Science 5 July 2013:
Vol. 341 no. 6141 pp. 53-56

A Population of Fast Radio Bursts at Cosmological Distances

D. Thornton, B. Stappers, M. Bailes, B. Barsdell, S. Bates, N. D. R. Bhat, M. Burgay, S. Burke-Spolaor, D. J. Champion, P. Coster, N. D'Amico, A. Jameson, S. Johnston, M. Keith, M. Kramer, L. Levin, S. Milia, C. Ng, A. Possenti, W. van Straten | 1 Comments

Radio telescope data revealed four short, extragalactic, nonrepeating bursts of radio emission whose source is unknown. [Also see Perspective by Cordes]

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Thornton et al. reported the discovery of a population of fast radio bursts (FRBs) of apparently extragalactic origin. Their nature has been disputed since the first discovery of a millisecond extragalactic radio burst [1]. Apparently non-thermal, these bursts can be produced by relativistic plasma in different events (core-collapse supernovae, neutron star mergers, etc.). A natural explanation of FRBs can also be related to giant flares from soft gamma-ray repeaters (SGRs), as was suggested by us [2].

SGRs are thought to be strongly magnetized neutron stars, which exhibit regular flaring activity related to strong internal magnetic field dissipation. Energetic giant flares can be related to relativistic magnetized explosions in SGR magnetospheres [3], and appearence of non-thermal radio emission seems natural. Due to induced scattering, short radio bursts with high brightness temperature can propagate only in relativistic plasmas [5].

Radio fluxes of FRBs agree with scaling suggested in [4]. A magnetar hyperflare at a distance of 600 Mpc would produce a FRB with the flux about 30 Jy [2]. FRBs detected by Thornton et al. are more distant, so their radio pluxes should to be lower, as observed. The rate of hyperflares for extragalactic SGRs was estimated in [2] to be 20-100 per day per cubic Gpc. This is confirmed by new FRB observations by Thornton et al. giving the rate about 10000 per day from the whole sky up to a distance of about 3 Gpc. Thus new observations by Thornton et al. support the model of FRB origin due to SGR giant flares [2].

Short radio burts from M31 have recently been reported [6]. Some of these events, especially multiple bursts with similar dispersion measure, can be related to repetitive activity of magnetars in M31. Here not giant flares, but with weaker SGR flares can be responsible for the observed radio bursts, assuming the SGR burst energy scaling from [2]. The rate of M31 radio bursts [6] is in agreement with that of flares with required luminosity assuming an SGR in M31 to be in active phase - a few events per hour. S.B Popov, K.A. Postnov

[1] D.R. Lorimer et al., Science 318, 777 (2007) [2] S.B. Popov, K.A. Postnov, arXiv: 0710.2006 [3] M. Lyutikov, Mon. Not. R. Astron. Soc. 367, 1594 (2006) [4] M. Lyutikov, Astrophys. J. 580, L65 (2002) [5] Y. Lyubarsky, Astrophys. J. 682, 1443 (2008) [6] E. Rubio-Herrera et al., Mon. Not. R. Astron. Soc. 428, 2857 (2013)

Submitted on Tue, 07/16/2013 - 05:02