Speaker
Description
Superbursts are very energetic explosions occurring at the outer crusts of neutron stars, as a consequence of unstable carbon burning . They release up to $10^{40}$ erg in a span of hours/days and have recurrence times in the order of years. In contrast to the standard, less-energetic bursts due to H/He burning, only a few multi-zone simulations have been reported. While these pioneering works are successful in explaining the observational characteristics of the superbursts, from the point of view of nuclear physics many questions are still open. For instance, the impact changing the carbon fusion rate has over all the observable properties of the superbursts, as well as those not directly observable, such as the distribution of ashes from carbon burning. In recent years the carbon fusion rate has been reviewed, and although at high temperatures there is agreement with the old CF88 rate, at temperatures between $10^8$ and $10^9$ K - typical of superburst ignition - it has been claimed the rate can be either 1000 times larger or smaller than CF88. The purpose of my talk is to present my results from recent multi-zone simulations of superbursts carried with the public stellar code MESA, in which we consider four different versions of the carbon fusion rate. We find that enhancing the carbon fusion rate leads to a reduction in the recurrence time and exponential decay of luminosity, while reducing the carbon fusion rate leads to the reverse effect. We find changing the carbon fusion rate has comparable effects as to change the base luminosity of the crust.