On the nature of CP Pup

TL;DR

This study presents new X-ray and optical observations of the old nova CP Pup, providing evidence supporting its classification as an intermediate polar type magnetic cataclysmic variable.

Contribution

The paper offers new multi-wavelength spectra and analysis that reinforce the classification of CP Pup as an intermediate polar mCV, highlighting its complex plasma and periodic behaviors.

Findings

X-ray spectrum shows multi-temperature plasma up to 36 keV.

Optical spectra confirm a ~1.47 hr period with cycle-to-cycle variations.

Evidence suggests CP Pup is likely an intermediate polar mCV.

Abstract

We present new X-ray and optical spectra of the old nova CP Pup (nova Pup 1942) obtained with Chandra and the CTIO 4m telescope. The X-ray spectrum reveals a multi-temperature optically thin plasma reaching a maximum temperature of 36$^{+19}_{-16}$ keV absorbed by local complex neutral material. The time resolved optical spectroscopy confirms the presence of the $\sim$1.47 hr period, with cycle-to-cycle amplitude changes, as well as of an additional long term modulation which is suggestive either of a longer period or of non-Keplerian velocities in the emission line regions. These new observational facts add further support to CP Pup as a magnetic cataclysmic variable (mCV). We compare the mCV and the non-mCV scenarios and while we cannot conclude whether CP Pup is a long period system, all observational evidences point at an intermediate polar (IP) type CV.