主要内容:
通过模拟光变曲线,把低红移的移到高红移去(会包括流量的减少和能段的移动),看和实际观测到的高红移的暴的表现是否一致,用KS检验,发现不一样。
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文章信息:
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Title: |
| Are gamma-ray bursts the same at high redshift and low redshift? |
Authors: |
| Littlejohns, O. M.; Tanvir, N. R.; Willingale, R.; Evans, P. A.; O'Brien, P. T.; Levan, A. J. |
Affiliation: |
| AA(Department
of Physics and Astronomy, University of Leicester, Leicester LE1 7RH,
UK; School of Earth and Space Exploration, Arizona State University,
Tempe, AZ 85287, USA; olittlej@asu.edu), AB(Department of
Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK),
AC(Department of Physics and Astronomy, University of Leicester,
Leicester LE1 7RH, UK), AD(Department of Physics and Astronomy,
University of Leicester, Leicester LE1 7RH, UK), AE(Department of
Physics and Astronomy, University of Leicester, Leicester LE1 7RH, UK),
AF(Department of Physics, University of Warwick, Coventry CV4 7AL, UK) |
Publication: |
| Monthly Notices of the Royal Astronomical Society, Volume 436, Issue 4, p.3640-3655 (MNRAS Homepage) |
Publication Date: |
| 12/2013 |
Origin: |
| OUP |
Astronomy Keywords: |
| gamma-ray burst: general |
Abstract Copyright: |
| 2013 The Authors Published by Oxford University Press on behalf of the Royal Astronomical Society |
DOI: |
| 10.1093/mnras/stt1841 |
Bibliographic Code: |
| 2013MNRAS.436.3640L |
Abstract
The majority of Swift gamma-ray bursts (GRBs) observed at z ≳ 6
have
prompt durations of T
90 ≲ 30 s, which, at first
sight, is surprising given that cosmological time dilation means this
corresponds to ≲5 s in their rest frames. We have tested whether
the high-redshift GRBs are consistent with being drawn from the same
population as those observed at low
redshift by comparing them to an
artificially redshifted sample of 114 z < 4 bursts. This is
accomplished using two methods to produce realistic high-z simulations
of light curves based on the observed characteristics of the low-z
sample. In Method 1 we use the Swift/Burst Alert Telescope (BAT) data
directly, taking the photons detected in the harder bands to predict
what would be seen in
the softest energy band if the burst were seen at
higher z. In Method 2 we fit the light curves with a model, and use that
to extrapolate the expected
behaviour over the whole BAT energy range at
any
redshift. Based on the results of Method 2, a Kolmogorov-Smirnov
test of their durations finds a ˜1 per cent probability that the
high-z GRB sample is drawn from the same population as the bright low-z
sample. Although apparently marginally significant, we must bear in mind
that this test was partially a posteriori, since the rest-frame short
durations of several high-z bursts motivated the study in the first
instance.
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