Extended emission in short gamma-ray bursts registered by SPI-ACS of INTEGRAL observatory

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Extended emission in short gamma-ray bursts
registered by SPI-ACS of INTEGRAL observatory
Pavel Minaev 1, 2, Alexei Pozanenko 1, Vladimir
Loznikov 1 1- Space Research Institute (Moscow,
Russia) 2- Moscow State University (Moscow,
Russia)
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GRB duration classification

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Data selection and analyzed groups of events

• Data selection
• We have formed the list of short gamma-ray
  bursts, registered by SPI-ACS INTEGRAL in
  2002-2007, confirmed by other space-borne
  experiments (Swift, Konus, HETE etc), which
  consists of 86 events.
• Heavy particle triggers have been selected.
• Analyzed groups of events
• Confirmed short GRBs from our catalog (hereafter
  shown by black color)
• Unconfirmed short GRBs with T90lt2s (blue color)
• Unconfirmed short GRBs with T900.05s (green
  color)
• Heavy particle triggers (red color).

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Data analysis

• Alignment of time profiles against main peak
• Approximation of background by a linear law
• Subtraction of background model from time profile
• Calculation of averaged time profile for each
  group of events.

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Time profile of GRB060221
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Averaged time profiles of 2 groups of short
events, registered by SPI-ACS INTEGRAL

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Averaged time profiles of 2 groups of short
events, registered by SPI-ACS INTEGRAL

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Log N Log Cmax distribution
- 3/2

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Conclusions

• We have formed the list of short gamma-ray
  bursts, registered by SPI-ACS INTEGRAL in
  2002-2007, confirmed by other space-borne
  experiments (Swift, Konus, HETE etc), which
  consists of 86 events.
• The extended emission up to 25s after main peak
  has been found in averaged light curves of both
  confirmed and unconfirmed short GRBs registered
  by SPI-ACS INTEGRAL in energy band gt80keV
• The extended emission of the GRBs registered by
  SPI-ACS is in energy range above 80keV which may
  evidence against of explanation of extended
  emission as a rise of the afterglow.
• The evidence for extended emission in averaged
  light curve of unconfirmed short duration events
  of SPI-ACS supports the same origin of
  unconfirmed events as short duration gamma-ray
  bursts and increases the rate of INTEGRAL short
  duration bursts in three times, and the portion
  of short burst may be up to 45 of all Gamma-Ray
  bursts detected by SPI-ACS.
• The extended emission in averaged light curve of
  unconfirmed short duration events with T900.05s
  of SPI-ACS may evidence against of explanation of
  these events as evaporations of primordial black
  holes and supports the assumption, that these
  events have the same origin as short duration
  gamma-ray bursts with T90lt2s.