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작성일 : 14-08-08 15:18
8월 13일(수요일) 우주과학과 세미나 안내
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안녕하세요. 우주과학과 우주탐사학과 여러분.
 
세미나 공지 드리겠습니다.
 
 
이번 세미나는 8월 13일 오후 4시 30분 천문대 영상실에서 있습니다.
 
Kavli Institute for Astronomy and Astrophysics, Peking University 의 Dr. Lucas Uhm 께서 " Radiation Mechanism of Gamma-ray Burst Prompt Emission and Afterglow " 라는 제목의 강연을 해 주실 예정입니다.
 
강연은 영어로 진행됩니다.
 
 
세미나 참석을 원하시는 분은 세미나 시작 10분 전까지 입실해 주시기 바랍니다.
 
많은 참석 부탁드립니다. 감사합니다.
 
 
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Dear Colleagues,
 
There will be an Astronomy and Space Science seminar August 13th, 4:30 PM,  in Auditorium, Kyung Hee Astronomical Observatory.
Dr. Lucas Uhm of Kavli Institute for Astronomy and Astrophysics, Peking University will give a presentation about " Radiation Mechanism of Gamma-ray Burst Prompt Emission and Afterglow ".
 
The language of the seminar will be English
 
 
You are asked to join the seminar five to ten minutes before it starts. Your attendance will greatly be appreciated.

 
 
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Seminar Information
 
When: August 13th (Wed), 4:30 PM
 
Where: Auditorium, Kyung Hee Astronomical Observatory.
 
Speaker: Dr. Lucas Uhm
 
Title : Radiation Mechanism of Gamma-ray Burst Prompt Emission and Afterglow
Abstract :
Even after more than 45 years of their discovery in late 1960s, the radiation mechanism of gamma-ray bursts (GRBs) remains unclear. Since the main component of GRB prompt emission in sub-MeV energy range exhibits a non-thermal nature with a smoothly-joined broken power-law spectral shape ("Band function"), the synchrotron radiation of relativistic electrons in the emitting region has been put forward as the leading mechanism that powers GRBs. However, it was soon realized that the standard synchrotron spectrum in the fast-cooling regime is not consistent with the observed low-energy spectral index of prompt emission spectra, and as a result, the synchrotron mechanism has been disfavored and other photospheric models were invoked for the prompt emission. Under these circumstances, a theoretical breakthrough in understanding the GRB radiation mechanism is recently made on the synchrotron side. It is shown that, when the magnetic field strength in the emitting region decreases in time, the fast-cooling synchrotron spectrum is in fact in a non-steady state and becomes significantly harder than the "standard" one, becoming well consistent with the observed low-energy index. This new physics of synchrotron cooling of relativistic electrons also applies to the GRB afterglow phase where the magnetic field strength in the shocked region naturally decreases as the blast wave propagates through the surrounding ambient medium. Recent theoretical developments made on the blast wave dynamics and afterglow modeling will also be presented for generic models with various density structures in the ejecta and ambient medium.