The origin of the early time optical emission of Swift GRB 080310

Abstract

We present broadband multi-wavelength observations of GRB 080310 at redshift z = 2.43. This burst was bright and long-lived, and unusual in having extensive optical and near IR follow-up during the prompt phase. Using these data we attempt to simultaneously model the gamma-ray, X-ray, optical and IR emission using a series of prompt pulses and an afterglow component. Initial attempts to extrapolate the high energy model directly to lower energies for each pulse reveal that a spectral break is required between the optical regime and 0.3 keV to avoid over predicting the optical flux. We demonstrate that afterglow emission alone is insufficient to describe all morphology seen in the optical and IR data. Allowing the prompt component to dominate the early-time optical and IR and permitting each pulse to have an independent low energy spectral indices we produce an alternative scenario which better describes the optical light curve. This, however, does not describe the spectral shape of GRB 080310 at early times. The fit statistics for the prompt and afterglow dominated models are nearly identical making it difficult to favour either. However one enduring result is that both models require a low energy spectral index consistent with self absorption for at least some of the pulses identified in the high energy emission model.

24 pages, 12 figures, 12 tables. Accepted to MNRAS

References in corpus (7)

• Gamma-Ray Bursts: Progress, Problems & Prospects
• REM observations of GRB 060418 and GRB 060607A: the onset of the afterglow and the initial fireball Lorentz factor determination
• The Automated Palomar 60-Inch Telescope
• Ten per cent polarized optical emission from GRB 090102
• Global Properties of X-Ray Flashes and X-Ray-Rich Gamma-Ray Bursts Observed by Swift
• PROMPT Observations of the Early-Time Optical Afterglow of GRB 060607A
• Robust photometric redshift determinations of gamma-ray burst afterglows at z > 2

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• A Correlated Study of Optical and X-ray Afterglows of GRBs
• Cosmological Fast Optical Transients with the Zwicky Transient Facility: A Search for Dirty Fireballs
• GRB 090727 and gamma-ray bursts with early time optical emission
• A Large Catalogue of Multi-wavelength GRB Afterglows I: Color Evolution And Its Physical Implication
• Far-infrared observations of an unbiased sample of gamma-ray burst host galaxies
• Photospheric Prompt Emission From Long Gamma Ray Burst Simulations -- I. Optical Emission
• New radio constraints on the obscured star formation rates of massive GRB hosts at redshifts 2-3.5
• The CGM-GRB Study II: Outflow-Galaxy Connection at z ~ 2-6