GRB 060313: A New Paradigm for Short-Hard Bursts?

Abstract

We report the simultaneous observations of the prompt emission in the gamma-ray and hard X-ray bands by the Swift-BAT and the KONUS-Wind instruments of the short-hard burst, GRB 060313. The observations reveal multiple peaks in both the gamma-ray and hard X-ray bands suggesting a highly variable outflow from the central explosion. We also describe the early-time observations of the X-ray and UV/Optical afterglows by the Swift XRT and UVOT instruments. The combination of the X-ray and UV/Optical observations provide the most comprehensive lightcurves to date of a short-hard burst at such an early epoch. The afterglows exhibit complex structure with different decay indices and flaring. This behavior can be explained by the combination of a structured jet, radiative loss of energy, and decreasing microphysics parameters occurring in a circum-burst medium with densities varying by a factor of approximately two on a length scale of 10^17 cm. These density variations are normally associated with the environment of a massive star and inhomogeneities in its windy medium. However, the mean density of the observed medium (n approximately 10^−4 cm^3) is much less than that expected for a massive star. Although the collapse of a massive star as the origin of GRB 060313 is unlikely, the merger of a compact binary also poses problems for explaining the behavior of this burst. Two possible suggestions for explaining this scenario are: some short bursts may arise from a mechanism that does not invoke the conventional compact binary model, or soft late-time central engine activity is producing UV/optical but no X-ray flaring.

28 pages, 6 figures. Accepted for publication in ApJ. Clarifications made and typos corrected

References in corpus (7)

• X-Ray Flares from Postmerger Millisecond Pulsars
• A new definition of the intermediate group of gamma-ray bursts
• The X-ray afterglow of the short gamma ray burst 050724
• General Relativistic Binary Merger Simulations and Short Gamma Ray Bursts
• The faint afterglow and host galaxy of the short-hard GRB 060121
• Small-scale variations in the radiating surface of the GRB 011211 jet
• The Swift X-ray flaring afterglow of GRB 050607

Cited by in corpus (16)

• Discerning the physical origins of cosmological Gamma-ray bursts based on multiple observational criteria: the cases of z=6.7 GRB 080913, z=8.3 GRB 090423, and some short/hard GRBs
• The optically unbiased GRB host (TOUGH) survey. I. Survey design and catalogs
• The First Swift Ultra-Violet/Optical Telescope GRB Afterglow Catalog
• The Host Galaxies of Short-Duration Gamma-Ray Bursts: Luminosities, Metallicities, and Star Formation Rates
• Different progenitors of short hard gamma-ray bursts
• Swift observations of GRB 060614: an anomalous burst with a well behaved afterglow
• Smooth Light Curves from a Bumpy Ride: Relativistic Blast Wave Encounters a Density Jump
• The optical afterglows and host galaxies of three short/hard gamma-ray bursts
• The Prompt Gamma-Ray and Afterglow Energies of Short-Duration Gamma-Ray Bursts
• Multicolor observations of the afterglow of the short/hard GRB 050724
• Short Gamma Ray Bursts: a bimodal origin?
• On the nature of the short duration GRB 050906
• Gamma-ray burst afterglows
• Constraints on an optical afterglow and on supernova light following the short burst GRB 050813
• The Search for Primordial Black Holes Using Very Short Gamma Ray Bursts
• The Swift Discovery of X-ray Afterglows Accompanying Short Bursts from SGR 1900+14