Evolutionary Period Changes For 52 Cataclysmic Variables, and the Failure For the Most Fundamental Prediction of the Magnetic Braking Model

TL;DR

This study tests the Magnetic Braking Model's predictions for 52 cataclysmic variables and finds that its core assumptions and predicted period changes are consistently contradicted by observational data, indicating the model's fundamental failure.

Contribution

The paper provides the first comprehensive observational test of the MBM's predicted period changes, revealing significant discrepancies and evidence of unknown mechanisms affecting CV evolution.

Findings

44% of CVs have positive period change, contradicting MBM

Observed period changes are often orders of magnitude more negative than MBM predictions

Large chaotic and sudden period variations are observed, incompatible with MBM

Abstract

The evolution of Cataclysmic Variables (CVs) is driven by period-changes ($\dot{P}$), for which the long-venerable consensus is the Magnetic Braking Model (MBM). The MBM has its only distinctive assumption being a power-law `recipe' describing the angular momentum loss (AML) in the binary, producing a single unique evolutionary track with $\dot{P}$ as a function of the orbital period. This required prediction can be used to test the most-fundamental assumption of MBM, but it has never been tested previously. In this paper, I collect $\dot{P}$ measures for 52 CVs of all types. First, 44 per cent of the CVs have positive-$\dot{P}$, with such being impossible in MBM. Second, even amongst the CVs with negative-$\dot{P}$, their $\dot{P}$ measures are always more-negative than required by MBM, with an average deviation of 110$\times$. Third, three CVs have large chaotic variations in $\dot{P}$ that are impossible for MBM, proving that some unknown mechanism exists and is operating that dominates for these systems. Fourth, the MBM does not account for the long-term effects on evolution arising from the large sudden period decreases seen across many nova events, with this unaccounted effect dominating for the majority of nova systems and changing the sign of the overall evolutionary $\dot{P}$. Fifth, three recurrent novae are observed to suddenly change $\dot{P}$ by an order-of-magnitude across a nova event, with this being impossible in the MBM. In all, the required MBM $\dot{P}$ predictions all fail for my 52 CVs, usually by orders-of-magnitude, so the MBM AML-recipe is wrong by orders-of-magnitude.