CTCV J2056-3014: An X-ray-faint Intermediate Polar Harboring An Extremely Fast-spinning White Dwarf

TL;DR

This paper reports the discovery of CTCV J2056-3014, an intermediate polar with the fastest-spinning white dwarf, characterized by low X-ray luminosity, modest accretion rate, and implications for magnetic field origins and cataclysmic variable evolution.

Contribution

It presents the first detection of a 29.6s pulsation in an X-ray-faint intermediate polar, identifying the fastest-spinning white dwarf in such systems and discussing its broader astrophysical implications.

Findings

Discovered a 29.6s pulsation in X-rays and optical data.

Identified the system as an X-ray-faint intermediate polar.

White dwarf is the fastest-spinning known in such systems.

Abstract

We report on XMM-Newton X-ray observations that reveal CTCV J2056-3014 to be an unusual accretion-powered, intermediate polar (IP) system. It is a member of the class of X-ray-faint IPs whose space density remains unconstrained but potentially very high, with L$_{x,0.3-12 keV}$ of 1.8$\times$10$^{31}$ erg s$^{-1}$. We discovered a coherent 29.6s pulsation in X-rays that was also revealed in our reanalysis of published optical data, showing that the system harbors the fastest-spinning, securely known white dwarf (WD) so far. There is no substantial X-ray absorption in the system. Accretion occurs at a modest rate ($\sim$ 6$\times$10$^{-12}$ M$_{\odot}$ yr$^{-1}$) in a tall shock above the WD, while the star seems to be spinning in equilibrium and to have low magnetic fields. Further studies of CTCV J2056-3014 potentially have broad implications on the origin of magnetic fields in WDs, on the population and evolution of magnetic cataclysmic variables, and also on the physics of matter around rapidly rotating magnetic WDs.