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Crawford et al. present four new fast radio bursts discovered in a
search of the Parkes 70-cm pulsar survey data archive for dispersed
single pulses and bursts.
A total of 719905 single pulse candidates were detected in the survey,
of which 75774 were classified as possibly real.
All but 7 of the classified signals were either rejected by eye as
not morphologically realistic or were determined to have come from
known pulsars, some of which emitted many detectable pulses in a
single observation (e.g., the Vela pulsar and PSR J0437−4715)
Of the 7 unidentified signals, three were weak pulses with
narrow widths and small Dispersion Measures, indicating likely
Rapidly Rotating Transients (RRATs) in our Galaxy.
The four FRBs
discovered have significantly larger widths (> 50 ms) than almost all
of the FRBs detected and cataloged to date, however, the large pulse widths are
not dominated by interstellar scattering or dispersive smearing within
channels.
The image above shows the detection plot of FRB910730, which is
the earliest FRB to have been detected
by any radio telescope to date, predating the Lorimer Burst
-- the first Fast Radio Burst to be discovered -- by almost a decade.
Frequency channels corrupted by RFI (radio frequency interference)
have been masked in the middle plot. Each panel shows the dedispersed pulse profile for the burst
(top), signal strength (brightness) vs. frequency and time for the dedispersed
pulse (middle), and signal strength (brightness) vs. DM and time (bottom).
The burst widths are significantly larger than the widths measured for
almost all of the FRBs detected and cataloged to date. This may
indicate that many more such signals could be present in pulsar
surveys which could have been missed in searches that did not increase
the search window to sufficiently large values.
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