TY - JOUR
T1 - Neutron-Star Radius from a Population of Binary Neutron Star Mergers
AU - Bose, Sukanta
AU - Chakravarti, Kabir
AU - Rezzolla, Luciano
AU - Sathyaprakash, B. S.
AU - Takami, Kentaro
N1 - Funding Information:
We have presented a new method to infer the average radius of a population of neutron stars in BNSs that employs both the inspiral-merger and the postmerger phases. The postmerger allows for the measurement of the compactness, which complements the measurement of the component masses from the inspiral to determine the radius. Our modeling of the postmerger can help produce complete inspiral, merger and postmerger time-domain waveforms. It may be argued that our results are somewhat limited for a couple of reasons. First, our phenomenological fits and the estimates of the errors Δ f 1 , 2 are given for binaries with mass ratio q ≃ 1 . However, we have found that similar fits can be obtained for unequal mass ratios studied in Ref. [17] , and that Δ f 1 , 2 are very similar in such cases for signals with the same SNRs. This observation is consistent with those made in Ref. [18] . If nature relents to provide us with an especially strong signal, such that the network SNR of the postmerger signal is ≈ 6.4 , which can happen if the source is of optimal orientation and sky position and located at a distance of 30 Mpc, then our method can be used to deduce the radius to about 1.6%, at 90% confidence level. Second, as the number of observed binaries increases and the fractional errors of the EOS properties decrease, the systematic uncertainties, mostly related to the accuracy of NR calculations, will dominate. The average numerical error from the simulations is ∼ 0.1 kHz , while the average uncertainty for the identification of peak frequencies is ∼ 0.2 kHz [13,24] . Third, we ignored the effect of spins, which can increase the total-mass error [33] , and therefore the effectiveness of the stacking method. They can also change f 2 by 0.2–0.3 kHz in the most extreme cases [34,35] . While this is comparable to the NR uncertainty, it is important that spin effects be properly incorporated in future simulations. (For more details on the quasiuniversal relations and parameter-estimation methods employed in this work, see the Supplemental Material [27] , which includes Refs. [36–39] .) Finally, since both the imprint of EOS and the signals themselves may be weak, it will be important to utilize as much of the signal as is meaningful for measuring the EOS parameters. This can be especially helpful owing to the possibility that these parameters may have nontrivial covariances with other parameters, such as their masses. EOS estimation would therefore gain from exploring if the same EOS parameter values can explain consistently features in all parts of the waveform—specifically, the inspiral and the postmerger waveforms. It is a pleasure to thank J. Clark, B. Lackey, and J. Read for reading the manuscript and providing useful input. Support comes from NSF Grants (No. PHY-1206108 and No. PHY-1506497); ERC Synergy Grant “BlackHoleCam” (No. 610058); “NewCompStar”; COST Action No. MP1304; the LOEWE Program in HIC for FAIR; the European Union’s Horizon 2020 Research and Innovation Programme (No. 671698) (call FETHPC-1-2014, project ExaHyPE); JSPS KAKENHI Grants (No. 15H06813 and No. 17K14305); and the Navajbai Ratan Tata Trust. The simulations were performed on SuperMUC at LRZ-Munich, on LOEWE at CSC-Frankfurt, and on Hazelhen at HLRS in Stuttgart.
Funding Information:
Support comes from NSF Grants (No. PHY-1206108 and No. PHY-1506497); ERC Synergy Grant BlackHoleCam (No. 610058); NewCompStar; COST Action No. MP1304; the LOEWE Program in HIC for FAIR; the European Union's Horizon 2020 Research and Innovation Programme (No. 671698) (call FETHPC-1-2014, project ExaHyPE); JSPS KAKENHI Grants (No. 15H06813 and No. 17K14305); and the Navajbai Ratan Tata Trust
Publisher Copyright:
© 2018 American Physical Society.
PY - 2018/1/16
Y1 - 2018/1/16
N2 - We show how gravitational-wave observations with advanced detectors of tens to several tens of neutron-star binaries can measure the neutron-star radius with an accuracy of several to a few percent, for mass and spatial distributions that are realistic, and with none of the sources located within 100 Mpc. We achieve such an accuracy by combining measurements of the total mass from the inspiral phase with those of the compactness from the postmerger oscillation frequencies. For estimating the measurement errors of these frequencies, we utilize analytical fits to postmerger numerical relativity waveforms in the time domain, obtained here for the first time, for four nuclear-physics equations of state and a couple of values for the mass. We further exploit quasiuniversal relations to derive errors in compactness from those frequencies. Measuring the average radius to well within 10% is possible for a sample of 100 binaries distributed uniformly in volume between 100 and 300 Mpc, so long as the equation of state is not too soft or the binaries are not too heavy. We also give error estimates for the Einstein Telescope.
AB - We show how gravitational-wave observations with advanced detectors of tens to several tens of neutron-star binaries can measure the neutron-star radius with an accuracy of several to a few percent, for mass and spatial distributions that are realistic, and with none of the sources located within 100 Mpc. We achieve such an accuracy by combining measurements of the total mass from the inspiral phase with those of the compactness from the postmerger oscillation frequencies. For estimating the measurement errors of these frequencies, we utilize analytical fits to postmerger numerical relativity waveforms in the time domain, obtained here for the first time, for four nuclear-physics equations of state and a couple of values for the mass. We further exploit quasiuniversal relations to derive errors in compactness from those frequencies. Measuring the average radius to well within 10% is possible for a sample of 100 binaries distributed uniformly in volume between 100 and 300 Mpc, so long as the equation of state is not too soft or the binaries are not too heavy. We also give error estimates for the Einstein Telescope.
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U2 - 10.1103/PhysRevLett.120.031102
DO - 10.1103/PhysRevLett.120.031102
M3 - Article
C2 - 29400541
AN - SCOPUS:85040723943
VL - 120
JO - Physical Review Letters
JF - Physical Review Letters
SN - 0031-9007
IS - 3
M1 - 031102
ER -