GRB 990413: Insight into the thermal phase evolution

Abstract

GRB 990413 shows a very hard spectrum (with a low energy spectral component F(E) \propto E^{2.49}) which is well represented by a black body model with characteristic temperature ~70 keV. It thus belongs to the subset of GRBs which might be revealing a thermal phase. We find that the temperature/luminosity evolution is consistent with that found in the other ``thermal'' GRBs. The time resolved spectral analysis indicates the presence of a second non--thermal component contributing (for about 1 s) up to 30 per cent of the total flux. Differently from the other thermal GRBs, GRB 990413 shows significantly high level of variability and the evolution of the thermal/non--thermal spectral components is strongly correlated with the flux variations. This GRB thus offers the unique opportunity to test the standard fireball photospheric and internal shock phases and their reciprocal influence. GRB 990413 was not selected on the basis of its spectrum and thus hints to the possibility that this early behavior might be more common than currently known.

6 pages, 5 figures, 2 tables. Accepted for publication in MNRAS Letter

References in corpus (19)

• Unsteady Outflow Models for Cosmological Gamma-Ray Bursts
• The BATSE Gamma-Ray Burst Spectral Catalog. I. High Time Resolution Spectroscopy of Bright Bursts using High Energy Resolution Data
• The Fourth BATSE Gamma-Ray Burst Catalog (Revised)
• Dissipative Photosphere Models of Gamma-ray Bursts and X-ray Flashes
• Steep Slopes and Preferred Breaks in GRB Spectra: the Role of Photospheres and Comptonization
• The observable effects of a photospheric component on GRB's and XRF's prompt emission spectrum
• A Possible Cepheid-Like Luminosity Estimator for the Long Gamma-Ray Bursts
• Low Frequency Spectra of Gamma-Ray Bursts
• BATSE Observations of Gamma-Ray Burst Spectra. II. Peak Energy Evolution in Bright, Long Bursts -
• The Cooling Behavior of Thermal Pulses in Gamma-Ray Bursts
• Evolution of the Low-Energy Photon Spectra in Gamma-Ray Bursts
• Constraints on the emission mechanisms of gamma-ray bursts
• The expected thermal precursors of gamma-ray bursts in the internal shock model
• Extremely hard GRB spectra prune down the forest of emission models
• Quasi-thermal Comptonization and gamma-ray bursts
• The Synchrotron Spectrum of Fast Cooling Electrons Revisited
• Compton Dragged Gamma--Ray Bursts associated with Supernovae
• Interpreting the Behavior of Time Resolved Gamma-Ray Burst Spectra
• Photospheric signatures imprinted on the gamma-ray burst spectra

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• Photosphere emission in the X-Ray Flares of Swift Gamma-Ray Bursts and Implications for the Fireball Properties
• Thermal Components in Gamma-ray Bursts. I. How Do They Affect Non-Thermal Spectral Parameters?
• The 999th Swift gamma-ray burst: Some like it thermal
• GRBs spectral correlations and their cosmological use