Eclipse timings of the LMXB XTE J1710-281: orbital period glitches

Abstract

We present an X-ray eclipse timing analysis of the transient low mass X-ray binary XTE J1710-281. We report observations of 57 complete X-ray eclipses, spread over more than a decade of observations, made with the proportional counter array detectors aboard the RXTE satellite. Using the eclipse timing technique, we have derived a constant orbital period of 0.136 710 9674 (3) d, during the period from MJD 52132 up to MJD 54410, and 1σ limits of −1.6 × 10−12 and 0.2 × 10−12 d d−1, on the period derivative, inline image. This puts constraints on the minimum time-scale of secular orbital period evolution (inline image) of 2.34 × 108 yr for a period decay and 18.7 × 108 yr for a period increase. We also report detection of two instances of discontinuity in the mid-eclipse time, one before and one after the above MJD range. These results are interpreted as three distinct epochs of orbital period in XTE J1710-281. We have put lower limits of 1.4 and 0.9 ms on orbital period change (ΔPorb) at successive epochs. The detection significance of the two orbital period glitches are 11σ and 4σ, respectively. The sudden changes in orbital period is very similar in nature to that observed in EXO 0748-676, though their magnitude is much smaller in XTE J1710–281.