Daily Image
07-11-2022
Happy 10th birthday to "The Repeater", FRB 121102
| Submitter: | Jason Hessels |
| Description: | They grow up so fast... the famous FRB 121102 has just turned 10 years old (plus of course the 3 billion years it took the signal to reach Earth from its host galaxy). This picture shows a 3D printed burst from FRB 121102, wearing a special birthday hat. Fast radio bursts (FRBs) have been an astrophysical mystery since the discovery of the Lorimer Burst in 2007. What is producing these remarkably luminous and ephemeral radio bursts originating from distant galaxies? The hyper-magnetised neutron stars known as "magnetars" are a leading contender, but it's unclear whether all FRBs have a magnetar origin or whether there are multiple physical progenitors creating the observed sample. The discovery of FRB 121102 has had a huge impact on our understanding of the phenomenon. Discovered by Laura Spitler, FRB 121102 was the first such source to be found using the Arecibo 305-m telescope. Previously, all known FRBs had been found using the Parkes (Murriyang) 64-m dish, leaving still some scepticism about whether these flashes are genuine astrophysical signals or pernicious human-made interference. The discovery of an FRB with a 2nd telescope brought strong confidence that these signals are indeed astrophysical, which is now well established. Even more striking was the 2016 discovery that FRB 121102 repeats. It is not so often in science that a single observable can rule out so many theories in one blow, but for FRB 121102 it was clear that whatever is producing the bursts must be relatively long-lived - as opposed to a one-time-only cataclysmic explosion. Since then we have localised FRB 121102 to its dwarf host galaxy using the VLA and EVN. The FRB source is close to a knot of star-formation, as imaged with the Hubble Space Telescope, and also coincident with a compact, persistent radio source. Subsequent observations revealed an enormous Faraday rotation measure - showing that FRB 121102 is embedded in an extreme magneto-ionic environment, and suggesting that the persistent radio source may be some form of nebula powered by the burst source. Detailed studies of the bursts themselves show a striking effect, now colloquially termed the `sad trombone' effect, in which the bursts drift to lower radio frequencies at later times. This may be showing us how the emitting region is propagating outwards from the central engine. Thanks to the CHIME/FRB system, and other telescopes, we now know of over two dozen repeating FRBs, and another 600 FRB sources that have so far failed to repeat. FRB 121102 remains a prototype for the class, though at the same time we are scratching our heads about the diversity in burst properties and host galaxies we see between different sources. There are still many questions to solve, and its a very exciting time to be working in high-time-resolution radio astronomy! |
| Copyright: | Hessels |
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