JWST Time-Series Census Finds 1,315 Variables in Terzan 5 and Liller 1, Including First IR Counterparts to Known Pulsars

The method samples every 21 seconds by subtracting consecutive non-destructive reads within each integration, converting standard NIRCam data into a high-cadence infrared movie suited to the compact fields of view of these bulge clusters. This recovered the Rapid Burster's dramatic variability and the orbital modulation of PSR J1748-2446A, delivering the first optical or infrared counterpart for any Terzan 5 pulsar while also revealing 915 new variables in Liller 1, a field with zero prior detections.

Prior optical surveys catalogued 5,604 variables across 151 clusters, overwhelmingly pulsating stars; the new sample is dominated by photometrically variable binaries, exceeding the combined historical total for such systems. The approach bypasses crowding and extinction that defeated ground-based monitoring, demonstrating that JWST's pixel scale and sensitivity match the spatial density of the Galaxy's most extreme stellar environments.

The work connects to earlier radio pulsar timing and Chandra X-ray studies of Terzan 5, showing that infrared variability can now supply the missing counterparts needed to constrain companion masses and evolutionary pathways. It also supplies a ready template for time-domain programs on other dense systems such as the Arches or Quintuplet clusters.

Future observations with the same read-difference pipeline on additional JWST epochs could distinguish long-period binaries from pulsators and test whether the binary fraction in these fossil fragments exceeds that of classical globular clusters.