Sudden and Steady Orbital Period Changes Across Six Classical Nova Eruptions; The End of Hibernation and Two Serious Challenges for the Magnetic Braking Model of Cataclysmic Variable Evolution

TL;DR

This study measures orbital period changes in six classical novae, revealing significant deviations from existing models and challenging the validity of the Hibernation and Magnetic Braking models for cataclysmic variable evolution.

Contribution

It provides the first long-term period change measurements for classical novae, showing discrepancies with current theoretical models and emphasizing the need to incorporate $ riangle P$ and $ullet P$ physics.

Findings

Measured $ riangle P/P$ ranges from -290 to +40 ppm, contradicting the Hibernation Model.

Long-term $ullet P$ values are often 5 to 190 times larger than model predictions.

Observed period changes are much larger than magnetic braking effects, challenging existing theories.

Abstract

I report on two new measures of the sudden change in the orbital period ($P$) across the nova eruption ($\Delta$P) and the steady period change in quiescence ($\dot{P}$) for classical novae (CNe) RR Pic and HR Del, bringing a total of six such measures for CNe, all in a final report of my large and long observing program. The fractional changes ($\Delta$P/P) in parts-per-million (ppm) are -290.71$\pm$0.28 (QZ Aur), -472.1$\pm$4.8 (HR Del), -4.46$\pm$0.03 (DQ Her), +39.6$\pm$0.5 (BT Mon), -2003.7$\pm$0.9 (RR Pic), and -273$\pm$61 (V1017 Sgr). These results are in stark opposition to the Hibernation Model for the evolution of cataclysmic variables (CVs), which requires $\Delta$P/P$>$+1000 ppm to get the required drop in the accretion rate to produce hibernation. The Hibernation Model cannot be salvaged in any way. My program has also measured the first long-term $\dot{P}$ for classical novae, with -2.84$\pm$0.22 (QZ Aur), +4.0$\pm$0.9 (HR Del), +0.00$\pm$0.02 (DQ Her), -2.3$\pm$0.1 (BT Mon), and +1.25$\pm$0.01 (RR Pic) in units of $10^{-11}$ days/cycle. These can be directly compared to the predictions of the Magnetic Braking Model, where the long-term average $\dot{P}$ is a single universal function of $P$. The measured values are +5.3, $-$94, 0.00, +6.9, and $-$190 times that predicted by the model, so the predictions are always greatly wrong. Further, the effects of the $\Delta$P averaged over the eruption cycle are usually much larger than the magnetic braking effects. To get a realistic model of CV evolution, we must add the physics of the $\Delta$P and $\dot{P}$ variations.