2005/02/15 by Alessandro Papitto, A. Papitto, M. T. Menna +5 · 1 citation
Earth and Planetary Sciences · Physics and Astronomy · #Astronomy #Astrophysical Phenomena and Observations #Astrophysics #Computer science #Epoch (astronomy) #High-pressure geophysics and materials #Magnitude (astronomy) #Millisecond #Millisecond pulsar #Optics #Orb (optics) #Orbital elements #Orbital period #Physics #Pulsar #Pulsars and Gravitational Waves Research #Pulse (music) #Stars #astro-ph
paper · pdf · doi:10.1086/429222
published as Astrophys.J. 621 (2005) L113
openalex publication_date 2005/02/15 · arxiv created 2005/05/05 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/08/05
We present a temporal analysis of the three outbursts of the X-ray millisecond pulsar SAX J1808.4-3658 that occurred in 1998, 2000, and 2002. With a technique that uses the χ 2 obtained with an epoch-folding search to discriminate between different possible orbital solutions, we find an unique solution valid over the whole 5 yr period for which high temporal resolution data are available. We revise the estimate of the orbital period, P orb = 7249.1569(1) s, and reduce the corresponding error by 1 order of magnitude with respect to that previously reported. Moreover, we report the first constraint on the orbital period derivative, -6.6 × 10 -12 < orb < +0.8 × 10 -12 s s -1 . These values allow us to produce, via a folding technique, pulse profiles at any given time. Analysis of these profiles shows that the pulse shape is clearly asymmetric in 2002, occasionally showing a secondary peak at about 145° from the main pulse, which is quite different from the almost sinusoidal shape reported at the beginning of the 1998 outburst.