Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userWas GW190814 a black hole -- strange quark star system?
81
0
0.0
(
0
)
Authors
I. Bombaci
Ask ChatGPT about the research
No Arabic abstract
We investigate the possibility that the low mass companion of the black hole in the source of GW190814 was a strange quark star. This possibility is viable within the so-called two-families scenario in which neutron stars and strange quark stars coexist. Strange quark stars can reach the mass range indicated by GW190814, $Msim (2.5-2.67) M_odot$ due to a large value of the adiabatic index, without the need for a velocity of sound close to the causal limit. Neutron stars (actually hyperonic stars in the two-families scenario) can instead fulfill the presently available astrophysical and nuclear physics constraints which require a softer equation of state. In this scheme it is possible to satisfy both the request of very large stellar masses and of small radii while using totally realistic and physically motivated equations of state. Moreover it is possible to get a radius for a 1.4 $M_odot$ star of the order or less than 11 km, which is impossible if only one family of compact stars exists.
rate research
Read More
The interface effects play important roles for the properties of strange quark matter (SQM) and the related physical processes. We show several examples on the implications of interface effects for both stable and unstable SQM. Based on an equivparticle model and adopting mean-field approximation (MFA), the surface tension and curvature term of SQM can be obtained, which are increasing monotonically with the density of SQM at zero external pressure. For a parameter set constrained according to the 2$M_odot$ strange star, we find the surface tension is $sim$2.4 MeV/fm${}^2$, while it is larger for other cases.
The secondary component of GW190814 with a mass of 2.50-2.67 $M_{odot}$ may be the lightest black hole or the heaviest neutron star ever observed in a binary compact object system. To explore the possible equation of state (EOS), which can support such massive neutron star, we apply the relativistic mean-field model with a density-dependent isovector coupling constant to describe the neutron-star matter. The acceptable EOS should satisfy some constraints: the EOS model can provide a satisfactory description of the nuclei; the maximum mass $M_textrm{TOV}$ is above 2.6 $M_{odot}$; the tidal deformability of a canonical 1.4 $M_{odot}$ neutron star $Lambda_{1.4}$ should lie in the constrained range from GW170817. In this paper, we find that the nuclear symmetry energy and its density dependence play a crucial role in determining the EOS of neutron-star matter. The constraints from the mass of 2.6 $M_{odot}$ and the tidal deformability $Lambda_{1.4}=616_{-158}^{+273}$ (based on the assumption that GW190814 is a neutron star-black hole binary) can be satisfied as the slope of symmetry energy $L leq 50$ MeV. Even including the constraint of $Lambda_{1.4}=190_{-120}^{+390}$ from GW170817 which suppresses the EOS stiffness at low density, the possibility that the secondary component of GW190814 is a massive neutron star cannot be excluded in this study.
Gravitational waves provide a window to probe general relativity (GR) under extreme conditions. The recent observations of GW190412 and GW190814 are unique high-mass-ratio mergers that enable the observation of gravitational-wave harmonics beyond the dominant $(ell, m) = (2, 2)$ mode. Using these events, we search for physics beyond GR by allowing the source parameters measured from the sub-dominant harmonics to deviate from that of the dominant mode. All results are consistent with GR. We constrain the chirp mass as measured by the $(ell, m) = (3, 3)$ mode to be within $0_{-3}^{+5}%$ of the dominant mode when we allow both the masses and spins of the sub-dominant modes to deviate. If we allow only the mass parameters to deviate, we constrain the chirp mass of the $(3, 3)$ mode to be within $pm1%$ of the expected value from GR.
The effect of strange interactions in neutron star matter and the role of the strange meson-hyperon couplings are studied in a relativistic quark model where the confining interaction for quarks inside a baryon is represented by a phenomenological average potential in an equally mixed scalar-vector harmonic form. The hadron-hadron interaction in nuclear matter is then realized by introducing additional quark couplings to $sigma$, $omega$, $rho$, $sigma^*$ and $phi$ mesons through mean-field approximations. The meson-baryon couplings are fixed through the SU(6) spin-flavor symmetry and the SU(3) flavor symmetry to determine the hadronic equation of state (EoS). We find that the SU(3) coupling set gives the potential depth between $Lambda$s around $-5$ MeV and favours a stiffer EoS.The radius for the canonical neutron star lies within a range of $12.7$ to $13.1$ km.
All stellar mass black holes have hitherto been identified by X-rays emitted by gas that is accreting onto the black hole from a companion star. These systems are all binaries with black holes below 30 M$_{odot}$$^{1-4}$. Theory predicts, however, that X-ray emitting systems form a minority of the total population of star-black hole binaries$^{5,6}$. When the black hole is not accreting gas, it can be found through radial velocity measurements of the motion of the companion star. Here we report radial velocity measurements of a Galactic star, LB-1, which is a B-type star, taken over two years. We find that the motion of the B-star and an accompanying H$alpha$ emission line require the presence of a dark companion with a mass of $68^{+11}_{-13}$ M$_{odot}$, which can only be a black hole. The long orbital period of 78.9 days shows that this is a wide binary system. The gravitational wave experiments have detected similarly massive black holes$^{7,8}$, but forming such massive ones in a high-metallicity environment would be extremely challenging to current stellar evolution theories$^{9-11}$.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
