Swift-UVOT captures the earliest ultraviolet spectrum of a Gamma Ray Burst

Abstract

We present the earliest ever ultraviolet spectrum of a gamma-ray burst (GRB) as observed with the Swift-UVOT. The GRB 081203A spectrum was observed for 50 seconds with the UV grism starting 251 seconds after the Swift-BAT trigger when the GRB was of u ~13.4 mag and still rising to its peak optical brightness. The UV grism spectrum shows a damped Ly-alpha line, Ly-beta, and the Lyman continuum break at a redshift z = 2.05 +/- 0.01. A model fit to the Lyman absorption implies log N(HI) = 22.0 +/- 0.2 cm-2, which is typical for GRB host galaxies with damped Ly-alpha absorbers. This observation of GRB 081203A demonstrates that for GRBs brighter than v ~14 mag and with 0.5 < z < 3.5 the UVOT will be able to provide redshifts, and probe for damped Ly-alpha absorbers within 4-6 minutes from the time of the Swift-BAT trigger.

4 pages, 4 figures, accepted by MNRAS letters

References in corpus (2)

• The First Swift Ultra-Violet/Optical Telescope GRB Afterglow Catalog
• A Survey for NV Absorption at z~z_GRB in GRB Afterglow Spectra: Clues to Gas Near the Progenitor Star

Cited by in corpus (14)

• SOUSA: the Swift Optical/Ultraviolet Supernova Archive
• The Konus-Wind catalog of gamma-ray bursts with known redshifts. I. Bursts detected in the triggered mode
• Phenomenology of Reverse-Shock Emission in the Optical Afterglows of Gamma Ray Bursts
• A Comparative Study of Long and Short GRBs. I. Overlapping Properties
• The Swift-UVOT ultraviolet and visible grism calibration
• A Correlated Study of Optical and X-ray Afterglows of GRBs
• Searching for differences in Swift's intermediate GRBs
• GRB 221009A: An ordinary nearby GRB with extraordinary observational properties
• A Large Catalog of Homogeneous Ultra-Violet/Optical GRB Afterglows: Temporal and Spectral Evolution
• Observational Search for PeV-EeV Tau Neutrino from GRB081203A
• Fires in the deep: The luminosity distribution of early-time gamma-ray-burst afterglows in light of the Gamow Explorer sensitivity requirements
• Swift/UVOT: 18 Years of Long GRB Discoveries and Advances
• A Method to Measure Photometries of Moderately-Saturated UVOT Sources
• Extract cleaned Swift/UVOT UV grism spectra with uvotpy package