Original title: Constraining equation of state of neutron star using neutron star-black hole mergers
Vasudev Dubey, Rahul Kashyap, Yugesh Bhoge · August 2026
Neutron stars are extremely dense dead stars. Scientists want to understand what matter inside them is made of, which is described by an equation of stateA set of rules that describes what a neutron star is made of and how its matter behaves under extreme pressure.. When a neutron star orbits a black hole, the black hole pulls on it. This stretching, called tidal deformation, imprints clues into gravitational waves, which are ripples in space. Unlike mergers between two neutron stars that blur their properties together, a neutron star-black hole merger lets scientists directly measure how easily the single neutron star deforms. The researchers simulated hundreds of these mergers using future gravitational wave detectors. They found that detectors like the Einstein Telescope and Cosmic Explorer will need at least 20 merger events to clearly tell different equations of state apart.
Imagine trying to guess the recipe of a cake by watching it bake. If two cakes are in the same oven, their effects mix, and you cannot tell which ingredient belongs to which cake. In this paper, the black hole acts like a single oven, so the neutron star's deformation is measured clearly, like watching one cake bake alone. The researchers find that you need at least 20 such cakes to confidently identify the recipe.
Neutron stars are the densest objects in the universe, but we don't know what they're made of. By studying gravitational waves from neutron star-black hole mergers, scientists can measure how the neutron star gets deformed, which reveals its internal composition. This work shows that with future detectors, we'll need at least 20 such mergers to clearly distinguish between different possible compositions, guiding how we plan observations.
This is a simulation study, not actual observations. It assumes future detector sensitivities and does not account for possible systematic errors or astrophysical uncertainties in the population of NSBH mergers. The requirement of 20 events may vary with different equations of state or detector configurations not considered.
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Constraining equation of state of neutron star using neutron star-black hole mergers — Vasudev Dubey, Rahul Kashyap, Yugesh Bhoge
Abstract licence: CC0
Explanation generated by Synthesis from the abstract — it is not the original paper. This is a preprint, so it hasn't necessarily been peer reviewed.