GRB 250126A
GCN Circular 39035
Subject
GRB 250126A: Fermi GBM Final Real-time Localization
Date
2025-01-26T05:09:08Z (4 months ago)
From
Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply@GIOC.nsstc.nasa.gov>
Via
email
The Fermi GBM team reports the detection of a likely LONG GRB
At 04:58:50 UT on 26 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250126A (trigger 759560335.992228 / 250126208).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 337.4, Dec = -11.6 (J2000 degrees, equivalent to J2000 22h 29m, -11d 35'), with a statistical uncertainty of 2.2 degrees.
The angle from the Fermi LAT boresight is 69.0 degrees.
The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_skymap_all_bn250126208.png
The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_healpix_all_bn250126208.fit
The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
GCN Circular 39036
Subject
GRB 250126A: BALROG localization (Fermi Trigger 759560335 / GRB 250126208)
Date
2025-01-26T08:00:56Z (4 months ago)
From
Jochen Greiner at MPE <jcgrog@mpe.mpg.de>
Via
email
T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
759560335 at 04:58:50 on 26 Jan. 2025 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position is:
RA(2000.0) = 334.6 deg
Decl.(2000.0) = -15.8 deg
The 1 sigma statistical error radius is 2.0 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB250126208/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB250126208/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB250126208/json
GCN Circular 39038
Subject
GRB 250126A: MAXI/GSC detection
Date
2025-01-26T12:11:19Z (4 months ago)
From
Hitoshi Negoro at Nihon University/MAXI team <negoro.hitoshi@nihon-u.ac.jp>
Via
Web form
Y. Okada (Kyoto U.), H. Negoro (Nihon U.), Y. Kawakubo (AGU),
M. Nakajima, Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, K. Tatano, H. Nishio (Nihon U.),
T. Mihara, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN),
T. Sakamoto, M. Serino, S. Sugita, H. Hiramatsu, H. Nishikawa,
Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.),
M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech),
S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA),
Y. Ueda, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.),
K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.),
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered on a bright uncatalogued X-ray transient source,
probably GRB 250126A (GCN Circ. 39035, 39036), at 05:01:45 UT on January 26, 2025.
Assuming that the source flux was constant over the transit, we obtain the source position at
(R.A., Dec) = (337.621 deg, -14.383 deg) = (22 30 29, -14 22 58) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.32 deg and 0.23 deg, respectively.
The roll angle of the long axis from the north direction is 50.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The X-ray flux averaged over the scan was 148 +- 29 mCrab
(4.0-10.0keV, 1 sigma error).
Without assumptions on the source constancy, we obtain a rectangular error
box for the transient source with the following corners:
(R.A., Dec) = (337.049, -14.721) deg = (22 28 11, -14 43 15) (J2000)
(R.A., Dec) = (337.415, -14.977) deg = (22 29 39, -14 58 37) (J2000)
(R.A., Dec) = (338.598, -13.378) deg = (22 34 23, -13 22 40) (J2000)
(R.A., Dec) = (338.233, -13.124) deg = (22 32 55, -13 07 26) (J2000)
There was no significant excess flux in the previous transit at 03:29 UT
and in the next transit at 06:34 UT with an upper limit of 20 mCrab for each.
GCN Circular 39040
Subject
GRB 250126A: CALET Gamma-Ray Burst Monitor detection
Date
2025-01-26T15:05:47Z (4 months ago)
From
Yuta Kawakubo at Aoyama Gakuin University <kawakubo@phys.aoyama.ac.jp>
Via
Web form
S. Sugita, A. Yoshida, T. Sakamoto, 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 long GRB 250126A (Fermi GBM Final Real-time Localization:
Fermi GBM team, GCN Circ. 39035; BALROG localization: Preis et al.,
GCN Circ 39036; MAXI/GSC detection: Okada et al., GCN Circ 39038)
was detected in the ground analysis of the CALET Gamma-ray
Burst Monitor (CGBM) data around 04:58:50.99 on 26 January 2025 (referenced
to the Fermi-GBM Observation: GCN Circ. 39035).
(https://cgbm.calet.jp/cgbm_trigger/flight/1421902612/index.html).
The burst signal was seen by all CGBM detectors.
The burst light curve shows a multi-peaked structure that starts
at T-0.3 sec, peaks at T+85.4 sec, and ends at T+100.1 sec.
The T90 and T50 durations measured by the HXM2 data are 96.9 +/- 1.4 sec
and 82.5 +/- 1.3 sec (7-100 keV), respectively.
The ground-processed light curve is available at
https://cgbm.calet.jp/cgbm_trigger/ground/1421902612/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at Waseda University.