Electromagnetic signal of the QCD phase transition in neutron star mergers

Abstract

Mergers of binary neutron stars create conditions of supranuclear density $n\gtrsim n_{\mathrm{nuc}}\simeq 0.17{\mathrm{fm}}^{-3}$ and moderate temperature $50\lesssim T\lesssim 90\mathrm{MeV}$. These events thus probe a sensitive region of the density-temperature phase diagram of QCD matter. We study photon production by the QCD conformal anomaly for a signal of a possible transition to quark degrees of freedom during the merger. We discuss energy loss due to photon radiation as a cooling mechanism that is sensitive to the bulk viscosity and thermal conductivity of the quark matter.

Comments: 9 pages, 3 figures, two column revtex format; v2 typos corrected, Sec II discussion improved; v3 as published