Nine fixed image extractions give positive infrared color contrasts in two BD+05 4868 Ab cores

We test how detector extraction changes a reported infrared color feature in the known disintegrating planet BD+05 4868 Ab. We read 14,645 calibrated JWST MIRI integrations from two consecutive transit cores. We combine source widths of 8, 12, and 16 columns with left, right, or both background regions. All nine variants use the same valid native samples for each row. A common validity cut keeps 62 rows at 8–10 micrometres and 82 rows at 10–12 micrometres. Fixed phase windows measure a local red-minus-blue log contrast. The nine contrasts range from 808 to 2,118 parts per million (ppm) in core 316 and from 1,101 to 1,388 ppm in core 317. The 12-column source with both background regions gives 1,231 ± 152 ppm and 1,213 ± 90 ppm. Errors are conditional standard deviations from paired residual blocks. At a fixed 12-column source width, left and right backgrounds give 1,792 and 832 ppm in the first core. A linear image check also shows a larger negative color change in the left background of this core. Two-minute bins change individual contrasts by at most 25 ppm. Equal fractional row weights preserve the positive sign. These results establish a positive contrast for the tested extractions and show background sensitivity in the first core. The nine variants share the archive calibration. Residual errors do not bound slow detector response changes, and the nearby stellar companion is not separated. The physical cause remains open. The package contains spectra, code, figures, exact archive byte-range hashes, and offline reproduction checks.

BD+05 4868 Ab · JWST · MIRI · disintegrating planet · infrared transit · background subtraction · extraction sensitivity · reproducible astronomy