Fermi GBM and Swift BAT pipeline flags seven new magnetar candidates among 550 unassociated bursts

The team ran a coherent GBM detection pipeline on 12 years of data, then applied a statistical association framework that uses BAT arcminute localizations to anchor GBM events and a spatio-temporal clustering algorithm to link unlocalized bursts to common sources. This produced 1170 bursts confidently tied to 11 known magnetars and left 550 bursts unattributed, from which three discovery channels yielded the seven candidates. The catalog reaches the lowest fluences GBM has recorded for magnetar-like events.

Magnetars remain the only confirmed Galactic sources capable of producing the observed short-hard X-ray and soft-gamma-ray bursts at the required luminosities and repetition rates. Adding even a few new members would tighten constraints on magnetic-field decay timescales and the fraction of core-collapse supernovae that produce ultra-magnetized neutron stars, directly affecting models of galactic cosmic-ray acceleration and fast-radio-burst progenitors.

The principal limitation is the absence of arcsecond X-ray or radio positions and spin-period measurements; the candidates rest on statistical clustering alone. Targeted Swift/XRT or NICER observations within the next 12 months could confirm periodicities below 12 s and persistent luminosities above 10^33 erg s^-1, converting statistical candidates into secure additions to the known magnetar population.

Future wide-field monitors such as COSI or the proposed MoonBEAM mission will increase burst detection rates by an order of magnitude; applying the same GBM-BAT association framework to those data streams offers the clearest near-term path to completing the Galactic magnetar census.