Compact object of HESS J1731-347 and its implication on neutron star matter

In this work, we investigate the impact of the possibility of a small, subsolar mass compact star, such as the recently reported central compact object of HESS J1731-347, on the equation of state (EOS) of neutron stars. We have used a hybrid approach to the nuclear EOS developed recently where the matter around nuclear saturation density is described by a parametric expansion in terms of nuclear empirical parameters and represented in an agnostic way at higher density using piecewise polytropes. We have incorporated the inputs provided by the latest neutron skin measurement experiments from PREX-II and CREX, simultaneous mass-radius measurements of pulsars PSR <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"> <a:mrow> <a:mi mathvariant="normal">J</a:mi> <a:mn>0030</a:mn> <a:mo>+</a:mo> <a:mn>0451</a:mn> </a:mrow> </a:math> and PSR <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" display="inline"> <d:mrow> <d:mi mathvariant="normal">J</d:mi> <d:mn>0740</d:mn> <d:mo>+</d:mo> <d:mn>6620</d:mn> </d:mrow> </d:math> , and the gravitational wave events GW170817 and GW190425. The main results of the study show the effect of HESS J1731-347 on the nuclear parameters and neutron star observables. Our analysis yields the slope of symmetry energy <g:math xmlns:g="http://www.w3.org/1998/Math/MathML" display="inline"> <g:mi>L</g:mi> <g:mo>=</g:mo> <g:mn>45.7</g:mn> <g:msubsup> <g:mn>1</g:mn> <g:mrow> <g:mo>−</g:mo> <g:mn>22.11</g:mn> </g:mrow> <g:mrow> <g:mo>+</g:mo> <g:mn>38.18</g:mn> </g:mrow> </g:msubsup> <g:mtext> </g:mtext> <g:mtext> </g:mtext> <g:mi>MeV</g:mi> </g:math> , the radius of a <i:math xmlns:i="http://www.w3.org/1998/Math/MathML" display="inline"> <i:mn>1.4</i:mn> <i:msub> <i:mi>M</i:mi> <i:mo stretchy="false">⊙</i:mo> </i:msub> </i:math> star, <l:math xmlns:l="http://www.w3.org/1998/Math/MathML" display="inline"> <l:msub> <l:mi>R</l:mi> <l:mn>1.4</l:mn> </l:msub> <l:mo>=</l:mo> <l:mn>12.1</l:mn> <l:msubsup> <l:mn>8</l:mn> <l:mrow> <l:mo>−</l:mo> <l:mn>0.88</l:mn> </l:mrow> <l:mrow> <l:mo>+</l:mo> <l:mn>0.71</l:mn> </l:mrow> </l:msubsup> <l:mtext> </l:mtext> <l:mtext> </l:mtext> <l:mi>km</l:mi> </l:math> , and the maximum mass of a static star, <n:math xmlns:n="http://www.w3.org/1998/Math/MathML" display="inline"> <n:msub> <n:mi>M</n:mi> <n:mi>max</n:mi> </n:msub> <n:mo>=</n:mo> <n:mn>2.1</n:mn> <n:msubsup> <n:mn>4</n:mn> <n:mrow> <n:mo>−</n:mo> <n:mn>0.17</n:mn> </n:mrow> <n:mrow> <n:mo>+</n:mo> <n:mn>0.26</n:mn> </n:mrow> </n:msubsup> <n:msub> <n:mi>M</n:mi> <n:mo stretchy="false">⊙</n:mo> </n:msub> </n:math> within 90% confidence interval, respectively.