GRB 090618: different pulse temporal and spectral characteristics within a burst

Abstract

GRB 090618 was simultaneously detected by Swift-BAT and Fermi-GBM. Its light curve shows two emission episodes consisting of four prominent pulses. The pulse in the first episode (episode A) has a smoother morphology than the three pulses in the second episode (episode B). Using the pulse peak-fit method, we have performed a detailed analysis of the temporal and spectral characteristics of these four pulses and found out that the first pulse (pulse A) exhibits distinctly different properties than the others in episode B (pulses B1, B2 and B3) in the following aspects. (i) Both the pulse width ($w$) and the rise-to-decay ratio of pulse ($r/d$, pulse asymmetry) in GRB 090618 are found to be energy-dependent. The indices of the power-law correlation between $w$ and $E$ for the pulses in episode B however are larger than that in episode A. Moreover the pulses B1, B2 and B3 tend to be more symmetric at the higher energy bands while the pulse A displays a reverse trend. (ii) Pulse A shows a hard-to-soft spectral evolution pattern, while the three pulses in the episode B follow the light curve trend. (iii) Pulse A has a longer lag than the pulses B1, B2 and B3. The mechanism which causes the different pulse characteristics within one single GRB is unclear.

17 pages, 4 figures

References in corpus (9)

• Precursors in Swift Gamma Ray Bursts with redshift
• Temporal Profiles and Spectral Lags of XRF 060218
• The Spectral Lag of GRB060505: A Likely Member of the Long Duration Class
• Evidence for a proto-black hole and a double astrophysical component in GRB 101023
• Time-resolved spectral correlations of long-duration 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
• Broadband lightcurve characteristics of GRBs 980425 and 060218 and comparison with long-lag, wide-pulse GRBs
• Correlations between Lag, Duration, Peak Luminosity, Hardness, and Asymmetry in Long GRB Pulses
• Relationship between pulse width and energy in GRB 060124: from X-ray to gamma-ray bands

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