Analyzing the length of the slow stable hybrid star branch and its linkage with multi-messenger observations of compact stars

MARIANI, MAURO; MILVA G. ORSARIA; LEANDRO DIVANO; IGNACIO FRANCISCO RANEA SANDOVAL

Congreso; XVII Latin American Regional IAU Meeting; 2023

The internal composition of neutron stars, one of the densest astronomical objects in the universe,is still unknown. Although in the last decade, with the onset of multi-messenger gravitational waveastronomy, several astrophysical observations placed strong constraints on these compact objects, there isstill a lack of understanding of the dense matter equation of state. In this work, we model neutron starsas hybrid stars -composed of an inner core of quark matter and a mantle of hadronic matter-, consideringan abrupt and slow first-order hadron-quark phase transition in their core. We model the hadronic phasewith a piecewise polytropic fit, and the inner quark core through a Color Flavor Locked superconductingequation of state, with corrections due to the strong coupling constant, within the framework of the MITBag model. In the framework of this abrupt and slow scenario, it is possible to obtain an extended branchof stable stellar configurations. It has been shown that the appearance of such branches could resolve theexisting tension between current astrophysical observations. We analyze the behavior of this extendedstability branch by quantifying and systematically studying, for the first time, its length, relating thisquantity to fundamental properties of the hybrid equation of state. This study allows not only a deeperunderstanding of the extended stability scenario with slow hadron-quark conversions but could reveal themystery of the composition of neutron stars and, consequently, clarify the uncertainty about the equationof state of dense matter.