Gamma-ray Burst 230228A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:51:11 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1156572,   Seg_Num: 0
GRB_RA:           18.403d {+01h 13m 37s} (J2000),
                  18.740d {+01h 14m 58s} (current),
                  17.678d {+01h 10m 43s} (1950)
GRB_DEC:         +44.489d {+44d 29' 19"} (J2000),
                 +44.611d {+44d 36' 39"} (current),
                 +44.224d {+44d 13' 26"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1935 [cnts]    Image_Peak=210 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   146     E_range: 25-100 keV
BKG_INTEN:       8315 [cnts]
BKG_TIME:        21033.16 SOD {05:50:33.16} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20003 TJD;    59 DOY;   23/02/28
GRB_TIME:        21050.25 SOD {05:50:50.25} UT
GRB_PHI:         177.68 [deg]
GRB_THETA:        30.83 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.03 [sigma]
IMAGE_SIGNIF:    11.96 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +2  +1  +0  +0 -46  +0 
SUN_POSTN:       340.95d {+22h 43m 48s}   -8.05d {-08d 03' 09"}
SUN_DIST:         62.70 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.33d {+05h 13m 19s}  +26.53d {+26d 31' 35"}
MOON_DIST:        50.50 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.09,-18.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       35.64, 33.60 [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 = 91.38,8.91 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 28 Feb 23 17:05:50 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     699256256
GRB_RA:           18.970d {+01h 15m 53s} (J2000),
                  19.312d {+01h 17m 15s} (current),
                  18.235d {+01h 12m 56s} (1950)
GRB_DEC:         +46.800d {+46d 47' 60"} (J2000),
                 +46.922d {+46d 55' 18"} (current),
                 +46.536d {+46d 32' 10"} (1950)
GRB_ERROR:       9.44 [deg radius, statistical only]
GRB_DATE:        20003 TJD;    59 DOY;   23/02/28
GRB_TIME:        21051.19 SOD {05:50:51.19} UT
GRB_PHI:         307.00 [deg]
GRB_THETA:       116.00 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:       341.39d {+22h 45m 33s}   -7.88d {-07d 52' 32"}
SUN_DIST:         64.30 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       84.61d {+05h 38m 26s}  +27.21d {+27d 12' 33"}
MOON_DIST:        54.00 [deg]
MOON_ILLUM:      63 [%]
GAL_COORDS:      127.28,-15.87 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       37.35, 35.47 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230228244/quicklook/glg_lc_medres34_bn230228244.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230228244/quicklook/glg_locplot_all_bn230228244.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice has human-in-the-loop processing.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(1.0<100sec) coincident with the SWIFT_BAT event (trignum=1156572).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:52:59 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.422d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 39"} (J2000)
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21169.24 SOD {05:52:49.24} UT,   119.0 [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:     Tue 28 Feb 23 05:54:28 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1156572,   Seg_Num: 0
GRB_RA:           18.403d {+01h 13m 37s} (J2000),
                  18.740d {+01h 14m 58s} (current),
                  17.678d {+01h 10m 43s} (1950)
GRB_DEC:         +44.489d {+44d 29' 19"} (J2000),
                 +44.611d {+44d 36' 39"} (current),
                 +44.224d {+44d 13' 26"} (1950)
GRB_DATE:        20003 TJD;    59 DOY;   23/02/28
GRB_TIME:        21050.25 SOD {05:50:50.25} UT
TRIGGER_INDEX:   146
GRB_PHI:         177.68 [deg]
GRB_THETA:        30.83 [deg]
DELTA_TIME:      51.00 [sec]
TRIGGER_DUR:     1.024 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     25.03 [sigma]
IMAGE_SIGNIF:    11.96 [sigma]
LC_URL:          sw01156572000msb.lc
SUN_POSTN:       340.95d {+22h 43m 48s}   -8.05d {-08d 03' 06"}
SUN_DIST:         62.70 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.36d {+05h 13m 27s}  +26.53d {+26d 31' 49"}
MOON_DIST:        50.52 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.09,-18.20 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       35.64, 33.60 [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 = 91.38,8.91 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:56:10 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.422d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 38"} (J2000)
POINT_ROLL:      222.791d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21172.14 SOD {05:52:52.14} UT,   121.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.426
N_STARS:         142
X_OFFSET:        615 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1574 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw01156572000msufc0121.fits
SUN_POSTN:       340.95d {+22h 43m 49s}   -8.05d {-08d 03' 05"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.38d {+05h 13m 30s}  +26.53d {+26d 31' 57"}
MOON_DIST:        50.52 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:56:26 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.422d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 38"} (J2000)
POINT_ROLL:      222.791d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21172.14 SOD {05:52:52.14} UT,   121.9 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        4.426
N_STARS:         142
X_OFFSET:        615 [pixels]
Y_OFFSET:        430 [pixels]
X_MAX:           1574 [pixels]
Y_MAX:           1389 [pixels]
DET_THRESH:      18
PHOTO_THRESH:    10
SL_URL:          sw01156572000msufc0121.fits
SUN_POSTN:       340.95d {+22h 43m 49s}   -8.05d {-08d 03' 04"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.38d {+05h 13m 31s}  +26.53d {+26d 31' 58"}
MOON_DIST:        50.52 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:57:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.422d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 38"} (J2000)
ROLL:            222.791d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21172.14 SOD {05:52:52.14} UT,   121.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     699256402
X_OFFSET:        934 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1094
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw01156572000msuni0152.fits
SUN_POSTN:       340.95d {+22h 43m 49s}   -8.05d {-08d 03' 03"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.39d {+05h 13m 34s}  +26.53d {+26d 32' 03"}
MOON_DIST:        50.53 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:57:53 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.422d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 38"} (J2000)
ROLL:            222.791d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21172.14 SOD {05:52:52.14} UT,   121.9 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     699256402
X_OFFSET:        934 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1094
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw01156572000msuni0152.fits
SUN_POSTN:       340.95d {+22h 43m 49s}   -8.05d {-08d 03' 03"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.39d {+05h 13m 34s}  +26.53d {+26d 32' 04"}
MOON_DIST:        50.53 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 05:57:20 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1156572,   Seg_Num: 0
GRB_RA:           18.3777d {+01h 13m 30.64s} (J2000),
                  18.7148d {+01h 14m 51.55s} (current),
                  17.6530d {+01h 10m 36.72s} (1950)
GRB_DEC:         +44.4833d {+44d 28' 59.8"} (J2000),
                 +44.6055d {+44d 36' 19.9"} (current),
                 +44.2185d {+44d 13' 06.7"} (1950)
GRB_ERROR:       3.8 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21177.00 SOD {05:52:57.00} UT,   126.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       340.95d {+22h 43m 49s}   -8.05d {-08d 03' 04"}
SUN_DIST:         62.68 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.39d {+05h 13m 33s}  +26.53d {+26d 32' 02"}
MOON_DIST:        50.56 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.07,-18.21 [deg] galactic lon,lat of the burst
ECL_COORDS:       35.62, 33.60 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:04:00 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
POINT_ROLL:      222.789d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21385.36 SOD {05:56:25.36} UT,   335.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.093
N_STARS:         190
X_OFFSET:        375 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1814 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw01156572000msufc0335.fits
SUN_POSTN:       340.96d {+22h 43m 50s}   -8.05d {-08d 02' 57"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.45d {+05h 13m 48s}  +26.54d {+26d 32' 31"}
MOON_DIST:        50.56 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN Circular #33378
S. Dichiara (PSU), J.D. Gropp (PSU), D. M. Palmer (LANL) and T. M. Parsotan (GSFC/UMBC/CRESSTII) report on behalf of the Neil Gehrels Swift Observatory Team:
At 05:50:50 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230228A (trigger=1156572). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 18.403, +44.489 which is
```
   RA(J2000) = 01h 13m 37s
   Dec(J2000) = +44d 29' 19"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single symmetrical peak structure with a duration of about 1.5 sec. The peak count rate was ~2000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 05:52:49.2 UT, 119.0 seconds after the BAT trigger. Using promptly downlinked data we find a fading, uncatalogued X-ray source located at RA, Dec 18.37776, 44.48321 which is equivalent to:
```
   RA(J2000)  = 01h 13m 30.66s
   Dec(J2000) = +44d 28' 59.6"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 68 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 consistent with the Galactic value of 9.72 x 10^20 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 122 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.085.
Burst Advocate for this burst is S. Dichiara (simonedichiara55 AT gmail.com). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:04:13 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
POINT_ROLL:      222.789d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21385.36 SOD {05:56:25.36} UT,   335.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        1.093
N_STARS:         190
X_OFFSET:        375 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1814 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      9
PHOTO_THRESH:    4
SL_URL:          sw01156572000msufc0335.fits
SUN_POSTN:       340.96d {+22h 43m 50s}   -8.05d {-08d 02' 57"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.45d {+05h 13m 48s}  +26.54d {+26d 32' 32"}
MOON_DIST:        50.56 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:05:22 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
ROLL:            222.789d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21385.36 SOD {05:56:25.36} UT,   335.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     699256616
X_OFFSET:        934 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1094
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw01156572000msuni0366.fits
SUN_POSTN:       340.96d {+22h 43m 50s}   -8.05d {-08d 02' 56"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.46d {+05h 13m 51s}  +26.54d {+26d 32' 37"}
MOON_DIST:        50.57 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:05:32 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
ROLL:            222.789d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21385.36 SOD {05:56:25.36} UT,   335.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     699256616
X_OFFSET:        934 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1094
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw01156572000msuni0366.fits
SUN_POSTN:       340.96d {+22h 43m 50s}   -8.05d {-08d 02' 56"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.46d {+05h 13m 51s}  +26.54d {+26d 32' 38"}
MOON_DIST:        50.57 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:05:34 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1156572,   Seg_Num: 0
GRB_RA:           18.3780d {+01h 13m 30.72s} (J2000),
                  18.7151d {+01h 14m 51.62s} (current),
                  17.6533d {+01h 10m 36.79s} (1950)
GRB_DEC:         +44.4830d {+44d 28' 58.7"} (J2000),
                 +44.6052d {+44d 36' 18.8"} (current),
                 +44.2182d {+44d 13' 05.6"} (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:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21177.00 SOD {05:52:57.00} UT,   126.8 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:       340.96d {+22h 43m 50s}   -8.05d {-08d 02' 56"}
SUN_DIST:         62.68 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.46d {+05h 13m 51s}  +26.54d {+26d 32' 38"}
MOON_DIST:        50.60 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.07,-18.21 [deg] galactic lon,lat of the burst
ECL_COORDS:       35.62, 33.60 [deg] ecliptic lon,lat of the burst
COMMENTS:        SWIFT-XRT Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        This is an Update Notice -- the RA,Dec values herein supersede the previous XRT_POS Notice.  
COMMENTS:        TAM values, flux and significance fields are not valid.  
COMMENTS:        This position was automatically generated on the ground using  
COMMENTS:        Photon Counting data telemetered via TDRSS (SPER data).  
COMMENTS:        See http://www.swift.ac.uk/sper/docs.php for details.  
COMMENTS:        This position was enhanced using UVOT field astrometry.  
COMMENTS:        The probability that this is a serendipitous source in the  
COMMENTS:        SPER window is 0.58% < P(seren) < 1.1%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:10:28 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
POINT_ROLL:      222.790d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21915.40 SOD {06:05:15.40} UT,   865.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.393
N_STARS:         190
X_OFFSET:        375 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1814 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01156572000msufc0865.fits
SUN_POSTN:       340.96d {+22h 43m 51s}   -8.05d {-08d 02' 51"}
SUN_DIST:         62.72 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.51d {+05h 14m 02s}  +26.55d {+26d 32' 59"}
MOON_DIST:        50.60 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:10:45 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
POINT_ROLL:      222.790d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21915.40 SOD {06:05:15.40} UT,   865.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.393
N_STARS:         190
X_OFFSET:        375 [pixels]
Y_OFFSET:        190 [pixels]
X_MAX:           1814 [pixels]
Y_MAX:           1629 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01156572000msufc0865.fits
SUN_POSTN:       340.96d {+22h 43m 51s}   -8.05d {-08d 02' 51"}
SUN_DIST:         62.71 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.51d {+05h 14m 03s}  +26.55d {+26d 33' 00"}
MOON_DIST:        50.60 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:12:14 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
ROLL:            222.790d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21915.40 SOD {06:05:15.40} UT,   865.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     699257146
X_OFFSET:        934 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1094
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw01156572000msuni0896.fits
SUN_POSTN:       340.96d {+22h 43m 51s}   -8.05d {-08d 02' 49"}
SUN_DIST:         62.71 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.53d {+05h 14m 06s}  +26.55d {+26d 33' 07"}
MOON_DIST:        50.61 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 28 Feb 23 06:12:22 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1156572,   Seg_Num: 0
POINT_RA:         18.421d {+01h 13m 41s} (J2000)
POINT_DEC:       +44.511d {+44d 30' 40"} (J2000)
ROLL:            222.790d
IMG_START_DATE:  20003 TJD;    59 DOY;   23/02/28
IMG_START_TIME:  21915.40 SOD {06:05:15.40} UT,   865.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     699257146
X_OFFSET:        934 [pixels]
Y_OFFSET:        749 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1094
Y_GRB_POS:       909
BINNING_INDEX:   1
IM_URL:          sw01156572000msuni0896.fits
SUN_POSTN:       340.96d {+22h 43m 51s}   -8.05d {-08d 02' 49"}
SUN_DIST:         62.71 [deg]   Sun_angle= -2.5 [hr] (East of Sun)
MOON_POSTN:       78.53d {+05h 14m 07s}  +26.55d {+26d 33' 07"}
MOON_DIST:        50.61 [deg]
MOON_ILLUM:      59 [%]
GAL_COORDS:      127.10,-18.18 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       35.67, 33.61 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        The GRB Position came from the Window Position in the Mode Command.  
COMMENTS:        The image has 2x2 binning (compression).  
COMMENTS:        All 4 attachments are included.

GCN Circular #33379
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
Using promptly downlinked XRT event data for GRB 230228A, we find an enhanced XRT position of the afterglow: RA, Dec: 18.37804, 44.48289 which is equivalent to:
```
   RA (J2000)  = 01 13 30.73
   Dec (J2000) = +44 28 58.4
```
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/1156572.
Position enhancement is 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 Circular #33380
Gu Lim (PNU), Donghyun Kim (PNU), Dohyeong Kim (PNU), Myungshin Im (SNU ARC/SNU), Gregory S.H. Paek (SNU ARC/SNU), Keun-Hong Park (MAAO), and Seonghun Lim (MAAO) on behalf of GECKO collaboration
We searched for the optical counterpart of a possible short burst GRB 230228A (Dichiara et al. GCN #33378) with the 0.7-m telescope at Miryang Arirang Astronomical Observatory (MAAO), located at Miryang, Republic of Korea. We observed the center of Swift-XRT localization (RA, Dec = 01:13:30.73, +44:28:58.4; Evans et al. GCN #33379) +4.09 hours after report, but could not find any possible transient within the field of view (28.2' x 28.2'). We performed flux calibration with the PS1 catalog and used the AB magnitude system. Each depth means 3 and 5 sigma upper limit for a point source detection. The magnitudes are not corrected for galactic extinction.
```
object     exposures  date-obs (UT)       MJD        band Depth(3σ) Depth(5
σ) FWHM(")
=========================================================================================
GRB230228A 60sx8      2023-02-28T09:56:11 60003.414  V    <18.77     <18.21
     2.8
```
Gravitational wave Electromagnetic wave Counterpart Korean Observatory (GECKO) is a network of 10+ 0.5m to 1m class telescopes over the world.
ᐧ
GCN Circular #33381
T.H. Lu, S.Q. Jiang, S.Y. Fu, X. Liu (NAOC), Z.P. Zhu (NAOC, HUST), D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 230228A detected by Swift (Dichiara et al., GCN 33378) using the NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained 12x200 s frames in the Sloan r-band and 12x200 s frames in the Sloan z-band, starting at 14:37:32 UT on 2023-02-28 (i.e., 8.77 hr after the BAT trigger).
No optical source is detected in our stacked images at the enhanced XRT position (Evans, GCN 33379), and preliminary photometric results are as follows:
```
T_mid-T0 (hr)    Filter   Upper limit(3-sigma)
    9.86                r          >20.6
    9.14                z          >19.5
```
calibrated with the nearby PanSTARRS field and not corrected for Galactic extinction.
GCN Circular #33382
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 2720 s of XRT Photon Counting mode data and 3 UVOT images for GRB 230228A, 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 = 18.37812, +44.48293 which is equivalent to:
```
RA (J2000): 01h 13m 30.75s
Dec (J2000): +44d 28' 58.5"
```
with an uncertainty of 2.1 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 #33383
S. Belkin (IKI, HSE), E. Klunko (ISTP), A. Pozanenko (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed the field of GRB 230228A (Dichiara et al., GCN 33378) with AZT-33 telescope of Mondy observatory starting on Feb. 28 (UT) 12:46:56. We do not detect any optical counterpart within the enhanced Swift/XRT error box (Beardmore et al., GCN 33382). Preliminary photometry of the field is following
```
Date       UT start t-T0     Filter    Exp.    OT   Err  UL(3sigma)

2023-02-28 12:46:56 0.31053  R         30*120  n/d  n/d  21.1
```
The photometry is based on the nearby USNO-B1.0 stars R2
```
RA DEC R2
01:13:35.3661600 +44:26:54.711600 15.50
01:13:18.4240800 +44:28:30.280800 16.70
```
The upper limit is not contradict observations reported earlier (Dichiara et al., GCN 33378; Lim et al., GCN 33380; Lu et al., GCN 33381).
GCN Circular #33384
A. Tohuvavohu (U. Toronto), D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB) and S. Dichiara report on behalf of the Swift-XRT team:
We have analysed 6.9 ks of XRT data for GRB 230228A (Dichiara et al. GCN Circ. 33378), from 102 s to 63.7 ks after the BAT trigger. The data comprise 10 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Beardmore et al. (GCN Circ. 33379).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.94 (+/-0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.82 (+0.27, -0.25). The best-fitting absorption column is 2.1 (+1.1, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 9.7 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 3.9 x 10^-11 (5.0 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     2.1 (+1.1, -0.9) x 10^21 cm^-2
Galactic foreground: 9.7 x 10^20 cm^-2
Excess significance: 1.9 sigma
Photon index:	     1.82 (+0.27, -0.25)
```
If the light curve continues to decay with a power-law decay index of 0.94, the count rate at T+24 hours will be 2.1 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.1 x 10^-14 (1.0 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/01156572.
This circular is an official product of the Swift-XRT team.
GCN Circular #33387
Y.-D. Hu, V. Casanova, E. Fernandez-Garcia, A. J. Castro-Tirado, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy (IAA-CSIC), on behalf of a larger collaboration, report:
Following the detection of GRB 230228A by Swift (Dichiara et al. GCN 33378), we triggered the 0.9m OSN telescope in Granada (Spain) starting on Feb. 28 at 19:34:03 UT (~13.7 hrs post burst). Ten images covering the burst error region were taken in the I-band. No optical afterglow is detected in the stacked image down to I=20.2 mag. These results are in agreement with the non-detection reported by Lim et al. (GCNC 33380), Lu et al. (GCNC 33381) and Belkin et al. (GCNC 33383).
We thank the staff at OSN for their excellent support.
GCN Circular #33389
C. Fletcher (USRA), S. Lesage (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 05:50:51 UT on 28 February 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230228A (trigger 699256256/230228244). which was also detected by Swift BAT (S. Dichiara et al. 2023, GCN 33378). The Fermi GBM on-ground location is consistent with the Swift BAT position.
The angle from the Fermi LAT boresight is 114 degrees.
The GBM light curve consists of a single burst with a duration (T90) of about 2 s (10-1000 keV). The time-averaged spectrum from T0-0.9 to T0+1.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.8 +/- 0.3 and the cutoff energy, parameterized as Epeak, is 110 +/- 20 keV.
The event fluence (10-1000 keV) in this time interval is (5.9 +/- 0.6)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0 s in the 10-1000 keV band is 6 +/- 1 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #33392
A. A. Breeveld (UCL-MSSL) and S. Dichiara (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230228A 122 s after the BAT trigger (Dichiara et al., GCN Circ. 33378). No optical afterglow consistent with the enhanced XRT position (Beardmore et al., GCN Circ. 33382) 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           122          272          147         >20.2
u_FC               335          585          246         >19.5
white              122         1706          240         >20.6
v                  665         1752           97         >18.8
b                  591         1851           88         >19.8
u                  335         1830          341         >19.7
w1                 714         1806          117         >20.0
m2                 689         1780           97         >19.7
w2                 640         1731           78         >20.1
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.085 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #33393
H. A. Krimm (NSF), S. D. Barthelmy (GSFC), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), T. Sakamoto (AGU), M. Stamatikos (OSU) (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 230228A (trigger #1156572) (Dichiara, et al., GCN Circ. 33378). The BAT ground-calculated position is RA, Dec = 18.397, 44.495 deg which is
```
   RA(J2000)  =  01h 13m 35.3s
   Dec(J2000) = +44d 29' 41.9"
```
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment). The partial coding was 78%.
The mask-weighted light curve shows a Fast Rise Exponential Decay single pulse. T90 (15-350 keV) is 2.18 +- 0.40 sec (estimated error including systematics).
The time-averaged spectrum from T-0.05 to T+2.53 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.66 +- 0.17. The fluence in the 15-150 keV band is 3.6 +- 0.4 x 10^-07 erg/cm2.
The 1-sec peak photon flux measured from T+0.18 sec in the 15-150 keV band is 3.0 +- 0.4 ph/cm2/sec. All the quoted errors are at the 90% confidence level.
The results of the batgrbproduct analysis are available at http://gcn.gsfc.nasa.gov/notices_s/1156572/BA/
GCN Circular #33394
G. Schroeder (Northwestern), T. Laskar (Utah), E. Berger (Harvard) report:
"We observed the position of the possibly short GRB 230228A (Dichiara et al. GCN 33378; Fletcher GCN 33389) with the Karl G. Jansky Very Large Array (VLA) under program 23A-296 (PI: Schroeder) beginning on 2023 March 2.02 UT (1.78 days post-burst) at a mean frequency of 6 GHz.
Based on preliminary analysis, we do not detect any radio emission at or near the position of the XRT afterglow (Beardmore et al., GCN 33382) to a 3-sigma limit of 12 microJy. Additional followup is planned.
We thank the VLA staff for quickly approving and executing these observations."
GCN Circular #33426
K. Noonan (UVI), N. Orange (OrangeWave Innovative Science, LLC), P. Gokuldass (Florida Tech), D. Morris (UVI), K. Smith (UVI), R. Querrard (UVI) report:
We observed the field of GRB 230228A (Dichiara et al., GCN 33378) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 02-28-2023 starting at 23:29:41 UT (T+17.5 hrs). We performed a series of exposures in the R filter with a total exposure of 2940s. The weather conditions were clear during the hours of observation. The GRB was positioned at a lower altitude with an average airmass of 2.7.
We detect no new source within the enhanced XRT position error circle (Beardmore et al., GNC 33382) consistent with other non-detections (Lim et al., GCN 33380, Lu et al., GCN 33381, Belkin et al., GCN 33383, Hu et al., GCN 33387, and Breeveld et al., GCN 33392) and report the following 3-sigma upper limit:
```
T_mid            ||Exposure     ||Filter      ||Limit
T+ 18 hrs        ||2940s        ||R           ||>20.6
```
The limit is estimated from comparison to nearby USNO B1 stars and is not corrected for Galactic extinction. The VIRT is still in the commissioning phase.
We acknowledge financial support from NASA MUREP MIRO award 80NSSC21M0001, NASA EPSCoR award 80NSSC22M0063, and NSF EiR award 1901296. R.Q. and N.B.O. also acknowledge financial support from South Carolina Space Grant award 80NSSC20M0054. This message can be cited.
GCN Circular #33436
T. Komesh (NU), Zh. Maksut (NU), B. Grossan (UCB, NU), Zh. Abdullayev (NU), M. Krugov (FAI), report on behalf of the Energetic Cosmos Laboratory:
The Nazarbayev University Transient Telescope at Assy-Turgen Astrophysical Observatory (NUTTelA-TAO) observed the field of GRB 230228A, observing in Sloan g', r' and i' bands, with the Burst Simultaneous Three-Channel Imager (BSTI; Grossan, Kumar & Smoot 2019, JHEA, 32, 14).
We obtained 10x300 s frames starting at UT 2023-02-28 14:03:02, 8.2 hours after the BAT trigger. Observations were made under clear conditions, beginning with the target at an altitude of 45 deg. No new or changing sources consistent with the XRT position (Evans 2023, GCN 33379) were detected. Note that these observations provide essentially full-time coverage, simultaneous in all three bands. We report the following results:
```
start time   t-t0(h)     end time      UL g'    UL r'  ULi'   exposure_time (s)
------------    -----       -----------       ------    ------     -----      ------
14:03:02     8.2      14:53:02        19.9    19.6    19.5	300
```
start time is in UT. t-t0(h) gives the time since trigger, in hours. UL gives the 5 sigma upper limit sensitivity in magnitudes for images with individual exposure times. The given upper limit values are derived from the average calibration with only 3 standard stars per frame, and no other analysis or corrections.
----------------------------------
```
NU = Nazarbayev University, Nur-Sultan, Kazakhstan
UCB = University of California, Berkeley, USA
FAI = Fesenkov Astrophysical Institute, Kazakhstan
```
This research has been funded by the Science Committee of the Ministry of Science and Higher Education of the Republic of Kazakhstan (Grant No. AP14870504). The NUTTelA-TAO Team acknowledges the support of the staff of the Assy-Turgen Astrophysical Observatory, Almaty, Kazakhstan, and the Fesenkov Astrophysical Institute, Almaty, Kazkhstan.
GCN Circular #33557
Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, I. Perez-Garcia, M.D. Caballero-Garcia, R. Sanchez-Ramirez (IAA-CSIC), Bin-bin Zhang (NJU) and D. Garcia (GTC, IAC) on behalf of a larger collaboration, report:
Following the detection of short GRB 230228A by Swift (Dichiara et al. GCN 33378), we triggered the 10.4 m Gran Telescopio de Canarias (GTC) in La Palma (Spain) to image the GRB location with the OSIRIS instrument in two epochs (Mar 1 20:16 UT and Mar 3, 20:02 UT, 1.6 and 2.6 days post-burst respectively). Within the XRT error region, a constant brightness (z-band magnitude = 23.6) is found, which we suggest as the potential host galaxy of this burst.
We thank the excellent support from the GTC staff.

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Jochen Greiner, last update: 03-Apr-2023 [Disclaimer]