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journal id: "astrophysicalxjournal"
| Authors | J.M. Hartman, A. Patruno, D. Chakrabarty, C.B. Markwardt, E.H. Morgan, M. van der Klis, R. Wijnands | | Title | A decade of timing an accretion-powered millisecond pulsar: the continuing spin down and orbital evolution of SAX J1808.4–3658 |
| Journal | Astrophysical Journal |
| Volume | 702 |
| Year | 2009 |
| Issue | 2 |
| Pages | 1673-1678 |
| ISSN | 0004637X |
| Faculty | Faculty of Science |
| Institute/dept. | FNWI: Astronomical Institute Anton Pannekoek (IAP) |
| Abstract | The Rossi X-ray Timing Explorer has observed five outbursts from the transient 2.5 ms accretion-powered pulsar SAX J1808.4-3658 during 1998-2008. We present a pulse timing study of the most recent outburst and compare it with the previous timing solutions. The spin frequency of the source continues to decrease at a rate of (-5.5 +/- 1.2) x 10(-18) Hz s(-1), which is consistent with the previously determined spin derivative. The spin down occurs mostly during quiescence, and is most likely due to the magnetic dipole torque from a B = 1.5 x 10(8) G dipolar field at the neutron star surface. We also find that the 2 hr binary orbital period is increasing at a rate of (3.80 +/- 0.06) x 10(-12) s s(-1), also consistent with previous measurements. It remains uncertain whether this orbital change reflects secular evolution or short-term variability. |
| Document type | Article |
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