Gamma-ray Burst 250509A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:33:52 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1311764,   Seg_Num: 0
GRB_RA:           46.455d {+03h 05m 49s} (J2000),
                  46.697d {+03h 06m 47s} (current),
                  45.977d {+03h 03m 54s} (1950)
GRB_DEC:         -38.853d {-38d 51' 11"} (J2000),
                 -38.756d {-38d 45' 22"} (current),
                 -39.046d {-39d 02' 45"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       3732 [cnts]    Image_Peak=326 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       16469 [cnts]
BKG_TIME:        81196.42 SOD {22:33:16.42} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81210.63 SOD {22:33:30.63} UT
GRB_PHI:          53.92 [deg]
GRB_THETA:         9.42 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     33.15 [sigma]
IMAGE_SIGNIF:    12.76 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +2  +0  +0 -55  +0 
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 56"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.13d {+13h 08m 31s}   -9.42d {-09d 25' 18"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       26.57,-53.14 [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 = 225.15,20.24 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(1.0<100sec) coincident with the FERMI_GBM event (trignum=768522814).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 09 May 25 22:33:58 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      46
TRIGGER_NUM:     768522814
GRB_RA:           56.033d {+03h 44m 08s} (J2000),
                  56.296d {+03h 45m 11s} (current),
                  55.516d {+03h 42m 04s} (1950)
GRB_DEC:         -28.083d {-28d 04' 59"} (J2000),
                 -28.005d {-28d 00' 16"} (current),
                 -28.240d {-28d 14' 23"} (1950)
GRB_ERROR:       18.10 [deg radius, statistical plus systematic]
GRB_INTEN:       87 [cnts/sec]
DATA_SIGNIF:     9.40 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81209.29 SOD {22:33:29.29} UT
GRB_PHI:          46.00 [deg]
GRB_THETA:        80.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.09
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      90%  GRB
2nd_MOST_LIKELY:   5%  Solar Flare
DETECTORS:       0,1,1, 0,0,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 56"}
SUN_DIST:         46.48 [deg]   Sun_angle= -0.6 [hr] (East of Sun)
MOON_POSTN:      197.13d {+13h 08m 32s}   -9.42d {-09d 25' 20"}
MOON_DIST:       126.76 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      224.68,-51.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       44.48,-46.30 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 284.93,6.57 [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=1311764).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 09 May 25 22:34:07 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      59
TRIGGER_NUM:     768522814
GRB_RA:           44.583d {+02h 58m 20s} (J2000),
                  44.833d {+02h 59m 20s} (current),
                  44.092d {+02h 56m 22s} (1950)
GRB_DEC:         -37.300d {-37d 17' 59"} (J2000),
                 -37.200d {-37d 11' 58"} (current),
                 -37.499d {-37d 29' 56"} (1950)
GRB_ERROR:       10.07 [deg radius, statistical plus systematic]
GRB_INTEN:       151 [cnts/sec]
DATA_SIGNIF:     13.90 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81209.29 SOD {22:33:29.29} UT
GRB_PHI:          55.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      1.07
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      92%  GRB
2nd_MOST_LIKELY:   4%  Distant Particles
DETECTORS:       0,1,1, 0,0,0, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 56"}
SUN_DIST:         54.86 [deg]   Sun_angle= 0.2 [hr] (West of Sun)
MOON_POSTN:      197.13d {+13h 08m 32s}   -9.42d {-09d 25' 22"}
MOON_DIST:       126.64 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      241.82,-61.46 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       25.58,-51.09 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 284.93,6.57 [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=1311764).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 09 May 25 22:34:17 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     768522814
GRB_RA:           43.590d {+02h 54m 22s} (J2000),
                  43.856d {+02h 55m 25s} (current),
                  43.066d {+02h 52m 16s} (1950)
GRB_DEC:         -31.290d {-31d 17' 23"} (J2000),
                 -31.188d {-31d 11' 16"} (current),
                 -31.493d {-31d 29' 32"} (1950)
GRB_ERROR:       5.04 [deg radius, statistical only]
DATA_SIGNIF:     17.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81209.29 SOD {22:33:29.29} UT
GRB_PHI:          49.00 [deg]
GRB_THETA:        91.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 57"}
SUN_DIST:         48.90 [deg]   Sun_angle= 0.2 [hr] (West of Sun)
MOON_POSTN:      197.13d {+13h 08m 32s}   -9.42d {-09d 25' 24"}
MOON_DIST:       131.99 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      229.18,-62.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       28.35,-45.31 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_768522814.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(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1311764).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 09 May 25 22:35:09 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      1
TRIGGER_NUM:     768522814
GRB_RA:           47.140d {+03h 08m 34s} (J2000),
                  47.391d {+03h 09m 34s} (current),
                  46.644d {+03h 06m 35s} (1950)
GRB_DEC:         -35.340d {-35d 20' 23"} (J2000),
                 -35.244d {-35d 14' 38"} (current),
                 -35.530d {-35d 31' 48"} (1950)
GRB_ERROR:       3.58 [deg radius, statistical only]
DATA_SIGNIF:     22.90 [sigma]
DATA_INTERVAL:   12.288 [sec]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81209.29 SOD {22:33:29.29} UT
GRB_PHI:          53.00 [deg]
GRB_THETA:        88.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 57"}
SUN_DIST:         52.86 [deg]   Sun_angle= -0.0 [hr] (East of Sun)
MOON_POSTN:      197.14d {+13h 08m 34s}   -9.43d {-09d 25' 35"}
MOON_DIST:       126.97 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      237.23,-59.73 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       29.86,-50.22 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_768522814.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1311764).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 09 May 25 22:34:56 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     768522814
GRB_RA:           45.720d {+03h 02m 53s} (J2000),
                  45.978d {+03h 03m 55s} (current),
                  45.210d {+03h 00m 51s} (1950)
GRB_DEC:         -33.330d {-33d 19' 47"} (J2000),
                 -33.232d {-33d 13' 53"} (current),
                 -33.525d {-33d 31' 30"} (1950)
GRB_ERROR:       4.41 [deg radius, statistical only]
DATA_SIGNIF:     18.40 [sigma]
DATA_INTERVAL:   7.168 [sec]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81209.29 SOD {22:33:29.29} UT
GRB_PHI:          51.00 [deg]
GRB_THETA:        89.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 57"}
SUN_DIST:         50.86 [deg]   Sun_angle= 0.1 [hr] (West of Sun)
MOON_POSTN:      197.14d {+13h 08m 33s}   -9.43d {-09d 25' 33"}
MOON_DIST:       129.28 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      233.38,-61.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       29.52,-47.91 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_768522814.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1311764).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 09 May 25 22:42:46 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     768522814
GRB_RA:           45.960d {+03h 03m 50s} (J2000),
                  46.213d {+03h 04m 51s} (current),
                  45.461d {+03h 01m 51s} (1950)
GRB_DEC:         -35.340d {-35d 20' 23"} (J2000),
                 -35.242d {-35d 14' 31"} (current),
                 -35.534d {-35d 32' 03"} (1950)
GRB_ERROR:       3.04 [deg radius, statistical only]
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81209.29 SOD {22:33:29.29} UT
GRB_PHI:          53.00 [deg]
GRB_THETA:        89.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        47.10d {+03h 08m 24s}  +17.62d {+17d 37' 02"}
SUN_DIST:         52.87 [deg]   Sun_angle= 0.1 [hr] (West of Sun)
MOON_POSTN:      197.20d {+13h 08m 47s}   -9.46d {-09d 27' 18"}
MOON_DIST:       127.57 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      237.45,-60.68 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       28.50,-49.81 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_locplot_all_bn250509940.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1311764).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:35:18 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1311764,   Seg_Num: 0
GRB_RA:           46.4509d {+03h 05m 48.2s} (J2000),
                  46.6934d {+03h 06m 46.4s} (current),
                  45.9728d {+03h 03m 53.4s} (1950)
GRB_DEC:         -38.8412d {-38d 50' 28.3"} (J2000),
                 -38.7442d {-38d 44' 39.0"} (current),
                 -39.0339d {-39d 02' 01.8"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       179 [cnts]
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81281.71 SOD {22:34:41.71} UT,   71.1 [sec] since BAT Trigger Time
CENTROID_X:      295.76,  raw= 296  [pixels]
CENTROID_Y:      304.68,  raw= 305  [pixels]
ROLL:            0.73 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   14.11
GRB_POS_XRT_Z:   -37.31
IMAGE_URL:       sw01311764000msxps_rw.img
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 57"}
SUN_DIST:         56.36 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.14d {+13h 08m 34s}   -9.43d {-09d 25' 37"}
MOON_DIST:       124.53 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.26,-59.70 [deg] galactic lon,lat of the burst
ECL_COORDS:       26.58,-53.13 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:35:16 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1311764,   Seg_Num: 0
GRB_RA:           46.4509d {+03h 05m 48.2s} (J2000),
                  46.6934d {+03h 06m 46.4s} (current),
                  45.9728d {+03h 03m 53.4s} (1950)
GRB_DEC:         -38.8412d {-38d 50' 28.3"} (J2000),
                 -38.7442d {-38d 44' 39.0"} (current),
                 -39.0339d {-39d 02' 01.8"} (1950)
GRB_ERROR:       4.7 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       179 [cnts]
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81281.71 SOD {22:34:41.71} UT,   71.1 [sec] since BAT Trigger Time
CENTROID_X:      295.76,  raw= 296  [pixels]
CENTROID_Y:      304.68,  raw= 305  [pixels]
ROLL:            0.73 [deg]
GAIN:            2
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   14.11
GRB_POS_XRT_Z:   -37.31
IMAGE_URL:       sw01311764000msxps_rw.img
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 57"}
SUN_DIST:         56.36 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.14d {+13h 08m 34s}   -9.43d {-09d 25' 37"}
MOON_DIST:       124.53 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.26,-59.70 [deg] galactic lon,lat of the burst
ECL_COORDS:       26.58,-53.13 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:35:06 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1311764,   Seg_Num: 0
GRB_RA:           46.4509d {+03h 05m 48.21s} (J2000),
                  46.6934d {+03h 06m 46.40s} (current),
                  45.9728d {+03h 03m 53.46s} (1950)
GRB_DEC:         -38.8412d {-38d 50' 28.3"} (J2000),
                 -38.7442d {-38d 44' 39.0"} (current),
                 -39.0339d {-39d 02' 01.8"} (1950)
GRB_ERROR:       4.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       7.21e-09 [erg/cm2/sec]
GRB_SIGNIF:      13.37 [sigma]
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81281.71 SOD {22:34:41.71} UT,   71.1 [sec] since BAT Trigger Time
TAM[0-3]:        327.65 237.12 261.75 243.32
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 57"}
SUN_DIST:         56.36 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.14d {+13h 08m 34s}   -9.43d {-09d 25' 35"}
MOON_DIST:       124.53 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.26,-59.70 [deg] galactic lon,lat of the burst
ECL_COORDS:       26.58,-53.13 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 0.75 arcmin from the BAT position.  
COMMENTS:        The object found at this position is either a very bright burst or a cosmic ray hit.  
COMMENTS:        Examine the XRT Image to differentiate (CRs are much more compact); see examples at:  
COMMENTS:        http://www.swift.psu.edu/xrt/XRT_Postage_Stamp_Image_Photo_Gallery.htm .

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:36:54 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1311764,   Seg_Num: 0
GRB_RA:           46.455d {+03h 05m 49s} (J2000),
                  46.697d {+03h 06m 47s} (current),
                  45.977d {+03h 03m 54s} (1950)
GRB_DEC:         -38.853d {-38d 51' 11"} (J2000),
                 -38.756d {-38d 45' 22"} (current),
                 -39.046d {-39d 02' 45"} (1950)
GRB_DATE:        20804 TJD;   129 DOY;   25/05/09
GRB_TIME:        81210.63 SOD {22:33:30.63} UT
TRIGGER_INDEX:   146
GRB_PHI:          53.92 [deg]
GRB_THETA:         9.42 [deg]
DELTA_TIME:      19.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     33.15 [sigma]
IMAGE_SIGNIF:    12.76 [sigma]
LC_URL:          sw01311764000msb.lc
SUN_POSTN:        47.10d {+03h 08m 23s}  +17.62d {+17d 36' 58"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.15d {+13h 08m 37s}   -9.43d {-09d 26' 00"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       26.57,-53.14 [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 = 225.15,20.24 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:40:05 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1311764,   Seg_Num: 0
POINT_RA:         46.456d {+03h 05m 49s} (J2000)
POINT_DEC:       -38.852d {-38d 51' 04"} (J2000)
POINT_ROLL:      0.729d
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81291.11 SOD {22:34:51.11} UT,   80.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.131
N_STARS:         15
X_OFFSET:        464 [pixels]
Y_OFFSET:        560 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1519 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw01311764000msufc0080.fits
SUN_POSTN:        47.10d {+03h 08m 24s}  +17.62d {+17d 37' 00"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.18d {+13h 08m 43s}   -9.45d {-09d 26' 42"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       26.58,-53.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #40406
The Fermi GBM team reports the detection of a likely LONG GRB
At 22:33:29 UT on 9 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250509A (trigger 768522814.285632 / 250509940).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 46.0, Dec = -35.3 (J2000 degrees, equivalent to J2000 03h 04m, -35d 17'), with a statistical uncertainty of 3.0 degrees.
The angle from the Fermi LAT boresight is 89.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_skymap_all_bn250509940.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/bn250509940/quicklook/glg_healpix_all_bn250509940.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250509940/quicklook/glg_lc_medres34_bn250509940.gif

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:49:14 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1311764,   Seg_Num: 0
POINT_RA:         46.455d {+03h 05m 49s} (J2000)
POINT_DEC:       -38.851d {-38d 51' 03"} (J2000)
POINT_ROLL:      0.730d
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81503.21 SOD {22:38:23.21} UT,   292.6 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.708
N_STARS:         7
X_OFFSET:        527 [pixels]
Y_OFFSET:        501 [pixels]
X_MAX:           1486 [pixels]
Y_MAX:           1460 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01311764000msufc0292.fits
SUN_POSTN:        47.11d {+03h 08m 25s}  +17.62d {+17d 37' 06"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.25d {+13h 08m 59s}   -9.48d {-09d 28' 45"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       26.57,-53.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #40407
M. H. Siegel (PSU), S. Dichiara (PSU), R. Gupta (NASA GSFC) and B. Sbarufatti (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team:
At 22:33:30 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250509A (trigger=1311764). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 46.455, -38.853 which is
```
   RA(J2000) = 03h 05m 49s
   Dec(J2000) = -38d 51' 11"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi peak structure with a duration of about 60 sec. The peak count rate was ~2800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 22:34:41.7 UT, 71.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source located at RA, Dec 46.45032, -38.84173 which is equivalent to:
```
   RA(J2000)  = 03h 05m 48.08s
   Dec(J2000) = -38d 50' 30.2"
```
with an uncertainty of 3.6 arcseconds (radius, 90% containment). This location is 42 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 (2.03 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 9.2 (+3.98/-3.41) x 10^21 cm^-2 (90% confidence).
The initial flux in the 2.5 s image was 7.21e-09 erg cm^-2 s^-1 (0.2-10 keV).
UVOT took a finding chart exposure of nominal 150.000 seconds with the White filter starting 80 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. Data from the 2.7'x2.7' sub-image are not available at this time. 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 0.021.
Burst Advocate for this burst is M. H. Siegel (siegel AT swift.psu.edu). 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:     Fri 09 May 25 22:49:23 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1311764,   Seg_Num: 0
POINT_RA:         46.455d {+03h 05m 49s} (J2000)
POINT_DEC:       -38.851d {-38d 51' 03"} (J2000)
POINT_ROLL:      0.730d
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81503.21 SOD {22:38:23.21} UT,   292.6 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        2.708
N_STARS:         7
X_OFFSET:        527 [pixels]
Y_OFFSET:        501 [pixels]
X_MAX:           1486 [pixels]
Y_MAX:           1460 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01311764000msufc0292.fits
SUN_POSTN:        47.11d {+03h 08m 25s}  +17.62d {+17d 37' 06"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.25d {+13h 08m 59s}   -9.48d {-09d 28' 47"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       26.57,-53.14 [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:     Fri 09 May 25 22:49:44 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1311764,   Seg_Num: 0
GRB_RA:           46.4495d {+03h 05m 47.88s} (J2000),
                  46.6920d {+03h 06m 46.07s} (current),
                  45.9714d {+03h 03m 53.12s} (1950)
GRB_DEC:         -38.8413d {-38d 50' 28.6"} (J2000),
                 -38.7443d {-38d 44' 39.3"} (current),
                 -39.0340d {-39d 02' 02.2"} (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:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81446.00 SOD {22:37:26.00} UT,   235.4 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        47.11d {+03h 08m 25s}  +17.62d {+17d 37' 07"}
SUN_DIST:         56.36 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.25d {+13h 09m 00s}   -9.48d {-09d 28' 52"}
MOON_DIST:       124.53 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.26,-59.70 [deg] galactic lon,lat of the burst
ECL_COORDS:       26.58,-53.13 [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:     Fri 09 May 25 22:50:43 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1311764,   Seg_Num: 0
POINT_RA:         46.455d {+03h 05m 49s} (J2000)
POINT_DEC:       -38.851d {-38d 51' 03"} (J2000)
ROLL:            0.730d
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81503.21 SOD {22:38:23.21} UT,   292.6 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     768523138
X_OFFSET:        847 [pixels]
Y_OFFSET:        821 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1007
Y_GRB_POS:       981
BINNING_INDEX:   1
IM_URL:          sw01311764000msuni0328.fits
SUN_POSTN:        47.11d {+03h 08m 26s}  +17.62d {+17d 37' 07"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.26d {+13h 09m 02s}   -9.48d {-09d 29' 05"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       26.57,-53.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:50:37 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1311764,   Seg_Num: 0
POINT_RA:         46.455d {+03h 05m 49s} (J2000)
POINT_DEC:       -38.851d {-38d 51' 03"} (J2000)
ROLL:            0.730d
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81503.21 SOD {22:38:23.21} UT,   292.6 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     768523138
X_OFFSET:        847 [pixels]
Y_OFFSET:        821 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1007
Y_GRB_POS:       981
BINNING_INDEX:   1
IM_URL:          sw01311764000msuni0328.fits
SUN_POSTN:        47.11d {+03h 08m 26s}  +17.62d {+17d 37' 07"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.26d {+13h 09m 01s}   -9.48d {-09d 29' 04"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       26.57,-53.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the XRT Position Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN Circular #40408
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 250509A ( M. H. Siegel et al., GCN 40407) errorbox 1296 sec after notice time and 1332 sec after trigger time at 2025-05-09 22:55:43 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 76 deg. The sun altitude is -14.1 deg.
The galactic latitude b = -59 deg., longitude l = 244 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2866479
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    1423 |         MASTER-OAFA |   C |   180 | 18.2 |        
    1609 |         MASTER-OAFA |   C |   180 | 18.4 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.

GCN Circular #40409
V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 250509A ( Fermi GBM team, GCN 40406) errorbox 7 sec after notice time and 64 sec after trigger time at 2025-05-09 22:34:33 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 70 deg. The sun altitude is -9.7 deg.
The galactic latitude b = -60 deg., longitude l = 237 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2866536
We obtain a following upper limits.

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

      70 | 2025-05-09 22:34:33 |         MASTER-OAFA | (03h 18m 00.28s , -38d 23m 19.1s) |   C |    10 | 14.1 |        
     104 | 2025-05-09 22:35:03 |         MASTER-OAFA | (03h 18m 00.24s , -38d 23m 19.1s) |   C |    20 | 14.5 |        
     138 | 2025-05-09 22:35:42 |         MASTER-OAFA | (03h 18m 00.14s , -38d 23m 18.9s) |   C |    10 | 14.4 |        
     174 | 2025-05-09 22:36:18 |         MASTER-OAFA | (03h 18m 00.11s , -38d 23m 18.5s) |   C |    10 | 14.4 |        
     215 | 2025-05-09 22:36:53 |         MASTER-OAFA | (03h 18m 00.10s , -38d 23m 18.6s) |   C |    20 | 14.7 |        
     265 | 2025-05-09 22:37:39 |         MASTER-OAFA | (03h 18m 00.12s , -38d 23m 19.3s) |   C |    30 | 14.8 |        
     865 | 2025-05-09 22:46:44 |         MASTER-OAFA | (03h 18m 00.32s , -38d 23m 28.0s) |   C |   140 | 14.8 |        
    1041 | 2025-05-09 22:49:30 |         MASTER-OAFA | (03h 18m 00.52s , -38d 23m 31.2s) |   C |   160 | 16.3 |        
    1227 | 2025-05-09 22:52:36 |         MASTER-OAFA | (03h 18m 00.73s , -38d 23m 34.3s) |   C |   160 | 16.5 |        
    1414 | 2025-05-09 22:55:42 |         MASTER-OAFA | (03h 18m 01.03s , -38d 23m 38.0s) |   C |   160 | 17.0 |        
    1424 | 2025-05-09 22:55:43 |         MASTER-OAFA | (03h 06m 24.43s , -38d 43m 44.4s) |   C |   180 | 18.2 |        
    1600 | 2025-05-09 22:58:49 |         MASTER-OAFA | (03h 18m 01.35s , -38d 23m 42.3s) |   C |   160 | 17.1 |        
    1610 | 2025-05-09 22:58:49 |         MASTER-OAFA | (03h 06m 24.67s , -38d 43m 47.0s) |   C |   180 | 18.4 |        
    1786 | 2025-05-09 23:01:55 |         MASTER-OAFA | (03h 18m 01.74s , -38d 23m 46.7s) |   C |   160 | 17.1 |        
    1796 | 2025-05-09 23:01:55 |         MASTER-OAFA | (03h 06m 24.96s , -38d 43m 50.0s) |   C |   180 | 18.3 |        
    1972 | 2025-05-09 23:05:01 |         MASTER-OAFA | (03h 18m 02.05s , -38d 23m 50.9s) |   C |   160 | 17.1 |        
    1983 | 2025-05-09 23:05:02 |         MASTER-OAFA | (03h 06m 25.27s , -38d 43m 53.2s) |   C |   180 | 18.2 |        
    2159 | 2025-05-09 23:08:08 |         MASTER-OAFA | (03h 18m 02.30s , -38d 23m 55.2s) |   C |   160 | 17.1 |        
    2169 | 2025-05-09 23:08:08 |         MASTER-OAFA | (03h 06m 25.58s , -38d 43m 56.5s) |   C |   180 | 18.1 |        
    2356 | 2025-05-09 23:11:14 |         MASTER-OAFA | (03h 06m 25.97s , -38d 44m 00.1s) |   C |   180 | 18.0 |        
    2531 | 2025-05-09 23:14:20 |         MASTER-OAFA | (03h 18m 02.98s , -38d 24m 03.8s) |   C |   160 | 17.1 |        
    2542 | 2025-05-09 23:14:20 |         MASTER-OAFA | (03h 06m 26.35s , -38d 44m 03.6s) |   C |   180 | 18.0 |        
    2718 | 2025-05-09 23:17:26 |         MASTER-OAFA | (03h 18m 03.37s , -38d 24m 09.0s) |   C |   160 | 17.2 |        
    2728 | 2025-05-09 23:17:27 |         MASTER-OAFA | (03h 06m 26.66s , -38d 44m 06.7s) |   C |   180 | 18.0 |        
    2904 | 2025-05-09 23:20:33 |         MASTER-OAFA | (03h 18m 03.73s , -38d 24m 14.1s) |   C |   160 | 17.1 |        
    2914 | 2025-05-09 23:20:33 |         MASTER-OAFA | (03h 06m 26.94s , -38d 44m 08.8s) |   C |   180 | 17.6 |        
    3090 | 2025-05-09 23:23:39 |         MASTER-OAFA | (03h 18m 04.07s , -38d 24m 19.9s) |   C |   160 | 16.9 |        
    3100 | 2025-05-09 23:23:39 |         MASTER-OAFA | (03h 06m 27.22s , -38d 44m 12.4s) |   C |   180 | 17.4 |

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

GCN Circular #40410
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using 426 s of promptly downlinked XRT event data for GRB 250509A, we find an enhanced XRT position of the afterglow: RA, Dec: 46.44960, -38.84128 which is equivalent to:
```
   RA (J2000)  = 03 05 47.90
   Dec (J2000) = -38 50 28.6
```
with an uncertainty of 1.9 arcseconds (radius, 90% confidence). Analysis of the promptly available data is online at http://www.swift.ac.uk/sper/1311764.
Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177).
This circular is an official product of the Swift-XRT team.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Fri 09 May 25 22:40:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1311764,   Seg_Num: 0
POINT_RA:         46.456d {+03h 05m 49s} (J2000)
POINT_DEC:       -38.852d {-38d 51' 04"} (J2000)
POINT_ROLL:      0.729d
IMG_START_DATE:  20804 TJD;   129 DOY;   25/05/09
IMG_START_TIME:  81291.11 SOD {22:34:51.11} UT,   80.5 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        7.131
N_STARS:         15
X_OFFSET:        464 [pixels]
Y_OFFSET:        560 [pixels]
X_MAX:           1423 [pixels]
Y_MAX:           1519 [pixels]
DET_THRESH:      23
PHOTO_THRESH:    14
SL_URL:          sw01311764000msufc0080.fits
SUN_POSTN:        47.10d {+03h 08m 24s}  +17.62d {+17d 37' 01"}
SUN_DIST:         56.37 [deg]   Sun_angle= 0.0 [hr] (West of Sun)
MOON_POSTN:      197.18d {+13h 08m 43s}   -9.45d {-09d 26' 45"}
MOON_DIST:       124.52 [deg]
MOON_ILLUM:      93 [%]
GAL_COORDS:      244.28,-59.70 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       26.58,-53.14 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #40411
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 877 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250509A, 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 = 46.44965, -38.84201 which is equivalent
```
RA (J2000): 03h 05m 47.92s
Dec (J2000): -38d 50' 31.2"
```
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 #40416
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.8 ks of XRT data for GRB 250509A, from 63 s to 28.3 ks after the trigger. The data comprise 156 s in Windowed Timing (WT) mode (the first 6 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode.
The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=3.20 (+/-0.09). At T+349 s the decay flattens to an alpha of -1.1 (+0.7, -0.4) before breaking again at T+1377 s to a final decay with index alpha=1.44 (+0.10, -0.09).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.02 (+0.11, -0.10). The best-fitting absorption column is 6.6 (+/-0.7) x 10^21 cm^-2, in excess of the Galactic value of 2.0 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 2.13 (+/-0.15) and a best-fitting absorption column of 6.0 (+1.0, -0.9) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.1 x 10^-11 (7.5 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     6.0 (+1.0, -0.9) x 10^21 cm^-2
Galactic foreground: 2.0 x 10^20 cm^-2
Excess significance: 10.7 sigma
Photon index:	     2.13 (+/-0.15)
```
If the light curve continues to decay with a power-law decay index of 1.44, the count rate at T+24 hours will be 9.5 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 3.9 x 10^-13 (7.1 x 10^-13) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01311764.
This circular is an official product of the Swift-XRT team.
GCN Circular #40422
A. Myers (NPP/GSFC), C. Meegan (UAH) and A. Holzmann Airasca (UniTrento and INFN Bari) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 22:33:29.29 UT on 09 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250509A (trigger 768522814/250509940). which was also detected by Swift BAT (M. H. Siegel et al. 2025, GCN 40407). The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 89 degrees.
The GBM light curve consists of main emission episode with a duration (T90) of about 69 s (50-300 keV). The time-averaged spectrum from T0+0.000 to T0+69.120 s is best fit by a power law function. The power law index is -2.19 +/- 0.03.
The event fluence (10-1000 keV) in this time interval is (6.18 +/- 0.29)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+6.2 s in the 10-1000 keV band is 3.6 +/- 0.3 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:
GCN Circular #40456
T. Parsotan (GSFC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU), M. H. Siegel (PSU) (i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250509A (trigger #1311764) (Siegel, et al., GCN Circ. 40407). The BAT ground-calculated position is RA, Dec = 46.451, -38.854 deg which is
```
   RA(J2000)  =  03h 05m 48.3s 
   Dec(J2000) = -38d 51' 15.1" 
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 96%.
The mask-weighted BAT light curve shows a sharp rise and exponential decay profile. T90 (15-350 keV) is 55.43 +- 10.47 sec (estimated error including systematics).
The time-averaged spectrum from T-2.85 to T+71.46 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.54 +- 0.08. The fluence in the 15-150 keV band is 2.4 +- 0.1 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+0.42 sec in the 15-150 keV band is 1.9 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1311764

Back to JG's homepage

Jochen Greiner, last update: 14-May-2025 [Disclaimer]