The X-ray afterglow of the short gamma ray burst 050724

¹ INAF - Osservatorio Astronomico di Brera, via Bianchi 46, 23807 Merate (LC), Italy e-mail: sergio.campana@brera.inaf.it
² JILA, Campus Box 440, University of Colorado, Boulder, CO 80309-0440, USA
³ Università degli studi di Milano-Bicocca, Dipartimento di Fisica, piazza delle Scienze 3, 20126 Milano, Italy
⁴ X-ray and Observational Astronomy Group, Department of Physics and Astronomy, University of Leicester, LE1 7RH, UK
⁵ INAF, Istituto di Astrofisica Spaziale e Fisica Cosmica di Palermo, via U. La Malfa 153, 90146 Palermo, Italy
⁶ ASI Science Data Center, via G. Galilei, 00044 Frascati (Roma), Italy
⁷ Department of Physics, University of Nevada, Box 454002, Las Vegas, NV 89154-4002, USA
⁸ NASA/Goddard Space Flight Center, Greenbelt Road, Greenbelt, MD20771, USA
⁹ Department of Astronomy and Astrophysics, Pennsylvania State University, 525 Davey Lab, University Park, PA 16802, USA

Received: 13 January 2006
Accepted: 14 March 2006

Abstract

Short duration (2 s) Gamma-ray bursts (GRBs) have been a mystery since their discovery. Until May 2005 very little was known about short GRBs, but this situation has changed rapidly in the last few months since the Swift and HETE-2 satellites have made it possible to discover X-ray and optical counterparts to these sources. Positional associations indicate that short GRBs arise in close-by galaxies (). Here we report on a detailed study of the short GRB 050724 X-ray afterglow. This burst shows strong flaring variability in the X-ray band. It clearly confirms early suggestions of X-ray activity in the 50–100 s time interval following the GRB onset seen with BATSE. Late flare activity is also observed. These observations support the idea that flares are related to the inner engine for short GRBs, as well as long GRBs.