GRB 081203A: Swift UVOT captures the earliest ultraviolet spectrum of a gamma-ray burst

GRB 081203A: Swift UVOT captures the earliest ultraviolet spectrum of a gamma-ray burst

We present the earliest ultraviolet (UV) spectrum of a gamma-ray burst (GRB) as observedwith the Swift Ultra-Violet/Optical Telescope (UVOT). The GRB 081203A spectrum wasobserved for 50 s with the UV-grism starting 251 s after the Swift-Burst-Alert-Telescope(BAT) trigger. During this time, the GRB w...

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Bibliographic Details
Main Authors: Kuin, N., Landsman, W., Page, M., Schady, P., Still, M., Breeveld, A., De Pasqualea, M., Roming, P., Brown, P., carter, M., James, C., Curran, Peter, Cucchiara, A., Gronwall, C., Holland, S., Hoversten, E., Hunsberger, S., Kennedy, T., Koch, S., Lamoureux, H., Marshall, F., Oates, S., Parsons, A., Palmer, D., Smith, P.
Format: Journal Article
Published: Wiley-Blackwell Publishing Ltd. 2009
Subjects:
instrumentation: spectrographs
gamma-rays: bursts
Online Access:http://mnrasl.oxfordjournals.org/content/395/1/L21.full.pdf+html
http://hdl.handle.net/20.500.11937/10158
Description
Summary:We present the earliest ultraviolet (UV) spectrum of a gamma-ray burst (GRB) as observedwith the Swift Ultra-Violet/Optical Telescope (UVOT). The GRB 081203A spectrum wasobserved for 50 s with the UV-grism starting 251 s after the Swift-Burst-Alert-Telescope(BAT) trigger. During this time, the GRB was ˜13.4 mag (u filter) and was still rising to itspeak optical brightness. In the UV-grism spectrum, we find a damped Lya line, Lyß and theLyman continuum break at a redshift z = 2.05 ± 0.01. A model fit to the Lyman absorptionimplies a gas column density of log NHI = 22.0 ± 0.1 cm-2, which is typical of GRB hostgalaxies with damped Lya absorbers. This observation of GRB 081203A demonstrates thatfor brighter GRBs (v ˜ 14 mag) with moderate redshift (0.5 < z < 3.5) the UVOT is able toprovide redshifts, and probe for damped Lya absorbers within 4–6 min from the time of theSwift-BAT trigger.

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