2001 Fiscal Year Final Research Report Summary
milli second Magnetar and Gamma Ray Bursts
| Project/Area Number |
11640274
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| Research Category |
Grant-in-Aid for Scientific Research (C)
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| Allocation Type | Single-year Grants |
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| Section | 一般 |
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| Research Field |
素粒子・核・宇宙線
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| Research Institution | KYOTO UNIVERSITY |
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Principal Investigator |
NAKAMURA Takashi Yukawa Institute, KYOTO UNIVERSITY, Professor, 基礎物理学研究所, 教授 (80155837)
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| Project Period (FY) |
1999 – 2001
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| Keywords | Gamma Ray / Burst / Pulsar / Cosmology |
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| Research Abstract |
In 1999 I organized the workshop Gamma Ray Bursts in collaboration with YITP. In 2000 I also had the symposium on the future of the High Energy Astrophysics in collaboration with YITP as the post number of the participants were 60 and 130, respectively. Teoretical workshop on Gamma Ray Burst 2001 was organized by me and held from Aug. 23 to 25 of 2001. The workshop consists of 9 long talks and 10 short talks. The number of the registered participants was 50. In the past workshop on GRB (Gamma Ray Bursts), it was difficult to have three days program without the topics indirectly related to GRB. However in this time all the talks were directly related to GRB. Nine talks were given by PDFs and graduate students. This clearly shows that young people occupy the main part of the workshop. A new aspect of GRB appeared in the workshop. GRB should be a major probe to study the first stars, the formation of galaxy before the redshift 7. In this region the other probes such as QSO might be dim. I
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n this sense, even for the people who are not interested in the central engine of GRB, GRB should not be missed.
A formula for off-axis emissions from the beamed afterglow of GRBs in a syncrotron model is derived. The formula is applied to an inhomogeneous circumstellar matter obeying n proportional to 1/r^<**>2 suggested for SN1998bw/GRB980425. The slow decline rate as well as the X-ray flux similar to the observed values are obtained for appropriate choice of the parameters so that the association of GRB980425 with SN1998bw is further strengthened.
We assume that internal shocks of Gamma Ray Bursts (GRBs) consist of multiple sub-jets with a collimation half-angle 〜 several X <γ_i>^<-1>, where γ_i is the Lorenz factor of each sub-jet. If by chance a sub-jet is first emitted off-axis from the line of sight, the observed peak energy can be in the X-ray region. Next if by chance a subsequent sub-jet is emitted along the line of sight, then the peak energy will be in the gamma ray region and the gamma ray may arrive after the X-ray precursor from the former sub-jet depending on parameters. This model predicts a new class of GRBs with extremely weak and short gamma ray emission but X-ray precursor and/or post-cursor as well as an afterglow. Less
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