GRB 210807A
GCN Circular 30600
Subject
GRB 210807A: Swift detection of a burst with an optical counterpart
Date
2021-08-07T10:34:25Z (4 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
A. Y. Lien (GSFC/UMBC), C. Gronwall (PSU), J.D. Gropp (PSU),
N. J. Klingler (GSFC/UMBC/CRESSTII), K. L. Page (U Leicester) and
D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 10:03:40 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 210807A (trigger=1064221). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 76.677, +58.245 which is
RA(J2000) = 05h 06m 43s
Dec(J2000) = +58d 14' 43"
with an uncertainty of 3 arcmin (radius, 90% containment, including
systematic uncertainty). Because this is an image trigger,
the actual light curve structure requires further ground
data analysis. The 112-s image trigger indicates that
this is a long burst.
The XRT began observing the field at 10:07:02.3 UT, 201.9 seconds after
the BAT trigger. XRT found a bright, uncatalogued X-ray source located
at RA, Dec 76.6815, 58.2503 which is equivalent to:
RA(J2000) = 05h 06m 43.56s
Dec(J2000) = +58d 15' 01.1"
with an uncertainty of 11.1 arcseconds (radius, 90% containment). This
location is 20 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 2.5 s image was 4.08e-09 erg cm^-2 s^-1 (0.2-10
keV).
UVOT took a finding chart exposure of 150 seconds with the White filter
starting 210 seconds after the BAT trigger. There is a candidate afterglow in
the rapidly available 2.7'x2.7' sub-image at
RA(J2000) = 05:06:43.90 = 76.68293
DEC(J2000) = +58:14:59.2 = 58.24978
with a 90%-confidence error radius of about 0.61 arc sec. This position is 3.3
arc sec. from the center of the XRT error circle. The estimated magnitude is
17.00 with a 1-sigma error of about 0.14. No correction has been made for the
expected extinction corresponding to E(B-V) of 0.409.
Burst Advocate for this burst is A. Y. Lien (amy.y.lien AT nasa.gov).
Please contact the BA by email if you require additional information
regarding Swift followup of this burst. In extremely urgent cases, after
trying the Burst Advocate, you can contact the Swift PI by phone (see
Swift TOO web site for information: http://www.swift.psu.edu/)
GCN Circular 30602
Subject
GRB 210807A: BOOTES-5/JGT optical afterglow detection
Date
2021-08-07T14:09:06Z (4 years ago)
From
Youdong HU at IAA-CSIC <huyoudong072@hotmail.com>
Y.-D. Hu, T.-R. Sun, E. Fernandez-Garcia and A. J. Castro-Tirado, M.D. Caballero-Garcia (IAA-CSIC), D. Hiriart and W. H. Lee (UNAM), C. J. Perez del Pulgar and I. Carrasco (UMA), I. H. Park (SKKU) on behalf of a larger collaboration, report:
The 60cm BOOTES-5/JGT robotic telescope at Observatorio Astronomico Nacional in San Pedro Martir (Mexico) automatically responded in 16 min to the Swift trigger of GRB 210807A (Lien et al., GCNC 30600). The first image (1s exposure, clear-filter) was obtained at 10:20:19.5 UT. We detected the optical afterglow at the position reported by Swift /UVOT (Lien et al. GCNC 30600). In the co-added image (10 x 1s exposures) we measure 17.8+/- 0.2 mag. Further analysis is ongoing. The magnitude is calibrated against the USNO-B1 catalog and is not corrected for Galactic extinction in the direction towards the GRB.
We thank the staff at Observatorio Astronomico Nacional in San Pedro Martir for its excellent support.
GCN Circular 30603
Subject
GRB 210807A: Enhanced Swift-XRT position
Date
2021-08-07T16:09:23Z (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 1337 s of XRT Photon Counting mode data and 4 UVOT
images for GRB 210807A, 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 = 76.68376, +58.24980 which is equivalent
to:
RA (J2000): 05h 06m 44.10s
Dec (J2000): +58d 14' 59.3"
with an uncertainty of 2.1 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 30607
Subject
Swift GRB 210807A: Global MASTER-Net observations report
Date
2021-08-07T20:08:23Z (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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 210807A ( A. Y. Lien et al., GCN 30600) errorbox 32639 sec after notice time and 33871 sec after trigger time at 2021-08-07 19:28:12 UT, with upper limit up to 16.6 mag. The observations began at zenith distance = 76 deg. The sun altitude is -21.7 deg.
The galactic latitude b = 11 deg., longitude l = 152 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=1683291
We obtain a following upper limits.
Tmid-T0 | Site |Filt.| Expt. | Limit| Comment
_________|_____________________|_____|_______|______|________
33962 | MASTER-Tavrida | C | 180 | 13.4 |
35859 | MASTER-Tavrida | C | 180 | 16.6 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
GCN Circular 30616
Subject
GRB 210807A: correction to the GCN Circ. #30614 Assy optical observations
Date
2021-08-08T10:25:45Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
V. Kim (FAI, Pulkovo Observatory), A. Pozanenko (IKI), M. Krugov (FAI),
N. Pankov (HSE, IKI), S. Belkin (IKI) report on behalf of GRB IKI FuN:
The name of GRB was indicated incorrectly in GCN Circ. #30614.
The observation and photometry in GCN Circ. #30614 indeed refer to the
GRB 210807A.
We apologize for possible inconvenience.
GCN Circular 30617
Subject
GRB 210807A: Swift-XRT refined Analysis
Date
2021-08-08T12:24:18Z (4 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
A.P. Beardmore (U. Leicester), P.A. Evans (U. Leicester), J.P. Osborne
(U. Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) ,
M. Capalbi (INAF-IASFPA), D.N. Burrows (PSU), J. D. Gropp (PSU), J.A.
Kennea (PSU) and A.Y. Lien report on behalf of the Swift-XRT team:
We have analysed 3.1 ks of XRT data for GRB 210807A (Lien et al. GCN
Circ. 30600), from 208 s to 86.2 ks after the BAT trigger. The data
comprise 488 s in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The enhanced XRT position for this burst was
given by Evans et al. (GCN Circ. 30603).
The light curve can be modelled with a series of power-law decays. The
initial decay index is alpha=0.71 (+/-0.09). At T+384 s the decay
steepens to an alpha of 2.8 (+0.7, -0.6). The light curve breaks again
at T+497 s to a decay with alpha=1.02 (+/-0.03), before a final break
at T+32.3 ks s after which the decay index is 2.1 (+1.0, -0.7).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.82 (+/-0.03). The
best-fitting absorption column is 5.52 (+0.24, -0.23) x 10^21 cm^-2,
in excess of the Galactic value of 3.4 x 10^21 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.71 (+0.15, -0.12)
and a best-fitting absorption column consistent with the Galactic
value. The counts to observed (unabsorbed) 0.3-10 keV flux conversion
factor deduced from this spectrum is 4.6 x 10^-11 (5.9 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.4 (+0.6, -0.0) x 10^21 cm^-2
Galactic foreground: 3.4 x 10^21 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.71 (+0.15, -0.12)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/01064221.
This circular is an official product of the Swift-XRT team.
GCN Circular 30618
Subject
GRB 210807A: Swift/UVOT Detection
Date
2021-08-08T21:07:25Z (4 years ago)
From
Sam LaPorte at PSU <sjl5346@psu.edu>
GRB 210807A: Swift/UVOT Detection
S. J. LaPorte (PSU) and A. Y. Lien (GSFC/UMBC)
report on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 210807A
210 s after the BAT trigger (Lien et al., GCN Circ. 30600).
A source consistent with the XRT position
(Lien et al. GCN Circ. 30600)
is detected in the initial UVOT exposures.
The preliminary UVOT position is:
RA (J2000) = 05:06:43.89 = 76.68289 (deg.)
Dec (J2000) = +58:14:59.2 = 58.24979 (deg.)
with an estimated uncertainty of 0.43 arc sec. (radius, 90% confidence).
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
b 489 683 38 >17.84
u 639 659 19 >17.04
v 390 583 39
16.58+-0.25
uvw1 440 633 38 >17.12
uvw2 539 721 26 >17.08
white 234 383 147
16.93+-0.04
white 234 708 184 17.19+-0.05
The magnitudes in the table are not corrected for the Galactic extinction
due to the reddening of E(B-V) = 0.409 in the direction of the burst
(Schlegel et al. 1998).
GCN Circular 30623
Subject
GRB 210807A: Swift-BAT refined analysis
Date
2021-08-10T01:41:52Z (4 years ago)
From
Sibasish Laha at GSFC <sibasish.laha@nasa.gov>
T. N. Ukwatta (LANL), S. D. Barthelmy (GSFC),
J. R. Cummings (CPI), H. A. Krimm (NSF),
S. Laha (GSFC/UMBC), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. Stamatikos (OSU),
(i.e. the Swift-BAT team):
Using the data set from T-239 to T+963 sec from the recent telemetry downlink,
we report further analysis of BAT GRB 210807A (trigger #1064221)
(Lien et al., GCN Circ. 30600). The BAT ground-calculated position is
RA, Dec = 76.666, 58.257 deg which is
RA(J2000) = 05h 06m 39.7s
Dec(J2000) = +58d 15' 25.6"
with an uncertainty of 1.5 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 28%.
The BAT light curve showed a complex structure with a duration of about ~200 sec.
T90 (15-350 keV) is 156.30 +- 214.60 sec (estimated error including systematics).
The time-averaged spectrum from -19.544 to 640.052 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.26 +- 0.08. The fluence in the 15-150 keV band is 9.5 +- 0.4 x 10^-06 erg/cm2.
The 1-sec peak photon flux measured from T+70.52 sec in the 15-150 keV band
is 1.8 +- 0.4 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/1064221/BA/
GCN Circular 30624
Subject
GRB 210807A: Detection by GRBAlpha
Date
2021-08-10T14:37:22Z (4 years ago)
From
Masanori Ohno at Hiroshima University <ohno@astro.hiroshima-u.ac.jp>
J. Ripa (Masaryk U.), M. Ohno (Eotvos U./Hiroshima 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. Enoto
(Kyoto U.), Zs. Frei (Eotvos U.),
Y. Fukazawa, K. Hirose (Hiroshima U.); S. Hisadomi (Nagoya U.), Y. Ichinohe
(Rikkyo U.),
L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa
(Nagoya U.),
H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.) -- the GRBAlpha
collaboration.
The long duration GRB 210807A (Swift-BAT detection; Lien et al. GCN Circ.
30600)
was detected by the GRBAlpha 1U CubeSat (Pal et al. Proc. SPIE 2020).
This is the first time that a GRB was observed by a 1U CubeSat dedicated to
gamma-ray burst observations.
The data acquisition started at 10:05:14 UT and the tail part of the prompt
emission, which consists of multiple peaks,
was observed with a duration of about 80 sec. The 7.3 sigma detection
significance was confirmed at around 10:06:00 UT.
The light curve obtained by GRBAlpha is available here:
https://grbalpha.konkoly.hu/static/share/GRB210807A.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 30628
Subject
GRB 210807A: Tautenburg observations
Date
2021-08-11T11:37:11Z (4 years ago)
From
Ana Nicuesa at TLS Tautenburg <ana@tls-tautenburg.de>
S. Schmidl, A. Nicuesa Guelbenzu, S. Klose, S. Melnikov, B. Stecklum, U.
Laux (all Tautenburg) and J. Greiner (MPE Garching) report:
We observed the field of GRB 210807A (Lien et al., GCN 30600) with the
Tautenburg 1.34m Schmidt telescope equipped with the TAUKAM 6kx6k CCD
camera.
Observations started at 23:19 UT on August 7, about 13 hours after the GRB
trigger. For the optical afterglow (Lien et al., GCN 30600; Hu et al., GCN
30602; LaPorte et al. GCN 30618) we measure the following magnitudes:
r = 21.66 +/- 0.18, at a midtime of August 7, 23:28 UT,
i = 21.25 +/- 0.19, at a midtime of August 8, 01:16 UT,
z = 20.52 +/- 0.19, at a midtime of August 8, 01:26 UT.
Second-epoch observations were performed the following night.
The optical transient was not detected anymore:
r 22.2, at a midtime of August 8, 23:34 UT,
i 22.4, at a midtime of August 9, 00:38 UT,
z 21.2, at a midtime of August 9, 01:20 UT.
Given magnitudes are calibrated against the Pan-STARRS catalogue.
GCN Circular 30637
Subject
GRB 210807A: continued Assy, AbAO and Mondy observations
Date
2021-08-12T19:34:29Z (4 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Belkin (IKI), A. Pozanenko (IKI), V. Kim (FAI, Pulkovo Observatory),
R. Ya. Inasaridze (AbAO), E. Klunko (ISTP), M. Krugov (FAI), N.
Pankov (HSE), D. Datashvili (AbAO), V. R. Ayvazian (AbAO), G. V.
Kapanadze (AbAO) report on behalf of IKI GRB FuN:
We continued observation of the GRB 210807A (Lien et al., GCN 30600;
Ripa et al., GCN 30624) with AZT-20 of Assy observatory, AZT-33IK of
Mondy observatory, and AS-32 of Abastumani observatory.
The optical transient GRB 210807A (Lien et al., GCN 30600; Hu et al.,
GCN 30602; Lipunov et al., GCN 30607; Kim et al., GCNs 30614, 30616;
LaPorte et al., GCN 30618; Schmidl et al., GCN 30628) was detected in
almost all of our stacked images. Preliminary photometric results are
presented below:
Date UT start t-T0 Filter Exp. OT Err. UL(3sig) Observ.
(mid, days) (s)
2021-08-07 23:46:09 0.58957 R 53*60 20.94 0.09 21.6 AbAO
2021-08-09 17:11:54 2.31822 R 30*120 22.6 0.35 22.5 Mondy
2021-08-10 17:22:17 3.32334 R 27*120 n/d n/d 22.7 Mondy
2021-08-10 21:33:07 3.50135 r(AB) 65*60 23.14 0.26 23.7 Assy
The photometry is based on the nearby stars of the USNO-B1.0 catalog.
USNO-B1.0_id R2
1482-0188929 16.72
1482-0188954 15.47
1482-0189006 15.38
and based on the same stars presented in PS1 catalog for r(AB) calibrations.
The light curve plotted based on available data for can be found at
http://grb.rssi.ru/GRB210807A/GRB210807A_LC.png
The light curve can be approximated by broken power law with power law
indices of -0.55 and -1.05 before and after break at about 0.22 days.