Deviation of light curves of gamma-ray burst pulses from standard forms due to the curvature effect of spherical fireballs or uniform jets

Abstract

As revealed previously, under the assumption that some pulses of gamma-ray bursts are produced by shocks in spherical fireballs or uniform jets of large opening angles, there exists a standard decay form of the profile of pulses arising from very narrow or suddenly dimming local (or intrinsic) pulses due to the relativistic curvature effect (the Doppler effect over the spherical shell surface). Profiles of pulses arising from other local pulses were previously found to possess a reverse S-feature deviation from the standard decay form. We show in this paper that, in addition to the standard decay form shown in Qin et al. (2004), there exists a marginal decay curve associated with a local $\delta$ function pulse with a mono-color radiation. We employ the sample of Kocevski et al. (2003) to check this prediction and find that the phenomenon of the reverse S-feature is common, when compared with both the standard decay form and the marginal decay curve. We accordingly propose to take the marginal decay curve (whose function is simple) as a criteria to check if an observed pulse could be taken as a candidate suffered from the curvature effect. We introduce two quantities $A_1$ and $A_2$ to describe the mentioned deviations within and beyond the $FWHM$ position of the decay phase, respectively. The values of $A_1$ and $A_2$ of pulses of the sample are calculated, and the result suggests that for most of these pulses their corresponding local pulses might contain a long decay time relative to the time scale of the curvature effect.

24 pages, 7 figures, 1 table accepted for publication in MNRAS

References in corpus (4)

• Search for Relativistic Curvature Effects in Gamma-Ray Burst Pulses
• Gamma-Ray Burst Spectra and Light Curves as Signatures of a Relativistically Expanding Plasma
• Characteristics of profiles of gamma-ray burst pulses associated with the Doppler effect of fireballs
• Emission and absorption lines of gamma-ray bursts affected by the relativistic motion of fireball ejecta

Cited by in corpus (14)

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• Testing the Curvature Effect and Internal Origin of Gamma-Ray Burst Prompt Emissions and X-ray Flares with Swift Data
• X-ray Hardness Evolution in GRB Afterglows and Flares: Late Time GRB Activity Without N_H Variations
• A test of the power law relationship between gamma-ray burst pulse width ratio and energy expected in fireballs or uniform jets
• The full curvature effect expected in early X-ray afterglow emission of gamma-ray bursts
• Spectral Lag Relations in GRB Pulses Detected with HETE-2
• The softening phenomenon due to the curvature effect: in the case of extremely short intrinsic emission
• Inferring the emission regions for different kinds of gamma-ray bursts
• Hardness ratio evolutionary curves of gamma-ray bursts expected by the curvature effect
• Dependence of Temporal Properties on Energy in Long-Lag, Wide-Pulse Gamma-Ray Bursts
• Roles of the kinetic and dynamic mechanisms in the $L_p-E_p$ relation
• Relationship between the rise width and the full width of gamma-ray burst pulses and its implications in terms of the fireball model
• Two types of softening detected in X-ray afterglows of Swift bursts: internal and external shock origins?
• Development of the spectrum of gamma-ray burst pulses influenced by the intrinsic spectral evolution and the curvature effect