arXiv subjects

M. Nava-Callejas

Publications and source records attributed to M. Nava-Callejas.

2 recordsLinked to original sources

arXiv2026

On the superbursts as photodisintegrators of ashes from the rp-process -- Numerical simulations of superbursts with MESA II

Context: Superbursts are energetic explosions in the crusts of neutron stars in Low-Mass X-ray Binaries (LMXBs). At temperatures above 4 GK, photodisintegration of heavy rp-process ashes may play a major role alongside $^{12}$C fusion. Aims: We investigate how photodisintegration of rp-process ashes affects superburst properties and the initial $^{12}$C abundance required for ignition. Methods: We simulate superbursts with MESA v.24.08.1. Besides the canonical fuel of $20\%$ $^{12}$C and $80\%$ $^{56}$Fe, we test different $^{12}$C abundances mixed with scaled rp-process ashes. Results: Superbursts can ignite with only $10\%$ $^{12}$C when the remaining $90\%$ consists of rp-process ashes. Their luminosity is comparable to that of the canonical fuel, whereas $10\%$ $^{12}$C mixed with $90\%$ $^{56}$Fe yields lower luminosity. $^{56}$Fe remains the most abundant ash nuclide. Although photodisintegration drives nucleosynthesis, neutron, proton and alpha captures release energy at late times. We also find that $A=64$ nuclides or $^{20}$Ne help reduce the $^{12}$C abundance needed for ignition. Conclusions: The composition of accreted material - not just its $^{12}$C content - substantially affects superburst ignition, luminosity and nucleosynthesis.

astro-ph.HE↗

arXiv2026

A solution to the tension of burning on neutron stars and nuclear physics

When neutron stars accrete matter from a companion star, this matter forms a disc around them and eventually falls on their surface. Here, the fuel can ignite into bright flashes called Type I bursts. Theoretical calculations based on state-of-the-art nuclear reactions are able to explain many features of the bursts. However, models predict that the bursts should cease at high accretion rates, whereas in many sources they disappear at much lower rates. Moreover, their recurrence times also show strong discrepancies with predictions. Although various solutions have been proposed, none can account for all the observational constraints. Here we describe a new model that explains all the contradictory behaviours within a single picture. We are able to reconstruct the conditions on the star surface that determine the burst properties by comparing data to new simulations. We find strong evidence that the physical mechanism driving the burst behaviour is the structure of the accretion disc in the regions closest to the star. This connection reconciles the puzzling burst phenomenology with nuclear physics and also opens a new window on the study of accretion processes around compact objects.

astro-ph.HE↗