Phase-coherent timing of the accreting millisecond pulsar SAX J1748.9-2021

Abstract

We present a phase-coherent timing analysis of the intermittent accreting millisecond pulsar SAX J1748.9-2021. A new timing solution for the pulsar spin period and the Keplerian binary orbital parameters was achieved by phase connecting all episodes of intermittent pulsations visible during the 2001 outburst. We investigate the pulse profile shapes, their energy dependence and the possible influence of Type I X-ray bursts on the time of arrival and fractional amplitude of the pulsations. We find that the timing solution of SAX J1748.9-2021 shows an erratic behavior when selecting different subsets of data, that is related to substantial timing noise in the timing post-fit residuals. The pulse profiles are very sinusoidal and their fractional amplitude increases linearly with energy and no second harmonic is detected. The reason why this pulsar is intermittent is still unknown but we can rule out a one-to-one correspondence between Type I X-ray bursts and the appearance of the pulsations.

arXiv comment22 pages, 7 figures, ApJ accepted. Two figures removed, one typo in the Timing parameters corrected (Table 2)

References in corpus (27)

• TEMPO2, a new pulsar timing package. I: Overview
• Observations of Accreting Pulsars
• Calibration of the Rossi X-ray Timing Explorer Proportional Counter Array
• On the Nature of the X-ray Emission from the Accreting Millisecond Pulsar SAX J1808.4-3658
• Eight New Millisecond Pulsars in NGC 6440 and NGC 6441
• The long-term evolution of the spin, pulse shape, and orbit of the accretion-powered millisecond pulsar SAX J1808.4-3658
• Unstable Disk Accretion to Magnetized Stars: First Global 3D MHD Simulations
• Discovery of coherent millisecond X-ray pulsations in Aql X-1
• Discovery of the accretion-powered millisecond X-ray pulsar IGR J00291+5934
• The atoll source states of 4U 1608-52
• INTEGRAL and RXTE observations of accreting millisecond pulsar IGR J00291+5934 in outburst
• Physics of accretion in the millisecond pulsar XTE J1751-305
• The Amplitude Evolution and Harmonic Content of Millisecond Oscillations in Thermonuclear X-ray Bursts
• Chandra Observation of the Globular Cluster NGC 6440 and the Nature of Cluster X-ray Luminosity Functions
• Absolute Timing of the Crab Pulsar with RXTE
• Discovery of the Millisecond X-Ray Pulsar HETE J1900.1-2455
• Soft Phase Lags of Pulsed Emission from the Millisecond X-ray Pulsar SAX J1808.4-3658
• Timing of the Accreting Millisecond Pulsar XTE J1814-338
• Intermittent pulsations in an accretion-powered millisecond pulsar
• Identification of the optical and quiescent counterparts to the bright X-ray transient in NGC 6440
• Order in the Chaos: Spin-up and Spin-down during the 2002 Outburst of SAX J1808.4-3658
• Spin up and phase fluctuations in the timing of the accreting millisecond pulsar XTE J1807-294
• The Energy Dependence of Millisecond Oscillations in Thermonuclear X-ray Bursts
• Discovery of 442-Hz Pulsations from an X-ray Source in the Globular Cluster NGC 6440
• Energy dependent ~100 μs time lags as observational evidence of Comptonization effects in the neutron star plasma environment
• The energy dependence of burst oscillations from the accreting millisecond pulsar XTE J1814-338
• Discovery of kilohertz quasi-periodic oscillations and state transitions in the low-mass X-ray binary 1E~1724-3045 (Terzan 2)

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