Nine fits give an 8.7 minute range for the Cen X-3 eclipse midpoint in 2021–2026 BAT data

We measured eclipse midpoints for Cen X-3 in public Swift/BAT 15–50 keV data from 2021–2026. We kept the Table 3 orbital clock of Klawin et al. (2023) fixed. Nine specified fits gave midpoint residuals from −968 to −445 s, a range of 523 s, or 8.7 minutes. This is a range of point estimates, not a confidence interval. The benchmark fit used independent linear edges and integrated each exposure. It added an error floor of 0.01 count cm⁻² s⁻¹. Its residual was −900 s with a conditional 95% interval of [−1693, −464] s. We used 240 draws of 64-cycle blocks. The 2012–2020 reference fit gave −199 s and [−372, −69] s. The later ingress moved more than egress in this model. Nearly equal weights gave −445 s and [−1424, +406] s. A paired interval for the weight change included zero. These results do not establish a new change in the orbit or a resolved weight effect. The intervals condition on the observed sampling and fixed clock. The package preserves the data snapshot, code, provenance, fit tables, bootstrap samples, figures, and reproduction instructions.

Cen X-3 · Swift BAT · eclipse timing · orbital ephemeris · X-ray binary · block bootstrap · reproducible data