GRB 240205A

The Fermi GBM team reports the detection of a likely SHORT GRB

At 20:26:30 UT on 5 Feb 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240205A (trigger 728857595.713148 / 240205852).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 300.9, Dec = 20.5 (J2000 degrees, equivalent to J2000 20h 03m, 20d 30'), with a statistical uncertainty of 6.0 degrees.

The angle from the Fermi LAT boresight is 57.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240205852/quicklook/glg_skymap_all_bn240205852.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240205852/quicklook/glg_healpix_all_bn240205852.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240205852/quicklook/glg_lc_medres34_bn240205852.gif

C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report:
 
The Glowbug gamma-ray telescope [1,2], operating on the International Space Station, reports the detection of the short GRB 240205A, which was also detected by Fermi/GBM (GCN 35679
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 ) and Konus-Wind (Trigger Time 20:26:26.689).
 
Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2024-02-05 20:26:29.640 with a duration of 0.29 s and a total significance of about 24.0 sigma.  The light curve comprises a single peak.
 
Using a standard power-law function with an exponential high-energy cutoff [3] to model the emission over this duration results in a photon index dN/dE~E^x of x=1.0 and a cutoff energy ("Epeak") of 310 keV.  The modeled 10-10000 keV fluence is 4.2e-07 erg/cm^2.
 
The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS.
 
Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC.  It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS.  The detector comprises 12 large-area (15 cm x 15 cm) CsI:Tl panels covering the surface of a half cube, and two hexagonal (5-cm diameter, 10-cm length) CLLB scintillators, giving it a large field of view (instantaneous FoV ~2/3 sky) over a wide energy band of 50 keV to >2 MeV.
 
[1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959
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[2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O
[3] Goldstein, A. et al. 2020, ApJ 895, 40, arXiv :1909.03006
 
Distribution Statement A: Approved for public release.  Distribution is unlimited.

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

A. Goldstein, M. S. Briggs, C. Wilson-Hodge,
and E. Burns on behalf of the Fermi GBM team,

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

and

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

The short-duration GRB 240205A
(Ferm-GBM detection: The Fermi GBM team, GCN 35679
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 ;
Glowbug detection: Cheung, et al.,  GCN 35707
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 )
was detected by Fermi (GBM trigger 728857595), Konus-Wind,
INTEGRAL (SPI-ACS), and Swift (BAT) at about 73591 s UT (20:26:31).
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-GBM     297.778  -19.219  40.665  0.735
GBM-SPI-ACS   180.960   84.546  70.289  6.208
---------------------------------------------------
The annuli intersect to form a long 60.9 sq.deg (3 sigma)
localization region.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB240205_T73586/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 short-duration GRB 240205A
(Fermi GBM Final Real-time Localization: GCN 35679
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 ;
Glowbug gamma-ray detection: Cheung et al., GCN 35707
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 ;
IPN triangulation: Svinkin et al., GCN 35710
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 )
triggered Konus-Wind at T0=73586.689 s UT (20:26:26.689).

The burst light curve shows a single pulse,
which starts at ~T0-0.2 s and has a total duration of ~0.45 s.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB240205_T73586/

As observed by Konus-Wind, the burst
had a fluence of 5.45(-0.84,+0.89)x10^-7 erg/cm2,
and a 16-ms peak flux, measured from T0-0.016 s,
of 4.13(-0.92,+1.08)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).

Since the brightest part of the burst emission
was detected before the trigger, the spectral analysis
was performed using the KW 3-channel light curve data.

Modelling the KW 3-channel time-integrated spectrum
(measured from T0-0.192 s to T0+0.256 s)
by a power law with exponential cutoff (CPL) model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep),
yields alpha = -0.10(-0.38,+0.48) and Ep = 241(-46,+52) keV.

Modelling the KW 3-channel spectrum near the peak count rate
(measured from T0-0.064 s to T0) by the CPL model
yields alpha = -0.30(-0.48,+0.64) and Ep = 317(-82,+136) keV.

All the quoted errors are at the 68% confidence level.
All the quoted values are preliminary.