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Table 1

Results of evidence-based model comparison.

Model Number of No decisive No decisive No decisive No decisive Max
model parameters evidence against evidence against evidence against evidence against evidence
it at 3σ it at 5σ it at 7σ it at 10σ

Constant 1 0 0 0 0 0
Constant plus noise 2 59 64 73 94 4
Sinusoid (flat prior in P) 4 28 37 46 58 2
Sinusoid (flat prior in log P) 4 20 23 29 39 2
Sinusoid (periodogram prior) 4 27 30 39 50 4
Two sinusoids (flat priors in P) 7 33 36 45 60 7
Sinusoid (flat prior in P) plus noise 5 467 583 721 921 149

Wiener process (random walk) 2 2205 2724 3230 3949 11
OU process (damped random walk) 3 6023 6069 6093 6131 5047
Gaussian CAR(2) process (φ1 = φ2 = 0.1) 2 0 0 0 1 0
Gaussian CAR(2) process (τ1 = τ2) 3 1 2 2 3 0
Gaussian CAR(2) process (τ1 ≠ τ2) 4 5 5 5 5 5
Cauchy CAR(1) process (φ = 1) 2 81 108 172 361 36
Symmetric stable CAR(1) process (φ = 1, β = 0) 3 0 0 0 0 0
Stable CAR(1) process (φ = 1) 4 0 0 0 0 0
Gaussian CARMA(1, 1) process 4 0 0 0 0 0

Constant + Gaussian ARCH(1) process 3 236 268 306 355 69
Sinusoid + Gaussian ARCH(1) process 6 923 1208 1529 2096 155
Gaussian CAR(1)-ARCH(1) process 4 1884 2257 2639 3183 219
Gaussian CAR(1)-GARCH(1, 1) process 5 3542 3912 4285 4751 536
Gaussian CARMA(1, 1)-GARCH(1, 1) process 6 1533 2041 2593 3486 58

Notes.For each model under consideration we quote the number of model parameters, the number of QSO lightcurves where there is no decisive evidence against this model at a specified confidence level, and the number of QSO lightcurves where each model provides the highest evidence. The upper block of the table contains deterministic models. The middle block contains stochastic models with constant variance, while the lower block contains stochastic process with stochastic variance. (Periods of all sinusoids are between 1 and 10 000 days.) The last column adds up to the total of 6304 QSO lightcurves, the other columns do not.

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