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

With inverse variance weights, selected GX 301-2 profiles give a smaller 15-50 keV lag behind 4-10 keV in 2023-2025 than in 2010-2022

We test whether the energy-dependent mean flare time in GX 301-2 changes after 2022. We use public Swift/BAT 15-50 keV and MAXI/GSC 4-10 keV short-bin light curves. Coverage cuts select 104 complete binary orbits in 2010-2022 and 16 in 2023-2025. We fit a constant plus a Lorentzian to each folded profile, with inverse reported variance weights. The hard-band lag is 0.932 day in the early interval and 0.455 day in the late interval. The change is -0.477 day, with a paired whole-orbit bootstrap nominal 95% interval of [-0.800, -0.103] day. The 10-20 keV control gives a change of -0.039 day, with interval [-0.212, 0.151] day. Equal weights for orbit-level phase means give a change of -0.222 day, with interval [-0.581, 0.147] day, which includes zero. In 100 no-change synthetic tests with 200 bootstrap draws per test, the nominal interval covers the truth in 89 cases. This test does not establish calibrated 95% confidence for the primary 2000-draw interval. The smaller lag is a result for selected variance-weighted profiles. Its physical interpretation depends on orbit weights, coverage, response, and variation in flare shape. We do not establish a source-wide physical change or infer orbital decay. We preserve source snapshots, provenance, code, cycle selection, orbit uncertainty draws, and validation results.

GX 301-2 · Swift BAT · MAXI · X-ray binary · flare timing · energy lag · orbit bootstrap · public data

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References

7
  1. usesdoi:10.1093/mnras/stad3090

    The known energy lag and local Lorentzian method motivate this later-interval test. Its source data end before the new interval.

  2. usesdoi:10.1093/mnras/staa1774

    Provides the quoted shared orbital coordinate and prior evidence for the hard-band lag.

  3. usesdoi:10.1051/0004-6361/200912951

    Source of the older orbit parameters used only as a common fold coordinate.

  4. doi:10.1093/mnras/stu756

    Prior evidence for energy-dependent orbital profiles and absorption.

  5. doi:10.22201/ia.01851101p.2025.61.01.03

    Prior study of MAXI flare spectra and variation in orbital flares.

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

    Describes the Swift/BAT transient monitor whose public light curves are used.

  7. usesdoi:10.1093/pasj/61.5.999

    Describes the MAXI mission whose public GSC light curves are used.

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