Gamma-ray Burst 250126A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 26 Jan 25 04:59:02 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      59
TRIGGER_NUM:     759560335
GRB_RA:          334.300d {+22h 17m 12s} (J2000),
                 334.657d {+22h 18m 38s} (current),
                 333.587d {+22h 14m 21s} (1950)
GRB_DEC:         -30.650d {-30d 38' 59"} (J2000),
                 -30.524d {-30d 31' 26"} (current),
                 -30.900d {-30d 54' 00"} (1950)
GRB_ERROR:       9.65 [deg radius, statistical plus systematic]
GRB_INTEN:       206 [cnts/sec]
DATA_SIGNIF:     21.00 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20701 TJD;    26 DOY;   25/01/26
GRB_TIME:        17930.99 SOD {04:58:50.99} UT
GRB_PHI:         329.00 [deg]
GRB_THETA:        55.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.85
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic Transient
DETECTORS:       0,1,0, 1,0,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       308.88d {+20h 35m 30s}  -18.65d {-18d 38' 51"}
SUN_DIST:         26.19 [deg]   Sun_angle= -1.7 [hr] (East of Sun)
MOON_POSTN:      264.62d {+17h 38m 29s}  -28.43d {-28d 25' 49"}
MOON_DIST:        59.97 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       17.61,-56.22 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      324.89,-18.62 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 91.35,0.97 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 26 Jan 25 04:58:54 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      47
TRIGGER_NUM:     759560335
GRB_RA:          330.183d {+22h 00m 44s} (J2000),
                 330.552d {+22h 02m 13s} (current),
                 329.445d {+21h 57m 47s} (1950)
GRB_DEC:         -34.717d {-34d 43' 00"} (J2000),
                 -34.595d {-34d 35' 42"} (current),
                 -34.957d {-34d 57' 25"} (1950)
GRB_ERROR:       22.23 [deg radius, statistical plus systematic]
GRB_INTEN:       137 [cnts/sec]
DATA_SIGNIF:     7.40 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20701 TJD;    26 DOY;   25/01/26
GRB_TIME:        17930.99 SOD {04:58:50.99} UT
GRB_PHI:         327.00 [deg]
GRB_THETA:        50.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.97
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      94%  GRB
2nd_MOST_LIKELY:   3%  Solar Flare
DETECTORS:       0,1,0, 1,0,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       308.88d {+20h 35m 30s}  -18.65d {-18d 38' 52"}
SUN_DIST:         24.99 [deg]   Sun_angle= -1.4 [hr] (East of Sun)
MOON_POSTN:      264.62d {+17h 38m 29s}  -28.43d {-28d 25' 49"}
MOON_DIST:        55.56 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       10.39,-52.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      319.85,-21.10 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 91.35,0.97 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 26 Jan 25 04:59:09 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     759560335
GRB_RA:          336.510d {+22h 26m 02s} (J2000),
                 336.845d {+22h 27m 23s} (current),
                 335.842d {+22h 23m 22s} (1950)
GRB_DEC:         -13.590d {-13d 35' 23"} (J2000),
                 -13.462d {-13d 27' 42"} (current),
                 -13.845d {-13d 50' 40"} (1950)
GRB_ERROR:       2.80 [deg radius, statistical only]
DATA_SIGNIF:     28.00 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20701 TJD;    26 DOY;   25/01/26
GRB_TIME:        17930.99 SOD {04:58:50.99} UT
GRB_PHI:         343.00 [deg]
GRB_THETA:        67.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       308.88d {+20h 35m 30s}  -18.65d {-18d 38' 51"}
SUN_DIST:         27.34 [deg]   Sun_angle= -1.9 [hr] (East of Sun)
MOON_POSTN:      264.62d {+17h 38m 29s}  -28.43d {-28d 25' 49"}
MOON_DIST:        68.16 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       47.33,-53.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      333.27, -3.52 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_759560335.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 26 Jan 25 05:00:00 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     759560335
GRB_RA:          334.930d {+22h 19m 43s} (J2000),
                 335.267d {+22h 21m 04s} (current),
                 334.257d {+22h 17m 02s} (1950)
GRB_DEC:         -15.000d {-15d 00' 00"} (J2000),
                 -14.873d {-14d 52' 23"} (current),
                 -15.251d {-15d 15' 04"} (1950)
GRB_ERROR:       2.47 [deg radius, statistical only]
DATA_SIGNIF:     31.80 [sigma]
DATA_INTERVAL:   8.192 [sec]
GRB_DATE:        20701 TJD;    26 DOY;   25/01/26
GRB_TIME:        17930.99 SOD {04:58:50.99} UT
GRB_PHI:         343.00 [deg]
GRB_THETA:        65.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       308.88d {+20h 35m 30s}  -18.65d {-18d 38' 51"}
SUN_DIST:         25.53 [deg]   Sun_angle= -1.8 [hr] (East of Sun)
MOON_POSTN:      264.63d {+17h 38m 32s}  -28.43d {-28d 25' 50"}
MOON_DIST:        66.17 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       44.09,-52.76 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      331.33, -4.28 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_759560335.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 26 Jan 25 05:00:20 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      3
TRIGGER_NUM:     759560335
GRB_RA:          336.660d {+22h 26m 38s} (J2000),
                 336.993d {+22h 27m 58s} (current),
                 335.995d {+22h 23m 59s} (1950)
GRB_DEC:         -12.200d {-12d 11' 59"} (J2000),
                 -12.072d {-12d 04' 17"} (current),
                 -12.455d {-12d 27' 17"} (1950)
GRB_ERROR:       2.36 [deg radius, statistical only]
DATA_SIGNIF:     35.60 [sigma]
DATA_INTERVAL:   15.360 [sec]
GRB_DATE:        20701 TJD;    26 DOY;   25/01/26
GRB_TIME:        17930.99 SOD {04:58:50.99} UT
GRB_PHI:         344.00 [deg]
GRB_THETA:        68.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       308.88d {+20h 35m 30s}  -18.65d {-18d 38' 51"}
SUN_DIST:         27.86 [deg]   Sun_angle= -1.9 [hr] (East of Sun)
MOON_POSTN:      264.63d {+17h 38m 32s}  -28.43d {-28d 25' 51"}
MOON_DIST:        68.89 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       49.49,-52.97 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      333.92, -2.28 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_759560335.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 26 Jan 25 05:07:59 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     759560335
GRB_RA:          337.400d {+22h 29m 36s} (J2000),
                 337.732d {+22h 30m 56s} (current),
                 336.737d {+22h 26m 57s} (1950)
GRB_DEC:         -11.610d {-11d 36' 35"} (J2000),
                 -11.481d {-11d 28' 51"} (current),
                 -11.866d {-11d 51' 58"} (1950)
GRB_ERROR:       2.20 [deg radius, statistical only]
GRB_DATE:        20701 TJD;    26 DOY;   25/01/26
GRB_TIME:        17930.99 SOD {04:58:50.99} UT
GRB_PHI:         344.00 [deg]
GRB_THETA:        69.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       308.88d {+20h 35m 32s}  -18.65d {-18d 38' 46"}
SUN_DIST:         28.72 [deg]   Sun_angle= -1.9 [hr] (East of Sun)
MOON_POSTN:      264.71d {+17h 38m 51s}  -28.43d {-28d 26' 01"}
MOON_DIST:        69.73 [deg]
MOON_ILLUM:      12 [%]
GAL_COORDS:       50.94,-53.31 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      334.81, -2.00 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_lc_medres34_bn250126208.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250126208/quicklook/glg_locplot_all_bn250126208.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.

GCN Circular #39035
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
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
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
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.

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Jochen Greiner, last update: 26-Jan-2025 [Disclaimer]