GRB 260706A — All Circulars

J. K. Leung (U. Toronto/HUJI), G. E. Anderson (CSIRO), S. Chastain (TTU), L. Rhodes (TSI/McGill), A. Gulati (U. Sydney), A. J. van der Horst (GWU) on behalf of the PanRadio GRB collaboration

We performed observations of GRB 260706A, which was detected by SVOM/ECLAIRs (Alaux et al., GCN 45089) and Fermi/GBM (Fermi GBM team, GCN 45088; Trigg et al., GCN 45093), using the Australia Telescope Compact Array (ATCA) from 14:30 - 23:00 UT on 11 July 2026 (~5.1 days post-burst) using the 4cm (4-12 GHz) receiver. Our observations were centred on the position of the uncatalogued X-ray source found in EP-FXT follow-up observations (Liang et al., GCN45097; Pillas et al., GCN 45114).

In our preliminary analysis, we detect a radio source at ~0.2 mJy at 8 GHz with a spectral index of ~1.5 indicating that the radio counterpart is likely to be self-absorbed at this epoch. We measured the position of the radio source to be:
RA (J2000)=2:15:15.4
DEC (J2000)=-49:09:02.7
with a positional uncertainty radius of ~0.5".

No previous radio source was detected at this position in the Rapid ASKAP Continuum Survey (RACS; McConnell et al., PASA, 37, e048). The radio source is ~2.7" away from the reported position of the EP-FXT uncatalogued X-ray source position (Liang et al., GCN45097), but is consistent within its ~10" positional uncertainty radius. It is the only radio source detected above the 5-sigma = 30 microJy/beam within the SVOM/ECLAIRs error circle (Alaux et al., GCN 45089). We therefore suggest this source is possibly the radio counterpart to GRB 260706A.

Further observations are planned.

We thank the CSIRO Space and Astronomy staff for supporting these observations. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility (https://ror.org/05qajvd42) which is funded by the Australian Government for operation as a National Facility managed by CSIRO.

K. Agabi (OCA), A. Simon (TShNU of Kyiv), L. Wyrzykowski (Uni. Warsaw/NCBJ), A. Guštin (UNG School of Science, GoChile), J. Hambsch (VVS, GEOS, BAV), S. Antier (IJCLAB), M. Pillas (IAP), L. Abe (OCA), T T. Guillot (OCA). X. Sheng (QUB), P. Gokuldass (ERAU), E. Elhosseiny (KAO),  O. Sokoliuk (UKyiv), Y. Rajabov (UBAI), Z. Maksut NU), E. Jehin (U of Liège), M. Ferrais (U of Liège), Nélio Sasaki (UEA-Parintins), Wagner Corradi (UFMG) on behalf of GRANDMA collaboration:

We observed the field of GRB 260706A detected by SVOM/ECLAIRs (GCN 45089), SVOM/GRM and Fermi-GBM (GCN 45088) and its counterpart detected by EP-FXT (GCN 45097, GCN 45114). The observations started at 20:30:00 UTC on the 6 of July 2026, 4.3 post ECLAIRs T0 with ASTEP and last about 1 day in all the network.

We didn't detect any optical counterpart at the EP location (and near by) with GRANDMA, using 0.4m GoT1 telescope of University of Nova Gorica hosted at El Sauce Observatory in Chile, 0.6m TRAPPIST-South, 14" telescope at Franz-Josef Hambsch's Remote Observatory Atacama Dessert (ROAD) in Chile, ASTEP-40cm at Concordia, OPD-60cm, 1m LCO-SAAO telescope in South Africa  with observatory in multiple epochs and filters. We reported our upper limit in the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GCN-260706_161221. To access, one simply needs to create an account using your ORCID id.

Our upper limit are coherent with REM (GCN 45100), LCO-1m (GCN 45098), and SVOM/VT (GCN 45113).

The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousins filters were calibrated using the Gaia DR3 Synphot catalog.

The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet@ijclab.in2p3.fr, skyportal.io). 

K. Agabi (OCA), A. Simon (TShNU of Kyiv), L. Wyrzykowski (Uni. Warsaw/NCBJ), A. Guštin (UNG School of Science, GoChile), J. Hambsch (VVS, GEOS, BAV), S. Antier (IJCLAB), M. Pillas (IAP), L. Abe (OCA), T T. Guillot (OCA). X. Sheng (QUB), P. Gokuldass (ERAU), E. Elhosseiny (KAO),  O. Sokoliuk (UKyiv), Y. Rajabov (UBAI), Z. Maksut NU), E. Jehin (U of Liège), M. Ferrais (U of Liège), Nélio Sasaki (UEA-Parintins), Wagner Corradi (UFMG) on behalf of GRANDMA collaboration:

We observed the field of GRB 260706A detected by SVOM/ECLAIRs (GCN 45089), SVOM/GRM and Fermi-GBM (GCN 45088) and its counterpart detected by EP-FXT (GCN 45097, GCN 45114). The observations started at 20:30:00 UTC on the 6 of July 2026, 4.3 post ECLAIRs T0 with ASTEP and last about 1 day in all the network.

We didn't detect any optical counterpart at the EP location (and near by) with GRANDMA, using 0.4m GoT1 telescope of University of Nova Gorica hosted at El Sauce Observatory in Chile, 0.6m TRAPPIST-South, 14" telescope at Franz-Josef Hambsch's Remote Observatory Atacama Dessert (ROAD) in Chile, ASTEP-40cm at Concordia, OPD-60cm, 1m LCO-SAAO telescope in South Africa  with observatory in multiple epochs and filters. We reported our upper limit in the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GCN-260706_161221. To access, one simply needs to create an account using your ORCID id.

Our upper limit are coherent with REM (GCN 45100), LCO-1m (GCN 45098), and SVOM/VT (GCN 45113).

The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousins filters were calibrated using the Gaia DR3 Synphot catalog.

The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK.

GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet@ijclab.in2p3.fr, skyportal.io). 

M. Pillas (IAP), F. Daigne (IAP), Y.F. Liang (PMO), report on behalf of the SVOM and EP collaborations:

EP-FXT performed an additional follow-up observation of GRB 260706A detected by SVOM/ECLAIRs (Alaux et al., GCN 45089) and Fermi/GBM (Fermi GBM Team, GCN 45088). This second follow-up observation epoch started on 2026-07-07 at 19:16:49 (UTC), about 27.1 hr after the SVOM trigger, with a total exposure time of 3 ks.

On-ground analysis of the FXT data still detected an uncatalogued source consistent with the previous EP/FXT detection (Liang et al., GCN 45097). The derived average unabsorbed flux is (2.5+/- 0.5) x 10^(-13) erg/s/cm^2 (0.5-10 keV; 1-sigma uncertainty).

Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).

H. L. Li, L. P. Xin, C. Wu, Y. L. Qiu, Y. N. Ma, J. R. Xu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan,  J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), F. Daigne (IAP) and M. Pillas (IAP) report on behalf of the SVOM/VT team.

SVOM/VT performed ToO observation to GRB 260706A detected by SVOM/Eclairs  (sb26070606, Alaux et al., GCN 45089; Guillot et al., GCN 45103). This burst was also detected by SVOM/GRM (Alaux et al., GCN 45089; Wang et al., GCN 45101) and Fermi/GBM (the Fermi GBM team, GCN 45088; Trigg et al., GCN 45093). The observation started at 2026-07-07T07:42:10 UTC, about 15.506 hours after trigger in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. 

No credible sources are detected in stacked images within error box of SVOM/Eclairs (Alaux et al., GCN 45089) and EP-FXT (Liang et al., GCN 45097) down to 10-sigma upper limits of 22.0 mag in both channels at the midtime of 17.43 hr post trigger.

The magnitudes are in the AB system and are not corrected for Galactic extinction.
Our non-detection is consistent with observations from LCO (Saccardi et al., GCN 45098) and REM (Brivio et al., GCN 45100).

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.

Authors: S. Guillot, M. Brunet, J. Alaux (IRAP), F. Daigne, M. Pillas (IAP), report on behalf of the SVOM/ECLAIRs team: 

Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260706A (SVOM Burst id sb26070606, GCN #45089) with trigger time T0 = 2026-07-06T16:12:23 UTC, which was also detected by Fermi/GBM (GCN #45088). 

The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve, and the burst duration is T90 = 23.41 +0.64/-0.89 s in the 4-120 keV energy band.

The time-averaged spectrum from T0 to T0+24 s in the 5-120 keV energy range is best fitted by a cut-off powerlaw model with alpha = -1.4 +/- 0.1 and Epeak = 38.1 +/- 6.4 keV.  With this model, the 4-120 keV fluence is (3.5 +/- 0.3)e-6 erg/cm^2 and the 4-120 keV photon flux is 5.9 +/- 0.3 ph/cm^2/s. 

All the quoted errors are at the 68% confidence level.
The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC.

The SVOM/ECLAIRs point of contact for this burst is: Sebastien Guillot (IRAP) (sebastien.guillot at utoulouse.fr)

SVOM/GRM team: Yue Wang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)

SVOM/ECLAIRs team: Sebastien Guillot (IRAP)

Report on behalf of the SVOM team:

SVOM/GRM was triggered in-flight by GRB 260706A at 2026-07-06T16:12:22.000 (T0), which is also detected by SVOM/ECLAIRs (J. Alaux et. al., GCN #45089) and Fermi/GBM (Fermi GBM team, GCN #45088, #45093).

With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple peaks with a T90 of 31 +12/-8 s in the 15-5000 keV band.

The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb260706A.png

In addition, the position of this burst, as determined by SVOM/ECLAIRs (RA = 33.8323 deg, Dec = -49.1375 deg, Error = 3.17 arcmin, GCN #45089), is used for the spectral analysis. With this localization, the time-averaged spectrum from T0-3.0 to T0+30.0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.47 +0.16/-0.15 and the cutoff energy, parameterized as Epeak, is 53.98 +5.09/-4.96 keV. The event fluence (10-1000 keV) in this time interval is (3.96 +0.21/-0.19)E-06 erg/cm^2.

The localization of GRB 260706A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260706A_amati.png
The localization of GRB 260706A in the 'Yonetoku' relation diagram is shown at:
https://www.bursthub.cn//admin/static/svgrb260706A_yonetoku.png

The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.

The SVOM/GRM point of contact for this burst is: Yue Wang (IHEP) (yuewang@ihep.ac.cn)

R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:

We observed the field of GRB 260706A, detected by SVOM/ECLAIRs (Alaux et al., GCN 45089) and Fermi/GBM (Trigg et al., GCN 45093) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile).                 
The observations were carried out in the g,r,i,z, and K bands, started on 2026-07-07 at 04:49:10 UT (i.e. 12.6 hr after the burst) and lasted for about 1 hr.

From preliminary photometry, we do not detect any uncatalogued source within the EP/FXT error box (Liang et al., GCN 45097) down to the following 3sigma limits:
r > 19.4 (AB; calibrated against the SkyMapper catalogue),
 at a mid-time of 13.5 hr after the trigger;

K > 13.6 (Vega; calibrated against the 2MASS catalogue),
 at a mid-time of 13.3 hr after the trigger.

A. Saccardi (CEA/Irfu), D. Turpin (CEA/Irfu), F. Daigne, M. Pillas (IAP), report on behalf of the SVOM mission team:

We observed the field of GRB 260706A detected by SVOM/ECLAIRs (Alaux et al., GCN 45089) and Fermi/GBM (Fermi GBM team, GCN 45088; Trigg et al., GCN 45093), with the LCO 1m telescope at Cerro Tololo Observatory equipped with the Sinistro instrument.

Our observation started on 2026-07-07 at 08:15:35 UT (about 16 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r filter.

In the stacked image, we do not detect any new source within the EP/FXT error box (Liang et al., GCN 45097). We measure the following upper limit calibrated against the SkyMapper DR4 catalog, and not corrected for Galactic extinction:

r > 22.3 AB (3-sigma, mid-time 16.14 hr after the trigger).

This project is funded by the SVOM collaboration.

Y.F. Liang, H. Zhou (PMO), K. R. Ni (CCNU), C.-K. Kan (HKU), H. Sun (NAOC) on behalf of the Einstein Probe (EP) team:

EP-FXT performed an automatically follow-up observation of GRB 260706A detected by SVOM/ECLAIRs (Alaux et al., GCN 45089), which also triggered Fermi-GBM (Fermi GBM team, GCN 45088; Trigg et al., GCN 45093). The follow-up observation started at 2026-07-06 17:44:38 (UTC), about 1.5 hr after the SVOM trigger, with a total exposure time of around 5462 ks.

On-ground analysis of the FXT data found an uncatalogued source within the ECLAIRs error circle at R.A., Dec. =33.8136, -49.1514 deg (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic). The derived average unabsorbed flux is 6.21 (-0.87/+1.03) x 10^(-12) erg/s/cm^2 (0.5-10 keV; 1-sigma uncertainty).

Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics).

A. C. Trigg (NPP ORAU, NASA MSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:

"At 16:12:21.43 UT on 06 July 2026, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 260706A (trigger 805047146/260706675),
which was also detected by SVOM/ECLAIRs (J. Alaux et al. 20026, GCN 45089).
The Fermi GBM on-ground location is consistent with the SVOM/ELCAIRs position.

The angle from the Fermi LAT boresight is 43 degrees.

The GBM light curve displays two peaks with a duration (T90)
of about 17 s (50-300 keV). The time-averaged spectrum
from T0+0.001 to T0+30.616 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.13 +/- 0.01 and the cutoff energy,
parameterized as Epeak, is 47.1 +/- 0.6 keV.

The event fluence (10-1000 keV) in this time interval is
(3.18 +/- 0.08)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+15 s in the 10-1000 keV band is 5.3 +/- 0.3 ph/s/cm^2.

A Band function fits the spectrum equally well
with Epeak= 39.1 +/- 0.5 keV, alpha = -0.71 +/- 0.01 and beta = -2.63 +/- 0.03.

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/"

J. Alaux, M. Brunet, S. Guillot, M. Boiziot (IRAP), F. Daigne, M. Pillas (IAP) report on behalf of the SVOM mission team:

At 2026-07-06T16:12:23 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260706A (SVOM burst-id sb26070606), which is also detected by Fermi/GBM (GCN 45088).

The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.

The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 19 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 31.31 in the [8-120] keV energy band over a time window of 20.48 seconds starting at 2026-07-06T16:12:20.

The localization of the best alert is R.A., Dec. 33.8323, -49.1375 degrees:
R.A. (J2000) = 2h15m19.75s
Dec. (J2000) = -49d08m15.14s
with a 90% confidence level (C.L.) radius of 3.17 arcmin (including systematic error of 2 arcmin added in quadrature).

The SVOM/ECLAIRs light curve showed a multiple peak structure. 

This burst also triggered SVOM/GRM at 2026-07-06T16:12:21 on a timescale of 1 second with an SNR of 9.50. The SVOM/GRM light curve showed a multiple peak structure with a T90 duration of about 
22.9 -3.8/+10.5 seconds.

SVOM slewed to the burst.

No X-ray observation could be performed by SVOM/MXT for the time being. 
No optical observation could be performed by SVOM/VT for the time being.

The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.

The Burst Advocate (BA) on shift for this alert is Frédéric Daigne: daigne@iap.fr.
Please contact the BA by email if you require additional information.

The Fermi GBM team reports the detection of a likely LONG GRB

At 16:12:21 UT on 6 Jul 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260706A (trigger 805047146.426808 / 260706675).

The on-ground calculated location, using the Fermi GBM trigger data, is RA = 17.5, Dec = -40.6 (J2000 degrees, equivalent to J2000 01h 10m, -40d 36'), with a statistical uncertainty of 5.4 degrees.

The angle from the Fermi LAT boresight is 57.0 degrees.

The skymap can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260706675/quicklook/glg_skymap_all_bn260706675.png

The HEALPix FITS file, including the estimated localization systematic, can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260706675/quicklook/glg_healpix_all_bn260706675.fit

The GBM light curve can be found here:
https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260706675/quicklook/glg_lc_medres34_bn260706675.gif