BAT exposure midpoints are a median 0.498 day after daily labels in 6,445 matched LMC X-4 bins
We audit daily time labels in public Swift/BAT LMC X-4 tables generated on 21 October 2026. Inverse statistical-variance averages of flag-zero pointings reproduce 6,447 of 6,952 tested daily rates within 5e-8 count cm^-2 s^-1. In 6,445 bins, the summed exposure also agrees within 0.1 second. The weighted exposure midpoint for these bins is a median 0.49794 day after the integer daily label. The 5th to 95th percentile range is 0.21310 to 0.77277 day. We preserve every daily row, including mismatches and two known bad dates. Scientific phase fits exclude those dates from both BAT and MAXI. In 28 four-cycle windows with 2,762 common daily pairs, replacement of BAT labels with weighted midpoints changes the mean soft-minus-hard first-harmonic phase by -0.016529 cycle. Its conditional 95% t interval is [-0.017008, -0.016049]. A Fourier model averaged over uniform pointing intervals differs from the midpoint fit by -0.000039 cycle in the mean. Deterministic common-profile injections recover zero phase with the averaged model and show a mean false phase of +0.016659 cycle with literal labels. Prior SCI work already describes the half-day convention and its approximate phase effect. This contribution adds a complete weighted-time record, joint rate and exposure checks, and a checked interval-averaged design. Matches do not prove identical original selections. The result is limited to these frozen products and the tested phase estimator. The package includes data, source hashes, code, figures, results, and offline repeat instructions.
LMC X-4 · Swift BAT · MAXI · X-ray binaries · time labels · exposure midpoint · daily light curves · Fourier phase · data provenance · reproducible research
References
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 study identified the BAT team notice for MJD 58571 and 58572. We apply those external date exclusions. It already describes the half-day BAT convention and a phase effect near 0.016 cycle. Our added outputs are the per-day weighted-time record, joint rate and exposure audit, and interval-averaged model test.
- supportsDates are one day late in four of six tested Swift/BAT pointing tables for 2023–2025 sci:sha256:8df335c8aba52a813960ed565c10e06026b400e9f6d21ae623aefa7ad652b251
Its six-source audit finds no integer date offset in this LMC X-4 pointing snapshot. Our result measures within-day weighted exposure times in that unaffected control source.
- usesLMC X-4 data from 2024–2026 show no clear cycle phase shift between 4–10 and 15–50 keV when known outburst dates are excluded sci:sha256:6320833d3c5a45725a18d6b8d67aed596cb74187420695d304060b358529b4b1
This prior later-phase test already uses BAT exposure midpoints. We use its five documented nearby outburst dates for retained exploratory later-coverage diagnostics. Our main result is the daily product time audit. No source code or numeric data are copied from that package.
- usesdoi:10.3847/1538-4357/ae4691
We use the fixed period of 30.3187 days and epoch MJD 50075.472. The paper motivates the phase question. Our daily soft proxy and first-harmonic phase differ from its extraction and centroid method. We do not infer how the author handled BAT daily labels.
- usesdoi:10.1088/0067-0049/209/1/14
The Swift/BAT transient monitor supplies the public daily and pointing data. Section 2.1.4 documents weighted UT calendar-day aggregation.
- usesdoi:10.1093/pasj/61.5.999
MAXI supplies the public soft-band daily and orbit-bin data used in the estimator and coverage checks.
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