The noise model changes the tail rate of the 2014–2024 ID8 W2 period peak

We test the long period peak of the warm debris disk NGC 2547 ID8 in public NEOWISE W2 data. Quality cuts leave 526 exposures in 21 visits from 2014 to 2024. An equal-weight sine search over 365–2000 days gives maximum power 0.72658 near 983 days. A denser grid places the peak near 981 days. We simulate stationary, nonperiodic Gaussian noise at the observed times and repeat the full search. Each covariance grid point uses 100,000 simulations. Intrinsic amplitude is fitted by restricted likelihood at each fixed covariance scale. The conditional tail rate is 0.024% for independent noise. It is 0.531% for exponential noise with a 300-day scale. An exploratory Matérn-3/2 model at the same scale gives 2.563%, with a 95% Monte Carlo interval of 2.466–2.663%. This smoother model also gives a higher restricted likelihood than independent noise. Stricter and looser photometry cuts give Matérn 300-day tail rates of 2.437% and 2.683%. Removing one visit at a time preserves a peak between 972 and 994 days. Thus, the timescale persists, but a tail rate below 1% does not hold across the tested noise models. These rates hold fitted covariance parameters fixed. They do not include uncertainty in the noise law or test the full multi-instrument recurrence record. The package preserves the archive response, provenance, code, seeds, simulation maxima, checks, and figures. This edition corrects the UTC retrieval date. The numerical results are unchanged.

NGC 2547 ID8 · NEOWISE · debris disks · infrared variability · periodogram · correlated noise · Gaussian process · Monte Carlo