Gamma-ray Burst 210411C

(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 11 Apr 21 15:06:04 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1042398,   Seg_Num: 0
GRB_RA:          296.559d {+19h 46m 14s} (J2000),
                 296.919d {+19h 47m 40s} (current),
                 295.713d {+19h 42m 51s} (1950)
GRB_DEC:         -39.373d {-39d 22' 21"} (J2000),
                 -39.320d {-39d 19' 09"} (current),
                 -39.495d {-39d 29' 43"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       1092 [cnts]    Image_Peak=97 [image_cnts]
TRIGGER_DUR:     0.256 [sec] 
TRIGGER_INDEX:   120     E_range: 15-50 keV
BKG_INTEN:       21748 [cnts]
BKG_TIME:        54341.17 SOD {15:05:41.17} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19315 TJD;   101 DOY;   21/04/11
GRB_TIME:        54351.47 SOD {15:05:51.47} UT
GRB_PHI:          84.03 [deg]
GRB_THETA:        14.73 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.69 [sigma]
IMAGE_SIGNIF:    8.09 [sigma]
MERIT_PARAMS:     +1  +0  +0  -2  +1  -2  +0  +0  +0  +0 
SUN_POSTN:        20.29d {+01h 21m 11s}   +8.55d {+08d 32' 59"}
SUN_DIST:         90.34 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.81d {+01h 07m 14s}   +2.67d {+02d 39' 56"}
MOON_DIST:        83.90 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      291.30,-17.88 [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 = 195.65,5.43 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:07:13 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.575d {+19h 46m 18s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 26"} (J2000)
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54414.64 SOD {15:06:54.64} UT,   63.2 [sec] since BAT Trigger Time
COUNTS:          9    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 11 Apr 21 15:09:55 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.574d {+19h 46m 18s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 27"} (J2000)
POINT_ROLL:      79.375d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54417.83 SOD {15:06:57.83} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.756
N_STARS:         108
X_OFFSET:        370 [pixels]
Y_OFFSET:        582 [pixels]
X_MAX:           1329 [pixels]
Y_MAX:           1541 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01042398000msufc0066.fits
SUN_POSTN:        20.30d {+01h 21m 11s}   +8.55d {+08d 33' 03"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.84d {+01h 07m 21s}   +2.68d {+02d 40' 46"}
MOON_DIST:        83.92 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:10:14 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.574d {+19h 46m 18s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 27"} (J2000)
POINT_ROLL:      79.375d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54417.83 SOD {15:06:57.83} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        2.756
N_STARS:         108
X_OFFSET:        370 [pixels]
Y_OFFSET:        582 [pixels]
X_MAX:           1329 [pixels]
Y_MAX:           1541 [pixels]
DET_THRESH:      14
PHOTO_THRESH:    7
SL_URL:          sw01042398000msufc0066.fits
SUN_POSTN:        20.30d {+01h 21m 11s}   +8.55d {+08d 33' 03"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.84d {+01h 07m 21s}   +2.68d {+02d 40' 50"}
MOON_DIST:        83.93 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [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 11 Apr 21 15:11:26 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.574d {+19h 46m 18s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 27"} (J2000)
ROLL:            79.375d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54417.83 SOD {15:06:57.83} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     639846444
X_OFFSET:        689 [pixels]
Y_OFFSET:        901 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       849
Y_GRB_POS:       1061
BINNING_INDEX:   1
IM_URL:          sw01042398000msuni0093.fits
SUN_POSTN:        20.30d {+01h 21m 11s}   +8.55d {+08d 33' 04"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.85d {+01h 07m 23s}   +2.68d {+02d 41' 05"}
MOON_DIST:        83.94 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [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 11 Apr 21 15:11:34 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1042398,   Seg_Num: 0
GRB_RA:          296.559d {+19h 46m 14s} (J2000),
                 296.919d {+19h 47m 40s} (current),
                 295.713d {+19h 42m 51s} (1950)
GRB_DEC:         -39.373d {-39d 22' 21"} (J2000),
                 -39.320d {-39d 19' 09"} (current),
                 -39.495d {-39d 29' 43"} (1950)
GRB_DATE:        19315 TJD;   101 DOY;   21/04/11
GRB_TIME:        54351.47 SOD {15:05:51.47} UT
TRIGGER_INDEX:   120
GRB_PHI:          84.03 [deg]
GRB_THETA:        14.73 [deg]
DELTA_TIME:      -70.00 [sec]
TRIGGER_DUR:     0.256 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     14.69 [sigma]
IMAGE_SIGNIF:    8.09 [sigma]
LC_URL:          sw01042398000msb.lc
SUN_POSTN:        20.30d {+01h 21m 11s}   +8.55d {+08d 33' 04"}
SUN_DIST:         90.34 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.85d {+01h 07m 24s}   +2.69d {+02d 41' 07"}
MOON_DIST:        83.95 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.89 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      291.30,-17.88 [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 = 195.65,5.43 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:10:45 UT
NOTICE_TYPE:     Swift-XRT Position
TRIGGER_NUM:     1042398,   Seg_Num: 0
GRB_RA:          296.6098d {+19h 46m 26.35s} (J2000),
                 296.9692d {+19h 47m 52.60s} (current),
                 295.7636d {+19h 43m 03.27s} (1950)
GRB_DEC:         -39.3989d {-39d 23' 56.0"} (J2000),
                 -39.3455d {-39d 20' 43.8"} (current),
                 -39.5218d {-39d 31' 18.3"} (1950)
GRB_ERROR:       3.5 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54432.00 SOD {15:07:12.00} UT,   80.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        20.30d {+01h 21m 11s}   +8.55d {+08d 33' 04"}
SUN_DIST:         90.31 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.84d {+01h 07m 22s}   +2.68d {+02d 40' 56"}
MOON_DIST:        83.91 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.27,-26.93 [deg] galactic lon,lat of the burst
ECL_COORDS:      291.33,-17.91 [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 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:11:41 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.574d {+19h 46m 18s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 27"} (J2000)
ROLL:            79.375d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54417.83 SOD {15:06:57.83} UT,   66.4 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     639846444
X_OFFSET:        689 [pixels]
Y_OFFSET:        901 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       849
Y_GRB_POS:       1061
BINNING_INDEX:   1
IM_URL:          sw01042398000msuni0093.fits
SUN_POSTN:        20.30d {+01h 21m 11s}   +8.55d {+08d 33' 05"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.85d {+01h 07m 24s}   +2.69d {+02d 41' 08"}
MOON_DIST:        83.94 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [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 11 Apr 21 15:13:41 UT
NOTICE_TYPE:     Swift-UVOT Position
TRIGGER_NUM:     1042398,   Seg_Num: 0
GRB_RA:          296.6117d {+19h 46m 26.80s} (J2000),
                 296.9711d {+19h 47m 53.05s} (current),
                 295.7655d {+19h 43m 03.72s} (1950)
GRB_DEC:         -39.3977d {-39d 23' 51.7"} (J2000),
                 -39.3443d {-39d 20' 39.5"} (current),
                 -39.5206d {-39d 31' 14.0"} (1950)
GRB_ERROR:       1.1 [arcsec radius, statistical only]
GRB_MAG:         17.98 +/- 0.40 [mag]
FILTER:          10, White
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54414.00 SOD {15:06:54.00} UT,   62.5 [sec] since BAT Trigger Time
SUN_POSTN:        20.30d {+01h 21m 12s}   +8.55d {+08d 33' 06"}
SUN_DIST:         90.31 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.86d {+01h 07m 27s}   +2.69d {+02d 41' 34"}
MOON_DIST:        83.93 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.27,-26.93 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      291.33,-17.91 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        SWIFT UVOT Position Notice.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        Result based on srclist data.  
COMMENTS:        Notice generated automatically.

GCN Circular #29794
T. Sbarrato (INAF-OAB), M. G. Bernardini (INAF-OAB), P. D'Avanzo (INAF-OAB), J. A. Kennea (PSU), A. Y. Lien (GSFC/UMBC), F. E. Marshall (NASA/GSFC), A. Melandri (INAF-OAB), K. L. Page (U Leicester) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team:
At 15:05:51 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 210411C (trigger=1042398). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 296.559, -39.373 which is
```
   RA(J2000) = 19h 46m 14s
   Dec(J2000) = -39d 22' 21"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a multi-peaked structure with a duration of about 20 sec. The peak count rate was ~5500 counts/sec (15-350 keV), at ~4 sec after the trigger.
The XRT began observing the field at 15:06:54.6 UT, 63.1 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source located at RA, Dec 296.60899, -39.39786 which is equivalent to:
```
   RA(J2000)  = 19h 46m 26.16s
   Dec(J2000) = -39d 23' 52.3"
```
with an uncertainty of 3.7 arcseconds (radius, 90% containment). This location is 165 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 in excess of the Galactic value (8.10 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 3.2 (+2.66/-2.35) x 10^21 cm^-2 (90% confidence).
UVOT took a finding chart exposure of nominal 150.000 seconds with the White filter starting 66 seconds after the BAT trigger. There is a candidate afterglow in the list of sources generated on-board at
```
  RA(J2000)  =	19:46:26.83 = 296.61178
  DEC(J2000) = -39:23:51.9  = -39.39774
```
with a 90%-confidence error radius of about 1.10 arc sec. This position is 7.0 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.99. No correction has been made for the expected extinction corresponding to E(B-V) of 0.080.
Burst Advocate for this burst is T. Sbarrato (tullia.sbarrato AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:18:11 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.579d {+19h 46m 19s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 24"} (J2000)
POINT_ROLL:      79.373d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54630.04 SOD {15:10:30.04} UT,   278.6 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.830
N_STARS:         190
X_OFFSET:        130 [pixels]
Y_OFFSET:        342 [pixels]
X_MAX:           1569 [pixels]
Y_MAX:           1781 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01042398000msufc0278.fits
SUN_POSTN:        20.30d {+01h 21m 12s}   +8.55d {+08d 33' 10"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.90d {+01h 07m 36s}   +2.71d {+02d 42' 33"}
MOON_DIST:        83.99 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:18:37 UT
NOTICE_TYPE:     Swift-XRT Position UPDATE
TRIGGER_NUM:     1042398,   Seg_Num: 0
GRB_RA:          296.6116d {+19h 46m 26.78s} (J2000),
                 296.9710d {+19h 47m 53.03s} (current),
                 295.7654d {+19h 43m 03.70s} (1950)
GRB_DEC:         -39.3971d {-39d 23' 49.5"} (J2000),
                 -39.3437d {-39d 20' 37.3"} (current),
                 -39.5200d {-39d 31' 11.8"} (1950)
GRB_ERROR:       2.3 [arcsec radius, statistical plus systematic, 90% containment]
GRB_INTEN:       1.00e-10 [erg/cm2/sec]
GRB_SIGNIF:      10.00 [sigma]
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54432.00 SOD {15:07:12.00} UT,   80.5 [sec] since BAT Trigger Time
TAM[0-3]:        100.00 100.00 100.00 100.00
AMPLIFIER:       1
WAVEFORM:        31
SUN_POSTN:        20.30d {+01h 21m 12s}   +8.55d {+08d 33' 11"}
SUN_DIST:         90.31 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.90d {+01h 07m 36s}   +2.71d {+02d 42' 39"}
MOON_DIST:        83.97 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.27,-26.93 [deg] galactic lon,lat of the burst
ECL_COORDS:      291.33,-17.91 [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 0.11% < P(seren) < 0.58%.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:19:38 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.579d {+19h 46m 19s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 24"} (J2000)
ROLL:            79.373d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54630.04 SOD {15:10:30.04} UT,   278.6 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     639846656
X_OFFSET:        689 [pixels]
Y_OFFSET:        901 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       849
Y_GRB_POS:       1061
BINNING_INDEX:   1
IM_URL:          sw01042398000msuni0305.fits
SUN_POSTN:        20.30d {+01h 21m 13s}   +8.55d {+08d 33' 12"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.91d {+01h 07m 38s}   +2.71d {+02d 42' 52"}
MOON_DIST:        84.00 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [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 11 Apr 21 15:18:33 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.579d {+19h 46m 19s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 24"} (J2000)
POINT_ROLL:      79.373d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54630.04 SOD {15:10:30.04} UT,   278.6 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.830
N_STARS:         190
X_OFFSET:        130 [pixels]
Y_OFFSET:        342 [pixels]
X_MAX:           1569 [pixels]
Y_MAX:           1781 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01042398000msufc0278.fits
SUN_POSTN:        20.30d {+01h 21m 12s}   +8.55d {+08d 33' 11"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.90d {+01h 07m 36s}   +2.71d {+02d 42' 38"}
MOON_DIST:        83.99 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [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 11 Apr 21 15:19:50 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.579d {+19h 46m 19s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 24"} (J2000)
ROLL:            79.373d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  54630.04 SOD {15:10:30.04} UT,   278.6 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     639846656
X_OFFSET:        689 [pixels]
Y_OFFSET:        901 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       849
Y_GRB_POS:       1061
BINNING_INDEX:   1
IM_URL:          sw01042398000msuni0305.fits
SUN_POSTN:        20.30d {+01h 21m 13s}   +8.55d {+08d 33' 12"}
SUN_DIST:         90.33 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       16.91d {+01h 07m 39s}   +2.72d {+02d 42' 54"}
MOON_DIST:        84.00 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [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 11 Apr 21 15:41:07 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.579d {+19h 46m 19s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 25"} (J2000)
POINT_ROLL:      79.373d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  55208.58 SOD {15:20:08.58} UT,   857.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.196
N_STARS:         190
X_OFFSET:        130 [pixels]
Y_OFFSET:        342 [pixels]
X_MAX:           1569 [pixels]
Y_MAX:           1781 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01042398000msufc0857.fits
SUN_POSTN:        20.32d {+01h 21m 16s}   +8.56d {+08d 33' 31"}
SUN_DIST:         90.35 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       17.07d {+01h 08m 17s}   +2.79d {+02d 47' 31"}
MOON_DIST:        84.17 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Sun 11 Apr 21 15:41:21 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1042398,   Seg_Num: 0
POINT_RA:        296.579d {+19h 46m 19s} (J2000)
POINT_DEC:       -39.374d {-39d 22' 25"} (J2000)
POINT_ROLL:      79.373d
IMG_START_DATE:  19315 TJD;   101 DOY;   21/04/11
IMG_START_TIME:  55208.58 SOD {15:20:08.58} UT,   857.1 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.196
N_STARS:         190
X_OFFSET:        130 [pixels]
Y_OFFSET:        342 [pixels]
X_MAX:           1569 [pixels]
Y_MAX:           1781 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01042398000msufc0857.fits
SUN_POSTN:        20.32d {+01h 21m 16s}   +8.56d {+08d 33' 32"}
SUN_DIST:         90.35 [deg]   Sun_angle= 5.6 [hr] (West of Sun)
MOON_POSTN:       17.07d {+01h 08m 18s}   +2.79d {+02d 47' 34"}
MOON_DIST:        84.17 [deg]
MOON_ILLUM:      0 [%]
GAL_COORDS:        0.29,-26.90 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      291.31,-17.88 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN Circular #29800
M.R. Goad, J.P. Osborne, A.P. Beardmore and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team.
Using 318 s of XRT Photon Counting mode data and 1 UVOT images for GRB 210411C, 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 = 296.61122, -39.39793 which is equivalent to:
```
RA (J2000): 19h 46m 26.69s
Dec (J2000): -39d 23' 52.6"
```
with an uncertainty of 2.0 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 #29802
R. Strausbaugh (U. of the Virgin Islands), A. Cucchiara (U. of the Virgin Islands/College of Marin) report on behalf of a larger collaboration:
We observed Swift GRB 210411C (Sbarrato, GCN 29794) with the LCO 1-m Sinistro instrument at the Siding Spring Observatory, Australia site, on April 11, from 16:18 to 16:42 UT (corresponding to 1.22 to 1.62 hours from the GRB trigger time) with the Bessel R and I filters.
We performed a series of 4x180s exposures in R and I. We detect an optical source in R and I band images at a location consistent the initial UVOT detection (Sbarrato, GCN 29794) and enhanced XRT position (Goad, GCN 29800), that is not present in either USNO or 2MASS catalogs. Using the USNO-B.1 catalog as reference, we calculate the following magnitudes:
R = 18.51 +/- 0.03
I = 18.01 +/- 0.03
These magnitudes are not corrected for galactic extinction. These magnitudes may also be contaminated by a bright foreground star.
R.S. is funded by NSF AST grant #1831682
GCN Circular #29803
Y.-D. Hu, E. Fernandez-Garcia, A. J. Castro-Tirado, M. D. Caballero-Garcia, M. A. Castro Tirado (IAA-CSIC), C. Perez del Pulgar (Univ. de Malaga), S. Guziy (Univ. of Nikolaev) and D. R. Xiong, Y. F. Fan, J. M. Bai, C. J. Wang, Y. X. Xin, X. H. Zhao (Yunnan Observatories of CAS) on behalf of a larger collaboration, report:
Following the detection of GRB 210406A by Swift (Sbarrato et al. GCNC 29794), follow-up observations at the 0.6m BOOTES-4/MET robotic telescope in Lijiang Astronomical Observatory (China) were performed starting on Apr 11, 20:52 UT (~5.8 hr after trigger) at high airmass. No new source is detected down to 19.6 mag at the optical afterglow position reported by UVOT (Sbarrato et al. GCNC 29794) and the 1.0m LCO in Siding Spring (Strausbaugh et al. GCNC 29802) in our co-added image (25x60 s, clear filter) confirming the fading in the optical range.
We thank the staff at Lijiang observatory for their excellent support.
GCN Circular #29804
V. Lipunov, E. Gorbovskoy, V.Kornilov, N.Tyurina, P.Balanutsa, A.Kuznetsov, F.Balakin, V.Vladimirov, D. Vlasenko, I.Gorbunov, D.Zimnukhov, V.Senik, T.Pogrosheva, D.Kuvshinov, D. Cheryasov (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, O.Ershova (Irkutsk State University, API),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
V. Yurkov, A. Gabovich, Yu. Sergienko (Blagoveschensk Educational State University)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 210411C ( T. Sbarrato et al., GCN 29794) errorbox 60730 sec after notice time and 60747 sec after trigger time at 2021-04-12 07:58:18 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 37 deg. The sun altitude is -38.0 deg.
The galactic latitude b = -27 deg., longitude l = 1 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1589515
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   60837 |         MASTER-OAFA |   C |   180 | 19.0 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #29806
A. de Ugarte Postigo (HETH/IAA-CSIC and DARK/NBI), B. Sbarufatti (PSU), D. Xu (NAO/CAS), J.-B. Vielfaure (APC, Paris University), D. B. Malesani (DTU Space), D. A. Kann (HETH/IAA-CSIC) V. D'Elia (ASI/SSDC, INAF/OAR), P. J. Pessi (FCAG/ESO), report on behalf of the Stargate consortium:
We observed the optical afterglow of GRB 210411C (Sbarrato et al., GCN 29794) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures by 1200 s each (8x600 s in the NIR). The observation mid time was 2021 Apr 12.33 UT (16.9 hr after the GRB).
In a 60 s image taken with the acquisition camera on Apr 12.294 UT, we detect the optical afterglow, for which we measure an AB magnitude r = 21.69 +- 0.04 (calibrated against nearby stars from the SkyMapper catalog; Wolf et al. 2018, PASA, 35, 010; https:doi.org/10.4225/41/593620ad5b574).
We clearly detect continuum over the wavelength range 3520 - 17500 AA. A trough is visible around 4650 AA, which we identify as due to H I. From the detection of several narrow absorption features, which we interpret as due to, among others, Si II, Si II*, O I, C II, Si IV, C IV, Fe II, Al II, we infer a redshift z = 2.826. We also identify the FeII* 2396 fine-structure transition, though at low S/N.
We acknowledge excellent support from the observing staff at Paranal, in particular Eleonora Sani and Bin Yang.
GCN Circular #29807
J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), P.A. Evans (U. Leicester), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A. Melandri (INAF-OAB), P. D'Avanzo (INAF-OAB) and T. Sbarrato report on behalf of the Swift-XRT team:
We have analysed 6.4 ks of XRT data for GRB 210411C (Sbarrato et al. GCN Circ. 29794), from 66 s to 42.0 ks after the BAT trigger. The data comprise 136 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The enhanced XRT position for this burst was given by Goad et al. (GCN Circ. 29800).
The late-time light curve (from T0+5.4 ks) can be modelled with a power-law decay with a decay index of alpha=1.49 (+/-0.17).
A spectrum formed from the WT mode data can be fitted with an absorbed power-law with a photon spectral index of 2.66 (+0.19, -0.18). The best-fitting absorption column is 1.2 (+0.4, -0.3) x 10^21 cm^-2, in excess of the Galactic value of 8.1 x 10^20 cm^-2 (Willingale et al. 2013). The PC mode spectrum has a photon index of 1.84 (+0.14, -0.11) and a best-fitting absorption column of 9.4 (+4.0, -1.3) x 10^20 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (4.3 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     9.4 (+4.0, -1.3) x 10^20 cm^-2
Galactic foreground: 8.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index:	     1.84 (+0.14, -0.11)
```
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01042398.
This circular is an official product of the Swift-XRT team.
GCN Circular #29808
P. Pessi (ESO), G. Csoernyei, A. Holas, S. Taubenberger, C. Vogl (MPA Garching), A. Floers (GSI), G. Pignata (UNAB), J. Teffs (Liverpool), M. Dennefeld (IAP), D. B. Malesani (DTU Space), P. D'Avanzo (INAF/Brera), J. Anderson (ESO), T. M�ller Bravo (Southampton), T.-W. Chen (Stockholm), M. Gromadzki (Warsaw), C. Inserra (Cardiff), E. Kankare (Turku), M. Nicholl (Birmingham), O. Yaron (Weizmann), D. Young (QUB), E. Zimmerman (Weizmann) report:
We observed the optical afterglow of GRB 210411C (Sbarrato et al., GCN 29794; Strausbaugh & Cucchiara, GCN 29802; de Ugarte Postigo et al., GCN 29806) under the the advanced Public ESO Spectroscopic Survey for Transient Objects (ePESSTO+; see Smartt et al. 2015, A&A, 579, 40 and http://www.pessto.org ). The observations were performed on the ESO New Technology Telescope (NTT) at La Silla with the EFOSC2 instrument. A single 5-min exposure was acquired in the Gunn r filter, with mean epoch 2021 Apr 12.234 UT (14.55 hr after the GRB).
The optical afterglow is well detected and we report the following coordinates (calibrated against the Gaia catalog):
```
RA = 19:46:26.83
Dec = -39:23:52.7
```
For the afterglow, we measure a magnitude R = 21.28 +- 0.04 (Vega), assuming R = 17.31 for the USNO star at RA = 19:46:25.68, Dec = -39:23:48.9 . An extra uncertainty of ~0.3 mag should be added to account for the photometric calibration error of the USNO catalog.
GCN Circular #29809
S. Belkin (IKI), A. Pozanenko (IKI), M. Krugov (AFIF), N. Pankov (HSE) report on behalf of IKI-FuN follow-up collaboration:
We observed the Swift GRB 210411C (Sbarrato et al., GCN 29794) with Chilescope RC-1000 started on April 12 (UT) 07:43:39 in r'-filter. We clearly detected optical afterglow (Sbarrato et al., GCN 29794; Strausbaugh et al., GCN 29802; Hu et al., GCN 29803; Lipunov et al., GCN 29804; de Ugarte Postigo et al., GCN 29806; Pessi et al., GCN 29808) in a stacked image with a total exposure of 3*600 seconds.
Preliminary photometry is following.
```
Date       UT start   t-T0       Filter Exp.   OT    Err.  UL(3sigma)
                      (mid, days)        (s)
2021-04-12 07:43:39   0.70333    r'     3*600  21.76 0.16  22.4
```
The photometry is based on nearby stars from the SkyMapper catalog
```
SMSS-DR1.1_id r
194633.88-392221.5 17.428
194648.73-392400.2 16.180
```
GCN Circular #29810
C. B. Markwardt (GSFC), S. D. Barthelmy (GSFC), J. R. Cummings (CPI), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC), D. M. Palmer (LANL), T. Sakamoto (AGU), T. Sbarrato (INAF-OAB), M. Stamatikos (OSU), T. N. Ukwatta (LANL) (i.e. the Swift-BAT team):
Using the data set from T-60 to T+243 sec from the recent telemetry downlink, we report further analysis of BAT GRB 210411C (trigger #1042398) (Sbarrato et al., GCN Circ. 29794). The BAT ground-calculated position is RA, Dec = 296.601, -39.399 deg which is
```
   RA(J2000)  =  19h 46m 24.2s
   Dec(J2000) = -39d 23' 57.8"
```
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 79%.
The mask-weighted light curve shows a multi-peaked structure that starts at ~T0 and ends at ~T+17 s. The two major peaks occur at ~T+4 s and ~T+11 s, respectively. T90 (15-350 keV) is 12.80 +- 0.60 sec (estimated error including systematics).
The time-averaged spectrum from T-0.45 to T+14.44 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.60 +- 0.40, and Epeak of 14.8 +- 10.8 keV (chi squared 51.24 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.1 x 10^-6 erg/cm2 and the 1-sec peak flux measured from T+3.87 sec in the 15-150 keV band is 4.8 +- 0.3 ph/cm2/sec. A fit to a simple power law gives a photon index of 2.62 +- 0.09 (chi squared 68.87 for 57 d.o.f.). 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/1042398/BA/
GCN Circular #29811
N. P. M. Kuin (UCL-MSSL) and Sbarrato (INAF-OAB) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210411C 66 s after the BAT trigger (Sbarrato et al., GCN Circ. 29794). A source consistent with the XRT position (Goad et al. GCN Circ. 29800) is detected in the initial UVOT exposures. Further detections were reported by Strausbaugh et al. (GCN Circ 29802)
The preliminary UVOT position is:
```
    RA  (J2000) =  19:46:26.81 = 296.61170 (deg.)
    Dec (J2000) = -39:23:52.2  = -39.39784 (deg.)
```
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
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               66          216          147         17.16 +/- 0.03
v                  609          801           39         17.43 +/- 0.18
b                  535          555           20         17.82 +/- 0.17
u                  279          528          246         17.82 +/- 0.07
w1                 658         1280           78        >19.7
m2                 633         5836           83        >19.6
w2                 584         5600          255        >20.1
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.081 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #29823
Y. Aimuratov, C.L. Bianco, L. Li, R. Moradi, F. Rastegar Nia, J.A. Rueda, R. Ruffini, N. Sahakyan, Y. Wang, S.S. Xue on behalf of the ICRANet team, report:
GRB 210411C (trigger=1042398) with a redshift z=2.826 (A. de Ugarte Postigo et al, 2021, GCN29806) was triggered and located by Swift Burst Alert Telescope (BAT) (T. Sbarrato et al, 2021, GCN 29794) with T90=12.8 sec in 15-150 keV (C. B. Markwardt et al, 2021, GCN29810).
The corresponding luminosity light curves of Swift-BAT and Swift-XRT (J.D. Gropp et al, 2021, GCN29807) show this source is a twin of GRB 190114C (Ruffini et al, 2021, https://doi.org/10.1093/mnras/stab724). A new additional feature is identified in the early luminosity of Swift-XRT data of GRB 210411C (see enclosed Fig.1).
We recommend to check for the possible existence of a yet unobserved GeV radiation and to follow up the late keV and possible GeV temporal power-law luminosities.
Fig. 1: http://www.icranet.org/documents/Swift_GRB210411C-Fermi_GRB190114C.pdf

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Jochen Greiner, last update: 16-Apr-2021 [Disclaimer]