Hybrid stars configurations

Figure 10. The Mass - radius relation and mass - central energy density dependencies for rotating (dashed lines) and nonrotating (solid lines) hybrid star configurations...

Figure 12. Cooling of hybrid star configurations of Fig. 9 with color superconducting quark matter core in 2SC+X phase. Different lines correspond to hybrid star masses in units of the solar mass.

It has been shown for a hybrid star model which uses the quark matter EoS presented in this work that the possibility to obtain a stable star configuration with 2SC quark matter core depends on the form-factor of the quark interaction [34], The Gaussian and Lorentzian form-factor models do allow a quark matter core, whereas the NJL form-factor model does not. 

In Fig. 3, we show the MR curve for pure HS within the GM1 model for the EOS of the hadronic phase, and that for hybrid stars or strange stars for different values of the bag constant B. The configuration marked with an asterisk on the hadronic MR curves represents the hadronic star for which the central pressure is equal to Pq. The full circle on the hadronic star sequence represents the critical mass configuration, in the case a = 30 MeV/fm2. The full... 

BIU < B < l>11. In this case, the critical mass for the pure hadronic star sequence is less than the maximum mass for the same stellar sequence, i.e., Mcr < Mus,max- Nevertheless (for the present EOS model), the baryonic mass Mb(Mcr) of the hadronic star with the critical mass is larger than the maximum baryonic mass MqS max of the hybrid star sequence. In this case, the formation of a critical size droplet of deconfined matter in the core of the hadronic star with the critical mass, will trigger off a stellar conversion process which will produce, at the end, a black hole (see cases marked as BH in Tab. 1 and Tab. 2). As in the previous case, it is extremely unlikely to populate the hybrid star branch. The compact star predicted by these EOS models are pure HS. Hadronic stars with a gravitational mass in the range Mhs(MqS rnax) < Mhs < Mcr (where MqS max is the baryonic mass of the maximum mass configuration for the hybrid star sequence) are metastable with respect to a conversion to a black hole. 

Figure 9. Mass - radius relations for compact star configurations with different EoS purely hadronic star with HHJ EoS (long-dashed), stable hybrid stars for HHJ - INCQM EoS with 2SC (solid) and without 2SC phase (dash-dotted) for the Gaussian formfactor. We show the influence of a tiny variation of the coupling constant Gi by the filled grey band. The difference between the models 2SC and 2SC corresponds to a shift in the bag function (see Fig. 8) 3 MeV/fm3. For comparison, observational constraints on the compactness are given from the "small compact star RX J1856.5-3754 and from the high surface redshift object EXO 0748-676 which can both be obeyed by our hybrid star EoS.

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