Abstract
On 14 August 2019, the LIGO/Virgo collaboration observed a compact object with mass ∼2.59−0.09+0.08M⊙, as a component of a system where the main companion was a black hole with mass ∼23M⊙. A scientific debate initiated concerning the identification of the low mass component, as it falls into the neutron star–black hole mass gap. The understanding of the nature of GW190814 event will offer rich information concerning open issues, the speed of sound and the possible phase transition into other degrees of freedom. In the present work, we made an effort to probe the nuclear equation of state along with the GW190814 event. Firstly, we examine possible constraints on the nuclear equation of state inferred from the consideration that the low mass companion is a slow or rapidly rotating neutron star. In this case, the role of the upper bounds on the speed of sound is revealed, in connection with the dense nuclear matter properties. Secondly, we systematically study the tidal deformability of a possible high mass candidate existing as an individual star or as a component one in a binary neutron star system. As the tidal deformability and radius are quantities very sensitive on the neutron star equation of state, they are excellent counters on dense matter properties. We conjecture that similar isolated neutron stars or systems may exist in the universe and their possible future observation will shed light on the maximum neutron star mass problem.
Highlights
In Ref. [1] the authors reported the observation of a compact binary coalescence involving a 22.2–24.3 M black hole and a compact object with a mass of a 2.50–2.67 M
The merger of a very massive black hole (∼23 M ) with a ∼2.6 M compact object has recently been announced by the LIGO/Virgo collaboration, as the GW190814 event
We note that the pure MDI-APR [35] (MDI)-APR equation of state (EoS) was in the range of the described limits for the gravitational mass and Kerr parameter, as well as the ones introduced in Figure 1, being a suitable hadronic EoS to simulate the compact object of ∼2.6 M
Summary
In Ref. [1] the authors reported the observation of a compact binary coalescence involving a 22.2–24.3 M black hole and a compact object with a mass of a 2.50–2.67 M (all measurements quoted at the 90% credible level). More relevant to the present study, the observation of the GW190814 event led to the following conclusion: due to the source’s asymmetric masses, the lack of detection of an electromagnetic counterpart and of clear signature of tides or spin-induced quadrupole effect in the waveform of the gravitational waves we are not able to distinguish between a black hole-black hole and black hole-neutron star system [1]. In this case, one must count only to the comparison between the mass of the second partner with the estimation of maximum NSs mass Mmax [2].
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