Consistent Modeling of GS 1826-24 X-ray Bursts for Multiple Accretion Rates Demonstrates the Possibility to Constrain rp-process Reaction Rates

Abstract

Type-I X-ray burst light curves encode unique information about the structure of accreting neutron stars and the nuclear reaction rates of the rp-process that powers bursts. Using the first model calculations of hydrogen/helium burning bursts for a large range of astrophysical conditions performed with the code MESA, this work shows that simultaneous model-observation comparisons for bursts from several accretion rates $\dot{M}$ are required to remove degeneracies in astrophysical conditions that otherwise reproduce bursts for a single $\dot{M}$ and that such consistent multi-epoch modeling could possibly limit the ${}^{15}\mathrm{O}(\alpha ,\gamma {)}^{19}\mathrm{Ne}$ reaction rate. Comparisons to the year 1998, 2000, and 2007 bursting epochs of the neutron star GS 1826-24 show that $\dot{M}$ must be larger than previously inferred and that the shallow heating in this source must be below 0.5 MeV/u, providing a new method to constrain the shallow heating mechanism in the outer layers of accreting neutron stars. Features of the light curve rise are used to demonstrate that a lower-limit could likely be placed on the ${}^{15}\mathrm{O}(\alpha ,\gamma )$ reaction rate, demonstrating the possibility of constraining nuclear reaction rates with X-ray burst light curves.

Accepted to the Astrophysical Journal

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