We present the first experimental optical trapping of ytterbium-doped sodium yttrium fluoride (Yb:NaYF4) hexagonal microdisks with a dual-beam dipole trap. These high-aspect-ratio hexagonal microdisks exhibit reduced photon recoil heating due to light scattering while allowing for 10s of kHz mechanical frequencies. These features make them good candidates as force sensors for the Levitated Sensor Detector (LSD) project, which detects high-frequency gravitational waves above the region previously probed by LIGO. We discuss motional dynamics of these microdisks by showing their motional spectra in comparison with analytical and numerical models and the recent progress of 1-meter LSD prototype that is under development at Northwestern University.
Kilometer-scale ground-based gravitational-wave interferometers have generated a new field of astronomy by viewing the universe in gravitational wave (GW) radiation, operating at a peak sensitivity of frequencies ranging from 10s of Hz to a few kHz.1 A great many discoveries have resulted from these detectors, such as the existence of binary black hole and neutron star systems.2 It is of great scientific value to extend the GW search to other frequencies, just as has been the case for the exploration of the EM spectrum. The levitated sensor detector (LSD) is a 1 m tabletop scale high frequency (< 10 kHz) gravitational wave detection experiment currently under construction at Northwestern University.3 It will serve as a 1 m prototype for future generations of levitated mass based instruments. The LSD sensitivity has more favorable frequency scaling at these frequencies compared to laser interferometer detectors such as LIGO and VIRGO due to different limiting noise factors, the LIGO free spectral range, and the fact that the LSD is a resonant sensor. The LSD is sensitive to GWs from binary coalescence of sub-solar-mass primordial black holes and as-yet unexplored new physics in the high-frequency GW window, such as the annihiation of gravitationally bound states of the QCD axion by black hole superradiance. Many promising experiments and techniques exist for probing the GW spectrum below the LIGO frequency band; they include pulsar timing arrays,4, 5 atomic clocks and other interferometers,6, 7 LISA,8, 9 and DECIGO.10 There are also a number of proposals, experiments and initial bounds set above the LIGO frequency band, largely over 100 MHz.11–18 Fewer established methods to systematically probe the kHz-MHz part of the GW spectrum, where a variety of interesting sources could exist. At Northwestern, we are constructing a compact Michelson interferometer configuration with Fabry-P´erot arms as shown in Figure 3, designed to work in the 10-100 kHz band. In the medium and long term, a multi index dielectric stack will be suspended at an anti-node of the standing wave inside each Fabry-P´erot arm. In the short term, this is likely to be a disc or disc like object (discussed in sections 2 and 2.2) — with which a degree of experimental success has already been had. A second laser is used to read out the position of the object as well as cool it along the cavity axes.19
Using the Star Track population synthesis code we compute the distribution of masses of merging compact object (black hole or neutron star) binaries. The shape of the mass distribution is sensitive to some parameters governing the stellar binary evolution. We discuss the possibility of constraining stellar evolution models using mass measurements abtained from detection of compact object inspiral with upcoming gravitational-wave observatories.
The detection of gravitational waves by the first generation of ground-based interferometric detectors, like LIGO, relies on sophisticated data analysis techniques. For the inspiral phase of binary compact objects, the optimal one is the so-called matched-filtering technique. The output of the detector is cross-correlated with a bank of templates. The closer the templates are to the real signal, the higher the S/N of the detection is. In this paper we quantify the loss of S/N that occurs when one tries to detect a precessing binary using non-precessing templates. To do so, we compute the fitting factor which is a measure of the mismatch between the signal and the templates. The precessing signal is obtained using a 1.5 PN analytical approximation of the real solution called simple precession. We found regions of the parameter space for which the detection could be jeopardized if precession is not accounted in the templates. The solution of this problem could be to use more complete templates, that could capture the main features of the precession. Specifically we examine such a family of 'mimic' templates, that requires only three additional parameters, first proposed by Apostolatos. However we find that this family does not recover the main part of the signal. We conclude that a more efficient template family will be needed in the near future.
KEYWORDS: Binary data, Statistical analysis, LIGO, Galactic astronomy, Statistical modeling, Data modeling, Systems modeling, Signal to noise ratio, Stars, Monte Carlo methods
Estimates of the Galactic coalescence rate (R) of close binaries with two neutron stars (NS-NS) are known to be uncertain by large factors (about two orders of magnitude) mainly due to the small number of systems detected as binary radio pulsars. We present an analysis method that allows us to estimate the Galactic NS-NS coalescence using the current observed sample and, importantly, to assign
a statistical significance to these estimates and to calculate the allowed ranges of values at various confidence levels. The method involves the simulation of selection effects inherent in all relevant radio pulsar surveys and a Bayesian statistical analysis for the probability distribution of R. The most likely values for the total Galactic coalescence rate (Rtot) lie in the range 2-60 Myr-1 depending on different pulsar population models. For our reference model 1, where the most likely estimates of pulsar population properties are adopted, we obtain Rtot = 8-5+9 Myr-1 at a 68% statistical confidence level. The corresponding range of expected detection rates of NS-NS inspiral are 3-2+4 × 10-3 yr-1 for the initial LIGO and 18-11+21 yr-1 for the advanced LIGO.
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