Speaker
Description
The gravitational wave (GW) events offer new insights into compact stars. The binary merger GW170817 and its electromagnetic counterpart have led to new constraints on the maximum mass of neutron stars (NSs). Based on GW170817, the upper bound of MTOV for NSs is predicted as (2.3-2.4)M⊙. However, there are other observations of pulsars and binary mergers consisting of components or remnants with masses more than this value which fall within the unknown mass gap region (2.5-5M⊙). For example, PSR J0952-0607, the secondary component of GW190814, and the remnants of GW170817 and GW190425 have masses more than the maximum mass predicted for NSs. For two important reasons, the possibility of such massive NSs seems very unlikely. Firstly, for non-rotating NSs, the equation of state (EOS) must be very rigid to get such massive objects. This contrasts the tidal deformability constraint, which requires softer EOSs. Secondly, for a rotating NS, the rotation rate should be close to the Keplerian limit. Now, the question arises whether these objects are the smallest black holes or other forms of compact stars like hybrid stars and self-bounded strange quark stars.
My research findings indicate that by using a modified version of the Nambu-Jona-Lasinio model and a modified theory of gravity (massive gravity), it is possible to obtain quark stars that not only have masses fall in the mass gap region but also satisfy the GW observational constraints well.
