GRB 250107D

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

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

E. Burns on behalf of the IPN,

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

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 short-duration GRB 250107D
was detected by Konus-Wind, INTEGRAL (SPI-ACS),
Swift (BAT), and Mars-Odyssey(HEND), at about 19406 s UT (05:23:26).
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:
  259.300 (17h 17m 12s) -29.710 (-29d 42' 37")
 Corners:
  259.267 (17h 17m 04s) -28.346 (-28d 20' 46")
  259.147 (17h 16m 35s) -30.541 (-30d 32' 29")
  259.382 (17h 17m 32s) -30.988 (-30d 59' 15")
  259.469 (17h 17m 52s) -28.855 (-28d 51' 18")
 ---------------------------------------------
The error box area is 1635 sq. arcmin, and its maximum
dimension is 2.6 deg (the minimum one is 12.6 arcmin).
The Sun distance was 27 deg.

This localization may be improved.

A triangulation map and HEALPix FITS file are posted at
http://www.ioffe.ru/LEA/GRBs/GRB250107_T19411/IPN/
The HEALPix triangulation map is the multi-order HEALPix in units of
probability density.

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 GRB 250107D (IPN triangulation: Kozyrev et al., GCN 38880
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 )
triggered Konus-Wind (KW) at T0=19411.897 s UT (05:23:31.897).

The burst light curve shows a single, multi-peaked emission pulse
which starts at ~T0-0.112 s and has a duration of ~0.208 s.

The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB250107_T19411/

As observed by Konus-Wind, the burst had
the total fluence of 2.06(-0.34,+0.62)x10^-6 erg/cm^2
and a 16-ms peak energy flux, measured from T0-0.064 s,
of 1.99(-0.32,+0.59)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).

Since a major part of the burst emission was detected before the trigger time,
the time-averaged spectral analysis was performed using the KW 3-channel light curve data.
Modeling the 3-channel time-integrated spectrum (measured from T0-0.112 s to T0+0.096 s)
by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
yields alpha = -0.40 (-0.32, + 0.41) and Ep = 897(-203,+453) keV.

All the quoted errors are estimated at the 68% confidence level.
All the presented results are preliminary.

T. Sakamoto, A. Yoshida, S. Sugita, Y. Kawakubo (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), 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 short GRB 250107D (IPN triangulation: Kozyrev et al., GCN Circ. 38880
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 ;
Konus-Wind detection: Frederiks et al., GCN Circ. 38881
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 ) triggered the CALET
Gamma-ray Burst Monitor (CGBM) at 05:23:36.72 UTC on 7 January 2025
(https://cgbm.calet.jp/cgbm_trigger/flight/1420262534/index.html).
The burst signal was seen by only the SGM detector.  Because of a problem with the ground 
alert processing script, the GCN notice was not distributed automatically for this event.

The burst light curve shows a single pulse that starts
at T+0.17 sec, peaks at T+0.25 sec, and ends at T+0.32 sec.
The T90 and T50 durations measured by the SGM data are 0.13 +/- 0.03 sec
and 0.08 +/- 0.02 sec (40-1000 keV), respectively.

The ground-processed light curve is available at

https://cgbm.calet.jp/cgbm_trigger/ground/1420262534/

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

A. Pal (Konkoly Observatory), M. Dafcikova, J. Ripa, M. Kolar, N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, L. Szakszonova, J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal,  A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory),  T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration.

The long-duration GRB 250107D (IPN Triangulation: GCN 38880
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 ; Konus/Wind detection: GCN 38881
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 ; CALET/CGBM detection: GCN 38897
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 ; INTEGRAL/SPI-ACS peak detection at 2025-01-07 ~05:23:36 UTC) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract).

The detection was confirmed at the peak time 2025-01-07 05:23:36.7 UTC. The T90 duration measured by GRBAlpha is 0.5 s and the overall significance during T90 reaches 6.6 sigma in the ~120-400 keV band.

The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250107D_GCN.pdf

All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/
GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume.