Radio bursts from superconducting strings

Abstract

We show that radio bursts from cusps on superconducting strings are linearly polarized, thus, providing a signature that can be used to distinguish them from astrophysical sources. We write the event rate of string-generated radio transients in terms of observational variables, namely, the event duration and flux. Assuming a canonical set of observational parameters, we find that the burst event rate can be quite reasonable, e.g., order ten a year for Grand Unified strings with 100 TeV currents, and a lack of observed radio bursts can potentially place strong constraints on particle physics models.PACS numbers: 98.80. Cq, 11.27.+d, 95.85.Bh, 95.85.Fm Cosmic strings are possible relics from the early Universe. Their discovery would substantiate our hot big bang cosmological model and also provide tremendous insight into the nature of fundamental interactions.There are a number of different ways to look for cosmic strings, mostly based on their gravitational interactions, and negative searches so far impose constraints on particle physics models and cosmology. If the strings are superconducting [1], their electromagnetic emission provides yet another signature that can be used to search for them. The electromagnetic emission from a cosmic string loop is not steady and can have sharp bursts that can be seen as transient events. In Ref.[2], it was pointed out that it might be fruitful to look for superconducting strings by searching for bursts at radio wavelengths. There is a simple reason for choosing to look in the radio band. Cosmic strings are large objects and their fundamental frequency of emission is very low. The power emitted at higher frequencies generally falls off with increasing harmonic. Thus, there is more power emitted in the radio than in other bands such as the optical. Also, as we shall see in Sec. I, the emission in the burst is beamed, with the beam being widest at lower frequencies. Thus, the event rate in radio bursts can be expected to be larger than those at higher frequencies. On the other hand, propagation effects in the radio band are stronger, and these have to be included when evaluating the signature.Besides superconducting cosmic strings, there are other strong motivations for looking at transient radio phenomenon from pulsars, supernovae, black hole evaporation, gamma-ray bursts, active galactic nuclei, and extra-terrestrial life. A radio burst from a superconducting cosmic string will have to be distinguished among bursts from other potential astrophysical sources. With this in mind, we recalculate the characteristics of the string burst and show that it is linearly polarized in a direction that is independent of the frequency.The feasibility of observations depends on the event * Electronic address: ycai21@asu.edu † Electronic address: Eray.Sabancilar@asu.edu ‡ Electronic address: tvachasp@asu.edu rates for radio bursts. Here, we focus on evaluating the event rate in variables that are most useful to observers. The burst at source occurs with a certain duration and flux. However...

CMB distortions from superconducting cosmic strings

“…If PIXIE does not detect suitable distortions, only light superconducting strings with modest currents (up to ∼ 10 8 GeV), or somewhat heavier strings but with small currents ( 10 4 GeV) will be allowed. Of course, there is a possibility that CMB distortions will be detected, in which case, one needs to look at other distinguishing signatures from superconducting cosmic strings such as neutrino bursts [8] and radio transients [9,10].…”

“…As superconducting strings move through the cosmic magnetized plasma, they can develop and carry large currents, and oscillating loops of superconducting strings will emit copious amounts of electromagnetic radiation and particles mostly as bursts [3,4]. This led to the idea that superconducting strings may be a candidate for the engine driving observed gamma ray bursts [5][6][7], sources of cosmic ray bursts [8] and radio transients [9,10].…”

Constraints on superconducting cosmic strings from early reionization

“…These features lead to the emission of high-energy photons from superconducting cosmic strings. The number of photons emitted from a cusp per unit time per unit frequency is [11] f c !…”

“…Radiation from strings is not isotropic but is most efficient at cusps-parts of a string that move very close to the speed of light-and kinksdiscontinuities in the tangent vector to the string. The strongly beamed radiation has been studied as sources of various observable effects such as gamma ray bursts [8,9], ultrahigh-energy neutrinos [7], radio transients [10][11][12], and distortions of the cosmic microwave background (CMB) [13][14][15][16]. In addition to these signatures that are particular to superconducting strings, there are more generic effects that are gravitational and do not rely on superconductivity.…”

Search for transient gravitational waves in coincidence with short-duration radio transients during 2007–2013

“…A cosmic string cusp may emit gravitational waves with a f −4/3 frequency dependence up to a cutoff frequency [24], potentially at frequencies and amplitudes detectable by ground-based interferometers [5,58]. The same cusps may produce short-duration linearly polarized radio bursts [23], a mechanism that has previously been proposed as the origin of the original Lorimer burst [68]. Unlike GWs from other sources discussed, cosmic string cusps could theoretically produce detectable GWs at cosmological distances, which makes them particularly interesting in the context of Parkes FRBs with Dispersion Measures (DMs) indicative of cosmological distances.…”