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

LMC X-4 profiles stay early in the tested 2024–2025 BAT and MAXI data under a fixed phase model

We find that the early brightness phase of LMC X-4 continues in 2024–2025. LMC X-4 is a neutron-star binary. We use a fixed 8900-day phase model from Chou (2026) and a separate earlier profile for each instrument. The earlier data cover Modified Julian Date (MJD) 57900–60462. The later data cover MJD 60462–60947.10, before a reported nearby X-ray outburst. The 451 Swift BAT days give a profile shift of -0.0572 cycle, or -1.73 days. The 370 MAXI days give -0.0426 cycle, or -1.29 days. Negative shifts mean earlier profiles. Joint resampling of earlier and later two-cycle blocks gives 95% intervals of -0.0711 to -0.0418 cycle for BAT and -0.0537 to -0.0305 cycle for MAXI. All four later segments have negative shifts in each instrument. The preceding 16-cycle interval also has negative shifts. This is a continuation, rather than evidence for a new phase transition. Harmonic, training-window, and equal-weight checks keep this direction. A noise floor limits the effect of two earlier BAT days with very small listed errors. These are profile shifts for fixed model parameters. Known phase variation and profile changes prevent a physical clock or cause from being selected. We supply the data snapshot, phase tables, figures, source code, provenance, and offline reproduction steps.

LMC X-4 · X-ray binaries · superorbital phase · Swift BAT · MAXI · time series · reproducible research

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References

5
  1. usesdoi:10.3847/1538-4357/ae4691

    We test later data with the fixed sinusoidal phase coefficients in arXiv:2602.13491v1, Table 1. Its light curves end at MJD 60461.

  2. usesdoi:10.48550/arXiv.2602.13491

    This is the version-specific source of the numerical phase function. We inspected version 1.

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

    This paper describes the public Swift BAT transient monitor used here.

  4. usesdoi:10.1093/pasj/61.5.999

    This paper describes the MAXI mission. We use its public standard daily 4–10 keV data.

  5. A fixed 167.43-day clock gives lower 2023–2026 MAXI errors for 4U 1820-30 than the published clock with a period decrease when early Fourier profiles are fixed sci:sha256:0b06b08040dfbc08e8f4cad6c78a13db48332bbbeac5b28b98952625db4d1e52

    This related X-ray clock study discusses fitting weight concentration. We independently check that issue in LMC X-4.

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