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

The selected 2012–2026 BAT sample shows a larger relative pre-eclipse loss in faint SMC X-1 intervals under a 120-day block model

Does the hard X-ray loss before eclipse change with the brightness of SMC X-1? We test 42,629 selected Swift/BAT pointings from 2012–2026. A separate MAXI 4–10 keV curve sets the brightness labels. Fixed thresholds use only 2012–2018 data. We divide each BAT pre-minus-post rate by its state reference rate. The faint-minus-bright difference is −0.2223. Paired resampling of 120-day calendar blocks gives a conditional 95% interval of [−0.3896, −0.0486]. This result conditions on the measured labels and the block model. The roll-dither sample gives −0.0868 [−0.3854, +0.1926]. A test with complete state-orbit cells gives −0.2367 [−0.6556, +0.2220]. All three eclipse mean rate intervals include zero. Prior work already showed brightness-dependent BAT orbital profiles. We add a recent fixed contrast and a record of its limits. The full sample supports an association. The restricted tests do not resolve the signal or establish a physical cause. The package contains frozen source data, hashes, a row selection record, code, figures, and independent numerical checks. A separate offline run reproduces all saved numerical outputs.

SMC X-1 · Swift BAT · MAXI · X-ray binaries · orbital profiles · pre-eclipse dip · block bootstrap · reproducible astronomy

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References

10
  1. doi:10.1086/305893

    This study measured large changes outside eclipse and smaller changes in eclipse spectra of SMC X-1.

  2. doi:10.1086/522075

    This study examined the orbital and longer-period flux structure of SMC X-1.

  3. doi:10.1088/0004-637X/773/1/58

    This study reported a dip at orbital phase 0.6–0.85 and changes in its width.

  4. doi:10.3847/1538-4357/ab48e4

    Section 3.3 and Figure 9 already show brightness-dependent BAT and MAXI orbital profiles. They report higher post-eclipse than pre-eclipse flux in several states. Our contribution is an updated fixed contrast and its tests.

  5. usesdoi:10.48550/arXiv.2511.05016

    We use the numerical orbital clock in Section III.2 of version 1. We do not fit a new clock.

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

    This paper describes the Swift/BAT transient monitor that supplies the hard X-ray data.

  7. doi:10.1093/pasj/61.5.999

    This paper describes MAXI, which supplies the separate brightness measure.

  8. Tests with cycle blocks do not reject proportional MAXI curves in three SMC X-1 time ranges from 2012 to 2025 sci:sha256:b6e88b9503db48bc0e853b20c92bfc32c7cb9f869a72bb312ed78d7d07f0c7ea

    This related study tests proportional MAXI curves over the longer cycle. Our test compares fixed orbital windows in BAT data.

  9. Dates are one day late in four of six tested Swift/BAT pointing tables for 2023–2025 sci:sha256:8df335c8aba52a813960ed565c10e06026b400e9f6d21ae623aefa7ad652b251

    This BAT timing audit motivated a check of FITS and ASCII values. SMC X-1 was an unaffected control. We find agreement to the ASCII precision.

  10. MAXI scans from 2023–2026 do not resolve extra soft attenuation in the SMC X-1 pre-eclipse dip under a paired reference sci:sha256:7b721c6a7fe7ab5820d2e998a4a3900732b266090b55a18278f0cbdc6de3edd2

    This related study tests dip energy dependence in recent MAXI scans with local paired references. Our long-baseline BAT contrast uses different reference windows.

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