Precise determination of orbital parameters in system with slowly drifting phases: application to the case of XTE J1807-294

Abstract

We describe a timing technique that allows to obtain precise orbital parameters of an accreting millisecond pulsar in those cases in which intrinsic variations of the phase delays (caused e.g. by proper variation of the spin frequency) with characteristic timescale longer than the orbital period do not allow to fit the orbital parameters over a long observation (tens of days). We show under which conditions this method can be applied and show the results obtained applying this method to the 2003 outburst observed by RXTE of the accreting millisecond pulsar XTE J1807-294 which shows in its phase delays a non-negligible erratic behavior. We refined the orbital parameters of XTE J1807-294 using all the 90 days in which the pulsation is strongly detected and the method applicable. In this way we obtain the orbital parameters of the source with a precision more than one order of magnitude better than the previous available orbital solution, a precision obtained to date, on accreting millisecond pulsars, only for XTE J1807-294 analyzing several outbursts spanning over seven years and with a much better statistics.

14 pages, including 6 figures. Submitted to MNRAS. Accepted 2007 September 12. Received 2007 September 12; in original form 2007 February 22

References in corpus (9)

• The two-hour orbit of a binary millisecond X-ray pulsar
• INTEGRAL spectroscopy of the accreting millisecond pulsar XTE J1807-294 in outburst
• Timing of the Accreting Millisecond Pulsar XTE J1814-338
• Discovery of kHz QPOs and shifted frequency correlations in the accreting millisecond pulsar XTE J1807--294
• Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658
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• Timing an Accreting Millisecond Pulsar: Measuring the Accretion Torque in IGR J00291+5934
• XMM-Newton observation of the 5.25 ms transient millisecond pulsar XTE J1807-294 in outburst
• Studies of orbital parameters and pulse profile of the accreting millisecond pulsar XTE J1807-294

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• Accretion torques and motion of the hot spot on the accreting millisecond pulsar XTE J1807-294
• Black Holes in Short Period X-ray Binaries and the Transition to Radiatively Inefficient Accretion
• Spectral and timing properties of IGR J00291+5934 during its 2015 outburst
• Timing of the accreting millisecond pulsar IGR~J17511--3057
• Close-in Exoplanets as Candidates of Strange Quark Matter Objects