Revised orbital parameters of the accreting millisecond pulsar SAX J1808.4-3658

被引:27
作者
Papitto, A
Menna, MT
Burderi, L
Di Salvo, T
D'Antona, F
Robba, NR
机构
[1] Osserv Astron Roma, I-00040 Rome, Italy
[2] Univ Palermo, Dipartimento Sci Fis & Astron, I-90123 Palermo, Italy
关键词
pulsars : general; pulsars : individual (SAX J1808.4-3658); stars : magnetic fields; stars : neutron; X-rays : binaries;
D O I
10.1086/429222
中图分类号
P1 [天文学];
学科分类号
0704 ;
摘要
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 chi(2) obtained with an epoch-folding search to x 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 x 10(-12) <(P) over dot P-orb < +0.8 x 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 degrees from the main pulse, which is quite different from the almost sinusoidal shape reported at the beginning of the 1998 outburst.
引用
收藏
页码:L113 / L116
页数:4
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