XTE J2123-058: A New Neutron Star X-Ray Transient

Abstract

We report on optical and RXTE observations of a new high-latitude bursting X-ray transient, XTE J2123-058. We identified the optical counterpart, measured the 5.9573 hr orbital period and constrained the binary inclination and the source distance. The distance lower limit indicates that the source is at least 2.6 kpc from the Galactic plane, which is unusual for an LMXB. RXTE observations were made between June and August 1998 during the first detected outburst from this source. We describe correlations between X-ray timing and spectral properties and discuss the possibility that the propeller mechanism turned on during the decay of the outburst. During one of the RXTE observations, we detect a pair of high frequency QPOs at 847.1 +/- 5.5 Hz and 1102 +/- 13 Hz simultaneously. According to the beat frequency model, the QPO separation implies a neutron star spin period near 3.9 ms. As the X-ray flux decreases at the end of the outburst, the amplitude of the optical modulation increases significantly. This behavior can be explained if the size of the accretion disk decreases during the decay of the outburst.

arXiv comment24 pages, 9 figures, accepted by ApJ

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• Detecting gravitational wave emission from the known accreting neutron stars
• Study of measured pulsar masses and their possible conclusions
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• The gas-to-extinction ratio and the gas distribution in the Galaxy
• Optical and X-ray observations of the neutron star soft X-ray transient XTE J1709-267
• Discovery of a Cosmological, Relativistic Outburst via its Rapidly Fading Optical Emission
• Modelling the spin equilibrium of neutron stars in LMXBs without gravitational radiation
• Simultaneous Measurements of X-Ray Luminosity and Kilohertz Quasi-Periodic Oscillations in Low-Mass X-Ray Binaries
• The Low Quiescent X-Ray Luminosity of the Neutron Star Transient XTE J2123-058
• VLT spectroscopy of XTE J2123-058 during quiescence
• Optical studies of the X-ray transient XTE J2123-058 - II. Phase-resolved spectroscopy
• Optical studies of the X-ray transient XTE J2123-058 -I. Photometry
• Investigation of the emission radii of kHz QPOs for the accreting millisecond X-Ray pulsars, Atoll and Z sources
• Rotational Broadening Measurement for the Neutron Star X-Ray Transient XTE J2123-058
• Statistical properties of twin kHz QPO in neutron star LMXBs
• The relation between outburst rate and orbital period in low-mass X-ray binary transients
• Keck Measurement of the XTE J2123-058 Radial Velocity Curve
• Discovery of twin kHz quasi periodic oscillations in the low mass X-ray binary XTE J1701-407