Year: 2018
Type: article
Abstract: A binary neutron star coalescence event has recently been observed for the first time in gravitational waves, and many more detections are expected once current ground-based detectors begin operating at design sensitivity. As in the case of binary black holes, gravitational waves generated by binary neutron stars consist of inspiral, merger, and postmerger components. Detecting the latter is important because it encodes information about the nuclear equation of state in a regime that cannot be probed prior to merger. The postmerger signal, however, can only be expected to be measurable by current detectors for events closer than roughly ten megaparsecs, which given merger rate estimates implies a low probability of observation within the expected lifetime of these detectors. We carry out Monte Carlo simulations showing that the dominant postmerger signal (the $\ensuremath{\ell}=m=2$ mode) from individual binary neutron star mergers may not have a good chance of observation even with the most sensitive future ground-based gravitational wave detectors proposed so far (the Einstein Telescope and Cosmic Explorer, for certain equations of state, assuming a full year of operation, the latest merger rates, and a detection threshold corresponding to a signal-to-noise ratio of 5). For this reason, we propose two methods that stack the postmerger signal from multiple binary neutron star observations to boost the postmerger detection probability. The first method follows a commonly used practice of multiplying the Bayes factors of individual events. The second method relies on an assumption that the mode phase can be determined from the inspiral waveform, so that coherent mode stacking of the data from different events becomes possible. We find that both methods significantly improve the chances of detecting the dominant postmerger signal, making a detection very likely after a year of observation with Cosmic Explorer for certain equations of state. We also show that in terms of detection, coherent stacking is more efficient in accumulating confidence for the presence of postmerger oscillations in a signal than the first method. Moreover, assuming the postmerger signal is detected with Cosmic Explorer via stacking, we estimate through a Fisher analysis that the peak frequency can be measured to a statistical error of $\ensuremath{\sim}4--20\text{ }\text{ }\mathrm{Hz}$ for certain equations of state. Such an error corresponds to a neutron star radius measurement to within $\ensuremath{\sim}15--56\text{ }\text{ }\mathrm{m}$, a fractional relative error $\ensuremath{\sim}4%$, suggesting that systematic errors from theoretical modeling $(\ensuremath{\gtrsim}100\text{ }\text{ }\mathrm{m}$) may dominate the error budget.
Language: English
Subfield: Astronomy and Astrophysics
Field: Physics and Astronomy
Domain: Physical Sciences
Open Access status: bronze
Funders: National Science Foundation, National Aeronautics and Space Administration, Simons Foundation, Canadian Institute for Advanced Research, Montana State University, Industry Canada, Institut Périmètre de physique théorique, Natural Sciences and Engineering Research Council of Canada, Japan Society for the Promotion of Science
Awards: CAREER: Gravitational Waves from Compact Binaries as Probes of the Universe, G1237556036, STUDIES OF GAMMA-RAY BURST ENGINES IN FULL GENERAL RELATIVITY WE PROPOSE TO PERFORM MAGNETOHYDRODYNAMIC SIMULATIONS IN FULL GENERAL RELATIVITY OF SH, Dynamical, Strong-field Gravity, G6671297155, A SPACE BASED GRAVITATIONAL WAVE DETECTOR WILL OPEN UP THE SOURCE RICH LOW FREQUENCY PORTION OF THE SPECTRUM THAT CAN NOT BE ACCESSED FROM THE GROUND
OpenAlex ID: W2728165010