Article

Early afterglow detection in the Swift observations of GRB 050801

M. de PasqualeMullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking Surrey RH5 6NTS. R. OatesMullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking Surrey RH5 6NTM. J. PageMullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking Surrey RH5 6NTD. N. BurrowsDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAA. J. BlustinMullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking Surrey RH5 6NTSilvia ZaneMullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking Surrey RH5 6NTK. O. MasonMullard Space Science Laboratory, University College London, Holmbury St Mary, Dorking Surrey RH5 6NTP. W. A. RomingDepartment of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Laboratory, University Park, PA 16802, USAD. M. PalmerLos Alamos National Laboratories, Los Alamos, NM 87545, USAN. GehrelsGoddard Space Flight Center, NASA, Greenbelt, MD 20771, USABing ZhangDepartment of Physics, University of Nevada, Las Vegas, NV 89154, USA

2007en

ABI

Abstract

We present results of Swift optical, ultraviolet (UV) and X-ray observations of the afterglow of GRB 050801. The source is visible over the full optical, UV and X-ray energy range of the Swift Ultraviolet and Optical Telescope and X-ray telescope instruments. Both optical and X-ray light curves exhibit a broad plateau (Δt/t∼ 1) during the first few hundred seconds after the γ-ray event. We investigate the multiwavelength spectral and timing properties of the afterglow, and we suggest that the behaviour at early times is compatible with an energy injection by a newly born magnetar with a period of a few tenths of a millisecond, which keeps the forward shock refreshed over this short interval by irradiation. Reverse shock emission is not observed. Its suppression might be due to GRB ejecta being permeated by high magnetic fields, as expected for outflows powered by a magnetar. Finally, the multiwavelength study allows a determination of the burst redshift, z= 1.56.

Identifiers

DOI: 10.1111/j.1365-2966.2007.11724.x

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