49 research outputs found
First results of the Laser-Interferometric Detector for Axions (LIDA)
We present the operating principle and the first observing run of a novel
kind of direct detector for axions and axion-like particles in the galactic
halo. Our experiment is sensitive to the polarisation rotation of linearly
polarised laser light induced by an axion field, and the first detector of its
kind collecting science data. We discuss our current peak sensitivity of
GeV (95 % confidence level) to the axion-photon
coupling strength in the axion mass range of 1.97-2.01 neV which is, for
instance, motivated by supersymmetric grand-unified theories. We also report on
effects that arise in our high-finesse in-vacuum cavity at unprecedented
optical continuous-wave intensity. Our detector already belongs to the most
sensitive direct searches within its measurement band, and our first results
pave the way towards surpassing the current sensitivity limits in the mass
range from eV down to eV via quantum-enhanced laser
interferometry
GWTC-2.1: Deep Extended Catalog of Compact Binary Coalescences Observed by LIGO and Virgo During the First Half of the Third Observing Run
The second Gravitational-Wave Transient Catalog reported on 39 compact binary coalescences observed by the Advanced LIGO and Advanced Virgo detectors between 1 April 2019 15:00 UTC and 1 October 2019 15:00 UTC. We present GWTC-2.1, which reports on a deeper list of candidate events observed over the same period. We analyze the final version of the strain data over this period with improved calibration and better subtraction of excess noise, which has been publicly released. We employ three matched-filter search pipelines for candidate identification, and estimate the astrophysical probability for each candidate event. While GWTC-2 used a false alarm rate threshold of 2 per year, we include in GWTC-2.1, 1201 candidates that pass a false alarm rate threshold of 2 per day. We calculate the source properties of a subset of 44 high-significance candidates that have an astrophysical probability greater than 0.5. Of these candidates, 36 have been reported in GWTC-2. If the 8 additional high-significance candidates presented here are astrophysical, the mass range of events that are unambiguously identified as binary black holes (both objects ≥3M⊙) is increased compared to GWTC-2, with total masses from ∼14M⊙ for GW190924_021846 to ∼182M⊙ for GW190426_190642. The primary components of two new candidate events (GW190403_051519 and GW190426_190642) fall in the mass gap predicted by pair instability supernova theory. We also expand the population of binaries with significantly asymmetric mass ratios reported in GWTC-2 by an additional two events (the mass ratio is less than 0.65 and 0.44 at 90% probability for GW190403_051519 and GW190917_114630 respectively), and find that 2 of the 8 new events have effective inspiral spins χeff>0 (at 90% credibility), while no binary is consistent with χeff < 0 at the same significance
Design and sensitivity of a 6-axis seismometer for gravitational wave observatories
We present the design, control system, and noise analysis of a 6-axis
seismometer comprising a mass suspended by a single fused silica fibre. We
utilise custom-made, compact Michelson interferometers for the readout of the
mass motion relative to the table and successfully overcome the sensitivity of
existing commercial seismometers by over an order of magnitude in the angular
degrees of freedom. We develop the sensor for gravitational-wave observatories,
such as LIGO, Virgo, and KAGRA, to help them observe intermediate-mass black
holes, increase their duty cycle, and improve localisation of sources. Our
control system and its achieved sensitivity makes the sensor suitable for other
fundamental physics experiments, such as tests of semiclassical gravity,
searches for bosonic dark matter, and studies of the Casimir force
AIMS - A new tool for stellar parameter determinations using asteroseismic constraints
A key aspect in the determination of stellar properties is the comparison of
observational constraints with predictions from stellar models. Asteroseismic
Inference on a Massive Scale (AIMS) is an open source code that uses Bayesian
statistics and a Markov Chain Monte Carlo approach to find a representative set
of models that reproduce a given set of classical and asteroseismic
constraints. These models are obtained by interpolation on a pre-calculated
grid, thereby increasing computational efficiency. We test the accuracy of the
different operational modes within AIMS for grids of stellar models computed
with the Li\`ege stellar evolution code (main sequence and red giants) and
compare the results to those from another asteroseismic analysis pipeline,
PARAM. Moreover, using artificial inputs generated from models within the grid
(assuming the models to be correct), we focus on the impact on the precision of
the code when considering different combinations of observational constraints
(individual mode frequencies, period spacings, parallaxes, photospheric
constraints,...). Our tests show the absolute limitations of precision on
parameter inferences using synthetic data with AIMS, and the consistency of the
code with expected parameter uncertainty distributions. Interpolation testing
highlights the significance of the underlying physics to the analysis
performance of AIMS and provides caution as to the upper limits in parameter
step size. All tests demonstrate the flexibility and capability of AIMS as an
analysis tool and its potential to perform accurate ensemble analysis with
current and future asteroseismic data yields.Comment: Accepted for publication in MNRAS. 17 pages, 17 figure