GRB 180529A

V. Sharma and D. Bhattacharya (IUCAA), V. Bhalerao (IIT-B), A. R. Rao (TIFR) and S. Vadawale (PRL) report on behalf of the Astrosat CZTI collaboration:

Analysis of Astrosat CZTI data showed the detection of a short GRB 180529A, which was also detected by IPN Triangulation (Hurley K. et al., GCN 22748
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 ), CALET (Onozawa H., GCN 22749
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 ) and Konus-Wind (Svinkin D. et al., GCN 22750
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 ).

The source was clearly detected in the 40-200 keV energy range. The light curve shows multiple peaks of emission with strongest peak at 08:29:15.5 UT. The measured peak count rate is 346.4 cts/s above the background in combined data of four quadrants, with a total of 508 cts. The local mean background count rate was 496.5 cts/s. Using cumulative rates, we measure a T90 of 2.9 s.

It was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range.

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, ISAC, IUCAA, SAC and PRL. The Indian Space Research Organisation funded, managed and facilitated the project.

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks,
M. Ulanov, A. Tsvetkova, A. Lysenko, A.Kozlova, and T. Cline
on behalf of the Konus-Wind team, report:

The short-duration, bright GRB 180529A
(AGILE-MCAL detection: Ursi et al., GCN Circ. 22741
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 ;
IPN triangulation: Hurley et al., GCN Circ. 22748
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 ;
CALET-CGBM detection: Onozawa et al., GCN Circ. 22749
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 )
triggered Konus-Wind at T0=30554.458 s UT (08:29:14.458).

The burst light curve shows a multi-peaked structure
which starts at ~T0-0.5 s and has a total duration of ~1.7 s.
The emission is seen up to ~6 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180529_T30554/

As observed by Konus-Wind, the burst
had a fluence of 1.08(-0.22,+0.30)x10^-5 erg/cm2,
and a 16-ms peak flux, measured from T0+0.446 s,
of 1.65(-0.61,+0.71)x10^-5 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 10 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with  alpha = -0.71(-0.21,+0.26)
and Ep = 1046(-295,+502) keV (chi2 = 99/84 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 99/83 dof).

All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.

H. Onozawa, A. Yoshida, T. Sakamoto, V. Pal'shin, Y. Kawakubo,
A. Tezuka, S. Matsukawa (AGU), K. Yamaoka (Nagoya U),
S. Nakahira (RIKEN), I. Takahashi (IPMU), Y. Asaoka, S. Ozawa,
S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
W. Ishizaki (ICRR), M. L. Cherry (LSU), S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:

The short GRB 180529A (AGILE-MCAL detection: Ursi et al.,
GCN Circ. 22741
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 ; IPN triangulation: Hurley et al., GCN Circ. 22748
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 )
triggered the CALET Gamma-ray Burst Monitor (CGBM) at
08:29:14.435 UTC on 29 May 2018.  The burst signal was seen
by all CGBM detectors.

The burst light curve shows a single multi-peaked pulse which starts
at T+0.06 sec, peaks at T+1.15 sec and ends at T+3.14 sec.
The T90 and the T50 durations measured by the SGM data are
2.18 +- 0.69 sec and 0.83 +- 0.18 sec (40-1000 keV), respectively.
There is no any sign of the possible short precursor reported
by Ursi et a. (GCN Circ. 22741
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 ) in the CGBM event data which
comprise the time interval from ~T-165 sec to T+507 sec.

The ground processed light curve is available at

http://cgbm.calet.jp/cgbm_trigger/ground/1211617728/

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

K. Hurley, on behalf of the IPN,

I. G. Mitrofanov, D. Golovin, M. L. Litvak, and A. B. Sanin,
on behalf of the HEND-Odyssey GRB team,

D. Svinkin, S. Golenetskii, R. Aptekar, D. Frederiks, A. Kozlova,
and T. Cline on behalf of the Konus-Wind team,

A. von Kienlin, X. Zhang, A. Rau, V. Savchenko, E. Bozzo,
and C. Ferrigno, on behalf of the INTEGRAL SPI-ACS GRB team,

S. Barthelmy, J. Cummings, H. Krimm, and D. Palmer,
on behalf of the Swift-BAT team,

A. Ursi, N. Parmiggiani, F. Verrecchia, A. Bulgarelli,
A. Trois, M. Marisaldi, C. Pittori, M. Tavani, Y. Evangelista,
I. Donnarumma, M. Cardillo, G. Piano, G. Minervini, A. Argan,
F. Lucarelli, A. Zoli, V. Fioretti, F. Fuschino, M. Pilia,
F. Longo, A. Giuliani on behalf of the AGILE team, and

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

The short-duration GRB 180529A (Ursi et al., GCN Circ. 22741
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 )
was detected by AGILE (MCAL), Konus-Wind, Mars-Odyssey (HEND),
INTEGRAL (SPI-ACS), CALET (CGBM), and Swift (BAT)
at about 30554 s UT (08:29:14).
The burst was outside the coded field of view of the BAT.

We have triangulated it to a preliminary, 3 sigma error box whose 
coordinates are:
  ---------------------------------------------
   RA(2000), deg                 Dec(2000), deg
  ---------------------------------------------
  Center:
    97.947 (06h 31m 47s) -54.908 (-54d 54' 28")
  Corners:
    96.714 (06h 26m 51s) -54.840 (-54d 50' 23")
    98.264 (06h 33m 03s) -55.310 (-55d 18' 34")
    99.183 (06h 36m 44s) -54.962 (-54d 57' 43")
    97.637 (06h 30m 33s) -54.505 (-54d 30' 19")
  ---------------------------------------------
The error box area is 1976 sq. arcmin, and its maximum
dimension is 1.42 deg (the minimum one is 32.9 arcmin).
The Sun distance was 80 deg.

This box may be improved.

A triangulation map is posted at
http://www.ioffe.ru/LEA/GRBs/GRB180529_T30554/IPN

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