Duration distributions for gamma-ray
bursts registered in various experiments
since WIND/KONUS up to Fermi/GBM
I. V. ARKHANGELSKAJA
National Research Nuclear University MEPhI (Moscow
Engineering Physics Institute)
VELA – more than 100 GRB since 1967-07-02
number of events
30
KONUS-WIND/VENERA_11-12 since sept 1978
141 GRB
20
10
0 -1
10
10
0
10
1
t90, s
10
2
Now more than 12000 GRB were registered by different detectors
Statistical analysis of some distributions:
Duration distributions on t50 and t90
t90 is the time of accumulation for 90% of burst statistics;
t50 is the time of accumulation for 50% of burst statistics
Hardness distributions on H32 and so on
H32 is defined as the ratio of fluence in third BATSE energy channel and
fluence in second BATSE energy channel
Distribution on E0
Other distributions …
But t50 is not informative criterium for multiepisodic bursts
Hardness distribution and t90 distribution
t50 =30.144  0.916 sec
t90 =53.888  0. 345 sec
BATSE 1B
The temporal
profiles of
GRB021008 on
AVS-F data and
RHESSI ones
The temporal
profiles of
GRB050525 on
AVS-F data and
RHESSI ones
The GRB930131
(BATSE trigger #2151)
temporal profiles on
BATSE and COMPTEL
data
The duration of GRB060418
- GRB spectral behavior
t90  58 s according to SWIFT data  - differences of sensitivity threshold and
t90  36 s according to RHESSI data
operation energy band between
RHESSI and SWIFT
11 GRB  for ½ t90(SWIFT)2×t90(RHESSI); for 1 t90(RHESSI)1.5 ×t90(SWIFT);
for 5 - comparable
these differences  in our investigation of various distributions in duration
Leads to small changes of duration distribution???
What does it mean “small”???
Where is separation point between short and long GRB ???
BATSE 1B
GRBs duration distributions for BATSE catalogues
N
300
5B, 2005, #8121 (~2700GRB)
250
200
4B, 29.08.96, #5585 (1235) GRB
3B, 19.09.94, #3174 (835 GRB)
2B, 09.03.93, #2230 (436 GRB)
1B, 05.03.92, #1446 (219 GRB)
150
100
50
0
0.01
0.1
1
10
t90 , sec
100
1000
250
NGRB
BATSE GRB
from catalogue
of nontriggered
events
200
150
100
BATSE GRB
from current
catalogue
~2050 GRBs
50
0
0.01
0.1
1
t90
10
100
1000
519 GRB
HXD-WAM
(Suzaku)
725 GRB
number of events
250
200
Fermi/GBM
1712 GRB
150
100
50
0 -3
10
10
-2
10
-1
10
0
10
1
t90, s
10
2
10
3
140
120
t90Fermi
100
80
60
40
20
0
0
50
100
t90swift
150
200
GRBs duration on SWIFT/BAT and Fermi/GBM data for
subset of bursts simultaneously registered by these
instruments
The redshift of this burst was defined in 1997 using KECK
spectrum of optical transient. Some spectral lines were
identified as shifted to z approximately 0.7 –
extragalactic&cosmological
Swift GRBs (274 bursts with known redshift) subset
duration distributions
without (dotted histogram)
and with (solid one) correction on redshift.
GRBs observed since 1967 and now several thousends of events
were listed in more than 15 catalogues.
Gamma-ray bursts duration distribution was the first analysed
using data of BATSE instrument onboard the CGRO. The GRBs
duration distribution analysis had shown the existence of two
bursts classes: long (t90 more than 2 s) and short (t90 less than 2 s).
But results of similar distributions for bursts observed by other
detectors have shown shifting of boundary between short and long
events from value of 2 s. For example, Swift/BAT GRBs subset
analysis give the value of ~1 s for this separator point. Moreover,
t90 has dependence from instrument registered this burst – it is
function of detector sensitivity threshold and operation energy
band. Therefore, the type of GGB (whether it short or long) should
be defined only taking into account distinctive features of
instrument detected this event and GRB redshift.
Firstly third intermediate GRBs subgroup was found some years
ago in BATSE GRB duration and duration-hardness distributions
and it appeared in events subsets for several other detectors.