Speaker
Description
The extragalactic very-high-energy (VHE, E>100 GeV) gamma-ray sky is dominated by blazars. Most are of the BL Lacs subclass, and only 10 flat spectrum radio quasars (FSRQ) are known in this energy band. OP 313 was detected by the Large-Sized Telescope prototype (LST-1) for the Cherenkov Telescope Array Observatory (CTAO) in December 2023. It is a record-breaking FSRQ in terms of distance at a redshift of z=0.997 and was detected during one of the most luminous long-lasting blazar outbursts ever recorded by the Fermi-LAT in its 16 years of operations. The discovery of VHE emission from OP 313 opens an interesting science case for CTAO: the study of VHE sources in a cosmological epoch when galaxy mergers had a more predominant role at fueling AGN activity and star formation rate was much higher than in the current era.
In this contribution, we will discuss the observations of OP 313 and the rich multi-wavelength campaign designed to monitor the state of the source in multiple energy bands during its period of maximum activity. This result represents a major scientific success of LST-1, and a preview of what is to come with the construction of three more LSTs at Roque de los Muchachos Observatory (La Palma, Spain), the northern site of CTAO.
