Spectral properties of prompt emission of four short gamma-ray bursts observed by the Suzaku-WAM and the Konus-Wind

Masanori Ohno, Yasushi Fukazawa, Takuya Takahashi, Kazutaka Yamaoka, Satoshi Sugita, Valentin Pal'shin, Dmitry Frederiks, Philipp Oleynik, Mikhail Ulanov, Takanori Sakamoto, Goro Sato, Kevin Hurley, Makoto S. Tashiro, Yuji Urata, Kaori Onda, Toru Tamagawa, Yukikatsu Terada, Motoko Suzuki, Hong Soojing

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14 Citations (Scopus)

Abstract

We have performed a joint analysis of prompt emission from four bright short gamma-ray bursts (GRBs) with the Suzaku-WAM and the Konus-Wind experiments. This joint analysis allows us to investigate the spectral properties of short-duration bursts over a wider energy band with a higher accuracy. We find that these bursts have a high Epeak, around 1 MeV and have a harder power-law component than that of long GRBs. However, we can not determine whether these spectra follow the cut-off power-law model or the Band model. We also investigated the spectral lag, hardness ratio, inferred isotropic radiation energy and existence of a soft emission hump, in order to classify them into short or long GRBs using several criteria, in addition to the burst duration. We find that all criteria, except for the existence of the soft hump, support the fact that our four GRB samples are correctly classified as belonging to the short class. In addition, our broad-band analysis revealed that there is no evidence of GRBs with a very large hardness ratio, as seen in the BATSE short GRB sample, and that the spectral lag of our four short GRBs is consistent with zero, even in the MeV energy band, unlike long GRBs. Although our short GRB samples are still limited, these results suggest that the spectral hardness of short GRBs might not differ significantly from that of long GRBs, and also that the spectral lag at high energies could be a strong criterion for burst classification.

Original languageEnglish
JournalPublications of the Astronomical Society of Japan
Volume60
Issue numberSPEC. ISS. 1
Publication statusPublished - 2008

Keywords

  • Gamma rays: burst
  • Gamma rays: observations

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science

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    Ohno, M., Fukazawa, Y., Takahashi, T., Yamaoka, K., Sugita, S., Pal'shin, V., Frederiks, D., Oleynik, P., Ulanov, M., Sakamoto, T., Sato, G., Hurley, K., Tashiro, M. S., Urata, Y., Onda, K., Tamagawa, T., Terada, Y., Suzuki, M., & Soojing, H. (2008). Spectral properties of prompt emission of four short gamma-ray bursts observed by the Suzaku-WAM and the Konus-Wind. Publications of the Astronomical Society of Japan, 60(SPEC. ISS. 1).