Evolution of Spin in the Intermediate Polar CC Sculptoris

TL;DR

This paper studies the spin period variations of the intermediate polar CC Scl using TESS data, revealing a consistent spin-up trend, shape changes over years, and potential links to accretion and dwarf nova eruptions.

Contribution

It provides the first detailed analysis of CC Scl's spin evolution, combining observational data with theoretical spin profiles and suggesting accretion-driven spin changes.

Findings

Spin period has decreased by about 0.02 seconds since 2011.

The spin variation rate aligns with other intermediate polars.

The spin profile has changed shape over three years.

Abstract

We report on spin variations in the intermediate polar and cataclysmic variable CC Scl, as seen by the Transiting Exoplanet Survey Satellite (TESS). By studying both the spin period and its harmonic, we find that the spin has varied since it was first observed in 2011. We find the latest spin value for the source to be 389.473(6)s, equivalent to 0.00450779(7) days, 0.02s shorter than the first value measured. A linear fit to these and intermediate data give a rate of change of spin ~-4.26(2.66)e10^-11 and a characteristic timescale tau~2.90e10^5 years, in line with other known intermediate polars with varying spin. The spin profile of this source also matches theoretical spin profiles of high-inclination intermediate polars, and furthermore, appears to have changed in shape over a period of three years. Such `spin-up' in an intermediate polar is considered to be from mass accretion onto the white dwarf (the primary), and we note the presence of dwarf nova eruptions in this source as being a possible catalyst of the variations.