A burst of new ideas

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A burst of new ideas

• Nature Vol 444
• 21/28 December 2006
• ??? HEAR group meeting 12/26 2006

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Gamma-ray bursts

• GRBs are intense and short bursts of ?-ray
  radiation that occur all over the sky 1/day at
  very large distances.
• two main classes of GRBs

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A burst defies the current scheme

• A novel explosive process is required for the
  ?-ray burst GRB 060614, Gal-Yam et al.
• An enigmatic long-lasting ?-ray burst not
  accompanied by a bright supernova. Della Valle
  et al.
• No supernovae associated with two long-duration
  ?-ray bursts, Johan P. U. Fynbo et al.
• A new ?-ray burst classification scheme from GRB
  060614, N. Gehrels et al.

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GRB 060614

• On 14 June 2006, at 1243 UT
• BAT on board the Swift satellite
• Duration T90 102 s (13-350keV)
• Detailed information was collected by the Swift
  BAT, XRT, and UVOT.
• at the outskirts of a relatively nearby faint
  dwarf galaxy at a redshift of z0.125

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light curve
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No associated SN !

• Any putative SN component must be more than 100
  times fainter than the faintest GRB-associated
  supernova SN2006aj.

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GRB 060614 short burst category?

• The spectral lag and low luminosity make it
  distinct from other long-duration GRBs

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GRB 060614 short burst category?

• Afterglow of the burst has a large offset from
  the star-forming region of the host galaxy.
• star formation rate 0.0084M?/yr
• small compared with those of normal long GRBs

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Probabilities

• A long GRB associated with a collapsing star
  Its progenitor is different from those of
  other long GRBs
• Merger-type short GRB
• These should not carry the name short.
• Prototype of a different, 3rd category of burst
• More data are needed
  Whether GRBs with similar properties
  will be detectable in elliptical host galaxies

Thank you !
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This image shows the durations of the 4B Catalog
Gamma-Ray Bursts recorded with the Burst and
Transient Source Experiment on board NASA's
Compton Gamma-Ray Observatory. The duration
parameter used is T90, which is the time over
which a burst emits from 5 of its total measured
counts to 95. The data used for the calculation
are the BATSE 4 energy channel discriminator
data. Lightcurves used for the calculation of T90
are integrated over all 4 channels (E gt 20 keV).