Two 2019 notice dates hold over half the quoted weight in 29 of 94 BAT files labelled HMXB for 2012–2026

We measure how two dates named in a Swift/BAT data notice affect quoted statistical weight across a fixed public source list. We select all 94 monitor-index rows whose Source Type contains HMXB and preserve all daily files. For accepted rows from 2012 January 1 through 2026 October 20, MJD 58571 and 58572 contain at least 10% of the inverse-ERROR-squared weight in 66 files and more than half in 29 files. The maximum share is 88.09%. All 177 supplied notice-date rows pass the finite-value, positive-error, flag-zero, and positive-exposure cuts. None has an exactly zero rate. The median notice error divided by the median error on other accepted days is 0.02359. Five files have no notice-date rows and remain in the denominator. Dropping the exposure cut changes no result. With the full delivered history, 20 files retain more than half their weight on the two dates. We report every file, every notice row, and the change in weighted and unweighted means. These are deterministic archive properties. They extend earlier individual-source checks but do not establish the physical cause of each row or certify other dates. The package preserves exact compressed inputs, provenance, original code, figures, an independent numerical check, and an explicit screening tool.

Swift BAT · data quality · X-ray binaries · inverse variance · reproducibility · public astronomy data