Implications of latest NICER data for the neutron star equation of state

As an update to our previously performed Bayesian inference analyses of the neutron star matter equation-of-state and related quantities, the additional impact of the recently published NICER data of PSR J0437-4751 is examined. Including the mass and radius distributions of this pulsar in our database results in modest shifts from previously inferred median posterior values of radii <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" display="inline"><a:mi>R</a:mi></a:math> and central densities <c:math xmlns:c="http://www.w3.org/1998/Math/MathML" display="inline"><c:msub><c:mi>n</c:mi><c:mi>c</c:mi></c:msub></c:math> for representative <e:math xmlns:e="http://www.w3.org/1998/Math/MathML" display="inline"><e:mn>1.4</e:mn><e:msub><e:mi>M</e:mi><e:mo stretchy="false">⊙</e:mo></e:msub></e:math> and <h:math xmlns:h="http://www.w3.org/1998/Math/MathML" display="inline"><h:mn>2.1</h:mn><h:msub><h:mi>M</h:mi><h:mo stretchy="false">⊙</h:mo></h:msub></h:math> neutron stars: radii are reduced by about 0.2–0.3 km to values of <k:math xmlns:k="http://www.w3.org/1998/Math/MathML" display="inline"><k:msub><k:mi>R</k:mi><k:mn>1.4</k:mn></k:msub><k:mo>=</k:mo><k:mn>12.1</k:mn><k:mo>±</k:mo><k:mn>0.5</k:mn><k:mtext> </k:mtext><k:mtext> </k:mtext><k:mi>km</k:mi></k:math> and <m:math xmlns:m="http://www.w3.org/1998/Math/MathML" display="inline"><m:msub><m:mi>R</m:mi><m:mn>2.1</m:mn></m:msub><m:mo>=</m:mo><m:msubsup><m:mn>11.9</m:mn><m:mrow><m:mo>−</m:mo><m:mn>0.6</m:mn></m:mrow><m:mrow><m:mo>+</m:mo><m:mn>0.5</m:mn></m:mrow></m:msubsup><m:mtext> </m:mtext><m:mtext> </m:mtext><m:mi>km</m:mi></m:math> (at the 68% level), and central densities increase slightly to values of <o:math xmlns:o="http://www.w3.org/1998/Math/MathML" display="inline"><o:msub><o:mi>n</o:mi><o:mi>c</o:mi></o:msub><o:mo stretchy="false">(</o:mo><o:mn>1.4</o:mn><o:msub><o:mi>M</o:mi><o:mo stretchy="false">⊙</o:mo></o:msub><o:mo stretchy="false">)</o:mo><o:mo>/</o:mo><o:msub><o:mi>n</o:mi><o:mn>0</o:mn></o:msub><o:mo>=</o:mo><o:mn>2.8</o:mn><o:mo>±</o:mo><o:mn>0.3</o:mn></o:math> and <t:math xmlns:t="http://www.w3.org/1998/Math/MathML" display="inline"><t:msub><t:mi>n</t:mi><t:mi>c</t:mi></t:msub><t:mo stretchy="false">(</t:mo><t:mn>2.1</t:mn><t:msub><t:mi>M</t:mi><t:mo stretchy="false">⊙</t:mo></t:msub><t:mo stretchy="false">)</t:mo><t:mo>/</t:mo><t:msub><t:mi>n</t:mi><t:mn>0</t:mn></t:msub><t:mo>=</t:mo><t:msubsup><t:mn>3.8</t:mn><t:mrow><t:mo>−</t:mo><t:mn>0.7</t:mn></t:mrow><t:mrow><t:mo>+</t:mo><t:mn>0.6</t:mn></t:mrow></t:msubsup></t:math> (in units of equilibrium nuclear matter density, <y:math xmlns:y="http://www.w3.org/1998/Math/MathML" display="inline"><y:msub><y:mi>n</y:mi><y:mn>0</y:mn></y:msub><y:mo>=</y:mo><y:mn>0.16</y:mn><y:mtext> </y:mtext><y:mtext> </y:mtext><y:msup><y:mrow><y:mi>fm</y:mi></y:mrow><y:mrow><y:mo>−</y:mo><y:mn>3</y:mn></y:mrow></y:msup></y:math>)—i.e., they still fall below five times nuclear saturation density at the 68% level. As a further significant result, the evidence established by analyzing Bayes factors for a trace anomaly measure, <ab:math xmlns:ab="http://www.w3.org/1998/Math/MathML" display="inline"><ab:mi mathvariant="normal">Δ</ab:mi><ab:mo>=</ab:mo><ab:mn>1</ab:mn><ab:mo>/</ab:mo><ab:mn>3</ab:mn><ab:mo>−</ab:mo><ab:mi>P</ab:mi><ab:mo>/</ab:mo><ab:mi>ϵ</ab:mi><ab:mo>&lt;</ab:mo><ab:mn>0</ab:mn></ab:math>, inside heavy neutron stars is raised to .