sb26083106, GRB 260831B
GCN Circular 45490
Subject
GRB 260831B / sb26083106: SVOM/GWAC-F60A/B confirmation of optical variation of nova V* GK Per
Date
2026-09-01T15:29:59Z (a month ago)
Edited On
2026-09-01T16:09:58Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
S.J. Yin ,Y.X. Guan (GXU), C. Wu, L.P. Xin, X.H. Han, P.P. Zhang, J.L. Wang (NAOC), report on behalf of the SVOM follow-up team: We observed the field of sb26083106 triggered by SVOM (Godet et al., GCN 45477) with the GWAC-F60A/B at Xinglong Observatory, China.
We started observing at 2026-08-31T18:37:43.39 UTC with a set of 50 images in R-band, 1.5 min after the trigger. We do not detect credible uncataloged candidates within ECLAIRs' error box, which is consistent with the reports from LCO (Guan et al., GCN 45482) and SVOM/VT (Li et al., GCN 45489).
The following upper limit magnitude are derived R>18.6 mag (5-sigma at mid-time of 6.3 minutes after trigger), calibrated against USNO-B1.0 catalog, and not corrected for Galactic extinction.
We also measure the classical nova V* GK Per ,which shows an amplitude variation consistent with that reported by SVOM/VT (Li et al., GCN 45489).
Two 60-cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 19*19 arcmin.
GCN Circular 45489
Subject
GRB 260831B / sb26083106: SVOM/VT optical variability of V* GK Per
Date
2026-09-01T14:33:23Z (a month ago)
From
Huali Li at at NAOC, SVOM <lhl@nao.cas.cn>
Via
Web form
H. L. Li, L. P. Xin, C. Wu, Y. N. Ma, Y. L. Qiu, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) and C. Guepin (LUPM) report on behalf of the SVOM/VT team.
SVOM/VT performed observations with automatic slew of the SVOM/ECLAIRs trigger sb26083106 (Godet et al., GCN 45477, 45486) starting from 2026-08-31T18:46:36 UT, about 10 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
The classical nova mentioned by Godet et al. (GCN 45486) during our observations showed a fluctuating variation with the amplitude of about 0.2 mag in both channels.
We also searched for uncatalogued sources within the SVOM/ECLAIRs error box (Godet et al., GCN 45477). In our images no uncatalogued sources were detected down to 5-sigma upper limits of about 22.5 mag (AB) in both channels at the mid time of 18.3 minutes post trigger.
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.
GCN Circular 45486
Subject
SVOM trigger sb26083106 is not a GRB
Date
2026-09-01T13:07:45Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
O. Godet (IRAP), C. Guepin (LUPM), S. Guillot (IRAP)
report on behalf of the SVOM mission team:
At 2026-08-31T18:36:12 UT SVOM issued an alert with burst-id sb26083106, which was reported in the circular GCN #45477.
Using the event-by-event data downloaded through the X-band ground station, we determined a refined position for this event, concluding that it originated from the classical nova V* GK Per.
We apologize for any inconvenience this may have caused.
The Burst Advocate (BA) on shift for this alert is Claire Guepin: claire.guepin@lupm.in2p3.fr.
Please contact the BA by email if you require additional information.
GCN Circular 45484
Subject
GRB 260831B: EP-FXT follow-up observation
Date
2026-09-01T08:56:27Z (a month ago)
From
EP Team at NAOC/CAS <ep_ta@bao.ac.cn>
Via
Web form
Y. F. Liang, J. Y. Liu(PMO), X. Mao, Q. H. Lao, Z. X. Ling (NAO,CAS) on behalf of the Einstein Probe (EP) team:
EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 260831B (SVOM/sb26083106) (Godet et al. GCN 45477; Guan et al. GCN 45482) at 2026-08-31T21:31:08 (UTC), about 3 hours after the SVOM/ECLAIRs trigger, with an exposure time of 3002s. There is no uncataloged source within ECLAIRs' error box. The upper limit of this observation is about 2 x 10^(-13) erg/s/cm^2.
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).
GCN Circular 45482
Subject
GRB 260831B: LCO optical upper limits
Date
2026-09-01T06:56:51Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
Y.X. Guan (GXU), A. Saccardi, D. Turpin (CEA/Irfu), C. Wu, L.P. Xin (NAOC), C.Guepin (LUPM), C. Plasse (HKU) report on behalf of the SVOM mission team:
We observed the field of GRB 260831B (SVOM burst-id sb26083106 detected by SVOM (Godet et al., GCN 45477) with the LCO 1m telescope at Tenerife equipped with the Sinistro instrument.
Our observation started on 2026-09-01 at 01:31:26 UT (about 6.92 hr after the trigger) and we obtained 3x200 s exposures in the SDSS r and 3x200 s exposures in the Pan-STARRS z filters.
In the stacked image, we do not detect any new source within the SVOM/ECLAIRs error box. We measure the following upper limit calibrated against the Pan-STARRS DR1 catalog, and not corrected for Galactic extinction:
r > 21.5 AB (5-sigma, mid-time 7.22 hr after the trigger);
z > 20.2 AB (5-sigma, mid-time 7.01 hr after the trigger).
This project is funded by the SVOM collaboration.
GCN Circular 45477
Subject
GRB 260831B: SVOM detection of a possible burst
Date
2026-08-31T19:20:03Z (a month ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
O. Godet (IRAP), C. Guepin (LUPM), S. Guillot (IRAP) report on behalf of the SVOM mission team:
At 2026-08-31T18:36:12 UTC (T0), SVOM/ECLAIRs triggered and located the possible gamma-ray burst GRB 260831B (SVOM burst-id sb26083106).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was only detected by the Image Trigger (IMT), which produced a sequence of 5 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.11 in the [8-50] keV energy band over a time window of 655.36 seconds starting at 2026-08-31T18:32:07.
The localization of the best alert is R.A., Dec. 52.977, 43.971 degrees:
R.A. (J2000) = 3h31m54.41s
Dec. (J2000) = 43d58m15.22s
with a 90% confidence level (C.L.) radius of 8.69 arcmin (including systematic error of 2 arcmin added in quadrature).
The SVOM/ECLAIRs light curve is featureless.
SVOM slewed to the burst.
SVOM/MXT began observing the field about 10 minutes after T0. Using onboard processed data, no source was detected during a > 10 min exposure.
The SVOM/MXT team is waiting for the full dataset to detect and localise the possible SVOM/MXT counterpart.
VT began observing the field after the slew. The analysis of the data will be published in a future circular.
We note that the classical nova V* GK Per that triggered ECLAIRs in the past few weeks is within the ECLAIRs error circle.
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 Claire Guepin: claire.guepin at lupm.in2p3.fr
Please contact the BA by email if you require additional information.