2023MNRAS.525..785S

The evolution of novae and cataclysmic variables (CVs) is driven by changes in the binary orbital periods. In a direct and critical test for various evolution models and their physical mechanisms, I measure the sudden changes in the period (ΔP) across 14 nova eruptions, and I measure the steady period change during quiescence (Ṗ) for 20 inter-eruption intervals. The standard theory for ΔP is dominated by the mechanism of mass loss, and this fails completely for the five novae with negative values, and it fails to permit the ΔP for U Sco eruptions to change by one order of magnitude eruption to eruption. The Hibernation Model of evolution is refuted because all the ΔP measures are orders of magnitude too small to cause any significant drop in accretion luminosity, and indeed, near half of the nova have negative ΔP as the opposite of the required mechanism for any hibernation state. As for the Magnetic Braking Model, this fails by many orders of magnitude in its predictions of the required Ṗ for 9 out of 13 novae. The observed Ṗ values scatter, both positively and negatively, over a range of ±10^–9, while the predicted values are from -10^–13 to -10^–11. This huge scatter is not possible with standard theory, and there must be some currently unknown mechanism to be added in, with this new mechanism 100-10 000× larger in effect than the current theory allows. In all, these failed predictions demonstrate that nova systems must have unknown physical mechanisms for both ΔP and Ṗ that dominate over all other effects.