E. Sonoda

Publications (4)0 Total impact

• Article: New probes of GRB prompt emission properties using wide‐band spectroscopy by Suzaku Wide‐band All‐sky Monitor

  M. Ohno, K. Ioka, M. Kokubun, M. Suzuki, T. Takahashi, T. Uehara, Y. Fukazawa, C. Kira, Y. Hanabata, K. Yamaoka, [......], K. Nakazawa, K. Makishima, E. Sonoda, M. Yamauchi, H. Tanaka, R. Hara, N. Ohmori, K. Kono, H. Hayasi, S. Hong
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  ABSTRACT: Although the afterglow observations in HETE‐2 and Swift era have revealed a lot of afterglow properties of gamma‐ray bursts (GRBs), we still have poor understanding of the prompt gamma‐ray emission, such as the emission mechanism of the prompt emission and differences between short and long duration GRBs. We have observed many prompt emission of GRBs by Suzaku Wide‐band All‐sky Monitor in wide energy range of 50–5000 keV, with very large effective area of 400 cm2 even at 1 MeV. Furthermore, a combination of the Suzaku∕WAM and Swift data provides us not only wider energy range of 15–5000 keV but also redshift information even for some short GRBs. Thanks to these information, we can firstly investigate an intrinsic correlation for short GRBs like Epeak−Liso relation, and we can derive the same type of relation for time‐resolved spectra of long GRBs in finer time‐scale with higher statistics than ever before. These results could be used to discuss the differences between short and long GRBs, and our time‐resolved Epeak−Liso relation also could be used as both more appropriate redshift indicator and new probe of the fireball dynamics.
  AIP Conference Proceedings. 05/2009; 1133(1):338-343.
• Article: The spectral properties of the GRB prompt gamma-ray emission observed by the Suzaku Wide-band All-sky Monitor

  M. Ohno, T. Uehara, T. Takahashi, Y. Fukazawa, C. Kira, Y. Hanabata, K. Yamaoka, Y. E. Nakagawa, S. Sugita, T. Tamagawa, [......], K. Makishima, E. Sonoda, M. Yamauchi, S. Maeno, H. Tanaka, R. Hara, M. Kokubun, S. Hong, T. Murakami, H. Tajima
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  ABSTRACT: We report on the observational results of GRBs by the Suzaku Wide-band All-sky Monitor (WAM) in these two years since the Suzaku launch. Using the WAM data, we can investigate the spectral properties of the prompt emission of GRBs with a wider energy band and the highest sensitivity than any previous GRB missions. We found that the spectral properties between short and long GRBs, such as the spectral parameter distribution, the hardness ratio, the spectral lag, and the total emitting energy are clearly different even in the MeV energy band. This result implies that different progenitors or different bulk Lorentz factors of the ejecta are likely causes for the difference between these two classes. We also found that there is a strong correlation between the peak energy and the isotropic equivalent luminosity of the time-resolved spectra of the bright long GRB 061007, and found that this correlation can be separated well between rising and decay phase of each pulse. This indicates that the physical condition changes during the pulse phase of the burst.
  04/2008; 1000:101-104.
• Source

  Available from: Makoto S. Tashiro

  Article: Status of GRB Observations with the Suzaku Wideband All-sky Monitor

  M. S. Tashiro, Y Terada, Y Urata, K Onda, N. Kodaka, A Endo, M Suzuki, K. Morigami, K Yamaoka, Y. E. Nakagawa, [......], E. Sonoda, M Yamauchi, S. Maeno, H Tanaka, R Hara, M Kokubun, S. J. Hong, T Murakami, H Tajima, the HXD team
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  ABSTRACT: The Wide-band All-sky Monitor (WAM) is a function of the large lateral BGO shield of the Hard X-ray Detector (HXD) onboard Suzaku. Its large geometrical area of 800 cm^2 per side, the large stopping power for the hard X-rays and the wide-field of view make the WAM an ideal detector for gamma-ray bursts (GRBs) observations in the energy range of 50-5000 keV. In fact, the WAM has observed 288 GRBs confirmed by other satellites, till the end of May 2007. Comment: 4 pages, 4 figures, to be published in the proceedings of ''Gamma Ray Bursts 2007'', Santa Fe, New Mexico, November 5-9
  02/2008;
• Source

  Available from: Makoto S. Tashiro

  Article: Swift and Suzaku Observations of the X-Ray Afterglow from the GRB 060105

  M. S. Tashiro, K Abe, L. Angelini, S. Barthelmy, N. Gehrels, N Ishikawa, L. J. Kaluzienski, N Kawai, R. L. Kelley, K Kinugasa, [......], T Takahashi, T Tamagawa, K. Torii, Y Ueda, Y Urata, K Yamaoka, M Yamauchi, D. Yonetoku, A Yoshida, S. Yoshinari
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  ABSTRACT: Results are presented of early X-ray afterglow observations of GRB 060105 by Swift and Suzaku. The bright, long gamma-ray burst GRB 060105 triggered the Swift Burst Alert Telescope (BAT) at 06:49:28 on 5 January 2006. The Suzaku team commenced a pre-planned target of opportunity observation at 19 ks (5.3 hr) after the Swift trigger. Following the prompt emission and successive very steep decay, a shallow decay was observed from T_0+187 s to T_0+1287 s. After an observation gap during T_0 +(1.5-3) ks, an extremely early steep decay was observed in T_0+(4-30) ks. The lightcurve flattened again at T_0+30 ks, and another steep decay followed from T_0+50 ks to the end of observations. Both steep decays exhibited decay indices of 2.3 - 2.4. This very early break, if it is a jet break, is the earliest case among X-ray afterglow observations, suggesting a very narrow jet whose opening angle is well below 1 degree. The unique Suzaku/XIS data allow us to set very tight upper limits on line emission or absorption in this GRB. For the reported pseudo-redshift of z=4.0+/-1.3 the upper limit on the iron line equivalent width is 50 eV.
  10/2006;