Gamma-ray Burst 230421A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Apr 23 09:43:15 UT
NOTICE_TYPE:     Fermi-GBM Flight Position
RECORD_NUM:      48
TRIGGER_NUM:     703762971
GRB_RA:           53.600d {+03h 34m 24s} (J2000),
                  53.914d {+03h 35m 39s} (current),
                  52.928d {+03h 31m 43s} (1950)
GRB_DEC:          +8.167d {+08d 10' 00"} (J2000),
                  +8.243d {+08d 14' 36"} (current),
                  +8.000d {+08d 00' 01"} (1950)
GRB_ERROR:       19.05 [deg radius, statistical plus systematic]
GRB_INTEN:       112 [cnts/sec]
DATA_SIGNIF:     7.10 [sigma]
INTEG_TIME:      2.048 [sec]
GRB_DATE:        20055 TJD;   111 DOY;   23/04/21
GRB_TIME:        34966.37 SOD {09:42:46.37} UT
GRB_PHI:          15.00 [deg]
GRB_THETA:        90.00 [deg]
DATA_TIME_SCALE: 2.0480 [sec]
HARD_RATIO:      0.80
LOC_ALGORITHM:   3 (version number of)
MOST_LIKELY:      76%  GRB
2nd_MOST_LIKELY:  20%  Distant Particles
DETECTORS:       0,1,0, 0,0,1, 0,0,0, 0,0,0, 0,0,
SUN_POSTN:        28.91d {+01h 55m 38s}  +11.84d {+11d 50' 06"}
SUN_DIST:         24.87 [deg]   Sun_angle= -1.7 [hr] (East of Sun)
MOON_POSTN:       43.74d {+02h 54m 58s}  +17.98d {+17d 58' 38"}
MOON_DIST:        13.88 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      176.99,-37.06 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       53.28,-10.75 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif
COMMENTS:        Fermi-GBM Flight-calculated Coordinates.  
COMMENTS:        This trigger occurred at longitude,latitude = 159.20,-24.22 [deg].  
COMMENTS:        The LC_URL file will not be created until ~15 min after the trigger.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Apr 23 09:43:33 UT
NOTICE_TYPE:     Fermi-GBM Ground Position
RECORD_NUM:      58
TRIGGER_NUM:     703762971
GRB_RA:           46.380d {+03h 05m 31s} (J2000),
                  46.694d {+03h 06m 46s} (current),
                  45.708d {+03h 02m 50s} (1950)
GRB_DEC:          +9.110d {+09d 06' 36"} (J2000),
                  +9.199d {+09d 11' 57"} (current),
                  +8.917d {+08d 55' 00"} (1950)
GRB_ERROR:       12.91 [deg radius, statistical only]
DATA_SIGNIF:     9.30 [sigma]
DATA_INTERVAL:   2.048 [sec]
GRB_DATE:        20055 TJD;   111 DOY;   23/04/21
GRB_TIME:        34966.37 SOD {09:42:46.37} UT
GRB_PHI:          11.00 [deg]
GRB_THETA:        96.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   4173 (Gnd S/W Version number)
SUN_POSTN:        28.91d {+01h 55m 38s}  +11.84d {+11d 50' 06"}
SUN_DIST:         17.68 [deg]   Sun_angle= -1.2 [hr] (East of Sun)
MOON_POSTN:       43.74d {+02h 54m 58s}  +17.98d {+17d 58' 42"}
MOON_DIST:         9.23 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      169.50,-41.33 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       46.54, -7.99 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif
POS_MAP_URL:     http://gcn.gsfc.nasa.gov/notices_f/gbm_gnd_loc_map_703762971.fits
COMMENTS:        Fermi-GBM Ground-calculated Coordinates.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file will not be created/available until ~15 min after the trigger.  
COMMENTS:        The POS_MAP_URL file will not be created/available until ~1.5 min after the notice.

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Fri 21 Apr 23 09:53:04 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     703762971
GRB_RA:           44.550d {+02h 58m 12s} (J2000),
                  44.858d {+02h 59m 26s} (current),
                  43.890d {+02h 55m 33s} (1950)
GRB_DEC:          +5.960d {+05d 57' 36"} (J2000),
                  +6.052d {+06d 03' 08"} (current),
                  +5.760d {+05d 45' 38"} (1950)
GRB_ERROR:       5.55 [deg radius, statistical only]
GRB_DATE:        20055 TJD;   111 DOY;   23/04/21
GRB_TIME:        34966.37 SOD {09:42:46.37} UT
GRB_PHI:          13.00 [deg]
GRB_THETA:        99.00 [deg]
E_RANGE:         44.032 - 279.965 [keV]
LOC_ALGORITHM:   41731 (Gnd S/W Version number)
SUN_POSTN:        28.91d {+01h 55m 40s}  +11.84d {+11d 50' 14"}
SUN_DIST:         16.77 [deg]   Sun_angle= -1.1 [hr] (East of Sun)
MOON_POSTN:       43.83d {+02h 55m 19s}  +18.01d {+18d 00' 41"}
MOON_DIST:        12.00 [deg]
MOON_ILLUM:      2 [%]
GAL_COORDS:      170.46,-44.90 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       43.87,-10.50 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_locplot_all_bn230421405.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice was generated completely by automated pipeline processing.  
COMMENTS:        This is likely a Long GRB.

GCN Circular #33668
The Fermi GBM team reports the detection of a likely LONG GRB
At 09:42:46 UT on 21 Apr 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230421A (trigger 703762971.373066 / 230421405).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 44.5, Dec = 6.0 (J2000 degrees, equivalent to J2000 02h 58m, 6d 00'), with a statistical uncertainty of 5.5 degrees.
The angle from the Fermi LAT boresight is 99.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_skymap_all_bn230421405.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_healpix_all_bn230421405.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif
GCN Circular #33669
The Fermi GBM team reports the detection of a likely LONG GRB
At 09:42:46 UT on 21 Apr 2023, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 230421A (trigger 703762971.373066 / 230421405).
The on-ground calculated location, using the Fermi GBM trigger data, is RA = 44.5, Dec = 6.0 (J2000 degrees, equivalent to J2000 02h 58m, 6d 00'), with a statistical uncertainty of 5.5 degrees.
The angle from the Fermi LAT boresight is 99.0 degrees.
The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_skymap_all_bn230421405.png
The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_healpix_all_bn230421405.fit
The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2023/bn230421405/quicklook/glg_lc_medres34_bn230421405.gif
GCN Circular #33672
James DeLaunay (U Alabama), Aaron Tohuvavohu (U Toronto), Gayathri Raman (P= SU), Jamie A. Kennea (PSU), Samuele Ronchini (PSU), Tyler Parsotan (UMBC/GS= FC) report:
Swift/BAT did not localize GRB 230431A onboard (T0: 2023-04-21 09:42:46.370= 000UTC, Fermi/GBM GCN 33668).
The Fermi notice, distributed in near real-time, triggered the Swift Missio= n Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunit= ies (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).=20
Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert = Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] = seconds around the time of the burst. All the requested event mode data was= delivered to the ground.
The burst occured during a Swift slew.=20 Slew mosaic imaging finds the position of the burst with SNR of 10.5.
The BAT position is RA, Dec =3D 41.704, +1.119 deg which is
```
   RA(J2000)  =3D 02h 46m 48.96s
   Dec(J2000) =3D +01d 07=E2=80=B2 08.4=E2=80=B3
```
with an estimated uncertainty of 5 arcmin radius.
The burst location is Sun constrained for Swift, so there will be no XRT or= UVOT followup.
GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/
GCN Circular #33675
E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH) report on behalf of the Fermi GBM Team:
"At 09:42:46.37 UT on 21 April 2023, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 230421A (trigger 703762971 / 230421405), which was also detected by the Swift/BAT-GUANO (DeLaunay et al. 2023, GCN 33672). The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time is 104 degrees.
The GBM light curve consists of a single emission episode with a duration (T90) of about 10 s (50-300 keV). The time-averaged spectrum from T0-1 s to T0+4 s is adequately fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 360 +/- 160 keV.
The event fluence (10-1000 keV) in this time interval is (1.3 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.3 s in the 10-1000 keV band is 3.2 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"

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Jochen Greiner, last update: 20-Mai-2023 [Disclaimer]