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

Daily BAT data from 2018–2026 limit fixed 65- and 115-day signals in GX 301−2 under a stated orbit model and independent symmetric noise blocks

We test fixed 65-day and 115-day sinusoids in 2,644 daily Swift/BAT measurements of GX 301−2 from 2018-01-01 through 2026-10-20. The energy band is 15–50 keV. The model has annual means and annual orbital profiles with four harmonics. Neither target passes the joint test. A refitted residual block-sign bootstrap gives approximate joint 95% semiamplitude bounds of 11.78% and 17.47% of the observed mean. These bounds require the stated orbit model and independent symmetric error blocks. Residual structure at orbital lags limits their physical use. They apply to additive signals with fixed phase at exactly the two tested periods. A design audit uses 131 selected months from the public 157-month survey. At the reported monthly times, the largest canonical correlations with the 41.5-day orbit and its 20.75-day harmonic reach 0.9911 near 114.175 days and 0.9918 near 65.200 days. The later daily correlations at 115 and 65 days are 0.0173 and 0.0169. The alias interpretation is prior work from the authors of a withdrawn claim. This contribution adds measured design correlations, later-data conditional bounds, and an exact linear map for bootstrap refits. The package preserves raw data, provenance, code, results, draws, figures, checks, and reproduction instructions.

GX 301-2 · Swift BAT · X-ray binaries · orbital aliases · monthly sampling · daily monitoring · fixed periods · conditional amplitude bounds · block bootstrap

Admitted 1 citing publication

References

6
  1. usesdoi:10.48550/arXiv.2601.09226

    The authors withdrew the earlier 65- and 115-day claim and identified monthly orbital aliases. That interpretation is prior work. We use the fixed rounded periods as the stated targets.

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

    The Swift/BAT monitor supplies the public daily 15–50 keV input data.

  3. usesdoi:10.48550/arXiv.2506.04109

    The 157-month BAT survey supplies the monthly data and times for the design audit.

  4. usesdoi:10.1093/mnras/stad3090

    The BAT period and mean epoch and the summary period derivative define the adopted orbital phase. We do not claim to use the full fitted ephemeris.

  5. usesdoi:10.3368/jhr.50.2.317

    This guide provides the statistical context for cluster covariance, block independence, few clusters, and bootstrap inference.

  6. usesRemoving two known bad BAT days changes the LMC X-4 phase estimate by 0.034 cycles in a weighted daily test sci:sha256:d152ecc67c93e86a6bf741b8e9e67a6acae54dad161b2f67cd427e136b1ddd4f

    This related study documents the same known faulty BAT dates in LMC X-4. We read it after the first GX 301−2 fit. Our exclusion follows the instrument notice. No code or numeric inputs from its package enter this study.

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