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1. A fast radio burst associated with a Galactic magnetar

   https://doi.org/10.1038/s41586-020-2872-x  

   Bochenek, C. D.; Ravi, V.; Belov, K. V.; Hallinan, G.; Kocz, J.; Kulkarni, S. R.; McKenna, D. L. (November 2020, Nature)

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2. A fast radio burst localized to a massive galaxy

   https://doi.org/10.1038/s41586-019-1389-7  

   Ravi, V.; Catha, M.; Addario, L. D; Djorgovski, S. G.; Hallinan, G.; Hobbs, R.; Kocz, J.; Kulkarni, S. R.; Shi, J.; Vedantham, H. K.; et al (August 2019, Nature)

   Intense, millisecond-duration bursts of radio waves (named fast radio bursts) have been detected from beyond the Milky Way. Their dispersion measures—which are greater than would be expected if they had propagated only through the interstellar medium of the Milky Way—indicate extragalactic origins, and imply contributions from the intergalactic medium and perhaps from other galaxies. Although several theories exist regarding the sources of these fast radio bursts, their intensities, durations and temporal structures suggest coherent emission from highly magnetized plasma. Two of these bursts have been observed to repeat, and one repeater (FRB 121102) has been localized to the largest star-forming region of a dwarf galaxy at a cosmological redshift of 0.19. However, the host galaxies and distances of the hitherto non-repeating fast radio bursts are yet to be identified. Unlike repeating sources, these events must be observed with an interferometer that has sufficient spatial resolution for arcsecond localization at the time of discovery. Here we report the localization of a fast radio burst (FRB 190523) to a few-arcsecond region containing a single massive galaxy at a redshift of 0.66. This galaxy is different from the host of FRB 121102, as it is a thousand times more massive, with a specific star-formation rate (the star-formation rate divided by the mass) a hundred times smaller. 

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3. A Short Gamma-Ray Burst from a Protomagnetar Remnant

   https://doi.org/10.3847/1538-4357/ac972b  

   Jordana-Mitjans, N.; Mundell, C. G.; Guidorzi, C.; Smith, R. J.; Ramírez-Ruiz, E.; Metzger, B. D.; Kobayashi, S.; Gomboc, A.; Steele, I. A.; Shrestha, M.; et al (November 2022, The Astrophysical Journal)

   Abstract The contemporaneous detection of gravitational waves and gamma rays from GW170817/GRB 170817A, followed by kilonova emission a day after, confirmed compact binary neutron star mergers as progenitors of short-duration gamma-ray bursts (GRBs) and cosmic sources of heavy r -process nuclei. However, the nature (and life span) of the merger remnant and the energy reservoir powering these bright gamma-ray flashes remains debated, while the first minutes after the merger are unexplored at optical wavelengths. Here, we report the earliest discovery of bright thermal optical emission associated with short GRB 180618A with extended gamma-ray emission—with ultraviolet and optical multicolor observations starting as soon as 1.4 minutes post-burst. The spectrum is consistent with a fast-fading afterglow and emerging thermal optical emission 15 minutes post-burst, which fades abruptly and chromatically (flux density F ν ∝ t − α , α = 4.6 ± 0.3) just 35 minutes after the GRB. Our observations from gamma rays to optical wavelengths are consistent with a hot nebula expanding at relativistic speeds, powered by the plasma winds from a newborn, rapidly spinning and highly magnetized neutron star (i.e., a millisecond magnetar), whose rotational energy is released at a rate L th ∝ t −(2.22±0.14) to reheat the unbound merger-remnant material. These results suggest that such neutron stars can survive the collapse to a black hole on timescales much larger than a few hundred milliseconds after the merger and power the GRB itself through accretion. Bright thermal optical counterparts to binary merger gravitational wave sources may be common in future wide-field fast-cadence sky surveys. 

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4. Sub-second periodicity in a fast radio burst

   https://doi.org/10.1038/s41586-022-04841-8  

   Andersen, Bridget C.; Bandura, Kevin; Bhardwaj, Mohit; Boyle, P. J.; Brar, Charanjot; Breitman, Daniela; Cassanelli, Tomas; Chatterjee, Shami; Chawla, Pragya; Cliche, Jean-François; et al (July 2022, Nature)
5. A Nonrepeating Fast Radio Burst in a Dwarf Host Galaxy

   https://doi.org/10.3847/1538-4357/acc178  

   Bhandari, Shivani; Gordon, Alexa C.; Scott, Danica R.; Marnoch, Lachlan; Sridhar, Navin; Kumar, Pravir; James, Clancy W.; Qiu, Hao; Bannister, Keith W.; T. Deller, Adam; et al (May 2023, The Astrophysical Journal)

   Abstract We present the discovery of an as yet nonrepeating fast radio burst (FRB), FRB 20210117A, with the Australian Square Kilometre Array Pathfinder (ASKAP), as a part of the Commensal Real-time ASKAP Fast Transients Survey. The subarcsecond localization of the burst led to the identification of its host galaxy atz= 0.214(1). This redshift is much lower than what would be expected for a source dispersion measure (DM) of 729 pc cm⁻³, given typical contributions from the intergalactic medium and the host galaxy. Optical observations reveal the host to be a dwarf galaxy with little ongoing star formation—very different to the dwarf host galaxies of the known repeating FRBs 20121102A and 20190520B. We find an excess DM contribution from the host and attribute it to the FRB’s local environment. We do not find any radio emission from the FRB site or host galaxy. The low magnetized environment and the lack of a persistent radio source indicate that the FRB source is older than those found in other dwarf host galaxies, establishing the diversity of FRB sources in dwarf galaxy environments. We find our observations to be fully consistent with the “hypernebula” model, where the FRB is powered by an accretion jet from a hyperaccreting black hole. Finally, our high time resolution analysis reveals burst characteristics similar to those seen in repeating FRBs. We encourage follow-up observations of FRB 20210117A to establish any repeating nature. 

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