Spectroscopy of the Proposed White Dwarf Pulsar ASASSN-V J205543.90+240033.5

TL;DR

This study presents spectral observations of the candidate white dwarf pulsar J2055, revealing a binary system with emission lines and uncertain origin of its 10-minute photometric variability, suggesting complex stellar interactions.

Contribution

First spectral analysis of J2055 confirming its binary nature and providing insights into its stellar components and variability.

Findings

Spectra show emission lines and a blue continuum.

Binary nature confirmed by velocity variations.

Uncertain origin of 10-minute photometric variation.

Abstract

We obtained spectra of ASASSN-V J205543.90+240033.5 (J2055), a system that shows photometric variations similar to the white dwarf (WD) pulsar AR Scorpii (Kato et al. arXiv:2109.03979). Our spectra display a continuum rising steeply toward the blue as well as an array of emission lines. Resolved Balmer and Paschen lines are seen with H$\alpha$ and H$\beta$ having central absorption features. The strongest lines are unresolved CII, CIII, and NIII as well as doubly ionized helium. The spectra are similar to that of YY Hya (Kimeswenger et al. arXiv:2110.03935), and suggest that J2055 is a post-common envelope binary consisting of a hot compact star irradiating the face of a secondary of unknown spectral type. Velocity variations detected from the emission lines confirm the binary nature of J2055. The origin of the 10 minute photometric variation remains uncertain.