TXS 0506+056

TXS 0506+056 is a very high energy blazar – a quasar with a relativistic jet pointing directly towards Earth – of BL Lac-type.

[20] TXS 0506+056 is one of the blazars regularly monitored by the OVRO 40 meter Telescope, so has an almost-continuous radio light curve recorded from 2008 onwards.

[7] A search of this region in the sky, 1.33 degrees across, yielded only one likely source: TXS 0506+056, a previously-known blazar, which was found to be in a flaring state of high gamma ray emission.

[22] An independent analysis found no gamma-ray flare during this earlier period of neutrino emission, but supported its association with the blazar.

[11] In the blazar, a charged pion was produced by the interaction of a high-energy proton or nucleus (i.e. a cosmic ray) with the radiation field or with matter.

[7] Upon reaching Earth, the neutrino interacted with the Antarctic ice to produce a muon, which was observed by the Cherenkov radiation it generated as it moved through the IceCube detector.

[26] In 2020, a study using MASTER global telescope network found that TXS 0506+056 was in an 'off' state in the optical spectrum 1 minute after the alert for IceCube-170922A event and switched back on 2 hours later.