At 2017:9 on September 23, 5, the world's largest neutrino observation experiment IceCube at the South Pole detected a high-energy cosmic neutrino event. This neutrino event, named "Ice Cube-54A," was immediately distributed worldwide by the neutrino bulletin system developed mainly by Chiba University, and was followed up by various astronomical observation facilities.As a result, a blazer object TXS170922 + 0506, which has a huge black hole and emits very strong γ-rays, was confirmed in the direction of arrival of space neutrinos, and it became clear for the first time in history that γ-ray objects are the source of space neutrinos.

 IceCube is an international joint project by 12 research institutes in 49 countries around the world.Chiba University is the only official member from Japan.
In this research, aiming at the identification of the cosmic neutrino radiation source celestial body, which has been a mystery until now, it is called "multi-messenger observation" in which observation facilities around the world perform follow-up observations based on the information such as the arrival direction of the detected cosmic neutrinos. Pioneering new methods.An algorithm for identifying cosmic neutrino events in real time was developed mainly by Chiba University and started operation in April 2016.

 IceCube-170922A was detected under favorable conditions such as accurate estimation of the direction of arrival.The Kanata Telescope of Hiroshima University, which received the breaking news, started observation 20 hours after the detection of the neutrino event.We discovered that the blazer object TXS0506 + 056, which is in the direction of arrival of neutrinos, is brightening, and that it emits gamma rays with much higher brightness than usual.

 The probability of simultaneous observation of neutrinos and gamma-ray brightening by chance is about 0.003%, and it has been statistically verified that this object is a high-energy neutrino radiation source.This achievement can be said to be an important step in understanding the ultra-high energy cosmic ray radiation mechanism.

Paper information: [Science]Multimessenger observations of a flaring blazar coincident with high-energy neutrino IceCube-170922A
Neutrino emission from the direction of the blazar TXS 0506 + 056 prior to the IceCube-170922A alert

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