Time-resolved optical photometry of the ultra-compact binary 4U0614+091

TL;DR

This study uses time-resolved optical photometry to detect and analyze variable modulations in the ultra-compact X-ray binary 4U0614+091, revealing multiple periodic signals possibly related to orbital or accretion phenomena.

Contribution

First detailed optical variability analysis of 4U0614+091 using extensive multi-telescope data, identifying multiple transient periodic modulations.

Findings

Detected sinusoidal modulations with periods of 51.3, 42, and 64 minutes.

The strongest modulation at 51.3 mins may be related to the orbital period.

Modulations likely caused by X-ray irradiation, superhumps, or accretion disc activity.

Abstract

We present a detailed optical study of the ultra-compact X-ray binary 4U0614+091. We have used 63 hrs of time-resolved optical photometry taken with three different telescopes (IAC80, NOT and SPM) to search for optical modulations. The power spectra of each dataset reveals sinusoidal modulations with different periods, which are not always present. The strongest modulation has a period of 51.3 mins, a semi-amplitude of 4.6 mmags, and is present in the IAC80 data. The SPM and NOT data show periods of 42 mins and 64 mins respectively, but with much weaker amplitudes, 2.6 mags and 1.3 mmags respectively. These modulations arise from either X-ray irradiation of the inner face of the secondary star and/or a superhump modulation from the accretion disc, or quasi-periodic modulations in the accretion disc. It is unclear whether these periods/quasi-periodic modulations are related to the orbital period, however, the strongest period of 51.3 mins is close to earlier tentative orbital periods. Further observations taken over a long base-line are encouraged.