Orbital Period Changes for Fourteen Novae and the Critical Failures of the Predictions of Standard Theories, the Hibernation Model, and the Magnetic Braking Model

TL;DR

This study measures orbital period changes in 14 novae and finds that existing theories like the standard, hibernation, and magnetic braking models fail to accurately predict these changes, indicating unknown mechanisms are at play.

Contribution

It provides the first comprehensive observational test revealing the failures of current models in explaining nova orbital period variations.

Findings

Standard theory fails for novae with negative $\Delta P$.

Hibernation model is refuted due to insufficient $\Delta P$.

Magnetic braking model predictions are off by orders of magnitude.

Abstract

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 ($\Delta P$) across 14 nova eruptions and I measure the steady period change during quiescence ($\dot{P}$) for 20 inter-eruption intervals. The standard theory for $\Delta P$ 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 $\Delta P$ for U Sco eruptions to change by one order-of-magnitude from eruption-to-eruption. The Hibernation Model of evolution is refuted because all the $\Delta P$ measures are orders of magnitude too small to cause any significant drop in accretion luminosity, and indeed, near half of the nova have negative $\Delta P$ 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 $\dot{P}$ for 9-out-of-13 novae. The observed $\dot{P}$ values scatter, both positively and negatively, over a range of $\pm$10$^{-9}$, while the predicted values are from $-$10$^{-13}$ to $-$10$^{-11}$. This huge scatter is not possible with standard theory, and there must be some currently-unknown mechanism to be added in, with this new mechanism 100--10000$\times$ larger in effect than the current theory allows. In all, these failed predictions demonstrate that nova systems must have unknown physical mechanisms for both $\Delta P$ and $\dot{P}$ that dominate over all other effects.