GRB 220609B

Y. Asaoka (ICRR), A. Yoshida, T. Sakamoto, S. Sugita (AGU), 
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
S. Torii, Y. Akaike, K. Kobayashi (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:

The long GRB 220609B triggered the CALET Gamma-ray
Burst Monitor (CGBM) at 12:21:07.969 UTC on 9 June 2022
(http://cgbm.calet.jp/cgbm_trigger/flight/1338812272/index.html).
The burst signal was seen by all CGBM detectors.

The burst light curve shows a multi-peaked structure which starts
at T-6.4 sec, peaks at T+7.9 sec, and ends at T+14.1 sec.
The T90 and T50 durations measured by the SGM data are 9.9 +/- 1.0 sec
and 3.5 +/- 0.2 sec (40-1000 keV), respectively.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1338812272/

The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.

R. Gopalakrishnan (IUCAA), V. Prasad (IUCAA), G. Waratkar (IITB), A. 
Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka 
University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report 
on behalf of the AstroSat CZTI collaboration:

Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 
2021, JApA, 42, 73) showed the detection of a long GRB 220609B which was 
also detected by CALET GBM (Asaoka et al., GCN Circ. 32185
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 ).

The source was clearly detected in the 20-200 keV energy range. The 
light curve peaks at 2022-06-09 12:21:15.65 UTC. The measured peak count 
rate associated with the burst is 1230 (+239, -53) counts/s above the 
background in the combined data of four quadrants, with a total of 6095 
(+298, -291) counts. The local mean background count rate was 411 (+3, 
-6) counts/s. Using cumulative rates, we measure a T90 of 11 (+1, -1) s.

It was also clearly detected in the CsI anticoincidence (Veto) detector 
in the 100-500 keV energy range. The light curve peaks at 2022-06-09 
12:21:15.42 UTC. The measured peak count rate is 4988 (+127, -136) 
counts/s above the background in the combined Veto data of four 
quadrants, with a total of 24547 (+545, -597) counts. The local mean 
background count rate was 1421 (+5, -5) counts/s. We measure a T90 of 11 
(+2, -1) s from the cumulative Veto light curve.

CZTI GRB detections are reported regularly on the payload site at 
http://astrosat.iucaa.in/czti/?q=grb. CZTI is built by a TIFR-led 
consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, 
and PRL. The Indian Space Research Organisation funded, managed, and 
facilitated the project.

A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin
on behalf of the MGNS/BepiColombo and HEND/Mars Odyssey teams,

J. Benkhoff on behalf of the BepiColombo team,

A. Ridnaia, D. Frederiks, D. Svinkin, A. Lysenko,
and T. Cline on behalf of the Konus-Wind team,

E. Bozzo and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

and

W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr,
and A.S. Gardner on on behalf of the GRS-Odyssey GRB team,
report:

The long-duration GRB 220609B
(CALET-CGBM detection: Asaoka et al., GCN Circ 32185
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 ;
AstroSat-CZTI detection: Gopalakrishnan et al., GCN Circ 32186
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 )
has been detected by Konus-Wind, CALET (CGBM), AstroSat (CZTI),
INTEGRAL (SPI-ACS), Mars-Odyssey (HEND), BepiColombo (MGNS),
and GECAM-B, so far, at about 44473 s UT (12:21:13).

We have triangulated it to a preliminary, 3 sigma error box
whose coordinates are:
 ---------------------------------------------
  RA(2000), deg                 Dec(2000), deg
 ---------------------------------------------
 Center:
  347.791 (23h 11m 10s)  +0.385 ( +0d 23' 05")
 Corners:
  348.003 (23h 12m 01s)  -0.627 ( +0d 37' 39")
  347.702 (23h 10m 49s)  +0.442 ( +0d 26' 31")
  347.634 (23h 10m 32s)  +1.229 ( +1d 13' 46")
  347.880 (23h 11m 31s)  +0.327 ( +0d 19' 37")
 ---------------------------------------------
The error box area is 515 sq. arcmin, and its maximum
dimension is 1.9 deg (the minimum one is 8.4 arcmin).
The Sun distance was 89 deg.

This box may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB220609_T44473/IPN/

The Konus-Wind time history and spectrum will be given in a forthcoming
GCN Circular.

D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin,
A. Tsvetkova,  M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:

The long GRB 220609B (CALET-CGBM detection: Asaoka et al., GCN Circ 32185
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 ;
AstroSat-CZTI detection: Gopalakrishnan et al., GCN Circ 32186
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 ;
IPN localization: Kozyrev et al., GCN 32190
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 )
triggered Konus-Wind (KW) at T0=44473.865 s UT (12:21:13.865).

The burst light curve shows a single emission pulse
which starts at ~T0-1.5 s and has a total duration of ~18 s.
The emission is seen up to ~10 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB220609_T44473/

As observed by Konus-Wind, the burst had
a fluence of (1.0 �� 0.1)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 4.544 s,
of (2.7 �� 0.2)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

The time-integrated spectrum (measured from T0 to T0+14.592 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.79 (-0.11,+0.13),
the high energy photon index beta = -2.02 (-0.14,+0.10),
the peak energy Ep = 537 (-86,+112) keV,
chi2 = 113/98 dof.

The spectrum near the peak count rate (measured from T0 to T0+6.400 s)
is best fit in the 20 keV - 15 MeV range
by a GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.83 (-0.06,+0.07),
the high energy photon index beta = -2.04 (-0.17,+0.12),
the peak energy Ep = 748 (-145,+170) keV,
chi2 = 88/97 dof.

All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.