The difference amplitude is 15 to 20 times the sum amplitude in fixed-frequency fits to 2021 TESS data for TT Ari

TT Ari has two known superhump signals and a strong signal near their difference frequency. We test whether an instantaneous product of two fixed sinusoids can account for the fitted low component. A real product requires equal sum and difference amplitudes. We fit 26,831 quality-zero samples from the 120-second TESS SPOC light curves in sectors 42 and 43. The parent frequencies are fixed at 7.5233 and 6.6200 cycles/day. The difference and sum semi-amplitudes are 2.724% and 0.179% of median flux in sector 42, and 2.309% and 0.117% in sector 43. Their ratios are 15.23 and 19.77. Planned processing controls give ratios from 13.53 to 19.86. Block sign checks depend on the error model. The largest fitted-null tail fractions are 0.0078125 and 0.005127 with planned 0.5 to 2-day blocks. They rise to 0.0625 and 0.03125 with four-day blocks. Artificial data show that nominal interval coverage is imperfect. Thus, the measured coherent components do not meet the equal-amplitude condition for a constant instantaneous scalar cross term. This result does not exclude disk precession, a separate low-frequency contribution, cancellation, or coupling that changes with time or frequency. The signals were already known. This work adds a quantitative necessary-condition test and its error audit. The package includes native data, archive hashes, code, tables, figures, and offline reproduction instructions.

TT Arietis · TESS · cataclysmic variables · superhumps · frequency mixing · block resampling · reproducible astronomy