Radio Transients: An antediluvian review

📝 Abstract

We are at the dawn of a new golden age for radio astronomy, with a new generation of facilities under construction and the global community focussed on the Square Kilometre Array as its goal for the next decade. These new facilities offer orders of magnitude improvements in survey speed compared to existing radio telescopes and arrays. Furthermore, the study of transient and variable radio sources, and what they can tell us about the extremes of astrophysics as well as the state of the diffuse intervening media, have been embraced as key science projects for these new facilities. In this paper we review the studies of the populations of radio transients made to date, largely based upon archival surveys. Many of these radio transients and variables have been found in the image plane, and their astrophysical origin remains unclear. We take this population and combine it with sensitivity estimates for the next generation arrays to demonstrate that in the coming decade we may find ourselves detecting 10^5 image plane radio transients per year, providing a vast and rich field of research and an almost limitless set of targets for multiwavelength follow up.

💡 Analysis

We are at the dawn of a new golden age for radio astronomy, with a new generation of facilities under construction and the global community focussed on the Square Kilometre Array as its goal for the next decade. These new facilities offer orders of magnitude improvements in survey speed compared to existing radio telescopes and arrays. Furthermore, the study of transient and variable radio sources, and what they can tell us about the extremes of astrophysics as well as the state of the diffuse intervening media, have been embraced as key science projects for these new facilities. In this paper we review the studies of the populations of radio transients made to date, largely based upon archival surveys. Many of these radio transients and variables have been found in the image plane, and their astrophysical origin remains unclear. We take this population and combine it with sensitivity estimates for the next generation arrays to demonstrate that in the coming decade we may find ourselves detecting 10^5 image plane radio transients per year, providing a vast and rich field of research and an almost limitless set of targets for multiwavelength follow up.

📄 Content

arXiv:1112.2579v1 [astro-ph.HE] 12 Dec 2011 Bull. Astr. Soc. India (2011) 00, 1–19 Radio Transients: An antediluvian review R. P. Fender∗, and M. E. Bell†, School of Physics & Astronomy, University of Southampton Received 1st June 2021 Abstract. We are at the dawn of a new golden age for radio astronomy, with a new generation of facilities under construction and the global community focussed on the Square Kilometre Array as its goal for the next decade. These new facilities offer orders of magnitude improvements in survey speed compared to existing radio tele- scopes and arrays. Futhermore, the study of transient and variable radio sources, and what they can tell us about the extremes of astrophysics as well as the state of the diffuse intervening media, have been embraced as key science projects for these new facilities. In this paper we review the studies of the populations of radio transients made to date, largely based upon archival surveys. Many of these radio transients and variables have been found in the image plane, and their astrophysical origin remains unclear. We take this population and combine it with sensitivity estimates for the next generation arrays to demonstrate that in the coming decade we may find ourselves de- tecting 105 image plane radio transients per year, providing a vast and rich field of research and an almost limitless set of targets for multiwavelength follow up. Keywords : Radio Astronomy – Transients 1. Radio transients: the potential The Universe is a violent and dynamic environment, in which the explosions of massive stars can outshine an entire galaxy, supermassive black holes swallow stars whole, merging neutron stars cause ripples in the fabric of spacetime and bursts of ultra-high energy radiation which can be detected at vast distances, and particles are accelerated to energies far surpassing anything possible in laboratories on the Earth. The extremes of physics – density, temperature, pressure, velocity, gravitational and magnetic fields – experienced in these environments provide a unique ∗email: r.fender@soton.ac.uk †email: meb1w07@soton.ac.uk 2 R.P. Fender and M.E. Bell glimpse at the laws of physics operating in extraordinary regimes. Such ‘extreme astrophysics’, is a high priority for global research in the 21st century1. In the second half of the 20th cen- tury, astronomy moved beyonds its optical origins into the radio, infrared, ultraviolet, X-ray and gamma-ray bands. The most extreme environments in the Universe betray themselves by their copious high-energy emission, in the X-ray and gamma-ray bands, and also by their radio emis- sion. Strong magnetic fields and shock waves as matter collides in the ambient medium, result in radio bursts from electrons (and positrons) spiralling around, and sometimes being channelled along, these magnetic field lines. Wide-field orbiting X- and gamma-ray observatories, with all- sky monitors, have revealed our Galaxy to be a hotbed of explosive and relativistic effects, which go largely unnoticed by traditional optical telescopes both because they are missed in the narrow fields of view, and are obscured by interstellar dust. By far the best way to observe and understand the violent Universe from the ground is via the radio emission which is ubiquitously associated with these violent events. The emission arises as the shocked particles glow with synchrotron radiation, streaming along and around magnetic field lines, or are induced to move and emit co- herently, producing extremely bright bursts. However, in the past radio astronomy, like optical astronomy, has suffered from the narrow fields of view which are a consequence of large dishes, and cannot survey the sky sufficiently rapidly to detect rare and rapid events, which may be the most significant astrophysically. All of this is about to change, with a new generation of radio telescopes, taking advantage of new technology and the vast advances made in data transport and computer processing, connecting large numbers of small detectors, able to deliver enormous fields of view. Finally the age of the radio all-sky monitors is here. What is more, these radio all-sky monitors will have several advantages over the traditional X-ray and gamma-ray monit- ors: they will be able to localise events immediately with arcsec precision, and will be able to go significantly deeper / further. As we shall demonstrate in this review, our current understanding of the population of radio transients implies that we should detect thousands, or even millions, of such events with ‘next generation’ radio facilities such as The Low-Frequency Array (LOFAR), The South African Ka- roo Array Telescope (MeerKAT) and The Australian SKA Pathfinder (ASKAP), and ultimately the Square Kilometre Array (SKA). As well as drawing our attention to the extremes of astro- physics, these sources are potentially observable to vast distances (possibly as far as the Epoch of Reionisation at redshift z > 6) and will turn out to be a

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