Gravitational Wave Follow-up of Gamma-Ray Bursts During the First Part of the Fourth LIGO-Virgo-KAGRA Observing Run

Since the detection of GW170817 and its associated Gamma-Ray Burst (GRB) 170817A, the promise of multi-messenger astronomy has been clearly established. Yet such events remain rare, requiring systematic follow-up of electromagnetic triggers to build a comprehensive picture. We report on gravitational wave searches for compact binary coalescences, triggered by external observations of short/ambiguous GRBs during the first part of the fourth LIGO-Virgo-KAGRA observing run (O4a), spanning May 24, 2023, to January 16, 2024. We employed PyCBC, built for modeled searches using the matched-filtering algorithm, and the PyGRB coherent ranking statistic for multidetector networks, updated for O4. Our analysis includes GRBs reported by the Fermi Gamma-ray Burst Monitor (GBM), Swift Burst Alert Telescope (BAT), and the Interplanetary Network (IPN). We will present the updates to PyGRB, current status of this work, and discuss implications for future multi-messenger observations.