The puzzling temporally variable optical and X-ray afterglow of GRB 101024A

B. Gendre¹, G. Stratta¹, M. Laas-Bourez², D. M. Coward³, A. Klotz^4,5, S. Cutini¹, M. Boër⁵ and C. Stockdale⁶

¹ ASI Science Data Center, via Galileo Galilei, 00044 Frascati (RM), Italy
e-mail: bruce.gendre@asdc.asi.it
² University of Western Australia, School of Physics/ICRAR, W.A. 6009 Crawley, Australia
³ University of Western Australia, School of Physics, W.A. 6009 Crawley, Australia
⁴ Institut de Recherche en Astrophysique et Planetologie, 9 avenue du colonel Roche, 31028 Toulouse, France
⁵ Observatoire de Haute Provence (CNRS), 04780 Saint Michel l’Observatoire, France
⁶ Centre for Backyard Astrophysics, 3842 Churchill Victoria, Australia

Received: 27 February 2011
Accepted: 11 April 2011

Abstract

Aims. We present the optical observations of the afterglow of the Swift burst GRB 101024A and try to reconcile these observations with the X-ray afterglow data of GRB 101024A using current afterglow models

Methods. We employ early optical observations, using the Zadko Telescope combined with X-ray data, to compare them with the reverse shock/forward shock model.

Results. The early optical light curve reveals a very unusual steep decay index of α ~ 5. This is followed by a flattening and possibly a plateau phase coincident with a similar feature in the X-ray. We discuss these observations in the framework of the standard reverse shock/forward shock model and energy injection. The plateau phase might also be the signature of the formation of a new magnetar.