Dense magnetized plasma associated with a fast radio burst

Abstract

Fast radio bursts are bright, unresolved, non-repeating, broadband, millisecond flashes, found primarily at high Galactic latitudes, with dispersion measures much larger than expected for a Galactic source. The inferred all-sky burst rate is comparable to the core-collapse supernova rate out to redshift 0.5. If the observed dispersion measures are assumed to be dominated by the intergalactic medium, the sources are at cosmological distances with redshifts of 0.2 to 1 (refs 10 and 11). These parameters are consistent with a wide range of source models. One fast burst revealed circular polarization of the radio emission, but no linear polarization was detected, and hence no Faraday rotation measure could be determined. Here we report the examination of archival data revealing Faraday rotation in the fast radio burst FRB 110523. Its radio flux and dispersion measure are consistent with values from previously reported bursts and, accounting for a Galactic contribution to the dispersion and using a model of intergalactic electron density, we place the source at a maximum redshift of 0.5. The burst has a much higher rotation measure than expected for this line of sight through the Milky Way and the intergalactic medium, indicating magnetization in the vicinity of the source itself or within a host galaxy. The pulse was scattered by two distinct plasma screens during propagation, which requires either a dense nebula associated with the source or a location within the central region of its host galaxy. The detection in this instance of magnetization and scattering that are both local to the source favours models involving young stellar populations such as magnetars over models involving the mergers of older neutron stars, which are more likely to be located in low-density regions of the host galaxy.

A repeating fast radio burst

“…This is strong evidence that a single astronomical source is responsible for the events. In addition, the ∼ 0.002 DM index uncertainty we calculate for Burst 11 (see Methods) is slightly less than that reported for FRB 110523 8 , making this the most precise determination of dispersion index for any FRB thus far. The upper bound on the dispersion index is identical to that of FRB 110523 8 , and hence, following the same arguments used there, Burst 11 provides a similar lower limit of 10 AU for the size of the dispersive region.…”

“…Some FRBs have shown clear evidence for multi-path propagation from scattering by the intervening interstellar or extragalactic material along the line of sight 2,[6][7][8] . However, the burst profiles from FRB 121102 show no obvious evidence for asymmetry from multi-path propagation.…”

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Fast Radio Bursts are millisecond-duration astronomical radio pulses of unknown physical origin that appear to come from extragalactic distances [1][2][3][4][5][6][7][8] . Previous follow-up observations have failed to find additional bursts at the same dispersion measures (i.e.

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A New Electron-Density Model for Estimation of Pulsar and FRB Distances

“…For the host galaxy, scattering could arise in the ISM along the path (see, e.g., Cordes et al 2016;Xu & Zhang 2016) or in the immediate environs of the FRB source (see, e.g., Masui et al 2015). Because of the extremely small lever-arm factor…”

Sky reconstruction for the Tianlai cylinder array

“…A forecast for its capability in measuring dark energy and constrain primordial non-Gaussianity can be found in Xu et al (2015). In addition to the redshifted 21 cm intensity mapping observation, such surveys may also be used for other observations, such as 21cm absorber (Yu et al 2014), fast radio burst (FRB) (Masui et al 2015;Connor et al 2016), and electromagnetic counter part of gravitational wave events (Feng et al 2014).…”