星系研究组知识库

It is recently suggested that low-luminosity gamma-ray bursts (LL-GRBs) are likely a unique GRB population. We present a systematical analysis of the light-curve characteristics from X-ray to gamma-ray bands for two prototypical LL-GRBs, 980425 and 060218. It is found that both the pulse width (w) and the ratio of the rising width to the decaying width (r/d) of the two bursts are energy-dependent over a broad energy band. There exists a significant trend that the pulses tend to be narrower and more symmetrical at higher energy bands for the two events. Both the X-rays and gamma-rays follow the same w-E and r/d-E relations. These facts may indicate that the X-ray emission tracks the gamma-ray emission, and both are likely to originate from the same physical mechanism. Their light curves show significant spectral lags. We calculate the three types of lags with the pulse peaking time (t(peak)), the pulse centroid time (t(cen)), and the cross-correlation function (CCF). The lag calculated by CCF is strongly correlated with that derived from t(peak), but the lag derived from t(cen) is less correlated with that derived from tpeak and CCF. We also find that their pulse temporal characteristics are normal when compared to the other normal BATSE GRB pulses, indicating that GRBs 980425 and 060218 may share a similar radiation physics with them.