Abstract
Neutron stars (NSs) are excellent natural laboratories to constrain gravity on strong field regime and nuclear matter in extreme conditions. Motivated by the recent discovery of a compact object with 2.59^{+0.08}_{-0.09} M_odot in the binary merger GW190814, if this object was a NS, it serves as a strong constraint on the NS equation of state (EoS), ruling out several soft EoSs favored by GW170817 event. In this work, we revisit the question of the maximum mass of NSs considering a chameleon screening (thin-shell effect) on the NS mass-radius relation, where the microscopic physics inside the NS is given by realistic soft EoSs. We find that from appropriate and reasonable combination of modified gravity, rotation effects and realistic soft EoSs, that it is possible to achieve high masses and explain GW190814 secondary component, and in return also NSs like PSR J0740 + 6620 (the most NS massive confirmed to date). It is shown that gravity can play an important role in estimating maximum mass of NSs, and even with soft EoSs, it is possible to generate very high masses. Therefore, in this competition of hydrostatic equilibrium between gravity and pressure (from EoS choice), some soft EoSs, in principle, cannot be completely ruled out without first taking into account gravitational effects.
Highlights
The discovery of the gravitational wave (GW) binary GW190814 triggered intense theoretical efforts about the real nature of its secondary component, in particular, the high mass requires the compact star matter to be described by a stiff equation of state (EoS)
In [6] the authors infer a lower limit on the maximum mass Mmax of non-rotating Neutron stars (NSs), using arguments based on universal relations connecting the masses and spins of uniformly rotating NSs
They obtain a lower bound on the dimensionless spin for the secondary companion, using the upper maximum mass constraints from the GW170817 event [7,8], and show that the allowed range in dimensionless spins correspond to rotational frequencies much higher than the fastest millisecond pulsars known [9]
Summary
The discovery of the gravitational wave (GW) binary GW190814 triggered intense theoretical efforts about the real nature of its secondary component, in particular, the high mass requires the compact star matter to be described by a stiff equation of state (EoS). In [10] a rigorous upper bounds on maximum mass under the exclusive assumptions of causality and general relativity (GR), showing that the presence of a NS in GW190814 is not inconsistent with present observational constraints on the NS EoS. The two main observable of a NS, i.e., their mass and radius, both depend crucially on the choice of EoS and the gravitational theory, where gravity will deter-. We analyze the NS mass-radius relation through a modification of the TOV equations induced by the presence of a possible chameleon screening (thin-shell effect), where the microscopic physics inside the NS will be modeled by realistic soft EoSs of which it is not possible to generate very massive NS with ∼ 2.6 M or even ∼ 2.14 M in GR context.
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
