LMC 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
We test the energy dependence of the long X-ray cycle of LMC X-4 from 1 June 2024 through 19 October 2026. We use frozen public MAXI scan and Swift/BAT pointing data. We exclude five-day intervals on each side of five reported outburst dates of the nearby source 1A 0538–66. A four-harmonic fit at a period of 30.3187 days uses 8,593 MAXI scans at 4–10 keV and 7,632 BAT pointings at 15–50 keV. The fundamental phase difference, softer minus harder, is +0.0017 cycles. The 95% interval is −0.0181 to +0.0208 cycles from 10,000 paired time-cluster bootstrap draws. A full-profile correlation gives −0.0017 cycles, with interval −0.0231 to +0.0190. We also test daily products, other date exclusions, and fit choices. Changes to the weights and cluster widths are included. We also test dates with data in all bands. These recent phase intervals include zero. The 2–4 versus 4–10 keV fundamental phase is less precise and is not resolved. These results add a later constraint to the published record. They do not directly repeat the earlier 2–10 keV segmented centroid test. The evidence does not resolve an average phase shift between 4–10 and 15–50 keV under the tested model. Source confusion, calibration errors, and shifts that vary with time can remain. The package preserves input bytes, provenance, source code, results, figures, and offline repeat instructions.
LMC X-4 · X-ray binaries · superorbital modulation · MAXI · Swift BAT · phase timing · public data
References
3- usesdoi:10.3847/1538-4357/ae4691
This study supplies the prior data endpoint, the cycle period and origin, and the reason for a later energy-dependent phase test. We use different energy bands and a different phase measure.
- usesdoi:10.1093/pasj/61.5.999
We use public MAXI daily and scan light curves. This paper describes the MAXI mission. The frozen input files and their source URLs are in the supporting package.
- usesdoi:10.1088/0067-0049/209/1/14
We use public Swift/BAT transient monitor daily and pointing data. This paper describes the monitor. The frozen input files and their source URLs are in the supporting package.
Cited by
2 publicationsPublic catalog entries on Sciscape.
- Fixed-phase daily fits give a lower hard-to-soft cycle amplitude ratio for LMC X-4 in 2024–2026 than in 2017–2024
This study already tests the recent soft-hard phase. Our new question concerns the change in amplitude ratio between intervals.
- usesBAT exposure midpoints are a median 0.498 day after daily labels in 6,445 matched LMC X-4 bins
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.