2025ApJS..277....9C

The Gravitational Wave High-energy Electromagnetic Counterpart All-sky Monitor (GECAM) is a dedicated mission consisting of multiple instruments on different spacecraft to monitor gamma-ray transients. To meet the requirement of GECAM, we developed the Energetic Transients Joint Analysis System for Multi-INstrument (ETJASMIN) pipeline, which has been extended to incorporate other instruments (such as Fermi-GBM, SVOM/GRM). In this work, we introduce the ETJASMIN pipeline with focus on the search, verification, and classification of gamma-ray transients (especially weak bursts) using data from GECAM-B, GECAM-C, and Fermi-GBM. For this pipeline, we implement a coherent algorithm to search for simultaneous signals in the light curves of multiple instruments, conduct a series of Monte Carlo simulations, and validate the pipeline performance with in-flight observation data. The results demonstrate that ETJASMIN can yield not only higher significance of burst search but also more reliable verification and classification of bursts jointly with multiple instruments compared to those derived with an individual instrument. Thus, ETJASMIN is particularly suitable for the exploitation of gamma-ray transients associated with multimessenger multiwavelength sources.