Gamma-ray Burst 230409B

(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 09 Apr 23 04:57:17 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1163401,   Seg_Num: 0
GRB_RA:          329.530d {+21h 58m 07s} (J2000),
                 329.742d {+21h 58m 58s} (current),
                 329.077d {+21h 56m 18s} (1950)
GRB_DEC:         +52.854d {+52d 51' 15"} (J2000),
                 +52.966d {+52d 57' 57"} (current),
                 +52.615d {+52d 36' 53"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       2569 [cnts]    Image_Peak=160 [image_cnts]
TRIGGER_DUR:     1.024 [sec] 
TRIGGER_INDEX:   139     E_range: 15-50 keV
BKG_INTEN:       14757 [cnts]
BKG_TIME:        17800.92 SOD {04:56:40.92} UT
BKG_DUR:         8 [sec]
GRB_DATE:        20043 TJD;    99 DOY;   23/04/09
GRB_TIME:        17816.79 SOD {04:56:56.79} UT
GRB_PHI:         -87.45 [deg]
GRB_THETA:        29.20 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     19.72 [sigma]
IMAGE_SIGNIF:    9.20 [sigma]
MERIT_PARAMS:     +1  +0  +0  +0  +1  +0  +0  +1 -50  +0 
SUN_POSTN:        17.62d {+01h 10m 30s}   +7.48d {+07d 28' 34"}
SUN_DIST:         59.71 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.68d {+15h 30m 44s}  -20.98d {-20d 58' 52"}
MOON_DIST:       110.79 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.57 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:        3.97, 58.55 [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 = 6.76,-19.22 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 09 Apr 23 04:58:45 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.515d {+21h 58m 04s} (J2000)
POINT_DEC:       +52.861d {+52d 51' 41"} (J2000)
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  17918.03 SOD {04:58:38.03} UT,   101.2 [sec] since BAT Trigger 
Time
COUNTS:          3    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 09 Apr 23 05:06:40 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1163401,   Seg_Num: 0
GRB_RA:          329.5143d {+21h 58m 03.43s} (J2000),
                 329.7259d {+21h 58m 54.20s} (current),
                 329.0605d {+21h 56m 14.52s} (1950)
GRB_DEC:         +52.8322d {+52d 49' 55.9"} (J2000),
                 +52.9440d {+52d 56' 38.2"} (current),
                 +52.5928d {+52d 35' 34.2"} (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:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18175.00 SOD {05:02:55.00} UT,   358.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        17.63d {+01h 10m 31s}   +7.48d {+07d 28' 43"}
SUN_DIST:         59.71 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.77d {+15h 31m 05s}  -21.01d {-21d 00' 34"}
MOON_DIST:       110.75 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.42, -1.59 [deg] galactic lon,lat of the burst
ECL_COORDS:        3.93, 58.54 [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:     Sun 09 Apr 23 05:11:13 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 43"} (J2000)
POINT_ROLL:      121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18203.15 SOD {05:03:23.15} UT,   386.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.596
N_STARS:         190
X_OFFSET:        565 [pixels]
Y_OFFSET:        516 [pixels]
X_MAX:           1524 [pixels]
Y_MAX:           1475 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw01163401000msufc0386.fits
SUN_POSTN:        17.63d {+01h 10m 32s}   +7.48d {+07d 28' 47"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.82d {+15h 31m 16s}  -21.02d {-21d 01' 24"}
MOON_DIST:       110.73 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 09 Apr 23 05:11:28 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 43"} (J2000)
POINT_ROLL:      121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18203.15 SOD {05:03:23.15} UT,   386.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.596
N_STARS:         190
X_OFFSET:        565 [pixels]
Y_OFFSET:        516 [pixels]
X_MAX:           1524 [pixels]
Y_MAX:           1475 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw01163401000msufc0386.fits
SUN_POSTN:        17.63d {+01h 10m 32s}   +7.48d {+07d 28' 47"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.82d {+15h 31m 16s}  -21.02d {-21d 01' 27"}
MOON_DIST:       110.73 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [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 09 Apr 23 05:12:53 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 43"} (J2000)
ROLL:            121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18203.15 SOD {05:03:23.15} UT,   386.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     702709434
X_OFFSET:        884 [pixels]
Y_OFFSET:        835 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       995
BINNING_INDEX:   1
IM_URL:          sw01163401000msuni0418.fits
SUN_POSTN:        17.63d {+01h 10m 32s}   +7.48d {+07d 28' 49"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.83d {+15h 31m 20s}  -21.03d {-21d 01' 42"}
MOON_DIST:       110.73 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [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 09 Apr 23 05:13:07 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 43"} (J2000)
ROLL:            121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18203.15 SOD {05:03:23.15} UT,   386.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     702709434
X_OFFSET:        884 [pixels]
Y_OFFSET:        835 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       995
BINNING_INDEX:   1
IM_URL:          sw01163401000msuni0418.fits
SUN_POSTN:        17.63d {+01h 10m 32s}   +7.48d {+07d 28' 49"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.83d {+15h 31m 20s}  -21.03d {-21d 01' 45"}
MOON_DIST:       110.73 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [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 09 Apr 23 05:11:59 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1163401,   Seg_Num: 0
GRB_RA:          329.5150d {+21h 58m 03.59s} (J2000),
                 329.7266d {+21h 58m 54.37s} (current),
                 329.0612d {+21h 56m 14.69s} (1950)
GRB_DEC:         +52.8322d {+52d 49' 55.9"} (J2000),
                 +52.9440d {+52d 56' 38.2"} (current),
                 +52.5928d {+52d 35' 34.2"} (1950)
GRB_ERROR:       1.9 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18175.00 SOD {05:02:55.00} UT,   358.2 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        17.63d {+01h 10m 32s}   +7.48d {+07d 28' 48"}
SUN_DIST:         59.71 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.82d {+15h 31m 18s}  -21.03d {-21d 01' 32"}
MOON_DIST:       110.73 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.42, -1.59 [deg] galactic lon,lat of the burst
ECL_COORDS:        3.93, 58.54 [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:     Sun 09 Apr 23 05:18:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 44"} (J2000)
POINT_ROLL:      121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18678.75 SOD {05:11:18.75} UT,   862.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.600
N_STARS:         190
X_OFFSET:        325 [pixels]
Y_OFFSET:        276 [pixels]
X_MAX:           1764 [pixels]
Y_MAX:           1715 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw01163401000msufc0861.fits
SUN_POSTN:        17.64d {+01h 10m 33s}   +7.48d {+07d 28' 54"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.88d {+15h 31m 32s}  -21.04d {-21d 02' 40"}
MOON_DIST:       110.71 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 09 Apr 23 05:18:30 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 44"} (J2000)
POINT_ROLL:      121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18678.75 SOD {05:11:18.75} UT,   862.0 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        6.600
N_STARS:         190
X_OFFSET:        325 [pixels]
Y_OFFSET:        276 [pixels]
X_MAX:           1764 [pixels]
Y_MAX:           1715 [pixels]
DET_THRESH:      22
PHOTO_THRESH:    13
SL_URL:          sw01163401000msufc0861.fits
SUN_POSTN:        17.64d {+01h 10m 33s}   +7.48d {+07d 28' 54"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.88d {+15h 31m 32s}  -21.05d {-21d 02' 43"}
MOON_DIST:       110.71 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [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 09 Apr 23 05:19:55 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 44"} (J2000)
ROLL:            121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18678.75 SOD {05:11:18.75} UT,   862.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     702709909
X_OFFSET:        884 [pixels]
Y_OFFSET:        835 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       995
BINNING_INDEX:   1
IM_URL:          sw01163401000msuni0893.fits
SUN_POSTN:        17.64d {+01h 10m 33s}   +7.48d {+07d 28' 55"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.90d {+15h 31m 35s}  -21.05d {-21d 02' 59"}
MOON_DIST:       110.70 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [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 09 Apr 23 05:20:09 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1163401,   Seg_Num: 0
POINT_RA:        329.512d {+21h 58m 03s} (J2000)
POINT_DEC:       +52.862d {+52d 51' 44"} (J2000)
ROLL:            121.325d
IMG_START_DATE:  20043 TJD;    99 DOY;   23/04/09
IMG_START_TIME:  18678.75 SOD {05:11:18.75} UT,   862.0 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     702709909
X_OFFSET:        884 [pixels]
Y_OFFSET:        835 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1044
Y_GRB_POS:       995
BINNING_INDEX:   1
IM_URL:          sw01163401000msuni0893.fits
SUN_POSTN:        17.64d {+01h 10m 33s}   +7.48d {+07d 28' 55"}
SUN_DIST:         59.73 [deg]   Sun_angle= 3.2 [hr] (West of Sun)
MOON_POSTN:      232.90d {+15h 31m 36s}  -21.05d {-21d 03' 01"}
MOON_DIST:       110.70 [deg]
MOON_ILLUM:      90 [%]
GAL_COORDS:       98.44, -1.56 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        3.97, 58.57 [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 Circular #33592
A. P. Beardmore (U Leicester), C. Gronwall (PSU), A. Y. Lien (U Tampa), K. L. Page (U Leicester), T. Sakamoto (AGU), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 04:56:57 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 230409B (trigger=1163401). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 329.530, +52.854 which is
```
   RA(J2000) = 21h 58m 07s
   Dec(J2000) = +52d 51' 15"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The immediately available BAT light curve starts at ~ a few seconds after the BAT trigger time. The light curve shows a small hump from ~50 to 100 s, however, further ground data will be required to determine whether the hump is due to background fluctuation.
The XRT began observing the field at 04:58:38.0 UT, 101.2 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 329.51486, 52.83228 which is equivalent to:
```
   RA(J2000)  = 21h 58m 03.57s
   Dec(J2000) = +52d 49' 56.2"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 84 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 7.56 x 10^21 cm^-2 (Willingale et al. 2013).
UVOT took a finding chart exposure of 150 seconds with the White filter starting 386 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 none of the XRT error circle. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. No correction has been made for the large, but uncertain, extinction expected.
Burst Advocate for this burst is A. P. Beardmore (apb AT star.le.ac.uk). 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 Circular #33594
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team.
Using 1709 s of XRT Photon Counting mode data and 2 UVOT images for GRB 230409B, 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 = 329.51474, +52.83212 which is equivalent to:
```
RA (J2000): 21h 58m 3.54s
Dec (J2000): +52d 49' 55.6"
```
with an uncertainty of 2.2 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 #33595
GRB 230409B: Swift/UVOT Detection
N. Paul Kuin (UCL/MSSL) and A. P. Beardmore (U. Leicester) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 230409B 386 s after the BAT trigger (Beardmore et al., GCN Circ. 33592). A weak fading source consistent with the XRT position (Beardmore et al. GCN Circ. 33592) is detected in the initial UVOT exposures at position RA=329.5158, Dec=52.8321 deg.
Preliminary detections and 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)           Mag

white              386          536          147         19.35 +/- 0.20
v                  542         1931          156        >18.1
b                  642         2029          156        >19.4
u                  616         2004          156        >19.0
w1                 592         1980          156        >18.8
m2                 567         1955          156        >19.2
w2                 692         1906          136        >20.0
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 1.226 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #33596
V. Lipunov, V.Kornilov, E.Gorbovskoy, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Kuznetsov, D. Vlasenko, G.Antipov, D.Zimnukhov, V.Senik, E.Minkina, A.Chasovnikov, V.Topolev, D.Kuvshinov, D.Cheryasov, Ya.Kechin (Lomonosov Moscow State University, SAI, Physics Department),
R. Podesta, C.Lopez, F. Podesta, C.Francile (Observatorio Astronomico Felix Aguilar OAFA),
R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias),
D. Buckley (South African Astronomical Observatory),
O.A. Gres, N.M. Budnev (Irkutsk State University, API),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the Swift GRB 230409B ( A. P. Beardmore et al., GCN 33592) errorbox 42781 sec after notice time and 42806 sec after trigger time at 2023-04-09 16:50:23 UT, with upper limit up to 15.5 mag. Observations started at twilight. The observations began at zenith distance = 83 deg. The sun altitude is -12.2 deg.
The galactic latitude b = -2 deg., longitude l = 99 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2209455
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   42897 |   MASTER-Kislovodsk |   C |   180 | 15.5 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #33598
D. M. Palmer (LANL), S. D. Barthelmy (GSFC), A. P. Beardmore (U Leicester), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), 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 230409B (trigger #1163401) (Beardmore et al., GCN Circ. 33592). The BAT ground-calculated position is RA, Dec = 329.516, 52.832 deg which is
```
   RA(J2000)  =  21h 58m 03.8s
   Dec(J2000) = +52d 49' 55.1"
```
with an uncertainty of 1.7 arcmin, (radius, sys+stat, 90% containment). The partial coding was 32%.
The mask-weighted light curve shows a single-pulse structure that starts at ~T-1 s, peaks at ~T+1 s, and ends at ~T+12 s. The hump at ~50 s to 100 s mentioned in the previous circular (Beardmore et al., GCN Circ. 33592) is due to background fluctuation and is not part of the burst. T90 (15-350 keV) is 9.79 +- 2.59 sec (estimated error including systematics).
The time-averaged spectrum from T-0.58 to T+11.78 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.86 +- 0.19. The fluence in the 15-150 keV band is 9.9 +- 1.2 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+0.43 sec in the 15-150 keV band is 3.7 +- 0.5 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/1163401/BA/
GCN Circular #33599
P. D'Avanzo (INAF-OAB), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) , D.N. Burrows (PSU), J. D. Gropp (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester) and A.P. Beardmore report on behalf of the Swift-XRT team:
We have analysed 6.6 ks of XRT data for GRB 230409B (Beardmore et al. GCN Circ. 33592), from 338 s to 52.1 ks after the BAT trigger. The data comprise 19 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Evans et al. (GCN Circ. 33594).
The light curve can be modelled with a power-law decay with a decay index of alpha=0.87 (+0.04, -0.03).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.97 (+0.22, -0.21). The best-fitting absorption column is 1.23 (+0.27, -0.24) x 10^22 cm^-2, in excess of the Galactic value of 7.6 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 5.2 x 10^-11 (9.9 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     1.23 (+0.27, -0.24) x 10^22 cm^-2
Galactic foreground: 7.6 x 10^21 cm^-2
Excess significance: 3.3 sigma
Photon index:	     1.97 (+0.22, -0.21)
```
If the light curve continues to decay with a power-law decay index of 0.87, the count rate at T+24 hours will be 0.020 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 1.1 x 10^-12 (2.0 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01163401.
This circular is an official product of the Swift-XRT team.
GCN Circular #33607
C. Adami (LAM), B. Schneider (MIT), S. Basa (LAM), E. Le Floc'h, D. Turpin, D. G�tz (CEA Paris-Saclay), S. D. Vergani (GEPI, Obs. de Paris), report on behalf of a larger collaboration:
We observed the field of GRB 230409B (Beardmore et al., GCN 33592) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. Four exposures were obtained in the i-band (2x300s + 2x600s) from 2023 10 April 03:03:03 UT to 2023 10 April 03:44:17 UT (mid time ~22.3h after trigger). In the combined frame, we do not detect any source at the position reported by Evans et al., GCN 33594 and Kuin et al., GCN 33595 down to the following 3-sigma limit:
i > 20.6 mag (AB)
The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitude is not corrected for Galactic extinction.
We acknowledge the excellent support from Observatoire de Haute-Provence, in particular Jean-Pierre Troncin.
GCN Circular #33608
S. Belkin (IKI), E. Klunko (ISTP), A. Pozanenko (IKI), N. Pankov (HSE) report on behalf of GRB IKI FuN:
We observed the field of Swift GRB 230409B (Beardmore et al., GCN 33592) with AZT-33IK telescope of Mondy observatory in R-filter on 2023-04-09 starting (UT) 14:52:05. We do not detect the optical counterpart (Kuin et al., GCN 33595) within the enhanced Swift/XRT error box (Evans et al., GCN 33594). Preliminary photometry of a stacked image is following
```
Date       UT start  t-T0     Exp.  Filter   OT   Err.  UL(3sigma)
                     (mid, days)  (s)

2023-04-09  14:52:05 0.42231  26*60 R        n/d  n/d   20.5
```
The photometry is based on nearby USNO-B1.0 stars.
```
USNO-B1.0
RA DEC R2
21:58:01.9195200 +52:49:21.982800 15.15
21:58:13.7054400 +52:48:57.002400 15.56
21:57:54.5028000 +52:50:57.080400 15.95
```
The upper limit does not contradict result reported by Adami et al. (GCN 33607).
GCN Circular #33627
Rahul Gupta, Amit K. Ror, S. B. Pandey, A. Aryan, K. Misra (ARIES), A. J. Castro-Tirado (IAA-CSIC), D. Bhattacharya (Ashoka University/IUCAA), and V. Bhalerao (IITB) report on behalf of a larger collaboration:
GRB 230409B was detected by the Swift Burst Alert Telescope (BAT) at 04:56:57 UT on 9th April 2023 (Beardmore et al., GCN 33592). The prompt emission mask-weighted BAT light curve consists of a single-peaked structure with a T90 duration of 9.79 +- 2.59 sec in 15-350 keV energy range (Palmer et al., GCN 33598). We compare the reported value of BAT fluence and peak photon flux for this GRB (Palmer et al., GCN 33598) with all the BAT-detected GRBs sample; this burst is positioned at the middle-near top of this distribution. We also determine the peak energy of the burst using BAT energy fluence and peak energy correlation. We calculated the peak energy of the burst is 61.49 (+23.39, -16.96) KeV; the softer value of peak energy is consistent with those of long GRBs (Type II).
The Swift XRT detected an X-ray afterglow ~ 101.2 sec after the BAT trigger (Beardmore et al., GCN 33592). The XRT count-rate light curve could be best described with a broken power-law model with temporal indices of 0.62 (+0.12, -0.12) and 1.15 (+0.19, -0.18) before and after break time (~4600-sec post-BAT detection), respectively. As no redshift has been reported for this source, we modeled the late time time-averaged XRT spectrum (T0 + 18528 to 113195 sec) considering redshift = 2, roughly average redshift value for long GRBs (Type II). The spectrum could be modeled using an absorption power-law with the following spectral parameters: NH_host= 4.85 (-4.85,+8.76) X 10^{22} cm^{-2} and \beta_x= 0.73 (-0.36,+0.40). Considering the adiabatic deceleration without energy injection, closure relations indicate that the late time X-ray afterglow could be best described with \nu_m < \nu < \nu_c spectral regime for ISM medium for the electron energy index p ~ 2.46.
The Swift UVOT detected a weak fading source within the XRT error circle (Kuin et al., GCN 33595). We performed the follow-up observations of this fading optical source using the TANSPEC mounted at the axial port of the 3.6m Devasthal Optical Telescope (DOT) of ARIES Nainital at multiple epochs in J filter (near-infrared). We report the preliminary brightness of the afterglow to be J = 20.1 +/- 0.3 mag ~ 0.75 days after the BAT trigger. We obtained the limiting mag of 20.5 mag ~ 2.7 days post-burst at successive epochs. Our observations confirm this fading source to be the afterglow of GRB 230409B.
The magnitude values reported are calibrated against 2MASS nearby stars.
This circular may be cited. 3.6m Devasthal Optical Telescope (DOT) is the recently commissioned facility in the Northern Himalayan region of India (long:79 41 04E, lat:29 21 40N, alt:2540m) owned and operated by the Aryabhatta Research Institute of Observational Sciences (ARIES), Nainital ( https://www.aries.res.in). Authors of this GCN circular thankfully acknowledge consistent support from the staff members to run and maintain the 3.6m DOT. We also thank Director ARIES for approving the DDT slot for the ToO observations.

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Jochen Greiner, last update: 15-Apr-2023 [Disclaimer]