Follow-up on three poorly studied AM CVn stars

TL;DR

This study provides detailed observational data and period measurements for three poorly understood AM CVn binary stars, confirming their classification and expanding knowledge of their properties.

Contribution

It offers the first optical spectroscopy for two systems and refines their period measurements, enhancing understanding of these rare binaries.

Findings

Confirmed the classification of two systems as AM CVn stars.

Measured superhump and orbital periods with high precision.

First optical spectroscopy for CRTSJ0910-2008 and NSV1440.

Abstract

We report follow-up observations of three poorly studied AM CVn-type binaries: CRTS CSS150211 J091017-200813, NSV1440, and SDSSJ183131.63+420220.2. Analysing time-series photometry obtained with a range of ground-based facilities as well as with TESS, we determine the superhump period of CRTSJ0910-2008 as P_sh=29.700+-0.004min and the orbital period of NSV1440 as Porb=36.56+-0.03min. We also confirm a photometric period of P=23.026+-0.097min in SDSSJ1831+4202, which is most likely the superhump period. We also report the first optical spectroscopy of CRTSJ0910-2008 and NSV1440 which unambiguously confirms both as AM CVn systems. We briefly discuss the distribution in the Hertzsprung-Russell diagram of the currently known sample of 63 AM CVn stars with known periods and Gaia data.