A fast radio burst associated with a Galactic magnetar

Since their discovery in 2007, much effort has been devoted to uncovering the sources of the extragalactic, millisecond-duration fast radio bursts (FRBs). A class of neutron star known as magnetars is a leading candidate source of FRBs. Magnetars have surface magnetic fields in excess of $10^{14}$ G, the decay of which powers a range of high-energy phenomena. Here we present the discovery of a millisecond-duration radio burst from the Galactic magnetar SGR 1935+2154, with a fluence of $1.5\pm 0.3$ Mega-Jansky milliseconds. This event, termed ST 200428A(=FRB 200428), was detected on 28 April 2020 by the STARE2 radio array in the 1281--1468\,MHz band. The isotropic-equivalent energy released in ST 200428A is $4\times10^{3}$ times greater than in any Galactic radio burst previously observed on similar timescales. ST 200428A is just 40 times less energetic than the weakest extragalactic FRB observed to date, and is arguably drawn from the same population as the observed FRB sample. The coincidence of ST 200428A with an X-ray burst favours emission models developed for FRBs that describe synchrotron masers or electromagnetic pulses powered by magnetar bursts and giant flares. The discovery of ST 200428A implies that active magnetars like SGR 1935+2154 can produce FRBs at extragalactic distances. The high volumetric rate of events like ST 200428A motivates dedicated searches for similar bursts from nearby galaxies.Comment: 23 pages, 7 figures, 2 tables. Submitted to Natur

Multiwavelength Radio Observations of Two Repeating Fast Radio Burst Sources: FRB 121102 and FRB 180916.J0158+65

The spectra of fast radio bursts (FRBs) encode valuable information about the source's local environment, underlying emission mechanism(s), and the intervening media along the line of sight. We present results from a long-term multiwavelength radio monitoring campaign of two repeating FRB sources, FRB 121102 and FRB 180916.J0158+65, with the NASA Deep Space Network (DSN) 70 m radio telescopes (DSS-63 and DSS-14). The observations of FRB 121102 were performed simultaneously at 2.3 and 8.4 GHz, and spanned a total of 27.3 hr between 2019 September 19 and 2020 February 11. We detected two radio bursts in the 2.3 GHz frequency band from FRB 121102, but no evidence of radio emission was found at 8.4 GHz during any of our observations. We observed FRB 180916.J0158+65 simultaneously at 2.3 and 8.4 GHz, and also separately in the 1.5 GHz frequency band, for a total of 101.8 hr between 2019 September 19 and 2020 May 14. Our observations of FRB 180916.J0158+65 spanned multiple activity cycles during which the source was known to be active and covered a wide range of activity phases. Several of our observations occurred during times when bursts were detected from the source between 400 and 800 MHz with the Canadian Hydrogen Intensity Mapping Experiment (CHIME) radio telescope. However, no radio bursts were detected from FRB 180916.J0158+65 at any of the frequencies used during our observations with the DSN radio telescopes. We find that FRB 180916.J0158+65's apparent activity is strongly frequency-dependent due to the narrowband nature of its radio bursts, which have less spectral occupancy at high radio frequencies (≳ 2 GHz). We also find that fewer or fainter bursts are emitted from the source at high radio frequencies. We discuss the implications of these results for possible progenitor models of repeating FRBs

A Dual-band Radio Observation of FRB 121102 with the Deep Space Network and the Detection of Multiple Bursts

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. We 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. During the 5.7 hr continuous observing session, we detected 6 bursts from FRB 121102, which were visible in the 2.25 GHz frequency band. However, none of these bursts were detected in the 8.36 GHz band, despite the larger bandwidth and greater sensitivity in the higher-frequency band. 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.Comment: 8 pages, 3 figures, 1 table. Accepted for publication in ApJL on 2020 June 8. v2: Updated to match published versio

A Dual-band Radio Observation of FRB 121102 with the Deep Space Network and the Detection of Multiple Bursts

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 FRBs, 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. We present results from a simultaneous 2.25 and 8.36 GHz observation of the repeating FRB 121102 using the 70 m Deep Space Network radio telescope, DSS-43. During the 5.7 hr continuous observing session, we detected six bursts from FRB 121102, which were visible in the 2.25 GHz frequency band. However, none of these bursts were detected in the 8.36 GHz band, despite the larger bandwidth and greater sensitivity in the higher-frequency band. 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