Gamma-ray Burst 230506B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN Circular #33727
S. Dichiara (PSU), C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (U Tampa), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 12:45:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230506B (trigger=1167266). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 326.993, +44.540 which is
```
   RA(J2000) = 21h 47m 58.32s
   Dec(J2000) = +44d 32' 24.00"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). No BAT light-curve is available at this time.
The XRT began observing the field at 12:47:12 UT, 114 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 326.97876, 44.51108 which is equivalent to:
```
   RA(J2000)  = 21h 47m 54.90s
   Dec(J2000) = +44d 30' 39.9"
```
with an uncertainty of 6 arcseconds (radius, 90% containment). This location is 110 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.
UVOT prompt data are not available at this time. We are waiting for the full dataset to search for an UVOT counterpart.
Due to a communications issue, no realtime alerts were received for this GRB. Therefore, results in this GCN are based on rapidly reported results, and will be refined in a future GCN Circular.
Burst Advocate for this burst is S. Dichiara (sbd5667 AT psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
red DSS finding chart ps-file
GCN Circular #33728
V.Lipunov, P.Balanutsa, A.Kuznetsov, N.Tiurina, O.Gress, E.Gorbovskoy, G.Antipov,K.Zhirkov, D.Vlasenko, Ya.Kechin, A.Chasovnikov,V.Senik, V.Topolev, Yu.Tselik, Siyu Wu, V.Vladimirov, D.Cheryasov (Lomonosov Moscow State University, SAI,Physics Department), C.Francile, F. Podesta, C.Lopez, R. Podesta (Observatorio Astronomico Felix Aguilar OAFA), D.A.H.Buckley (SAAO), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.Corella,L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), N.M.Budnev, O.Ershova (ISU,API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University), K.Vetrov, V.Shumkov, T.Pogrosheva, E.Minkina, O.Ershova (Lomonosov MSU)
MASTER-Amur robotic telescope (Global MASTER-Net http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Blagoveshchensk State Pedagogical University) was pointed to the SWIFT GRB230506.53 (trigger No 1167266,21h 47m 54.90s , +44d 30m 39.9s, R=0.1) errorbox 6276 sec after trigger time at 2023-05-06 14:29:54 UT, so as alert didn't come from GCN socket system.
The observations began at zenith distance = 72 deg. The sun altitude is -22.3 deg.The galactic latitude b = -7 deg., longitude l = 92 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2214809
We obtained following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

    6367 |         MASTER-Amur |   C |   180 | 16.8 |
    6567 |         MASTER-Amur |   C |   180 | 17.2 |
    6767 |         MASTER-Amur |   C |   180 | 17.3 |
    7037 |         MASTER-Amur |   C |   720 | 18.0 |  Coadd
    6966 |         MASTER-Amur |   C |   180 | 17.3 |
    7166 |         MASTER-Amur |   C |   180 | 17.4 |
    7366 |         MASTER-Amur |   C |   180 | 17.4 |
```
Filter C is a clear (unfiltred) band.
Observations and analysis will be continued. The message may be cited.
GCN Circular #33729
S. Dichiara (PSU), C. Gronwall (PSU), J. A. Kennea (PSU), A. Y. Lien (U Tampa), K. L. Page (U Leicester), B. Sbarufatti (INAF-OAB) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 12:45:18 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230506B (trigger=1167266). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 326.993, +44.540 which is
```
   RA(J2000) = 21h 47m 58.32s
   Dec(J2000) = +44d 32' 24.00"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). No BAT light-curve is available at this time.
The XRT began observing the field at 12:47:12 UT, 114 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 326.97876, 44.51108 which is equivalent to:
```
   RA(J2000)  = 21h 47m 54.90s
   Dec(J2000) = +44d 30' 39.9"
```
with an uncertainty of 6 arcseconds (radius, 90% containment). This location is 110 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.
UVOT prompt data are not available at this time. We are waiting for the full dataset to search for an UVOT counterpart.
Due to a communications issue, no realtime alerts were received for this GRB. Therefore, results in this GCN are based on rapidly reported results, and will be refined in a future GCN Circular.
Burst Advocate for this burst is S. Dichiara (sbd5667 AT psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 May 23 15:58:12 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.976d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 32' 60"} (J2000)
POINT_ROLL:      77.174d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57223.42 SOD {15:53:43.42} UT,   19311.4 [sec] since BAT Trigger Time
FILTER:          9, B
BKG_MEAN:        1.863
N_STARS:         190
X_OFFSET:        583 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1542 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw01167266001msufc796911.fits
SUN_POSTN:        43.41d {+02h 53m 39s}  +16.59d {+16d 35' 20"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      234.97d {+15h 39m 53s}  -21.64d {-21d 38' 35"}
MOON_DIST:       106.56 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 May 23 15:58:31 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.976d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 32' 60"} (J2000)
POINT_ROLL:      77.174d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57223.42 SOD {15:53:43.42} UT,   19311.4 [sec] since BAT Trigger Time
FILTER:          9, B
BKG_MEAN:        1.863
N_STARS:         190
X_OFFSET:        583 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1542 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      11
PHOTO_THRESH:    6
SL_URL:          sw01167266001msufc796911.fits
SUN_POSTN:        43.41d {+02h 53m 39s}  +16.59d {+16d 35' 21"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      234.98d {+15h 39m 54s}  -21.64d {-21d 38' 39"}
MOON_DIST:       106.56 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 May 23 15:59:39 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.976d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 32' 60"} (J2000)
ROLL:            77.174d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57223.42 SOD {15:53:43.42} UT,   19311.4 [sec] since BAT Trigger Time
FILTER:          9, B
EXPOSURE_ID:     705081254
X_OFFSET:        902 [pixels]
Y_OFFSET:        919 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1062
Y_GRB_POS:       1079
BINNING_INDEX:   1
IM_URL:          sw01167266001msuni796943.fits
SUN_POSTN:        43.41d {+02h 53m 39s}  +16.59d {+16d 35' 21"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      234.99d {+15h 39m 57s}  -21.65d {-21d 38' 51"}
MOON_DIST:       106.55 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
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:     Sat 06 May 23 15:59:47 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.976d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 32' 60"} (J2000)
ROLL:            77.174d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57223.42 SOD {15:53:43.42} UT,   19311.4 [sec] since BAT Trigger Time
FILTER:          9, B
EXPOSURE_ID:     705081254
X_OFFSET:        902 [pixels]
Y_OFFSET:        919 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1062
Y_GRB_POS:       1079
BINNING_INDEX:   1
IM_URL:          sw01167266001msuni796943.fits
SUN_POSTN:        43.41d {+02h 53m 39s}  +16.59d {+16d 35' 22"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      234.99d {+15h 39m 57s}  -21.65d {-21d 38' 52"}
MOON_DIST:       106.55 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
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:     Sat 06 May 23 16:03:28 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.975d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 33' 01"} (J2000)
POINT_ROLL:      77.173d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57536.08 SOD {15:58:56.08} UT,   19624.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.938
N_STARS:         190
X_OFFSET:        343 [pixels]
Y_OFFSET:        360 [pixels]
X_MAX:           1782 [pixels]
Y_MAX:           1799 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01167266001msufc797224.fits
SUN_POSTN:        43.41d {+02h 53m 39s}  +16.59d {+16d 35' 24"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      235.02d {+15h 40m 06s}  -21.66d {-21d 39' 32"}
MOON_DIST:       106.53 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 May 23 16:03:39 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.975d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 33' 01"} (J2000)
POINT_ROLL:      77.173d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57536.08 SOD {15:58:56.08} UT,   19624.1 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.938
N_STARS:         190
X_OFFSET:        343 [pixels]
Y_OFFSET:        360 [pixels]
X_MAX:           1782 [pixels]
Y_MAX:           1799 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01167266001msufc797224.fits
SUN_POSTN:        43.41d {+02h 53m 39s}  +16.59d {+16d 35' 24"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      235.03d {+15h 40m 06s}  -21.66d {-21d 39' 33"}
MOON_DIST:       106.53 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 May 23 16:04:50 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.975d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 33' 01"} (J2000)
ROLL:            77.173d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57536.08 SOD {15:58:56.08} UT,   19624.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     705081567
X_OFFSET:        902 [pixels]
Y_OFFSET:        919 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1062
Y_GRB_POS:       1079
BINNING_INDEX:   1
IM_URL:          sw01167266001msuni797256.fits
SUN_POSTN:        43.42d {+02h 53m 40s}  +16.59d {+16d 35' 25"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      235.04d {+15h 40m 09s}  -21.66d {-21d 39' 46"}
MOON_DIST:       106.53 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Image.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
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:     Sat 06 May 23 16:05:06 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.975d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 33' 01"} (J2000)
ROLL:            77.173d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57536.08 SOD {15:58:56.08} UT,   19624.1 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     705081567
X_OFFSET:        902 [pixels]
Y_OFFSET:        919 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1062
Y_GRB_POS:       1079
BINNING_INDEX:   1
IM_URL:          sw01167266001msuni797256.fits
SUN_POSTN:        43.42d {+02h 53m 40s}  +16.59d {+16d 35' 25"}
SUN_DIST:         68.70 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      235.04d {+15h 40m 10s}  -21.66d {-21d 39' 49"}
MOON_DIST:       106.53 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Image.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
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:     Sat 06 May 23 16:07:50 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.975d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 33' 01"} (J2000)
POINT_ROLL:      77.173d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57791.48 SOD {16:03:11.48} UT,   19879.5 [sec] since BAT Trigger Time
FILTER:          9, B
BKG_MEAN:        2.333
N_STARS:         190
X_OFFSET:        583 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1542 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01167266001msufc797479.fits
SUN_POSTN:        43.42d {+02h 53m 40s}  +16.59d {+16d 35' 27"}
SUN_DIST:         68.71 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      235.07d {+15h 40m 16s}  -21.67d {-21d 40' 18"}
MOON_DIST:       106.51 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sat 06 May 23 16:08:03 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1167266,   Seg_Num: 1
POINT_RA:        326.975d {+21h 47m 54s} (J2000)
POINT_DEC:       +44.550d {+44d 33' 01"} (J2000)
POINT_ROLL:      77.173d
IMG_START_DATE:  20070 TJD;   126 DOY;   23/05/06
IMG_START_TIME:  57791.48 SOD {16:03:11.48} UT,   19879.5 [sec] since BAT Trigger Time
FILTER:          9, B
BKG_MEAN:        2.333
N_STARS:         190
X_OFFSET:        583 [pixels]
Y_OFFSET:        600 [pixels]
X_MAX:           1542 [pixels]
Y_MAX:           1559 [pixels]
DET_THRESH:      13
PHOTO_THRESH:    7
SL_URL:          sw01167266001msufc797479.fits
SUN_POSTN:        43.42d {+02h 53m 40s}  +16.59d {+16d 35' 27"}
SUN_DIST:         68.71 [deg]   Sun_angle= 5.1 [hr] (West of Sun)
MOON_POSTN:      235.07d {+15h 40m 16s}  -21.67d {-21d 40' 20"}
MOON_DIST:       106.51 [deg]
MOON_ILLUM:      99 [%]
GAL_COORDS:       91.90, -6.99 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      352.63, 52.95 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        This Notice is generated as a result of an uploaded TOO on an old GRB -- this is not a newly detected burst.  
COMMENTS:        And the IMG_START_DATE/TIME fields are the current epoch -- not the original detection.  
COMMENTS:        All 4 attachments are included.

GCN Circular #33733
Paul Kuin (MSSL/UCL) and Simone Dichiara(PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230506B 114 s after the BAT trigger (Dichiara et al., GCN Circ. 33727). A candidate afterglow consistent with the XRT position is detected in the initial UVOT exposures.
Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white              113          271          147          20.19 +/- 0.24
white              614          807           38         >19.8
u                  334          583          247         >19.9
u                10511        11899          738          20.66 +/- 0.30
b                  589          783           39         >19.1
uvw1               714          734           20         >17.6
uvm2               688          708           20         >17.2
uvw2               639          658           20         >19.6
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.293 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #33737
D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), S. Dichiara (PSU) report on behalf of the Swift-XRT team:
We have analysed 7.9 ks of XRT data for GRB 230506B, from 68 s to 50.9 ks after the BAT trigger. The data comprise 124 s in Windowed Timing (WT) mode (the first 9 s were taken while Swift was slewing) with the remainder in Photon Counting (PC) mode. Using 335 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 326.98168, +44.51111 which is equivalent to:
```
RA (J2000): 21h 47m 55.60s
Dec(J2000): +44d 30' 40.0"
```
with an uncertainty of 2.6 arcsec (radius, 90% confidence).
The light curve can be modelled with an initial power-law decay with an index of alpha=1.83 (+0.16, -0.17), followed by a break at T+146 s to an alpha of 4.87 (+0.29, -0.24).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 1.45 (+/-0.13). The best-fitting absorption column is 5.8 (+1.3, -1.1) x 10^21 cm^-2, in excess of the Galactic value of 3.8 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 5.6 x 10^-11 (7.1 x 10^-11) erg cm^-2 count^-1.
A summary of the WT-mode spectrum is thus:
```
Total column:	     5.8 (+1.3, -1.1) x 10^21 cm^-2
Galactic foreground: 3.8 x 10^21 cm^-2
Excess significance: 3.0 sigma
Photon index:	     1.45 (+/-0.13)
```
If the light curve continues to decay with a power-law decay index of 4.87, the count rate at T+24 hours will be 5.0 x 10^-13 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.8 x 10^-23 (3.6 x 10^-23) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01167266.
This circular is an official product of the Swift-XRT team.
GCN Circular #33740
R. Strausbaugh (University of Minnesota), A. Cucchiara (NASA) report on behalf of a larger collaboration:
We observed the GRB 230506B (Dichiara et al., GCN 33727) field with the LCOGT 1-meter Sinistro instrument at the Teide Observatory, Tenerife site, on May 7, from 04:09 to 04:41 UT (corresponding to 15.43 to 15.93 hours from the GRB trigger time) with the SDSS r and i filters.
We performed a series of 3x300s exposures in each band. We do not detect an uncatalouged source within the Swift-XRT error region in either band.
The following upper limits are calculated using the PanSTARRS catalog as reference:
```
r > 22.3
i > 21.8
```
These magnitudes are not corrected for galactic extinction.
GCN Circular #33742
S. D. Barthelmy (GSFC), S. Dichiara (PSU), H. A. Krimm (NSF), 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-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 230506B (trigger #1167266) (Dichiara et al., GCN Circ. 33727). The BAT ground-calculated position is RA, Dec = 326.986, 44.514 deg which is
```
   RA(J2000)  =  21h 47m 56.6s
   Dec(J2000) = +44d 30' 50.9"
```
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 73%.
The mask-weighted light curve shows a multi-peaked structure that starts at ~T0 and ends at ~T+80 s. The main peak occurs at ~T+11 s. T90 (15-350 keV) is 61.54 +- 10.89 sec (estimated error including systematics).
The time-averaged spectrum from T+0.02 to T+76.30 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.41 +- 0.11. The fluence in the 15-150 keV band is 2.9 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+10.60 sec in the 15-150 keV band is 4.6 +- 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/1167266/BA/
GCN Circular #33750
Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team:
The XRT position of GRB230506B falls on a Gaia DR3 source of magnitude BP = 19.89, Gmag = 19.34. We see from further analysis of the UVOT data that within errors the detections are consistent with the Gaia source. The UVOT data are therefore not the optical afterglow of the GRB.
GCN Circular #33758
O.J. Roberts (USRA/NASA-MSFC), S. Bala (USRA), C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 12:45:18.77 UT on 06 May 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 230506B (trigger 705069923 / 230506531), which was also detected by the Swift/BAT (S. Dichiara et al. 2023, GCN 33729 and S.D. Barthelmy et al. 2023, GCN 33742). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 47 degrees.
The GBM light curve consists of multiple short bursts with a duration (T90) of about 38 s (50-300 keV). The time-averaged spectrum from T0-0.8 s to T0+39.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.28 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 1767 +/- 576 keV
The event fluence (10-1000 keV) in this time interval is (1.13 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+10.4 s in the 10-1000 keV band is 8.1 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #33935
B. O'Connor (GWU), S. Dichiara (PSU), E. Troja (UTV), S. B. Cenko (NASA-GSFC, UMD), C. Kouveliotou (GWU), T. Sakamoto (AGU), A. Kutyrev (UMD), G. Ryan (Perimeter), R. Ricci (INAF), G. Bruni (INAF):
We carried out two Chandra ToO observation of GRB 230506B beginning on May 11, 2023 at 06:59:55 UT and June 01, 2023 at 19:31:19 UT with ACIS-S as part of program 24400201 (PI: O'Connor) for a total of 19 ks and 55 ks, respectively. The initial observation began ~4.8 days after the GRB trigger (Dichiara et al. GCN 33727).
Within the XRT localization (Burrows et al. GCN 33737), we detect a single point source at RA, DEC = 21:47:55.6, 44:30:41.6 with an uncertainty of 0.9" (90% confidence, statistical + systematic). The source displays rapid fading between the two Chandra epochs confirming that it is the X-ray afterglow of GRB 230506B.
We would like to thank Patrick Slane, Harvey Tananbaum, Dan Schwartz, Scott Wolk, and the CXO staff for rapidly approving and planning this observation.
GCN Circular #35180
K. Noonan (UVI), P. Gokuldass (ERAU), N. Orange (OrangeWave Innovative Science, LLC), D. Morris (NASA), K. Smith (UVI), R. Querrard (UVI), T. Lombardi (Eckerd College)
We observed the field of GRB230506B (Dichiara et al. GCN 33727) with the 0.5m Virgin Island Robotic Telescope (VIRT) at the University of the Virgin Islands' Etelman Observatory on 05-07-2023 starting at 05:20:40.065 (T+16.33 hrs). We performed a series of exposures in R filter with a total exposure of 3860 s. The weather conditions were clear during the hours of observation with an average airmass of ~2.6.
We do not detect an uncatalogued source within the Swift-XRT error region and report the following 3-sigma upper limit:
```
T_mid     ||Exposure ||Filter ||Limit 
T+17 hrs ||3860s     ||R        ||>20.1 
```
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.

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Jochen Greiner, last update: 24-Nov-2023 [Disclaimer]