GRB 210706A
GCN Circular 30431
Subject
GRB 210706A: Swift/XRT afterglow confirmation
Date
2021-07-09T13:23:26Z (5 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
A. Tohuvavohu (U. Toronto) and K.L. Page (U. Leicester) report on
behalf of the Swift-XRT team:
Swift-XRT has performed further follow-up observations of the
Fermi/GBM (E. Bissaldi et al. GCN 30405) and Swift/BAT-GUANO detected
burst GRB 210706A (Tohuvavohu et al., GCN Circ. 30393), collecting 9.5
ks
of Photon Counting (PC) mode data between T0+43 ks and T0+180 ks.
The uncatalogued X-ray source (src #2) detected in the first 2.8 ks of
data as the GRB afterglow candidate (Tohuvavohu et al. GCN 30399),
which was above existing upper limits at this location from previous
XRT observations, has faded significantly in the latest observation,
and is thus confirmed as the X-ray afterglow of the burst.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/xrt_curves/00021455/.
This circular is an official product of the Swift-XRT team.
GCN Circular 30405
Subject
GRB 210706A: Fermi GBM observation
Date
2021-07-07T14:13:18Z (5 years ago)
From
Elisabetta Bissaldi at INFN,Bari <elisabetta.bissaldi@ba.infn.it>
E. Bissaldi (Politecnico and INFN Bari) and C. Meegan (UAH)
report on behalf of the Fermi GBM Team:
"At 08:17:49.86 UT on 6 July 2021, the Fermi Gamma-Ray Burst Monitor (GBM)
triggered and located GRB 210706A (trigger 647252274 / 210706346),
which was also detected by the Swift/BAT-GUANO pipeline
(Tohuvavohu et al. 2021, GCN 30393).
The GBM on-ground location is consistent with the Swift position.
The angle from the Fermi LAT boresight
at the GBM trigger time is 86 degrees.
The GBM light curve consists of a single emission episode
with a duration (T90) of about 7 s (50-300 keV).
The time-averaged spectrum from T0-0.1 s to T0+5.1 s is
best fit by a power law function with an exponential
high-energy cutoff. The power law index is -1.35 +/- 0.04 and
the cutoff energy, parameterized as Epeak, is 590 +/- 130 keV.
The event fluence (10-1000 keV) in this time interval is
(6.0 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+1.5 s in the 10-1000 keV band
is 12.1 +/- 0.3 ph/s/cm^2.
The spectral analysis results presented above are preliminary;
final results will be published in the GBM GRB Catalog:
https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html
For Fermi GBM data and info, please visit the official Fermi GBM Support Page:
https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/"
GCN Circular 30404
Subject
GRB 210706A: optical upper limit of Sintesz-Newton/CrAO and AS-32/AbAO
Date
2021-07-07T13:44:19Z (5 years ago)
From
Alexei Pozanenko at IKI, Moscow <apozanen@iki.rssi.ru>
N. Pankov (IKI, HSE), S. Nazarov (CrAO), R. Ya. Inasaridze (AbAO), A.
Pozanenko (IKI), S. Belkin (IKI, HSE) report on behalf of IKI GRB FuN:
We observed the filed of Swift/BAT-GUANO detection GRB 210706A
(Tohuvavohu et al., GCN 30393), GRB 210706A also triggered Konus-Wind
(Ridnaia et al., GCN 30403) with Sintesz-Newton 350mm f/5 telescope of
CrAO observatory and AS-32 telescope of Abastumani observatory (AbAO).
Observation started on 2021-07-06 (UT) 22:52:40 and consist of 6 images
of 300 s exposure in Clear filter (Sintesz-Newton) and in R-filter (UT)
2021-07-06 (UT) 20:23:40 (AS-32). In bothe telescopes we cover the whole
localization region of Swift/BAT-GUANO (Tohuvavohu et al., GCN 30393).
We find no new optical sources in either of the two XRT candidates
(https://www.swift.ac.uk/ToO_GRBs/00021455/). In particular no source
was detected in XRT afterglow candidate #2 (Tohuvavohu et al., GCN 30399).
Upper limit for of the stacked image is following
Date UT start t-T0 Filter Exp. OT err UL(3) Telescope
(mid, days) (s)
2021-07-06 20:23:40 0.50719 R 9*60 n/d n/d 20.5 AS-32
2021-07-06 22:52:40 0.60755 Clear 6*300 n/d n/d 21.5 Newton
The photometry is based on nearby USNO-B1.0 (R2) stars.
Our non-detections is consistent with results of GROWTH-India Telescope
(Kumar et al., GCN 30402).
GCN Circular 30403
Subject
Konus-Wind detection of GRB 210706A
Date
2021-07-07T13:05:45Z (5 years ago)
From
Anna Ridnaia at Ioffe Institute <ridnaia@mail.ioffe.ru>
A. Ridnaia, D. Frederiks, S. Golenetskii, A. Lysenko,
D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline
on behalf of the Konus-Wind team, report:
The long-duration GRB 210706A
(Fermi GBM trigger 647252274;
Swift/BAT-GUANO detection: Tohuvavohu et al., GCN 30393)
triggered Konus-Wind at T0=29875.487 s UT (08:17:55.487).
The burst light curve shows a multipeaked structure
started at ~T0-2.7 s with a total duration of ~8.9 s.
The emission is seen up to ~4 MeV.
The Konus-Wind light curve of this GRB is available at
http://www.ioffe.ru/LEA/GRBs/GRB210706_T29875/
As observed by Konus-Wind, the burst
had a fluence of 5.39(-0.66,+0.90)x10^-6 erg/cm2,
and a 64-ms peak flux, measured from T0+1.040 s,
of 2.73(-0.92,+0.99)x10^-6 erg/cm2/s
(both in the 20 keV - 10 MeV energy range).
The time-averaged spectrum of the burst
(measured from T0 to T0+8.448 s)
is best fit in the 20 keV - 4 MeV range
by a power law with exponential cutoff model:
dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep)
with alpha = -1.11(-0.26,+0.30)
and Ep = 263(-59,+112) keV (chi2 = 65/71 dof).
Fitting by a GRB (Band) model yields the same alpha and Ep,
and an upper limit on the high energy photon index: beta < -2.3
(chi2 = 65/70 dof).
All the quoted errors are at the 90% confidence level.
All the quoted values are preliminary.
GCN Circular 30402
Subject
GRB 210706A: GIT optical upper limits
Date
2021-07-07T12:39:54Z (5 years ago)
From
Harsh Kumar at Indian Inst of Tech,Bombay <harshkosli13@gmail.com>
H. Kumar (IITB), R. Norbu (IAO), V. Bhalerao (IITB), G. C. Anupama (IIA),
S. Barway (IIA) report on behalf of the GIT team:
We observed GRB 210706A detected by Swift/BAT-GUANO (see A. Tohuvavohu et
al. GCN #30393) with 0.7m GROWTH-India Telescope (GIT). We obtained
multiple 100-second images in g', r' and i' bands, interspersed with each
other. The total exposure in each band was 1000 seconds. We did not detect
any new source in our stacked images within the 3.2 arcsec circle, around
the swift XRT position centered at RA: 20h 47m 58.73s Dec: +13d 19' 01.0"
(GCN #30399). Also, we did not detect any new transient within the full 5
arcmin circle around the Swift/BAT-GUANO position (GCN #30393). The
obtained upper limit follow as:
-------------------------------------------------------------------
JD (mid) | T_mid-T0(hrs) | Filter | Lim_mag (5-sigma) |
-------------------------------------------------------------------
2459402.343657 | 11.95 | g' | > 20.86 |
2459402.346588 | 12.02 | r' | > 21.00 |
2459402.349518 | 12.09 | i' | > 20.32 |
-------------------------------------------------------------------
The magnitudes are calibrated against PanSTARRS (Flewelling et al., 2018)
and not corrected for Galactic extinction.
The GROWTH India Telescope (GIT) is a 70-cm telescope with a 0.7-degree
field of view, set up by the Indian Institute of Astrophysics and the
Indian Institute of Technology Bombay with support from the Indo-US Science
and Technology Forum (IUSSTF) and the Science and Engineering Research
Board (SERB) of the Department of Science and Technology (DST), Government
of India (https://sites.google.com/view/growthindia/). It is located at the
Indian Astronomical Observatory (Hanle), operated by the Indian Institute
of Astrophysics (IIA).
GCN Circular 30399
Subject
GRB 210706A: Swift-XRT afterglow detection
Date
2021-07-07T01:18:21Z (5 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
A. Tohuvavohu (U. Toronto), B. Sbarufatti (PSU), D.N. Burrows (PSU),
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri
(INAF-OAB), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB) and P.A.
Evans (U. Leicester) report on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
Swift/BAT-GUANO-detected burst GRB 210706A (Tohuvavohu et al. GCN Circ.
30393), collecting 2.8 ks of Photon Counting (PC) mode data between
T0+43.3 ks and T0+50.7 ks.
Two uncatalogued X-ray sources are detected, of which one ("Source 2")
is believed to be the afterglow. Using 2536 s of PC mode data and 2
UVOT images, we find an enhanced XRT position (using the XRT-UVOT
alignment and matching UVOT field sources to the USNO-B1 catalogue):
RA, Dec = 311.99471, +13.31694 which is equivalent to:
RA (J2000): 20h 47m 58.73s
Dec(J2000): +13d 19' 01.0"
with an uncertainty of 3.2 arcsec (radius, 90% confidence). This
position is 69 arcsec from the Swift/BAT-GUANO position. The source
has a mean count rate of 1.4e-02 ct/sec; we cannot determine at the
present time whether it is fading.
The field has been previously observed by XRT for the Swift
Gravitational Wave Galaxy Survey (https://www.swift.ac.uk/SGWGS/, GCN
24305). No source was detected at this position on a 2.8 ks integrated
exposure, down to a 3-�� upper limit of 7 e-3 ct s^-1.
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00021455.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021455.
This circular is an official product of the Swift-XRT team.
GCN Circular 30397
Subject
GRB 210706A: Swift ToO observations
Date
2021-07-06T20:19:06Z (5 years ago)
From
Phil Evans at U of Leicester <pae9@leicester.ac.uk>
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the Swift/BAT-GUANO GRB 210706A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021455
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the Swift/BAT-GUANO event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
GCN Circular 30393
Subject
GRB 210706A: Swift/BAT-GUANO detection and arcminute localization
Date
2021-07-06T18:22:57Z (5 years ago)
From
Aaron Tohuvavohu at U Toronto <aaron.tohu@gmail.com>
Aaron Tohuvavohu (U Toronto), James DeLaunay (PSU), Jamie A. Kennea
(PSU), Gayathri Raman (PSU) report:
Swift/BAT did not trigger on GRB 210706A (T0: 2021-07-06 08:17:49.9
UTC, Fermi/GBM trigger # 647252274).
The Fermi/GBM notice, distributed in near real-time, triggered the
Swift Mission Operations Center operated Gamma-ray Urgent Archiver for
Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1).
Upon trigger by this notice, GUANO sent a command to the Swift Burst
Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from
[-50,+150] seconds around the time of the burst. All the requested
event mode data was delivered to the ground.
The burst is detected in BAT with a duration of approximately 10 seconds.
The burst occurred during a Swift slew.
Using the normal BAT imaging technique, we find the location for
the GRB with an SNR of 19.
The BAT position is
RA, Dec = 312.0124 +13.3079 deg which is
RA(J2000) = 20h 48m 02.98s
Dec(J2000) = +13d 18��� 28.4���
with an estimated uncertainty of 5 arcmin.
This position is consistent with the Ferm/GBM localization.
XRT and UVOT follow-up has been requested.
Results of follow-up observations will be reported in future circulars.
GUANO is a fully autonomous, extremely low latency, spacecraft
commanding pipeline designed for targeted recovery of BAT event mode
data around the times of compelling astrophysical events to enable
more sensitive GRB searches.
A live reporting of Swift/BAT event data recovered by GUANO can be
found at: https://www.swift.psu.edu/guano/