2.6 M⊙ compact object and neutron stars in Eddington-inspired Born-Infeld theory of gravity

In the context of whether a massive compact object recently observed in the GW190814 event is a neutron star (NS) or not, we study the role of the parameters kappa and Lambda(c) of the Eddington-inspired Born-Infeld (EiBI) gravity theory in the NS mass-radius relation, moment of inertia, and tidal deformability. The results are compared to recent observational constraints extracted from the analysis of NS observation data. The NS core equation of state (EoS) is calculated using the relativistic mean-field model with the G3 parameter set. In the hyperon sector, the SU(3) and hyperon potential depths are used to determine the hyperon coupling constants. For the inner and outer crusts, we use the crust EoS from Miyatsu et al. [Astrophys. J. 777, 4 (2013)]. We also maintain the sound speed to not exceed c/root 3 - at high densities. We find that, in general, the NS mass significantly depends on the value of kappa, and the radius R is sensitive to the value of Lambda(c). Moreover, as Lambda(c) is equal to zero or less than the accepted bound of the cosmological constant, the NS within the EiBI theory is compatible with observational constraints, including 2.0 M-circle dot mass, canonical radius R1.4 M circle dot, moment of inertia, and tidal deformation. Our investigation also reveals that the 2.6 M-circle dot mass compact object and current observational constraint of canonical radius R1.4 M circle dot can simultaneously be satisfied only when the Lambda(c) value is unphysically too large and negative. Therefore, within the specific EoS employed in this work, we conclude that the secondary object with 2.6 M-circle dot observed in the GW190814 event [1] is not likely a static (or a slow-rotating) NS within the EiBI gravity theory.

Automated summary

The study explores the role of parameters kappa and Lambda(c) of the EiBI gravity theory in the mass-radius relation, moment of inertia, and tidal deformability of neutron stars. Results show that the mass of neutron stars significantly depends on kappa, while the radius is sensitive to the value of Lambda(c). The 2.6 solar mass compact object observed in the GW190814 event is unlikely to be a static neutron star within the EiBI gravity theory given the specific equation of state employed.