Hunderte von FRBs

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Fast Radio Burst (FRB)

Nachdem zunächst nur von einzelnen und schwer zu lokalisierenden Ereignissen die Rede war, siehe z.B. FRBs und Perytons, sprechen wir jetzt schon von Hunderten solcher Fälle. Insbesondere das Canadian Hydrogen Intensity Mapping Experiment (CHIME) hat den Zähler bereits im ersten Betriebsjahr um 500 FRBs erhöht:

Number of mysterious radio flashes quadruples

At the recent virtual meeting of the American Astronomical Society, a first data release from the Canadian Hydrogen Intensity Mapping Experiment (CHIME) nearly quadruples that number with 535 new fast radio bursts (FRBs), including 61 bursts from 18 repeating sources. The data come from the detector’s first year of operations, from mid-2018 to mid-2019.

CHIME is uniquely suited to finding FRBs because, unlike most radio telescopes with postage-stamp fields of view, it scans the whole sky visible from its location in British Columbia every night. Astronomers then use digital signal-processing to work through huge amounts of data - about 7 terabits per second, equivalent to a few percent of the world’s internet traffic - to “focus” on FRB signals.


Ein wesentlicher Fortschritt im Verständnis von FRBs gelang dabei mit dem Nachweis von FRB 200428

Ein innergalaktischer FRB und Magnetar


On 28 April 2020, CHIME astronomers reported the detection of a bright radio burst from the direction of the Galactic magnetar SGR 1935+2154 about 30,000 light years away in the Vulpecula constellation.
 
Der FRB 190520 wirft Fragen auf:

"The dispersive sweep of fast radio bursts (FRBs) has been used to probe the ionized baryon content of the intergalactic medium1, which is assumed to dominate the total extragalactic dispersion. Although the host-galaxy contributions to the dispersion measure appear to be small for most FRBs2, in at least one case there is evidence for an extreme magneto-ionic local environment3,4 and a compact persistent radio source5. Here we report the detection and localization of the repeating FRB 20190520B, which is co-located with a compact, persistent radio source and associated with a dwarf host galaxy of high specific-star-formation rate at a redshift of 0.241 ± 0.001. The estimated host-galaxy dispersion measure of approximately 903+72−111 parsecs per cubic centimetre, which is nearly an order of magnitude higher than the average of FRB host galaxies2,6, far exceeds the dispersion-measure contribution of the intergalactic medium. Caution is thus warranted in inferring redshifts for FRBs without accurate host-galaxy identifications."

Quelle: https://www.nature.com/articles/s41586-022-04755

Anscheinend wirft die Berechnung der Entfernung dieser Quelle nach der "Dispersionsmethode" eine wesentlich größere Entfernung aus, als die Rotverschiebung für die Gastgalaxie hergibt.

Thomas
 
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