Gamma-ray Burst 251005C

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:07:18 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1401726,   Seg_Num: 0
GRB_RA:           75.673d {+05h 02m 42s} (J2000),
                  76.046d {+05h 04m 11s} (current),
                  74.951d {+04h 59m 48s} (1950)
GRB_DEC:         +16.882d {+16d 52' 54"} (J2000),
                 +16.917d {+16d 55' 00"} (current),
                 +16.811d {+16d 48' 40"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       4374 [cnts]    Image_Peak=338 [image_cnts]
TRIGGER_DUR:     1.408 [sec] 
TRIGGER_INDEX:   485     E_range: 50-350 keV
BKG_INTEN:       26767 [cnts]
BKG_TIME:        57987.54 SOD {16:06:27.54} UT
BKG_DUR:         16 [sec]
GRB_DATE:        20953 TJD;   278 DOY;   25/10/05
GRB_TIME:        58013.91 SOD {16:06:53.91} UT
GRB_PHI:          -3.88 [deg]
GRB_THETA:        31.44 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     35.77 [sigma]
IMAGE_SIGNIF:    13.73 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +3  +3  +0  +0 +44  +0 
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.00d {-05d 00' 15"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.68d {+23h 30m 44s}   -2.76d {-02d 45' 26"}
MOON_DIST:        84.46 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       76.23, -5.88 [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 = 152.37,20.35 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=781373219).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:07:23 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     781373219
GRB_RA:          129.517d {+08h 38m 04s} (J2000),
                 129.990d {+08h 39m 58s} (current),
                 128.594d {+08h 34m 23s} (1950)
GRB_DEC:         +52.450d {+52d 27' 00"} (J2000),
                 +52.358d {+52d 21' 30"} (current),
                 +52.625d {+52d 37' 32"} (1950)
GRB_ERROR:       9.60 [deg radius, statistical plus systematic]
GRB_INTEN:       413 [cnts/sec]
DATA_SIGNIF:     9.10 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20953 TJD;   278 DOY;   25/10/05
GRB_TIME:        58014.00 SOD {16:06:54.00} UT
GRB_PHI:         100.00 [deg]
GRB_THETA:       150.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.26
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      62%  Distant Particles
2nd_MOST_LIKELY:  36%  GRB
DETECTORS:       0,0,0, 0,0,0, 0,0,0, 1,0,1, 0,0,
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.00d {-05d 00' 15"}
SUN_DIST:         77.31 [deg]   Sun_angle= 4.1 [hr] (West of Sun)
MOON_POSTN:      352.68d {+23h 30m 44s}   -2.76d {-02d 45' 25"}
MOON_DIST:       119.11 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      166.09, 37.22 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      117.44, 32.71 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251005671/quicklook/glg_lc_medres34_bn251005671.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 139.53,-19.37 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1401726).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 05 Oct 25 17:50:07 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     781373219
GRB_RA:           72.840d {+04h 51m 22s} (J2000),
                  73.210d {+04h 52m 51s} (current),
                  72.122d {+04h 48m 29s} (1950)
GRB_DEC:         +16.380d {+16d 22' 48"} (J2000),
                 +16.422d {+16d 25' 19"} (current),
                 +16.296d {+16d 17' 46"} (1950)
GRB_ERROR:       5.63 [deg radius, statistical only]
GRB_DATE:        20953 TJD;   278 DOY;   25/10/05
GRB_TIME:        58014.00 SOD {16:06:54.00} UT
GRB_PHI:         124.01 [deg]
GRB_THETA:        96.01 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:       191.72d {+12h 46m 53s}   -5.03d {-05d 01' 54"}
SUN_DIST:        118.74 [deg]   Sun_angle= 7.9 [hr] (West of Sun)
MOON_POSTN:      353.59d {+23h 34m 23s}   -2.27d {-02d 16' 01"}
MOON_DIST:        80.70 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      183.44,-17.37 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       73.46, -6.08 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251005671/quicklook/glg_lc_medres34_bn251005671.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251005671/quicklook/glg_locplot_all_bn251005671.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 has human-in-the-loop processing.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1401726).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:10:59 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1401726,   Seg_Num: 0
GRB_RA:           75.673d {+05h 02m 42s} (J2000),
                  76.046d {+05h 04m 11s} (current),
                  74.951d {+04h 59m 48s} (1950)
GRB_DEC:         +16.882d {+16d 52' 54"} (J2000),
                 +16.917d {+16d 55' 00"} (current),
                 +16.811d {+16d 48' 40"} (1950)
GRB_DATE:        20953 TJD;   278 DOY;   25/10/05
GRB_TIME:        58013.91 SOD {16:06:53.91} UT
TRIGGER_INDEX:   485
GRB_PHI:          -3.88 [deg]
GRB_THETA:        31.44 [deg]
DELTA_TIME:      -76.00 [sec]
TRIGGER_DUR:     1.408 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     35.77 [sigma]
IMAGE_SIGNIF:    13.73 [sigma]
LC_URL:          sw01401726000msb.lc
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.01d {-05d 00' 19"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.72d {+23h 30m 52s}   -2.74d {-02d 44' 23"}
MOON_DIST:        84.43 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       76.23, -5.88 [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 = 152.37,20.35 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:12:01 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.877d {+16d 52' 36"} (J2000)
POINT_ROLL:      87.258d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58136.78 SOD {16:08:56.78} UT,   122.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.056
N_STARS:         62
X_OFFSET:        455 [pixels]
Y_OFFSET:        535 [pixels]
X_MAX:           1414 [pixels]
Y_MAX:           1494 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw01401726000msufc0122.fits
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.01d {-05d 00' 20"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.73d {+23h 30m 54s}   -2.74d {-02d 44' 05"}
MOON_DIST:        84.42 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:12:13 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.877d {+16d 52' 36"} (J2000)
POINT_ROLL:      87.258d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58136.78 SOD {16:08:56.78} UT,   122.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.056
N_STARS:         62
X_OFFSET:        455 [pixels]
Y_OFFSET:        535 [pixels]
X_MAX:           1414 [pixels]
Y_MAX:           1494 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    8
SL_URL:          sw01401726000msufc0122.fits
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.01d {-05d 00' 20"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.73d {+23h 30m 55s}   -2.73d {-02d 44' 02"}
MOON_DIST:        84.42 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:13:25 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.877d {+16d 52' 36"} (J2000)
ROLL:            87.258d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58136.78 SOD {16:08:56.78} UT,   122.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     781373373
X_OFFSET:        774 [pixels]
Y_OFFSET:        854 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       934
Y_GRB_POS:       1014
BINNING_INDEX:   1
IM_URL:          sw01401726000msuni0159.fits
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.01d {-05d 00' 21"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.74d {+23h 30m 57s}   -2.73d {-02d 43' 41"}
MOON_DIST:        84.41 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:13:41 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.877d {+16d 52' 36"} (J2000)
ROLL:            87.258d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58136.78 SOD {16:08:56.78} UT,   122.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     781373373
X_OFFSET:        774 [pixels]
Y_OFFSET:        854 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       934
Y_GRB_POS:       1014
BINNING_INDEX:   1
IM_URL:          sw01401726000msuni0159.fits
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.01d {-05d 00' 21"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.74d {+23h 30m 58s}   -2.73d {-02d 43' 37"}
MOON_DIST:        84.40 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:12:56 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1401726,   Seg_Num: 0
GRB_RA:           75.6829d {+05h 02m 43.89s} (J2000),
                  76.0552d {+05h 04m 13.25s} (current),
                  74.9608d {+04h 59m 50.60s} (1950)
GRB_DEC:         +16.8805d {+16d 52' 49.8"} (J2000),
                 +16.9155d {+16d 54' 55.8"} (current),
                 +16.8100d {+16d 48' 35.8"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58142.00 SOD {16:09:02.00} UT,   128.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       191.66d {+12h 46m 38s}   -5.01d {-05d 00' 21"}
SUN_DIST:        115.93 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.73d {+23h 30m 56s}   -2.73d {-02d 43' 50"}
MOON_DIST:        84.42 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.67,-14.87 [deg] galactic lon,lat of the burst
ECL_COORDS:       76.24, -5.88 [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 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:20:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 40"} (J2000)
POINT_ROLL:      87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58349.86 SOD {16:12:29.86} UT,   335.9 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.876
N_STARS:         90
X_OFFSET:        215 [pixels]
Y_OFFSET:        295 [pixels]
X_MAX:           1654 [pixels]
Y_MAX:           1734 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01401726000msufc0335.fits
SUN_POSTN:       191.66d {+12h 46m 40s}   -5.01d {-05d 00' 28"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.80d {+23h 31m 12s}   -2.69d {-02d 41' 37"}
MOON_DIST:        84.33 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:21:57 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 40"} (J2000)
ROLL:            87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58349.86 SOD {16:12:29.86} UT,   335.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     781373586
X_OFFSET:        774 [pixels]
Y_OFFSET:        854 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       934
Y_GRB_POS:       1014
BINNING_INDEX:   1
IM_URL:          sw01401726000msuni0372.fits
SUN_POSTN:       191.67d {+12h 46m 40s}   -5.01d {-05d 00' 29"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.81d {+23h 31m 15s}   -2.69d {-02d 41' 15"}
MOON_DIST:        84.32 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:21:00 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1401726,   Seg_Num: 0
GRB_RA:           75.6834d {+05h 02m 44.01s} (J2000),
                  76.0557d {+05h 04m 13.37s} (current),
                  74.9613d {+04h 59m 50.72s} (1950)
GRB_DEC:         +16.8801d {+16d 52' 48.3"} (J2000),
                 +16.9151d {+16d 54' 54.4"} (current),
                 +16.8096d {+16d 48' 34.4"} (1950)
GRB_ERROR:       2.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58142.00 SOD {16:09:02.00} UT,   128.1 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       191.66d {+12h 46m 40s}   -5.01d {-05d 00' 28"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.80d {+23h 31m 13s}   -2.69d {-02d 41' 31"}
MOON_DIST:        84.34 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.67,-14.87 [deg] galactic lon,lat of the burst
ECL_COORDS:       76.24, -5.88 [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 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:22:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 40"} (J2000)
ROLL:            87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58349.86 SOD {16:12:29.86} UT,   335.9 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     781373586
X_OFFSET:        774 [pixels]
Y_OFFSET:        854 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       934
Y_GRB_POS:       1014
BINNING_INDEX:   1
IM_URL:          sw01401726000msuni0372.fits
SUN_POSTN:       191.67d {+12h 46m 40s}   -5.01d {-05d 00' 29"}
SUN_DIST:        115.94 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.81d {+23h 31m 16s}   -2.69d {-02d 41' 12"}
MOON_DIST:        84.32 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:27:56 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 41"} (J2000)
POINT_ROLL:      87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58879.97 SOD {16:21:19.97} UT,   866.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.185
N_STARS:         161
X_OFFSET:        215 [pixels]
Y_OFFSET:        295 [pixels]
X_MAX:           1654 [pixels]
Y_MAX:           1734 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01401726000msufc0866.fits
SUN_POSTN:       191.67d {+12h 46m 41s}   -5.01d {-05d 00' 35"}
SUN_DIST:        115.95 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.87d {+23h 31m 28s}   -2.66d {-02d 39' 32"}
MOON_DIST:        84.26 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 05 Oct 25 16:28:10 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 41"} (J2000)
POINT_ROLL:      87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58879.97 SOD {16:21:19.97} UT,   866.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.185
N_STARS:         161
X_OFFSET:        215 [pixels]
Y_OFFSET:        295 [pixels]
X_MAX:           1654 [pixels]
Y_MAX:           1734 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01401726000msufc0866.fits
SUN_POSTN:       191.67d {+12h 46m 41s}   -5.01d {-05d 00' 35"}
SUN_DIST:        115.95 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.87d {+23h 31m 28s}   -2.66d {-02d 39' 28"}
MOON_DIST:        84.26 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:29:41 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 41"} (J2000)
ROLL:            87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58879.97 SOD {16:21:19.97} UT,   866.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     781374116
X_OFFSET:        774 [pixels]
Y_OFFSET:        854 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       934
Y_GRB_POS:       1014
BINNING_INDEX:   1
IM_URL:          sw01401726000msuni0903.fits
SUN_POSTN:       191.67d {+12h 46m 41s}   -5.01d {-05d 00' 37"}
SUN_DIST:        115.95 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.88d {+23h 31m 32s}   -2.65d {-02d 39' 02"}
MOON_DIST:        84.24 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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:     Sun 05 Oct 25 16:29:49 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1401726,   Seg_Num: 0
POINT_RA:         75.675d {+05h 02m 42s} (J2000)
POINT_DEC:       +16.878d {+16d 52' 41"} (J2000)
ROLL:            87.256d
IMG_START_DATE:  20953 TJD;   278 DOY;   25/10/05
IMG_START_TIME:  58879.97 SOD {16:21:19.97} UT,   866.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     781374116
X_OFFSET:        774 [pixels]
Y_OFFSET:        854 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       934
Y_GRB_POS:       1014
BINNING_INDEX:   1
IM_URL:          sw01401726000msuni0903.fits
SUN_POSTN:       191.67d {+12h 46m 41s}   -5.01d {-05d 00' 37"}
SUN_DIST:        115.95 [deg]   Sun_angle= 7.7 [hr] (West of Sun)
MOON_POSTN:      352.88d {+23h 31m 32s}   -2.65d {-02d 39' 00"}
MOON_DIST:        84.24 [deg]
MOON_ILLUM:      97 [%]
GAL_COORDS:      184.66,-14.87 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       76.23, -5.88 [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 #42113
K. L. Page (U Leicester), S. Dichiara (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), N. P. M. Kuin (UCL-MSSL) and M. J. Moss (GSFC) report on behalf of the Neil Gehrels Swift Observatory Team:
At 16:06:53 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 251005C (trigger=1401726). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 75.673, +16.882 which is
```
   RA(J2000) = 05h 02m 42s
   Dec(J2000) = +16d 52' 54"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a double-peaked structure with a duration of about 2 sec. The peak count rate was ~4,500 counts/sec (15-350 keV), at ~1 sec after the trigger.
The XRT began observing the field at 16:08:52.2 UT, 118.3 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 75.68331, 16.88007 which is equivalent to:
```
   RA(J2000)  = 05h 02m 44.00s
   Dec(J2000) = +16d 52' 48.3"
```
with an uncertainty of 2.1 arcseconds (radius, 90% containment). This location is 36 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.
A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (3.19 x 10^21 cm^-2, Willingale et al. 2013), with an excess column of 5 (+3.76/-3.16) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 122 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 0.461.
Burst Advocate for this burst is K. L. Page (klp5 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 Circular #42115
B. P. Gompertz, D. O’Neill, G. Ramsay, P. O’Brien, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, A. Kumar, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to Swift/BAT trigger 1401726. The current difficulties with the distribution of GCN circulars means we are unsure of the official designation of this burst at the time of submission.
A targeted observation was performed at 17:48:32 (1.7 hours after trigger), consisting 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.
We find no new optical sources consistent with the Swift/XRT localisation to a 3-sigma limiting AB magnitude of L > 19.65 mag.
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 #42116
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 1541 s of XRT Photon Counting mode data and 2 UVOT images for GRB 251005C, 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 = 75.68325, +16.88054 which is equivalent to:
```
RA (J2000): 05h 02m 43.98s
Dec (J2000): +16d 52' 49.9"
```
with an uncertainty of 2.3 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 #42118
Jacob Smith (UAH), B. Mailyan (Florida Tech) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 16:06:54.00 UT on 05 October 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251005C (trigger 781373219/251005671), which was also detected by Swift BAT (K. L. Page et al. 2025, GCN 42113). The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 98 degrees.
The GBM light curve consists of a double emission episode with a duration (T90) of about 6 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+5.248 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.9 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 2136 +/- 866 keV.
The event fluence (10-1000 keV) in this time interval is (3.2 +/- 0.2)E-06 erg/cm^2. The 64-millisec peak photon flux measured starting from T0+0.58 s in the 10-1000 keV band is 6.1 +/- 1.2 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 #42119
J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), S. Lanava (PSU), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 7.6 ks of XRT data for GRB 251005C, from 129 s to 29.0 ks after the trigger. The data are entirely in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=1.34 (+/-0.06).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.41 (+0.27, -0.25). The best-fitting absorption column is 7.1 (+2.8, -2.2) x 10^21 cm^-2, in excess of the Galactic value of 3.2 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 6.4 x 10^-11 (8.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     7.1 (+2.8, -2.2) x 10^21 cm^-2
Galactic foreground: 3.2 x 10^21 cm^-2
Excess significance: 2.9 sigma
Photon index:	     1.41 (+0.27, -0.25)
```
If the light curve continues to decay with a power-law decay index of 1.34, the count rate at T+24 hours will be 4.2 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.7 x 10^-14 (3.5 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01401726.
This circular is an official product of the Swift-XRT team.
GCN Circular #42121
N. P. M. Kuin (MSSL/UCL) and K. L. Page (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 251005C 123 s after the BAT trigger (Page et al., GCN Circ. 42113). No optical afterglow consistent with the XRT position is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white_FC           123          273          147         >21.6
u_FC               336          586          246         >19.9
white              123         1536          392         >21.3
v                  666         1586          117         >19.4
b                  592         1676          108         >19.8
u                  336         1659          343         >20.0
w1                 715         1461           78         >19.4
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.461 in the direction of the burst (Schlegel et al. 1998).
Please note that the initial GCN (Page et al., GCN Circ. 42113) reported 251005A "A-burst", which was corrected to "C" : GRB 251005C.
GCN Circular #42122
A. Arya (IITB), U. Pathak (IITB), A. Goyal (IITB), Harsha K. H. (IUCAA), M. Tembhurnikar (IUCAA), S. Salunke (IUCAA), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB251005C which was also detected by Fermi/GBM (GCN Circ. 42118), Swift BAT (GCN Circ. 42113).
The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-10-05 16:06:52.04 UTC. The measured peak count rate associated with the burst is 218 (+69, -55) counts/s above the background in the combined data of all quadrants, with a total of 801 (+399, -369) counts. The local mean background count rate was 1373 (+5, -9) counts/s. Using cumulative rates, we measure a T90 of 9.6 (+5.3, -5.8) s.
The source was also faintly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-10-05 16:06:54.50 UTC. The measured peak count rate associated with the burst is 90 (+28, -31) counts/s above the background in the combined data of three quadrants (out of four), with a total of 133 (+86, -91) counts. The local mean background count rate was 225 (+3, -3) counts/s. Due to poor statistics, we cannot reliably estimate the T90 from it.
CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project.
CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb
GCN Circular #42123
J. T. Palmerio (CEA), L. P. Xin, H. L. Li, Y. N. Ma, Z. H. Yao, Y. L. Qiu, C. Wu, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC) report on behalf of the SVOM/VT team:
SVOM/VT performed a Target of Opportunity observation of GRB 251005C detected by Swift (Page et al., GCN 42113) and Fermi GBM (Smith et al., GCN 42118), starting at 2025-10-06T02:00:33 UTC, 9.90 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
An uncatalogued optical counterpart, compared to the PanSTARRS catalogue, is detected in VT_R at R.A., Dec. = 75.68455, 16.88019 degrees, equivalent to:
```
R.A. (J2000) = 05h02m44.3s 
Dec. (J2000) = +16d52m48.7s
```
with an uncertainty of 0.5 arcsec.
This location is 4.6 arcsec from the Swift-XRT position (Goad et al. GCN 42116), outside of the 90% confidence region of 2.3 arcsec. The candidate's magnitudes are given below:
```
  Mid_time     |   Band     |    Exposure Time  |     Magnitude (AB)
11.18  hour        VT_R            36*50 sec             22.64+/-0.25  mag                      
12.79  hour        VT_R            36*50 sec             22.81+/-0.25  mag
10.71  hour        VT_B            60*50 sec             >23.7 mag
12.86  hour        VT_B            50*50 sec             >23.6 mag
```
The fading of this candidate cannot be confirmed given the uncertainties.
Our photometry is not corrected for Galactic extinction.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular #42127
GRB 251005C: VLT/X-shooter Imaging
Muskan Yadav (U Rome), Yu-Han Yang (U Rome), Massine El Kabir (U Rome), Niccolò Passaleva (U Rome), Eleonora Troja (U Rome) report on behalf of the ERC BHianca team:
We observed the field of GRB 251005C (K. L. Page et al., GCN 42113) with the Xshooter spectrograph on the ESO VLT UT3 (Melipal). Observations began at T+16.5 hours. We obtained a total exposure of 335 s using the acquisition and guiding (A&G) camera. Observations were carried out in the i’ filter at an average airmass of about 1.4 and seeing 0.75 arcsec.
Within the XRT error region (Goad et al., GCN 42116) we detect a faint (i~24 AB mag) source at coordinates RA, Dec (J2000) = 05:02:44.03, +16:52:51.632. The object appears extended in our images. We also detect the SVOM/VT optical candidate (J. T. Palmeiro et al., GCN 42123) at a significantly fainter magnitude (i~24 AB mag), confirming its rapid fading. We thus suggest that this is the GRB optical counterpart.
We thank the staff at the VLT, for the rapid execution of these observations.
GCN Circular #42129
Alan M. Watson (UNAM), Francis Fortin (IRAP), Jean-Luc Atteia (IRAP), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), and Antonio de Ugarte Postigo (LAM):
We imaged the field of the Swift GRB 251005C (Page et al., GCN Circ. 42113) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-10-06 11:23 to 12:30 UTC (from 19.28 to 20.40 hours after the trigger) and obtained 38 minutes of simultaneous exposure in the i and z filters.
The data were reduced and coadded with the tenue software and analyzed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction.
At the position of the XRT source reported by Goad et al. (GCN Circ. 42116) and at the position of the VT optical source reported by Palmerio et al. (GCN Circ. 42123), we do not detect any sources above our 3-sigma limits of
```
i > 23.8
z > 23.3
```
However, at the position of the VT source there are hints of the presence of a faint resolved object at lower significance. Our results are consistent with the X-shooter photometry reported by Yadav et al. (GCN Circ. 42127).
We caution that the apparent fading in the i band with respect to the earlier VT_R detection is not conclusive, as the VT_R band above 650 nm includes both i and z, and our limit in z alone is not much deeper than the original detection.
We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams.
COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico.
GCN Circular #42135
SVOM/GRM team: Xing-Hao Luo, Chen-Wei Wang, Zheng-Hang Yu, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Frédéric Daigne (IAP), Stéphane Schanne (CEA)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a burst GRB 251005C(SVOM trigger reference: sb25100502) at 2025-10-05T16:06:54.000 UTC(T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#42118) and Swift/BAT (K. L. Page et al., GCN#42113)
With the event_by_event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multi-pulses with a T90 of 1.6 +0.6/-0.3 s in the 15-5000 keV band.
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb251005C.png
In addition, the position of this burst, as determined by Swift/XRT (RA=75.673 , DEC=16.882, GCN#42116), is located at about 51 degrees form the SVOM optical axis, which is outside the ECLAIRs field of view.
With this localization, the time-averaged spectrum from T0-0.4 to T0+1.6 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.81 +0.16/-0.14 and the cutoff energy, parameterized as Epeak, is 900 +547/-285 keV. The event fluence (10-1000 keV) in this time interval is (2.17 +0.19/-0.18)E-06 erg/cm^2.
The localization of GRB 251005C in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb251005C_amati.png
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM point of contact for this burst is: Xing-Hao Luo (2952704891@qq.com)
GCN Circular #42136
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team.
A second ToO observation from SVOM/VT was performed to the field of GRB 251005C (Page et al., GCN 42113; Smith et al., GCN 42118; Arya et al., GCN 42122; Luo et al., GCN 42135) which stared at 2025-10-06T17:36:01 UTC, I.e., 25.5 hours post trigger in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
The optical candidate (Palmerio et al. , GCN 42123; Yadav et al., GCN 42127; Watson et al., GCN 42129) was detected in VT_R stacked image at the mid time of 27.4 hours post trigger with the brightness of VT_R~23.3+/-0.2 mag. Combining earlier magnitudes from VT, the source was fading with a power-law temporal slope of about -0.7.
Our photometry was derived in AB magnitude and not corrected for Galactic extinction.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular #42153
M. El Kabir (U Rome), O. Guiffreda (UMD), N. Passaleva (U Rome), J. Durbak (UMD), E. Troja (U Rome), A. S. Kutyrev (NASA/GSFC), S. B. Cenko (NASA/GSFC)
Following the Swift/BAT detection and Swift/XRT localization of an uncatalogued source (Page et al, GCN 42113), we observed the transient field in J filter with PRIME ~32.9 hours after the initial BAT trigger.
Using Two Micron All Sky Survey (2MASS) for preliminary calibration we do not detect any uncatalogued source down to J>20.2 AB (3-sigma) not corrected for galactic extinction at the position of the candidates reported by Swift/XRT (Goad et al. GCN 42116), and SVOM/VT (Palmerio et al., GCN 42123).
PRIME is a 1.8m telescope with 1.56 square degree FOV (0.5 arcsec/pixel) located in Sutherland, South Africa at the South African Astronomical Observatory (SAAO) (Kutyrev et al. 2023, Yama et al. 2023, Durbak et al. 2024).
We thank the Osaka University observers at PRIME and the staff at SAAO for their support with these observations.

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Jochen Greiner, last update: 06-Oct-2025 [Disclaimer]