The nuclear reaction waiting points:: 22Mg, 26Si, 30S, and 34Ar and bolometrically double-peaked type I x-ray bursts

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 is 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: Mg-22, Si-26, S-30, and Ar-34, 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 photodisintegration at the burst temperature. The conclusion is that the effects of the experimentally unknown S-30(alpha,p)Cl-33 and Ar-34(alpha,p)K-37 might be directly visible in the observation of X-ray burst light curves.