BAT and GBM data give a rise to decay spin coefficient ratio of 1.01 with a fixed 6/7 law and frequency random walk noise in the 2020 1A 0535+262 outburst

We tested whether one coefficient relates spin change to hard X-ray rate on both sides of the 2020 giant outburst of 1A 0535+262. We used 30 public Fermi/GBM frequencies and Swift/BAT daily rates. The model integrates the BAT rate to power 6/7. It includes a constant drift and Gaussian random walk noise in frequency. The fitted rise to decay coefficient ratio is 1.0106. Its approximate 95% parametric bootstrap range is 0.937 to 1.092 under these assumptions. Separate coefficients improve twice the log likelihood by 0.073. A fitted-null simulation test gives a tail fraction of 0.803. Assigning the daily BAT values half a day earlier or later changes the ratio to 0.927 or 1.110. The input audit finds 12 positive bright daily bins with flag 3, while their 60 constituent pointings all have flag 0. Statistical-error weighted pointing means reproduce those daily rates to within 6.4 x 10^-8 count per square centimetre per second. A daily flag cut removes peak data and raises the fitted excess noise. These results test a sampled brightness proxy. They do not establish the absence of physical torque hysteresis. We preserve the raw monitor files, source hashes, selected rows, source code, simulations, numerical checks, figures and reproduction instructions.

1A 0535+262 · accreting pulsar · Swift BAT · Fermi GBM · spin change · outburst · rise and decay · data quality · random walk noise