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Outshining the quasars at reionisation: The X-ray spectrum and lightcurve of the redshift 6.29 Gamma-Ray Burst GRB050904 | | D. Watson
; J. N. Reeves
; J. Hjorth
; J. P. U. Fynbo
; P. Jakobsson
; K. Pedersen
; J. Sollerman
; J. M. Castro Cerón
; S. McBreen
; S. Foley
; | | Date: |
21 Sep 2005 | | Subject: | astro-ph | | Affiliation: | 2,3), J. Hjorth , J. P. U. Fynbo , P. Jakobsson , K. Pedersen , J. Sollerman , J. M. Castro Cerón , S. McBreen , S. Foley ( DARK Copenhagen, NASA-GSFC USRA ESA-ESTEC University College Dublin | | Abstract: | A gamma-ray burst (GRB) has finally been found with a redshift comparable to the most distant quasars and galaxies: GRB050904 at z=6.29+/-0.01, making it the most distant X-ray source known. The X-ray lightcurve for GRB 050904 is not a power-law like many GRB afterglows, but is dominated by large amplitude variability from a few minutes to at least half a day. The spectra soften during this time from a power-law with photon index Gamma=1.2 to 1.9. The spectra are well-described by an absorbed power-law with possible evidence of very large intrinsic absorption. There is no evidence for discrete features in spite of the spectrum’s very high signal-to-noise ratio, since GRB050904 was extraordinarily bright in X-rays. In the first days after the burst, it was by far the brightest known X-ray source at z>4. In the first minutes after the burst, the X-ray flux was >10^{-9} erg cm^-2 s^-1 in the 0.2--10 keV band, corresponding to an apparent luminosity between 10^5 and 10^6 times greater than the brightest X-ray quasars at similar distances. More photons were acquired in the first minutes with Swift-XRT than XMM-Newton and Chandra have obtained in ~300 ks of pointed observations of z>5 AGN. The huge X-ray fluence detected from GRB050904 is a clear demonstration of concept for efficient X-ray studies of the high-z IGM with new large area, high-resolution X-ray detectors, and shows that GRBs in their early phases are the only backlighting bright enough for X-ray absorption studies of the intervening matter at high redshift. | | Source: | arXiv, astro-ph/0509640 | | Services: | Forum | Review | PDF | Favorites | |
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