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Polarized Emission from Gamma-Ray Burst Jets

Shiho Kobayashi
2017 Galaxies  
I review how polarization signals have been discussed in the research field of Gamma-Ray Bursts (GRBs). I mainly discuss two subjects in which polarimetry enables us to study the nature of relativistic jets. (1) Jet breaks: Gamma-ray bursts are produced in ultra-relativistic jets. Due to the relativistic beaming effect, the emission can be modeled in a spherical model at early times. However, as the jet gradually slows down, we begin to see the edge of the jet together with polarized signals at
more » ... some point. (2) Optical flash: later time afterglow is known to be insensitive to the properties of the original ejecta from the GRB central engine. However, a short-lived, reverse shock emission would enable us to study the nature of of GRB jets. I also briefly discuss the recent detection of optical circular polarization in GRB afterglow.
doi:10.3390/galaxies5040080 fatcat:7jpjcngnxrhsnbflq2yv4rbjpu

Gravitational Radiation from Gamma-Ray Burst Progenitors

Shiho Kobayashi
2004 AIP Conference Proceedings  
A key feature of internal shocks is that the observed gamma-ray variability reflects the variability in the activity of the central engine (Kobayashi, Piran & Sari 1997) .  ... 
doi:10.1063/1.1810817 fatcat:5dzqz5njlrgctmunyka6syaaai

Luminosity and Variability of Collimated Gamma-Ray Bursts

Shiho Kobayashi
2003 AIP Conference Proceedings  
The wind can be modeled by a succession of relativistic shells (Kobayashi, Piran & Sari 1997, hereafter KPS) .  ...  A simplified description of this process is to assume that the two shells reflect with a smaller relative velocity (Kobayashi & Sari 2001).  ... 
doi:10.1063/1.1579352 fatcat:4r555435xffbhfkruboqgxgvyi

Ultraefficient Internal Shocks

Shiho Kobayashi, Re'em Sari
2001 Astrophysical Journal  
Ðreball (Sari & Piran 1995 ; Kobayashi, Piran, & Sari 1999) .  ...  We have developed a relativistic code with an exact Riemann solver to solve relativistic hydrodynamics problems (Kobayashi et al. 1999) .  ... 
doi:10.1086/320249 fatcat:hl3ceynumvdxxjxjxsiyaeioqm

Best differential characteristic search of FEAL [chapter]

Kazumaro Aoki, Kunio Kobayashi, Shiho Moriai
1997 Lecture Notes in Computer Science  
This paper presents the results of the best differential characteristic search of FEAL. The search algorithm for the best differential characteristic (best linear expression) was already presented by Matsui, and improvements on this algorithm were presented by Moriai et al. We further improve the speed of the search algorithm. For example, the search time for the 7round best differential characteristic of FEAL is reduced to about 10 minutes (Pentium/166 MHz), which is about 212"6 times faster
more » ... an Matsui's algorithm. Moreover, we determine all the best differential characteristics of FEAL for up to 32 rounds assuming all S-boxes are independent. As a result, we confirm that the N-round (7 < N <32) best differential characteristic probability of FEAL is 2 -2N, which was found by Biham. For N = 6, we find 6-round differential characteristics with a greater probability, 2 -11 , than that previously discovered, 2 -12.
doi:10.1007/bfb0052333 fatcat:ykbf4ziur5belfteu3jbyqobku

Optical flashes and radio flares in GRB afterglows: Numerical study

Shiho Kobayashi
2000 AIP Conference Proceedings  
We numerically study the evolution of an adiabatic relativistic fireball interacting with an ambient uniform medium, both in the initial energy transfer stage and in its late evolution. It is shown that the Blandford-McKee solution adequately describes the evolution of the shocked ejecta quite early on and for as long as the fireball material has relativistic temperatures. In the case where the reverse shock is only mildly relativistic, the shocked ejecta becomes cold almost immediately and the
more » ... evolution deviates from the Blandford-McKee solution. We derive analytical expressions for the ejecta evolution in its cold regime. This solution gives a good approximation to the numerical results. We estimate the radiation from the fireball ejecta using the numerical hydrodynamic evolution in both cases: cold and hot ejecta. Surprisingly, we find that both evolutions give rather similar light curves, decaying approximately as t-" in the optical and peaking after about one day in the radio, even though the hydrodynamics is different.
doi:10.1063/1.1361598 fatcat:wtr2eduicrd4vbmjqfpvev2a3y

Revealing Short GRB Jet Structure and Dynamics with Gravitational Wave Electromagnetic Counterparts [article]

Gavin P. Lamb, Shiho Kobayashi
2017 arXiv   pre-print
Figure adapted from Lamb & Kobayashi 2017c  ...  The afterglow is bright for an on-axis observer (Lamb & Kobayashi 2017d) .  ... 
arXiv:1712.02986v1 fatcat:5tay6hclbzdptdt5xh2nnwna4m

Background Gravitational Wave Produced in Inflationary Universe

Shin-ichi Nakamura, Noriaki Yoshino, Shiho Kobayashi
1992 Progress of theoretical physics  
We quantize the gravitational wave which arises from quantum fluctuations in the inflationary universe and compute its time evolution using a simple model of the cosmological evolution. As a result, we obtain the power spectrum of the background gravitational wave and calculate the behavior of the squeezed parameters.
doi:10.1143/ptp.88.1107 fatcat:6wxhduteq5gmhd3i63dji5oijq

Light Curves of Gamma‐Ray Burst Optical Flashes

Shiho Kobayashi
2000 Astrophysical Journal  
The fireball of GRB 990123 is likely to be a marginal case (Kobayashi & Sari 2000) .  ...  A prompt optical emission from GRB 990123 (Akerlof et al. 1999) can be regarded as this emission (Sari & Piran 1999b; Kobayashi & Sari 2000) .  ... 
doi:10.1086/317869 fatcat:zywftljjfbgeph6vsii2xacspq

Can internal shocks produce the variability in GRBs?

Shiho Kobayashi, Tsvi Piran, Re'em Sari
1998 Fourth Huntsville gamma-ray burst symposium  
We discuss the possibility that gamma-ray bursts result from internal shocks in an ultra-relativistic matter. Using a simple model we calculate the temporal structure and we estimate the efficiency of this process. In this model the ultra-relativistic matter flow is represented by a succession of shells with random values of the Lorentz factor. We calculate the shocks that take place between those shells and we estimate the resulting emission. Internal shocks can produce the highly variable
more » ... oral structure observed in most of the bursts provided that the source emitting the relativistic flow is highly variable. The observed peaks are in almost one to one correlation to the activity of the emitting source. A large fraction of the kinetic energy is converted to radiation. The most efficient case is when an inner engine produces shells with comparable energy but very different Lorentz factors. It also gives the most preferable temporal structure.
doi:10.1063/1.55397 fatcat:gljzoqwqirczbh35rhqtcgpbti

Beach Changes Observed in Phan Rang City in Southeast Vietnam

Yasuhito Noshi, Takaaki Uda, Akio Kobayashi, Shiho Miyahara, Masumi Serizawa
2015 Procedia Engineering  
In cooperation with Ho Chi Minh City University of Vietnam, beach changes on the coasts of Phan Rang City 270 km east of Ho Chi Minh City were investigated. Beach changes associated with the elongation of a sand spit and sand accumulation owing to the blockage of longshore sand transport by a jetty were investigated using satellite images together with site observation. This method combined satellite image analysis and site observation is useful for investigating beach changes in developing
more » ... tries, where field data necessary for the analysis are often lacking. Preventive or mitigation measures were considered in view of Integrated Coastal Zone Management in place of the local optimization.
doi:10.1016/j.proeng.2015.08.278 fatcat:b3nfz3uabrhxpi6jkw7mp77xz4

GRB 021004: Reverse Shock Emission

Shiho Kobayashi, Bing Zhang
2003 Astrophysical Journal  
The shock crossing time is (Sari & Piran 1999b; Kobayashi 2000) .  ...  The lower 12 11 10 ( p p 2.4) 8.8 # 10 ( p p 2.2) also makes the reverse shock emission dimmer in the n (t ) m, r # R band (Kobayashi 2000) .  ... 
doi:10.1086/367691 fatcat:vfjajboqkfgkpnq5reqv7nbwei

Polyphenol Contents and Processing Properties of Screenings of Black-kerneled Glutinous Rice Cultivar ^|^lsquo;Shiho^|^rsquo;

Kazuyuki Kobayashi, Toshio Joh, Toshinori Fukuyama
2013 Nippon sakumotsu gakkai kiji  
Polyphenol Contents and Processing Properties of Screenings of Black-kerneled Glutinous Rice Cultivar 'Shiho' : Kazuyuki Kobayashi 1) , Toshio Joh 2) and Toshinori Fukuyama 2) ( 1) Niigata Agr. Res.  ...  Kobayashi, Y. Nishiba, S. Furuta, I. Suda and T. Sato 2002. Polymeric procyanidins as radical-scavenging components in red-hulled rice. J. Agric.  ... 
doi:10.1626/jcs.82.192 fatcat:ftkhospaina5jc5274ehhlkkga

Ⅱ-2. Influence of groundwater on primary production
Ⅱ-2. 低次生産と地下水・海底湧水

2016 Nippon Suisan Gakkaishi  
doi:10.2331/suisan.wa2308-7 fatcat:pzhaphdmjrhkrc3jm4ygao47we

Anderson Localization in the Sky and Cosmological Magnetic Field

1996 Soryushiron Kenkyu Electronics  
Anderson Localization in the Sky and Cosmological Magnetic Field i Shiho KOBAYASHP Dept. of Physics, Tokyo Institute of Technology It has long been suspected that the presently observed galactic and cluster  ... 
doi:10.24532/soken.93.3_c117 fatcat:zegeqconxba6jmnkzb6g75k5m4
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