Gamma-ray Burst 250330A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:07:51 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1299776,   Seg_Num: 0
GRB_RA:          252.790d {+16h 51m 10s} (J2000),
                 255.601d {+17h 02m 24s} (current),
                 247.436d {+16h 29m 45s} (1950)
GRB_DEC:         -86.870d {-86d 52' 11"} (J2000),
                 -86.908d {-86d 54' 29"} (current),
                 -86.775d {-86d 46' 29"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1163 [cnts]    Image_Peak=141 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   123     E_range: 25-100 keV
BKG_INTEN:       18792 [cnts]
BKG_TIME:        22044.66 SOD {06:07:24.66} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20764 TJD;    89 DOY;   25/03/30
GRB_TIME:        22058.16 SOD {06:07:38.16} UT
GRB_PHI:           3.63 [deg]
GRB_THETA:        17.21 [deg]
SOLN_STATUS:     0x20000003
RATE_SIGNIF:     22.53 [sigma]
IMAGE_SIGNIF:    10.82 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +2  +0  +0  +0  +9  +0 
SUN_POSTN:         9.00d {+00h 36m 01s}   +3.88d {+03d 52' 51"}
SUN_DIST:         95.10 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:       18.80d {+01h 15m 12s}  +10.19d {+10d 11' 15"}
MOON_DIST:       101.87 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      267.92,-63.56 [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 = 327.30,-8.61 [deg].  
COMMENTS:           
COMMENTS:        NOTE: This BAT event is temporally(0.0<100sec) coincident with the FERMI_GBM event (trignum=765007663).

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:08:00 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      49
TRIGGER_NUM:     765007663
GRB_RA:          271.250d {+18h 05m 00s} (J2000),
                 272.517d {+18h 10m 04s} (current),
                 268.739d {+17h 54m 57s} (1950)
GRB_DEC:         -81.533d {-81d 31' 59"} (J2000),
                 -81.529d {-81d 31' 42"} (current),
                 -81.533d {-81d 31' 59"} (1950)
GRB_ERROR:       7.08 [deg radius, statistical plus systematic]
GRB_INTEN:       239 [cnts/sec]
DATA_SIGNIF:     17.50 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        20764 TJD;    89 DOY;   25/03/30
GRB_TIME:        22058.42 SOD {06:07:38.42} UT
GRB_PHI:         118.00 [deg]
GRB_THETA:        50.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      1.17
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      98%  GRB
2nd_MOST_LIKELY:   1%  Generic SGR
DETECTORS:       1,0,0, 0,0,0, 0,0,0, 1,0,0, 0,0,
SUN_POSTN:         9.00d {+00h 36m 01s}   +3.88d {+03d 52' 51"}
SUN_DIST:         94.79 [deg]   Sun_angle= 6.4 [hr] (West of Sun)
MOON_POSTN:       18.80d {+01h 15m 12s}  +10.19d {+10d 11' 17"}
MOON_DIST:       102.45 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      312.10,-25.13 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      270.35,-58.10 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_lc_medres34_bn250330255.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 110.32,-4.20 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1299776).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:08:15 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      60
TRIGGER_NUM:     765007663
GRB_RA:          238.630d {+15h 54m 31s} (J2000),
                 239.395d {+15h 57m 35s} (current),
                 237.132d {+15h 48m 32s} (1950)
GRB_DEC:         -74.700d {-74d 42' 00"} (J2000),
                 -74.772d {-74d 46' 19"} (current),
                 -74.552d {-74d 33' 06"} (1950)
GRB_ERROR:       3.78 [deg radius, statistical only]
DATA_SIGNIF:     20.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20764 TJD;    89 DOY;   25/03/30
GRB_TIME:        22058.42 SOD {06:07:38.42} UT
GRB_PHI:         124.00 [deg]
GRB_THETA:        58.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:         9.01d {+00h 36m 01s}   +3.88d {+03d 52' 51"}
SUN_DIST:        103.44 [deg]   Sun_angle= 8.6 [hr] (West of Sun)
MOON_POSTN:       18.80d {+01h 15m 13s}  +10.19d {+10d 11' 22"}
MOON_DIST:       111.53 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      314.28,-16.02 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      256.90,-52.69 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_lc_medres34_bn250330255.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_765007663.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1299776).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:08:50 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      0
TRIGGER_NUM:     765007663
GRB_RA:          238.820d {+15h 55m 17s} (J2000),
                 239.585d {+15h 58m 20s} (current),
                 237.323d {+15h 49m 17s} (1950)
GRB_DEC:         -74.660d {-74d 39' 35"} (J2000),
                 -74.732d {-74d 43' 54"} (current),
                 -74.513d {-74d 30' 45"} (1950)
GRB_ERROR:       3.28 [deg radius, statistical only]
DATA_SIGNIF:     20.40 [sigma]
DATA_INTERVAL:   4.096 [sec]
GRB_DATE:        20764 TJD;    89 DOY;   25/03/30
GRB_TIME:        22058.42 SOD {06:07:38.42} UT
GRB_PHI:         124.00 [deg]
GRB_THETA:        58.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:         9.01d {+00h 36m 01s}   +3.88d {+03d 52' 52"}
SUN_DIST:        103.42 [deg]   Sun_angle= 8.6 [hr] (West of Sun)
MOON_POSTN:       18.81d {+01h 15m 14s}  +10.19d {+10d 11' 32"}
MOON_DIST:       111.53 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      314.34,-16.03 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      256.96,-52.63 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_lc_medres34_bn250330255.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_765007663.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        In the LAT Field-of-view.  
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(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1299776).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:16:59 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     765007663
GRB_RA:          241.960d {+16h 07m 50s} (J2000),
                 242.708d {+16h 10m 50s} (current),
                 240.492d {+16h 01m 58s} (1950)
GRB_DEC:         -73.630d {-73d 37' 47"} (J2000),
                 -73.695d {-73d 41' 42"} (current),
                 -73.496d {-73d 29' 44"} (1950)
GRB_ERROR:       4.52 [deg radius, statistical only]
GRB_DATE:        20764 TJD;    89 DOY;   25/03/30
GRB_TIME:        22058.42 SOD {06:07:38.42} UT
GRB_PHI:         123.00 [deg]
GRB_THETA:        59.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:         9.01d {+00h 36m 03s}   +3.88d {+03d 52' 60"}
SUN_DIST:        103.35 [deg]   Sun_angle= 8.4 [hr] (West of Sun)
MOON_POSTN:       18.89d {+01h 15m 33s}  +10.23d {+10d 13' 51"}
MOON_DIST:       111.70 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      315.73,-15.86 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      257.74,-51.38 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_lc_medres34_bn250330255.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_locplot_all_bn250330255.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        In the LAT Field-of-view.  
COMMENTS:        This is likely a Long GRB.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(0.0<100sec) coincident with the SWIFT_BAT event (trignum=1299776).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:09:27 UT
NOTICE_TYPE:     Swift-XRT Image
TRIGGER_NUM:     1299776,   Seg_Num: 0
GRB_RA:          252.6043d {+16h 50m 25.0s} (J2000),
                 255.4265d {+17h 01m 42.3s} (current),
                 247.2325d {+16h 28m 55.8s} (1950)
GRB_DEC:         -86.8862d {-86d 53' 10.3"} (J2000),
                 -86.9249d {-86d 55' 29.7"} (current),
                 -86.7903d {-86d 47' 24.9"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       40 [cnts]
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  22131.34 SOD {06:08:51.34} UT,   73.2 [sec] since BAT Trigger Time
CENTROID_X:      310.23,  raw= 310  [pixels]
CENTROID_Y:      268.67,  raw= 269  [pixels]
ROLL:            116.03 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -70.77
GRB_POS_XRT_Z:   -3.21
IMAGE_URL:       sw01299776000msxps_rw.img
SUN_POSTN:         9.01d {+00h 36m 01s}   +3.88d {+03d 52' 53"}
SUN_DIST:         95.11 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:       18.81d {+01h 15m 15s}  +10.20d {+10d 11' 42"}
MOON_DIST:       101.88 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.91,-25.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      267.91,-63.57 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:09:29 UT
NOTICE_TYPE:     Swift-XRT Processed Image
TRIGGER_NUM:     1299776,   Seg_Num: 0
GRB_RA:          252.6043d {+16h 50m 25.0s} (J2000),
                 255.4265d {+17h 01m 42.3s} (current),
                 247.2325d {+16h 28m 55.8s} (1950)
GRB_DEC:         -86.8862d {-86d 53' 10.3"} (J2000),
                 -86.9249d {-86d 55' 29.7"} (current),
                 -86.7903d {-86d 47' 24.9"} (1950)
GRB_ERROR:       5.0 [arcsec, radius, statistical plus systematic]
GRB_INTEN:       40 [cnts]
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  22131.34 SOD {06:08:51.34} UT,   73.2 [sec] since BAT Trigger Time
CENTROID_X:      310.23,  raw= 310  [pixels]
CENTROID_Y:      268.67,  raw= 269  [pixels]
ROLL:            116.03 [deg]
GAIN:            1
MODE:            3, Long Image mode
WAVEFORM:        134
EXPO_TIME:       2.50 [sec]
GRB_POS_XRT_Y:   -70.77
GRB_POS_XRT_Z:   -3.21
IMAGE_URL:       sw01299776000msxps_rw.img
SUN_POSTN:         9.01d {+00h 36m 01s}   +3.88d {+03d 52' 53"}
SUN_DIST:         95.11 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:       18.81d {+01h 15m 15s}  +10.20d {+10d 11' 43"}
MOON_DIST:       101.88 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.91,-25.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      267.91,-63.57 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Processed Image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:09:17 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1299776,   Seg_Num: 0
GRB_RA:          252.6043d {+16h 50m 25.03s} (J2000),
                 255.4265d {+17h 01m 42.36s} (current),
                 247.2325d {+16h 28m 55.80s} (1950)
GRB_DEC:         -86.8862d {-86d 53' 10.3"} (J2000),
                 -86.9249d {-86d 55' 29.7"} (current),
                 -86.7903d {-86d 47' 24.9"} (1950)
GRB_ERROR:       5.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.46e-09 [erg/cm2/sec]
GRB_SIGNIF:      6.32 [sigma]
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  22131.34 SOD {06:08:51.34} UT,   73.2 [sec] since BAT Trigger Time
TAM[0-3]:        327.68 237.12 261.64 243.80
AMPLIFIER:       2
WAVEFORM:        134
SUN_POSTN:         9.01d {+00h 36m 01s}   +3.88d {+03d 52' 52"}
SUN_DIST:         95.11 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:       18.81d {+01h 15m 15s}  +10.19d {+10d 11' 39"}
MOON_DIST:       101.88 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.91,-25.53 [deg] galactic lon,lat of the burst
ECL_COORDS:      267.91,-63.57 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        The XRT position is 1.13 arcmin from the BAT position.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 06:11:21 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1299776,   Seg_Num: 0
GRB_RA:          252.790d {+16h 51m 10s} (J2000),
                 255.601d {+17h 02m 24s} (current),
                 247.436d {+16h 29m 45s} (1950)
GRB_DEC:         -86.870d {-86d 52' 11"} (J2000),
                 -86.908d {-86d 54' 29"} (current),
                 -86.775d {-86d 46' 29"} (1950)
GRB_DATE:        20764 TJD;    89 DOY;   25/03/30
GRB_TIME:        22058.16 SOD {06:07:38.16} UT
TRIGGER_INDEX:   123
GRB_PHI:           3.63 [deg]
GRB_THETA:        17.21 [deg]
DELTA_TIME:      -70.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     22.53 [sigma]
IMAGE_SIGNIF:    10.82 [sigma]
LC_URL:          sw01299776000msb.lc
SUN_POSTN:         9.01d {+00h 36m 02s}   +3.88d {+03d 52' 54"}
SUN_DIST:         95.10 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:       18.83d {+01h 15m 20s}  +10.20d {+10d 12' 15"}
MOON_DIST:       101.89 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.53 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      267.92,-63.56 [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 = 327.30,-8.61 [deg].

GCN Circular #39937
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-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 GRB250330.26 (trigger No 1299776,16h 51m 09.60s , -86d 52m 12.0s, R=0.05) errorbox 47 sec after notice time and 74 sec after trigger time at 2025-03-30 06:08:53 UT, with upper limit up to 19.1 mag. The observations began at zenith distance = 56 deg. The sun altitude is -55.5 deg.
The galactic latitude b = -26 deg., longitude l = 306 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2827980
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

      80 |         MASTER-OAFA |   C |    10 | 18.6 |        
     115 |         MASTER-OAFA |   C |    20 | 19.1 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #39938
S. B. Cenko (GSFC), K. L. Page (U Leicester) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 06:07:38 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250330A (trigger=1299776). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 252.790, -86.870 which is
```
   RA(J2000) = 16h 51m 10s
   Dec(J2000) = -86d 52' 11"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single peak structure with a duration of about 10 sec. The peak count rate was ~5800 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 06:08:51.3 UT, 73.2 seconds after the BAT trigger. Due to the proximity of Swift to the SAA, XRT centroided on a cosmic ray. Given the short visibility window, no other data are available at this time.
UVOT data are not available at this time.
Although this trigger occurred while Swift was close to the SAA, the BAT light-curve shows a definite peak, and Fermi-GBM also triggered at the same time.
Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). 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:     Sun 30 Mar 25 07:13:28 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1299776,   Seg_Num: 0
POINT_RA:        253.122d {+16h 52m 29s} (J2000)
POINT_DEC:       -86.885d {-86d 53' 06"} (J2000)
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  26000.14 SOD {07:13:20.14} UT,   3942.0 [sec] since BAT Trigger Time
COUNTS:          2    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 07:16:10 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1299776,   Seg_Num: 0
POINT_RA:        253.120d {+16h 52m 29s} (J2000)
POINT_DEC:       -86.885d {-86d 53' 07"} (J2000)
POINT_ROLL:      115.706d
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  26002.30 SOD {07:13:22.30} UT,   3944.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.616
N_STARS:         96
X_OFFSET:        309 [pixels]
Y_OFFSET:        589 [pixels]
X_MAX:           1268 [pixels]
Y_MAX:           1548 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01299776000msufc3944.fits
SUN_POSTN:         9.05d {+00h 36m 12s}   +3.90d {+03d 53' 57"}
SUN_DIST:         95.10 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:       19.45d {+01h 17m 48s}  +10.51d {+10d 30' 39"}
MOON_DIST:       102.20 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      267.97,-63.57 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 30 Mar 25 07:16:27 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1299776,   Seg_Num: 0
POINT_RA:        253.120d {+16h 52m 29s} (J2000)
POINT_DEC:       -86.885d {-86d 53' 07"} (J2000)
POINT_ROLL:      115.706d
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  26002.30 SOD {07:13:22.30} UT,   3944.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        1.616
N_STARS:         96
X_OFFSET:        309 [pixels]
Y_OFFSET:        589 [pixels]
X_MAX:           1268 [pixels]
Y_MAX:           1548 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    5
SL_URL:          sw01299776000msufc3944.fits
SUN_POSTN:         9.05d {+00h 36m 12s}   +3.90d {+03d 53' 58"}
SUN_DIST:         95.10 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:       19.45d {+01h 17m 49s}  +10.51d {+10d 30' 44"}
MOON_DIST:       102.20 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      267.97,-63.57 [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 30 Mar 25 07:17:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1299776,   Seg_Num: 0
POINT_RA:        253.120d {+16h 52m 29s} (J2000)
POINT_DEC:       -86.885d {-86d 53' 07"} (J2000)
ROLL:            115.706d
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  26002.30 SOD {07:13:22.30} UT,   3944.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     765011637
X_OFFSET:        628 [pixels]
Y_OFFSET:        908 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       788
Y_GRB_POS:       1068
BINNING_INDEX:   1
IM_URL:          sw01299776000msuni3980.fits
SUN_POSTN:         9.05d {+00h 36m 12s}   +3.90d {+03d 53' 59"}
SUN_DIST:         95.10 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:       19.46d {+01h 17m 52s}  +10.52d {+10d 31' 04"}
MOON_DIST:       102.21 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      267.97,-63.57 [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 30 Mar 25 07:17:54 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1299776,   Seg_Num: 0
POINT_RA:        253.120d {+16h 52m 29s} (J2000)
POINT_DEC:       -86.885d {-86d 53' 07"} (J2000)
ROLL:            115.706d
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  26002.30 SOD {07:13:22.30} UT,   3944.1 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     765011637
X_OFFSET:        628 [pixels]
Y_OFFSET:        908 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       788
Y_GRB_POS:       1068
BINNING_INDEX:   1
IM_URL:          sw01299776000msuni3980.fits
SUN_POSTN:         9.05d {+00h 36m 12s}   +3.90d {+03d 53' 59"}
SUN_DIST:         95.10 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:       19.47d {+01h 17m 52s}  +10.52d {+10d 31' 08"}
MOON_DIST:       102.21 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.55 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      267.97,-63.57 [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 30 Mar 25 07:44:41 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1299776,   Seg_Num: 0
GRB_RA:          252.9515d {+16h 51m 48.36s} (J2000),
                 255.7724d {+17h 03m 05.38s} (current),
                 247.5778d {+16h 30m 18.67s} (1950)
GRB_DEC:         -86.8797d {-86d 52' 46.9"} (J2000),
                 -86.9176d {-86d 55' 03.4"} (current),
                 -86.7853d {-86d 47' 07.2"} (1950)
GRB_ERROR:       3.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20764 TJD;    89 DOY;   25/03/30
IMG_START_TIME:  26020.00 SOD {07:13:40.00} UT,   3961.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:         9.07d {+00h 36m 16s}   +3.91d {+03d 54' 25"}
SUN_DIST:         95.12 [deg]   Sun_angle= 7.6 [hr] (West of Sun)
MOON_POSTN:       19.72d {+01h 18m 54s}  +10.65d {+10d 38' 43"}
MOON_DIST:       102.36 [deg]
MOON_ILLUM:      1 [%]
GAL_COORDS:      305.93,-25.54 [deg] galactic lon,lat of the burst
ECL_COORDS:      267.95,-63.56 [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:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN Circular #39940
K.L. Page and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team:
Because of the location of Swift with respect to the South Atlantic Anomaly at the time of the burst, XRT began collecting Photon Counting mode data for GRB 250330A (GCN Circ. 39938) around 4 ks after the trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec = 252.9515, -86.87972 which is equivalent to
```
RA (J2000): 16h 51m 48.36s
Dec (J2000): -86d 52' 47.0"
```
with an uncertainty of 3.9 arcsec (radius, 90% confidence). This is 47 arcseconds from the BAT position, inside the BAT error circle.
This circular is an official product of the Swift-XRT team.
GCN Circular #39941
Rosa Becerra (U Rome), Eleonora Troja (U Rome), Muskan Yadav (U Rome), Roberto Ricci (U Rome) report on behalf of the ERC BHianca team:
We observed the field of GRB 250330A (Cenko et al., GCN 39938) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began at T+1.25 hours after the trigger and were carried out in the R filter at an average seeing of 0.7" and airmass about 2.2.
Image subtraction against the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et al., 2024) shows no new uncataloged source down to r~21.5 AB. Several fainter objects are visible within the XRT position (Page et al., GCN 39940), however, additional observations are required to assess their variability
We thank the staff at the VLT for the rapid execution of these observations.
GCN Circular #39944
The Fermi GBM team reports the detection of a likely LONG GRB
"At 06:07:38.42 UT on 30 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250330A (trigger 765007663/250330255).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 254.96, Dec = -66.02 (J2000 degrees, equivalent to J2000 16h 51m, -86d 52'), with a statistical uncertainty of 6.9 degrees. This localization is consistent with Swift-BAT location (Cenko et al. 2025, GCN 39938) and Swift-XRT (Page et al. 2025, 39940).
The angle from the Fermi LAT boresight is 46 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_skymap_all_bn250330255.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/bn250330255/quicklook/glg_healpix_all_bn250330255.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250330255/quicklook/glg_lc_medres34_bn250330255.gif"
GCN Circular #39947
J.P. Osborne (U. Leicester), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), D.N. Burrows (PSU), M. A. Williams (PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the Swift-BAT-detected burst GRB 250330A. We searched for X-ray sources in 1.4 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 5.1 ks, obtained between T0+3.9 ks and T0+28.0 ks.
Two uncatalogued X-ray sources are detected within the estimated 3-sigma Swift-BAT error region (296 arcsec), of which one ("Source 1") is above the LSXPS 3-sigma upper limit at this position and fading with >3-sigma significance, and is therefore likely the GRB afterglow. Using 1474 s of PC mode data and 4 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 = 252.94482, -86.88053 which is equivalent to:
```
RA (J2000): 16h 51m 46.76s
Dec(J2000): -86d 52' 49.9"
```
with an uncertainty of 2.3 arcsec (radius, 90% confidence). This position is 48 arcsec from the Swift-BAT position.
The light curve can be modelled with a power-law decay with a decay index of alpha=1.01 (+0.15, -0.14).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.3 (+0.4, -0.3). The best-fitting absorption column is 4.9 (+1.9, -1.5) x 10^21 cm^-2, in excess of the Galactic value of 1.2 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 3.6 x 10^-11 (7.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     4.9 (+1.9, -1.5) x 10^21 cm^-2
Galactic foreground: 1.2 x 10^21 cm^-2
Excess significance: 3.9 sigma
Photon index:	     2.3 (+0.4, -0.3)
```
If the light curve continues to decay with a power-law decay index of 1.01, the count rate at T+24 hours will be 7.8 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x 10^-13 (5.4 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/01299776. The results of the full analysis of the XRT observations are available at https://www.swift.ac.uk/ToO_GRBs/01299776.
This circular is an official product of the Swift-XRT team.
GCN Circular #39948
M. H. Siegel (PSU) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250330A 3944 s after the BAT trigger (Cenko et al., GCN Circ. 39938). No optical afterglow consistent with the XRT position (Osborne et al., GCN Circ. 39947) 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          3944         4094          147         >21.2
white             3944         4094          147         >21.2
v                 4101         4300          197         >20.0
b                 4921         5109          185         >20.9
u                 4716         4915          197         >20.0
w1                4511         4711          197         >21.3
m2                4306         4505          197         >19.8
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.147 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #39949
I. Perez-Garcia, A. J. Castro-Tirado, E. Fernandez-Garcia, S.-Y. Wu, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), C. Perez del Pulgar (Univ. de Malaga), G. Garcia-Segura (Inst. de Astronomia, UNAM), M. Gritsevich (Univ. of Helsinki), D. R. Xiong (Yunnan Observatories of CAS), Y.-D. Hu (GuangXi Univ.), B.-B. Zhang (Nanjing Univ.) and A. Maury (Space, San Pedro de Atacama), on behalf of a larger collaboration, report:
Following the detection of GRB 250330A by Swift/BAT (Cenko et al., GCNC [39938](https://gcn.nasa.gov/circulars/39938)) and Fermi (Fermi GRB Team, GCNC [39944](https://gcn.nasa.gov/circulars/39944)), the 0.6m BOOTES-7 robotic telescope at San Pedro de Atacama (Chile) responded to the alert on Nov. 9, 06:08:48 UT (i.e. 57s after trigger, and 70s after the event). Within the reported Swift/XRT error circle (Page et al., GCNC [39940](https://gcn.nasa.gov/circulars/39940)) , no optical transient is detected down to 17.6 mag (clear filter). On a coadd (620s) of images at 06:31:17 UT (mid exposure time; i.e. 23.8 min post burst), nothing is detected down to 19.3 mag, in agreement with the deeper VLT/FORS2 observations taken later on (Becerra et al., GCNC [39941](https://gcn.nasa.gov/circulars/39941)).
We thank the staff at San Pedro de Atacama Celestial Observations for their excellent support.

GCN Circular #39950
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory)
MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250330A ( Fermi GBM team, GCN 39944) errorbox 41642 sec after notice time and 41678 sec after trigger time at 2025-03-30 17:42:16 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 69 deg. The sun altitude is -14.6 deg.
The galactic latitude b = -16 deg., longitude l = 316 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2828018
We obtain a following upper limits.

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

   41709 | 2025-03-30 17:42:16 |         MASTER-SAAO | (16h 01m 09.95s , -72d 45m 24.7s) |   C |    60 | 18.1 |        
   41788 | 2025-03-30 17:43:36 |         MASTER-SAAO | (16h 28m 26.03s , -72d 45m 15.7s) |   C |    60 | 18.2 |        
   41868 | 2025-03-30 17:44:56 |         MASTER-SAAO | (16h 02m 18.38s , -74d 39m 19.9s) |   C |    60 | 18.0 |        
   41947 | 2025-03-30 17:46:15 |         MASTER-SAAO | (16h 32m 49.13s , -74d 37m 47.3s) |   C |    60 | 18.3 |        
   42026 | 2025-03-30 17:47:34 |         MASTER-SAAO | (15h 04m 24.83s , -74d 37m 14.9s) |   C |    60 | 18.4 |        
   42106 | 2025-03-30 17:48:54 |         MASTER-SAAO | (15h 34m 57.62s , -74d 38m 25.7s) |   C |    60 | 18.4 |        
   42186 | 2025-03-30 17:50:14 |         MASTER-SAAO | (15h 09m 38.19s , -72d 45m 00.7s) |   C |    60 | 18.2 |        
   42265 | 2025-03-30 17:51:33 |         MASTER-SAAO | (15h 36m 45.01s , -72d 44m 01.7s) |   C |    60 | 18.3 |        
   42345 | 2025-03-30 17:52:52 |         MASTER-SAAO | (16h 01m 11.29s , -72d 45m 24.8s) |   C |    60 | 18.2 |        
   42424 | 2025-03-30 17:54:12 |         MASTER-SAAO | (16h 28m 23.83s , -72d 44m 12.1s) |   C |    60 | 18.2 |        
   42866 | 2025-03-30 18:01:34 |         MASTER-SAAO | (16h 02m 13.55s , -74d 39m 54.2s) |   C |    60 | 17.9 |        
   42945 | 2025-03-30 18:02:53 |         MASTER-SAAO | (16h 32m 48.33s , -74d 40m 05.2s) |   C |    60 | 18.3 |        
   43025 | 2025-03-30 18:04:13 |         MASTER-SAAO | (15h 04m 23.51s , -74d 37m 45.9s) |   C |    60 | 18.4 |        
   43104 | 2025-03-30 18:05:32 |         MASTER-SAAO | (15h 34m 50.67s , -74d 39m 22.5s) |   C |    60 | 18.5 |        
   43184 | 2025-03-30 18:06:52 |         MASTER-SAAO | (15h 09m 34.64s , -72d 44m 00.2s) |   C |    60 | 18.2 |        
   43263 | 2025-03-30 18:08:11 |         MASTER-SAAO | (15h 36m 38.09s , -72d 44m 59.8s) |   C |    60 | 18.3 |        
   43343 | 2025-03-30 18:09:31 |         MASTER-SAAO | (16h 01m 06.13s , -72d 44m 09.8s) |   C |    60 | 18.2 |        
   45719 | 2025-03-30 18:49:07 |         MASTER-SAAO | (16h 28m 13.93s , -72d 47m 17.6s) |   C |    60 | 18.2 |        
   45798 | 2025-03-30 18:50:26 |         MASTER-SAAO | (16h 02m 10.31s , -74d 39m 28.3s) |   C |    60 | 18.1 |        
   45878 | 2025-03-30 18:51:46 |         MASTER-SAAO | (16h 32m 34.04s , -74d 40m 31.3s) |   C |    60 | 18.3 |        
   46778 | 2025-03-30 19:06:46 |         MASTER-SAAO | (15h 04m 04.80s , -74d 39m 00.1s) |   C |    60 | 18.5 |        
   46858 | 2025-03-30 19:08:05 |         MASTER-SAAO | (15h 34m 34.17s , -74d 41m 15.3s) |   C |    60 | 18.4 |

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

GCN Circular #39957
Z.M. Wang, A. Li (BNU), L.P. Xin, H.L. Li, Y. L. Qiu, C. Wu, Z.H. Yao, Y. Xu, P.P. Zhang, J. Wang, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei(NAOC) report on behalf of the SVOM/VT team:
SVOM performed two Target of Opportunity observations of GRB 250330A (Cenko et al., GCN 39938; Pathak, GCN 39944; Osborne et al., GCN 39947) in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously， starting at 2025-03-30T09:17:44 UT, and 2025-03-30T12:40:58 UT, respectively.
No sources were detected in the stacked images within the XRT source position (Page, GCN 39940).
The 3 sigma limits in VT_R is 21.7 mag (AB) with the exposure time of 3 x 100s at the medium time of 3.2 hours after the Swift BAT trigger, and 23.0 mag with the exposure of 12*120s, at the medium time of 6.8 hours after the burst.
This result is consistent with the reports (Becerra, GCN 39941; Siegel et al., GCN 39948; Perez-Garcia et al., GCN 39949; Lipunov et al., GCN 39950).
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 #39964
U. Pathak (IITB), R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 06:07:38.42 UT on 30 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250330A (trigger 765007663/250330255). which was also detected by Swift-BAT (Cenko et al. 2025, GCN 39938). The afterglow has been detected by Swift-XRT (Osborne et al. 2025, GCN 39947). The Fermi GBM Final Localization (GCN 39944) is consistent with the Swift-BAT and Swift-XRT positions (Page et al. 2025, GCN 39940).
The angle from the Fermi LAT boresight is 46 degrees.
The GBM light curve consists of a single emission episode with a duration (T90) of about 4.8 s (50-300 keV). The time-averaged spectrum from T0-0.6 to T0+6.53 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 95 +/- 8 keV.
The event fluence (10-1000 keV) in this time interval is (1.50 +/- 0.08)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.26 s in the 10-1000 keV band is 6.5 +/- 0.3 ph/s/cm^2.
A Band function fits the spectrum equally well with Epeak= 86 +/- 10 keV, alpha = -0.8 +/- 0.2 and beta = -2.7 +/- 0.4.
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 #39970
Rosa L. Becerra (U Rome), Yu-Han Yang (U Rome), Simone Dichiara (PSU), Muskan Yadav (U Rome), Eleonora Troja (U Rome), Lei Hu (CMU) and Roberto Ricci (U Rome) report on behalf of the ERC BHianca team:
We reobserved the field of GRB 250330A (Cenko et al., GCN 39938) with the FORS2 imager on the ESO VLT UT1 (Antu). Observations began at T+19.8 hours after the trigger and were carried out in the R filter at an average seeing of 1.0" and airmass about 2.5.
A comparison to our first epoch (Becerra et al., GCN 39941) reveals a fading source within the XRT enhanced position (Evans et al., GCN 39947), located at RA, Dec (J2000) = 16:51:47.01, -86:52:51.85.
We estimate a preliminary magnitude of R~23.2 AB mag at 1.25 h post-trigger, calibrated using nearby stars from the SkyMapper Southern Survey (SMSS) Fourth Data Release (DR4) catalog (Onken et al., 2024) and not corrected for Galactic extinction.
We thank the staff at the VLT for the rapid execution of these observations.
GCN Circular #40055
H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), R. Gupta (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team):
Using the data set from T-137 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250330A (trigger #1299776) (Cenko, et al., GCN Circ. 39938). The BAT ground-calculated position is RA, Dec = 252.685, -86.875 deg which is
```
   RA(J2000)  =  16h 50m 44.5s
   Dec(J2000) = -86d 52' 29.6"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 98%.
The mask-weighted light curve shows a single well defined fast-rise exponential- decay pulse shape. the T90 (15-350 keV) is 11.27 +- 2.53 sec (estimated error including systematics).
The time-averaged spectrum from T-0.16 to T+14.33 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.72 +- 0.10. The fluence in the 15-150 keV band is 9.2 +- 0.6 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+0.26 sec in the 15-150 keV band is 4.0 +- 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/1299776

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Jochen Greiner, last update: 04-Apr-2025 [Disclaimer]