Optical Studies of 8 AM Herculis-Type Cataclysmic Variable Stars

TL;DR

This study provides detailed observations of eight AM Her-type cataclysmic variables, determining or refining their orbital periods, analyzing their magnetic properties, and identifying two new CVs from Gaia alerts.

Contribution

It reports the first orbital period measurements for several CVs, confirms magnetic characteristics through spectral analysis, and identifies two new CVs from Gaia data.

Findings

Orbital periods range from 81 to 219 minutes.

Spectral features indicate strong magnetic fields in these CVs.

Two Gaia-alert objects are newly classified as CVs.

Abstract

We report detailed follow-up observations of 8 cataclysmic variable stars (CVs) that are apparently AM Her stars, also called polars. For all, we either determine orbital periods for the first time, or improve on existing determinations. The seven for which we have spectra show the high-amplitude radial velocity curves and prominent HeII 4686 emission lines characteristic of strongly magnetic CVs, and their periods, which range from 81 to 219 minutes, are also typical for AM Her stars. Two objects from the Gaia-alerts index, Gaia18aot and Gaia18aya, are newly identified as CVs. Another, RX J0636.3+6554, eclipses deeply, while CSS080228:081210+040352 shows a sharp dip that is apparently a partial eclipse. The spectrum of Gaia18aya has a cyclotron harmonic near 5500 Angstroms that constrains the surface field to about 49 Megagauss or greater.