2007/10/31 by A. Riggio, T. Di Salvo, L. Burderi +5 · 2 citations
Physics and Astronomy · #Astronomy and Astrophysical Research #Astrophysical Phenomena and Observations #Harmonic #Millisecond #Millisecond pulsar #Phase (matter) #Position (finance) #Pulsar #Pulsars and Gravitational Waves Research #Pulse (music) #Spin (aerodynamics) #astro-ph
paper · pdf · doi:10.1086/533578
17 pages, 4 figures, Accepted by ApJ
arxiv created 2008/01/21 · openalex publication_date 2008/04/30 · arxiv updated 2009/12/01 · openalex created_date 2016/06/24 · openalex updated_date 2026/08/05
We have performed a timing analysis of the 2003 outburst of the accreting X-ray millisecond pulsar XTE J1807–294 as observed by the Rossi X-Ray Timing Explorer . Using recently refined orbital parameters, we report for the first time a precise estimate of the spin frequency and of the spin frequency derivative. The phase delays of the pulse profile show a strong erratic behavior superposed on what appears to be a global spin-up trend. The erratic behavior of the pulse phases is strongly related to rapid variations of the light curve, making it very difficult to fit these phase delays with a simple formula. As in previous cases, we therefore separately analyze the phase delays of the first harmonic and of the second harmonic of the spin frequency, finding that the phases of the second harmonic are far less affected by the erratic behavior. Under the hypothesis that the second-harmonic pulse phase delays are a good tracer of the spin frequency evolution, we give for the first time an estimate of the spin frequency derivative for this source. XTE J1807–294 shows a clear spin-up of = 2.5(7) × 10 −14 Hz s −1 (1 σ confidence level). The majority of the uncertainty in the value of the spin-up rate is due to the uncertainties in the source position on the sky. We discuss the effect of this systematic error on the spin frequency and its derivative.