Australia Telescope Compact Array observations for project C3743 semester 2025OCTS

Ultra-long gamma-ray bursts (ULGRBs) with durations exceeding 1000 seconds represent extreme stellar explosions that challenge current understanding of cosmic death scenarios. Recent theoretical advances favor magnetar central engines over traditional collapsar models, but observational discrimination remains elusive. This proposal requests ATCA time for systematic radio afterglow studies of ULGRBs to test competing progenitor models through unique radio diagnostics unavailable at other wavelengths. The observational strategy implements rapid-response multi-frequency monitoring spanning 300 days post-burst, optimized to detect magnetar energy injection signatures including late-time plateau phases, achromatic rebrightenings, and modified spectral evolution. Radio observations probe circumburst environments through self-absorption frequency evolution and investigate potential two-component jet structures revealed in recent discoveries. ATCA's southern hemisphere coverage captures 60-70% of Swift-detected events, with rapid-response capabilities enabling crucial early-time observations. The 10-epoch monitoring strategy provides complete temporal sampling of afterglow evolution phases while maintaining practical feasibility. Expected outcomes include the first definitive radio evidence for magnetar central engines in ULGRBs, comprehensive environment characterization distinguishing wind versus ISM scenarios, and potential discovery of unique jet structures. Even a single detection would double the current sample of radio-detected ULGRBs, establishing optimal strategies for future surveys and providing quantitative tests of theoretical models.