sb26071506

H. L. Li, Y. N. Ma, C. Wu, Y. L. Qiu, L. P. Xin, 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) and J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team.

SVOM/VT performed observations with automatic slew to the field of X-ray transient sb26071506 triggered by SVOM/ECLAIRs (Cangemi et al., GCN 45169
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 ). The observations started at 2026-07-15T16:28:06 UTC, i.e., 327 sec post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.

The high-proper motion star V* AT Mic located within the errorbox of and MXT and ECLAIRs (Cangemi et al., GCN 45169
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 ) was saturated in both channels of VT. We performed photometry using the method described in Li et al. (2026, arXiv:2604.24266
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 ). Its brightness decreased in both channels, especially in VT_B band decayed from ~10.9 mag to ~11.2 mag in about 1.4 hours. This fading confirms this ECLAIRs trigger is related to the stellar flare.

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.

V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, 
G.Antipov,  A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU),
O.Gress, N.Budnev (ISU),
M. Segura,  F. Podesta, R.Podesta, E. Gonzalez  (Observatorio Astronomico Felix Aguilar (OAFA),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A.Sosnovskij (CrAO),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
D.Buckley (SAAO),
R.Rebolo (The Instituto de Astrofisica de Canarias),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,
A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) 

MASTER-SAAO robotic telescope  [1]  located in South Africa (South African Astronomical Observatory) was pointed to the SVOM sb26071506 ( SVOM_group <svomgroup@bao.ac.cn> et al., GCN 45169
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 ) errorbox  273 sec after notice time and 2918 sec after trigger time at 2026-07-15 17:11:42 UT, with upper limit up to  18.1 mag. The observations began at zenith distance = 79 deg. The sun  altitude  is -17.5 deg. 

The galactic latitude b = -37 deg., longitude l = 12 deg.


Real time updated cover map and OT discovered available here: 
https://master.sai.msu.ru/site/master2/observ.php?id=3429400

We obtain a following upper limits.  

Tmid-T0  |      Date Time      |          Site       |             Coord (J2000)          |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________

    2949 | 2026-07-15 17:11:42 |         MASTER-SAAO | (20h 39m 45.29s , -32d 45m 32.6s) |   C |    60 | 14.7 |        
    5590 | 2026-07-15 17:55:44 |         MASTER-SAAO | (20h 39m 44.61s , -32d 46m 54.4s) |   C |    60 | 18.1 |        
Filter C is a clear (unfiltred) band. 


The observation and reduction will continue. 
The message may be cited.

[1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023,  Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp.
http : // www.pereplet.ru/lipunov/625.html

Floriane Cangemi (APC), Alexis Coleiro (APC), Maria Grazia Bernardini (INAF-OAB, LUPM), Frederic Piron (LUPM), Nicolas Dagoneau (CEA), Andrea Saccardi (CEA) and Damien Turpin (CEA) report on behalf of the SVOM mission team:

At 2026-07-15T16:23:04 UTC (T0), SVOM/ECLAIRs triggered and located a X-ray transient (SVOM burst-id sb26071506).

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 4 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.24 in the [5-20] keV energy band over a time window of 327.68 seconds starting at 2026-07-15T16:18:58.

The localization of the best alert is R.A., Dec. 310.3570, -32.4133 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.57 arcmin (including systematic error of 2 arcmin added in quadrature).

SVOM slewed to the burst.

SVOM/MXT began observing the field at 2026-07-15T16:27:08 UTC, 244 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 310.4508, -32.4345 degrees:
R.A. (J2000) = 20h41m48.18s
Dec. (J2000) = -32d26m04.34s
with a 90% C.L. radius of 29.15 arcseconds.

This location is 4.92 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.

We note the presence of the high-proper motion star V* AT Mic in the error box of both ECLAIRs and MXT.

VT began observing the field after the slew. The analysis of the data will be published in a future circular.

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 Floriane Cangemi: cangemi@apc.in2p3.fr.
Please contact the BA by email if you require additional information.