113 CHIME bursts from FRB 20180916B need a window of at least 5.11 days for constant periods of 16.0 to 16.7 days
We measured the smallest repeated time window for 113 distinct bursts from FRB 20180916B. The data are from CHIME/FRB Catalog 2, release 20251231. We converted arrival times to barycentric TDB. We searched constant periods from 16.0 to 16.7 days and allowed any phase origin. Each burst must be inside the repeated window. A finite search of 9,219 candidate periods gives a global minimum width of 5.1118121 days at a period of 16.3256310 days. An independent integer calculation confirms the result within its 1e-8-day rounding bound. Three bursts give a separate interpolation certificate. The minimum is unchanged by the tested catalog quality cuts. The 22 bursts after 2021 increase the minimum by 1.62 hours. Removal of one occupied cycle can reduce the width to 4.4009 days. This shows the role of the edge events. On the fixed cycle branch, a 5.2-day window permits constant periods from 16.32390 to 16.32857 days. A quadratic clock reduces the minimum width to 4.86452 days. Zero period change remains feasible for a 5.2-day window. These are deterministic containment results. They are not confidence intervals or a detection of period change. We do not model exposure or detection efficiency. Thus, the measured width does not establish the intrinsic activity window. The package preserves factual source extracts, provenance, code, proofs, results, figures, and reproduction instructions.
FRB 20180916B · CHIME · fast radio bursts · activity period · circular data · linear programming · reproducible astronomy
References
7- usesdoi:10.11570/25.0066
Catalog 2 release 20251231 supplies the component arrival times, event identifiers, positions, and quality flags.
- usesdoi:10.48550/arXiv.2601.09399
The Catalog 2 paper describes the measurements used here.
- doi:10.1038/s41586-020-2398-2
This paper established the known activity period of the source.
- usesdoi:10.3847/1538-4357/acf221
The reference period 16.34 days and epoch MJD 58369.40 define the fixed cycle labels. This paper also gives prior period and period-change results.
- doi:10.48550/arXiv.2507.04609
Frequency-dependent fitted activity profiles differ from a hard interval that contains every event.
- doi:10.1051/0004-6361/202452508
Earlier work used inactivity information in period searches with few burst detections.
- Peak frequency has a negative fitted phase slope in 104 CHIME bursts of FRB 20180916B with a linear time term sci:sha256:ea636893a1b6db79e9e07de450fc280011d6bc7ae7ff7e3df1737475ddb9fb7c
This SCI study uses the same catalog source for a spectral association and explains why its phase slope does not confirm a trial clock. The present work tests timing containment directly.
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