The tidal deformability probability distribution extracted from GW170817 alone, or including multi-messenger information, is confronted to astrophysical and nuclear physics additional constraints within a semi-agnostic approach for the dense matter equation of state. We use Bayesian statistics to combine together low density nuclear physics data, such as the ab-initio predictions based on $χ$EFT interactions or the isoscalar giant monopole resonance, and astrophysical constraints from neutron stars, such as the maximum mass of neutron stars or the probability density function of the tidal deformability $\tildeΛ$ obtained from the GW170817 event. The posteriors probability distribution functions are marginalized over several nuclear empirical parameters ($L_\textrm{sym}$, $K_\textrm{sym}$, $Q_\textrm{sat}$ and $Q_\textrm{sym}$), as well as over observational quantities such as the $1.4M_\odot$ radius $R_{1.4}$ and the pressure at twice the saturation density $P(2n_\textrm{sat})$. The correlations between $L_\textrm{sym}$ and $K_\textrm{sym}$ and between $K_\textrm{sat}$ and $Q_\textrm{sat}$ are also further analyzed. Tension is found between the posteriors: the first one is localized in the tidal deformability probability distribution itself, depending whether multi-messenger analysis is included or not, and the second one is between the observational data and the nuclear physics inputs. These tensions impact the predictions for $L_\textrm{sym}$, $K_\textrm{sym}$ and $R_{1.4}$ with centroids which differ by 2-3$σ$. Implications for the nuclear equation of state are also discussed.
We review the prospects for detecting quark matter in neutron star cores. We survey the proposed signatures and emphasize the importance of data from neutron star mergers, which provide access to dynamical properties that operate on short timescales that are not probed by other neutron star observables.
Measurement of macroscopic properties of neutron stars, whether in binary or in an isolated system, provides us a key opportunity to place a stringent constraint on its equation of state. In this paper, we perform Bayesian model-selection on a wide variety of neutron star equation of state using multi-messenger observations. In particular, (i) we use the mass and tidal deformability measurement from two binary neutron star merger event, GW170817 and GW190425; (ii) simultaneous mass-radius measurement of PSR J0030+0451 and PSR J0740+6620 by NICER collaboration, while the latter has been analyze…
Post-Merger Gravitational-Wave Uncertainties of Binary Neutron Stars under Multi-Messenger EOS Constraints
Key Laboratory of Dark Matter and Space Astronomy, Purple Mountain Observatory, Chinese Academy of Science（暗物质与空间天文重点实验室，中国科学院紫金山天文台）；RIKEN Center for Interdisciplinary Theoretical and Mathematical Sciences (iTHEMS), RIKEN（理化学研究所跨学科理论与数学科学中心（iTHEMS））；International College and Graduate School of Science, The University of Osaka（大阪大学国际理工学部研究生院）
Observations of neutron-star mergers based on distinct messengers, including gravitational waves and electromagnetic signals, can be used to study the behavior of matter denser than an atomic nucleus, and to measure the expansion rate of the Universe described by the Hubble constant. We perform a joint analysis of the gravitational-wave signal GW170817 with its electromagnetic counterparts AT2017gfo and GRB170817A, and the gravitational-wave signal GW190425, both originating from neutron-star mergers. We combine these with previous measurements of pulsars using X-ray and radio observations, an…
With the first multi-messenger observation of a binary neutron star merger (GW170817) new constraints became available for masses and radii of neutron stars. We introduce a class of hybrid EoS that fulfils all these constraints and predicts a region in the mass-radius diagram that could be populated only by hybrid neutron stars with quark matter cores. A confirmation of this conjecture would be provided when the NICER radius measurement for the high-mass pulsar PSR J0740+6620 yields a radius less than 11 km. Would this radius measurement yield a result in excess of 12 km, this would allow for …
We present a rapid analytic framework for predicting kilonova light curves following neutron star (NS) mergers, where the main input parameters are binary-based properties measurable by gravitational wave detectors (chirp mass and mass ratio, orbital inclination) and properties dependent on the nuclear equation of state (tidal deformability, maximum NS mass). This enables synthesis of a kilonova sample for any NS source population, or determination of the observing depth needed to detect a live kilonova given gravitational wave source parameters in low latency. We validate this code, implement…
Using hydrodynamical simulations for a large set of high-density matter equations of state (EoSs) we systematically determine the threshold mass M_thres for prompt black-hole formation in equal-mass and asymmetric neutron star (NS) mergers. We devise the so far most direct, general and accurate method to determine the unknown maximum mass of nonrotating NSs from merger observations revealing M_thres. Considering hybrid EoSs with hadron-quark phase transition, we identify a new, observable signature of quark matter in NS mergers. Furthermore, our findings have direct applications in gravitation…
The study of the equation-of-state (EoS) describing the properties of nuclear matter away from the normal conditions is a relevant and intriguing topic of modern nuclear physics. The last decades have witnessed a substantial experimental progress in derivation of the symmetric matter term of the EoS and of the so-called symmetry energy for the asymmetric matter, especially at densities below the saturation point. But it is only in recent years that the opening of the multi-messenger astronomy era, triggered by detection of gravitational waves due to the neutron star mergers, has renewed and en…
At very high densities, electrons react with protons to form neutron rich matter. This material is central to many fundamental questions in nuclear physics and astrophysics. Moreover, neutron rich matter is being studied with an extraordinary variety of new tools such as the Facility for Rare Isotope Beams (FRIB) and the Laser Interferometer Gravitational Wave Observatory (LIGO). We describe the Lead Radius Experiment (PREX) that uses parity violating electron scattering to measure the neutron radius in $^{208}$Pb. This has important implications for neutron stars and their crusts. We discuss …
In the past few years, new observations of neutron stars and neutron-star mergers have provided a wealth of data that allow one to constrain the equation of state of nuclear matter at densities above nuclear saturation density. However, most observations were based on neutron stars with masses of about 1.4 solar masses, probing densities up to $\sim$ 3-4 times the nuclear saturation density. Even higher densities are probed inside massive neutron stars such as PSR J0740+6620. Very recently, new radio observations provided an update to the mass estimate for PSR J0740+6620 and X-ray observations…
We investigate the possibility that GW170817 has not been the merger of two conventional neutron stars (NS) but involved at least one if not two hybrid stars with a quark matter core which might even belong to a third family of compact stars. To this end, we develop a Bayesian analysis method for selecting the most probable equation of state (EoS) under a set of constraints from compact star physics, which now also include the tidal deformability from GW170817 and the first result for the mass and radius determination for PSR J0030+0451 by NICER. We apply this method for the first time to a tw…
Binary neutron stars in the next-generation era: Multi-messenger detection prospects and constraints on the equation of state, mass distribution, and cosmology
University of Potsdam（波茨坦大学）；Utrecht University（乌得勒支大学）；Nikhef（尼黑核物理研究所）；Max Planck Institute for Gravitational Physics (Albert Einstein Institute)（马克斯·普朗克引力物理研究所（爱因斯坦研究所））；University of Ferrara（费拉拉大学）；INFN, Sezione di Ferrara（意大利国家核物理学院费拉拉分部）；INAF, Osservatorio Astronomico d’Abruzzo（意大利国家天体物理研究所阿布鲁佐天文台）
