Broadband lightcurve characteristics of GRBs 980425 and 060218 and comparison with long-lag, wide-pulse GRBs

Abstract

It has been recently argued that low-luminosity gamma-ray bursts (LL-GRBs) are likely a unique GRB population. Here, we present systematic analysis of the lightcurve characteristics from X-ray to gamma-ray energy bands for the 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 theses two bursts are energy-dependent over a broad energy band. There exists a significant trend that the pulses tend to be narrower and more symmetry with respect to the higher energy bands for the two events. Both the X-rays and the 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 be originated 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 derived $t_{peak}$ and $t_{cen}$ are a power-law function of energy. 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 $t_{peak}$ and CCF. The energy dependence of the lags is shallower at higher energy bands. These characteristics are well consistent with that observed in typical long-lag, wide-pulse GRBs, suggesting that GRBs 980425 and 060218 may share the similar radiation physics with them.

26 pages, 10 figures, 3 tables, accepted for publication in ApJ

References in corpus (18)

• An optical supernova associated with the X-ray flash XRF 060218
• A neutron-star-driven X-ray flash associated with supernova SN 2006aj
• On the Rates of Gamma Ray Bursts and Type Ib/c Supernovae
• SN 2006aj and the nature of low-luminosity gamma-ray bursts
• On the consistency of the peculiar GRBs 060218 and 060614 with the Ep,i - Eiso correlation
• Correlations Between Lag, Luminosity, and Duration in Gamma-ray Burst Pulses
• On the Spectral Lags of the Short Gamma-Ray Bursts
• Are GRB 980425 and GRB 031203 real outliers or twins of GRB 060218?
• Nonthermal gamma-ray and X-ray flashes from shock breakout in gamma-ray bursts/supernovae
• Temporal Profiles and Spectral Lags of XRF 060218
• Puzzled by GRB 060218
• The low-luminosity tail of the GRB distribution: the case of GRB 980425
• Revisiting the characteristics of the spectral lags in short gamma-ray bursts
• A test of the power law relationship between gamma-ray burst pulse width ratio and energy expected in fireballs or uniform jets
• Testing a new luminosity/redshift indicator for $\gamma$-ray bursts
• A Simple Two-Parameter Characterization of Gamma-Ray Burst Time Histories
• Relationship between pulse width and energy in GRB 060124: from X-ray to gamma-ray bands
• The complete catalogue of gamma-ray bursts observed by the Wide Field Cameras on board BeppoSAX

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