Gamma-ray Burst 240101A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 14:25:44 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.523d {+08d 31' 23"} (J2000)
POINT_ROLL:      247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51751.59 SOD {14:22:31.59} UT,   71832.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.212
N_STARS:         34
X_OFFSET:        655 [pixels]
Y_OFFSET:        543 [pixels]
X_MAX:           1614 [pixels]
Y_MAX:           1502 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01205708000msufc158232.fits
SUN_POSTN:       281.59d {+18h 46m 21s}  -23.01d {-23d 00' 27"}
SUN_DIST:         92.55 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.63d {+11h 02m 30s}   +9.46d {+09d 27' 36"}
MOON_DIST:       149.17 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 14:25:57 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.523d {+08d 31' 23"} (J2000)
POINT_ROLL:      247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51751.59 SOD {14:22:31.59} UT,   71832.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.212
N_STARS:         34
X_OFFSET:        655 [pixels]
Y_OFFSET:        543 [pixels]
X_MAX:           1614 [pixels]
Y_MAX:           1502 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01205708000msufc158232.fits
SUN_POSTN:       281.59d {+18h 46m 21s}  -23.01d {-23d 00' 27"}
SUN_DIST:         92.55 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.63d {+11h 02m 31s}   +9.46d {+09d 27' 33"}
MOON_DIST:       149.17 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [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:     Mon 01 Jan 24 14:27:16 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.523d {+08d 31' 23"} (J2000)
ROLL:            247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51751.59 SOD {14:22:31.59} UT,   71832.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725811784
X_OFFSET:        974 [pixels]
Y_OFFSET:        862 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1134
Y_GRB_POS:       1022
BINNING_INDEX:   1
IM_URL:          sw01205708000msuni158265.fits
SUN_POSTN:       281.59d {+18h 46m 21s}  -23.01d {-23d 00' 27"}
SUN_DIST:         92.55 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.64d {+11h 02m 33s}   +9.45d {+09d 27' 16"}
MOON_DIST:       149.18 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [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:     Mon 01 Jan 24 14:27:25 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.523d {+08d 31' 23"} (J2000)
ROLL:            247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51751.59 SOD {14:22:31.59} UT,   71832.2 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725811784
X_OFFSET:        974 [pixels]
Y_OFFSET:        862 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1134
Y_GRB_POS:       1022
BINNING_INDEX:   1
IM_URL:          sw01205708000msuni158265.fits
SUN_POSTN:       281.59d {+18h 46m 22s}  -23.01d {-23d 00' 27"}
SUN_DIST:         92.55 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.64d {+11h 02m 33s}   +9.45d {+09d 27' 14"}
MOON_DIST:       149.18 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [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:     Mon 01 Jan 24 14:33:24 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.524d {+08d 31' 28"} (J2000)
POINT_ROLL:      247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51909.60 SOD {14:25:09.60} UT,   71990.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.884
N_STARS:         54
X_OFFSET:        415 [pixels]
Y_OFFSET:        303 [pixels]
X_MAX:           1854 [pixels]
Y_MAX:           1742 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01205708000msufc158390.fits
SUN_POSTN:       281.59d {+18h 46m 23s}  -23.01d {-23d 00' 26"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.68d {+11h 02m 44s}   +9.43d {+09d 25' 55"}
MOON_DIST:       149.23 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 14:33:40 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.524d {+08d 31' 28"} (J2000)
POINT_ROLL:      247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51909.60 SOD {14:25:09.60} UT,   71990.2 [sec] since BAT Trigger Time
FILTER:          7, U
BKG_MEAN:        0.884
N_STARS:         54
X_OFFSET:        415 [pixels]
Y_OFFSET:        303 [pixels]
X_MAX:           1854 [pixels]
Y_MAX:           1742 [pixels]
DET_THRESH:      8
PHOTO_THRESH:    4
SL_URL:          sw01205708000msufc158390.fits
SUN_POSTN:       281.59d {+18h 46m 23s}  -23.01d {-23d 00' 26"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.69d {+11h 02m 45s}   +9.43d {+09d 25' 51"}
MOON_DIST:       149.23 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_srclist.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 14:34:47 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.524d {+08d 31' 28"} (J2000)
ROLL:            247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51909.60 SOD {14:25:09.60} UT,   71990.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     725811942
X_OFFSET:        974 [pixels]
Y_OFFSET:        862 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1134
Y_GRB_POS:       1022
BINNING_INDEX:   1
IM_URL:          sw01205708000msuni158423.fits
SUN_POSTN:       281.60d {+18h 46m 23s}  -23.01d {-23d 00' 25"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.69d {+11h 02m 47s}   +9.43d {+09d 25' 36"}
MOON_DIST:       149.24 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [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:     Mon 01 Jan 24 14:34:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.524d {+08d 31' 28"} (J2000)
ROLL:            247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  51909.60 SOD {14:25:09.60} UT,   71990.2 [sec] since BAT Trigger Time
FILTER:          7, U
EXPOSURE_ID:     725811942
X_OFFSET:        974 [pixels]
Y_OFFSET:        862 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1134
Y_GRB_POS:       1022
BINNING_INDEX:   1
IM_URL:          sw01205708000msuni158423.fits
SUN_POSTN:       281.60d {+18h 46m 23s}  -23.01d {-23d 00' 25"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.70d {+11h 02m 47s}   +9.43d {+09d 25' 34"}
MOON_DIST:       149.24 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.87,  3.74 [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:        If you have elected to receive attachments:  
COMMENTS:        The uvot_catalog_image.fits.gz file does not exist; skipping the attachment.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 14:40:30 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.525d {+08d 31' 29"} (J2000)
POINT_ROLL:      247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  52486.62 SOD {14:34:46.62} UT,   72567.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.381
N_STARS:         51
X_OFFSET:        415 [pixels]
Y_OFFSET:        303 [pixels]
X_MAX:           1854 [pixels]
Y_MAX:           1742 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01205708000msufc158967.fits
SUN_POSTN:       281.60d {+18h 46m 24s}  -23.01d {-23d 00' 24"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.74d {+11h 02m 57s}   +9.41d {+09d 24' 21"}
MOON_DIST:       149.28 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.88,  3.74 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Mon 01 Jan 24 14:40:38 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.525d {+08d 31' 29"} (J2000)
POINT_ROLL:      247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  52486.62 SOD {14:34:46.62} UT,   72567.3 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        3.381
N_STARS:         51
X_OFFSET:        415 [pixels]
Y_OFFSET:        303 [pixels]
X_MAX:           1854 [pixels]
Y_MAX:           1742 [pixels]
DET_THRESH:      15
PHOTO_THRESH:    8
SL_URL:          sw01205708000msufc158967.fits
SUN_POSTN:       281.60d {+18h 46m 24s}  -23.01d {-23d 00' 24"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.74d {+11h 02m 57s}   +9.41d {+09d 24' 19"}
MOON_DIST:       149.29 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.88,  3.74 [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:     Mon 01 Jan 24 14:42:09 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.525d {+08d 31' 29"} (J2000)
ROLL:            247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  52486.62 SOD {14:34:46.62} UT,   72567.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725812519
X_OFFSET:        974 [pixels]
Y_OFFSET:        862 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1134
Y_GRB_POS:       1022
BINNING_INDEX:   1
IM_URL:          sw01205708000msuni159000.fits
SUN_POSTN:       281.60d {+18h 46m 24s}  -23.01d {-23d 00' 24"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.75d {+11h 03m 00s}   +9.40d {+09d 23' 59"}
MOON_DIST:       149.30 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.88,  3.74 [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:     Mon 01 Jan 24 14:42:17 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     1205708,   Seg_Num: 0
POINT_RA:         10.374d {+00h 41m 30s} (J2000)
POINT_DEC:        +8.525d {+08d 31' 29"} (J2000)
ROLL:            247.067d
IMG_START_DATE:  20310 TJD;     1 DOY;   24/01/01
IMG_START_TIME:  52486.62 SOD {14:34:46.62} UT,   72567.3 [sec] since BAT Trigger Time
FILTER:          10, White
EXPOSURE_ID:     725812519
X_OFFSET:        974 [pixels]
Y_OFFSET:        862 [pixels]
WIDTH:           160 [pixels]
HEIGHT:          160 [pixels]
X_GRB_POS:       1134
Y_GRB_POS:       1022
BINNING_INDEX:   1
IM_URL:          sw01205708000msuni159000.fits
SUN_POSTN:       281.60d {+18h 46m 24s}  -23.01d {-23d 00' 24"}
SUN_DIST:         92.54 [deg]   Sun_angle= -5.9 [hr] (East of Sun)
MOON_POSTN:      165.75d {+11h 03m 00s}   +9.40d {+09d 23' 57"}
MOON_DIST:       149.30 [deg]
MOON_ILLUM:      73 [%]
GAL_COORDS:      118.72,-54.27 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:       12.88,  3.74 [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 #35448
S. B. Cenko (GSFC), C. Gronwall (PSU), J.D. Gropp (PSU) and K. L. Page (U Leicester) report on behalf of the Neil Gehrels Swift Observatory Team:
The Swift Burst Alert Telescope (BAT) triggered and located GRB 240101A (trigger=1205708), and Swift has slewed to this burst. The trigger time is believed to be no earlier than 12:52 UT. Given the loss of some of the TDRSS notices, we will not have values for T0 or the BAT Position until the full data have been downloaded, in approximately 1.25 hours (by around 16:05 UT).
Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 10.34819, 8.51706 which is equivalent to:
```
  RA(J2000)  = 00h 41m 23.57s
  Dec(J2000) = +08d 31' 01.4"
```
with an uncertainty of 1.9 arcseconds (radius, 90% containment). 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 (5.84 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 1.1 (+0.67/-0.52) x 10^22 cm^-2 (90% confidence).
No afterglow is detected in the initial UVOT data products.
Burst Advocate for this burst is S. B. Cenko (brad.cenko AT nasa.gov). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular #35452
A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team.
Using 885 s of XRT Photon Counting mode data and 2 UVOT images for GRB 240101A, 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 = 10.34841, +8.51582 which is equivalent to:
```
RA (J2000): 00h 41m 23.62s
Dec (J2000): +08d 30' 57.0"
```
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 #35453
WeiKang Zheng and Alexei V. Filippenko (UC Berkeley) report on
behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, responded to Swift GRB 240101A (Cenko et al.,
GCN 35448) starting at 15.57 hours after the burst. A total of
31x60s images were obtained in the clear (roughly R) filters.
We do not detect any optical afterglow candidate within the Enhanced
XRT position error circle (Beardmore et al., GCN 35452), neither in
single image, nor in the co-add images. The typical limiting magnitude
of our single clear image is about 18.5 mag calibrated to the PS1 catalog.
GCN Circular #35456
D.N. Burrows (PSU), J. D. Gropp (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), T. Sbarrato (INAF-OAB), S. Dichiara (PSU) and P.A. Evans report on behalf of the Swift-XRT team:
We have analysed 6.8 ks of XRT data for GRB 240101A, from 142 s to 57.6 ks after the BAT trigger. The data are entirely in Photon Counting (PC) mode.
The light curve can be modelled with a power-law decay with a decay index of alpha=1.06 (+0.08, -0.07).
A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.1 (+/-0.3). The best-fitting absorption column is 4.3 (+1.8, -1.5) x 10^21 cm^-2, in excess of the Galactic value of 5.8 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.9 x 10^-11 (6.5 x 10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
```
Total column:	     4.3 (+1.8, -1.5) x 10^21 cm^-2
Galactic foreground: 5.8 x 10^20 cm^-2
Excess significance: 4.1 sigma
Photon index:	     2.1 (+/-0.3)
```
If the light curve continues to decay with a power-law decay index of 1.06, the count rate at T+24 hours will be 1.4 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 5.6 x 10^-14 (9.3 x 10^-14) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01205708.
This circular is an official product of the Swift-XRT team.
GCN Circular #35457
N. P. M. Kuin (UCL-MSSL) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 240101A 168 s after the BAT trigger (Cenko et al., GCN Circ. 35448). No optical afterglow consistent with the BAT 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_FC           168          318          147         >20.4
white              168         1053          334         >20.8
v                  656         4661          236         >18.7
b                  582          773           39         >18.9
u                  729          749           19         >18.3
w1                 705         5071          236         >19.5
w2                 804          824           19         >18.7
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.059 in the direction of the burst (Schlegel et al. 1998).
GCN Circular #35460
A. Volnova (IKI), P. Phorunzij (INASAN), A. Pozanenko (IKI), N. Pankov (IKI, HSE), S. Belkin (IKI, HSE) report on behalf of GRB IKI FuN:
We observed the GRB 240101A (Cenko et al., GCN 35448) with Zeiss-2000 telescope of Terskol observatory starting on 2024-01-01 (UT) 16:10:24. Within enhanced Enhanced Swift-XRT position (Beardmore et al., GCN 35452) we do not detect any optical objects. However we marginally detected the object at coordinates (J2000) 00:41:23.50 +8:30:58.48, which is 3.4 arcsec from XRT position (Beardmore et al., GCN 35452). Preliminary photometry of the marginally detected object is following.
```
Date       UT start  t-T0     Filter Exp.    OT   Err. UL.    

                     (mid, days)      (s)         S/N 

2024-01-01 16:10:24  0.1823   R      19*60   23.7 2.0 23.0  
```
The photometry is based on the nearby PS1 stars photometry (Lupton transformations)
```
RA           Dec  c      R(Lupton)
00:41:22.24 +08:31:56.6  16.277  +/-  0.012
00:41:17.90 +08:31:41.5  18.013  +/-  0.014
```
GCN Circular #35473
A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), S. B. Cenko (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), C. B. Markwardt (GSFC), M. J. Moss (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-10 to T+242 sec from the recent telemetry downlink, we report further analysis of BAT GRB 240101A (trigger #1205708) (Cenko, et al., GCN Circ. 35448). The trigger time, which was unavailable in the first circular was 2024-01-01 at 14:20:17.331 UTC. The BAT ground-calculated position is RA, Dec = 10.289, 8.540 deg which is
```
   RA(J2000)  =  00h 41m 09.5s
   Dec(J2000) = +08d 32' 25.3"
```
with an uncertainty of 3.8 arcmin, (radius, sys+stat, 90% containment). The partial coding was 66%.
The mask-weighted light curve shows a weak, complex structure lasting from About T-5 to T+10 seconds. T90 (15-350 keV) is 15.8 +- 6.1 sec (estimated error including systematics).
The time-averaged spectrum from T-1.94 to T+20.28 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.03 +- 0.34. The fluence in the 15-150 keV band is 3.3 +- 0.7 x 10^-7 erg/cm2. The 1-sec peak photon flux measured from T+2.11 sec in the 15-150 keV band is 0.9 +- 0.2 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/1205708/BA/
GCN Circular #35486
Rahul Gupta, Amit K. Ror, Amar Aryan, and Shashi B. Pandey (ARIES) report on behalf of a larger collaboration:
We performed the optical follow-up observations of the field of new year burst GRB 240101A detected by Swift (Cenko et al. 2024, GCN 35448), utilizing the 1.3m Devasthal Fast Optical Telescope (DFOT) situated at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. Our observations started on 2024-01-01 at 15:37:15 UT, approximately 1.28 hours post-detection. Multiple frames were captured in the R filter with an exposure time of 300 seconds each. Subsequently, we aligned and stacked the images. In our stacked image, no optical afterglow was detected within the enhanced Swift-XRT error box (Beardmore et al. 2024, GCN 35452), resulting in a preliminary 3-sigma upper limit of ~ 22.4 mag. This non-detection is consistent with the observations of Zheng et al. 2024, GCN 35453; Kuin et al. 2024, GCN 35457; and Volnova et al. 2024, GCN 35460.
Additionally, we observed a potential signature of very faint optical emission at the position of the optical source reported by Volnova et al. 2024, GCN 35460. The detected faint optical source (if related) may potentially represent a candidate afterglow or the associated host galaxy of GRB 240101A. Further deep follow-up observations using larger telescopes will help to unveil the true nature of the optical source.
The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. This circular may be cited.

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Jochen Greiner, last update: 05-Jan-2024 [Disclaimer]