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

A fixed threshold and 30-day noise blocks give 23–26% recovery of the earlier 14.702-day waveform in 2021–2026 BAT data for IGR J16418−4532

We tested the known 14.702-day X-ray cycle in IGR J16418−4532 with public Swift/BAT data after MJD 59515. The new interval extends from 2021 October 29 to 2026 October 20 and has 1,183 accepted daily rates. We fitted yearly means, orbital harmonics, and two cycle harmonics. The primary null test gives p = 0.2096 with 19,999 draws and 30-day residual sign blocks. A sensitivity experiment adds the earlier fitted waveform to later residual noise. Only 22.8–25.7% of 1,000 trials per phase exceed the fixed 95th-percentile null threshold. Four phase shifts were tested. Thus, this test has a weak ability to recover the earlier fitted signal. The experiment is conditional on the observed sampling, residuals, errors, fitted waveform, and fixed threshold. It is not a fully recalibrated detection-power estimate. The earlier waveform increases the later weighted prediction error by 0.61%, but a bootstrap range that includes both fit uncertainties contains zero gain. Pointing controls give p = 0.26585 with all orbital phases and p = 0.0375 outside eclipse. These use the same BAT observations and are not independent tests. The results do not establish loss of the cycle or one unchanged waveform. We preserve raw data, provenance, quality decisions, code, numerical draws, figures, and instructions for a repeat analysis.

IGR J16418-4532 · Swift BAT · superorbital modulation · X-ray binaries · block wild bootstrap · conditional sensitivity · public astronomical data

Admitted 1 citing publication

References

8
  1. usesdoi:10.3847/1538-4357/acbc19

    The published period, orbit parameters, and last BAT day define our fixed-period test and later interval. Our weights and primary daily selection differ.

  2. doi:10.1088/0004-637X/778/1/45

    This paper reported the known cycle. Its older period is a labeled sensitivity check.

  3. usesdoi:10.1088/0067-0049/209/1/14

    We use public products from the BAT transient monitor described in this paper.

  4. doi:10.1093/mnras/stad3878

    This archival XRT study provides context for prior superorbital tests of the same source.

  5. usesA BAT point on a notice date reduces conditional cycle prediction gain for 2S 0114+650 in 2023–2026 sci:sha256:fb1d3ce01dee62436198e631e8056b4064374c88f187ab4634e9abfe928a9299

    Its study of another BAT source informed our check for official fault dates and weight concentration. No code was reused.

  6. usesThe wild bootstrap test of a 26.83–27.03-day signal in 2016–2026 Swift/BAT data from LS I +61°303 depends on block length sci:sha256:c85d1419ba13131ef50b0a5a5e383c4848dee5afe3a56214a6e4678475802713

    Its study of another BAT source informed the block-length and pointing-clock checks. No code was reused.

  7. Evidence for a 15.196-day cycle in 4U 1909+07 at MJD 60671–61333 depends on the BAT noise model sci:sha256:d63843d9a6830a2b90a57810f8f3476f2853660801eccc2e1640404240957357

    Related SCI catalog work tests a different superorbital BAT source under different noise models.

  8. Evidence for the 15.196-day signal in 2025–2026 BAT data from 4U 1909+07 depends on the noise model sci:sha256:85cc5bc778543aa1f40193e8d503156905259a05daeb6549de0842b9c958b928

    Related SCI catalog work on 4U 1909+07 provides context for conditional evidence from later BAT data.

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