Central Compact Objects: some of them could be spinning up?

TL;DR

This study models the evolution of certain central compact objects (CCOs) with fallback discs, suggesting some may currently be spinning up due to their magnetic and accretion properties, challenging previous assumptions about their spin behavior.

Contribution

It introduces a fallback disc model to explain the rotational and luminosity evolution of CCOs, proposing that some could be in a spin-up phase contrary to typical expectations.

Findings

CCOs can have dipole fields of a few billion Gauss.

Some CCOs may currently be spinning up due to fallback accretion.

Spin-up phase can occur within 10^3 to 10^4 years of evolution.

Abstract

Among confirmed central compact objects (CCOs), only three sources have measured period and period derivatives. We have investigated possible evolutionary paths of these three CCOs in the fallback disc model. The model can account for the individual X-ray luminosities and rotational properties of the sources consistently with their estimated supernova ages. For these sources, reasonable model curves can be obtained with dipole field strengths $\sim$ a few $\times 10^9$ G on the surface of the star. The model curves indicate that these CCOs were in the spin-up state in the early phase of evolution. The spin-down starts, while accretion is going on, at a time $t \sim 10^3 - 10^4$ yr depending on the current accretion rate, period and the magnetic dipole moment of the star. This implies that some of the CCOs with relatively long periods, weak dipole fields and high X-ray luminosities could be strong candidates to show spin-up behavior if they indeed evolve with fallback discs.