Gamma-ray Burst 240527B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:04:09 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      44
TRIGGER_NUM:     738511436
GRB_RA:          124.600d {+08h 18m 24s} (J2000),
                 124.887d {+08h 19m 33s} (current),
                 124.012d {+08h 16m 03s} (1950)
GRB_DEC:         -12.933d {-12d 55' 59"} (J2000),
                 -13.011d {-13d 00' 38"} (current),
                 -12.776d {-12d 46' 34"} (1950)
GRB_ERROR:       7.23 [deg radius, statistical plus systematic]
GRB_INTEN:       273 [cnts/sec]
DATA_SIGNIF:     11.50 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         287.00 [deg]
GRB_THETA:        75.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.82
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      71%  GRB
2nd_MOST_LIKELY:  27%  Distant Particles
DETECTORS:       0,0,0, 0,1,0, 0,1,1, 0,0,0, 0,0,
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 13"}
SUN_DIST:         68.17 [deg]   Sun_angle= -4.0 [hr] (East of Sun)
MOON_POSTN:      299.22d {+19h 56m 52s}  -25.86d {-25d 51' 39"}
MOON_DIST:       140.74 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      234.83, 12.66 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      130.54,-31.63 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 288.93,15.25 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:04:45 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      67
TRIGGER_NUM:     738511436
GRB_RA:          123.967d {+08h 15m 52s} (J2000),
                 124.235d {+08h 16m 56s} (current),
                 123.417d {+08h 13m 40s} (1950)
GRB_DEC:         -21.550d {-21d 33' 00"} (J2000),
                 -21.626d {-21d 37' 33"} (current),
                 -21.396d {-21d 23' 43"} (1950)
GRB_ERROR:       6.13 [deg radius, statistical plus systematic]
GRB_INTEN:       543 [cnts/sec]
DATA_SIGNIF:     23.10 [sigma]
INTEG_TIME:      1.024 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         279.00 [deg]
GRB_THETA:        70.00 [deg]
DATA_TIME_SCALE: 1.0240 [sec]
HARD_RATIO:      0.75
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      56%  GRB
2nd_MOST_LIKELY:  42%  Distant Particles
DETECTORS:       0,0,0, 0,1,0, 0,1,1, 0,0,0, 0,0,
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 14"}
SUN_DIST:         72.12 [deg]   Sun_angle= -4.0 [hr] (East of Sun)
MOON_POSTN:      299.22d {+19h 56m 54s}  -25.86d {-25d 51' 35"}
MOON_DIST:       132.27 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      241.86,  7.50 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      132.78,-40.08 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 288.93,15.25 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:04:52 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      71
TRIGGER_NUM:     738511436
GRB_RA:          117.867d {+07h 51m 28s} (J2000),
                 118.133d {+07h 52m 32s} (current),
                 117.321d {+07h 49m 17s} (1950)
GRB_DEC:         -21.183d {-21d 10' 59"} (J2000),
                 -21.247d {-21d 14' 48"} (current),
                 -21.054d {-21d 03' 15"} (1950)
GRB_ERROR:       5.83 [deg radius, statistical plus systematic]
GRB_INTEN:       457 [cnts/sec]
DATA_SIGNIF:     41.80 [sigma]
INTEG_TIME:      4.096 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         282.00 [deg]
GRB_THETA:        65.00 [deg]
DATA_TIME_SCALE: 4.0960 [sec]
HARD_RATIO:      0.78
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      63%  GRB
2nd_MOST_LIKELY:  35%  Distant Particles
DETECTORS:       0,0,0, 0,1,0, 0,1,1, 0,0,0, 0,0,
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 14"}
SUN_DIST:         67.22 [deg]   Sun_angle= -3.5 [hr] (East of Sun)
MOON_POSTN:      299.23d {+19h 56m 54s}  -25.86d {-25d 51' 34"}
MOON_DIST:       132.88 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      238.54,  2.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      125.43,-41.26 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 288.93,15.25 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:04:40 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      57
TRIGGER_NUM:     738511436
GRB_RA:          129.190d {+08h 36m 46s} (J2000),
                 129.479d {+08h 37m 55s} (current),
                 128.598d {+08h 34m 23s} (1950)
GRB_DEC:         -12.600d {-12d 35' 59"} (J2000),
                 -12.686d {-12d 41' 09"} (current),
                 -12.425d {-12d 25' 30"} (1950)
GRB_ERROR:       3.18 [deg radius, statistical only]
DATA_SIGNIF:     21.80 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         285.00 [deg]
GRB_THETA:        79.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 14"}
SUN_DIST:         71.94 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:      299.22d {+19h 56m 54s}  -25.86d {-25d 51' 36"}
MOON_DIST:       140.18 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      237.05, 16.61 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      135.44,-30.07 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_738511436.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(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:06:14 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      1
TRIGGER_NUM:     738511436
GRB_RA:          129.590d {+08h 38m 22s} (J2000),
                 129.882d {+08h 39m 32s} (current),
                 128.992d {+08h 35m 58s} (1950)
GRB_DEC:         -11.210d {-11d 12' 35"} (J2000),
                 -11.297d {-11d 17' 48"} (current),
                 -11.034d {-11d 02' 00"} (1950)
GRB_ERROR:       3.17 [deg radius, statistical only]
DATA_SIGNIF:     22.60 [sigma]
DATA_INTERVAL:   9.216 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         286.00 [deg]
GRB_THETA:        80.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 14"}
SUN_DIST:         71.64 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:      299.24d {+19h 56m 57s}  -25.86d {-25d 51' 24"}
MOON_DIST:       141.43 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      236.06, 17.70 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      135.41,-28.62 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_738511436.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(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:06:38 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      2
TRIGGER_NUM:     738511436
GRB_RA:          129.230d {+08h 36m 55s} (J2000),
                 129.519d {+08h 38m 05s} (current),
                 128.637d {+08h 34m 33s} (1950)
GRB_DEC:         -12.520d {-12d 31' 11"} (J2000),
                 -12.606d {-12d 36' 21"} (current),
                 -12.345d {-12d 20' 41"} (1950)
GRB_ERROR:       2.61 [deg radius, statistical only]
DATA_SIGNIF:     30.20 [sigma]
DATA_INTERVAL:   11.264 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         285.00 [deg]
GRB_THETA:        79.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 14"}
SUN_DIST:         71.94 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:      299.24d {+19h 56m 58s}  -25.86d {-25d 51' 21"}
MOON_DIST:       140.26 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      237.00, 16.68 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      135.46,-29.98 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_738511436.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(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:06:50 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      3
TRIGGER_NUM:     738511436
GRB_RA:          128.850d {+08h 35m 24s} (J2000),
                 129.137d {+08h 36m 33s} (current),
                 128.263d {+08h 33m 03s} (1950)
GRB_DEC:         -13.840d {-13d 50' 23"} (J2000),
                 -13.925d {-13d 55' 31"} (current),
                 -13.666d {-13d 39' 58"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
DATA_SIGNIF:     45.40 [sigma]
DATA_INTERVAL:   13.312 [sec]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         284.00 [deg]
GRB_THETA:        78.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        64.93d {+04h 19m 44s}  +21.44d {+21d 26' 15"}
SUN_DIST:         72.23 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:      299.25d {+19h 56m 59s}  -25.86d {-25d 51' 20"}
MOON_DIST:       139.07 [deg]
MOON_ILLUM:      83 [%]
GAL_COORDS:      237.93, 15.64 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      135.50,-31.35 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_738511436.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(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 14:55:37 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     738511436
GRB_RA:          128.510d {+08h 34m 02s} (J2000),
                 128.799d {+08h 35m 12s} (current),
                 127.918d {+08h 31m 40s} (1950)
GRB_DEC:         -12.680d {-12d 40' 47"} (J2000),
                 -12.765d {-12d 45' 52"} (current),
                 -12.508d {-12d 30' 27"} (1950)
GRB_ERROR:       1.70 [deg radius, statistical only]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
GRB_PHI:         285.33 [deg]
GRB_THETA:        78.49 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:        64.97d {+04h 19m 53s}  +21.44d {+21d 26' 34"}
SUN_DIST:         71.36 [deg]   Sun_angle= -4.3 [hr] (East of Sun)
MOON_POSTN:      299.75d {+19h 58m 59s}  -25.76d {-25d 45' 24"}
MOON_DIST:       140.48 [deg]
MOON_ILLUM:      82 [%]
GAL_COORDS:      236.73, 16.01 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      134.74,-30.34 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_locplot_all_bn240527586.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(11.0<100sec) coincident with the INTEGRAL_SPIACS event (trignum=10719).

GCN Circular #36545
T. Preis, B. Biltzinger, J. Burgess & J. Greiner (all MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 738511436 at 14:03:51 on 27 May 2024 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60).
The best-fit position is:
```
RA(2000.0) = 128.0 deg
Decl.(2000.0) = -15.2 deg
```
The 1 sigma statistical error radius is 3.4 deg. We estimate an additional systematic error of 2 deg.
Further details are available at: https://grb.mpe.mpg.de/grb/GRB240527586/
The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB240527586/healpix
The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB240527586/json
GCN Circular #36546
The Fermi GBM team reports the detection of a likely LONG GRB
"At 14:03:51.50 UT on 27 May 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240527B (trigger 738511436/240527586).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 128.51, Dec = -12.68 (J2000 degrees, equivalent to J2000 8h 34m, -12d 40'), with a statistical uncertainty of 1.70 degrees.
The angle from the Fermi LAT boresight is 78 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_skymap_all_bn240527586.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_healpix_all_bn240527586.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2024/bn240527586/quicklook/glg_lc_medres34_bn240527586.gif"

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Mon 27 May 24 21:00:52 UT
NOTICE_TYPE:     Fermi-LAT Offline Position
TRIGGER_NUM:     738511436
GRB_RA:          128.100d {+08h 32m 24s} (J2000),
                 128.385d {+08h 33m 32s} (current),
                 127.516d {+08h 30m 04s} (1950)
GRB_DEC:         -14.480d {-14d 28' 47"} (J2000),
                 -14.564d {-14d 33' 50"} (current),
                 -14.309d {-14d 18' 33"} (1950)
GRB_ERROR:       11.40 [arcmin radius, 90% containment, statistical only]
GRB_DATE:        20457 TJD;   148 DOY;   24/05/27
GRB_TIME:        50631.50 SOD {14:03:51.50} UT
TRIGGER_ID:      0x20000000
MISC:            0x40000000
SUN_POSTN:        65.23d {+04h 20m 55s}  +21.48d {+21d 29' 01"}
SUN_DIST:         71.67 [deg]   Sun_angle= -4.2 [hr] (East of Sun)
MOON_POSTN:      303.47d {+20h 13m 53s}  -24.96d {-24d 57' 35"}
MOON_DIST:       140.19 [deg]
MOON_ILLUM:      80 [%]
GAL_COORDS:      238.06, 14.68 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      134.90,-32.17 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi LAT Offline position.
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        It is the result of human-in-the-loop processing.  
COMMENTS:        This is a human generated position of a LAT ground detection.
COMMENTS:        This source corresponds to GBM trigger.

GCN Circular #36547
V. Lipunov, V.Kornilov, E. Gorbovskoy, K. Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, V.Senik, D. Vlasenko, G.Antipov, D.Zimnukhov, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D. Cheryasov, Ya.Kechin, Yu.Tselik, A. Sosnovskij (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gress, N.M. Budnev, O.Ershova (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich (Blagoveschensk Educational State University)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 240527B ( Fermi GBM team, GCN 36546) errorbox 9266 sec after notice time and 9291 sec after trigger time at 2024-05-27 16:38:42 UT, with upper limit up to 19.4 mag. Observations started at twilight. The observations began at zenith distance = 33 deg. The sun altitude is -11.7 deg.
The galactic latitude b = 16 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=2472451
We obtain a following upper limits.

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


    9321 | 2024-05-27 16:38:42 |         MASTER-SAAO | (08h 28m 27.08s , -12d 11m 25.9s) |   C |    60 | 18.5 |        
    9401 | 2024-05-27 16:40:02 |         MASTER-SAAO | (08h 36m 37.47s , -12d 10m 23.3s) |   C |    60 | 18.6 |        
   10243 | 2024-05-27 16:54:04 |         MASTER-SAAO | (08h 28m 28.80s , -12d 10m 06.2s) |   C |    60 | 19.1 |        
   10323 | 2024-05-27 16:55:24 |         MASTER-SAAO | (08h 36m 36.04s , -12d 10m 49.2s) |   C |    60 | 19.3 |        
   10403 | 2024-05-27 16:56:44 |         MASTER-SAAO | (08h 32m 25.70s , -14d 04m 43.2s) |   C |    60 | 19.2 |        
   10483 | 2024-05-27 16:58:04 |         MASTER-SAAO | (08h 40m 34.75s , -14d 05m 43.1s) |   C |    60 | 19.2 |        
   10563 | 2024-05-27 16:59:24 |         MASTER-SAAO | (08h 25m 05.25s , -10d 15m 57.2s) |   C |    60 | 19.2 |        
   10642 | 2024-05-27 17:00:43 |         MASTER-SAAO | (08h 33m 14.26s , -10d 17m 11.8s) |   C |    60 | 19.3 |        
   10803 | 2024-05-27 17:03:24 |         MASTER-SAAO | (08h 24m 52.36s , -14d 03m 20.3s) |   C |    60 | 19.2 |        
   10883 | 2024-05-27 17:04:44 |         MASTER-SAAO | (08h 43m 57.14s , -12d 11m 27.0s) |   C |    60 | 19.3 |        
   11042 | 2024-05-27 17:07:23 |         MASTER-SAAO | (08h 40m 33.16s , -10d 16m 51.0s) |   C |    60 | 19.4 |        
   11202 | 2024-05-27 17:10:03 |         MASTER-SAAO | (08h 28m 19.16s , -12d 10m 06.0s) |   C |    60 | 19.3 |        
   11282 | 2024-05-27 17:11:23 |         MASTER-SAAO | (08h 36m 32.47s , -12d 09m 07.5s) |   C |    60 | 19.4 |

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

GCN Circular #36550
R. Gupta (NASA/GSFC), F. Longo (University and INFN, Trieste), and A. Holzmann (DF, University of Buenos Aires, Argentina) report on behalf of the Fermi-LAT Collaboration:
At 14:03:51.50 on May, 27, 2024 Fermi-LAT detected high-energy emission from GRB 240527B which was also detected by Fermi-GBM (trigger 738511436 / 240527586, GCN 36546).
The best LAT on-ground location is found to be
RA, Dec = 128.10, -14.48 (J2000)
with an error radius of 0.19 deg (90 % containment, statistical error only).
This was 77 deg from the LAT boresight at the time of the trigger.
The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 0-3000 s after the GBM trigger is (6.2 +/- 3.0) E-7 ph/cm2/s. The estimated photon index above 100 MeV is - 1.6+/- 0.2.
The highest-energy photon is a 4.0 GeV event which is observed about 1200 seconds after the GBM trigger.
A Swift ToO has been approved.
The Fermi-LAT point of contact for this burst is Rahul Gupta ( rahul.gupta@nasa.gov).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #36553
C. Fletcher (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 14:03:51.50 UT on 27 May 2024, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 240527B (trigger 738511436/240527586). which was also detected by Fermi LAT (R. Gupta et al. 2024, GCN 36550). The Fermi GBM on-ground location (GCN 36546) is consistent with the Fermi LAT position.
The angle from the Fermi LAT boresight is 78 degrees.
The GBM light curve consists of multiple peaks with a duration (T90) of about 24.8 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+29.440 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.07 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 280 +/- 20 keV.
The event fluence (10-1000 keV) in this time interval is (1.46 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+14 s in the 10-1000 keV band is 10.9 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak= 201 +/- 20 keV, alpha = -0.95 +/- 0.05 and beta = -2.1 +/- 0.1.
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 #36558
J. D. Gropp (PSU), S. Dichiara (PSU), J.A. Kennea (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Fermi/LAT-detected burst GRB 240527B, collecting 5.2 ks of Photon Counting (PC) mode data between T0+27.3 ks and T0+135.5 ks.
Eight uncatalogued X-ray sources are detected, of which one ("Source 7") is above the RASS 3-sigma upper limit at this position and fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1624 s of PC mode data and 3 UVOT images, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 128.15387, -14.43738 which is equivalent to:
```
RA (J2000): 08h 32m 36.93s
Dec(J2000): -14d 26' 14.6"
```
with an uncertainty of 2.0 arcsec (radius, 90% confidence). This position is 4.0 arcmin from the Fermi/LAT position.
The light curve can be modelled with a power-law decay with a decay index of alpha=1.23 (+0.16, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.70 (+0.08, -0.06). The best-fitting absorption column is consistent with the Galactic value of 5.7 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.8 x 10^-11 (4.2 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     5.7 (+/-1.9) x 10^20 cm^-2
Galactic foreground: 5.7 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.70 (+0.08, -0.06)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00021694. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/00021694.
This circular is an official product of the Swift-XRT team.

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Jochen Greiner, last update: 29-May-2024 [Disclaimer]