Gamma-ray Burst 220412B

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN/BACODINE POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:07:01 UT
NOTICE_TYPE:     Swift-BAT GRB Position
TRIGGER_NUM:     1102329,   Seg_Num: 0
GRB_RA:          320.794d {+21h 23m 11s} (J2000),
                 321.080d {+21h 24m 19s} (current),
                 320.153d {+21h 20m 37s} (1950)
GRB_DEC:          -0.223d {-00d 13' 23"} (J2000),
                  -0.127d {-00d 07' 36"} (current),
                  -0.438d {-00d 26' 16"} (1950)
GRB_ERROR:       3.00 [arcmin radius, statistical only]
GRB_INTEN:       515 [cnts]    Image_Peak=72 [image_cnts]
TRIGGER_DUR:     0.032 [sec] 
TRIGGER_INDEX:   10318     E_range: 25-100 keV
BKG_INTEN:       20833 [cnts]
BKG_TIME:        61595.04 SOD {17:06:35.04} UT
BKG_DUR:         8 [sec]
GRB_DATE:        19681 TJD;   102 DOY;   22/04/12
GRB_TIME:        61608.80 SOD {17:06:48.80} UT
GRB_PHI:          36.78 [deg]
GRB_THETA:        23.06 [deg]
SOLN_STATUS:     0x3
RATE_SIGNIF:     46.56 [sigma]
IMAGE_SIGNIF:    8.88 [sigma]
MERIT_PARAMS:     +1  +0  +0  -5  +2  -1  +0  +0 -49  +0 
SUN_POSTN:        21.07d {+01h 24m 17s}   +8.86d {+08d 51' 25"}
SUN_DIST:         60.41 [deg]   Sun_angle= 4.0 [hr] (West of Sun)
MOON_POSTN:      155.47d {+10h 21m 53s}  +15.72d {+15d 43' 10"}
MOON_DIST:       158.91 [deg]
MOON_ILLUM:      81 [%]
GAL_COORDS:       52.27,-33.29 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      323.11, 14.35 [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 = 262.42,-16.46 [deg].

red DSS finding chart ps-file

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:08:21 UT
NOTICE_TYPE:     Swift-XRT Nack-Position
TRIGGER_NUM:     1102329,   Seg_Num: 0
POINT_RA:        320.805d {+21h 23m 13s} (J2000)
POINT_DEC:        -0.224d {-00d 13' 24"} (J2000)
IMG_START_DATE:  19681 TJD;   102 DOY;   22/04/12
IMG_START_TIME:  61693.77 SOD {17:08:13.77} UT,   85.0 [sec] since BAT Trigger Time
COUNTS:          12    Min_needed= 20
STD_DEV:         0.00   Max_StdDev_for_Good=28.44 [arcsec]
PH2_ITER:        1    Max_iter_allowed= 4
ERROR_CODE:      1
COMMENTS:        SWIFT-XRT Nack Position.  
COMMENTS:        No source found in the image.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:10:58 UT
NOTICE_TYPE:     Swift-BAT GRB Lightcurve
TRIGGER_NUM:     1102329,   Seg_Num: 0
GRB_RA:          320.794d {+21h 23m 11s} (J2000),
                 321.080d {+21h 24m 19s} (current),
                 320.153d {+21h 20m 37s} (1950)
GRB_DEC:          -0.223d {-00d 13' 23"} (J2000),
                  -0.127d {-00d 07' 36"} (current),
                  -0.438d {-00d 26' 16"} (1950)
GRB_DATE:        19681 TJD;   102 DOY;   22/04/12
GRB_TIME:        61609.03 SOD {17:06:49.03} UT
TRIGGER_INDEX:   10318
GRB_PHI:          36.78 [deg]
GRB_THETA:        23.06 [deg]
DELTA_TIME:      42.00 [sec]
TRIGGER_DUR:     0.032 [sec] 
SOLN_STATUS:     0x3
RATE_SIGNIF:     46.56 [sigma]
IMAGE_SIGNIF:    8.88 [sigma]
LC_URL:          sw01102329000msb.lc
SUN_POSTN:        21.07d {+01h 24m 17s}   +8.86d {+08d 51' 29"}
SUN_DIST:         60.41 [deg]   Sun_angle= 4.0 [hr] (West of Sun)
MOON_POSTN:      155.51d {+10h 22m 01s}  +15.71d {+15d 42' 22"}
MOON_DIST:       158.89 [deg]
MOON_ILLUM:      81 [%]
GAL_COORDS:       52.27,-33.29 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      323.11, 14.35 [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 = 262.42,-16.46 [deg].

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:11:58 UT
NOTICE_TYPE:     Swift-UVOT Source List
TRIGGER_NUM:     1102329,   Seg_Num: 0
POINT_RA:        320.805d {+21h 23m 13s} (J2000)
POINT_DEC:        -0.224d {-00d 13' 24"} (J2000)
POINT_ROLL:      79.722d
IMG_START_DATE:  19681 TJD;   102 DOY;   22/04/12
IMG_START_TIME:  61698.00 SOD {17:08:18.00} UT,   89.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.123
N_STARS:         40
X_OFFSET:        401 [pixels]
Y_OFFSET:        587 [pixels]
X_MAX:           1360 [pixels]
Y_MAX:           1546 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw01102329000msufc0089.fits
SUN_POSTN:        21.07d {+01h 24m 17s}   +8.86d {+08d 51' 30"}
SUN_DIST:         60.40 [deg]   Sun_angle= 4.0 [hr] (West of Sun)
MOON_POSTN:      155.51d {+10h 22m 03s}  +15.70d {+15d 42' 10"}
MOON_DIST:       158.90 [deg]
MOON_ILLUM:      81 [%]
GAL_COORDS:       52.28,-33.30 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      323.13, 14.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Source List.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:12:12 UT
NOTICE_TYPE:     Swift-UVOT Processed Source List
TRIGGER_NUM:     1102329,   Seg_Num: 0
POINT_RA:        320.805d {+21h 23m 13s} (J2000)
POINT_DEC:        -0.224d {-00d 13' 24"} (J2000)
POINT_ROLL:      79.722d
IMG_START_DATE:  19681 TJD;   102 DOY;   22/04/12
IMG_START_TIME:  61698.00 SOD {17:08:18.00} UT,   89.2 [sec] since BAT Trigger Time
FILTER:          10, White
BKG_MEAN:        5.123
N_STARS:         40
X_OFFSET:        401 [pixels]
Y_OFFSET:        587 [pixels]
X_MAX:           1360 [pixels]
Y_MAX:           1546 [pixels]
DET_THRESH:      19
PHOTO_THRESH:    11
SL_URL:          sw01102329000msufc0089.fits
SUN_POSTN:        21.07d {+01h 24m 17s}   +8.86d {+08d 51' 30"}
SUN_DIST:         60.40 [deg]   Sun_angle= 4.0 [hr] (West of Sun)
MOON_POSTN:      155.52d {+10h 22m 04s}  +15.70d {+15d 42' 07"}
MOON_DIST:       158.90 [deg]
MOON_ILLUM:      81 [%]
GAL_COORDS:       52.28,-33.30 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:      323.13, 14.35 [deg] ecliptic lon,lat of the pointing direction
COMMENTS:        SWIFT-UVOT Processed Source List.  
COMMENTS:        All 4 attachments are included.

GCN NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:14:50 UT
NOTICE_TYPE:     Swift-UVOT Image
TRIGGER_NUM:     14532607,   Seg_Num: 0
POINT_RA:          0.000d {+00h 00m 00s} (J2000)
POINT_DEC:        +0.000d {+00d 00' 00"} (J2000)
ROLL:            0.000d
IMG_START_DATE:  34893 TJD;   15314 DOY;   22/34/5894495
IMG_START_TIME:  9601.14 SOD {02:40:01.14} UT,   34392.3 [sec] since BAT Trigger Time
FILTER:          0, illegal value
EXPOSURE_ID:     91828096
X_OFFSET:        0 [pixels]
Y_OFFSET:        487 [pixels]
WIDTH:           1440 [pixels]
HEIGHT:          2015 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       128
BINNING_INDEX:   0
IM_URL:          sw01102329000msuni0118.fits
SUN_POSTN:        21.07d {+01h 24m 18s}   +8.86d {+08d 51' 33"}
SUN_DIST:         21.89 [deg]   Sun_angle= 1.4 [hr] (West of Sun)
MOON_POSTN:      155.54d {+10h 22m 09s}  +15.69d {+15d 41' 36"}
MOON_DIST:       150.32 [deg]
MOON_ILLUM:      81 [%]
GAL_COORDS:       96.34,-60.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        0.00,  0.00 [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 1x1 binning (ie no compression).  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN POSITION NOTICE

TITLE:           GCN/SWIFT NOTICE
NOTICE_DATE:     Tue 12 Apr 22 17:14:56 UT
NOTICE_TYPE:     Swift-UVOT Processed Image
TRIGGER_NUM:     14532607,   Seg_Num: 0
POINT_RA:          0.000d {+00h 00m 00s} (J2000)
POINT_DEC:        +0.000d {+00d 00' 00"} (J2000)
ROLL:            0.000d
IMG_START_DATE:  34893 TJD;   15314 DOY;   22/44/5894495
IMG_START_TIME:  9601.14 SOD {02:40:01.14} UT,   34392.3 [sec] since BAT Trigger Time
FILTER:          0, illegal value
EXPOSURE_ID:     91828096
X_OFFSET:        0 [pixels]
Y_OFFSET:        487 [pixels]
WIDTH:           1440 [pixels]
HEIGHT:          2015 [pixels]
X_GRB_POS:       0
Y_GRB_POS:       128
BINNING_INDEX:   0
IM_URL:          sw01102329000msuni0118.fits
SUN_POSTN:        21.07d {+01h 24m 18s}   +8.86d {+08d 51' 33"}
SUN_DIST:         21.89 [deg]   Sun_angle= 1.4 [hr] (West of Sun)
MOON_POSTN:      155.54d {+10h 22m 09s}  +15.69d {+15d 41' 34"}
MOON_DIST:       150.32 [deg]
MOON_ILLUM:      81 [%]
GAL_COORDS:       96.34,-60.19 [deg] galactic lon,lat of the pointing direction
ECL_COORDS:        0.00,  0.00 [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 1x1 binning (ie no compression).  
COMMENTS:        All 4 attachments are included.  
COMMENTS:        This notice was forced out after watchdog timer expiring -- most likely due to missing packet(s);  
COMMENTS:        as a consequence some of the fields may be incoorect (eg TRIGGER_NUM,RA,DEC).

GCN Circular #31886
J.D. Gropp (PSU), S. Dichiara (PSU), J. A. Kennea (PSU), N. J. Klingler (GSFC/UMBC/CRESSTII), F. E. Marshall (NASA/GSFC), K. L. Page (U Leicester), T. M. Parsotan (GSFC/UMBC/CRESSTII), B. Sbarufatti (PSU) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team:
At 17:06:49 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 220412B (trigger=1102329). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 320.794, -0.223 which is
```
   RA(J2000) = 21h 23m 11s
   Dec(J2000) = -00d 13' 23"
```
with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a single-peaked structure with a duration of about 0.5 sec. The peak count rate was ~6000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 17:08:13.7 UT, 85.0 seconds after the BAT trigger. No source was detected in the 2.5-s promptly available image. We are waiting for the full dataset to detect and localise the XRT counterpart.
UVOT took a finding chart exposure of 130 seconds with the White filter starting 89 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 25% of the BAT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the BAT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.060.
Shortly after the BAT trigger, Swift entered the South Atlantic Anomaly which limited data collection for the first orbit. We are awaiting further observations.
Burst Advocate for this burst is J.D. Gropp (jdg44 AT psu.edu). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular #31889
K. L. Murata, M. Niwano, Y. Imai, N. Ito, Y. Takamatsu, S. Sato, R. Hosokawa, M. Sasada, Y. Yatsu, and N. Kawai (Tokyo Tech) report on behalf of the MITSuME collaboration:
We observed the field of GRB 220412B (Gropp et al. GCN Circular #31886) with the optical three color (g', Rc, and Ic) CCD cameras attached to the MITSuME 50 cm telescope Akeno. The observation with a series of 60 sec exposures started at 2022-04-12 18:28:16 UT (82 minutes after the Swift/BAT trigger). We stacked the images with good conditions. We did not detect any uncatalogued sources within the BAT error region (Gropp et al. GCN Circular #31886). We obtained the 5-sigma limits of the stacked images as follows.
```
T0+[min] MID-UT T-EXP[sec] 5-sigma limits
------------------------------------------------------------------------------------------------
82 2022-04-12 18:55:21 2820 g'>17.9, Rc>19.0, Ic>18.5
------------------------------------------------------------------------------------------------
T0+ : Elapsed time after the burst
T-EXP: Total Exposure time
```
We used the PS1 catalog for flux calibration. The magnitudes are expressed in the AB system. The images were processed in real-time through the MITSuME GPU reduction pipeline (Niwano et al. 2021, PASJ, Vol.73, Issue 1, Pages 4-24; https://github.com/MNiwano/Eclaire).
GCN Circular #31892
H. Kumar (IITB), V. Swain (IITB), R. Norbu (IAO), G. C. Anupama (IIA), V. Bhalerao (IITB), S. Barway (IIA) report on behalf of the GIT team:
We observed the short GRB 220412B detected by Swift-BAT (J.D. Gropp et al., GCN #31886) with the 0.7m *GROWTH-India Telescope* (GIT). We obtained multiple 300-sec exposures in the r' filter. We did not detect any new source in our stacked image within the BAT uncertainty region of 3 arcmin circle, around R.A.= 320.794, DEC.= -0.223. The obtained upper limit follows as:
-------------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Exposure (sec) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------------
2459682.452891 | 5.75 | 300 x 6 (stacked) | r' | > 20.25 |
-------------------------------------------------------------------------
Our upper limit is consistent with results from K. L. Murata et al. (GCN #31889). The magnitudes are calibrated against Pan-STARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/.
GCN Circular #31894
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-OAGH robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the Swift GRB 220412B ( J.D. Gropp et al., GCN 31886) errorbox 61446 sec after notice time and 61475 sec after trigger time at 2022-04-13 10:11:24 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 77 deg. The sun altitude is -32.6 deg.
The galactic latitude b = -34 deg., longitude l = 53 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=1940975
We obtain a following upper limits.
```
Tmid-T0  |          Site       |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________

   61505 |         MASTER-OAGH |   C |    60 | 17.5 |        
   61505 |         MASTER-OAGH |   C |    60 | 17.3 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #31897
V. D'Elia (SSDC & INAF-OAR), A. D'Ai (INAF-IASFPA), J. D. Gropp (PSU), J.A. Kennea (PSU), A. Tohuvavohu (U. Toronto), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), A. Melandri (INAF-OAB) and J.D. Gropp (PSU) report on behalf of the Swift-XRT team:
We have analysed 7.8 ks of Photon Counting (PC) mode XRT data for the Swift-BAT-detected burst GRB 220412B (Gropp et al. GCN Circ. 31886), collected between T0+4.7 ks and T0+29.1 ks.
No X-ray sources have been detected consistent with being within 296 arcsec of the Swift-BAT position. The 3-sigma upper limit in the field is 0.001 ct s^-1, corresponding to a 0.3-10 keV observed flux of 4.2e-14 erg cm^-2 s^-1 (assuming a typical GRB spectrum).
Four uncatalogued sources were detected too far from the GRB position to be likely afterglow candidates.
The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/01102329.
This circular is an official product of the Swift-XRT team.
GCN Circular #31900
Y.-D. Hu, E. Fernandez-Garcia, T.-R. Sun, A. J. Castro-Tirado, M. D. Caballero-Garcia, R. Sanchez-Ramirez (IAA-CSIC), C. Perez del Pulgar, A. Castellon, I. Carrasco, A. Reina (Univ. de Malaga) and F. Rendon (IAA-CSIC and INTA-CEDEA) on behalf of a larger collaboration, report:
Following the detection of short GRB 220412B by Swift (Gropp et al., GCNC 31886), the 0.3m BOOTES-1B robotic telescope in Mazagon (Huelva), southern Spain, automatically responded to this burst on Apr 13 at 03:46 UT (~10.7 hours after trigger). In the co-added frame (45 x 60 s, clear filter), no source is detected within the BAT error box (Gropp et al., GCNC 31886) down to 18.8 mag, which is consistent with the non-detections reported by UVOT (Gropp et al., GCNC 31886), MITSuME (Murata et al. GCNC 31889), GIT (Kumar et al. GCNC 31892) and MASTER (Lipunov et al., GCNC 31894).
We thank the staff at INTA-CEDEA for their excellent support.
GCN Circular #31904
P. D'Avanzo (INAF-OAB), S. Piranomonte (INAF-OAR), L. Di Fabrizio, H. Stoev (INAF-TNG) on behalf of the CIBO collaboration report:
We observed the field of the short GRB 220412B (Gropp et al. GCN Circ. 31886) with the Italian 3.6m TNG telescope equipped with the optical camera DOLORES. A series of images were obtained with the r-sdss filter on 2022-04-13 from 04:42:48 UT to 05:26:37 UT (i.e. at a mid time of about 12 hours after the burst).
No clear afterglow candidate is detected within the BAT error (Gropp et al. GCN Circ. 31886). The typical 3sigma limiting magnitude of our co-added image for isolated objects is r ~ 24.2 mag (AB; calibrated against the SDSS catalogue).
GCN Circular #31908
P. Veres and C. Meegan (both UAH) report on behalf of the Fermi GBM Team:
"At 17:06:49.04 UT on 12 April 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220412B (trigger 671476014 / 220412713) which was also detected by the Swift/BAT (Gropp et al., GCN 31886). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 20 degrees.
The GBM light curve consists of a single pulse with a duration (T90) of about 0.16 s (50-300 keV). The time-averaged spectrum from T0-32 ms to T0+96 ms is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.70 +/-0.14 and the cutoff energy, parameterized as Epeak, is 499 +/- 116 keV.
The event fluence (10-1000 keV) in this time interval is (4.44 +/- 0.40)E-7 erg/cm^2. The 64-ms peak photon flux measured starting from T0 in the 10-1000 keV band is 17.2 +/- 1.2 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular #31909
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The short-duration GRB 220412B (Swift-BAT detection: Gropp et al., GCN Circ. 31886; Fermi-GBM observation: Veres and Meegan, GCN Circ. 31908) triggered Konus-Wind at T0=26885.231 s UT (07:28:05.231).
The burst light curve shows a single pulse with a total duration of ~86 ms.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB220412_T61606/
As observed by Konus-Wind, the burst had a fluence of 3.2(-0.1,+1.2)x10^-7 erg/cm2, and a 16-ms peak flux, measured from T0-42 ms, of 1.1(-0.1,+0.4)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
Since the main fraction of the burst emission was detected before the trigger, the spectral analysis was performed using the KW 3-channel light curve data.
Modelling the KW 3-channel time-integrated spectrum (measured from T0-52 ms to T0+34 ms) by a power law with exponential cutoff model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep), yields alpha = -0.03(-0.47,+0.59) and Ep = 283(-52,+68) keV.
All the quoted errors are at the 68% confidence level. All the quoted values are preliminary.
GCN Circular #31910
T. Sakamoto (AGU), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC/UMBC), M. Stamatikos (OSU) (i.e. the Swift-BAT team):
Using the data set from T-240 to T+40 sec sec from the recent telemetry downlink,
we report further analysis of BAT GRB 220412B (trigger #1102329)
(Gropp et al. GCN Circ. 31886). The BAT ground-calculated position is
RA, Dec = 320.758, -0.261 deg which is
RA(J2000) = 21h 23m 01.9s
Dec(J2000) = -00d 15' 38.5"
with an uncertainty of 1.6 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 75%.

The BAT light curve showed a single-peaked
structure. T90 (15-350 keV) is 0.14 +- 0.04 sec
(estimated error including systematics).

The time-averaged spectrum from T-0.03 to T+0.16 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.17 +- 0.20. The fluence in the 15-150 keV band is 8.9 +- 1.2 x 10^-08 erg/cm2.
The 1-sec peak photon flux measured from T-0.44 sec in the 15-150 keV band
is 1.0 +- 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/1102329/BA/
GCN Circular #31917
M. H. Siegel and J. D. Gropp (PSU) report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 220412B 89 s after the BAT trigger (Gropp et al., GCN Circ. 31886). No optical afterglow consistent with the BAT position (Sakamoto et al., GCN Circ. 31910) 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 initial exposures are:
```
Filter         T_start(s)   T_stop(s)      Exp(s)         Mag

white (fc)          89          217          128         >20.0
white             4378         4577          197         >20.3
b                 4173         4373          197         >19.8
u                 3968         4167          197         >19.4
w2                4584         4663           78         >19.2
```
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.060 in the direction of the burst (Schlegel et al. 1998).

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Jochen Greiner, last update: 19-Apr-2022 [Disclaimer]