Resonant shattering flares as asteroseismic tests of chiral effective field theory

Chiral effective field theory (<a:math xmlns:a="http://www.w3.org/1998/Math/MathML"><a:mrow><a:mi>χ</a:mi><a:mi>EFT</a:mi></a:mrow></a:math>) has proved to be a powerful microscopic framework for predicting the properties of neutron-rich nuclear matter with quantified theoretical uncertainties up to about twice the nuclear saturation density. Tests of <b:math xmlns:b="http://www.w3.org/1998/Math/MathML"><b:mrow><b:mi>χ</b:mi><b:mi>EFT</b:mi></b:mrow></b:math> predictions are typically performed at low densities using nuclear experiments, with neutron star (NS) constraints only being considered at high densities. In this work, we discuss how asteroseismic quasinormal modes within NSs could be used to constrain specific matter properties at particular densities not just the integrated quantities to which bulk NS observables are sensitive. We focus on the crust-core interface mode, showing that measuring this mode's frequency would provide a meaningful test of <c:math xmlns:c="http://www.w3.org/1998/Math/MathML"><c:mrow><c:mi>χ</c:mi><c:mi>EFT</c:mi></c:mrow></c:math> at densities around half the saturation density. Conversely, we use nuclear matter properties predicted by <d:math xmlns:d="http://www.w3.org/1998/Math/MathML"><d:mrow><d:mi>χ</d:mi><d:mi>EFT</d:mi></d:mrow></d:math> to estimate that this mode's frequency is around <e:math xmlns:e="http://www.w3.org/1998/Math/MathML"><e:mrow><e:mn>185</e:mn><e:mo>±</e:mo><e:mn>50</e:mn><e:mspace width="0.28em"/><e:mtext>Hz</e:mtext></e:mrow></e:math>. Asteroseismic observables such as resonant phase shifts in gravitational-wave signals and multimessenger resonant shattering flare timings, therefore, have the potential to provide useful tests of <g:math xmlns:g="http://www.w3.org/1998/Math/MathML"><g:mrow><g:mi>χ</g:mi><g:mi>EFT</g:mi></g:mrow></g:math>.