Subscribe to the gold package and get unlimited access to Shamra Academy
Register a new userImplications from GW170817 and I-Love-Q relations for relativistic hybrid stars
93
0
0.0
(
0
)
Added by
Vasileios Paschalidis
Publication date
2017
fields
Physics
and research's language is
English
Ask ChatGPT about the research
No Arabic abstract
Gravitational wave observations of GW170817 placed bounds on the tidal deformabilities of compact stars allowing one to probe equations of state for matter at supranuclear densities. Here we design new parametrizations for hybrid hadron-quark equations of state, that give rise to low-mass twin stars, and test them against GW170817. We find that GW170817 is consistent with the coalescence of a binary hybrid star--neutron star. We also test and find that the I-Love-Q relations for hybrid stars in the third family agree with those for purely hadronic and quark stars within $sim 3%$ for both slowly and rapidly rotating configurations, implying that these relations can be used to perform equation-of-state independent tests of general relativity and to break degeneracies in gravitational waveforms for hybrid stars in the third family as well.
rate research
Read More
Neutron stars are expected to have a tight relation between their moment of inertia ($I$), tidal deformability ($lambda$, which is related to the Love number), and rotational mass quadrupole moment ($Q$) that is nearly independent of the unknown equation of state (EoS) of cold dense matter. These and similar relations are often called universal, and they have been used for various applications including analysis of gravitational wave data. We extend these studies using piecewise polytropic representations of dense matter, including for so-called twin stars that have a second branch of stability at high central densities. The second-branch relations are less tight, by a factor of $sim 3$, than the relations found in the first stable branch. We find that the relations on both branches become tighter when we increase the lower limit to the maximum mass for the EoS under consideration. We also propose new empirical relations between $I$, $lambda$, $Q$, and the complex frequency $omega=omega_R+iomega_I$ of the fundamental axial $w$-mode, and find that they are comparably tight to the I-Love-Q correlations.
We propose three scenarios for compact hybrid stars consisting of nuclear and dark matters which could possibly serve as alternative interpretations to the LIGO/Virgo events GW170817 and GW190425. To demonstrate our proposal, we adopt the SLy4 equation of state (EoS) for nuclear matter, and an EoS for a bosonic self-interacting dark matter (SIDM), which is simple and capable of yielding both reasonable halo density and compact stars. We study the mass-radius and tidal Love number (TLN)-mass relations for these compact hybrid stars, and also generalize the Bardeen-Thorne-Meltzer (BTM) criteria to discuss in details the possible saddle instability due to the nature of two-fluid model. Our results show that it is possible for our hybrid star scenarios to explain GW170817 and GW190425. Some of the hybrid stars can have compact neutron or mixed cores around 10km while possessing thick dark matter shells, which can then explain the astrophysical observations of neutron stars with compact photon radius and mass higher than 2 solar masses. Reversely, we also infer the dark matter model from the parameter estimation of GW190425. Our scenarios of compact hybrid stars can be further tested by the coming LIGO/Virgo O3 events.
We use gravitational-wave observations of the binary neutron star merger GW170817 to explore the tidal deformabilities and radii of neutron stars. We perform Bayesian parameter estimation with the source location and distance informed by electromagnetic observations. We also assume that the two stars have the same equation of state; we demonstrate that for stars with masses comparable to the component masses of GW170817, this is effectively implemented by assuming that the stars dimensionless tidal deformabilities are determined by the binarys mass ratio $q$ by $Lambda_1/Lambda_2 = q^6$. We investigate different choices of prior on the component masses of the neutron stars. We find that the tidal deformability and 90$%$ credible interval is $tilde{Lambda}=222^{+420}_{-138}$ for a uniform component mass prior, $tilde{Lambda}=245^{+453}_{-151}$ for a component mass prior informed by radio observations of Galactic double neutron stars, and $tilde{Lambda}=233^{+448}_{-144}$ for a component mass prior informed by radio pulsars. We find a robust measurement of the common areal radius of the neutron stars across all mass priors of $8.9 le hat{R} le 13.2$ km, with a mean value of $langle hat{R} rangle = 10.8$ km. Our results are the first measurement of tidal deformability with a physical constraint on the stars equation of state and place the first lower bounds on the deformability and areal radii of neutron stars using gravitational waves.
Motivated by the recent discoveries of compact objects from LIGO/Virgo observations, we study the possibility of identifying some of these objects as compact stars made of dark matter called dark stars, or the mix of dark and nuclear matters called hybrid stars. In particular, in GW190814, a new compact object with 2.6 $M_{odot}$ is reported. This could be the lightest black hole, the heaviest neutron star, and a dark or hybrid star. In this work, we extend the discussion on the interpretations of the recent LIGO/Virgo events as hybrid stars made of various self-interacting dark matter (SIDM) in the isotropic limit. We pay particular attention to the saddle instability of the hybrid stars which will constrain the possible SIDM models.
We study the dynamical evolution of a phase-transition-induced collapse neutron star to a hybrid star, which consists of a mixture of hadronic matter and strange quark matter. The collapse is triggered by a sudden change of equation of state, which result in a large amplitude stellar oscillation. The evolution of the system is simulated by using a 3D Newtonian hydrodynamic code with a high resolution shock capture scheme. We find that both the temperature and the density at the neutrinosphere are oscillating with acoustic frequency. However, they are nearly 180$^{circ}$ out of phase. Consequently, extremely intense, pulsating neutrino/antineutrino fluxes will be emitted periodically. Since the energy and density of neutrinos at the peaks of the pulsating fluxes are much higher than the non-oscillating case, the electron/positron pair creation rate can be enhanced dramatically. Some mass layers on the stellar surface can be ejected by absorbing energy of neutrinos and pairs. These mass ejecta can be further accelerated to relativistic speeds by absorbing electron/positron pairs, created by the neutrino and antineutrino annihilation outside the stellar surface. The possible connection between this process and the cosmological Gamma-ray Bursts is discussed.
Log in to be able to interact and post comments
comments
Fetching comments
Sign in to be able to follow your search criteria
