scholarly journals Identifying Quark Matter in Hybrid Stars through Relativistic Tidal Deformations

Universe ◽  
2019 ◽  
Vol 5 (9) ◽  
pp. 193
Author(s):  
Bryen Irving ◽  
Thomas Klähn ◽  
Prashanth Jaikumar ◽  
Marc Salinas ◽  
Wei Wei
Keyword(s):  
Neutron Star ◽  
Parameter Space ◽  
Quark Matter ◽  
Specific Model ◽  
Nuclear Model ◽  
Hartree Fock ◽  
Binary Neutron Star ◽  
Merger Event ◽  
Hybrid Stars ◽  
Parameter Ranges

We study a specific model of neutron star matter that supports a phase transition to quark matter at high density and examine parameter ranges for consistency with the mass-weighted tidal deformability of Λ ˜ = 300 − 230 + 420 for a mass ratio of q ∈ [ 0.73 , 1.0 ] , as inferred from observations of gravitational waves from the binary neutron star merger event GW170817. By using this observation to restrict the parameter space for the equation of state (EoS) model used throughout this study, we aim to assess the possibility of a potential solution to the masquerade and flavor camouflage problems for hybrid EoS models. Assuming the two stars have the same EoS, in which the Dirac-Brueckner-Hartree Fock (DBHF) nuclear model transitions to the vBag quark model, we see if the parameter space of these hybrid model stars are restricted due to the adherence to the reported Λ 1.4 ∈ 70 , 580 and M m a x ∈ [ 2.01 , 2.16 ] M ⊙ constraints. Upon completion, we find that, while the parameter space for our model does get restricted, it does not ultimately resolve the masquerade and flavor camouflage problems.

scholarly journals Gamma-Ray Bursts and Binary Neutron Star Mergers

1996 ◽  
Vol 165 ◽  
pp. 489-502
Author(s):  
Tsvi Piran
Keyword(s):  
Neutron Star ◽  
Gravitational Radiation ◽  
Gamma Ray ◽  
Indirect Evidence ◽  
Gamma Ray Bursts ◽  
Binary Neutron Star ◽  
Merger Event ◽  
Γ Rays ◽  
Γ Ray ◽  
The One

Neutron star binaries, such as the one observed in the famous binary pulsar PSR 1913+16, end their life in a catastrophic merger event (denoted here NS2M). The merger releases ∼5 1053 ergs, mostly as neutrinos and gravitational radiation. A small fraction of this energy suffices to power γ-ray bursts (GRBs) at cosmological distances. Cosmological GRBs must pass, however, an optically thick fireball phase and the observed γ rays emerge only at the end of this phase. Hence, it is difficult to determine the nature of the source from present observations (the agreement between the rates of GRBs and NS2Ms providing only indirect evidence for this model). In the future a coinciding detection of a GRB and a gravitational-radiation signal could confirm this model.

scholarly journals LOFAR 144-MHz follow-up observations of GW170817

2020 ◽  
Vol 494 (4) ◽  
pp. 5110-5117
Author(s):  
J W Broderick ◽  
T W Shimwell ◽  
K Gourdji ◽  
A Rowlinson ◽  
S Nissanke ◽  
...  
Keyword(s):  
Neutron Star ◽  
Low Frequency ◽  
Radio Spectrum ◽  
Central Frequency ◽  
Binary Neutron Star ◽  
Upper Limit ◽  
Upper Limits ◽  
Maximum Elevation ◽  
Merger Event

ABSTRACT We present low-radio-frequency follow-up observations of AT 2017gfo, the electromagnetic counterpart of GW170817, which was the first binary neutron star merger to be detected by Advanced LIGO–Virgo. These data, with a central frequency of 144 MHz, were obtained with LOFAR, the Low-Frequency Array. The maximum elevation of the target is just 13${_{.}^{\circ}}$7 when observed with LOFAR, making our observations particularly challenging to calibrate and significantly limiting the achievable sensitivity. On time-scales of 130–138 and 371–374 d after the merger event, we obtain 3σ upper limits for the afterglow component of 6.6 and 19.5 mJy beam−1, respectively. Using our best upper limit and previously published, contemporaneous higher frequency radio data, we place a limit on any potential steepening of the radio spectrum between 610 and 144 MHz: the two-point spectral index $\alpha ^{610}_{144} \gtrsim$ −2.5. We also show that LOFAR can detect the afterglows of future binary neutron star merger events occurring at more favourable elevations.

scholarly journals SU(2) Chiral Sigma Model Study of Phase Transition in Hybrid Stars

2003 ◽  
Vol 18 (30) ◽  
pp. 2135-2145 ◽  
Author(s):  
P. K. Jena ◽  
L. P. Singh
Keyword(s):  
Phase Transition ◽  
Neutron Star ◽  
Nuclear Matter ◽  
Quark Matter ◽  
Sigma Model ◽  
Maximum Mass ◽  
Model Study ◽  
Stable Solutions ◽  
Hybrid Stars ◽  
Matter Component

We use a modified SU(2) chiral sigma model to study nuclear matter component and simple bag model for quark matter constituting a neutron star. We also study the phase transition of nuclear matter to quark matter with the mixed phase characterized by two conserved charges in the interior of highly dense neutron stars. Stable solutions of Tolman–Oppenheimer–Volkoff equations representing hybrid stars are obtained with a maximum mass of 1.67M⊙ and radius around 8.9 km.

scholarly journals Collimated outflows from long-lived binary neutron star merger remnants

2020 ◽  
Vol 495 (1) ◽  
pp. L66-L70 ◽  
Author(s):  
Riccardo Ciolfi
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Gamma Ray ◽  
Gamma Ray Bursts ◽  
Spin Axis ◽  
Binary Neutron Star ◽  
Physical Conditions ◽  
Massive Neutron Star ◽  
Merger Event ◽  
First Time

ABSTRACT The connection between short gamma-ray bursts (SGRBs) and binary neutron star (BNS) mergers was recently confirmed by the association of GRB 170817A with the merger event GW170817. However, no conclusive indications were obtained on whether the merger remnant that powered the SGRB jet was an accreting black hole (BH) or a long-lived massive neutron star (NS). Here, we explore the latter case via BNS merger simulations covering up to 250 ms after merger. We report, for the first time in a full merger simulation, the formation of a magnetically driven collimated outflow along the spin axis of the NS remnant. For the system at hand, the properties of such an outflow are found largely incompatible with an SGRB jet. With due consideration of the limitations and caveats of our present investigation, our results favour a BH origin for GRB 170817A and SGRBs in general. Even though this conclusion needs to be confirmed by exploring a larger variety of physical conditions, we briefly discuss possible consequences of all SGRB jets being powered by accreting BHs.

scholarly journals Detecting the Hadron-Quark Phase Transition with Gravitational Waves

Universe ◽  
2019 ◽  
Vol 5 (6) ◽  
pp. 156 ◽  
Author(s):  
Matthias Hanauske ◽  
Luke Bovard ◽  
Elias Most ◽  
Jens Papenfort ◽  
Jan Steinheimer ◽  
...  
Keyword(s):  
Phase Transition ◽  
Neutron Star ◽  
Equation Of State ◽  
Gravitational Wave ◽  
Compact Star ◽  
Binary Neutron Star ◽  
Interesting Part ◽  
Merger Event ◽  
Tidal Deformations ◽  
Quark Phase

The long-awaited detection of a gravitational wave from the merger of a binary neutron star in August 2017 (GW170817) marks the beginning of the new field of multi-messenger gravitational wave astronomy. By exploiting the extracted tidal deformations of the two neutron stars from the late inspiral phase of GW170817, it is now possible to constrain several global properties of the equation of state of neutron star matter. However, the most interesting part of the high density and temperature regime of the equation of state is solely imprinted in the post-merger gravitational wave emission from the remnant hypermassive/supramassive neutron star. This regime was not observed in GW170817, but will possibly be detected in forthcoming events within the current observing run of the LIGO/VIRGO collaboration. Numerous numerical-relativity simulations of merging neutron star binaries have been performed during the last decades, and the emitted gravitational wave profiles and the interior structure of the generated remnants have been analysed in detail. The consequences of a potential appearance of a hadron-quark phase transition in the interior region of the produced hypermassive neutron star and the evolution of its underlying matter in the phase diagram of quantum cromo dynamics will be in the focus of this article. It will be shown that the different density/temperature regions of the equation of state can be severely constrained by a measurement of the spectral properties of the emitted post-merger gravitational wave signal from a future binary compact star merger event.

scholarly journals The heavier the better: how to constrain mass ratios and spins of high-mass neutron star mergers

2020 ◽  
Vol 496 (1) ◽  
pp. L16-L21 ◽  
Author(s):  
Elias R Most ◽  
Lukas R Weih ◽  
Luciano Rezzolla
Keyword(s):  
Black Hole ◽  
Neutron Star ◽  
Lower Bound ◽  
Equations Of State ◽  
High Mass ◽  
Maximum Mass ◽  
Mass Ratio ◽  
Effective Spin ◽  
Binary Neutron Star ◽  
Merger Event

ABSTRACT The first binary neutron star merger event, GW170817, and its bright electromagnetic counterpart have provided a remarkable amount of information. By contrast, the second event, GW190425, with $M_{\rm tot}=3.4^{+0.3}_{-0.1}\, \mathrm{ M}_{\odot }$ and the lack of an electromagnetic counterpart, has hardly improved our understanding of neutron star physics. While GW190425 is compatible with a scenario in which the merger has led to a prompt collapse to a black hole and little ejected matter to power a counterpart, determining the mass ratio and the effective spin $\tilde{\chi }$ of the binary remains difficult. This is because gravitational waveforms cannot yet well constrain the component spins of the binary. However, since the mass of GW190425 is significantly larger than the maximum mass for non-rotating neutron stars, $M_{_{\rm TOV}}$, the mass ratio q cannot be too small, as the heavier star would not be gravitationally stable. Making use of universal relations and a large number of equations of state, we provide limits in the $(\tilde{\chi },q)$ plane for GW190425, namely qmin ≥ 0.38 and $\tilde{\chi }_{\rm max}\le 0.20$, assuming $M_\mathrm{tot} \simeq 3.4\, \mathrm{ M}_\odot$. Finally, we show how future observations of high-mass binaries can provide a lower bound on $M_{_{\rm TOV}}$.

scholarly journals Contraction of cold neutron star due to in the presence a quark core

2019 ◽  
Vol 79 (10) ◽  
Author(s):  
B. Eslam Panah ◽  
T. Yazdizadeh ◽  
G. H. Bordbar
Keyword(s):  
Neutron Star ◽  
Neutron Stars ◽  
Quark Matter ◽  
Average Density ◽  
Dynamical Stability ◽  
Hadronic Matter ◽  
Maximum Mass ◽  
Quark Core ◽  
Hybrid Stars ◽  
Schwarzschild Radius

Abstract Motivated by importance of the existence of quark matter on structure of neutron star. For this purpose, we use a suitable equation of state (EoS) which include three different parts: (i) a layer of hadronic matter, (ii) a mixed phase of quarks and hadrons, and, (iii) a strange quark matter in the core. For this system, in order to do more investigation of the EoS, we evaluate energy, Le Chatelier’s principle and stability conditions. Our results show that the EoS satisfies these conditions. Considering this EoS, we study the effect of quark matter on the structure of neutron stars such as maximum mass and the corresponding radius, average density, compactness, Kretschmann scalar, Schwarzschild radius, gravitational redshift and dynamical stability. Also, considering the mentioned EoS in this paper, we find that the maximum mass of hybrid stars is a little smaller than that of the corresponding pure neutron star. Indeed the maximum mass of hybrid stars can be quite close to the pure neutron stars. Our calculations about the dynamical stability show that these stars are stable against the radial adiabatic infinitesimal perturbations. In addition, our analyze indicates that neutron stars are under a contraction due to the existence of quark core.

scholarly journals Equation of state of dense nuclear matter and neutron star structure from nuclear chiral interactions

2018 ◽  
Vol 609 ◽  
pp. A128 ◽  
Author(s):  
Ignazio Bombaci ◽  
Domenico Logoteta
Keyword(s):  
Neutron Star ◽  
Equation Of State ◽  
Neutron Stars ◽  
Nuclear Matter ◽  
Symmetric Nuclear Matter ◽  
Heavy Nuclei ◽  
Hartree Fock ◽  
Binary Neutron Star ◽  
Dense Nuclear Matter ◽  
Three Body

Aims. We report a new microscopic equation of state (EOS) of dense symmetric nuclear matter, pure neutron matter, and asymmetric and β-stable nuclear matter at zero temperature using recent realistic two-body and three-body nuclear interactions derived in the framework of chiral perturbation theory (ChPT) and including the Δ(1232) isobar intermediate state. This EOS is provided in tabular form and in parametrized form ready for use in numerical general relativity simulations of binary neutron star merging. Here we use our new EOS for β-stable nuclear matter to compute various structural properties of non-rotating neutron stars. Methods. The EOS is derived using the Brueckner–Bethe–Goldstone quantum many-body theory in the Brueckner–Hartree–Fock approximation. Neutron star properties are next computed solving numerically the Tolman–Oppenheimer–Volkov structure equations. Results. Our EOS models are able to reproduce the empirical saturation point of symmetric nuclear matter, the symmetry energy Esym, and its slope parameter L at the empirical saturation density n0. In addition, our EOS models are compatible with experimental data from collisions between heavy nuclei at energies ranging from a few tens of MeV up to several hundreds of MeV per nucleon. These experiments provide a selective test for constraining the nuclear EOS up to ~4n0. Our EOS models are consistent with present measured neutron star masses and particularly with the mass M = 2.01 ± 0.04 M⊙ of the neutron stars in PSR J0348+0432.

scholarly journals Compact radio emission indicates a structured jet was produced by a binary neutron star merger

Science ◽  
2019 ◽  
Vol 363 (6430) ◽  
pp. 968-971 ◽  
Author(s):  
G. Ghirlanda ◽  
O. S. Salafia ◽  
Z. Paragi ◽  
M. Giroletti ◽  
J. Yang ◽  
...  
Keyword(s):  
Neutron Star ◽  
Very Long Baseline Interferometry ◽  
High Spatial Resolution ◽  
Apparent Size ◽  
Source Size ◽  
Global Network ◽  
Binary Neutron Star ◽  
Long Baseline ◽  
Relativistic Jet ◽  
Merger Event

The binary neutron star merger event GW170817 was detected through both electromagnetic radiation and gravitational waves. Its afterglow emission may have been produced by either a narrow relativistic jet or an isotropic outflow. High-spatial-resolution measurements of the source size and displacement can discriminate between these scenarios. We present very-long-baseline interferometry observations, performed 207.4 days after the merger by using a global network of 32 radio telescopes. The apparent source size is constrained to be smaller than 2.5 milli–arc seconds at the 90% confidence level. This excludes the isotropic outflow scenario, which would have produced a larger apparent size, indicating that GW170817 produced a structured relativistic jet. Our rate calculations show that at least 10% of neutron star mergers produce such a jet.

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