1. 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)

2. GRB duration classification ≤

3. 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. 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. Heavy particle triggers have been selected. Analyzed groups of events: Confirmed short GRBs from our catalog (hereafter shown by black color) Confirmed short GRBs from our catalog (hereafter shown by black color) Unconfirmed short GRBs with T 90 <2s (blue color) Unconfirmed short GRBs with T 90 <2s (blue color) Unconfirmed short GRBs with T 90 ≤0.05s (green color) Unconfirmed short GRBs with T 90 ≤0.05s (green color) Heavy particle triggers (red color). Heavy particle triggers (red color).

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

5. Time profile of GRB060221

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

7. ≤

8. Log N – Log C max distribution - 3/2 ≤

9. 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. 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 >80keV 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 >80keV 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 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 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 T 90 ≤0.05s 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 T 90 <2s. The extended emission in averaged light curve of unconfirmed short duration events with T 90 ≤0.05s 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 T 90 <2s.