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B.D. Johnson (UCLA/CTIO), S. Wachter (CTIO)
We present extensive new photometry of the low mass X-ray binary (LMXB) X0614+091. Discovered in 1974, its X-ray properties have only recently identified it as a member of the so-called Atoll sources. Atoll sources are thought to have main sequence mass donors and relatively short (< 8 hours) orbital periods. Early observations of the faint (V=18.5) optical counterpart revealed an unusual spectrum that only showed the NIII/CIII 4640/50 emission complex. LMXB spectra usually also exhibit HeII 4686 emission. Previous variability searches detected a 5.2 day modulation in X-rays and a ~10 day periodicity in the optical. If either one of these modulations reflects the orbital period, mass transfer via Roche lobe overflow would require a giant secondary, inconsistent with the observed optical properties of the source. An alternative cause for the variations is precession of the accretion disk in the system.
We obtained V band observations of X0614 with the queue scheduled YALO telescope at CTIO between UT 1999 Dec 10 and 2000 Jan 31 in order to confirm the reported ~10 day variability and search for an orbital period. Comparison with RXTE ASM data reveals that some of the optical observations occurred during a rare state of decreased X-ray variability of the source. We will report on the results of the period analysis and the correlation between optical and X-ray data for X0614+091.
This research was carried out as part of the 2000 Research Experiences for Undergraduates Program at CTIO, funded by the National Science Foundation.