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2nd of July 2020
Dual-Band Observations of FRB 121102 with the Tidbinbilla 70m
by Majid et al.
The spectra of repeating fast radio bursts (FRBs) are complex and time-variable, sometimes peaking within the observing band and showing a fractional emission bandwidth of about 10-30%. These spectral features may provide insight into the emission mechanism of repeating fast radio bursts, or they could possibly be explained by extrinsic propagation effects in the local environment. Broadband observations can better quantify this behavior and help to distinguish between intrinsic and extrinsic effects. Majid et al. present results from a simultaneous 2.25 and 8.36 GHz observation of the repeating FRB 121102 using the 70 m Deep Space Network (DSN) radio telescope, DSS-43, at the Canberra Deep Space Communication Complex (CDSCC). During a 5.7 hr observation, 6 bursts were detected from FRB 121102, all of which were visible in the 2.25 GHz frequency band but not detected in the 8.36 GHz band despite its larger bandwidth and greater sensitivity. This effect is not explainable by Galactic scintillation and, along with previous multi-band experiments, clearly demonstrates that apparent burst activity depends strongly on the radio frequency band that is being observed.

The figure above shows two of the 2-GHz band bursts detected from FRB 121102 with DSS-43. The flux calibrated, frequency-averaged burst profiles are shown in the top panels, and the dynamic spectrum associated with each burst is displayed in the bottom panels. The flux calibrated, time-averaged spectra are shown in the right panels. Each burst has been dedispersed using a DM of 563.6 pc/cm^3, determined from the brightest burst (B6). Each burst was fitted with a Gaussian function to determine the full-width at half-maximum (FWHM) burst duration, which is indicated with a cyan bar at the bottom of the top panels. The red ticks in the dynamic spectrum indicate frequency channels that have been masked as a result of radio-frequency interference (RFI). The paper will be published in Astrophysical Journal Letters.

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