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Thermonuclear (Type I) X-Ray Bursts Observed by the Rossi X-Ray Timing Explorer

Galloway, Duncan K. and Muno, Michael P. and Hartman, Jacob M. and Psaltis, Dimitrios and Chakrabarty, Deepto (2008) Thermonuclear (Type I) X-Ray Bursts Observed by the Rossi X-Ray Timing Explorer. Astrophysical Journal Supplement Series, 179 (2). pp. 360-422. ISSN 0067-0049. doi:10.1086/592044.

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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 10 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 detailed analysis of the variation of the burst profiles, energetics, recurrence times, presence of photospheric radius expansion, and presence of burst oscillations, as a function of accretion rate. We estimated the distance for 35 sources exhibiting radius-expansion bursts, and found that the peak flux of such bursts varies typically by 13%. We classified sources into two main groups based on the burst properties: (1) both long and short bursts (indicating mixed H/He accretion), and (2) consistently short bursts (primarily He accretion), and we calculated the mean burst rate as a function of accretion rate for the two groups. The decrease in burst rate observed at > 0.06dot MEdd (~2 × 10^37 ergs s^−1) is associated with a transition in the persistent spectral state and (as has been suggested previously) may be related to the increasing role of steady He burning. We found many examples of bursts with recurrence times <30 minutes, including burst triplets and even quadruplets. We describe the oscillation amplitudes for 13 of the 16 burst oscillation sources, as well as the stages and properties of the bursts in which the oscillations are detected. The burst properties are correlated with the burst oscillation frequency; sources spinning at <400 Hz generally have consistently short bursts, while the more rapidly spinning systems have both long and short bursts. This correlation suggests either that shear-mediated mixing dominates the burst properties, or alternatively that the nature of the mass donor (and hence the evolutionary history) has an influence on the long-term spin evolution.

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Chakrabarty, Deepto0000-0001-8804-8946
Additional Information:© 2008 The American Astronomical Society. Received 2006 August 7, accepted for publication 2008 June 12. Print publication: Issue 2 (2008 December). We are grateful to Pavlin Savov, who created the first version of the catalog on which this paper is based for an undergraduate project. We thank Erik Kuulkers and Jean in 't Zand for comments on early drafts of this paper. This work has benefited greatly from discussion and collaborative work with Andrew Cumming, Lars Bildsten, and Fred Lamb. This research has made use of data obtained through the High Energy Astrophysics Science Archive Research Center Online Service, provided by the NASA/Goddard Space Flight Center. This work was supported in part by the NASA Long Term Space Astrophysics program under grant NAG 5-9184 (PI: D. Chakrabarty).
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NASANAG 5-9184
Subject Keywords:nuclear reactions, nucleosynthesis, abundances; stars: distances; stars: neutron; X-rays: bursts
Issue or Number:2
Record Number:CaltechAUTHORS:GALapjss08
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Usage Policy:No commercial reproduction, distribution, display or performance rights in this work are provided.
ID Code:12694
Deposited By: Archive Administrator
Deposited On:20 Dec 2008 06:25
Last Modified:08 Nov 2021 22:32

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