Re-analysis of the SPI-ACS data excising the brightest part of the GRB (i.e. BTI), which is affected by data loss in Fermi/GBM. In the left and middle panel, we show observations in black, the maximum a posteriori combined model in blue, and draws from the posterior probability density for the mean function in orange. The left-most panel shows the results for ℳ₁ (skew-Gaussian mean function and DRW), the middle panel for ℳ₂ (skew-Gaussian mean function, DRW and QPO). In the right-hand panel, we show the posterior probability density for the period of the QPO, which is narrowly constrained around P = 0.347 s.