ACCRETION TORQUES AND MOTION OF THE HOT SPOT ON THE ACCRETING MILLISECOND PULSAR XTE J1807-294
Author(s)Patruno, Alessandro; Wijnands, R.; Chakrabarty, Deepto; van der Klis, Michiel; Hartman, Jacob M., Ph. D. Massachusetts Institute of Technology
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We present a coherent timing analysis of the 2003 outburst of the accreting millisecond pulsar (AMXP) XTE J1807-294. We find a 95% confidence interval for the pulse frequency derivative of (+0.7, + 4.7) × 10⁻¹⁴ Hz s⁻¹ and (-0.6, + 3.8) × 10⁻¹⁴ Hz s⁻¹ for the fundamental and second harmonics, respectively. The sinusoidal fractional amplitudes of the pulsations are the highest observed among AMXPs and can reach values of up to 27% (2.5-30 keV). The pulse arrival time residuals of the fundamental frequency follow a linear anti-correlation with the fractional amplitudes that suggests hot spot motion both in longitude and latitude over the surface of the neutron star. An anti-correlation between residuals and X-ray flux suggests an influence of the accretion rate on pulse phase and casts doubts on the interpretation of pulse frequency derivatives in terms of changes of spin rates and torques on the neutron star.
DepartmentMassachusetts Institute of Technology. Department of Physics; MIT Kavli Institute for Astrophysics and Space Research
American Astronomical Society/IOP Publishing
Patruno, Alessandro et al. “ACCRETION TORQUES AND MOTION OF THE HOT SPOT ON THE ACCRETING MILLISECOND PULSAR XTE J1807-294.” The Astrophysical Journal 717, 2 (June 2010): 1253–1261 © 2010 American Astronomical Society
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