The Nuclear Reaction Waiting Points: 22 Mg, 26 Si, 30 S, and 34 Ar and Bolometrically Double-peaked Type I X-Ray Bursts

Abstract
Type I X-ray bursts with a double peak in the bolometric luminosity have been observed from several sources. The separation between the two peaks are on the order of a few seconds. We propose a nuclear waiting point impedance in the thermonuclear reaction flow to explain these observations. Nuclear structure information suggests the potential waiting points: Mg22, Si26, S30 and Ar34, which arise in conditions, where a further reaction flow has to await a beta-decay, because the (alpha,p)-reaction is too weak to overcome the target Coulomb-barrier and the (p,gamma)-reaction is quenched by photo-disintegration at the burst temperature. The conclusion is that the effects of the experimentally unknown S30(alpha,p)Cl33 and Ar34(alpha,p)K37 might be directly visible in the observation of X-ray burst light curves.Comment: 5 pages, 3 figures, submitted to Astrophys. J. Let
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