2003/10/31 by Michael P. Muno, M. P. Muno, Duncan K. Galloway +3 · 1 citation
Physics and Astronomy · #Astrophysical Phenomena and Observations #Gamma-ray bursts and supernovae #Pulsars and Gravitational Waves Research #astro-ph
paper · pdf · doi:10.1086/420812
published as Astrophys.J. 608 (2004) 930-934 · 5 pages, including 2 figures. To appear in 20 June 2004 issue of ApJ. Added references and made minor changes to discussion
arxiv created 2004/03/16 · openalex publication_date 2004/06/11 · arxiv updated 2009/12/01 · openalex created_date 2025/10/10 · openalex updated_date 2026/07/31
Using observations with the Rossi X-Ray Timing Explorer , we previously showed that millisecond oscillations occur preferentially in thermonuclear X-ray bursts with photospheric radius expansion from sources rotating near 600 Hz, while they occur with equal likelihood in X-ray bursts with and without radius expansion for sources rotating near 300 Hz. In this paper, we use a larger sample of data to demonstrate that the detectability of the oscillations is not directly determined by the properties of the X-ray bursts. Instead, we find that (1) the oscillations are observed almost exclusively when the accretion rate onto the neutron star is high, but that (2) radius expansion is only observed at high accretion rates from the ≃600 Hz sources, whereas it occurs only at low accretion rates in the ≃300 Hz sources. The persistent millisecond pulsars provide the only apparent exceptions to these trends. The first result might be explained if the oscillation amplitudes are attenuated at low accretion rates by an extended electron corona. The second result indicates that the rotation period of the neutron star determines how the burst properties vary with accretion rate, possibly through the differences in the effective surface gravity or the strength of the Coriolis force.