Ponente
Descripción
We present gamma-ray observations by Major Atmospheric Gamma-Ray Imaging Cherenkov Telescope (MAGIC) and Large Sized Telescope (LST-1) of two of the most compelling gravitational-wave events detected by LIGO-Virgo-KAGRA (LVK) during Observing Run 4 (O4b). Conducted with MAGIC and LST-1 in a multi-telescope configuration, the campaign enabled a sensitive search for very-high-energy counterparts. The results constrain gamma-ray emission models for Binary Black Hole (BBH) mergers, such as super-Eddington accretion and post-merger jets, and demonstrate the capability of current Imaging Atmospheric Cherenkov Telescopes (IACTs) to contribute to multi-messenger astronomy.
The first source, S240615dg, currently the best-localized event of O4, was observed 15 hours after the alert under challenging conditions due to observations taken at high zenith angles and elevated Night Sky Background (NSB). A hybrid analysis approach was applied, deriving upper limits (ULs) that fully cover the source location (>99% C.R), with LST-1 helping to lower the energy threshold down to 0.15 TeV.
The second source, S241125n, presented a special scenario given the X-ray counterpart candidate detected by Swift/GUANO. Observations began 19 hours after the BBH merger reported by LVK, targeting the reported X-ray position. Due to suboptimal weather, LIDAR-based atmospheric corrections and dedicated Monte Carlo simulations incorporating the cloud profile were used. The results place constraints on gamma-ray emission from the X-ray counterpart above 0.6 TeV.
