Pulsar timing arrays

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Pulsar timing arrays

This content has been downloaded from IOPscience. Please scroll down to see the full text. 2013 Class. Quantum Grav. 30 220301 (http://iopscience.iop.org/0264-9381/30/22/220301) View the table of contents for this issue, or go to the journal homepage for more Download details: IP Address: 176.31.55.104 This content was downloaded on 21/06/2017 at 17:32 Please note that terms and conditions apply.

You may also be interested in: PRACTICAL METHODS FOR CONTINUOUS GRAVITATIONAL WAVE DETECTION USING PULSAR TIMING J. A. Ellis, F. A. Jenet and M. A. McLaughlin DATA Status update of the Parkes pulsar timing array J P W Verbiest, M Bailes, N D R Bhat et al. A COHERENT METHOD FOR THE DETECTION AND PARAMETER ESTIMATION OF CONTINUOUS GRAVITATIONAL SIGNALS USING AWAVE PULSAR TIMING ARRAY Yan Wang, Soumya D. Mohanty and Fredrick A. Jenet NANOGRAV CONSTRAINTS ON GRAVITATIONAL WAVE BURSTS WITH MEMORY Z. Arzoumanian, A. Brazier, S. Burke-Spolaor et al. OPTIMAL STRATEGIES FOR CONTINUOUS GRAVITATIONAL WAVE DETECTION IN PULSAR TIMING J. A. Ellis, X. Siemens and J. D. E. Creighton ARRAYS GRAVITATIONAL WAVES FROM INDIVIDUAL SUPERMASSIVE BLACK HOLE BINARIES IN CIRCULAR ORBITS: FROM THE LIMITS NORTH AMERICAN NANOHERTZ OBSERVATORY FOR GRAVITATIONAL WAVES Z. Arzoumanian, A. Brazier, S. Burke-Spolaor et al. A Bayesian analysis pipeline for continuous GW sources in the PTA band J A Ellis The European Pulsar Timing Array R D Ferdman, R van Haasteren, C G Bassa et al. OPTIMIZING PULSAR TIMING ARRAYS TO MAXIMIZE GRAVITATIONAL WAVE SINGLE-SOURCE DETECTION: Brian J. Burt, Andrea A FIRST N.CUT Lommen and Lee S. Finn

IOP PUBLISHING

CLASSICAL AND QUANTUM GRAVITY

Class. Quantum Grav. 30 (2013) 220301 (2pp)

doi:10.1088/0264-9381/30/22/220301

EDITORIAL

Pulsar timing arrays Within a decade of the discovery of pulsars in the late sixties, it was recognized that these exotic astrophysical phenomena might serve as tools to detect another exotic astrophysical phenomenon: gravitational waves (GWs). The time of arrival (TOA) of a pulse is modified if a gravitational wave passes between the pulsar at emission and the Earth at reception. That gravitational wave will, of course, affect the TOAs not only from a single pulsar, but for TOAs from pulsars from all directions in the sky. Many of the noise sources that limit the precision of pulsar timing are not correlated for different pulsars and different directions. It was understood from the beginning, therefore, that the best hope for detecting GWs this way lay in using an array of pulsars in different sky directions. The concept of detection via such a pulsar timing array (PTA) is now entering the realm of practicality, or at least plausibility, at the same time that Earth-based laser interferometers, LIGO, VIRGO and others, may be at the brink of detection, and at a time that plans for spacebased interferometers are moving haltingly forward. These three approaches address very different ranges of GW frequency, Earth-based around 100 Hz, space-based around 10−3 Hz, and PTAs below 10−7 Hz, so GW detection with each approach would bring very different information about the Universe and its contents. There is, of course, the undeniable motivation to be the first to make a direct detection of GWs. In the case of the pulsar community this has led to the formation of consortia of scientists: the Parkes (PPTA), the North American (NANOGRAV), and European (EPTA) groups, together with their international collaboration in the International Pulsar Timing Array (IPTA). This science-driven self-organization may turn out to be a model of scientific cooperation. There is a hope within the PTA community that these scientists can detect GWs within five years, most plausibly a stochastic background of GWs from binary supermassive black holes. Whether that hope can be fulfilled depends for one thing on achieving a timing precision of several tens of nanoseconds. The barriers to this are both in the Earth telescopes and their electronics and in the heavens, especially the inherent noise in the pulsar mechanism and the extent to which the effects of the interstellar medium (ISM) can be mitigated. PTA success also depends on the cooperation of nature, cooperation beyond providing strong GW sources. The more pulsars available, the bigger the array and the better the chances are of GW detection. But only around 1% of the known pulsars have acceptable features for achieving the needed timing accuracy. A search for GWs therefore involves a current search for more pulsars. If more pulsars can be found, if improved data algorithms are found for dealing with the ISM, if better electronic backends are developed, and if enough time is available on big radio telescopes around the world, gravitational waves will be detected by PTAs within five years. These are all big “Ifs”. This focus issue is a guide for watching during those years. The issue begins with an article that describes the fundamental techniques of pulsar timing and the effects of gravitational radiation, followed by five articles describing the current challenges: searches for suitable pulsars, noise limitations and data analysis techniques. Five articles then describe the current status of the PTA consortia, along with the status of the 0264-9381/13/220301+02$33.00

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Class. Quantum Grav. 30 (2013) 220301

Editorial

Square Kilometer Array and its potential contribution to PTA. The remaining five articles are devoted to the astrophysics of sources of GWs in this frequency band and the potential for testing general relativity using PTA. M A Bizouard, F Jenet, R Price and C M Will Guest Editors

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