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 χ2 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, Porb=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<P˙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.
Papitto, A., MENNA M., T., Burderi, L., DI SALVO, T., D'Antona, F., & Robba, N. (2005). Revised Orbital Parameters of the Accreting Millisecond Pulsar SAX J1808.4-3658. THE ASTROPHYSICAL JOURNAL, 621, L113-L116.
|Data di pubblicazione:||2005|
|Titolo:||Revised Orbital Parameters of the Accreting Millisecond Pulsar SAX J1808.4-3658|
|Citazione:||Papitto, A., MENNA M., T., Burderi, L., DI SALVO, T., D'Antona, F., & Robba, N. (2005). Revised Orbital Parameters of the Accreting Millisecond Pulsar SAX J1808.4-3658. THE ASTROPHYSICAL JOURNAL, 621, L113-L116.|
|Digital Object Identifier (DOI):||http://dx.doi.org/10.1086/429222|
|Appare nelle tipologie:||1.01 Articolo in rivista|