We present the spectral and timing analysis of the X-ray pulsar GRO J1744-28 during its 2014 outburst using data collected with the X-ray satellites Swift, INTEGRAL, Chandra, and XMM-Newton. We derived, by phase-connected timing analysis of the observed pulses, an updated set of the source ephemeris. We were also able to investigate the spin-up of the X-ray pulsar as a consequence of the accretion torque during the outburst. Relating the spin-up rate and the mass accretion rate as nu proportional to M-beta, we fitted the pulse phase delays obtaining a value of beta = 0.96(3). Combining the results from the source spin-up frequency derivative and the flux estimation, we constrained the source distance to be between 3.4 and 4.1 kpc, assuming a disc viscous parameter a to be in the range of 0.1-1. Finally, we investigated the presence of a possible spin-down torque by adding a quadratic component to the pulse phase delay model. The marginal statistical improvement of the updated model does not allow us to firmly confirm the presence of this component.
|Numero di pagine||11|
|Rivista||Monthly Notices of the Royal Astronomical Society|
|Stato di pubblicazione||Published - 2017|
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