GRB 240124B

J. Joshi (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 GRB 240124B. We also inspected INTEGRAL/SPI-ACS data, and see a detection there.

The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2024-01-24 21:14:33.25 UTC. The measured peak count rate associated with the burst is 386 (+141, -69) counts/s above the background in the combined data of three quadrants (out of four), with a total of 322 (+81, -76) counts. The local mean background count rate was 257 (+5, -10) counts/s. Using cumulative rates, we measure a T90 of 2.35 (+0.34, -0.9) s.

The source was also detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2024-01-23 21:14:31.78 UTC. The measured peak count rate associated with the burst is 710 (+72, -80) counts/s above the background in the combined data of all quadrants, with a total of 1164 (+159, -179) counts. The local mean background count rate was 1303 (+6, -8) counts/s. Due to the intrinsic 1 s binning of veto data, we cannot reliably estimate a T90 from it.

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.

CZTI GRB detections are reported regularly on the payload site at:
http://astrosat.iucaa.in/czti/?q=grb

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,

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

and 

G. Waratkar (IITB), J.Joshi (IUCAA), A. Vibhute (IUCAA),
V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA),
A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL)
on behalf of the Astrosat-CZTI team,

report:

The long-duration GRB 240124B
(AstroSat CZTI detection: Joshi et al., GCN 35636
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was detected by Konus-Wind, INTEGRAL (SPI-ACS),
Swift (BAT), and AstroSat (CZTI) 
at about 76474 s UT (21:14:34).
The burst was outside the coded field of view of the BAT.

We have triangulated this GRB to the following annuli:
---------------------------------------------------
annulus         R.A.     Dec.     R     dR (3sigma)
                (deg)    (deg)   (deg)     (deg)
---------------------------------------------------
Konus-SPI-ACS   114.536  21.719  79.082  2.281
Konus-BAT       112.129  19.162  79.550  1.622
---------------------------------------------------

The annuli combined with the KW ecliptic latitude response
give 254.7 sq.deg (3 sigma) localization region.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240124_T76473/IPN

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

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

The long-duration GRB 240124B
(AstroSat CZTI detection: Joshi et al., GCN 35636
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 ;
IPN triangulation: Ridnaia et al., GCN 35657
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triggered Konus-Wind at T0=76473.999 s UT (21:14:33.999).

The burst light curve shows a single-pulse structure
which starts at ~T0-1.1 s and has a total duration of ~4.0 s.
The emission is seen up to 3 MeV.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240124_T76473/

As observed by Konus-Wind, the burst
had a fluence of 4.57(-0.85,+2.93)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+0.228s,
of 4.33(-1.37,+3.93)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

A 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 = -1.40(-0.35,+0.44)
and Ep = 270(-94,+1040) keV (chi2 = 113/97 dof).
Fitting by a GRB (Band) model yields close alpha and Ep,
and an upper limit on the high energy photon index: beta < -1.9
(chi2 = 112/96 dof).

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