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Professor Dai zigao from Nanjing University was invited to our school for academic exchange

Professor Dai zigao from Nanjing University was invited to our school for academic exchange

At the invitation of the school of physical science and technology, professor Dai zigao of Nanjing University came to our school for academic exchanges, and delivered an academic report titled "Binary Neutron Star Mergers" in the conference room 437 of Xingjian building at 3 PM on May 9, 2019. Teachers and postgraduates in related fields attended the academic report.

Dai zigao is a professor and doctoral supervisor at the school of astronomy and space science, Nanjing University. His research areas include neutron stars, pulsars, gamma-ray bursts, gamma-ray cosmology, rapid radio bursts, and superbright supernovae. He was awarded the national science foundation for outstanding young scientists in 1998 and was elected as a distinguished professor of the cheung kong scholars award scheme in 2002. He is the chief scientist of the GRB 973 project. He has won many national science and technology awards, such as the first prize of natural science of the ministry of education in 2002 and 2010, and the second prize of national natural science of the ministry of education in 2003.

In this report, the professor Dai Zigao introduced first 11 Nobel Prize awards of physics in the filed of high-energy astrophysics since 1936, and found that, for astrophysics especially in high-energy astrophysics areas to win the Nobel Prize, it needs to find new laws of extreme physical conditions or new probe of the universe! Professor Dai told us, in the four major basic interactions in physics at present, the strong interaction is one of the most unclear. Considering the equation of state for neutron stars, there are many mass - radius relation. Observation data maybe give limite. Professor Dai introduced short and long gamma-ray bursts and explained that long bursts may come from collapsing stars, while short bursts may come from merging neutron stars. Professor Dai introduced the fate of binary neutron star merger for different state equations, may lead to different merger products, a black hole or a neutron star.

Next, professor Dai described the gravitational wave event GW170817, which was the first observed GRB170817A, the electromagnetic counterpart of the gravitational wave event. This GRB was detected by Fermi/GBM about two seconds after the gravitational wave event. Dai also explained in detail the physical parameters of neutron stars that can be obtained from gravitational waves, and imposed restrictions on the equation of state. Then, the electromagnetic counterparts of binary neutron stars, such as gamma-ray bursts, kilonova and afterglow, are introduced. Kilonova is generally thought to be produced during the merger of binary neutron stars or black hole-neutron stars, in which faster neutron capture produces heavier elements such as lanthanides and actinides. Off-axis observations of GRB170817A exclude a uniform jet model, which may be a structured jet or a jet + cocoon model.

Report finally, professor Dai detailed introduced their proposed model in the event of the double neutron stars merge, they suggested that the merger of light may not be powered by radioactive elements, but powered by millisecond magnetar, and presented some relevant evidence. Chandrasekhar satellite observation is very good to prove it, not being a very high degree of confidence, but the problem still need further discussion. In addition, Dai also introduced the merger of black holes and neutron stars and discussed the possible applications in cosmology and basic physical examination.

After the end of the report, teachers and students responded very warmly, raised a lot of questions about the neutron star state equation, black hole neutron star merger and other related issues. Professor Dai carried out a detailed solution and discussion, and welcomed students to further contact and exchange.

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