We present a method for assigning a statistical significance to detection candidates in targeted searches for continuous gravitational waves from known pulsars, without assuming the detector noise is Gaussian and stationary. We take advantage of the
expected Doppler phase modulation of the signal induced by Earths orbital motion, as well as the amplitude modulation induced by Earths spin, to effectively blind the search to real astrophysical signals from a given location in the sky. We use this sky-shifting to produce a large number of noise-only data realizations to empirically estimate the background of a search and assign detection significances, in a similar fashion to the use of timeslides in searches for compact binaries. We demonstrate the potential of this approach by means of simulated signals, as well as hardware injections into real detector data. In a study of simulated signals in non-Gaussian noise, we find that our method outperforms another common strategy for evaluating detection significance. We thus demonstrate that this and similar techniques have the potential to enable a first confident detection of continuous gravitational waves.
Gravitational waves (GWs) can offer a novel window into the structure and dynamics of neutron stars. Here we present the first search for long-duration quasi-monochromatic GW transients triggered by pulsar glitches. We focus on two glitches observed
in radio timing of the Vela pulsar (PSR J0835-4510) on 12 December 2016 and the Crab pulsar (PSR J0534+2200) on 27 March 2017, during the Advanced LIGO second observing run (O2). We assume the GW frequency lies within a narrow band around twice the spin frequency as known from radio observatons. Using the fully-coherent transient-enabled F-statistic method to search for transients of up to four months in length. We find no credible GW candidates for either target, and through simulated signal injections we set 90% upper limits on (constant) GW strain as a function of transient duration. For the larger Vela glitch, we come close to beating an indirect upper limit for when the total energy liberated in the glitch would be emitted as GWs, thus demonstrating that similar post-glitch searches at improved detector sensitivity can soon yield physical constraints on glitch models.
This Python module provides an interface for querying the Australia Telescope National Facility (ATNF) pulsar catalogue (Manchester et al. 2005). The intended users are astronomers wanting to extract data from the catalogue through a script rather th
an having to download and parse text tables output using the standard web interface. It allows users to access information, such as pulsar frequencies and sky locations, on all pulsars in the catalogue. Querying of the catalogue can easily be incorporated into Python scripts.
This document describes a code to perform parameter estimation and model selection in targeted searches for continuous gravitational waves from known pulsars using data from ground-based gravitational wave detectors. We describe the general workings
of the code and characterise it on simulated data containing both noise and simulated signals. We also show how it performs compared to a previous MCMC and grid-based approach to signal parameter estimation. Details how to run the code in a variety of cases are provided in Appendix A.
The direct detection of gravitational waves provides the opportunity to measure fundamental aspects of gravity which have never been directly probed before, including the polarization of gravitational waves. In the context of searches for continuous
waves from known pulsars, we present novel methods to detect signals of any polarization content, measure the modes present and place upper-limits on the amplitude of non-tensorial components. This will allow us to obtain new model-independent, dynamical constraints on deviations from general relativity. We test this framework on multiple potential sources using simulated data from three advanced-era detectors at design sensitivity. We find that signals of any polarization will become detectable and distinguishable for characteristic strains $hgtrsim 3times10^{-27} sqrt{1~{rm yr}/T}$, for an observation time $T$. We also find that our ability to detect non-tensorial components depends only on the power present in those modes, irrespective of the strength of the tensorial strain.
Rapidly rotating neutron stars are promising sources of continuous gravitational wave radiation for the LIGO and Virgo interferometers. The majority of neutron stars in our galaxy have not been identified with electromagnetic observations. All-sky se
arches for isolated neutron stars offer the potential to detect gravitational waves from these unidentified sources. The parameter space of these blind all-sky searches, which also cover a large range of frequencies and frequency derivatives, presents a significant computational challenge. Different methods have been designed to perform these searches within acceptable computational limits. Here we describe the first benchmark in a project to compare the search methods currently available for the detection of unknown isolated neutron stars. We employ a mock data challenge to compare the ability of each search method to recover signals simulated assuming a standard signal model. We find similar performance among the short duration search methods, while the long duration search method achieves up to a factor of two higher sensitivity. We find the absence of second derivative frequency in the search parameter space does not degrade search sensivity for signals with physically plausible second derivative frequencies. We also report on the parameter estimation accuracy of each search method, and the stability of the sensitivity in frequency, frequency derivative and in the presence of detector noise.
We present an improved method of targeting continuous gravitational-wave signals in data from the LIGO and Virgo detectors with a higher efficiency than the time-domain Bayesian pipeline used in many previous searches. Our spectral interpolation algo
rithm, SplInter, removes the intrinsic phase evolution of the signal from source rotation and relative detector motion. We do this in the frequency domain and generate a time series containing only variations in the signal due to the antenna pattern. Although less flexible than the classic heterodyne approach, SplInter allows for rapid analysis of putative signals from isolated (and some binary) pulsars, and efficient follow-up searches for candidate signals generated by other search methods. The computational saving over the heterodyne approach can be many orders of magnitude, up to a factor of around fifty thousand in some cases, with a minimal impact on overall sensitivity for most targets.
The sudden spin-down in the rotation of magnetar 1E 2259+586 observed by Archibald et al. (2013) was a rare event. However this particular event, referred to as an anti-glitch, was followed by another event which Archibald et al. (2013) suggested cou
ld either be a conventional glitch or another anti-glitch. Although there is no accompanied radiation activity or pulse profile change, there is decisive evidence for the existence of the second timing event, judging from the timing data. We apply Bayesian Model Selection to quantitatively determine which of these possibilities better explains the observed data. We show that the observed data strongly supports the presence of two successive anti-glitches with a Bayes Factor, often called the odds ratio, greater than 40. Furthermore, we show that the second anti-gtlich has an associated frequency change $Delta u$ of $-8.2 times 10^{-8}$ Hz. We discuss the implications of these results for possible physical mechanisms behind this anti-glitch.
We open the discussion into how the Laser Interferometer Space Antenna (LISA) observations of supermassive black-hole (SMBH) mergers (in the mass range ~10^6-10^8 Msun) may be complementary to pulsar timing-based gravitational wave searches. We consi
der the toy model of determining pulsar distances by exploiting the fact that LISA SMBH inspiral observations can place tight parameter constraints on the signal present in pulsar timing observations. We also suggest, as a future path of research, the use of LISA ring-down observations from the most massive (>~ a few 10^7 Msun) black-hole mergers, for which the inspiral stage will lie outside the LISA band, as both a trigger and constraint on searches within pulsar timing data for the inspiral stage of the merger.
