| 9th of May 2018 |
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| The polarization properties of two FRBs |
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Caleb et al., 2018 report on the polarization properties of two fast
radio bursts (FRBs): 151230 and 160102 discovered in the SUrvey for
Pulsars and Extragalactic Radio Bursts (SUPERB) at the Parkes radio
telescope. Fast radio bursts are millisecond duration, coherent bursts
with dispersion measures (DMs) well in excess of the Galactic
contribution thus indicating extragalactic/cosmological origins. FRB
151230 is observed to be 6(+/-11)% circularly polarized and
35(+/-13)% linearly polarized with a rotation measure (RM) consistent
with zero. Conversely, FRB 160102 is observed to have a circular
polarization fraction of 30(+/-11)%, linear polarization fraction
of 84(+/-15)% for RM = -221(6) rad m^-2 and the highest
measured DM (2596.1 +/- 0.3 pc cm^-3) for an FRB to date.
The figure above shows the comparison of the RMs and DMs of pulsars and FRBs. The DM values for the FRBs are upper limits as they are the total observed values. In the case of an FRB, the total observed DM is the sum of contributions from the Galactic foreground, the intergalactic medium, a potential host galaxy and possibly the immediate environment surrounding the progenitor. The Galactic magnetar J1745−2900, has an unusual line-of-sight which explains the high observed RM. The shaded regions enclose the RM and DM values expected from potential FRB models. More details are give in the the preprint of the paper, which will be published in Monthly Notices of the Royal Astronomical Society. |