GRB 180720B
GCN Circular 22973
Subject
GRB 180720B: Swift detection of a burst
Date
2018-07-20T14:34:56Z (7 years ago)
From
David Palmer at LANL <palmer@lanl.gov>
M. H. Siegel (PSU), D. N. Burrows (PSU), A. Deich (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), S. J. LaPorte (PSU),
A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University),
K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
At 14:21:44 UT, the Swift Burst Alert Telescope (BAT) triggered and
located GRB 180720B (trigger=848890). Swift slewed immediately to the burst.
The BAT on-board calculated location is
RA, Dec 0.530, -2.933 which is
RA(J2000) = 00h 02m 07s
Dec(J2000) = -02d 56' 00"
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 150 sec. The peak count rate
was ~50000 counts/sec (15-350 keV), at ~11 sec after the trigger.
The XRT began observing the field at 14:23:11.0 UT, 86.5 seconds after
the BAT trigger. XRT found a bright, flaring and fading uncatalogued
X-ray source located at RA, Dec 0.5279, -2.9170 which is equivalent to:
RA(J2000) = +00h 02m 6.70s
Dec(J2000) = -02d 55' 01.2"
with an uncertainty of 5.0 arcseconds (radius, 90% containment). This
location is 58 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 6.59e-08 erg cm^-2 s^-1 (0.2-10
keV).
No UVOT data is available yet.
Burst Advocate for this burst is M. H. Siegel (siegel AT swift.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/too.html.)
[GCN OPS NOTE(21jul18): In response to GCN Circular 22975, this
archived copy of 22973 has been modified with the correct GRB maining
"A" --> "B".]
GCN Circular 22975
Subject
Correction: Swift trigger #848890 is GRB 180720B (not GRB 180720A)
Date
2018-07-20T14:48:26Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
M. H. Siegel (PSU), D. N. Burrows (PSU), A. Deich (PSU),
J.D. Gropp (PSU), J. A. Kennea (PSU), S. J. LaPorte (PSU),
A. Y. Lien (GSFC/UMBC), M. J. Moss (George Washington University),
K. L. Page (U Leicester), D. M. Palmer (LANL), B. Sbarufatti (PSU) and
A. Tohuvavohu (PSU) report on behalf of the Neil Gehrels Swift
Observatory Team:
The GRB name in GCN Circ. #22973 should be GRB 180720B because of
an earlier detection of GRB 180720A from AGILE/MCAL (GCN Circ. #22970).
We apologize for the mistake and any confusion caused by this.
GCN Circular 22976
Subject
GRB 180720B: LCO Haleakala possible bright optical candidate
Date
2018-07-20T15:30:47Z (7 years ago)
From
Renato Martone at Universita' di Ferrara <mrtrnt@unife.it>
R. Martone, C. Guidorzi (U. Ferrara), S. Kobayashi (LJMU), C.G. Mundell (U. Bath), A. Gomboc (U. Nova Gorica), I.A. Steele (LJMU), A. Cucchiara, D. Morris (U. of Virgin Islands) on behalf of a large collaboration report:
The LCO 2-m unit at Haleakala Observatory (Hawaii) began observing Swift GRB180720B (Siegel et al. GCN 22973) on July 20, 14:33:34 UT (11.8 minutes after the GRB trigger time) with the SDSS i' filter. On the border of the Swift-XRT error circle, we detect a 13-mag uncatalogued object at the following position:
RA(J2000)= +00:02:06.87
DEC(J2000)= -02:55:05.2
with an error radius of ~1��� as calibrated against nearby SDSS stars.
GCN Circular 22977
Subject
GRB 180720B: Kanata 1.5m optical/NIR observation
Date
2018-07-20T16:21:08Z (7 years ago)
From
Koji Kawabata at HASC,Hiroshima U <kawabtkj@hiroshima-u.ac.jp>
M. Sasada, T. Nakaoka, M. Kawabata, N. Uchida, Y. Yamazaki,
K. S. Kawabata (Hiroshima Univ.) report on behalf of Kanata team:
We performed optical and NIR imaging polarimetry to the field of the
GRB 180720B (Siegel et al. GCN 22973; Martone et al. GCN 22976) from
2018-07-20 14:22:57 UT (73 seconds after the trigger) with HOWPol
and HONIR attached to the 1.5-m Kanata telescope at Higashi-Hiroshima
Observatory, Japan. We detected a bright optical counterpart of the
GRB within the the Swift-XRT error circle of the X-ray afterglow. The
magnitude of the optical counterpart was R~9.4 mag in our first frame
taken with 30 second exposure and then smoothly declined. Further
analysis is ongoing.
GCN Circular 22979
Subject
GRB 180720B : TSHAO optical observations
Date
2018-07-20T21:36:57Z (7 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
I. Reva (FAPHI), A. Pozanenko (IKI), A. Volnova (IKI), E. Mazaeva (IKI),
A. Kusakin (FAPHI), M. Krugov (FAPHI) report on behalf of larger GRB
follow-up collaboration:
We observed the field of GRB 180720B (Siegel et al., GCN 22973) with
Zeiss-1000 telescope of Tien Shan Astronomical Observatory starting on July
20 (UT) 19:46:17. We obtained several images in R and B-filters. The
optical afterglow (Martone et al. GCN 22976; Sasadaet al., GCN 22977) is
clearly detected in both filters. Preliminary photometry of the afterglow
at (UT, mid time) 19:59 is R =17.1 +/- 0.1. The photometry is based on
nearby USNO-B1.0 (R2) stars.
GCN Circular 22980
Subject
GRB 180720B : Fermi-LAT detection
Date
2018-07-20T22:28:56Z (7 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico & INFN Bari) and J. L. Racusin (NASA/GSFC)
report on behalf of the Fermi-LAT team:
"At 14:21:44.55 UT on July 20, 2018, Fermi-LAT detected
high-energy emission from GRB 180720B, which was also
detected by Swift (Siegel et al. 2018, GCN 22973)
and by Fermi-GBM (trigger 553789304 / 180720598).
The best LAT on-ground location is found to be
RA, Dec = 0.58, -2.95 (J2000)
with an error radius of 0.11 deg (90 % containment, statistical error only).
This was 50 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 very high significance.
The highest-energy photon is a 5 GeV event which is
observed 137 seconds after the GBM trigger.
Given that GRB 180720B is detected by both Swift and Fermi,
and it is very bright in the LAT, we encourage follow-up observations.
The Fermi-LAT point of contact for this burst is
Elisabetta Bissaldi (elisabetta.bissaldi@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 22981
Subject
GRB 180720B: Fermi GBM observation
Date
2018-07-20T22:50:18Z (7 years ago)
From
Oliver J Roberts at USRA/NASA <oliver.roberts@nasa.gov>
O.J. Roberts (USRA/NASA) and C. Meegan (UAH) report on behalf
of the Fermi GBM Team:
"At 14:21:39.65 UT on 20 July 2018, the Fermi Gamma-Ray Burst Monitor
triggered and located GRB 180720B (trigger 553789304 / 180720598),
which was also detected by Swift (Siegel et al. 2018, GCN 22973/22975)
and the LAT (Bissaldi et al., GCN 22980). The GBM on-ground location is
consistent with the Swift position.
The angle from the Fermi LAT boresight at the GBM trigger time using the
Swift-XRT position is 50 degrees.
The GBM light curve consists of a very bright, FRED-like peak with
numerous overlapping pulses with a duration (T90) of 49 s (50-300 keV).
The time-averaged spectrum from T0 to T0+55 s is best fit by a Band
function with Epeak = 631 +/- 10 keV, alpha = -1.11 +/- 0.01 and
beta = -2.30 +/- 0.03.
The event fluence (10-1000 keV) over the T90 interval is
(2.985 +/- 0.001)E-04 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.4 s in the 10-1000 keV band is 125 +/- 1 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog."
GCN Circular 22983
Subject
GRB 180720B: MITSuME Akeno optical observations
Date
2018-07-21T02:16:27Z (7 years ago)
From
Ryosuke Itoh at Tokyo Institute of Tech. <itoh@hp.phys.titech.ac.jp>
R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita,
K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano,
Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the optical counterpart of GRB 180720B
(Siegel et al., GCN 22973)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the MITSuME 50cm telescope of Akeno Observatory, Yamanashi, Japan.
The observation started on 2018-07-20 18:08:46 UT, (~3.8 hours after
the burst). We detected the previously reported afterglow
(Martone et al., GCN 22976, Sasada et al., GCN 22977, Reva et al., GCN 22979)
in the g', Rc and Ic band.
The photometric results of the OT are listed below.
We used UCAC-4 catalog for flux calibration.
#T0+[hour] MID-UT T-EXP[sec] g' Rc Ic
-------------------------------------------------------------------
3.8 18:14:30 540 16.53+/-0.06 16.67+/-0.06 16.25+/- 0.08
-------------------------------------------------------------------
T0+ : Elapsed time after the burst [hour]
T-EXP: Total Exposure time [sec]
GCN Circular 22984
Subject
GRB 180720B: Swift-XRT refined Analysis
Date
2018-07-21T02:17:13Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia
(ASDC), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAB), A. Tohuvavohu
(PSU), S. J. LaPorte (PSU), J.A. Kennea (PSU), P.A. Evans (U.
Leicester) and M.H. Siegel report on behalf of the Swift-XRT team:
We have analysed 7.2 ks of XRT data for GRB 180720B (Siegel et al. GCN
Circ. 22973), from 90 s to 19.4 ks after the BAT trigger. The data
comprise 3.3 ks in Windowed Timing (WT) mode with the remainder in
Photon Counting (PC) mode. The refined XRT position is RA, Dec =
0.5286, -2.9189 which is equivalent to:
RA (J2000): 00 02 06.86
Dec(J2000): -02 55 08.1
with an uncertainty of 3.5 arcsec (radius, 90% confidence).
The late-time light curve (from T0+5.6 ks) can be modelled with an
initial power-law decay with an index of alpha=1.18 (+0.16, -0.28),
followed by a break at T+7030 s to an alpha of -0.17 (+0.26, -1.33).
A spectrum formed from the WT mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.770 (+/-0.011). The
best-fitting absorption column is 1.42 (+/-0.04) x 10^21 cm^-2, in
excess of the Galactic value of 3.9 x 10^20 cm^-2 (Willingale et al.
2013). The PC mode spectrum has a photon index of 1.85 (+/-0.07) and a
best-fitting absorption column of 1.75 (+0.23, -0.22) x 10^21 cm^-2.
The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor
deduced from this spectrum is 3.8 x 10^-11 (4.9 x 10^-11) erg cm^-2
count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.75 (+0.23, -0.22) x 10^21 cm^-2
Galactic foreground: 3.9 x 10^20 cm^-2
Excess significance: 10.1 sigma
Photon index: 1.85 (+/-0.07)
If the light curve continues to decay with a power-law decay index of
-0.17, the count rate at T+24 hours will be 21 count s^-1,
corresponding to an observed (unabsorbed) 0.3-10 keV flux of 8.4 x
10^-10 (1.1 x 10^-9) erg cm^-2 s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00848890.
This circular is an official product of the Swift-XRT team.
[GCN OPS NOTE(21jul18): In response to GCN Circular 22986, this
archived copy of 22984 has been modified with the correct GRB maining
"A" --> "B".]
GCN Circular 22985
Subject
GRB 180720B: OSN detection, fading slower?
Date
2018-07-21T02:51:06Z (7 years ago)
From
Alexander Kann at IAA-CSIC <kann@iaa.es>
D. A. Kann, L. Izzo (both HETH/IAA-CSIC), V. Casanova (IAA-CSIC), and A. de
Ugarte Postigo (HETH-IAA/CSIC and DARK/NBI) report on behalf of HETH:
We observed the position of the extremely bright GRB 180720B (Swift-BAT
detection: Siegel et al., GCN #22973, GCN #22975; Fermi-LAT detection:
Bissaldi and Racusin, GCN #22980; Fermi-GBM detection: Roberts et al.,
GCN #22981) with the T90 telescope of the Observatorio Sierra Nevada
(OSN) near Granada, Spain.
The optical afterglow (Martone et al., GCN #22976; Sasada et al., GCN
#22977; Reva et al., GCN #22979; Itoh et al., GCN #22983) is clearly
detected in single 180 s images. For an Rc image at mid-time 0.455188
days after the INTEGRAL SPI/ACS trigger (14:21:40 UT), we derive Rc =
17.53 +/- 0.03 mag.
We note that this is only ~0.4 mag fainter than the value found by Reva
et al. at 0.23 days after the GRB, indicating the decay may have slowed
down. This feature also seems to be seen in the XRT light curve (Page et
al., GCN #22984).
Further observations, even with smaller telescopes, are strongly
encouraged.
Magnitudes were obtained against SDSS standard stars transformed
following the equations of Lupton (2005).
[GCN OPS NOTE(21jul18): Due to a processing problem with some
in-line UTF formatting characters, the "slower?" was deleted
from the SUBJECT-line in the distributed circulars. It has been
replaced in these archived copies.]
[GCN OPS NOTE(21jul18): Per author's request, A. de U.P. was added
to the author list.]
GCN Circular 22986
Subject
GCN 22984 was for GRB 180720B
Date
2018-07-21T02:59:07Z (7 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U Leicester) reports on behalf of the Swift-XRT team :
The XRT refined analysis reported in GCN Circ. 22984 was the analysis of GRB 180720B, not A as reported in the circular. Apologies for the confusion.
GCN Circular 22988
Subject
GRB 180720B: LCO optical afterglow observations
Date
2018-07-21T04:59:42Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
Nicolas Crouzet (IAC) and Daniele B. Malesani (DAWN/NBI and DARK/NBI)
report:
We observed the optical afterglow of GRB 180720B (Siegel et al., GCN
22973; Martone et al., GCN 22976) using the 0.4-m telescope located at
the Teide Observatory, part of the Las Cumbres Observatory (LCO)
telescope network.
A single 600-s exposure in the SDSS r band was obtained with mean time
July 21.094 UT (0.495 days after the GRB). The PSF of the image is not
optimal, being double-peaked.
Aperture photometry, compared to nearby stars from the Pan-STARRS
catalog, provides for the afterglow a preliminary magnitude r = 17.85 +-
0.10 AB.
GCN Circular 22993
Subject
GRB 180720B: MAXI/GSC detection
Date
2018-07-21T11:19:21Z (7 years ago)
From
H. Negoro at Nihon U. <negoro@phys.cst.nihon-u.ac.jp>
H. Negoro (Nihon U.), A. Tanimoto (Kyoto U.),
M. Nakajima, W. Maruyama, A. Sakamaki (Nihon U.),
T. Mihara, S. Nakahira, F. Yatabe, Y. Takao, M. Matsuoka (RIKEN),
N. Kawai, M. Sugizaki, Y. Tachibana, K. Morita (Tokyo Tech),
T. Sakamoto, M. Serino, S. Sugita, Y. Kawakubo, T. Hashimoto, A. Yoshida (AGU),
S. Ueno, H. Tomida, M. Ishikawa, Y. Sugawara, N. Isobe, R. Shimomukai (JAXA),
Y. Ueda, T. Morita, S. Yamada (Kyoto U.), Y. Tsuboi, W. Iwakiri, R. Sasaki,
H. Kawai, T. Sato (Chuo U.), H. Tsunemi, T. Yoneyama (Osaka U.),
M. Yamauchi, K. Hidaka, S. Iwahori (Miyazaki U.), T. Kawamuro (NAOJ),
K. Yamaoka (Nagoya U.), M. Shidatsu (Ehime U.)
report on behalf of the MAXI team:
The MAXI/GSC nova alert system triggered on GRB 180720B (Siegel et al., GCN 22973/20975;
Bissaldi et al., GCN 22980; Roberts et al., GCN 22981) at 14:28:15 UT on 2018 July 20,
396 sec after the Fermi/GRB trigger.
Assuming that the source flux was constant over the transit, we obtain the source position at
(R.A., Dec) = (0.467 deg, -2.846 deg) = (00 01 52, -02 50 45) (J2000)
with a statistical 90% C.L. elliptical error region
with long and short radii of 0.21 deg and 0.16 deg, respectively.
The roll angle of the long axis from the north direction is 166.0 deg counterclockwise.
There is an additional systematic uncertainty of 0.1 deg (90% containment radius).
The above position is 5.6 arcminutes from the Swift/XRT
position of GRB 180720B (Siegel et al. GCN 22973).
The X-ray flux averaged over the scan was 191 +- 27 mCrab (4.0-10.0keV, 1 sigma error).
MAXI/GSC also detected the source at 25 +/- 12 mCrab in the next scan transit at 16:01.
The 2-20 keV GSC spectrum obtained in the scan transit at 14:28 is well described by
an absorbed power-law with a photon index of 2.11 +/- 0.25 with n_H fixed at the total
Galactic column density to the direction of 3.5e20 atoms/cm2.
GCN Circular 22996
Subject
GRB 180720B: VLT/X-shooter redshift
Date
2018-07-21T14:34:50Z (7 years ago)
From
Daniele Malesani at Dark Cosmology Centre, Niels Bohr Inst <malesani@dark-cosmology.dk>
P. M. Vreeswijk (Radboud Univ. Nijmegen), D. A. Kann (HETH/IAA-CSIC), K.
E. Heintz (Univ. Iceland and DAWN/NBI), A. de Ugarte Postigo
(HETH-IAA/CSIC and DARK/NBI), B. Milvang-Jensen (DAWN/NBI), D. B.
Malesani (DARK/NBI and DAWN/NBI), S. Covino (INAF/Brera), A. J. Levan
(Univ. Warwick), G. Pugliese (Amsterdam), report on behalf of the
Stargate collaboration:
We observed the optical counterpart of GRB 180720B (Siegel et al., GCN
22973; Martone et al., GCN 22976) with the ESO VLT UT2 equipped with the
X-shooter spectrograph. Two spectra of 600 s each were secured starting
on 2018 July 21.384 UT (0.786 days after the GRB), covering the
wavelength range 3000-25000 AA.
A bright continuum is detected across the entire observed range. Several
absorption features are detected, which can be identified as due to Fe
II, Mg II, Mg I, and Ca II, all at z = 0.654. We also identify
fine-structure transitions due to both Fe II* and Ni II**, thus making
the redshift association with the GRB secure.
We acknowledge the ESO observing staff at Paranal, in particular Juan
Carlos Munoz, Emanuela Pompei, and Luca Sbordone.
GCN Circular 22998
Subject
GRB 180720B: Swift-BAT refined analysis
Date
2018-07-21T17:11:45Z (7 years ago)
From
Amy Lien at GSFC <amy.y.lien@nasa.gov>
S. D. Barthelmy (GSFC), J. R. Cummings (CPI),
H. A. Krimm (NSF/USRA), A. Y. Lien (GSFC/UMBC),
C. B. Markwardt (GSFC), D. M. Palmer (LANL),
T. Sakamoto (AGU), M. H. Siegel (PSU),
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 180720B (trigger #848890)
(Siegel et al., GCN Circ. 22973). The BAT ground-calculated position is
RA, Dec = 0.528, -2.925 deg which is
RA(J2000) = 00h 02m 06.8s
Dec(J2000) = -02d 55' 31.3"
with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment).
The partial coding was 8%.
The mask-weighted light curve shows a multi-peaked structure, with the main peak
occurs around ~T+11 s. The burst emission starts around ~T-20 s, although there might
be additional emission before the GRB came into the BAT FOV at ~T-57 s. The burst lasts
beyond the available event data range (until T+962 s). Analysis using the BAT survey data
shows that the burst emission extends at least till ~ T+2000 s, when Swift went into SAA
and no more data were collected. The burst came back into the BAT FOV at ~ T0+5626 s, and
the burst was no longer detected (signal-to-noise ratio < 3 sigma).
The time-averaged spectrum from T-20.0 to T+961.1 sec is best fit by a simple
power-law model. The power law index of the time-averaged spectrum is
1.36 +- 0.03. The fluence in the 15-150 keV band is 8.6 +- 0.1 x 10^-05 erg/cm2.
The 1-sec peak photon flux measured from T+10.94 sec in the 15-150 keV band
is 67.9 +- 2.6 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/848890/BA/
GCN Circular 23004
Subject
GRB 180720B: MITSuME Ishigaki optical observations
Date
2018-07-22T00:04:42Z (7 years ago)
From
Ryosuke Itoh at Tokyo Institute of Tech. <itoh@hp.phys.titech.ac.jp>
T. Horiuchi, H. Hanayama, M. Honma (IAO, NAOJ),
R. Itoh, K. L. Murata, Y. Tachibana, S. Harita, K. Morita
K. Shiraishi, K. Iida, M. Oeda, R. Adachi, S. Niwano,
Y. Yatsu, and N. Kawai (Tokyo Tech)
report on behalf of the MITSuME collaboration:
We observed the optical counterpart of GRB 180720B
(Siegel et al., GCN 22973)
with the optical three color (g', Rc, and Ic) CCD cameras attached to
the Murikabushi 1m telescope of Ishigakijima Astronomical Observatory, Japan.
The observation started on 2018-07-20 17:11:26 UT, (~2.8 hours after
the burst). We detected the previously reported afterglow
(Martone et al., GCN 22976, Sasada et al., GCN 22977, Reva et al., GCN 22979)
in the Rc and Ic band.
The photometric results of the OT are listed below.
We used UCAC-4 catalog for flux calibration.
#T0+[hour] MID-UT T-EXP[sec] Rc Ic
-------------------------------------------------------------------
2.8 17:14:58 240 16.23+/-0.03 16.24+/-0.05
-------------------------------------------------------------------
T0+ : Elapsed time after the burst [hour]
T-EXP: Total Exposure time [sec]
GCN Circular 23011
Subject
Konus-Wind observation of GRB 180720B
Date
2018-07-22T13:43:39Z (7 years ago)
From
Dmitry Frederiks at Ioffe Institute <fred@mail.ioffe.ru>
D. Frederiks, S. Golenetskii, R.Aptekar, A. Kozlova,
A.Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline,
on behalf of the Konus-Wind team, report:
The long, extremely bright GRB 180720B
(Swift-BAT detection: Siegel et al., GCN 22973, GCN 22975;
Fermi-LAT detection: Bissaldi and Racusin, GCN 22980;
Fermi-GBM detection: Roberts et al., GCN 22981)
triggered Konus-Wind at T0=51705.261 s UT (14:21:45.261).
The burst light curve shows a multi-peaked structure
with a total duration (T100) of ~125 s.
The emission is seen up to ~15 MeV.
As observed by Konus-Wind, the burst had a fluence of
(5.43 �� 0.26)x10^-4 erg/cm2 and a 64-ms peak energy flux,
measured from T0+15.168, of (9.70 �� 0.52)x10^-5 erg/cm2
(both in the 20 keV - 10 MeV energy range).
The time-integrated spectrum (measured from T0 to T0+119.808 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 = -1.01 (-0.06,+0.06),
the high energy photon index beta = -2.07 (-0.08,+0.07),
the peak energy Ep = 451 (-45,+52) keV,
chi2 = 102/97 dof.
The spectrum near the peak count rate (measured from T0+14.592 s
to T0+15.360 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 = -0.82 (-0.09,+0.10),
the high energy photon index beta = -2.27 (-0.22,+0.13),
the peak energy Ep = 779 (-127,+169) keV,
chi2 = 92/76 dof.
Assuming the redshift z=0.654 (Vreeswijk et al., GCN 22996)
and a standard cosmology model with H_0 = 70 km/s/Mpc,
Omega_M = 0.30, and Omega_Lambda = 0.70,
we estimate the following rest-frame parameters:
the isotropic energy release E_iso is ~6.0x10^53 erg,
the peak luminosity L_iso is ~1.8x10^53 erg/s,
and the rest-frame peak energy of the time-integrated spectrum,
Ep,z, is ~746 keV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB180720_T51705/
All the quoted errors are estimated at the 90% confidence level.
All the presented results are preliminary.
GCN Circular 23017
Subject
GRB 180720B: COATLI Optical Detection
Date
2018-07-22T20:52:09Z (7 years ago)
From
Alan M. Watson at Instituto de Astronomia UNAM <alan@astro.unam.mx>
Alan M. Watson (UNAM), Nat Butler (ASU), Rosa L. Becerra (UNAM), William
H. Lee (UNAM), Carlos Rom��n-Z����iga (UNAM), Alexander Kutyrev (GSFC), and
Eleonora Troja (GSFC) report:
We observed the field of GRB 180720B (Siegel et al., GCN Circ. 22973)
with the COATLI 50-cm telescope and interim imager at the Observatorio
Astron��mico Nacional on the Sierra de San Pedro M��rtir
(http://coatli.astroscu.unam.mx) from 2018-07-22 06:25 to 11:23 UTC
(from 40.07 to 45.03 hours after the trigger), obtaining a total of 4.06
hours of exposure in the w filter.
We detect the optical counterpart (Martone et al., GCN Circ. 22976) with
w = 20.07 +/- 0.02
These magnitudes are calibrated against the USNO-B1 catalog (adjusted to
an approximate AB system) and are not corrected for Galactic extinction
in the direction of the GRB.
We thank the COATLI technical team (Fernando ��ngeles, Oscar Chapa,
Salvador Cuevas, Alejandro Farah, Jorge Fuentes, Rosal��a Langarica,
Fernando Quir��s, and Carlos Tejada) and the staff of the Observatorio
Astron��mico Nacional.
GCN Circular 23019
Subject
GRB 180720B: Testing the universality of the newly born neutron star in BdHNe
Date
2018-07-22T22:30:27Z (7 years ago)
From
Remo Rufinni at ICRA <ruffini@icra.it>
R. Ruffini, Y. Aimuratov, C. L. Bianco, Y. C. Chen, D. M. Fuksman, M. Karlica, R. Moradi, D. Primorac, J.A. Rueda, N. Sahakyan, Y. Wang, on behalf of the ICRANet team, report:
GRB 180720B (Siegel et al., GCN 22973) is a long GRB with isotropic energy ~6.0e53 erg (Frederiks et al., GCN 23011). It belongs to the long GRB subclass of Binary Driven Hypernovae (BdHNe) (Ruffini et al., 2016, ApJ, 832, 136), with energies larger than 1e52 erg and GeV radiation, which allows the determination of the black hole mass (Ruffini et al., arXiv:1803.05476). It includes GRB 130427A associated to SN 2013cq (Ruffini et al., GCN 14526, Xu et al., GCN 14646), as well as GRB 160625B (Troja et al., 2017). The comparison of X-ray light-curves is attached [1], plotted in the rest frame of the sources. These sources are polar views from the normal to the plane of the binary progenitor (Ruffini et al., arXiv:1803.05476). In GRB 180720B, which has redshift z = 0.654 (GCN 22996), being a BdHN, a supernova is expected to peak, using the averaged observed value (Cano et al., 2016), at 21.8 +/ 4.3 day after the trigger (11 August 2018, uncertainty from August 7th to August 15th): the prolonged observations of the afterglow in all bands, especially the optical band, is recommended to further probe the nature of the supernova and of the newly born neutron star, strikingly constant in all BdHNe (see also Becerra et al., arXiv:1803.04356).
[1] Link: http://www.icranet.org/documents/20180721.jpg
Caption of figure: Three BdHNe with polar views from the normal to the plane of the binary progenitor, pointing to the similarities. GRB 130427A with redshift z=0.34 is associated to the companion supernova SN 2013cq. GRB 160625B has redshift z=1.406, which is too far for the optical observation of the associated supernova (Woosley & Bloom, 2006). GRB 180720B with redshift z=0.654 is expected to have the observation of an associated supernova.
GCN Circular 23020
Subject
GRB 180720B: ISON-Castelgrande optical observations
Date
2018-07-22T23:39:09Z (7 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
S. Schmalz (KIAM), F. Graziani (GAUSS). A. Pozanenko (IKI), A. Volnova
(IKI), E. Mazaeva (IKI), I. Molotov (KIAM) report on behalf of larger GRB
follow-up collaboration:
We observed the field of GRB 180720B (Swift-BAT detection: Siegel et al.,
GCN 22973, GCN 22975; Fermi-LAT detection: Bissaldi and Racusin, GCN 22980;
Fermi-GBM detection: Roberts et al., GCN 22981; MAXI/GSC detection: Negoro
et al., GCN 22993; Konus-Wind detection: Frederiks et al., GCN 23011)
with ORI-22 (22 cm) telescope of ISON-Castelgrande observatory starting on
July 20 (UT) 23:04:30. We obtained 150 images of 60 s exposure in Clear
filter. The optical afterglow (e.g. Martone et al. GCN 22976; Sasada et
al., GCN 22977; Reva et al., GCN 22979; Itoh et al., GCN 22983; Kann et
al., GCN 22985) is detected in separate images up to the end of series.
The coordinates of the optical afterglow are (J2000)
:02:06.792 -02:55:04:99 with uncertainties of about 0.5 arcsec in both
coordinates. Preliminary photometry of the afterglow at (UT, mid time)
23:22:21 is R =17.40 +/- 0.15. The photometry is based on nearby USNO-B1.0
(R2) stars.
GCN Circular 23021
Subject
GRB 180720B: REM photometry
Date
2018-07-23T09:43:43Z (7 years ago)
From
Stefano Covino at Brera Astronomical Observatory <stefano.covino@gmail.com>
S.Covino, D. Fugazza (INAF/OAB), on behalf of the REM team, report:
We observed the field of GRB180720B (Siegel et al. GCN 22973) with the REM 60cm robotic telescope located at the ESO premise of La Silla (Chile).
The observations were performed starting from about 13.5 hours after the event and were carried in the g, r, i, z, J, H and K bands.
The optical counterpart (Martone et al. GCN 22976) is still detected in the optical and in the NIR bands. A preliminary photometry on the first H band set of frame gives:
H = 15.65 +- 0.22 at 13.7 hours from the GRB time.
Magnitudes are calibrated against the 2MASS catalogue.
GCN Circular 23023
Subject
GRB 180720B: MASTER Global Net OT observations
Date
2018-07-23T11:57:20Z (7 years ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
V. Lipunov, E. Gorbovskoy, N.Tiurina, D.Vlasenko, V.Kornilov, A.Kuznetsov,
V.Chazov, I. Gorbunov, D.Zimnukhov, D.Kuvshinov, P.Balanutsa,
V.Vladimirov,
Lomonosov Moscow State University,SAI
D. Buckley,
South African Astronomical Observatory (SAAO)
R. Rebolo, M. Serra, N. Lodieu, G. Israelian, L. Suarez-Andres
The Instituto de Astrofisica de Canarias (IAC)
A. Tlatov, V.Senik, D. Dormidontov
Kislovodsk Solar Station of the Pulkovo Observatory
R. Podesta, F. Podesta, C. Lopez, C.Francile
Observatorio Astronomico Felix Aguilar (OAFA)
H.Levato,
Instituto de Ciencias Astronomicas, de la Tierra y del Espacio (ICATE)
O. Gres, N.M.Budnev , Yu.Ishmuhametova
Irkutsk State University (ISU)
A. Gabovich, V. Yurkov, Yu. Sergienko
Blagoveschensk Educational State University (BSPU)
MASTER-Amur robotic telescope (MASTER-Net: http://observ.pereplet.ru,
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in
Russia (Blagoveschensk State Pedagogical University) was pointed to the
Swift GRB180720B (Siegel et al., GCN Circ #22973) 113 sec after trigger
time at 2018-07-20 14:23:37 UT.
So as the GRB was 4.6 degrees above the horizont, the good observations
started on 2018-07-20 15:21:50UT.
Galaxy latitude b = -63.07 degree.
The moon (58 % bright part) is 9 degrees above the horizon. The distance
between moon and object was 143.
The sun altitude was -17.19 degree.
The object observed till 2018-07-20 15:47:58
MASTER-SAAO robotic telescope (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
GRB180720B 27260 sec after trigger time at 2018-07-19 20:56:09 UT as
MASTER's LAT (Bissaldi et al GCN22980)alert inspection with polarization
filters.
MASTER-SAAO auto-detection system ( Lipunov et al., "MASTER Global Robotic
Net", Advances in Astronomy, 2010, 30L )
discovered bright OT source at (RA, Dec) = 00h 02m 06.92s -02d 55m 05.6s
on 2018-07-19 20:56:09 UT.
The OT magnitude is ~16.8m .
There is no minor planet at this place.
We have reference image on 2016-05-04.12293 UT with unfiltered mlim = 18.1m.
The observations made on zenit distance = 16.7 degrees, galaxy latitude b
= -74.37 degree. The moon (61 % bright part) was 24 degrees above the
horizon.The sun altitude was -63.7 degree.
MASTER-SAAO reobserved this area on 2018-07-21 22:28:10-22:54:51UT as
MASTER's MAXI (Negoro et al GCN 22993) alert inspection with mlim=20.2
and unfiltered m_OT~19.1
The discovery and reference images are
http://master.sai.msu.ru/static/OT/MASTERGRB180720B.jpg
MASTER-Kislovodsk robotic telescope (MASTER-Net:
http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy,
vol. 2010, 30L) located in Russia (Pulkovo Solar Station) was pointed to
the GRB180720B (Siegel et al., GCN Circ #22973) 27457 sec after trigger
time at 2018-07-20 21:59:21 UT .
On our first (180s exposure) set MASTER-Kislovodsk auto-detection system
discovered OT with m_OT~17.0, automatical mlim~17.6.
The observations made on zenit distance = 25.66 degrees, galaxy latitude b
= -63.07 degree.
The moon (61 % bright part) is below the horizon(The altitude of Moon is
-8). The distance between moon and object is 138
The sun altitude is -24.87 degree.
The object observed till 2018-07-20 22:19:52
MASTER-IAC robotic telescope (MASTER-Net: http://observ.pereplet.ru,
Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in
Spain (IAC Teide Observatory) was pointed to the GRB180720B (Siegel et
al., GCN Circ #22973) 44691 sec after trigger time at 2018-07-21 02:46:35
UT . On our first (60s exposure) MASTER-IAC auto-detection system
discovered optical transient within Swift error-box with automatical
magnitude ~18.0.
The observations made on zenit distance = 43.01 degrees, galaxy latitude b
= -63.07 degree.
The moon (63 % bright part) is below the horizon(The altitude of Moon is
-15). The distance between moon and object is 136
The sun altitude is -36.01 degree.
The object observed till 2018-07-21 03:03:36
The visibility GRB error box (coord:0.5279, -2.9170 error_box: 0.05)
at trigger time at different MASTER sites:
obj: -47.70 sun: 29.73 - Tavrida (Crimea, Russia)
obj: -41.62 sun: 72.28 - IAC, Teide, (Tenerife, Spain)
obj: -54.25 sun: 15.39 - SAAO (Sutherland, SA)
obj: -46.85 sun: 23.59 - Kislovodsk (Russia)
obj: -29.98 sun: 15.28 - Ural(Kourovka, Russia)
obj: -10.74 sun: -8.46 - Tunka (near Baykal Lake, Russia)
obj: 4.55 sun: -17.19 - Amur(Blagoveschensk)
obj: 6.72 sun: 27.64 - OAFA (Argentina)
The message may be cited.
GCN Circular 23024
Subject
GRB 180720B: D50 optical observations
Date
2018-07-23T20:21:57Z (7 years ago)
From
Jan Strobl at AI AS CR,Ondrejov <jan@strobl.cz>
M. Jelinek, J. Strobl, R. Hudec, C. Polasek (ASU CAS Ondrejov)
report:
We observed the position of the bright GRB 180720B (Siegel et al., GCN
22973 & GCN 22975) with the D50 telescope of the Astronomical Institute
Ondrejov, near Prague, Czech Republic. We performed a series of ~300x 20s
unfiltered exposures as soon as the position became accessible above local
horizon, between 9.8 and 12h after the trigger.
The optical afterglow (Martone et al., GCN 22976; Sasada et al., GCN
22977; Reva et al., GCN 22979; Itoh et al., GCN 22983) is clearly detected
in single 20 s images.
We confirm the stationary behaviour during our observations as reported by
Kann et al. (GCN 22985) - the afterglow might have faded as few as 0.04
mag between 10 and 11h after the GRB trigger.
GCN Circular 23033
Subject
GRB 180720B: KAIT Optical Observations
Date
2018-07-25T00:12:38Z (7 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, observed the field of Swift GRB 180720B
(Siegel et al., GCN 22973) each night from 21 to 24 UT, at a mean time
of 0.855, 1.886, 2.883 and 3.874 days, respectively, after the burst.
Observations were performed with a sequence in the B, V, R, I and
clear (roughly R) filters, and the exposure time was 60 s per image.
The optical afterglow (Martone et al., GCN 22976) was clearly detected
and we measure its clear band mag to be 18.5, 19.6, 20.5 and 20.9,
respectively, calibrated to the SDSS catalog.
GCN Circular 23036
Subject
GRB 180720B long follow up requested
Date
2018-07-25T08:52:55Z (7 years ago)
From
Arnon Dar at Technion-Israel Inst. of Tech <arnon@physics.technion.ac.il>
Long follow up of the afterglow of the extremely bright GRB
180720B (Swift-BAT detection: Siegel et al., GCN #22973, GCN
#22975; Fermi-LAT detection: Bissaldi and Racusin, GCN #22980;
Fermi-GBM detection: Roberts et al., GCN #22981; Konus Wind
detection: Frederiks et al. GCN 23011) is urged. It will provide
another critical test of GRB theories. Its current late-time X-ray
afterglow, measured with Swift XRT, decays like a single power-law
with a temporal index alpha=1.34+/-0.01 and an unabsorbed spectral
index beta=0.82+/-0.04 (Evans et al. Swift-XRT GRB lightcurve
repository). It satisfies well the Cannonball model closure relation
alpha=beta+1/2 (e.g., Dado and Dar, PhRvD, 94, 3007 (2016)) for
the late time unabsorbed afterglows of SN-GRBs (while those of
SN-less GRBs satisfy alpha=2, e.g., Dado and Dar arXiv:1807.08726).
An SN akin to SN1998bw may be resolved from the optical afterglows
around day ~15. An achromatic break in the late time afterglow
is expected only if the host galaxy is aligned near face on.
[GCN OPS NOTE(26jul18): The operator has corrected the GRB name
in the Subject-line; and corrected Frederiks reference from 230110
to 23011.]
GCN Circular 23037
Subject
GRB 180720B: AMI-LA 15.5 GHz observation
Date
2018-07-25T09:12:00Z (7 years ago)
From
Itai Sfaradi at Hebrew U of Jerusalem <itai.sfaradi@mail.huji.ac.il>
Itai Sfaradi (HUJI), Joe Bright (Oxford), Assaf Horesh (HUJI), Rob Fender
(Oxford) ,
Sara Motta (Oxford), David Titterington, Yvette Perrott (MRAO, Cambridge)
report:
We observed the position of GRB180720B (GCN CIRCULAR #22973) with the
Arcminute Microkelvin Imager Large Array (AMI-LA; Zwart et al. 2008; Hickish
et al. 2018) at 15.5 GHz on 2018-07-22.21 for 3.9 hours.
We clearly detect a source at the phase center, fitting the source with the
CASA task IMFIT
provides an integrated flux density of ~ 1 mJy and a position of RA:
00:02:07.02,
Dec: -02 55 02.224 with a synthesized beam major and minor FWHM of 93������ and
27������ respectively
(consistent with the position reported in GCN CIRCULAR #22973).
The custom pipeline REDUCE_DC (e.g. Perrott et al. 2015) was used to
calibrate
and flag the data, with 3C286 as the absolute flux calibrator and J2357-0152
as the interleaved phase calibrator.
We plan to continue monitoring this source, and would like to thank the
MRAO staff for carrying out these observations.
GCN Circular 23040
Subject
GRB 180720B: OAJ optical observations
Date
2018-07-26T08:56:58Z (7 years ago)
From
Luca Izzo at IAA-CSIC <Luca.Izzo@ICRA.it>
L. Izzo, D. A. Kann (HETH/IAA-CSIC), A. de Ugarte Postigo (HETH/IAA-CSIC, DARK/NBI), C. C. Thoene, K. Bensch, M. Blazek (HETH/IAA-CSIC), M. C. Diaz-Martin, and S. Rodriguez-Llano (OAJ) report:
We observed the field of the Swift-BAT GRB 180720B (Siegel et al. GCN 22973), detected also by Fermi-LAT (Bissaldi et al. GCN 22980), with the 0.8m telescope of the Observatorio Astrofisico de Javalambre (Teruel, Spain). Observations consisted of a series of 3x300 s griz exposures, starting at 01:12:55 UT (10.85 hr after the GRB trigger). The afterglow is clearly detected at a position consistent with the one reported by Martone et al. (GCN 22976).
We measure a magnitude of r(AB) = 17.77+/- 0.05 mag at an average time of 01:37:14 UT (11.26 hr after the GRB trigger), as compared to nearby SDSS stars.
GCN Circular 23041
Subject
NuSTAR observations of GRB 180720B
Date
2018-07-26T16:39:39Z (7 years ago)
From
Eric C Bellm at UW <ecbellm@uw.edu>
E. C. Bellm (UW) and S. B. Cenko (GSFC) report:
We have analyzed 38 ksec of NuSTAR data for GRB 180720B (M. H. Siegel et
al., GCN Circ. 22973), from 243 ksec to 318 ksec after the BAT trigger.
NuSTAR detects emission from the X-ray afterglow to approximately 30 keV.
The NuSTAR spectrum can be well-modeled from 3-30 keV by an absorbed power
law with spectral index 1.80+/-0.06, consistent with the value reported
by XRT (K. L. Page et al., GCN Circ. 22984). The 3-30 keV flux was
4.8+/-0.2 x 10^-12 erg cm^-2 s^-1.
We thank Karl Forster and the NuSTAR operations team for their assistance
executing these TOO observations.
GCN Circular 23042
Subject
GRB 180720B: CALET Gamma-Ray Burst Monitor detection
Date
2018-07-27T04:11:45Z (7 years ago)
From
Takanori Sakamoto at AGU <tsakamoto@phys.aoyama.ac.jp>
M. L. Cherry (LSU), A. Yoshida, T. Sakamoto, V. Pal'shin, S. Sugita, Y. Kawakubo,
A. Tezuka, S. Matsukawa, H. Onozawa, T. Ito, H. Morita, Y. Sone (AGU),
K. Yamaoka (Nagoya U), S. Nakahira (RIKEN), I. Takahashi (IPMU),
Y. Asaoka, S. Ozawa, S. Torii (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U),
W. Ishizaki (ICRR), S. Ricciarini (U of Florence),
A. V. Penacchioni, P. S. Marrocchesi (U of Siena)
and the CALET collaboration:
The extremely bright, long GRB 180720B (Swift-BAT trigger #848890:
Siegel et al., GCN Circ. 22973, Barthelmy et al. GCN Circ. 22998;
Fermi-LAT detection: Bissaldi and Racusin, GCN Circ. 22980;
Fermi-GBM observation: Roberts and Meegan, GCN Circ. 22981;
MAXI/GGS detection: Negoro et al., GCN Circ. 22993;
Konus-Wind observation: Frederiks et al., GCN Circ. 23011)
triggered the CALET Gamma-ray Burst Monitor (CGBM)
at 14:21:40.948 UTC on 20 July 2018. Because of a problem in
one of the ground alert processing script, the GCN notice was not
distributed automatically for this event. The burst signal was seen
by all CGBM detectors.
The CGBM data cover the time interval from T-243 sec to T+1449 sec
(when the HV was on and the source was in the CGBM FoV).
The burst light curve shows the main emission episode comprised
of several bright overlapped pulses which starts
at T-2.9 sec, peaks at 15.3 sec, and ends at T+54.0 sec,
followed by the weak tail seen at least up to T+120.1 sec.
The T90 and the T50 durations measured by the SGM data are
51.1 +- 3.0 sec and 15.4 +- 1.4 sec (40-1000 keV), respectively.
No any precursor is seen in the time interval from T-243 sec to T-2.9 sec.
The time-averaged spectrum of the main episode (measured by the SGM
from T+0.8 sec to T+52.8 sec) is best fit in the 30 keV - 20 MeV range
by a GRB (Band) model with alpha = -1.29 +- 0.04,
Epeak = 686(-77, +88) keV, and beta = -2.23(-0.12, +0.09)
(chi2 = 254.4/236 dof). The emission is seen up to ~20 MeV.
The resulting fluence in the 30 keV - 10 MeV range is
5.79(-0.19, +0.20)x10^-4 erg/cm2 .
Assuming a redshift of z=0.654 (Vreeswijk et al., GCN 22996)
and a FlatLambdaCDM cosmology with H0=68 km/s/Mpc and Omega_M=0.308
(Planck Collaboration 2016, A&A, 594, A13 (Paper XIII)),
the isotropic energy release, Eiso, is 6.82(-0.22, 0.24)x10^53 erg.
The quoted errors are at the 90% CL.
The ground processed light curve is available at
http://cgbm.calet.jp/cgbm_trigger/ground/1216131585/
All the quoted values are preliminary.
The CALET data used in this analysis are provided by the Waseda CALET
Operation Center located at the Waseda University.
GCN Circular 23073
Subject
GMRT radio detection of GRB 180720B
Date
2018-08-03T09:23:31Z (7 years ago)
From
Poonam Chandra at TIFR <poonam@ncra.tifr.res.in>
Poonam Chandra (NCRA-TIFR), A. J. Nayana (NCRA-TIFR), Dipankar Bhattacharya (IUCAA), S. Bradley Cenko (NASA) and Alessandra Corsi (Texas-Tech) report:
We observed GRB 180720B (Siegel et al. GCN 22973) with the Giant Metrewave Radio Telescope at the 1.4 GHz band on 2018 Jul 29.99 UT. We detect a radio afterglow with the flux density of ~370+/-59 uJy at the optical position (Martone et al. GCN 22976).
We thank the staff of the GMRT that made these observations possible. GMRT is run by the National Centre for Radio Astrophysics of the Tata Institute of Fundamental Research. More observations are planned.