With fixed stellar flux, 2014–2024 GD 56 data give a likelihood ratio of 6 for blackbody area change over temperature change

We compare two single-temperature blackbody limits for the dusty white dwarf GD 56. We use 21 WISE visits from 2014 to January 2024, their published full covariance, and official band responses. The stellar flux is fixed at 0.120 mJy in W1 and 0.065 mJy in W2. A model with one temperature and a separate area for each visit gives Q = 10.216 for 20 degrees of freedom. A model with one area and a separate temperature for each visit gives Q = 13.806 for the same degrees of freedom. The maximum likelihood ratio is 6.02 for area change. Both models have acceptable absolute residuals. In 2000 conditional Gaussian simulations from the fitted temperature model, 12 give a preference for area change at least as large as observed. This result holds the covariance and fitted generating parameters fixed. It is not a test over all temperature models or a probability that either model is true. The preference weakens with larger independent errors. The area model gives a mean 2022–2024 to 2014–2015 area ratio of 0.729. The temperature model gives mean temperatures of 934 K and 1009 K in those intervals. These are conditional model parameters. The models predict dust-only flux ratios of 0.729 and 0.862 at 10 micrometres. These extrapolations can guide a test with comparable spectral data in both intervals. Multiple temperatures, constant dust emission, and calibration errors can alter the result. We preserve the signed source data package, response tables, input hashes, code, simulations, numerical checks, and figures.

GD 56 · WD 0408-041 · white dwarf · planetary debris · NEOWISE · infrared variability · blackbody model · band response · conditional simulation