| 1. |
- Kirsten, Franz, 1983, et al.
(författare)
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A repeating fast radio burst source in a globular cluster
- 2022
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Ingår i: Nature. - : Springer Science and Business Media LLC. - 0028-0836 .- 1476-4687. ; 602:7898, s. 585-589
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Tidskriftsartikel (refereegranskat)abstract
- Fast radio bursts (FRBs) are flashes of unknown physical origin1. The majority of FRBs have been seen only once, although some are known to generate multiple flashes2,3. Many models invoke magnetically powered neutron stars (magnetars) as the source of the emission4,5. Recently, the discovery6 of another repeater (FRB 20200120E) was announced, in the direction of the nearby galaxy M81, with four potential counterparts at other wavelengths6. Here we report observations that localized the FRB to a globular cluster associated with M81, where it is 2 parsecs away from the optical centre of the cluster. Globular clusters host old stellar populations, challenging FRB models that invoke young magnetars formed in a core-collapse supernova. We propose instead that FRB 20200120E originates from a highly magnetized neutron star formed either through the accretion-induced collapse of a white dwarf, or the merger of compact stars in a binary system7. Compact binaries are efficiently formed inside globular clusters, so a model invoking them could also be responsible for the observed bursts.
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| 2. |
- Alef, Walter, et al.
(författare)
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BRAND - The next generation receiver for VLBI
- 2018
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Ingår i: Proceedings of Science. - Trieste, Italy : Sissa Medialab. - 1824-8039. ; 344
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Konferensbidrag (refereegranskat)abstract
- The aim of the BRAND EVN project is to build a very wide receiver prototype for primary focus with a frequency range from 1.5 GHz to 15.5 GHz In addition we will investigate solutions for secondary focus telescopes. The project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 730562 [RadioNet]. We present the status of the project which was started on January 1st, 2017 and is progressing smoothly: Feed, LNA, filters, major digital components, and some of the firmware are available now. © Copyright owned by the author(s) under the terms of the Creative Commons.
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| 3. |
- Hewitt, Dante M., et al.
(författare)
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Milliarcsecond localization of the hyperactive repeating FRB 20220912A
- 2024
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Ingår i: Monthly Notices of the Royal Astronomical Society. - 0035-8711 .- 1365-2966. ; 529:2, s. 1814-1826
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Tidskriftsartikel (refereegranskat)abstract
- We present very long-baseline interferometry (VLBI) observations of the hyperactive repeating FRB 20220912A using the European VLBI Network (EVN) outside of regular observing sessions (EVN-Lite). We detected 150 bursts from FRB 20220912A over two observing epochs in 2022 October. Combining the burst data allows us to localize FRB 20220912A to a precision of a few milliarcseconds, corresponding to a transverse scale of less than 10 pc at the distance of the source. This precise localization shows that FRB 20220912A lies closer to the centre of its host galaxy than previously found, although still significantly offset from the host galaxy's nucleus. On arcsecond scales, FRB 20220912A is coincident with a persistent continuum radio source known from archival observations; however, we find no compact persistent emission on milliarcsecond scales. The 5σ upper limit on the presence of such a compact persistent radio source is 120 μJy, corresponding to a luminosity limit of (D/362.4 Mpc)erg s-1 Hz-1. The persistent radio emission is thus likely to be from star formation in the host galaxy. This is in contrast to some other active FRBs, such as FRB 20121102A and FRB 20190520B.
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| 4. |
- Nimmo, K., et al.
(författare)
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A burst storm from the repeating FRB 20200120E in an M81 globular cluster
- 2023
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Ingår i: Monthly Notices of the Royal Astronomical Society. - : Oxford University Press (OUP). - 0035-8711 .- 1365-2966. ; 520:2, s. 2281-2305
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Tidskriftsartikel (refereegranskat)abstract
- The repeating fast radio burst (FRB) source FRB 20200120E is exceptional because of its proximity and association with a globular cluster. Here we report 60 bursts detected with the Effelsberg telescope at 1.4 GHz. We observe large variations in the burst rate, and report the first FRB 20200120E 'burst storm', where the source suddenly became active and 53 bursts (fluence ≥0.04 Jy ms) occurred within only 40 min. We find no strict periodicity in the burst arrival times, nor any evidence for periodicity in the source's activity between observations. The burst storm shows a steep energy distribution (power-law index α = 2.39 ± 0.12) and a bimodal wait-time distribution, with log-normal means of 0.94+0.07−0.06 s and 23.61+3.06−2.71 s. We attribute these wait-time distribution peaks to a characteristic event time-scale and pseudo-Poisson burst rate, respectively. The secondary wait-time peak at ∼1 s is ∼50 × longer than the ∼24 ms time-scale seen for both FRB 20121102A and FRB 20201124A - potentially indicating a larger emission region, or slower burst propagation. FRB 20200120E shows order-of-magnitude lower burst durations and luminosities compared with FRB 20121102A and FRB 20201124A. Lastly, in contrast to FRB 20121102A, which has observed dispersion measure (DM) variations of ΔDM > 1 pc cm−3 on month-to-year time-scales, we determine that FRB 20200120E's DM has remained stable (ΔDM < 0.15 pc cm−3) over >10 months. Overall, the observational characteristics of FRB 20200120E deviate quantitatively from other active repeaters, but it is unclear whether it is qualitatively a different type of source.
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| 5. |
- Nimmo, K., et al.
(författare)
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Burst timescales and luminosities as links between young pulsars and fast radio bursts
- 2022
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Ingår i: Nature Astronomy. - : Springer Science and Business Media LLC. - 2397-3366. ; 6:3, s. 393-401
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Tidskriftsartikel (refereegranskat)abstract
- Fast radio bursts (FRBs) are extragalactic radio flashes of unknown physical origin. Their high luminosities and short durations require extreme energy densities, such as those found in the vicinity of neutron stars and black holes. Studying the burst intensities and polarimetric properties on a wide range of timescales, from milliseconds down to nanoseconds, is key to understanding the emission mechanism. However, high-time-resolution studies of FRBs are limited by their unpredictable activity levels, available instrumentation and temporal broadening in the intervening ionized medium. Here we show that the repeating FRB 20200120E can produce isolated shots of emission as short as about 60 nanoseconds in duration, with brightness temperatures as high as 3 × 1041 K (excluding relativistic effects), comparable with ‘nano-shots’ from the Crab pulsar. Comparing both the range of timescales and luminosities, we find that FRB 20200120E observationally bridges the gap between known Galactic young pulsars and magnetars and the much more distant extragalactic FRBs. This suggests a common magnetically powered emission mechanism spanning many orders of magnitude in timescale and luminosity. In this Article, we probe a relatively unexplored region of the short-duration transient phase space; we highlight that there probably exists a population of ultrafast radio transients at nanosecond to microsecond timescales, which current FRB searches are insensitive to.
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