Gamma-ray Burst 210706A

(All information courtesy of the instrument teams.)

Previous IAU Circulars

none

Results of Observations

GCN NOTICE

TITLE:           GCN/FERMI NOTICE
NOTICE_DATE:     Tue 06 Jul 21 12:51:50 UT
NOTICE_TYPE:     Fermi-GBM Final Position
RECORD_NUM:      0
TRIGGER_NUM:     647252274
GRB_RA:          313.960d {+20h 55m 50s} (J2000),
                 314.217d {+20h 56m 52s} (current),
                 313.363d {+20h 53m 27s} (1950)
GRB_DEC:         +12.360d {+12d 21' 36"} (J2000),
                 +12.443d {+12d 26' 36"} (current),
                 +12.168d {+12d 10' 04"} (1950)
GRB_ERROR:       3.23 [deg radius, statistical only]
GRB_DATE:        19401 TJD;   187 DOY;   21/07/06
GRB_TIME:        29869.86 SOD {08:17:49.86} UT
GRB_PHI:         146.11 [deg]
GRB_THETA:        85.07 [deg]
E_RANGE:         50.000 - 300.000 [keV]
LOC_ALGORITHM:   415 (Gnd S/W Version number)
SUN_POSTN:       105.93d {+07h 03m 44s}  +22.63d {+22d 37' 39"}
SUN_DIST:        135.30 [deg]   Sun_angle= 10.1 [hr] (West of Sun)
MOON_POSTN:       63.85d {+04h 15m 25s}  +20.74d {+20d 44' 17"}
MOON_DIST:       103.33 [deg]
MOON_ILLUM:      11 [%]
GAL_COORDS:       59.63,-20.58 [deg] galactic lon,lat of the burst (or transient)
ECL_COORDS:      320.45, 28.43 [deg] ecliptic lon,lat of the burst (or transient)
LC_URL:          http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210706346/quicklook/glg_lc_medres34_bn210706346.gif
LOC_URL:         http://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2021/bn210706346/quicklook/glg_locplot_all_bn210706346.png
COMMENTS:        Fermi-GBM Final Position.  
COMMENTS:        This Notice was ground-generated -- not flight-generated.  
COMMENTS:        The LC_URL file should be available by the time this FINAL notice is produced.  
COMMENTS:        This notice has human-in-the-loop processing.

GCN Circular #30393
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/
GCN Circular #30397
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 #30399
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-σ 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 #30402
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 #30403
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 #30404
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 #30405
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 #30431
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.

Back to JG's homepage

Jochen Greiner, last update: 09-Jul-2021 [Disclaimer]