Duncan K. Galloway

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Millisecond pulsars are neutron stars that are thought to have been spun-up by mass accretion from a stellar companion. It is not known whether there is a natural brake for this process, or if it continues until the centrifugal breakup limit is reached at submillisecond periods. Many neutron stars that are accreting mass from a companion star exhibit(More)
We have assembled a sample of 1187 thermonuclear (type-I) X-ray bursts from observations of 48 accreting neutron stars by the Rossi X-ray Timing Explorer, spanning more than ten years. The sample contains examples of two of the three theoretical ignition regimes (confirmed via comparisons with numerical models) and likely examples of the third. We present a(More)
We have identified the third known accretion-powered millisecond pulsar, XTE J0929−314, with the Rossi X-Ray Timing Explorer. The source is a faint, high–Galactic-latitude X-ray transient in the Galactic bulge (d 9 kpc) that was in outburst during 2002 April–June. The 185 Hz (5.4 ms) pulsation had a fractional rms amplitude of 3–7% and was generally broad(More)
We report on observations of the sixth accretion-powered millisecond pulsar, IGR J00291+5934, with the Rossi X-Ray Timing Explorer. The source is a faint, recurrent X-ray transient initially identified by INTEGRAL. The 599 Hz (1.67 ms) pulsation had a fractional rms amplitude of 8% in the 2–20 keV range, and its shape was approximately sinusoidal. The(More)
We analysed Rossi X-ray Timing Explorer observations of the accretion-powered 401 Hz pulsar SAX J1808.4−3658, in order to precisely determine the source distance. While the fluences for the five transient outbursts observed from 1996 were constant to within the uncertainties, the outburst interval varied signficantly, so that the time-averaged flux (and(More)
We analyze the frequency evolution of millisecond oscillations observed during type I X-ray bursts with the Rossi X-ray Timing Explorer in order to establish the stability of the mechanism underlying the oscillations. Our sample contains 68 pulse trains detected in a search of 159 bursts from 8 accreting neutron stars. As a first step, we confirm that the(More)
The Australian Square Kilometre Array Pathfinder (ASKAP) will give us an unprecedented opportunity to investigate the transient sky at radio wavelengths. In this paper we present VAST, an ASKAP survey for Variables and Slow Transients. VAST will exploit the wide-field survey capabilities of ASKAP to enable the discovery and investigation of variable and(More)
Compton scattering of X-rays in the bulk flow of the accretion column in magnetic cat-aclysmic variables (mCVs) can significantly shift photon energies. We present Monte Carlo simulations based on a nonlinear algorithm demonstrating the effects of Comp-ton scattering on the H-like, He-like and neutral Fe Kα lines produced in the post-shock region of the(More)
The population of accretion-powered millisecond pulsars (AMSPs) has grown rapidly over the last four years, with the discovery of six new examples to bring the total sample to seven. While the first six discovered are transients active for a few weeks every two or more years, the most recently-discovered source HETE J1900.1−2455, has been active for more(More)
We present a detailed study of the correlations between the burst properties and the inferred mass accretion rate for the X-ray transient MXB 1659–298. The bursts which exhibited oscillations were observed when the source was at relatively high mass accretion rate, similar to what has been seen for other sources. However, due to the limited number of(More)