Routing (electronic design automation)

X-ray binary

Spin (aerodynamics)

Pulsar

Galaxy

Stellar black hole

Nuclear physics

Particle physics

Compact star

Astrophysics

Computer science

Spins

Computer network

Neutron

Thermodynamics

Routing protocol

Physics

Link-state routing protocol

Condensed matter physics

Primary (astronomy)

Neutron star

Black hole (networking)

Star (game theory)

Monthly Notices of the Royal Astronomical Society Letters

The recent detection of GW190814 featured the merger of a binary with a primary having a mass of $\sim 23\,M_{\odot}$ and a secondary with a mass of $\sim 2.6\,M_{\odot}$. While the primary was most likely a black hole, the secondary could be interpreted as either the lightest black hole or the most massive neutron star ever observed, but also as the indication of a novel class of exotic compact objects. We here argue that the secondary in GW190814 needs not be an ab-initio black hole nor an exotic object; rather, based on our current understanding of the nuclear-matter equation of state, it can be a rapidly rotating neutron star that collapsed to a rotating black hole at some point before merger. Using universal relations connecting the masses and spins of uniformly rotating neutron stars, we estimate the spin, $0.49 \lesssim \chi \lesssim 0.68$, of the secondary -- a quantity not constrained so far by the detection -- and a novel strict lower bound on the maximum mass, $M_{\rm TOV} > 2.08^{+0.04}_{-0.04}\, \,M_{\odot}$, of nonrotating neutron stars, consistent with recent observations of a very massive pulsar. The new lower bound also remains valid even in the less likely scenario in which the secondary neutron star never collapsed to a black hole.

A lower bound on the maximum mass if the secondary in GW190814 was once a rapidly spinning neutron star