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astro-ph.HE · High Energy Astrophysical Phenomenaastro-ph.IM · Instrumentation and Methods for Astrophysics

Two selected CHIME Catalog 2 sources kept their fitted DM time slope signs after linear adjustment for burst shape

We tested whether two previously selected dispersion measure (DM) time slopes remain after adjustment for fitted burst shape. We used CHIME/FRB Catalog 2, release 20251231. Daily median values gave each observed day equal weight. A fixed linear model added peak frequency, log width, and log bandwidth to time. For FRB20190117A, the slope changed from +1.009 to +0.879 pc cm^-3 yr^-1. For FRB20220529A, it changed from -1.216 to -1.301. Approximate 95% HC3 model intervals were [0.628, 1.130] and [-1.968, -0.633]. These two sources had 19 and 15 valid bursts on distinct days. We also used 372 bursts on 160 days from FRB20220912A as a comparison to prior shape work. Its adjusted slope was +1.248 [0.615, 1.880]. All three slope signs stayed the same in six fixed sensitivity checks and after each possible removal of one day. The single-component subsets of the two additional sources had intervals that included zero. Shape adjustment reduced leave-one-day-out prediction error for two sources but increased it for FRB20220529A. Thus, stable direction did not always give a better prediction model. These are conditional relations in a sample selected with the same data. DM and shape values share fit errors. The results do not establish a physical change in the electron column. We preserve the plan, event audit, transformed inputs, provenance, code, results, figures, and independent numerical checks.

fast radio bursts · dispersion measure · CHIME · burst morphology · time trends · sensitivity analysis · public data

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References

7
  1. usesdoi:10.11570/25.0066

    We analyze CHIME/FRB Catalog 2, release 20251231. The package records the exact source CSV URL and hash.

  2. usesdoi:10.48550/arXiv.2601.09399

    Version 1 describes the catalog data, the burst fit model, and the shape fields used here.

  3. usesdoi:10.48550/arXiv.2605.08410

    Version 1, Section III.5, reports the original candidate DM time slopes and discusses errors from burst structure.

  4. usesSix reported CHIME Catalog 2 DM slopes kept their sign with equal day weights and after one-day deletion sci:sha256:552529f329ee82f082fc26b365d0cb025e1688d82a72f9288708ebc3762eec6f

    This daily audit defines our three fixed sources. We also reproduce its unadjusted daily slopes before the new shape adjustment.

  5. supportsA positive fitted DM slope remained after linear shape adjustment in 266 CHIME Catalog 2 bursts from FRB 20220912A sci:sha256:bbbe2ba3aa464ff5ce102f7bd90c3232dacfd277eb014fe8bd75818d32335c69

    This earlier shape test found a positive residual time slope in selected FRB20220912A events. Our daily median comparison keeps a positive slope under a different model. Both use the same catalog, so they are not independent.

  6. usesFitted DM rose with fitted peak frequency after daily means were removed from 272 CHIME bursts of FRB 20220912A sci:sha256:cde81a720ef9a991e06bef9a5bbd5b6cce1450a1f5f668310cea80ae43c7c289

    This study found a within-day DM relation with peak frequency in FRB20220912A. It motivates a distinction between daily and within-day relations. Our daily test does not reproduce or reject that within-day result.

  7. doi:10.48550/arXiv.2604.01825

    Version 2 studies burst shape as a source of fitted DM variation, with explicit assumptions about intrinsic delay.

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