Hadron-Quark phase transition in the context of GW190814

Abstract: The properties of the neutron stars are calculated for the hadronic matter within the density-dependent relativistic mean-field model (DD-RMF). The phase transition to the quark matter is studied and the hybrid star matter properties are systematically calculated using the Vector-Enhanced Bag model (vBag). The maximum mass of neutron star with DD-LZ1 and DD-RMF parameter sets is found to be around 2.55$M_{\odot}$ for pure hadronic phase and around 2$M_{\odot}$ for hadron-quark mixed phase using both Gibbs and Maxwell construction. The tidal deformability for the hybrid EoS at 1.4$M_{\odot}$, $\Lambda_{1.4}$, remains unchanged from the pure hadronic EoS with Maxwell construction, but decreases with the increasing neutron star mass for Gibbs construction. While the pure hadron matter EoS satisfies the mass constraint from recently observed GW190814 data, implying a stiff neutron star EoS, the hadron-quark phase transition satisfies the constraints from the recent observations GW170817. Therefore, we cannot exclude the possibility of the secondary object in GW190814 as a neutron star with a phase transition to the quark matter that satisfies the 2$M_{\odot}$ maximum mass limit.