Exploring the sensitivity of gravitational wave detectors to neutron star physics

Abstract

The physics of neutron stars can be studied with gravitational waves emitted from coalescing binary systems. Tidal effects become significant during the last few orbits and can be visible in the gravitational-wave spectrum above 500 Hz. After the merger, the neutron star remnant oscillates at frequencies above 1 kHz and can collapse into a black hole. Gravitational-wave detectors with a sensitivity of 10 −24 strain/ √Hz at 2−4 kHz can observe these oscillations from a source which is ∼ 100 Mpc away. The current observatories, such as LIGO and Virgo, are limited by shot noise at high frequencies and have a sensitivity of ≥ 2 × 10 −23 strain/ √Hz at 3 kHz. In this paper, we propose an optical configuration of gravitational-wave detectors which can be set up in present facilities using the current interferometer topology. This scheme has a potential to reach 7 × 10 −25 strain/ √ Hz at 2.5 kHz without compromising the detector sensitivity to black hole binaries. We argue that the proposed instruments have a potential to detect similar amount of post-merger neutron star oscillations as the next generation detectors, such as Cosmic Explorer and Einstein Telescope. We also optimise the arm length of the future detectors for neutron star physics and find that the optimal arm length is ≈ 20 km. These instruments have the potential to observe neutron star post-merger oscillations at a rate of ∼ 30 events per year with a signal-to-noise ratio of 5 or more.

Quantum expander for gravitational-wave observatories

“…The quantum noise at low frequencies (QRPN) will remain unchanged. This differs our approach from other designs targeting the high-frequency sensitivity [44][45][46]. The QRPN can be suppressed independently using already developed approaches using frequency dependent squeezing, variational readout or quantum non-demolition measurements [35][36][37][38].…”

“…χ = 0) in the typical operational range of GW observatories Ω ω s , the input-output relation Eq. (6) reduces to the standard one for a baseline GWO [43,44], with the detection bandwidth given by: γ baseline = ω 2 s /γ = cT ITM /(T SE L arm ). Second, the noise term in Eq.…”

Detection prospects of core-collapse supernovae with supernova-optimized third-generation gravitational-wave detectors

“…The strain sensitivity of the detector does not always improve by scaling the detector as other fundamental sources of noise also change by scaling the length of the detector [56]. As the gravitational wave spectrum of supernovae has some power in a few kilohertz range, we allow the arm length to vary independently similar to the analysis by [53,57]. Our simulations indicated the optimal length to be close to 40 km, the upper bound value allowed for the length parameter.…”

“…We optimize over the length of the signal recycling cavity (L src ) and the transmissivity of the signal recycling mirror (T srm ) to maximize the CCSN detection range. The quantum resonant sidebands can be tuned with these parameters and we exploit this behavior for supernovae tuning similar to the approach used by Buonanno et al [52] and Martynov et al [53].…”

Broadband quantum noise reduction in future long baseline gravitational-wave detectors via EPR entanglement

“…[17], which assumes T SRC 1, starts to break down. We also need to take into account the frequency dependent propagation phase of the sidebands, which leads to the following expression for the coupling constant constant [18]:…”