AAS 206th Meeting, 29 May - 2 June 2005
Session 17 Fundamental Physics with Millisecond Pulsars
Special Session, Monday, 10:00-11:30am, May 30, 2005, 102 C

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[17.06] The newest accreting millisecond X-ray pulsar: IGR J00291+5934

D. K. Galloway (MIT), C. B. Markwardt (NASA GSFC), E. H. Morgan, D. Chakrabarty (MIT), T. E. Strohmayer (NASA GSFC)

Accreting millisecond X-ray pulsars are the long-sought evolutionary progenitors of ``recycled" millisecond radio pulsars. The population of these sources has grown rapidly over the last three years, with the discovery of five new examples. The latest, IGR J00291+5934, was first detected in outburst by ESA's International Gamma-Ray Astrophysics Laboratory (INTEGRAL) in December 2004, and was subsequently observed by the Rossi X-ray Timing Explorer (RXTE). The neutron star in this 2.46~hr binary has the most rapid spin of the accretion-powered pulsars at 599 Hz. Two previous outbursts were detected retroactively in the RXTE All-Sky Monitor lightcurve, each three years before the next. IGR J00291+5394 is similar in almost every respect to the first accreting millisecond pulsar discovered, SAX J1808.4-3658. I will compare the properties of these two sources to the rest of the sample, and also present recent evidence for variations in the long-term accretion rate.

This work was supported in part by the NASA Long Term Space Astrophysics program under grant NAG 5-9184.

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