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Advances in Astronomy
Volume 2015, Article ID 341018, 12 pages
Research Article

Systematic Spectral Lag Analysis of Swift Known- GRBs

1Department of Physics and Mathematics, Aoyama Gakuin University, 5-10-1 Fuchinobe, Sagamihara, Kanagawa 252-5258, Japan
2Astrophysics Science Division, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA

Received 25 December 2014; Revised 12 March 2015; Accepted 3 April 2015

Academic Editor: Wing-Huen Ip

Copyright © 2015 Yuta Kawakubo et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.


The difference of photon arrival time, which is known as spectral lag, is well known characteristics of gamma-ray bursts (GRBs). In particular, long duration GRBs show a soft lag which means that high energy photons arrive earlier than soft photons. The lag-luminosity relation is the empirical relationship between the isotropic peak luminosity and the spectral lag. We calculated the spectral lags for 40 known redshift GRBs observed by Swift addition to the previous 31 GRB samples. We confirmed that most of our samples follow the lag-luminosity relation. However, we noticed that there are some GRBs which show a significant scatter from the relation. We also confirm that the relationship between the break time and the luminosity of the X-ray afterglow (so-called Dainotti relation) extends up to the lag-luminosity relation.