An optical spectrum of the afterglow of a γ-ray burst at a redshift of z = 6.295
2006; Nature Portfolio; Volume: 440; Issue: 7081 Linguagem: Inglês
10.1038/nature04498
ISSN1476-4687
AutoresN. Kawai, George Kosugi, Kentaro Aoki, Tōru Yamada, Tomonori Totani, Kouji Ohta, Masanori Iye, Takashi Hattori, Wako Aoki, Hisanori Furusawa, K. Hurley, Koji S. Kawabata, Naoto Kobayashi, Yutaka Komiyama, Y. Mizumoto, K. Nomoto, Junichi Noumaru, Ryusuke Ogasawara, Rie Sato, K. Sekiguchi, Y. Shirasaki, M. Suzuki, Tadafumi Takata, Toru Tamagawa, Hiroshi Terada, J. Watanabe, Yoichi Yatsu, A. Yoshida,
Tópico(s)Pulsars and Gravitational Waves Research
ResumoThe γ-ray burst GRB 050904, detected by the Swift satellite on 4 September last year, is one of the most distant objects ever observed. Its redshift of z = 6.3 equates to an explosion taking place 12.8 billion years ago, when the Universe was a mere 890 million years old. Three groups this week present detailed observations of the γ-ray, X-ray, near-infrared and optical spectra of the afterglow of GRB 050904. The results begin to paint a picture of the conditions prevailing when the parent body exploded and suggest that the γ-ray bursts that we see in the future can be used by cosmologists to probe the early Universe for evidence of star and galaxy formation, nucleosynthesis and reionization. The prompt γ-ray emission from γ-ray bursts (GRBs) should be detectable out to distances of z > 10 (ref. 1), and should therefore provide an excellent probe of the evolution of cosmic star formation, reionization of the intergalactic medium, and the metal enrichment history of the Universe1,2,3,4. Hitherto, the highest measured redshift for a GRB has been z = 4.50 (ref. 5). Here we report the optical spectrum of the afterglow of GRB 050904 obtained 3.4 days after the burst; the spectrum shows a clear continuum at the long-wavelength end of the spectrum with a sharp cut-off at around 9,000 Å due to Lyman α absorption at z ≈ 6.3 (with a damping wing). A system of absorption lines of heavy elements at z = 6.295 ± 0.002 was also detected, yielding the precise measurement of the redshift. The Si ii fine-structure lines suggest a dense, metal-enriched environment around the progenitor of the GRB.
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