There is as yet no firm evidence for quark matter cores in neutron stars. This is mainly because of the lack of direct probes of the opaque neutron star interior and the lack of clear qualitative difference between hadronic and quark phases. The detection of GW170817 along with the measurement of its tidal parameters has offered a first example of how the arrival of direct gravitational waves can be used to constrain the equation of state (EoS) of ultra-dense matter.

We shall discuss taking into account currently available information how to reveal possible phase transitions in neutron stars: the steadily growing body of astrophysical data and supported laboratory experiments should eventually allow us to narrow down the options by combining these various observations. We survey the proposed signatures of exotic matter and emphasize the importance of data from neutron star mergers.

Dr. Sophia Han obtained her Ph.D. in physics at Washington University in St. Louis in 2015, where she was supervised by Prof. Mark Alford. After graduation, she then joined Prof. Andrew Steiner’s group, working as a postdoc at University of Tennessee Knoxville and a guest visitor at Oak Ridge National Laboratory. Starting from September 2018, Sophia has been stationed at Ohio University within the N3AS Collaboration Network. Before coming to the U.S., she completed undergraduate degrees in Materials Science & Engineering (major) and English (minor) at Shanghai Jiao Tong University in 2009. Sophia’s research interests revolve around properties of dense matter in the QCD phase diagram and neutron star physics. She has been working on effects of possible phase transitions in neutron star Equation of State and relating them to astrophysical observations. She is also interested in constraining theoretical models of nuclear matter and connections to laboratory measurements of neutron-rich nuclei.