Confirmation of 1RXS J165443.5-191620 as an intermediate polar and its orbital and spin periods

TL;DR

This study confirms 1RXS J165443.5-191620 as an intermediate polar, identifying its orbital period of 3.7 hours and white dwarf spin period of 546 seconds through optical photometry and spectroscopy, contributing to understanding of magnetic cataclysmic variables.

Contribution

First comprehensive optical photometry and spectroscopy confirming the intermediate polar nature and precise periods of 1RXS J165443.5-191620.

Findings

Confirmed intermediate polar with 546s spin period

Orbital period of 3.7 hours established

Displays characteristic modulations of magnetic CVs

Abstract

Aims: We investigate the physical nature of the X-ray emitting source 1RXS J165443.5-191620 through optical photometry and time-resolved spectroscopy. Methods: Optical photometry is obtained from a variety of telescopes all over the world spanning about 27 days. Additionally, time-resolved spectroscopy is obtained from the MDM observatory. Results: The optical photometry clearly displays modulations consistent with those observed in magnetic cataclysmic variables: a low-frequency signal interpreted as the orbital period, a high-frequency signal interpreted as the white dwarf spin period, and an orbital sideband modulation. Our findings and interpretations are further confirmed through optical, time-resolved, spectroscopy that displays H-alpha radial velocity shifts modulated on the binary orbital period. Conclusion: We confirm the true nature of 1RXS J165443.5-191620 as an intermediate polar with a spin period of 546 seconds and an orbital period of 3.7 hours. In particular, 1RXS J165443.5-191620 is part of a growing subset of intermediate polars, all displaying hard X-ray emission above 15keV, white dwarf spin periods below 30 minutes, and spin-to-orbital ratios below 0.1.