GRB 210822A
GCN Circular 30677
Subject
GRB 210822A: Swift detection of a burst with an optical afterglow
Date
2021-08-22T09:52:13Z (4 years ago)
From
Kim Page at U.of Leicester <klp5@leicester.ac.uk>
K. L. Page (U Leicester), J.D. Gropp (PSU), N. P. M. Kuin (UCL-MSSL)
and A. Y. Lien (U Tampa) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 09:18:18 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210822A (trigger=1069788). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 304.476, +5.265 which is
RA(J2000) = 20h 17m 54s
Dec(J2000) = +05d 15' 54"
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 30 sec. The peak count rate
was ~38000 counts/sec (15-350 keV), at ~0 sec after the trigger.
The XRT began observing the field at 09:19:32.7 UT, 74.6 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 304.4377, 5.2786 which is equivalent to:
RA(J2000) = 20h 17m 45.05s
Dec(J2000) = +05d 16' 43.0"
with an uncertainty of 11.9 arcseconds (radius, 90% containment). This
location is 145 arcseconds from the BAT onboard position, within the
BAT error circle. No event data are yet available to determine the
column density using X-ray spectroscopy.
The initial flux in the 0.1 s image was 1.25e-08 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 250 seconds with the U filter
starting 297 seconds after the BAT trigger. An afterglow candidate
has been found in the initial data products with a magnitude
of u = 13.81 +/- 0.03. No correction has been made for the expected
extinction corresponding to E(B-V) of 0.162. The preliminary UVOT
position is RA=304.43748, Dec = 5.28337 (J2000), which is equivalent
to:
RA = 20h 17m 45.0s,
Dec = +05d 17m 00.1s (J2000) with an uncertainty of about an
arcsecond.
Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk).
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 30678
Subject
GRB 210822A: GECAM detection
Date
2021-08-22T11:31:19Z (4 years ago)
From
Shaolin Xiong at IHEP <xiongsl@ihep.ac.cn>
C. W. Wang, S. L. Xiong, X. Y. Zhao, X. Y. Song, C. Cai, C. Y. Li,
Y. Huang, S. L. Xie, J. C. Liu, Y. Q. Zhang,�� Y. Zhao, Z. W. Guo, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li,
X. H. Liang, J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu,
Q. Luo, X. Ma, G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi,
L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, J. Z. Wang,X. L. Zhang,
W. C. Xue, X. Y. Wen, S. Xiao, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao,
Q. B. Yi, B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang,
H. M. Zhang, K. Zhang, P. Wang, P. Zhang, S. N. Zhang, Z. Zhang,
S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP), report on behalf of GECAM team:
During the commissioning phase, GECAM-B was triggered in-flight
by a long bright burst, GRB 210822A, at 2021-08-22T09:18:18.00 UTC
(denoted as T0), which is also observed by Swift/BAT (GCN #30677).
Its alert data was downlinked to the ground through the
short message service of BeiDou Navigation Satellite System (BDS).
According to the GECAM-B light curves in about 30-1000 keV
from BDS alert data, this burst mainly consists of multiple
pulses with a duration of about 15 s.
The GECAM light curve could be found here:
http://twiki.ihep.ac.cn/pub/GECAM/GRBList/gecamb_lc_grd_all_combine_83323099.png
An automatic localization was calculated using the light curves and
spectrum,
and the GECAM location is consistent with the Swift/BAT position within
the error.
Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).
GCN Circular 30679
Subject
GRB 210822A: KAIT Optical Afterglow Confirmation
Date
2021-08-22T15:25:27Z (4 years ago)
From
Weikang Zheng at UC Berkeley <weikang@berkeley.edu>
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 the Swift GRB 210822A (Page et al.,
GCN 30677; see also GECAM detection, Wang et al., GCN 30678)
starting at 09:20:02 UT, 104s after the burst.
Observations were performed with a sequence in the clear (roughly R),
V, and I filters, and the exposure time was 20 s per image.
The bright optical afterglow reported by UVOT (Page et al., GCN 30677)
was clearly detected in our single image. We measure its brightness
of 11.4 mag in our first clear image at 114s after the burst, then
decayed to 16.1 mag at 2690s after the burst.
A preliminary KAIT clear band light curve is available at:
https://w.astro.berkeley.edu/~zwk/grb/GRB210822A/GRB210822A_kait.png
GCN Circular 30680
Subject
GRB 210822A: RATIR Optical Detections
Date
2021-08-22T16:59:44Z (4 years ago)
From
Nat Butler at Az State U <natbutler@asu.edu>
Nat Butler (ASU), Alan M. Watson (UNAM), Alexander Kutyrev (GSFC), William
H. Lee (UNAM), Eleonora Troja (GSFC), Michael G. Richer (UNAM), Ori Fox
(STScI), J. Xavier Prochaska (UCSC), Josh Bloom (UCB), Enrico Ramirez-Ruiz
(UCSC), Jes��s Gonz��lez (UNAM), Carlos Rom��n-Z����iga (UNAM), Harvey Moseley
(GSFC), Rosa L. Becerra (UNAM), Simone Dichiara (UMD), and Oc��lotl L��pez
(UNAM) report:
We observed the field of GRB 210822A (Page, et al., GCN 30677) with the
Reionization and Transients Infrared Camera (RATIR) on the 1.5m Harold
Johnson Telescope at the Observatorio Astron��mico Nacional on Sierra San
Pedro M��rtir from 2021/08 22.39 to 2021/08 22.41 UTC (1.2 minutes to 0.49
hours after the BAT trigger), obtaining a total of 0.19 hours exposure in
the r and i bands.
We detect the fading OT (see, Zheng & Filippenko, GCN 30679) with high
confidence. The flux varies approximately as t^(-1) from i = 13.2 to i =
15.8 (and r=15.6). These preliminary magnitudes are in the AB system and
are not corrected for Galactic extinction in the direction of the GRB.
We thank the staff of the Observatorio Astron��mico Nacional in San Pedro
M��rtir.
GCN Circular 30681
Subject
Swift GRB 210822A: Global MASTER-Net observations report
Date
2021-08-22T17:07:28Z (4 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
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-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 Swift GRB 210822A ( K. L. Page et al., GCN 30677) errorbox 27300 sec after notice time and 27365 sec after trigger time at 2021-08-22 16:54:24 UT, with upper limit up to 16.2 mag. Observations started at twilight. The observations began at zenith distance = 68 deg. The sun altitude is -8.8 deg.
The galactic latitude b = -17 deg., longitude l = 48 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1697012
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
27456 | MASTER-SAAO | C | 180 | 16.2 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 30682
Subject
GRB 210822A: Enhanced Swift-XRT position
Date
2021-08-22T17:08:09Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester)
report on behalf of the Swift-XRT team.
Using 501 s of XRT Photon Counting mode data and 2 UVOT
images for GRB 210822A, 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 = 304.43756, +5.28349 which is equivalent
to:
RA (J2000): 20h 17m 45.01s
Dec (J2000): +05d 17' 00.6"
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 30684
Subject
GRB 210822A: Nanshan/NEXT optical observations
Date
2021-08-22T18:35:26Z (4 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
S.Y. Fu (NAOC), Z.P. Zhu (NAOC,HUST), X. Liu, D. Xu (NAOC), X. Gao
(Urumqi No.1 Senior High School), J.Z. Liu (XAO) report:
We observed the field of GRB 210822A (Page et al., GCN 30677) using the
NEXT-0.6m telescope located at Nanshan, Xinjiang, China. We obtained
15x100 s frames in the Sloan r-band and 10x100 s frames in the V-band,
starting at 14:42:53 UT on 2021-08-22, i.e., 5.41 hr after the BAT trigger.
The optical afterglow (e.g., Page et al., GCN 30677; Zheng & Filippenko,
GCN 30679) of the burst is clearly detected in our stacked images.
Preliminary photometry results are as follows:
Tmid (UT) Tmid-T0(day) Mag MagErr Filter
2021-08-22T14:58:04 0.236 18.53 0.06 r
2021-08-22T15:54:29 0.275 18.88 0.08 V
calibrated with nearby PanSTARRS stars.
GCN Circular 30687
Subject
GRB 210822A: Fermi-LAT detection
Date
2021-08-22T20:02:07Z (4 years ago)
From
Masanori Ohno at Hiroshima U <ohno@astro.hiroshima-u.ac.jp>
M. Ohno (Eotvos U./Hiroshima U.), D. Kocevski (NASA/MSFC), F. Longo
(University and INFN, Trieste), a F. Dirirsa (LAPP, Annecy)
report on behalf of the Fermi-LAT Collaboration:
On August 22th, 2021, Fermi-LAT detected high-energy emission from
GRB 210822A, which was also detected by Swift-BAT (trigger1069788; Page et
al. GCN Circ. 30677) and GECAM (Wang et al., GCN Circ. 30678).
The best LAT on-ground location is found to be
RA, Dec 304.6, 4.9 (degrees, J2000)
with an error radius of 0.5 deg (90% containment, statistical error only).
This was 83 deg from the LAT boresight at the time of the Swift trigger:
T0 = 09:18:18 UT.
And the burst came into the LAT boresight about 500 s after the Swift
trigger time.
The data from the Fermi-LAT show a significant increase
in the event rate after the Swift trigger that is spatially correlated with
the Swift emission with high significance.
The photon flux above 100 MeV in the time interval 500-10000 s after the
Swift trigger is 2.5(-/+ 0.8) ph/cm2/s.
The estimated photon index above 100 MeV is -2.4 (-/+ 0.3).
The highest-energy photon is a 1.0 GeV event which is observed 855 seconds
after the Swift trigger.
The Fermi-LAT point of contact for this burst is
Feraol F. Dirirsa (dirirsa@lapp.in2p3.fr ).
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 30689
Subject
GRB 210822A: Swift-BAT refined analysis
Date
2021-08-23T01:10:30Z (4 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC),
H. A. Krimm (NSF), S. Laha (GSFC/UMBC),
C. B. Markwardt (GSFC), K. L. Page (U Leicester),
D. M. Palmer (LANL), T. Sakamoto (AGU),
M. Stamatikos (OSU), T. N. Ukwatta (LANL)
(i.e. the Swift-BAT team):
Using the data set from T-240 to T+962 sec from the recent telemetry
downlink,
we report further analysis of BAT GRB 210822A (trigger #1069788)
(Page et al., GCN Circ. 30677). The BAT ground-calculated position is
RA, Dec = 304.461, 5.265 deg which is
RA(J2000) = 20h 17m 50.7s
Dec(J2000) = +05d 15' 54.9"
with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 64%.
The mask-weighted light curve shows a multi-peaked structure that
starts and peaks at T0. The main pulse structure ends at ~T+20 s,
followed by a long tail lasting till ~T+400 s. T90 (15-350 keV)
is 180.8 +- 42.7 sec (estimated error including systematics).
The time-averaged spectrum from T-0.37 to T+402.66 sec is best fit
by a simple power-law model. The power law index of the time-averaged
spectrum is 1.30 +- 0.04. The fluence in the 15-150 keV band
is 2.0 +- 0.04 x 10^-5 erg/cm2. The 1-sec peak photon flux measured
from T+0.00 sec in the 15-150 keV band is 27.7 +- 0.7 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/1069788/BA/
GCN Circular 30691
Subject
GRB 210822A: Swift-XRT refined Analysis
Date
2021-08-23T08:08:50Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), A. D'Ai
(INAF-IASFPA), A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N.
Burrows (PSU), A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester)
and K.L. Page report on behalf of the Swift-XRT team:
We have analysed 7.3 ks of XRT data for GRB 210822A (Page et al. GCN
Circ. 30677), from 64 s to 58.6 ks after the BAT trigger. The data
comprise 1.2 ks in Windowed Timing (WT) mode (the first 9 s were taken
while Swift was slewing) with the remainder in Photon Counting (PC)
mode. The enhanced XRT position for this burst was given by Evans et
al. (GCN Circ. 30682).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=0.93 (+0.09, -0.06). At T+145 s the decay
steepens to an alpha of 3.2 (+1.8, -0.8). The light curve breaks again
at T+157 s to a decay with alpha=1.081 (+0.016, -0.015), again at
T+3863 s s to alpha=1.81 (+0.12, -0.11), and again at T+22.4 ks s to
alpha=-0.1 (+0.5, -1.4), before a final break at T+29.6 ks s after
which the decay index is 1.7 (+/-0.3).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.829 (+/-0.019). The
best-fitting absorption column is 1.89 (+/-0.07) x 10^21 cm^-2, in
excess of the Galactic value of 1.5 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.77 (+/-0.12) and a
best-fitting absorption column of 2.3 (+/-0.5) x 10^21 cm^-2. The
counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 4.0 x 10^-11 (5.2 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 2.3 (+/-0.5) x 10^21 cm^-2
Galactic foreground: 1.5 x 10^21 cm^-2
Excess significance: 3.1 sigma
Photon index: 1.77 (+/-0.12)
If the light curve continues to decay with a power-law decay index of
1.7, the count rate at T+24 hours will be 0.050 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.0 x
10^-12 (2.6 x 10^-12) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01069788.
This circular is an official product of the Swift-XRT team.
GCN Circular 30692
Subject
GRB 210822A: NOT photometry and spectroscopy
Date
2021-08-23T08:25:52Z (4 years ago)
From
Dong Xu at NAOC/CAS <dxu@nao.cas.cn>
Z.P. Zhu (NAOC, HUST), L. Izzo (DARK/NBI), S.Y.Fu, D. Xu (NAOC), J.P.U.
Fynbo (DAWN/NBI), E. Paraskeva, S. Vitali (NOT), report on behalf of a
larger collaboration:
We observed the bright optical afterglow of GRB 210822A (Page et al.,
GCN 30677; Wang et al., GCN 30678; Ohno et al., GCN 30687) using the
Nordic Optical Telescope (NOT) equipped with the ALFOSC camera.
We obtained 3x120s frames in the Sloan r-filter, starting at 23:11:50 UT
on 2021-08-22 (i.e., ~ 13.89 hr after the BAT trigger). The previously
reported optical afterglow (e.g., Page et al., GCN 30677; Zheng &
Filippenko, GCN 30679; Butler et al., GCN 30680; Lipunov et al., GCN
30681; Fu et al., GCN 30684) has decayed to m(r) = 19.71 +/- 0.02,
calibrated with the PS1 field.
Subsequently 4x1200 s spectroscopy was carried out. A continuum is
detected over the whole wavelength range of 3700-9500 AA, superimposed
with some absorption features, among which prominent Fe II, Mg II, Mg I,
and Al III lines were identified at a common redshift of z = 1.736. We
conclude that this is the redshift of the burst.
GCN Circular 30693
Subject
GRB 210822A: AstroSat CZTI detection
Date
2021-08-23T09:13:47Z (4 years ago)
From
Gaurav Waratkar at IIT,Bombay <gauravwaratkar@iitb.ac.in>
V. Prasad (IUCAA), P. Sawant (IUCAA), G. Waratkar (IITB), A. Vibhute
(IUCAA), V. Bhalerao (IITB), D. Bhattacharya (IUCAA), A. R. Rao
(IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat
CZTI collaboration:
Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al,
2020, arxiv:2011.07067) showed detection of a bright long GRB 210822A,
which was also detected by Swift (Page et al., GCN 30677), GECAM (Wang
et al., GCN 30678), and Fermi-LAT (Ohno et al., GCN 30687).
The source was clearly detected in the 20-200 keV energy range. The
light curve showed multiple peaks of emission with the strongest peak at
2021-08-22 09:18:17.50 UT. The measured peak count rate associated with
the burst is 2190 (+85, -91) cts/s above the background in the combined
data of four quadrants, with a total of 12961 (+301, -314) cts. The
local mean background count rate was 530 (+2, -3) cts/s. Using
cumulative rates, we measure a T90 of 10 (+0.2, -0.2) s.
It was also clearly detected in the CsI anticoincidence (Veto) detector
in the 100-500 keV energy range. The light curve showed multiple peaks
of emission with the strongest peak at 2021-08-22 09:18:18.97 UT. The
measured peak count rate is 3587 (+117, -127) cts/s above the background
in the combined Veto data of four quadrants, with a total of 24196
(+541, -655) cts. The local mean background count rate was 1799 (+4, -4)
cts/s. We measure a T90 of 12 (+0.5, -0.5) s from the cumulative Veto
light curve.
CZTI GRB detections are reported regularly on the payload site at
http://astrosat.iucaa.in/czti/?q=grb [1]. CZTI is built by a TIFR-led
consortium of institutes across India, including VSSC, ISAC, IUCAA, SAC
and PRL. The Indian Space Research Organisation funded, managed and
facilitated the project.
Links:
------
[1] http://astrosat.iucaa.in/czti/?q=grb
GCN Circular 30694
Subject
Konus-Wind detection of GRB 210822A
Date
2021-08-23T12:38:10Z (4 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, A.Lysenko, A. Ridnaia,
D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long GRB 210822A (Swift detection: Page et al., GCN 30677;
GECAM detection: Wang et al., GCN 30678;
Fermi-LAT detection: Ohno et al., GCN 30687;
AstroSat CZTI detection: Ohno et al., GCN 30693)
triggered Konus-Wind (KW) at T0=33502.974 s UT (09:18:22.974).
The burst light curve shows a bright, multi-peaked pulse
which starts at ~T0-1 s and has a total duration of ~12 s,
followed by a weaker decaying emission visible up to ~T0+50 s.
The emission in the main pulse is seen up to ~15 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210822_T33502/
As observed by Konus-Wind, the burst had
a fluence of (1.20 �� 0.11)x10^-4 erg/cm^2 and
a 64-ms peak energy flux, measured from T0 + 0.320 s,
of (3.25 �� 0.28)x10^-5 erg/cm^2/s (both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+18.176 s)
is best fit in the 20 keV - 20 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.64 (-0.06,+0.07),
the high energy photon index beta = -2.39 (-0.15,+0.12),
the peak energy Ep = 398 (-29,+30) keV,
chi2 = 124/96 dof.
The spectrum near the peak count rate (measured from T0+4.096
to T0+7.936 s) is best fit in the 20 keV - 15 MeV range
by the GRB (Band) function with the following model parameters:
the low-energy photon index alpha = -0.59 (-0.15,+0.18),
the high energy photon index beta = -2.08 (-0.18,+0.12),
the peak energy Ep = 429 (-83,+108) keV,
chi2 = 75/63 dof.
Assuming the redshift z=1.736 (Zhu et al., GCN 30692)
and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315,
and Omega_Lambda = 0.685 (Planck Collaboration, 2014),
we estimate the isotropic energy release E_iso to (9.5 �� 0.8)x10^53 erg,
the isotropic luminosity L_iso to (7.0 �� 0.6)x10^53 erg/s,
the rest-frame peak energy of the time-integrated spectrum Epi,z to (1090 �� 80) keV,
and the rest-frame peak energy of the 'peak' spectrum Epp,z to (1175 �� 250) keV.
With these values, GRB 210822A lies within 68% prediction bands
for both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs
with known redshifts (Tsvetkova et al., 2021, ApJ, 908, 83),
see http://www.ioffe.ru/LEA/GRBs/GRB210702_T68826/GRB210822A_rest_frame.pdf
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 30696
Subject
GRB 210822A: GECAM refined analysis
Date
2021-08-23T15:00:34Z (4 years ago)
From
Chenwei Wang at IHEP <cwwang@ihep.ac.cn>
C. W. Wang, S. L. Xiong, X. Y. Zhao, X. Y. Song, C. Cai, C. Y. Li,
Y. Huang, S. L. Xie, J. C. Liu, Y. Q. Zhang, Y. Zhao, Z. W. Guo, C. Zheng,
Z. H. An, C. Chen, G. Chen, W. Chen, M. Gao, K. Gong, D. Y. Guo, J. J. He,
B. Li, C. Li, J. H. Li, Q. X. Li, X. B. Li, X. Q. Li, Y. G. Li,
X. H. Liang, J. Y. Liao, J. C. Liu, X. J. Liu, Y. Q. Liu, F. J. Lu,
Q. Luo, X. Ma, G. Ou, W. X. Peng, R. Qiao, D. L. Shi, J. Y. Shi,
L. M. Song, G. X. Sun, X. L. Sun, Y. L. Tuo, J. Z. Wang,X. L. Zhang,
W. C. Xue, X. Y. Wen, S. Xiao, Y. B. Xu, Y. P. Xu, S. Yang, M. Yao,
Q. B. Yi, B. X. Zhang, C. Y. Zhang, D. L. Zhang, Fan Zhang, Fei Zhang,
H. M. Zhang, K. Zhang, P. Wang, P. Zhang, S. N. Zhang, Z. Zhang,
S. Y. Zhao, S. J. Zheng, X. Zhou (IHEP), report on behalf of GECAM team:
At 2021-08-22T09:18:18.00 UTC(denoted as T0), GECAM-B was triggered in-flight
by a long bright burst, GRB 210822A, which is also observed by Swift/BAT (GCN #30677).
The spectrum was calculated using the GECAM-B trigger data.
The time-integrated spectrum (measured from T0 to T0+15)
is best fit in the 20 keV - 5 MeV range
by a power law with high energy exponential rolloff model:
dN/dE ~ (E^alpha)*exp(-E/beta)
with alpha = -0.8595 +/- 0.029,
and beta = 394.9867 +/- 23.466 keV.
The event fluence (10-1000 keV) in this time interval is
(7.54 +0.10/-0.19)E-05 erg/cm^2.
Please note that all GECAM results here are preliminary. The final analysis
will be published in journal papers or GECAM online catalog.
Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor
(GECAM) mission consists of two small satellites (GECAM-A and GECAM-B) in
Low Earth Orbit (600 km, 29 deg), launched on Dec 10, 2020 (Beijing Time),
which was funded by the Chinese Academy of Sciences (CAS).
GCN Circular 30697
Subject
GRB 210822A: Detection by GRBAlpha
Date
2021-08-23T15:42:18Z (4 years ago)
From
Masanori Ohno at Hiroshima U <ohno@astro.hiroshima-u.ac.jp>
M. Ohno (Eotvos U./Konkoly Observatory/Hiroshima U.), J. Ripa (Masaryk U.),
H. Takahashi (Hiroshima U.), A. Pal, L. Meszaros, B. Csak (Konkoly
Observatory), N. Werner, M. Topinka, F. Munz, F. Hroch (Masaryk U.), T.
Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus,
M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M.
Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner
Research Center/Eotvos U.), Yuusuke Uchida, Helen Poon, H. Matake, N.
Uchida (Hiroshima U.), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T.
Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa,
K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.),
K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno
(Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J.
Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.) -- the GRBAlpha
collaboration.
The long duration GRB 210822A (Swift-BAT detection; Page et al. GCN Circ.
30677, GECAM detection; Wang et al. GCN Circ. 30678, Fermi-LAT detection;
Ohno et al. GCN Circ. 30687) was detected by the GRBAlpha 1U CubeSat (Pal
et al. Proc. SPIE 2020).
The light curve shows a strong spike structure with a high significance of
a SNR ~ 45. The observed total duration was about 12 sec. GRBAlpha was
leaving the outer Van Allen radiation belt and thus GRB 210822A is
superimposed on a high background due to trapped electrons.
The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB210822A_GCN.pdf
GRBAlpha is a demonstration mission for a future CubeSats constellation
(Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75
x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy
range from ~50 keV to ~1000 keV. GRBAlpha was launched on 2021 March 22
from Baikonur. After its commissioning phase, the scientific observations
are now under way. To increase the duty cycle and the downlink rate, the
upgrade of the on-board data acquisition software stack is in progress. The
ground segment is also supported by the radio amateur community and it
takes advantage of the SatNOGS network for increased data downlink volume.
GCN Circular 30701
Subject
GRB 210822A: Abbey Ridge Observatory optical afterglow observation
Date
2021-08-24T06:49:06Z (4 years ago)
From
Filipp Dmitrievich Romanov at Amateur astronomer <filipp.romanov.27.04.1997@gmail.com>
Filipp D. Romanov (Russia) and David J. Lane (Saint Mary's University,
Canada) report:
Filipp Romanov observed optical afterglow of GRB 210822A (Page et al.,
GCN Circ. 30677) remotely using 0.355-m f/6.2 Schmidt-Cassegrain
telescope of Abbey Ridge Observatory (it is owned by Dave Lane) in
Canada, on 2021-08-23.
Four images (with exposures: 720, 720, 600 and 720 seconds) were
obtained with Cousins R filter from 00:54:39 to 02:17:30 UTC. Faint
(SNR = 5) optical afterglow (with UVOT position) is visible in the
stacked image (mid time = 01:36:04 UTC, that is 16.296 hours after
the trigger). Romanov measured its magnitude comparing to transformed
(using formula Rc=r���-0.22 from Dymock & Miles, 2009) r' magnitudes of
nearby stars from Pan-STARRS DR1 catalogue (Chambers et al., 2016).
The measured magnitude = 20.1 +/- 0.3. Magnitude was not corrected for
Galactic extinction.
Stacked image available here:
http://abbeyridgeobservatory.ca/images/grb210822a.jpg
GCN Circular 30703
Subject
GRB 210822A: GROND observations
Date
2021-08-24T15:19:39Z (4 years ago)
From
Ana Nicuesa at TLS Tautenburg <ana@tls-tautenburg.de>
A. Nicuesa Guelbenzu, S. Klose (both TLS Tautenburg) and
A. Rau (MPE Garching) report:
We observed the field of GRB 210822A (Swift trigger #1069788; Page et al.,
GCN 30677) with GROND mounted at the 2.2m MPG telescope at La Silla
Observatory (Chile).
Observations started at 02:54 UT on August 23, about 17.6 hr after the GRB
trigger. They were performed at an average seeing of 2.2 arcsec and at an
average airmass of 1.2.
Based on combined images with 10 min total exposure, at a mid-time of
03:02 UT on 2021-08-23 for the afterglow (Page et al., GCN 30677; Zheng &
Filippenko, GCN 30679; Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu
et al., GCN 30692; Romanov & Lane, GCN 30701) we derive the following
AB magnitudes:
g' = 20.37 +/- 0.09,
r' = 20.10 +/- 0.05,
i' = 19.92 +/- 0.05.
Given magnitudes are calibrated against Pan-STARRS and are not corrected
for the expected Galactic foreground extinction corresponding to a
reddening of E(B-V) = 0.14 mag in the direction of the burst (Schlegel et
al. 1998).
We thank Angela Hempel for excellent support and for performing the
observations.
GCN Circular 30710
Subject
GRB 210822A: Swift/UVOT Detection
Date
2021-08-25T06:21:36Z (4 years ago)
From
Mike Siegel at PSU/Swift MOC <mhs18@psu.edu>
M. H. Siegel (PSU) and K. L. Page (U. Leicester)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210822A
85 s after the BAT trigger (Page et al., GCN Circ. 30677).
A fading source consistent with the XRT position (Page et al.
GCN Circ. 30677) and the previously reported UVOT source is
is detected in the initial UVOT exposures.
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 (fc) 86 236 147 13.63+/-1.10
white 577 1200 205 15.35+/-0.02
white 4965 5058 91 17.43+/-0.05
white 34405 35230 804 19.15+/-0.05
white 149533 190336 1894 20.64+/-0.11
v 627 1250 77 15.07+/-0.05
v 27494 28215 702 18.68+/-0.13
b 553 1176 58 15.31+/-0.04
b 4760 4960 196 17.56+/-0.06
b 33493 34400 885 19.18+/-0.08
u (fc) 298 548 245 13.78+/-0.03
u 700 1304 39 14.86+/-0.05
u 4555 4755 196 16.85+/-0.05
u 57947 58635 670 19.73+/-0.19
uvw1 676 1299 77 15.28+/-0.07
uvw1 39434 96567 1775 19.90+/-0.22
uvm2 824 1274 38 >17.66
uvm2 92215 93015 788 >20.06
uvw2 602 1225 77 17.21+/-0.18
uvw2 21659 64335 1469 20.40+/-0.34
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.162 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 30712
Subject
GRB 210822A: TSHAO optical observation
Date
2021-08-25T09:49:39Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP), Pozanenko (IKI), N.
Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:
We observed GRB 210822A (Page et al., GCN 30677; Wang et al., GCN
30678; Prasad et al., GCN 30693; Frederiks et al., GCN 30694) with
Zeiss-1000 telescope of Tien Shan Astronomical Observatory on Aug. 22
(UT) 15:48:55 -- 18:48:47. We obtained series with 20 and 30 sec
exposition in R-filter.
The optical afterglow (Page et al., GCN 30677; Zheng et al., GCN 30679;
Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu et al., GCN 30692;
Romanov et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al.,
GCN 30710) at redshift z = 1.736 (Zhu et al., GCN 30692) is detected in
stacked images. Preliminary photometry of the afterglow in a stacked
image of the second series is following.
Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma)
(mid, days) (s)
2021-08-22 17:26:41 0.36184 R 196*20 18.63 0.03 21.0
The photometry is based on nearby USNO-B1.0 stars.
USNO-B1.0
RA Dec R2
20:18:06.64416 +05:17:24.1404 12.33
20:17:59.55288 +05:18:19.5912 13.05
GCN Circular 30713
Subject
GRB 210822A: VLA detection
Date
2021-08-25T14:47:06Z (4 years ago)
From
Tanmoy Laskar at U of Bath <tanmoylaskar@gmail.com>
T. Laskar (University of Bath), K. D. Alexander (Northwestern), E. Berger
(Harvard), R. Chornock (UC Berkeley), W. Fong (Northwestern), R. Margutti
(UC Berkeley), C. G. Mundell (University of Bath), P. Schady (University of
Bath), and G. Schroeder (Northwestern) report on behalf of a larger
collaboration:
"We observed GRB 210822A (Page et al. GCN 30677) with the Karl G. Jansky
Very Large Array (VLA) beginning on 2021 August 24 at 05:30 UT (1.9 d after
the burst). At a mean frequency of 14.8 GHz, we detect a radio source with
a preliminary flux density of ~ 0.4 mJy at the position:
RA (J2000) = 20:17:44.992 +/- 0.001
Dec (J2000) = 05:16:59.53 +/- 0.02
consistent with the position of the optical afterglow (Page et al., GCN
30677) and the Swift/XRT afterglow (Evans al., GCN 30682). Follow-up
observations are planned.
We thank the VLA staff for rapidly executing these observations."
GCN Circular 30714
Subject
GRB 210822A: TSHAO continued optical observation
Date
2021-08-25T16:34:52Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Kusakin (FAP), I. Reva (FAP), Pozanenko (IKI), N.
Pankov (HSE), V. Kim (FAP) report on behalf of GRB-IKI-FuN:
We continue observations of GRB 210822A (Page et al., GCN 30677; Wang
et al., GCN 30678; Prasad et al., GCN 30693; Frederiks et al., GCN
30694) with Zeiss-1000 telescope of Tien Shan Astronomical Observatory.
on Aug. 22 (UT) 15:48:55 -- 18:48:47. We obtained series in R-filter
starting on 2021-08-24 (UT) 16:47:35.
The optical afterglow (Page et al., GCN 30677; Zheng et al., GCN 30679;
Butler et al., GCN 30680; Fu et al., GCN 30684; Zhu et al., GCN 30692;
Romanov et al., GCN 30701; Guelbenzu et al., GCN 30703; Siegel et al.,
GCN 30710; Belkin et al., GCN 30712) at the redshift of z = 1.736 (Zhu
et al., GCN 30692) is detected in stacked image. Preliminary
photometry of the afterglow in a stacked image is following.
Date UT start t-T0 Filter Exp. OT Err. UL(3 sigma)
(mid, days) (s)
2021-08-24 16:47:35 2.33041 R 3180 21.60 0.26 22.0
The photometry is based on nearby USNO-B1.0 stars.
USNO-B1.0
RA Dec R2
20:18:06.64416 +05:17:24.1404 12.33
20:17:59.55288 +05:18:19.5912 13.05
GCN Circular 30723
Subject
GRB 210822A: CAHA 2.2m observations
Date
2021-08-27T00:27:10Z (4 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC,
DARK/NBI), C. Thoene, M. Blazek, J. F. Agui Fernandez (all
HETH/IAA-CSIC), A. Fernandez, I. Hermelo, and P. Martin (all CAHA)
report:
We observed the bright GRB 210822A (Swift detection: Page et al., GCN
#30677; GECAM detection: Wang et al., GCN #30678; Fermi-LAT detection:
Ohno et al., GCN #30687; AstroSat CZTI detection: Prasad et al., GCN
#30693; Konus-Wind detection: Frederiks et al., GCN #30694; GRBAlpha
detection: Ohno et al., GCN #30697) at a redshift of z = 1.736 (Zhu et
al., GCN #30692) with CAFOS mounted on the 2.2m CAHA telescope at Calar
Alto, Alemria, Spain. The first epoch was obtained under very inclement
conditions (almost overcast), and one 60 s as well as four 90 s images
were useful. The second epoch, two nights later, was obtained under
significantly improved (but still not really good) conditions, and 31 x
30 s images were obtained.
The optical afterglow (Page et al., GCN #30677; Zheng et al., GCN
#30679; Butler et al., GCN #30680; Fu et al., GCN #30684; Zhu et al.,
GCN #30692; Romanov & Lane, GCN #30701; Nicuesa Guelbenzu et al., GCN
#30703; Siegel et al., GCN #30710; Belkin et al., GCN #30712; Belkin
et al., GCN #30714) is faintly detected in the first epoch, but not
detected in the second epoch.
Against three nearby Pan-STARRS comparison stars, we measure (AB
magnitudes):
i' = 18.56 +/- 0.14 mag at 0.43283 days after the GRB, and
i' > 21.5 mag at 2.5206 mag after the GRB.
GCN Circular 30744
Subject
GRB 210822A: CALET Gamma-Ray Burst Monitor detection
Date
2021-08-30T07:06:23Z (4 years ago)
From
Valentin Pal'shin at AGU <val@phys.aoyama.ac.jp>
K. Kobayashi (Waseda U),
A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita (AGU),
Y. Kawakubo (LSU), K. Yamaoka (Nagoya U), S. Nakahira (RIKEN),
Y. Asaoka (ICRR), S. Torii, Y. Akaike (Waseda U),
Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC/UMBC),
M. L. Cherry (LSU), S. Ricciarini (U of Florence),
P. S. Marrocchesi (U of Siena),
and the CALET collaboration:
The long GRB 210822A (Swift detection: Page et al., GCN Circ. 30677, Lien
et al., GCN Circ. 30689; GECAM detection: Wang et al., GCN Circ. 30678,
30696; Fermi-LAT detection: Ohno et al., GCN Circ. 30687; AstroSat CZTI
detection: Prasad et al., GCN Circ. 30693; Konus-Wind detection:
Frederiks et al., GCN Circ. 30694; GRBAlpha detection: Ohno et al.,
GCN Circ. 30697; https://gcn.gsfc.nasa.gov/other/210822A.gcn3)
triggered the CALET Gamma-ray Burst Monitor (CGBM) at 09:18:18.162 UTC
on 22 August 2021. The burst signal was seen by all CGBM detectors.
Because of a problem in one of the ground alert processing script,
the GCN notice was not distributed automatically for this event.
The burst light curve shows a multi-peaked structure which starts at
T-0.2 sec, peaks at T+0.1 sec and ends at T+11.0 sec.
The T90 and T50 durations measured by the SGM data are 10.1 +- 0.5 sec
and 5.8 +- 0.4 sec (40-1000 keV), respectively.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1313658800/
The CALET data used in this analysis are provided by
the Waseda CALET Operation Center located at the Waseda University.