A fixed orbital phase with 1 day of Gaussian time scatter does not fit 25 selected Cyg X-2 minima in 2017–2026 MAXI data

An earlier study linked deep Cyg X-2 X-ray minima to whole numbers of binary orbits. We apply an explicit minimum rule to public MAXI daily data at 4–10 keV, from MJD 57900.5 to 61316.5. Only 2056 of 3417 days pass the data rule. We select 25 minima. The planned test needs 20 intervals with no gap longer than 5 days. It retains only one interval and cannot support an inference. A separate test, chosen after data inspection, uses all 24 observed adjacent intervals. Missing whole minima preserve integer spacing in a model of fixed orbital phase. The mean cosine of interval phase is −0.041294 at a period of 9.8444 days. Only 3 intervals are within 0.1 cycle of an integer. None of 20000 model draws with independent Gaussian time scatter of 1 day gives a value this low. A comparison with 1999 light curves that preserve the flux distribution and approximately the power spectrum gives a one-sided rank probability of 0.5990. The result is conditional on the selected minima and the timing model. It does not exclude orbital control with phase drift, other time errors, or errors in minimum selection. The package preserves the data, event tables, all checks, figures, code, source records, and reproduction instructions.

Cyg X-2 · MAXI · X-ray binaries · orbital period · time series · minimum times · sampling gaps · surrogate data · reproducible research