More Like this

1. Detecting the Hadron-Quark Phase Transition with Gravitational Waves

   https://doi.org/10.3390/universe5060156  

   Hanauske, Matthias; Bovard, Luke; Most, Elias; Papenfort, Jens; Steinheimer, Jan; Motornenko, Anton; Vovchenko, Volodymyr; Dexheimer, Veronica; Schramm, Stefan; Stöcker, Horst (June 2019, Universe)

   null (Ed.)

   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. 

   more » « less
2. Implications of the search for optical counterparts during the first six months of the Advanced LIGO’s and Advanced Virgo’s third observing run: possible limits on the ejecta mass and binary properties

   https://doi.org/10.1093/mnras/stz3457  

   Coughlin, Michael W.; Dietrich, Tim; Antier, Sarah; Bulla, Mattia; Foucart, Francois; Hotokezaka, Kenta; Raaijmakers, Geert; Hinderer, Tanja; Nissanke, Samaya (December 2019, Monthly Notices of the Royal Astronomical Society)

   ABSTRACT GW170817 showed that neutron star mergers not only emit gravitational waves but also can release electromagnetic signatures in multiple wavelengths. Within the first half of the third observing run of the Advanced LIGO and Virgo detectors, there have been a number of gravitational wave candidates of compact binary systems for which at least one component is potentially a neutron star. In this article, we look at the candidates S190425z, S190426c, S190510g, S190901ap, and S190910h, predicted to have potentially a non-zero remnant mass, in more detail. All these triggers have been followed up with extensive campaigns by the astronomical community doing electromagnetic searches for their optical counterparts; however, according to the released classification, there is a high probability that some of these events might not be of extraterrestrial origin. Assuming that the triggers are caused by a compact binary coalescence and that the individual source locations have been covered during the EM follow-up campaigns, we employ three different kilonova models and apply them to derive possible constraints on the matter ejection consistent with the publicly available gravitational-wave trigger information and the lack of a kilonova detection. These upper bounds on the ejecta mass can be related to limits on the maximum mass of the binary neutron star candidate S190425z and to constraints on the mass-ratio, spin, and NS compactness for the potential black hole–neutron star candidate S190426c. Our results show that deeper electromagnetic observations for future gravitational wave events near the horizon limit of the advanced detectors are essential. 

   more » « less
3. The impact of the crust equation of state on the analysis of GW170817

   https://doi.org/10.1088/1361-6382/ab5ba4  

   Gamba, R.; Read, J. S.; Wade, L. E. (December 2019, Classical and Quantum Gravity)

   Abstract The detection of GW170817, the first neutron star-neutron star merger observed by Advanced LIGO and Virgo, and its following analyses represent the first contributions of gravitational wave data to understanding dense matter. Parameterizing the high density section of the equation of state of both neutron stars through spectral decomposition, and imposing a lower limit on the maximum mass value, led to an estimate of the stars’ radii ofkm andkm (Abbottet al2018Phys. Rev. Lett.121161101). These values do not, however, take into account any uncertainty owed to the choice of the crust low-density equation of state, which was fixed to reproduce the SLy equation of state model (Douchin and Haensel 2001Astron. Astrophys.380151). We here re-analyze GW170817 data and establish that different crust models do not strongly impact the mass or tidal deformability of a neutron star—it is impossible to distinguish between low-density models with gravitational wave analysis. However, the crust does have an effect on inferred radius. We predict the systematic error due to this effect using neutron star structure equations, and compare the prediction to results from full parameter estimation runs. For GW170817, this systematic error affects the radius estimate by 0.3 km, approximatelyof the neutron stars’ radii. 

   more » « less
4. Multimessenger constraints on the neutron-star equation of state and the Hubble constant

   https://doi.org/10.1126/science.abb4317  

   Dietrich, Tim; Coughlin, Michael W.; Pang, Peter T. H.; Bulla, Mattia; Heinzel, Jack; Issa, Lina; Tews, Ingo; Antier, Sarah (December 2020, Science)

   Observations of neutron-star mergers with 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 as quantified by the Hubble constant. We performed a joint analysis of the gravitational-wave event GW170817 with its electromagnetic counterparts AT2017gfo and GRB170817A, and the gravitational-wave event GW190425, both originating from neutron-star mergers. We combined these with previous measurements of pulsars using x-ray and radio observations, and nuclear-theory computations using chiral effective field theory, to constrain the neutron-star equation of state. We found that the radius of a 1.4–solar mass neutron star is ${11.75}_{-0.81}^{+0.86}$km at 90% confidence and the Hubble constant is ${66.2}_{-4.2}^{+4.4}$at 1σ uncertainty. 

   more » « less
5. Bayesian inference for gravitational waves from binary neutron star mergers in third-generation observatories

   Rory Smith, Ssohrab Borhanian (August 2021, Physical review letters)

   null (Ed.)

   Third-generation (3G) gravitational-wave detectors will observe thousands of coalescing neutron star binaries with unprecedented fidelity. Extracting the highest precision science from these signals is expected to be challenging owing to both high signal-to-noise ratios and long-duration signals. We demonstrate that current Bayesian inference paradigms can be extended to the analysis of binary neutron star signals without breaking the computational bank. We construct reduced order models for ∼90minute long gravitational-wave signals, covering the observing band (5−2048Hz), speeding up inference by a factor of ∼1.3×10^4 compared to the calculation times without reduced order models. The reduced order models incorporate key physics including the effects of tidal deformability, amplitude modulation due to the Earth's rotation, and spin-induced orbital precession. We show how reduced order modeling can accelerate inference on data containing multiple, overlapping gravitational-wave signals, and determine the speedup as a function of the number of overlapping signals. Thus, we conclude that Bayesian inference is computationally tractable for the long-lived, overlapping, high signal-to-noise-ratio events present in 3G observatories. 

   more » « less