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When Bursters pulse and Pulsars burst — the Magnetar story

Presentation #119.02 in the session HEAD I: The Shaw Prize in Astronomy.

Published onJun 29, 2022
When Bursters pulse and Pulsars burst — the Magnetar story

On March 5th, 1979, the gamma-ray sky lit up from a tremendous explosion, similar to a Gamma Ray Burst (GRB). The transient, however, presented properties that did not agree with the nature of GRBs, which are catastrophic phenomena leaving behind them stellar size black holes. The March 5th event light curve showed clear evidence of pulsations and was followed by additional bursts from the same direction (albeit fainter, softer, and much shorter), indicative of a neutron star nature. In the next decade, two more sources were detected to produce ~100 – 200msec bursts, suggesting the discovery of a potential new class of objects, called soft gamma repeaters (SGRs). I was one of the proponents of this new kind of source, and strongly advocated their distinction from GRBs. To confirm their neutron star nature, I proposed to look for pulsations with the Rossi X-ray Timing Explorer in the next SGR source that would start actively bursting. SGR 1806-20 obliged with coherent pulsations of 7.47s and a fast spin down rate that translated to an extreme surface dipolar B-field of 8 × 1014 G. It was the first source officially entering the Thompson and Duncan magnetar club. Soon after many more were discovered and their properties were analyzed in detail by my team and by other colleagues, totaling ~30 sources. Today magnetars comprise a diverse group in our Galaxy, including sources that were initially classified as Anomalous X-Ray Pulsars, and Rotation Powered Pulsars. Recently, Fast Radio Bursts, a new phenomenon detected in distant galaxies by their very short and bright radio bursts, are also associated with magnetars, although their nature is still debated — the hunt is on.

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