Multiple-component analysis of the time-resolved spectra of GRB 041006: A clue to the nature of the underlying soft component of GRBs

Yuji Shirasaki*, Atsumasa Yoshida, Nobuyuki Kawai, Toru Tamagawa, Takanori Sakamoto, Motoko Suzuki, Yujin Nakagawa, Akina Kobayashi, Satoshi Sugita, Ichiro Takahashi, Makoto Arimoto, Takashi Shimokawabe, Nicolas Vasquez Pazmino, Takuto Ishimura, Rie Sato, Masaru Matsuoka, Edward E. Fenimore, Mark Galassi, Donald Q. Lamb, Carlo GrazianiTimothy Q. Donaghy, Jean Luc Atteia, Alexandre Pelangeon, Roland Vanderspek, Geoffrey B. Crew, John P. Doty, Joel Villasenor, Gregory Paigozhin, Nat Butler, George R. Ricker, Kevin Hurley, Stanford E. Woosley, Graziella Pizzichini

*Corresponding author for this work

Research output: Contribution to journalArticlepeer-review

13 Citations (Scopus)


GRB 041006 was detected by HETE-2 on 2004 October 06. The light curves in four different energy bands display different features. At higher energy bands several peaks are seen in the light curve, while at lower energy bands a single broader bump dominates. It is expected that these different features are the result of a mixture of several components, each of which has different energetics and variability. We analyzed the time-resolved spectra, which were resolved into several components. These components can be classified into two distinct classes. One is a component that has an exponential decay of E p with a characteristic timescale shorter than ∼ 30s; its spectrum is well represented by a broken power-law function, which is frequently observed in many prompt GRB emissions, so it should have an internal-shock origin. Another is a component whose Ep is almost unchanged with a characteristic timescale longer than ∼ 60s, and shows a very soft emission and slower variability. The spectrum is characterized by either a broken power law or a black-body spectrum. By assuming that the soft component is a thermal emission, the radiation radius is initially 4.4 x 106km, which is a typical radius of a blue supergiant, and its expansion velocity is 2.4 x 10 5km s-1 in the source frame.

Original languageEnglish
Pages (from-to)919-931
Number of pages13
JournalPublications of the Astronomical Society of Japan
Issue number4
Publication statusPublished - 2008
Externally publishedYes


  • Gamma-rays: Bursts
  • X-rays: individual (GRB 041006)
  • X-rays: nursts

ASJC Scopus subject areas

  • Astronomy and Astrophysics
  • Space and Planetary Science


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