1,490 research outputs found
Empirically extending the range of validity of parameter-space metrics for all-sky searches for gravitational-wave pulsars
All-sky searches for gravitational-wave pulsars are generally limited in
sensitivity by the finite availability of computing resources. Semicoherent
searches are a common method of maximizing search sensitivity given a fixed
computing budget. The work of Wette and Prix [Phys. Rev. D 88, 123005 (2013)]
and Wette [Phys. Rev. D 92, 082003 (2015)] developed a semicoherent search
method which uses metrics to construct the banks of pulsar signal templates
needed to search the parameter space of interest. In this work we extend the
range of validity of the parameter-space metrics using an empirically-derived
relationship between the resolution (or mismatch) of the template banks and the
mismatch of the overall search. This work has important consequences for the
optimization of metric-based semicoherent searches at fixed computing cost.Comment: 14 pages, 5 figures, 4 table
Lattice template placement for coherent all-sky searches for gravitational-wave pulsars
All-sky, broadband, coherent searches for gravitational-wave pulsars are
restricted by limited computational resources. Minimizing the number of
templates required to cover the search parameter space, of sky position and
frequency evolution, is one important way to reduce the computational cost of a
search. We demonstrate a practical algorithm which, for the first time,
achieves template placement with a minimal number of templates for an all-sky
search, using the reduced supersky parameter-space metric of Wette and Prix
[Phys. Rev. D 88, 123005 (2013)]. The metric prescribes a constant template
density in the signal parameters, which permits that templates be placed at the
vertices of a lattice. We demonstrate how to ensure complete coverage of the
parameter space, including in particular at its boundaries. The number of
templates generated by the algorithm is compared to theoretical estimates, and
to previous predictions by Brady et al. [Phys. Rev. D 57, 2101 (1998)]. The
algorithm may be applied to any search parameter space with a constant template
density, which includes semicoherent searches and searches targeting known
low-mass X-ray binaries.Comment: 16 pages, 14 figure
Parameter-space metric for all-sky semicoherent searches for gravitational-wave pulsars
The sensitivity of all-sky searches for gravitational-wave pulsars is
primarily limited by the finite availability of computing resources.
Semicoherent searches are a widely-used method of maximizing sensitivity to
gravitational-wave pulsars at fixed computing cost: the data from a
gravitational-wave detector are partitioned into a number of segments, each
segment is coherently analyzed, and the analysis results from each segment are
summed together. The generation of template banks for the coherent analysis of
each segment, and for the summation, requires knowledge of the metrics
associated with the coherent and semicoherent parameter spaces respectively. We
present a useful approximation to the semicoherent parameter-space metric,
analogous to that presented in Wette and Prix [Phys. Rev. D 88, 123005 (2013)]
for the coherent metric. The new semicoherent metric is compared to previous
work in Pletsch [Phys. Rev. D 82, 042002 (2010)], and Brady and Creighton
[Phys. Rev. D 61, 082001 (2000)]. We find that semicoherent all-sky searches
require orders of magnitude more templates than previously predicted.Comment: 21 pages, 13 figures, 2 table
A fast, reliable algorithm for computing frequency responses of state space models
Computation of frequency responses for large order systems described by time invariant state space systems often provides a bottleneck in control system analysis. It is shown that banding the A-matrix in the state space model can effectively reduce the computation time for such systems while maintaining reliability in the results produced
Flat parameter-space metric for all-sky searches for gravitational-wave pulsars
All-sky, broadband, coherent searches for gravitational-wave pulsars are
computationally limited. It is therefore important to make efficient use of
available computational resources, notably by minimizing the number of
templates used to cover the signal parameter space of sky position and
frequency evolution. For searches over the sky, however, the required template
density (determined by the parameter-space metric) is different at each sky
position, which makes it difficult in practice to achieve an efficient
covering. Previous work on this problem has found various choices of sky and
frequency coordinates that render the parameter-space metric approximately
constant, but which are limited to coherent integration times of either less
than a few days, or greater than several months. These limitations restrict the
sensitivity achievable by hierarchical all-sky searches, and hinder the
development of follow-up pipelines for interesting gravitational-wave pulsar
candidates. We present a new flat parameter-space metric approximation, and
associated sky and frequency coordinates, that do not suffer from these
limitations. Furthermore, the new metric is numerically well-conditioned, which
facilitates its practical use.Comment: 19 pages, 20 figure
A Deep Pulse Search in Eleven Low Mass X-Ray Binaries
We present a systematic coherent X-ray pulsation search in eleven low mass
X-ray binaries (LMXBs). We select a relatively broad variety of LMXBs,
including persistent and transient sources and spanning orbital periods between
0.3 and 17 hours. We use about 3.6 Ms of data collected by the Rossi X-Ray
Timing Explorer (RXTE) and XMM-Newton and apply a semi-coherent search strategy
to look for weak and persistent pulses in a wide spin frequency range. We find
no evidence for X-ray pulsations in these systems and consequently set upper
limits on the pulsed sinusoidal semi-amplitude between 0.14% and 0.78% for ten
outbursting/persistent LMXBs and 2.9% for a quiescent system. These results
suggest that weak pulsations might not form in (most) non-pulsating LMXBs.Comment: submitted to ApJ, 8 page
- …