Discovery and characterization of ZTF J0112+5827: An 80.9-minute polar with strong cyclotron features

TL;DR

This paper reports the discovery of ZTF J0112+5827, a magnetic cataclysmic variable with an 80.9-minute period, characterized by strong cyclotron features and a magnetic field of approximately 39 MG, expanding understanding of polars.

Contribution

The study presents the first detailed characterization of ZTF J0112+5827, including its magnetic field strength, accretion features, and confirmation as a polar system, which was previously unknown.

Findings

ZTF J0112+5827 is an 80.9-minute polar with strong cyclotron features.

The magnetic field strength of the white dwarf is approximately 39 MG.

No accretion disk was detected, only accretion streams.

Abstract

We report the discovery and characterization of ZTF J0112+5827, a new magnetic cataclysmic variable with an orbital period of 80.9 minutes. ROSAT observations revealed X-ray emission with an average flux of $(68.4 \pm 15.7) \times 10^{-14}$ erg s$^{-1}$ cm$^{-2}$ (0.1--2.4 keV). The ZTF light curves show ellipsoidal-like variability in the $g$ band and two prominent humps at phases $\sim$0.0 and $\sim$0.7 in $i$ and $r$ bands. Spectroscopic observations with the Palomar 200-inch telescope revealed cyclotron emission features and strong He II and Balmer emission lines. Doppler tomography shows clear accretion streams with line-of-sight velocities of $\sim$500 km s$^{-1}$, but no accretion disk. Analysis of cyclotron harmonics indicates a magnetic field strength of $38.7^{+1.3}_{-1.1}$ MG, confirming ZTF J0112+5827 as a polar system containing a strongly magnetic white dwarf.