2004ApJ...608L..61F

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: ²²Mg, ²⁶Si, ³⁰S, and ³⁴Ar, which arise in conditions, where a further reaction flow has to await a β⁺-decay, because the (α,p)-reaction is too weak to overcome the target Coulomb barrier and the (p,γ)-reaction is quenched by photodisintegration at the burst temperature. The conclusion is that the effects of the experimentally unknown ³⁰S(α,p)³³Cl and ³⁴Ar(α,p)³⁷K might be directly visible in the observation of X-ray burst light curves.