Investigating peculiar prompt emission properties of the multi-Peaked GRB 250129A

We present a high-energy spectral analysis of GRB~250129A, which was triggered by the Swift-BAT. The burst exhibits a complex, multi-peaked temporal structure characterized by two distinct emission episodes, with the main peak occurring approximately 180 seconds after the BAT trigger. The time-integrated spectral analysis in the 15–150 keV energy range indicates that a broken power-law (BPL) model provides the best fit, signifying a non-thermal origin of the prompt emission. A time-resolved spectral analysis, performed using the Bayesian block technique, shows that the intervals around the main emission peak are well described by the BPL model, while the fits for low-count intervals remain less constrained. An evident intensity-tracking behavior is observed between the flux and the spectral peak energy (Eₚ). Furthermore, both the Amati relation and hardness–intensity correlation suggest that GRB~250129A occupies an intermediate regime, acting as a bridge between long and ultra-long GRBs.