Gamma-ray Burst 220921A

(All information courtesy of the instrument teams.)

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Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Sep 22 13:19:49 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     685451164
GRB_RA:           66.850d {+04h 27m 24s} (J2000),
                  67.044d {+04h 28m 10s} (current),
                  66.424d {+04h 25m 42s} (1950)
GRB_DEC:         -40.000d {-39d 59' 59"} (J2000),
                 -39.950d {-39d 57' 00"} (current),
                 -40.110d {-40d 06' 36"} (1950)
GRB_ERROR:       1.00 [deg radius, statistical only]
GRB_DATE:        19843 TJD;   264 DOY;   22/09/21
GRB_TIME:        39959.07 SOD {11:05:59.07} UT
GRB_PHI:          88.80 [deg]
GRB_THETA:        69.43 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:       178.66d {+11h 54m 39s}   +0.58d {+00d 34' 44"}
SUN_DIST:        106.79 [deg]   Sun_angle= 7.4 [hr] (West of Sun)
MOON_POSTN:      132.20d {+08h 48m 47s}  +23.10d {+23d 06' 05"}
MOON_DIST:        87.46 [deg]
MOON_ILLUM:      18 [%]
GAL_COORDS:      243.55,-43.94 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       52.36,-60.45 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220921462/quicklook/glg_lc_medres34_bn220921462.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2022/bn220921462/quicklook/glg_locplot_all_bn220921462.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 has human-in-the-loop processing.  
COMMENTS:           
COMMENTS:        NOTE: This GBM event is temporally(2.0<100sec) coincident with the KONUS event (trignum=1984339961).

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Wed 21 Sep 22 18:01:21 UT
NOTICE_TYPE:     Fermi-LAT Offline Position
TRIGGER_NUM:     685451164
GRB_RA:           66.790d {+04h 27m 10s} (J2000),
                  66.983d {+04h 27m 56s} (current),
                  66.366d {+04h 25m 28s} (1950)
GRB_DEC:         -40.250d {-40d 15' 00"} (J2000),
                 -40.200d {-40d 12' 00"} (current),
                 -40.361d {-40d 21' 37"} (1950)
GRB_ERROR:       25.19 [arcmin radius, 90% containment, statistical only]
GRB_DATE:        19843 TJD;   264 DOY;   22/09/21
GRB_TIME:        39959.07 SOD {11:05:59.07} UT
TRIGGER_ID:      0x20000000
MISC:            0x40000000
SUN_POSTN:       178.84d {+11h 55m 22s}   +0.50d {+00d 30' 10"}
SUN_DIST:        106.86 [deg]   Sun_angle= 7.5 [hr] (West of Sun)
MOON_POSTN:      134.65d {+08h 58m 37s}  +22.47d {+22d 28' 29"}
MOON_DIST:        88.77 [deg]
MOON_ILLUM:      17 [%]
GAL_COORDS:      243.89,-43.99 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:       52.11,-60.67 [deg] ecliptic lon,lat of the burst (or transient)
COMMENTS:        Fermi LAT Offline position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        It is the result of human-in-the-loop processing.  
COMMENTS:        This is a human generated position of a LAT ground detection.  
COMMENTS:        This source corresponds to GBM trigger.

GCN Circular #32567
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a series of observations, tiled on the sky, of the Fermi/LAT GRB 220921A. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00107
Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the Fermi/LAT event is high: any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular #32568
R. Pillera (Politecnico and INFN Bari), E. Bissaldi (Politecnico and INFN Bari), N. Di Lalla (Stanford Univ.) report on behalf of the Fermi-LAT team:
At 11:05:59.07 UTC on September, 21, 2022 Fermi-LAT detected high-energy emission from GRB 220921A, which was also detected by Fermi GBM (trigger 685451164 / 220921462).
The best LAT on-ground location is found to be
RA, Dec = 66.79, -40.25 (J2000)
with an error radius of 0.42 deg (90 % containment, statistical error only). This was 69 deg from the LAT boresight at the time of the trigger.
The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The 100 MeV - 1 GeV photon flux in the time interval 0-2000 s after the GBM trigger is (3.1 +/- 0.1)E-06 ph/cm2/s. The estimated photon index above 100 MeV is -2.1 +/- 0.3. The highest-energy photon is a 866 MeV event which is observed 935 seconds after the GBM trigger.
A Swift ToO has been requested for this burst.
The Fermi-LAT point of contact for this burst is Roberta Pillera (roberta.pillera@ba.infn.it).
The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden.
GCN Circular #32569
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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the LAT GRB220921.46 (trigger No 685451164,04h 27m 09.60s , -40d 15m 00.0s, R=0.419833) errorbox 6084 sec after notice time and 31017 sec after trigger time at 2022-09-21 19:42:56 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 83 deg. The sun altitude is -39.3 deg.
The galactic latitude b = -44 deg., longitude l = 244 deg.
Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2097454
We obtain a following upper limits.
```
Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

   31047 | 2022-09-21 19:42:56 |         MASTER-SAAO | (04h 26m 34.71s , -40d 24m 51.8s) |   C |    60 | 15.4 |        
   31140 | 2022-09-21 19:44:28 |         MASTER-SAAO | (04h 26m 31.92s , -40d 22m 54.3s) |   C |    60 | 16.0 |        
```
Filter C is a clear (unfiltred) band.
The observation and reduction will continue. The message may be cited.
GCN Circular #32570
V.Lipunov (Lomonosov MSU), D.A.H.Buckley (SAAO), N.Tiurina, A.Kuznetsov, O.Gress, E.Gorbovskoy, G.Antipov, P.Balanutsa, K.Zhirkov, A.Chasovnikov, D.Vlasenko, V.Senik, D.Kuvshinov, V.Topolev,Ya.Kechin, Yu.Tselik (Lomonosov Moscow State University, SAI, Physics Department), C.Francile, R. Podesta, C.Lopez, F. Podesta (Observatorio Astronomico Felix Aguilar OAFA), R. Rebolo, M. Serra (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory), N.M.Budnev (ISU,API), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational State University)
MASTER OT J042553.42-402420.7 discovery as possibly counterpart of GRB 220921A AT2022vjw
MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic Net", Advances in Astronomy, 2010, 30L ) discovered OT source at (RA, Dec) = 04h 25m 53.42s -40d 24m 20.7s on 2022-09-21.82255 UT during Fermi trigger 685451164 inspection(T0=2022-09-21 11:05:59.07) (Lipunov et al. GCN 32569, Fermi-LAT GCN 32568, also detected by GECAM-B) https://master.sai.msu.ru/site/master2/event.php?id=2097239 .
The OT unfiltered magnitude is 17.8m (automatic), mlim=19.8.
The OT is seen in 24 images. There is no minor planet at this place.
We have 600 reference images without any OT since 2014, for ex., on 2018-11-12.98741 UT with unfiltered mlim=20.3m.
Spectral observations are required.
There is possible host galaxy in VIZIER database (DES, rmag=24.3)
The message may be cited.
GCN Circular #32571
Swift-XRT has performed follow-up observations of the Fermi-LAT-detected burst GRB 220921A, collecting 4.1 ks of Photon Counting (PC) mode data between T0+27.4 and T0+40.7 ks.
An uncatalogued X-ray source has been detected consistent with being within 17.3 arcmin from the center of the Fermi-LAT position (which is within its 90% error radius of 25.19 arcmin; Pillera et al., GCN 32568), and being consistent with the optical transient detected by MASTER (Lipunov et al., GCN 32570). The source's peak flux (8.6 (+/- 1.9) * 10^-12 erg cm^-2 s^-1) is 7.6-σ above the RASS limit, and it is fading with 2.9-σ significance.
Source 1:
```
  RA (J2000.0):  66.47255  =  04:25:53.41
  Dec (J2000.0): -40.4057  =  -40:24:20.4
  Error: 3.8 arcsec (radius, 90% conf.)
  Count-rate: (0.20 [+/- 0.04]) ct s^-1
  Distance: 17.3 arcsec from Fermi-LAT position
  Exposure: 1328 s (vignetting corrected)
```
Two other uncatalogued sources were also detected within the GRB position.
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/xrt_products/TILED_GRB00107/.
Further observations are pending.
This circular is an official product of the Swift-XRT team.
GCN Circular #32572
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO) and D.A.H Buckley (SAAO) report on behalf of the MeerLICHT consortium:
Following the detection of GRB 220921A by Fermi/LAT (Pillera et al., GCN 32568), the 0.6m wide-field MeerLICHT telescope, located at Sutherland, South Africa, obtained a repeated series of 60s exposures of a field encompassing the entire LAT error box in the q,u,g,r,i,z bands following the sequence quqgqrqiqz. Observations started at 01:29:34 UT on September 22 and continued for approximately two hours.
We detect the previously reported afterglow to GRB 220921A at a position consistent with the MASTER and Swift/XRT positions (Lipunov et al., GCN 32570; Kingler et al., GCN 32571) with the following AB magnitudes at a mid-time of September 22 01:46:00 UT, 0.61 days after the LAT trigger time:
```
u = 19.28 +/- 0.14
g = 18.64 +/- 0.03
q = 18.47 +/- 0.02
r = 18.43 +/- 0.04
i = 18.25 +/- 0.05
z = 18.24 +/- 0.11
```
We note that the source is exhibiting fading behaviour with respect to the previously reported MASTER brightness (Lipunov et al., GCN 32570).
MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.
GCN Circular #32574
E. Bissaldi (Politecnico and INFN Bari) reports on behalf of the Fermi GBM Team:
"At 11:05:59.071 UT on 21 September 2022, the Fermi Gamma-Ray Burst Monitor (GBM) triggered and located GRB 220921A (trigger 685451164/ 220921462), which was also detected by Fermi-LAT (Pillera et al. 2022, GCN #32568).
The on-ground calculated location, using the GBM trigger data, is
RA = 66.85, DEC = -40.0
(J2000 degrees, equivalent to 04h 27m, -40d 00'), with a statistical uncertainty of 1 degree (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error. [Connaughton et al. 2015, ApJS, 216, 32]). The Fermi GBM on-ground Localization is consistent with the Fermi-LAT position.
The angle from the Fermi LAT boresight at the GBM trigger time is 69 degrees.
The GBM light curve consists of multiple emission episodes with a duration (T90) of about 210 s (50-300 keV). The time-averaged spectrum from T0 to T0+40 s is best fit by a Band function with Epeak = 142 +/- 4 keV, alpha = -0.90 +/- 0.02, and beta = -2.09 +/- 0.02.
The event fluence (10-1000 keV) in this time interval is (5.92 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+11 s in the 10-1000 keV band is 36.2 +/- 0.4 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 #32575
D. Svinkin, D. Frederiks, M. Ulanov, A. Tsvetkova, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, report:
The bright, long-duration GRB 220921A (Fermi-LAT detection: Pillera et al., GCN Circ. 32568; Fermi-GBM detection: Bissaldi, GCN Circ. 32574) triggered Konus-Wind at T0=39961.714 s UT (11:06:01.714).
The burst light curve shows the bright multipeaked initial emission episode which starts at ~T0-3.7 s and ends at ~T0+38 s, followed by a weaker episode at T0+220 s. The total duration of ~231 s. The emission is seen up to ~8 MeV.
The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB220921_T39961/
As observed by Konus-Wind, the burst had a fluence of 9.71(-2.95,+2.35)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+9.216 s, of 1.44(-0.25,+0.26)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst (measured from T0 to T0+257.536 s) is best fit in the 20 keV - 8 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.88(-0.47,+0.67), the high energy photon index beta = -2.07(-0.50,+0.15), the peak energy Ep = 126(-36,+85) keV (chi2 = 93/78 dof).
The spectrum near the maximum count rate (measured from T0+6.656 to T0+11.776 s) is best fit in the 20 keV - 8 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.89(-0.14,+0.20), the high energy photon index beta = -2.26(-0.19,+0.14), the peak energy Ep = 203(-35,+36) keV (chi2 = 106/78 dof).
All the quoted errors are at the 90% confidence level. All the quoted values are preliminary.
GCN Circular #32576
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), Simone Dichiara (PSU), Diego Gonzalez (UNAM), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Oc�lotl Lopez (UNAM), Margarita Pereyra (UNAM), and Eleonora Troja (GSFC/UMD) report:
We observed the field of the Fermi/LAT GRB 220921A (Pillera et al., GCN Circ. 32568) with the DDOTI wide-field imager at the Observatorio Astron�mico Nacional on Sierra San Pedro Martir (http://ddoti.astroscu.unam.mx) from 2022-09-23 11:51 to 12:24 UTC (48.75 to 49.30 hours after the trigger) obtaining 2040 seconds of exposure.
At the position of the OT detected by MASTER-Net (Lipunov et al., GCN Circ. 32570) we detect a source with w = 19.31 +/- 0.13. We calibrate our photometry against the APASS catalog.
The afterglow has continued to fade from the observations reported by Lipunov et al. (GCN Circ. 32570) and de Wet et al. (GCN Circ. 32572).
We thank the staff of the Observatorio Astron�mico Nacional in San Pedro Martir.
GCN Circular #32577
T. Laskar (University of Utah), K. D. Alexander (University of Arizona), E. Berger (Harvard University), R. Chornock (UC Berkeley), W. Fong (Northwestern University), R. Margutti (UC Berkeley), C. G. Mundell (University of Bath), and P. Schady (University of Bath) report on behalf of a larger collaboration:
"We observed GRB 220921A (Pillera et al., GCN 32568) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 97.5 GHz beginning on 2021 September 23 08:04 UT (45 h after the burst). Preliminary analysis reveals a mm source with flux density of ~ 0.7 mJy at position:
```
RA (J2000) = 04:25:53.42
Dec (J2000) = -40:24:20.25
```
with uncertainty ~ 0.01" in each coordinate, consistent with the X-ray position (N. Klinger, GCN 32571) and optical position (Lipunov et al., GCN 32570). Further observations are planned.
We thank the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations."
GCN Circular #32582
S. de Wet (UCT), P.J. Groot (Radboud/UCT/SAAO) and D.A.H Buckley (SAAO) report on behalf of the MeerLICHT consortium:
The 0.6m wide-field MeerLICHT telescope obtained a total of six 300s exposures in the qugrizq bands in order to monitor the evolving afterglow of GRB 220921A. Observations started at 00:34:09 UT on September 24, approximately 2.56 days post-trigger. We detect the afterglow with a SNR > 5 in the qugri bands and with a SNR of 3.8 in the z band. We report the following magnitudes:
```
u = 20.63 +/- 0.21
g = 20.52 +/- 0.10
q = 20.23 +/- 0.04
r = 20.16 +/- 0.10
i = 20.24 +/- 0.14
z = 19.91 +/- 0.28
```
We note that the source is continuing to fade.
MeerLICHT is built and run by a consortium consisting of Radboud University, University of Cape Town, the South African Astronomical Observatory, the University of Oxford, the University of Manchester and the University of Amsterdam.
GCN Circular #32596
R. Strausbaugh (University of Minnesota), A. Cucchiara (College of Marin) report on behalf of a larger collaboration:
We observed the Fermi-LAT detection GRB 220921A (Pillera et al., GCN 32568) field with the Las Cumbres Observatory Global Telescope Network (LCOGT) 1-meter Sinistro instrument at the South African Astronomical Observatory site, on September 22, from 00:18 to 00:45 (corresponding to 13.22 to 14.57 hours from the GRB trigger time) with the Bessel I and R filters.
We performed a series of 3x300s exposures in R and I bands. We detect the MASTER optical afterglow candidate (Lipunov et al., GCN 32570), in both bands, consistent with other optical detections (de Wet et al., GCN 32572; Watson et al., GCN 32576).
The following magnitudes are calculated using the USNO-B1 catalog as reference:
```
R= 18.02 +/- 0.27
I= 17.78 +/- 0.36
```
We also observed the afterglow of GRB 220921A with the LCOGT 1-meter Sinistro instrument at the Cerro Tololo Interamerican Observatory, Chile site, on September 23, from 04:50 to 05:18 (corresponding to 41.75 to 42.22 hours from the GRB trigger time) with the Bessel I and R filters.
We performed a series of 3x300s exposures in R and I bands. We detect the MASTER optical afterglow candidate (Lipunov et al., GCN 32570) in both bands.
The following magnitudes are calculated using the USNO-B1 catalog as reference:
```
R= 19.26 +/- 0.34
I= 19.03 +/- 0.39
```
These magnitudes are not corrected for galactic extinction. Further observations are planned.
GCN Circular #32618
James Leung (University of Sydney/CSIRO), Ziteng Wang (University of Sydney/CSIRO), Emil Lenc (CSIRO), Tara Murphy (University of Sydney)
The Australia Telescope Compact Array (ATCA) observed GRB 220921A (Pillera et al., GCN 32568) at multiple frequencies starting on 2022 September 28, from 16:30 to 21:00 UTC (7.2 to 7.4d post-trigger).
We detect a radio source in all bands at the position:
```
RA (J2000) = 04:25:53.4
Dec (J2000) = -40:24:20.5
```
with uncertainty ~0.5" in each coordinate, which is consistent with the MASTER optical (Lipunov et al., GCN 32570) and ALMA mm (Laskar et al., GCN 32577) candidate afterglow positions.
We report our preliminary flux density measurements below:
```
Freq (GHz) | Peak Flux Density (micro-Jy/beam)
----------------------------------------------
5.5        | 163 +/- 19
9.0        | 364 +/- 17
16.7       | 763 +/- 50
21.2       | 988 +/- 95
```
Ongoing observations are planned.
We thank CSIRO staff for rapidly scheduling and supporting these observations.

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Jochen Greiner, last update: 03-Oct-2022 [Disclaimer]