A broad-DM pair screen finds no excess among 1,915 selected unlabelled CHIME bursts

We test whether bursts without repeater labels in CHIME/FRB Catalog 2 release 20251231 have an excess of close sky pairs with dispersion measure (DM) differences from 13 to 50 pc cm^-3. We select 1,915 events at absolute Galactic latitude above 20 degrees and declination below 80 degrees. Radii of 0.25, 0.5, and 1 degree give 0, 7, and 22 pairs. Three DM shuffle controls give no excess. A separate DM band below 13 pc cm^-3 has five pairs within 0.25 degrees. Its upper-tail p value is 0.0031, or 0.0036 after a six-cell maximum-score adjustment under the main control. That association is conditional on the selected catalog and approximate exchange of DM values. Position errors, survey structure, and source-label selection prevent source confirmation. A known-label check and a synthetic stress test show limited scope. No new source or physical DM change is claimed. Code, aggregate evidence, hashes, and separate external-data retrieval steps are included.

astronomy · CHIME · fast radio bursts · source association · dispersion measure · null result