First VHE gamma-ray observations of BL Lacertae with the Large-Sized Telescope (LST-1)

The Large-Sized Telescope (LST-1) is the first prototype telescope for the future Cherenkov Telescope Array Observatory (CTAO) northern site, located in the Roque de los Muchachos in La Palma. The telescope detected the Very High Energy (VHE) gamma ray signal from BL Lacertae, the namesake for the AGN-blazar class, in 2021 and has since then collected many observations of the object. This has allowed us to study extreme levels of VHE variability in an unprecedented flare of the source. The analysis and results will become the base of one of the very first scientific results from the LST collaboration. We will present the results of the BL Lac 2021 observational campaign, including the VHE gamma-ray lightcurve of BL Lacertae detected by the LST-1 in 2021, together with its measured Spectral Energy Distribution.