University of Leicester
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Swift observations of GRB 070110: An extraordinary X-ray afterglow powered by the central engine

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posted on 2012-10-24, 09:06 authored by E Troja, G Cusumano, PT O'Brien, B Zhang, B Sbarufatti, V Mangano, R Willingale, G Chincarini, JP Osborne, FE Marshall, DN Burrows, S Campana, N Gehrels, C Guidorzi, HA Krimm, La Parola V, EW Liang, T Mineo, A Moretti, KL Page, P Romano, G Tagliaferri, BB Zhang, MJ Page, P Schady
We present a detailed analysis of Swift multiwavelength observations of GRB 070110 and its remarkable afterglow. The early X-ray light curve, interpreted as the tail of the prompt emission, displays a spectral evolution already seen in other gamma-ray bursts. The optical afterglow shows a shallow decay up to ~2 days after the burst, which is not consistent with standard afterglow models. The most intriguing feature is a very steep decay in the X-ray flux at ~2 × 10^4 s after the burst, ending an apparent plateau. The abrupt drop of the X-ray light curve rules out an external shock as the origin of the plateau in this burst and implies long-lasting activity of the central engine. The temporal and spectral properties of the plateau phase point toward a continuous central engine emission rather than the episodic emission of X-ray flares. We suggest that the observed X-ray plateau is powered by a spinning-down central engine, possibly a millisecond pulsar, which dissipates energy at an internal radius before depositing energy into the external shock.


We wish to thank the anonymous referee for his/ her careful reading of the paper. We also thank Daniele Malesani and Paolo Pagano for useful discussions and suggestions. This work is supported at INAF by funding from ASI through grant I/R/ 039/ 04 and by COFIN MIUR grant 2005025417, at Penn State by NASA contract NASS5-00136, and at the University of Leicester by the Science and Technology Facilities Council. We gratefully acknowledge the contributions of dozens of members of the XRT team at OAB, PSU, UL, GSFC, and ASDC and our subcontractors, who helped make this instrument possible.



Astrophysical Journal, 2007, 665 (1), pp. 599-607


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