observations, which show good agreement between both results and prove that LST-1 is highly sensitive to gamma-ray sources with time variation above tens of GeV. These results foresee an exceptional performance of AGN detection with LST-1 and CTAO in the future.
