Forecast constraints on cosmic strings from future CMB, pulsar timing, and gravitational wave direct detection experiments

ABSTRACT Cosmic strings are potential gravitational-wave (GW) sources that can be probed by pulsar timing arrays (PTAs). In this work we develop a detection algorithm for a GW burst from a cusp on a cosmic string, and apply it to Parkes PTA data. We find four events with a false alarm probability less than 1 per cent. However further investigation shows that all of these are likely to be spurious. As there are no convincing detections we place upper limits on the GW amplitude for different event durations. From these bounds we place limits on the cosmic string tension of Gμ ∼ 10−5, and highlight that this bound is independent from those obtained using other techniques. We discuss the physical implications of our results and the prospect of probing cosmic strings in the era of Square Kilometre Array.

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Constraining the nanohertz gravitational wave background with the Parkes Pulsar Timing Array

Proceedings of the International Astronomical Union ◽

10.1017/s174392131202354x ◽

2012 ◽

Vol 8 (S291) ◽

pp. 177-177

Author(s):

Ryan Shannon

Keyword(s):

Gravitational Wave ◽

Gravitational Waves ◽

Direct Detection ◽

Massive Black Hole ◽

Black Hole Binaries ◽

Pulsar Timing ◽

The Galaxy ◽

Gravitational Wave Background ◽

Pulsar Timing Array ◽

The Universe

AbstractThe direct detection of gravitational waves will usher in a new era of astrophysics, enabling the study of regions of the universe opaque to electromagnetic radiation or electromagnetically quiet. An ensemble of pulsars (referred to as a pulsar timing array) provides a set of clocks distributed across the Galaxy sensitive to gravitational waves with periods on the order of five years (frequencies of many nanohertz). Plausible source of gravitational waves in this frequency band include massive black hole binaries in the throes of mergers and oscillating cosmic strings. The stochastic gravitational wave background, the sum of gravitational waves emitted throughout the universe, is the most likely signal to be detected by a pulsar timing array.While the detection of gravitational waves will be a milestone in pulsar astronomy, a constraining limit on the strength of the gravitational wave background can be used to constrain cosmological models and early Universe physics. Here we present a new algorithm that can be used to constrain the strength of the GWB with a pulsar timing array. We then apply this technique to Parkes Pulsar Timing Array observations and place a new limit on the strength of the GWB. We conclude by discussing the astrophysical implications of this limit and the prospects for detecting gravitational waves with pulsars.

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Gravitational wave astronomy: needle in a haystack

Philosophical Transactions of The Royal Society A Mathematical Physical and Engineering Sciences ◽

10.1098/rsta.2011.0540 ◽

2013 ◽

Vol 371 (1984) ◽

pp. 20110540 ◽

Cited By ~ 6

Author(s):

Neil J Cornish

Keyword(s):

Gravitational Wave ◽

Strong Field ◽

Direct Detection ◽

Dynamical Regime ◽

New Era ◽

Pulsar Timing ◽

Astrophysical Objects ◽

Model Spaces ◽

Instrument Noise ◽

Non Gaussian

A worldwide array of highly sensitive ground-based interferometers stands poised to usher in a new era in astronomy with the first direct detection of gravitational waves. The data from these instruments will provide a unique perspective on extreme astrophysical objects, such as neutron stars and black holes, and will allow us to test Einstein’s theory of gravity in the strong field, dynamical regime. To fully realize these goals, we need to solve some challenging problems in signal processing and inference, such as finding rare and weak signals that are buried in non-stationary and non-Gaussian instrument noise, dealing with high-dimensional model spaces, and locating what are often extremely tight concentrations of posterior mass within the prior volume. Gravitational wave detection using space-based detectors and pulsar timing arrays bring with them the additional challenge of having to isolate individual signals that overlap one another in both time and frequency. Promising solutions to these problems will be discussed, along with some of the challenges that remain.

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Gravitational-Wave Detection Using Pulsars: Status of the Parkes Pulsar Timing Array Project

Publications of the Astronomical Society of Australia ◽

10.1071/as08023 ◽

2009 ◽

Vol 26 (2) ◽

pp. 103-109 ◽

Cited By ~ 49

Author(s):

G. B. Hobbs ◽

M. Bailes ◽

N. D. R. Bhat ◽

S. Burke-Spolaor ◽

D. J. Champion ◽

...

Keyword(s):

Gravitational Wave ◽

Gravitational Waves ◽

Direct Detection ◽

Low Frequency ◽

Current Status ◽

Binary Black Holes ◽

Gravitational Wave Detection ◽

Wave Detection ◽

Pulsar Timing ◽

Pulsar Timing Array

AbstractThe first direct detection of gravitational waves may be made through observations of pulsars. The principal aim of pulsar timing-array projects being carried out worldwide is to detect ultra-low frequency gravitational waves (f ∼ 10−9–10−8 Hz). Such waves are expected to be caused by coalescing supermassive binary black holes in the cores of merged galaxies. It is also possible that a detectable signal could have been produced in the inflationary era or by cosmic strings. In this paper, we review the current status of the Parkes Pulsar Timing Array project (the only such project in the Southern hemisphere) and compare the pulsar timing technique with other forms of gravitational-wave detection such as ground- and space-based interferometer systems.

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Stochastic gravitational-wave background from metastable cosmic strings

Journal of Cosmology and Astroparticle Physics ◽

10.1088/1475-7516/2021/12/006 ◽

2021 ◽

Vol 2021 (12) ◽

pp. 006

Author(s):

Wilfried Buchmüller ◽

Valerie Domcke ◽

Kai Schmitz

Keyword(s):

Gravitational Wave ◽

Cosmic Strings ◽

Long Strings ◽

Wave Spectrum ◽

Cosmic Time ◽

String Tension ◽

Relevant Parameter ◽

Pulsar Timing ◽

Near Future ◽

Gravitational Wave Background

Abstract A metastable cosmic-string network is a generic consequence of many grand unified theories (GUTs) when combined with cosmic inflation. Metastable cosmic strings are not topologically stable, but decay on cosmic time scales due to pair production of GUT monopoles. This leads to a network consisting of metastable long strings on superhorizon scales as well as of string loops and segments on subhorizon scales. We compute for the first time the complete stochastic gravitational-wave background (SGWB) arising from all these network constituents, including several technical improvements to both the derivation of the loop and segment contributions. We find that the gravitational waves emitted by string loops provide the main contribution to the gravitational-wave spectrum in the relevant parameter space. The resulting spectrum is consistent with the tentative signal observed by the NANOGrav and Parkes pulsar timing collaborations for a string tension of G μ ∼ 10-11…-7 and has ample discovery space for ground- and space-based detectors. For GUT-scale string tensions, G μ ∼ 10-8…-7, metastable strings predict a SGWB in the LIGO-Virgo-KAGRA band that could be discovered in the near future.

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