Gamma-ray Burst 250128B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:23:07 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1285677,   Seg_Num: 0
GRB_RA:          231.420d {+15h 25m 41s} (J2000),
                 231.742d {+15h 26m 58s} (current),
                 230.778d {+15h 23m 07s} (1950)
GRB_DEC:          -0.517d {-00d 31' 01"} (J2000),
                  -0.604d {-00d 36' 13"} (current),
                  -0.342d {-00d 20' 31"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       438 [cnts]    Image_Peak=58 [image_cnts]
TRIGGER_DUR:     0.064 [sec] 
TRIGGER_INDEX:   10418     E_range: 25-100 keV
BKG_INTEN:       16604 [cnts]
BKG_TIME:        58957.02 SOD {16:22:37.02} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20703 TJD;    28 DOY;   25/01/28
GRB_TIME:        58973.66 SOD {16:22:53.66} UT
GRB_PHI:         -15.64 [deg]
GRB_THETA:        18.21 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     24.75 [sigma]
IMAGE_SIGNIF:    7.64 [sigma]
MERIT_PARAMS:     +1  +0  +0  -4  +2  -2  +0  +0 -16  +0 
SUN_POSTN:       311.44d {+20h 45m 45s}  -18.00d {-18d 00' 09"}
SUN_DIST:         80.02 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.27d {+20h 05m 04s}  -24.90d {-24d 53' 51"}
MOON_DIST:        71.23 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.61, 43.77 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      229.14, 17.62 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Coordinates.  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 174.89,-5.45 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=759774178).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:23:24 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      45
TRIGGER_NUM:     759774178
GRB_RA:          229.267d {+15h 17m 04s} (J2000),
                 229.489d {+15h 17m 57s} (current),
                 228.823d {+15h 15m 17s} (1950)
GRB_DEC:         +43.000d {+43d 00' 00"} (J2000),
                 +42.909d {+42d 54' 33"} (current),
                 +43.182d {+43d 10' 57"} (1950)
GRB_ERROR:       24.97 [deg radius, statistical plus systematic]
GRB_INTEN:       308 [cnts/sec]
DATA_SIGNIF:     5.40 [sigma]
INTEG_TIME:      0.128 [sec]
GRB_DATE:        20703 TJD;    28 DOY;   25/01/28
GRB_TIME:        58973.77 SOD {16:22:53.77} UT
GRB_PHI:         295.00 [deg]
GRB_THETA:        50.00 [deg]
DATA_TIME_SCALE: 0.1280 [sec]
HARD_RATIO:      1.23
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      97%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       0,0,0, 1,1,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:       311.44d {+20h 45m 45s}  -18.00d {-18d 00' 09"}
SUN_DIST:         96.48 [deg]   Sun_angle= 5.5 [hr] (West of Sun)
MOON_POSTN:      301.27d {+20h 05m 05s}  -24.90d {-24d 53' 49"}
MOON_DIST:        94.53 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       70.89, 56.60 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      206.43, 57.80 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128683/quicklook/glg_lc_medres34_bn250128683.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 148.90,23.73 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1285677).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:23:40 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     759774178
GRB_RA:          239.880d {+15h 59m 31s} (J2000),
                 240.166d {+16h 00m 40s} (current),
                 239.311d {+15h 57m 15s} (1950)
GRB_DEC:         +16.490d {+16d 29' 24"} (J2000),
                 +16.420d {+16d 25' 13"} (current),
                 +16.631d {+16d 37' 51"} (1950)
GRB_ERROR:       19.91 [deg radius, statistical only]
DATA_SIGNIF:     5.40 [sigma]
DATA_INTERVAL:   0.128 [sec]
GRB_DATE:        20703 TJD;    28 DOY;   25/01/28
GRB_TIME:        58973.77 SOD {16:22:53.77} UT
GRB_PHI:         294.00 [deg]
GRB_THETA:        78.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:       311.44d {+20h 45m 45s}  -18.00d {-18d 00' 09"}
SUN_DIST:         78.14 [deg]   Sun_angle= 4.8 [hr] (West of Sun)
MOON_POSTN:      301.27d {+20h 05m 06s}  -24.90d {-24d 53' 47"}
MOON_DIST:        72.46 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:       29.22, 45.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      233.41, 36.18 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128683/quicklook/glg_lc_medres34_bn250128683.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_759774178.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.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1285677).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:32:18 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     759774178
GRB_RA:          264.750d {+17h 39m 00s} (J2000),
                 265.219d {+17h 40m 52s} (current),
                 263.816d {+17h 35m 16s} (1950)
GRB_DEC:         -46.640d {-46d 38' 23"} (J2000),
                 -46.652d {-46d 39' 07"} (current),
                 -46.612d {-46d 36' 43"} (1950)
GRB_ERROR:       8.18 [deg radius, statistical only]
GRB_DATE:        20703 TJD;    28 DOY;   25/01/28
GRB_TIME:        58973.77 SOD {16:22:53.77} UT
GRB_PHI:         294.00 [deg]
GRB_THETA:       145.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:       311.44d {+20h 45m 46s}  -18.00d {-18d 00' 03"}
SUN_DIST:         47.44 [deg]   Sun_angle= 3.1 [hr] (West of Sun)
MOON_POSTN:      301.36d {+20h 05m 27s}  -24.88d {-24d 52' 33"}
MOON_DIST:        36.02 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      344.17, -8.14 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      266.08,-23.27 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128683/quicklook/glg_lc_medres34_bn250128683.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128683/quicklook/glg_locplot_all_bn250128683.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:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Short GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1285677).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:24:22 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.412d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.517d {-00d 31' 01"} (J2000)
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59052.35 SOD {16:24:12.35} UT,   78.7 [sec] since BAT Trigger Time
COUNTS:          39    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        4    Max_iter_allowed= 4
ERROR_CODE:      2
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        Algorithm did not converge; too many iterations.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:26:52 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1285677,   Seg_Num: 0
GRB_RA:          231.420d {+15h 25m 41s} (J2000),
                 231.742d {+15h 26m 58s} (current),
                 230.778d {+15h 23m 07s} (1950)
GRB_DEC:          -0.517d {-00d 31' 01"} (J2000),
                  -0.604d {-00d 36' 13"} (current),
                  -0.342d {-00d 20' 31"} (1950)
GRB_DATE:        20703 TJD;    28 DOY;   25/01/28
GRB_TIME:        58973.71 SOD {16:22:53.71} UT
TRIGGER_INDEX:   10418
GRB_PHI:         -15.64 [deg]
GRB_THETA:        18.21 [deg]
DELTA_TIME:      -68.00 [sec]
TRIGGER_DUR:     0.064 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     24.75 [sigma]
IMAGE_SIGNIF:    7.64 [sigma]
LC_URL:          sw01285677000msb.lc
SUN_POSTN:       311.44d {+20h 45m 45s}  -18.00d {-18d 00' 07"}
SUN_DIST:         80.02 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.31d {+20h 05m 14s}  -24.89d {-24d 53' 20"}
MOON_DIST:        71.27 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.61, 43.77 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      229.14, 17.62 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT-BAT GRB Lightcurve.  
COMMENTS:           
COMMENTS:        The next comments were copied from the BAT_POS Notice:  
COMMENTS:        This is a rate trigger.  
COMMENTS:        A point_source was found.  
COMMENTS:        This does not match any source in the on-board catalog.  
COMMENTS:        This does not match any source in the ground catalog.  
COMMENTS:        This is a GRB.  
COMMENTS:        This trigger occurred at longitude,latitude = 174.89,-5.45 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:27:15 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.412d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.517d {-00d 31' 00"} (J2000)
POINT_ROLL:      108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59056.34 SOD {16:24:16.34} UT,   82.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.196
N_STARS:         34
X_OFFSET:        521 [pixels]
Y_OFFSET:        525 [pixels]
X_MAX:           1480 [pixels]
Y_MAX:           1484 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01285677000msufc0082.fits
SUN_POSTN:       311.44d {+20h 45m 46s}  -18.00d {-18d 00' 06"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.31d {+20h 05m 14s}  -24.89d {-24d 53' 16"}
MOON_DIST:        71.28 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:27:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.412d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.517d {-00d 31' 00"} (J2000)
POINT_ROLL:      108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59056.34 SOD {16:24:16.34} UT,   82.7 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.196
N_STARS:         34
X_OFFSET:        521 [pixels]
Y_OFFSET:        525 [pixels]
X_MAX:           1480 [pixels]
Y_MAX:           1484 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01285677000msufc0082.fits
SUN_POSTN:       311.44d {+20h 45m 46s}  -18.00d {-18d 00' 06"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.31d {+20h 05m 15s}  -24.89d {-24d 53' 14"}
MOON_DIST:        71.28 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:28:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.412d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.517d {-00d 31' 00"} (J2000)
ROLL:            108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59056.34 SOD {16:24:16.34} UT,   82.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     759774291
X_OFFSET:        840 [pixels]
Y_OFFSET:        844 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1000
Y_GRB_POS:       1004
BINNING_INDEX:   1
IM_URL:          sw01285677000msuni0117.fits
SUN_POSTN:       311.44d {+20h 45m 46s}  -18.00d {-18d 00' 05"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.32d {+20h 05m 18s}  -24.88d {-24d 53' 05"}
MOON_DIST:        71.29 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:28:48 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.412d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.517d {-00d 31' 00"} (J2000)
ROLL:            108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59056.34 SOD {16:24:16.34} UT,   82.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     759774291
X_OFFSET:        840 [pixels]
Y_OFFSET:        844 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1000
Y_GRB_POS:       1004
BINNING_INDEX:   1
IM_URL:          sw01285677000msuni0117.fits
SUN_POSTN:       311.44d {+20h 45m 46s}  -18.00d {-18d 00' 05"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.33d {+20h 05m 18s}  -24.88d {-24d 53' 03"}
MOON_DIST:        71.29 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:31:21 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1285677,   Seg_Num: 0
GRB_RA:          231.4254d {+15h 25m 42.09s} (J2000),
                 231.7478d {+15h 26m 59.47s} (current),
                 230.7832d {+15h 23m 07.96s} (1950)
GRB_DEC:          -0.5392d {-00d 32' 21.1"} (J2000),
                  -0.6259d {-00d 37' 33.3"} (current),
                  -0.3644d {-00d 21' 51.7"} (1950)
GRB_ERROR:       4.2 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59060.00 SOD {16:24:20.00} UT,   86.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       311.44d {+20h 45m 46s}  -18.00d {-18d 00' 04"}
SUN_DIST:         80.01 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.35d {+20h 05m 24s}  -24.88d {-24d 52' 42"}
MOON_DIST:        71.29 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.59, 43.75 [deg] galactic lon,lat of the burst
ECL_COORDS:      229.15, 17.60 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN Circular #39057
The Fermi GBM team reports the detection of a likely SHORT GRB
At 16:22:53 UT on 28 Jan 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250128B (trigger 759774178.772694 / 250128683).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 264.8, Dec = -46.6 (J2000 degrees, equivalent to J2000 17h 39m, -46d 36'), with a statistical uncertainty of 8.2 degrees.
The angle from the Fermi LAT boresight is 145.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128683/quicklook/glg_skymap_all_bn250128683.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/bn250128683/quicklook/glg_healpix_all_bn250128683.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250128683/quicklook/glg_lc_medres34_bn250128683.gif

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:36:07 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.413d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.515d {-00d 30' 54"} (J2000)
POINT_ROLL:      108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59268.38 SOD {16:27:48.38} UT,   294.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.898
N_STARS:         55
X_OFFSET:        281 [pixels]
Y_OFFSET:        285 [pixels]
X_MAX:           1720 [pixels]
Y_MAX:           1724 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01285677000msufc0294.fits
SUN_POSTN:       311.45d {+20h 45m 47s}  -18.00d {-18d 00' 00"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.40d {+20h 05m 36s}  -24.87d {-24d 52' 01"}
MOON_DIST:        71.36 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:37:29 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.413d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.515d {-00d 30' 54"} (J2000)
ROLL:            108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59268.38 SOD {16:27:48.38} UT,   294.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     759774503
X_OFFSET:        840 [pixels]
Y_OFFSET:        844 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1000
Y_GRB_POS:       1004
BINNING_INDEX:   1
IM_URL:          sw01285677000msuni0329.fits
SUN_POSTN:       311.45d {+20h 45m 47s}  -18.00d {-18d 00' 00"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.41d {+20h 05m 39s}  -24.86d {-24d 51' 49"}
MOON_DIST:        71.37 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:37:05 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1285677,   Seg_Num: 0
GRB_RA:          231.4253d {+15h 25m 42.07s} (J2000),
                 231.7477d {+15h 26m 59.45s} (current),
                 230.7831d {+15h 23m 07.93s} (1950)
GRB_DEC:          -0.5396d {-00d 32' 22.5"} (J2000),
                  -0.6263d {-00d 37' 34.8"} (current),
                  -0.3648d {-00d 21' 53.2"} (1950)
GRB_ERROR:       1.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59060.00 SOD {16:24:20.00} UT,   86.3 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       311.45d {+20h 45m 47s}  -18.00d {-18d 00' 00"}
SUN_DIST:         80.01 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.41d {+20h 05m 38s}  -24.86d {-24d 51' 53"}
MOON_DIST:        71.34 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.59, 43.75 [deg] galactic lon,lat of the burst
ECL_COORDS:      229.15, 17.60 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 1.1% < P(seren) < 2.8%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:37:42 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.413d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.515d {-00d 30' 54"} (J2000)
ROLL:            108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59268.38 SOD {16:27:48.38} UT,   294.7 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     759774503
X_OFFSET:        840 [pixels]
Y_OFFSET:        844 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1000
Y_GRB_POS:       1004
BINNING_INDEX:   1
IM_URL:          sw01285677000msuni0329.fits
SUN_POSTN:       311.45d {+20h 45m 47s}  -18.00d {-18d 00' 00"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.42d {+20h 05m 40s}  -24.86d {-24d 51' 47"}
MOON_DIST:        71.37 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #39058
P. A. Evans (U Leicester), R. A. J. Eyles-Ferris (U Leicester), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 16:22:53 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250128B (trigger=1285677). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 231.420, -0.517 which is
```
   RA(J2000) = 15h 25m 41s
   Dec(J2000) = -00d 31' 01"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 0.5 sec. The peak count rate was ~5578 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 16:24:12.3 UT, 78.6 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 231.42552, -0.53970 which is equivalent to:
```
   RA(J2000)  = 15h 25m 42.12s
   Dec(J2000) = -00d 32' 22.9"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 84 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density consistent with the Galactic value of 8.00 x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 82 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.121.
Burst Advocate for this burst is P. A. Evans (pae9 AT leicester.ac.uk). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:36:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.413d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.515d {-00d 30' 54"} (J2000)
POINT_ROLL:      108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59268.38 SOD {16:27:48.38} UT,   294.7 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.898
N_STARS:         55
X_OFFSET:        281 [pixels]
Y_OFFSET:        285 [pixels]
X_MAX:           1720 [pixels]
Y_MAX:           1724 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01285677000msufc0294.fits
SUN_POSTN:       311.45d {+20h 45m 47s}  -18.00d {-18d 00' 00"}
SUN_DIST:         80.03 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.40d {+20h 05m 37s}  -24.87d {-24d 51' 59"}
MOON_DIST:        71.36 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:46:01 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.413d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.515d {-00d 30' 54"} (J2000)
ROLL:            108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59846.38 SOD {16:37:26.38} UT,   872.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     759775081
X_OFFSET:        840 [pixels]
Y_OFFSET:        844 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1000
Y_GRB_POS:       1004
BINNING_INDEX:   1
IM_URL:          sw01285677000msuni0907.fits
SUN_POSTN:       311.45d {+20h 45m 49s}  -18.00d {-17d 59' 54"}
SUN_DIST:         80.04 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.50d {+20h 06m 00s}  -24.84d {-24d 50' 36"}
MOON_DIST:        71.44 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Jan 25 16:46:16 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1285677,   Seg_Num: 0
POINT_RA:        231.413d {+15h 25m 39s} (J2000)
POINT_DEC:        -0.515d {-00d 30' 54"} (J2000)
ROLL:            108.187d
IMG_START_DATE:  20703 TJD;    28 DOY;   25/01/28
IMG_START_TIME:  59846.38 SOD {16:37:26.38} UT,   872.7 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     759775081
X_OFFSET:        840 [pixels]
Y_OFFSET:        844 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1000
Y_GRB_POS:       1004
BINNING_INDEX:   1
IM_URL:          sw01285677000msuni0907.fits
SUN_POSTN:       311.45d {+20h 45m 49s}  -18.00d {-17d 59' 54"}
SUN_DIST:         80.04 [deg]   Sun_angle= 5.3 [hr] (West of Sun)
MOON_POSTN:      301.50d {+20h 06m 01s}  -24.84d {-24d 50' 34"}
MOON_DIST:        71.44 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:        2.60, 43.78 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      229.13, 17.62 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN Circular #39059
L. Izzo (INAF-OACn and DARK/NBI), and D. B. Malesani (DAWN/NBI and Radboud Univ.) report:
We observed the field of the short GRB 250128A (Evans et al., GCN #39058) with the Sinistro instrument mounted on the 1-m telescope of the LCO network, located at Siding Spring, Australia. Observations started on 2025 January 28 at 17:19 UT (0.95 hr after the GRB trigger). We obtained a single image of 300s in the SDSS-r and SDSS-i filters.
We did not detect any source consistent with the position of the X-ray afterglow reported by Swift-XRT (Evans et al., GCN #39058) up to a limit of r = 19.4 mag and z = 18.4 mag.
This project has received funding from the European Union's Horizon 2020 research and innovation program under grant agreement No 101004719.
GCN Circular #39061
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) was pointed to the Swift GRB 250128B ( P. A. Evans et al., GCN 39058) errorbox 8555 sec after notice time and 8574 sec after trigger time at 2025-01-28 18:45:48 UT, with upper limit up to 17.9 mag. The observations began at zenith distance = 83 deg. The sun altitude is -52.9 deg.
The galactic latitude b = 43 deg., longitude l = 3 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2759219
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    8665 |        MASTER-Tunka |   C |   180 | 12.6 |        
   10262 |        MASTER-Tunka |   C |    90 | 13.9 |        
   10400 |        MASTER-Tunka |   C |    45 | 13.1 |        
   10453 |        MASTER-Tunka |   C |    36 | 14.1 |        
   10502 |        MASTER-Tunka |   C |    36 | 14.9 |        
   10550 |        MASTER-Tunka |   C |    30 | 14.8 |        
   10590 |        MASTER-Tunka |   C |    26 | 14.8 |        
   10627 |        MASTER-Tunka |   C |    20 | 17.9 |        
   10660 |        MASTER-Tunka |   C |    20 | 17.9 |        
   10693 |        MASTER-Tunka |   C |    20 | 17.9 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #39062
K. Ulaczyk, D. O'Neill, G. Ramsay, B. P. Gompertz, R. Starling, M. Kennedy, K. Ackley, M. J. Dyer, J. Lyman, A. Kumar, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:
The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) covered the field of Fermi and Swift triggered GRB 250128B (GCN 39057, 39058) at 2025-01-28 17:36:35 UT (+1.23h post-trigger). The observation was taken by GOTO-South, and consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues.
We do not identify any candidate optical counterparts within the Swift XRT localisation uncertainty region, down to a 3-sigma limiting magnitude of L > 20.4 AB mag, consistent with the non-detections reported by Izzo et al. (GCN 39059) and Lipunov et al. (GCN 39061).
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
GCN Circular #39063
A. Myers (NPP/GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 16:22:53.77 UT on 28 January 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250128B (trigger 759774178/250128683). which was also detected by Swift BAT (P.A Evans et al. 2025, GCN [39058](https://gcn.nasa.gov/circulars/39058)). The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 86 degrees.
The GBM light curve consists of a short single emission episode with a duration (T90) of about 1.1 s (50-300 keV). The time-averaged spectrum from T0-0.8 to T0+0.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.0 +/- 0.5 and the cutoff energy, parameterized as Epeak, is 176 +/- 115 keV. A power law function with index -1.6 +/- 0.2 fits the spectrum equally well.
The event fluence (10-1000 keV) in this time interval is (2.1 +/- 0.7)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.064 s in the 10-1000 keV band is 9 +/- 2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #39064
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), M. A. Williams (PSU), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 7.0 ks of XRT data for GRB 250128B, from 87 s to 33.6 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode. The best available XRT position (using the promptly downlinked event data, the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue) is RA, Dec = 231.42552, -0.53950 which is equivalent to:
```
RA (J2000): 15 25 42.12
Dec(J2000): -00 32 22.2
```
with an uncertainty of 1.9 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay index of alpha=1.17 (+0.16, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+0.7, -0.6). The best-fitting absorption column is 1.9 (+2.9, -1.1) x 10^21 cm^-2, consistent with the Galactic value of 8.0 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.7 x 10^-11 (5.1 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.9 (+2.9, -1.1) x 10^21 cm^-2
Galactic foreground: 8.0 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     2.0 (+0.7, -0.6)
```
If the light curve continues to decay with a power-law decay index of 1.17, the count rate at T+24 hours will be 1.5 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.7 x 10^-15 (7.6 x 10^-15) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01285677.
This circular is an official product of the Swift-XRT team.

GCN Circular #39067
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250128B ( Fermi GBM team, GCN 39057) errorbox 26118 sec after notice time and 26157 sec after trigger time at 2025-01-28 23:38:50 UT, with upper limit up to 18.7 mag. The observations began at zenith distance = 76 deg. The sun altitude is -38.7 deg.
The galactic latitude b = -9 deg., longitude l = 344 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2759250
We obtain a following upper limits.

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   26187 | 2025-01-28 23:38:50 |         MASTER-SAAO | (16h 54m 01.94s , -51d 54m 03.8s) |   C |    60 | 14.5 |        
   26645 | 2025-01-28 23:46:28 |         MASTER-SAAO | (17h 07m 34.90s , -48d 08m 01.7s) |   C |    60 | 13.5 |        
   30371 | 2025-01-29 00:48:34 |         MASTER-SAAO | (16h 55m 30.58s , -48d 08m 09.4s) |   C |    60 | 12.1 |        
   30450 | 2025-01-29 00:49:53 |         MASTER-SAAO | (17h 07m 31.89s , -48d 07m 22.2s) |   C |    60 | 12.6 |        
   30529 | 2025-01-29 00:51:13 |         MASTER-SAAO | (17h 25m 40.30s , -46d 15m 46.5s) |   C |    60 | 15.9 |        
   30609 | 2025-01-29 00:52:32 |         MASTER-SAAO | (17h 37m 21.80s , -46d 15m 49.3s) |   C |    60 | 15.1 |        
   31804 | 2025-01-29 01:12:28 |         MASTER-SAAO | (16h 53m 49.95s , -51d 55m 37.6s) |   C |    60 | 15.4 |        
   31884 | 2025-01-29 01:13:47 |         MASTER-SAAO | (16h 55m 31.05s , -48d 09m 30.8s) |   C |    60 | 17.2 |        
   31963 | 2025-01-29 01:15:06 |         MASTER-SAAO | (17h 07m 34.80s , -48d 08m 03.8s) |   C |    60 | 17.0 |        
   32243 | 2025-01-29 01:19:46 |         MASTER-SAAO | (17h 25m 37.93s , -46d 14m 13.1s) |   C |    60 | 14.9 |        
   32322 | 2025-01-29 01:21:05 |         MASTER-SAAO | (17h 37m 19.22s , -46d 15m 27.6s) |   C |    60 | 14.3 |        
   32481 | 2025-01-29 01:23:44 |         MASTER-SAAO | (16h 53m 52.00s , -51d 57m 29.7s) |   C |    60 | 16.1 |        
   32560 | 2025-01-29 01:25:03 |         MASTER-SAAO | (16h 55m 30.06s , -48d 08m 10.8s) |   C |    60 | 17.9 |        
   32639 | 2025-01-29 01:26:22 |         MASTER-SAAO | (17h 07m 30.76s , -48d 09m 30.5s) |   C |    60 | 17.6 |        
   32718 | 2025-01-29 01:27:42 |         MASTER-SAAO | (17h 18m 16.31s , -48d 09m 14.3s) |   C |    60 | 17.3 |        
   32798 | 2025-01-29 01:29:01 |         MASTER-SAAO | (17h 30m 18.33s , -48d 08m 28.5s) |   C |    60 | 17.3 |        
   32877 | 2025-01-29 01:30:21 |         MASTER-SAAO | (17h 25m 43.58s , -46d 15m 26.3s) |   C |    60 | 17.5 |        
   32957 | 2025-01-29 01:31:40 |         MASTER-SAAO | (17h 37m 12.35s , -46d 16m 40.3s) |   C |    60 | 17.0 |        
   33115 | 2025-01-29 01:34:19 |         MASTER-SAAO | (16h 53m 47.39s , -51d 55m 49.0s) |   C |    60 | 16.3 |        
   33195 | 2025-01-29 01:35:38 |         MASTER-SAAO | (16h 55m 28.67s , -48d 09m 42.8s) |   C |    60 | 17.3 |        
   33475 | 2025-01-29 01:40:18 |         MASTER-SAAO | (17h 07m 26.19s , -48d 09m 10.5s) |   C |    60 | 17.6 |        
   33554 | 2025-01-29 01:41:37 |         MASTER-SAAO | (17h 18m 15.01s , -48d 08m 25.7s) |   C |    60 | 16.8 |        
   33633 | 2025-01-29 01:42:57 |         MASTER-SAAO | (17h 30m 20.98s , -48d 09m 41.3s) |   C |    60 | 16.5 |        
   33713 | 2025-01-29 01:44:16 |         MASTER-SAAO | (17h 25m 36.21s , -46d 16m 39.3s) |   C |    60 | 17.3 |        
   33792 | 2025-01-29 01:45:35 |         MASTER-SAAO | (17h 37m 17.42s , -46d 16m 36.8s) |   C |    60 | 17.0 |        
   33872 | 2025-01-29 01:46:55 |         MASTER-SAAO | (16h 55m 27.37s , -48d 08m 29.5s) |   C |    60 | 16.3 |        
   33951 | 2025-01-29 01:48:15 |         MASTER-SAAO | (17h 33m 38.21s , -44d 21m 23.3s) |   C |    60 | 15.5 |        
   34031 | 2025-01-29 01:49:34 |         MASTER-SAAO | (17h 44m 46.86s , -44d 22m 07.8s) |   C |    60 | 15.1 |        
   34110 | 2025-01-29 01:50:53 |         MASTER-SAAO | (17h 07m 25.08s , -48d 08m 18.6s) |   C |    60 | 17.1 |        
   34189 | 2025-01-29 01:52:12 |         MASTER-SAAO | (17h 18m 19.31s , -48d 09m 34.6s) |   C |    60 | 17.0 |        
   34268 | 2025-01-29 01:53:32 |         MASTER-SAAO | (17h 30m 15.48s , -48d 10m 51.3s) |   C |    60 | 17.4 |        
   34348 | 2025-01-29 01:54:51 |         MASTER-SAAO | (17h 25m 39.83s , -46d 16m 26.1s) |   C |    60 | 17.5 |        
   34427 | 2025-01-29 01:56:11 |         MASTER-SAAO | (17h 37m 12.76s , -46d 15m 22.7s) |   C |    60 | 17.1 |        
   34706 | 2025-01-29 02:00:49 |         MASTER-SAAO | (17h 33m 37.71s , -44d 21m 26.5s) |   C |    60 | 17.1 |        
   34787 | 2025-01-29 02:02:10 |         MASTER-SAAO | (17h 44m 44.57s , -44d 22m 19.1s) |   C |    60 | 17.0 |        
   34866 | 2025-01-29 02:03:30 |         MASTER-SAAO | (17h 18m 13.41s , -48d 08m 42.4s) |   C |    60 | 15.6 |        
   34946 | 2025-01-29 02:04:49 |         MASTER-SAAO | (17h 30m 18.40s , -48d 10m 00.7s) |   C |    60 | 16.2 |        
   35025 | 2025-01-29 02:06:08 |         MASTER-SAAO | (17h 25m 33.37s , -46d 16m 57.8s) |   C |    60 | 17.2 |        
   35104 | 2025-01-29 02:07:27 |         MASTER-SAAO | (17h 37m 14.58s , -46d 16m 48.0s) |   C |    60 | 16.9 |        
   35184 | 2025-01-29 02:08:47 |         MASTER-SAAO | (17h 41m 05.26s , -48d 11m 14.0s) |   C |    60 | 17.1 |        
   35263 | 2025-01-29 02:10:06 |         MASTER-SAAO | (17h 53m 10.47s , -48d 09m 56.4s) |   C |    60 | 17.0 |        
   35343 | 2025-01-29 02:11:26 |         MASTER-SAAO | (17h 33m 31.26s , -44d 22m 13.5s) |   C |    60 | 17.2 |        
   35422 | 2025-01-29 02:12:45 |         MASTER-SAAO | (17h 44m 44.37s , -44d 21m 30.1s) |   C |    60 | 16.9 |        
   35501 | 2025-01-29 02:14:04 |         MASTER-SAAO | (17h 18m 16.78s , -48d 09m 51.5s) |   C |    60 | 16.8 |        
   35581 | 2025-01-29 02:15:24 |         MASTER-SAAO | (17h 30m 12.42s , -48d 11m 09.5s) |   C |    60 | 17.3 |        
   35660 | 2025-01-29 02:16:43 |         MASTER-SAAO | (17h 12m 14.68s , -44d 21m 08.1s) |   C |    60 | 16.9 |        
   35938 | 2025-01-29 02:21:21 |         MASTER-SAAO | (17h 23m 30.01s , -44d 21m 27.4s) |   C |    60 | 16.5 |        
   36018 | 2025-01-29 02:22:41 |         MASTER-SAAO | (17h 41m 00.34s , -48d 10m 28.6s) |   C |    60 | 15.7 |        
   36097 | 2025-01-29 02:24:00 |         MASTER-SAAO | (17h 53m 01.26s , -48d 09m 45.3s) |   C |    60 | 16.1 |        
   36176 | 2025-01-29 02:25:19 |         MASTER-SAAO | (17h 33m 35.46s , -44d 22m 23.6s) |   C |    60 | 16.2 |        
   36255 | 2025-01-29 02:26:39 |         MASTER-SAAO | (17h 44m 41.67s , -44d 23m 40.6s) |   C |    60 | 16.2 |        
   36335 | 2025-01-29 02:27:58 |         MASTER-SAAO | (17h 18m 14.66s , -48d 10m 39.3s) |   C |    60 | 17.4 |        
   36414 | 2025-01-29 02:29:17 |         MASTER-SAAO | (17h 30m 13.31s , -48d 09m 35.0s) |   C |    60 | 17.2 |        
   36494 | 2025-01-29 02:30:37 |         MASTER-SAAO | (17h 12m 12.99s , -44d 22m 28.4s) |   C |    60 | 18.7 |        
   36573 | 2025-01-29 02:31:56 |         MASTER-SAAO | (17h 23m 29.31s , -44d 21m 35.4s) |   C |    60 | 17.9 |        
   36652 | 2025-01-29 02:33:16 |         MASTER-SAAO | (17h 40m 59.51s , -48d 10m 37.4s) |   C |    60 | 17.5 |        
   36732 | 2025-01-29 02:34:35 |         MASTER-SAAO | (17h 53m 00.41s , -48d 09m 54.9s) |   C |    60 | 17.6 |        
   36890 | 2025-01-29 02:37:14 |         MASTER-SAAO | (17h 44m 40.86s , -44d 23m 49.2s) |   C |    60 | 16.7 |        
   37169 | 2025-01-29 02:41:52 |         MASTER-SAAO | (17h 12m 11.39s , -44d 21m 00.5s) |   C |    60 | 17.1 |        
   37248 | 2025-01-29 02:43:11 |         MASTER-SAAO | (17h 23m 24.33s , -44d 22m 58.5s) |   C |    60 | 17.3 |        
   37327 | 2025-01-29 02:44:31 |         MASTER-SAAO | (17h 41m 03.16s , -48d 09m 53.2s) |   C |    60 | 17.1 |        
   37407 | 2025-01-29 02:45:50 |         MASTER-SAAO | (17h 52m 57.89s , -48d 11m 03.2s) |   C |    60 | 16.6 |        
   37486 | 2025-01-29 02:47:09 |         MASTER-SAAO | (17h 33m 26.22s , -44d 21m 38.3s) |   C |    60 | 14.9 |        
   37566 | 2025-01-29 02:48:29 |         MASTER-SAAO | (17h 44m 44.73s , -44d 22m 56.9s) |   C |    60 | 12.7 |        
   37645 | 2025-01-29 02:49:48 |         MASTER-SAAO | (17h 47m 35.43s , -46d 17m 56.8s) |   C |    60 | 15.6 |        
   37724 | 2025-01-29 02:51:07 |         MASTER-SAAO | (17h 59m 08.69s , -46d 16m 32.3s) |   C |    60 | 15.7 |        
   37803 | 2025-01-29 02:52:27 |         MASTER-SAAO | (17h 12m 10.07s , -44d 22m 55.3s) |   C |    60 | 13.4 |        
   37883 | 2025-01-29 02:53:46 |         MASTER-SAAO | (17h 23m 26.84s , -44d 21m 42.8s) |   C |    60 | 15.3 |        
   37962 | 2025-01-29 02:55:05 |         MASTER-SAAO | (17h 40m 56.50s , -48d 10m 51.8s) |   C |    60 | 15.8 |        
   38041 | 2025-01-29 02:56:24 |         MASTER-SAAO | (17h 52m 58.20s , -48d 10m 11.0s) |   C |    60 | 15.3 |        
   38120 | 2025-01-29 02:57:43 |         MASTER-SAAO | (17h 35m 05.33s , -50d 05m 41.0s) |   C |    60 | 14.7 |        
   38425 | 2025-01-29 03:02:48 |         MASTER-SAAO | (17h 47m 37.45s , -50d 04m 32.0s) |   C |    60 | 15.0 |        
   38662 | 2025-01-29 03:06:45 |         MASTER-SAAO | (17h 12m 04.50s , -44d 22m 13.1s) |   C |    60 | 16.4 |        
   38742 | 2025-01-29 03:08:05 |         MASTER-SAAO | (17h 23m 18.76s , -44d 21m 34.3s) |   C |    60 | 16.0 |        
   38821 | 2025-01-29 03:09:24 |         MASTER-SAAO | (17h 41m 00.17s , -48d 11m 01.1s) |   C |    60 | 15.7 |

Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.

GCN Circular #39069
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1514 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250128B, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 231.42540, -0.53929 which is equivalent to:
```
RA (J2000): 15h 25m 42.10s
Dec (J2000): -00d 32' 21.4"
```
with an uncertainty of 2.7 arcsec (radius, 90% confidence).
This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular was automatically generated, and is an official product of the Swift-XRT team.
GCN Circular #39076
C. Adami (LAM/Pytheas/AMU), B. Schneider (LAM), S. Basa (LAM/OHP/Pytheas/AMU), E. Le Floc'h (CEA/Irfu), A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), F. Schussler (CEA Paris-Saclay), M. Dennefeld (IAP), J. Palmerio (CEA/Irfu) report on behalf of a larger collaboration:
We observed the field of the GRB250128B (Fermi GBM team, GCN 39057; Evans et al., GCN 39058; Izzo et al., GCN 39059; Lipunow et al., GCN 39061; Ulaczyk et al., GCN 39062; Muers et al., GCN 39063; Osborne et al., GCN 39064; Lipunov et al., GCN 39067; Evans et al., GCN 39069) with the T193cm telescope at the Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained a total of 2490sec (1x30s + 1x300s + 3x720s) in the i-band using the red MISTRAL setting from 20250129_043822UT to 20250129_050703UT (mid-time ~12.5h after the trigger).
In the stacked image, we do not detect any new source at the XRT source position (Evans et al., GCN 39069) down to the following 3-sigma limit:
i > 20.6
The photometric calibration was performed using nearby stars from the PanSTARRS catalog. We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean Balcaen, and the Sophie observer Alice Radcliffe
GCN Circular #39080
Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome), Simone Dichiara (PSU), Eleonora Troja (U Rome) and Roberto Ricci (U Rome) report:
We observed the field of GRB 250128B (Evans et al., GCN 39058, Myers et al., GCN 39063) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began 0.67 days after the trigger and were carried out in the R filter at an average seeing of 1.1".
We do not detect any new source at the XRT source position (Evans et al., GCN 39069) down to the following 3-sigma limit R>24.8 AB mag calibrated using nearby stars in the PanSTARRS PS1 DR2 catalogue.
In our image we identify a few extended objects close to the XRT localization, however their probability of chance coincidence is Pcc>20 %.
We thank the staff at the VLT, especially Steffen Mieske, for the rapid execution of these observations.
GCN Circular #39081
K. E. Heintz (DAWN/NBI), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. de Ugarte Postigo (CNRS, OCA and LAM), Benjamin N. Hauptmann (NOT, DTU Space), Arthur M. Kadela (NOT, NBI), report on behalf of a larger collaboration:
We observed the field of the short Fermi and Swift GRB 250128B (Fermi GBM team, GCN 39057; Evans et al., GCN 39058) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Three exposures by 300 s each were secured in the r band, with a mean epoch 2025 Jan 29.2095 UT (12.65 hr after the trigger). The sequence was interrupted in order to observe GRB 250129A (Izzo et al., GCN 39073).
No source is detected within or close to the UVOT-enhanced XRT position (Evans et al., GCN 39069), down to a 3-sigma limiting AB magnitude r > 23.45, calibrated against nearby stars from the Pan-STARRS catalog.
GCN Circular #39084
Yu-Han Yang (U Rome), Muskan Yadav (U Rome), Rosa L. Becerra (U Rome), Simone Dichiara (PSU), Eleonora Troja (U Rome) and Roberto Ricci (U Rome) report:
We observed the field of GRB 250128B (Evans et al., GCN 39058, Myers et al., GCN 39063) with the HAWKI imager on the ESO VLT UT4 (Yepun). Observations began 0.68 days after the trigger and were carried out in the J filter at an average seeing of 1.3".
Based on a preliminary analysis, we do not detect any new source within the XRT afterglow position (Evans et al., GCN 39069) down to J > 24 AB mag (3 sigma), calibrated using nearby stars in the 2MASS catalogue. A low-significance (~2 sigma) source is identified at RA, Dec (J2000) = 15:25:42.11, -0.32:21.21. Further observations to determine the significance and possible variability of this source are planned.
We thank the staff at the VLT, for the rapid execution of these observations.
GCN Circular #39086
A. Rossi (INAF-OAS), R. Brivio, M. Ferro, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB), L. Di Fabrizio, G. Mainella (INAF-TNG) report on behalf of the CIBO collaboration:
We observed the field of the short GRB 250128B detected by Fermi and Swift (Fermi GBM team, GCN 39057; Evans et al., GCN 39058) with the Italian 3.6m TNG telescope equipped with the optical camera DOLORES. A series of images were obtained with the i-sdss filter on 2025-01-29 at a mid-time of about 13.5 hours after the burst.
No clear afterglow candidate is detected within the UVOT-enhanced XRT position (Evans et al., GCN 39069) down to a 3-sigma limiting magnitude of i ~ 25.3 (AB; calibrated against the Pan-STARRS catalogue).
GCN Circular #39088
Jillian Rastinejad, Wen-fai Fong (Northwestern), Genevieve Schroeder (Cornell), Harsh Kumar (CfA), Benjamin Gompertz (Birmingham) and Andrew Levan (Radboud) report on behalf of a larger collaboration:
We observed the location of the X-ray counterpart of the short GRB 250128B (Evans et al., GCN 39058) with the Gemini Multi-Object Spectrograph (GMOS) mounted on Gemini-North under Program GN-2024B-Q-111 (PI: Fong). We obtained 13x120-sec imaging in r-band at a mid-time of 2025-01-29 14:43:45.0 UT (0.93 days post-burst), at a median airmass of 1.3 and seeing of 1’’.
Within the enhanced XRT localization (Evans et al., GCN 39069), we detect a faint extended source, or possibly a blend of two unrelated sources. This source complex is centered at R.A. = 15:25:42.07, Decl. = -00:32:20.3 (J2000) with an approximate visual angular size of 2”, and is consistent with the position of the candidate near-IR source reported by Yang et al., GCN 39084. Both positions are consistent with the enhanced XRT localization (Evans et al., GCN 39069). Calibrated to SDSS, we measure a preliminary brightness for this source complex of r = 25.4 +/- 0.2 AB mag, not corrected for Galactic extinction. We do not detect any other sources within or adjacent to the XRT localization to a 3-sigma limiting magnitude of r > 25.8 AB mag. At this stage, we cannot make any determination if there is any contribution to the observed light from an afterglow component.
Further observations are planned to monitor the variability of the source. We thank Jennifer Andrews and additional Gemini staff for the rapid planning and execution of these observations.
GCN Circular #39093
Roberto Ricci (U Rome), Muskan Yadav (U Rome), Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome) and Eleonora Troja (U Rome) report:
We observed the field of the short GRB 250128B discovered by Fermi/GBM (Fermi GMB team, GCN 39057) and Swift/BAT (Evans et al. GCN 39058) with the Very Large Array at the centre frequency of 6 GHz (C band) with a bandwidth 4 GHz. The observations started on 2025-01-29 at 12:48 UT and lasted for 47 mins, resulting in a mid elapsed time of 20.8 hours after trigger. The primary calibrator was 3C286 and the phase calibrator J1546+0026.
Within the enhanced Swift/XRT position (Evans et al., GCN 39069) no counterpart is found down to a 3-sigma upper limit of 15 microJy. Additional follow-up is planned.
We thank the VLA staff for promptly observing the target.
GCN Circular #39094
A. S. Moskvitin (SAO RAS), N. Pankov (HSE, IKI), O. Spiridonova (SAO RAS), V. Rumyantsev (CrAO), A. Volnova (IKI), A. Pozanenko (IKI) report on behalf of the collaboration between IKI-GRB-FuN and the GRB follow-up team.
We observed the field of GRB 250128B (Fermi GBM team, GCN 39057; Evans et al., GCN 39058; Myers and Meegan, GCN 39063; Osborne et al., GCN 39064) with the 1-meter Zeiss-1000 telescope at the Special Astrophysical Observatory (SAO RAS) and the 2.6-meter Shajn telescope (ZTSh) at Crimean Astrophysical Observatory (CrAO). The observations began on 2025-01-29 00:57:27 at the SAO RAS, i.e. ~0.38 days since the burst. We obtained 12 x 300 sec images in the Rc-filter with Zeiss-1000 and 44 x 120 sec images in the R-filter with ZTSh. The stacked images from both telescopes have not revealed any new optical source located within the enhanced XRT circle (Evans et al., GCN 39069). The preliminary upper limits are as follows:
```
Date       UT start  t-T0         Exp.    Filter  UL(3sigma) Telescope
                     (mid, days)  (s)
2025-01-29 00:57:27  0.38090      12*300  Rc      23.5       Zeiss-1000
2025-01-29 01:33:22  0.41284      44*120  R       23.1       ZTSh
```
The photometry is based on nearby stars of the USNO-B1.0 catalog (R2 magnitudes) and have not been corrected for the Galactic extinction. Our results are consistent with the upper limits obtained by other teams (Izzo & Malesani, GCN 39059; Lipunov et al., GCN 39061; GCN 39067; Ulaczyk et al., GCN 39062; Adami et al., GCN 39076; Becerra et al., GCN 39080; Heintz et al., GCN 39081; Yang et. al, GCN 39084; Rossi et. al, GCN 39086).
GCN Circular #39103
G. Schroeder (Cornell), T. Laskar (Utah), W. Fong, J. Rastinejad (Northwestern) report:
We observed the position of the short GRB 250128B (Evans et al., GCN 39058; Fermi GBM team, GCN 39057) with the Karl G. Jansky Very Large Array (VLA) under program 25A-063 (PI: Schroeder) beginning on 2025 Jan 29 at 10:05 UT (0.74 days post-burst) for 0.75 hours at a mean frequency of 6 GHz.
Based on preliminary analysis, within the enhanced XRT position (Evans et al., GCN 39069) we find a possible source with a peak flux density of ~20 uJy at the position:
```
RA(J2000): 15:25:42.032
Dec(J2000): -00:32:22.72
```
with an uncertainty of 0.1 arcsec in each coordinate. This position is ~2 arcsec offset from the optical/near IR sources reported in Yang et al. (GCN 39084) and Rastinejad et al. (GCN 39088). At present we cannot determine if this possible source is associated with the burst. We note that these observations were taken 2.7 hr prior to those reported in Ricci et al. (GCN 39093).
We thank the VLA staff for quickly approving and executing these observations. Further observations are planned to assess the temporal behavior of the possible source.

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Jochen Greiner, last update: 31-Jan-2025 [Disclaimer]