AAS 207th Meeting, 8-12 January 2006
Session 158 GRB: Short Bursts and Panchromatic Observations
Oral, Wednesday, 2:00-3:30pm, January 11, 2006, Virginia

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[158.04] The Broadband Afterglow of a Short-Hard Gamma-Ray Burst

D. B. Fox (Penn State University), React GRB Team

I will discuss our discovery, sub-arcsecond localization, and multiwavelength follow-up of the afterglow of GRB\,050709. This was the first short-hard burst (SHB) with a sub-arcsecond position and the first with a detected optical afterglow. Gemini spectroscopy reveals its host to be a subluminous star-forming galaxy at redshift z=0.16. The burst redshift, energy in prompt emission, and energy in relativistic ejecta are all well below the median values of these properties for the long-duration GRBs. At the same time, the values coincide well with previous inferences drawn from the luminosity function of BATSE SHBs. Our month-long imaging campaign with the Hubble Space Telescope places the afterglow in the context of its host galaxy and tracks its decay to I\rm AB>28\,mag. We observe the first jet break seen for any SHB, measure the burst collimation angle, and set stringent (extinction-free) limits on the brightness of any associated supernova. Based on these observations, we consider the binary merger scenario for SHBs strongly favored over alternate models.

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