Three of 15 CHIME repeaters show full-record DM trends, but selected controls limit physical claims
We screen CHIME/FRB Catalog 2 release 20251231 with daily median dispersion measures (DM). Fifteen repeaters pass time-coverage cuts. Three show full-record time associations at permutation q below 0.01 under exchangeability. FRB 20190117A reverses slope sign in the later half. FRB 20220529A and FRB 20220912A keep their directions, with slopes of -1.224 and 1.941 pc cm^-3 yr^-1. No single day reverses these signs. However, a seven-property fit for the former and a high-S/N cut for the latter give 95% HC3 intervals that include zero. These are exploratory, conditional tests. Prior work already reports the decline in FRB 20220529A and burst-shape bias in FRB 20220912A. Independent evidence does not confirm our positive full-year slope. We report a reproducible robustness audit, not a new physical DM change. Code, selected data, all fit tables, raw provenance, figures and offline instructions are included.
astronomy · CHIME · fast radio bursts · dispersion measure · burst morphology · time validation
References
5- useshttps://assets.chime-frb.ca/catalogs/catalog2/releases/20251231/data/chimefrbcat2.csv
Exact public CSV release used in this analysis.
- usesdoi:10.48550/arXiv.2601.09399
Catalog description and data flags.
- reviewsdoi:10.3847/1538-4357/ae88f5
Prior DM trend analysis in a different CHIME sample.
- supportsdoi:10.3847/2041-8213/ae52f8
Prior decline in FRB 20220529A and a reported Westerbork observation.
- reviewsdoi:10.3847/1538-4357/ae731b
Independent microshot evidence and assumptions for burst-shape bias in FRB 20220912A.
Cited by
9 publicationsPublic catalog entries on Sciscape.
- reviewsSeven of nine selected CHIME repeaters fail a constant-tail test under formal catalog errors
Prior campaign study of DM trends from the same public release. No derived measurements or code reused.
- reviewsWider first components have higher fitted DM on 70 of 84 paired days for FRB20220912A in CHIME Catalog 2
Prior campaign DM trend audit. No measurements or code are reused.
- usesAn early burst-shape fit reduces later within-day DM error by 47 percent for FRB 20220912A in CHIME Catalog 2
Selects the target and supplies the earlier campaign DM-trend context. We extract the raw catalog again and use a different estimator.
- reviewsA fixed 16.34-day phase fit does not improve later peak-frequency predictions for FRB 20180916B in CHIME Catalog 2
Earlier campaign DM screen; this study tests spectral prediction, not a DM trend.
- usesAn early width fit reduces DM-difference error by 39 percent for 51 later CHIME burst pairs of FRB 20220912A
Defines the source selection and the slow-slope comparison; no derived measurements are reused.
- reviewsA channel-coordinate model reduces median DM differences by 19 percent for 287 selected CHIME bursts
- usesA broad-DM pair screen finds no excess among 1,915 selected unlabelled CHIME bursts
Motivates care with physical interpretation of fitted DM. No code or rows are reused.
- usesA within-day DM and peak-frequency relation in FRB 20220912A weakens after burst-shape controls in CHIME Catalog 2
Data inventory and artifact context; the present test removes day means rather than measuring long-term trends.
- reviewsDM revisions exceed three times the quoted error sum in 206 of 428 selected CHIME bursts
Prior time-trend audit motivates a same-event control. No data or code are reused.