GRB 251203B
GCN Circular 42983
Subject
GRB 251203B: Swift-XRT observations
Date
2025-12-03T22:35:55Z (2 days ago)
From
Phil Evans at U of Leicester <pae9@star.le.ac.uk>
Via
email
S. Lanava (PSU), P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi
(INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio
(INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A.
D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara
(PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T.
Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf
of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source
sb25120304, collecting 972 s of Photon Counting (PC) mode data between T0+4.6 ks and
T0+5.7 ks after the trigger. A candidate counterpart has been found. The details of
this source are:
Source 1 (SWIFT J011326.9+000111):
==================================
RA (J2000.0): 18.3625 = 01 13 27.00
Dec (J2000.0): +0.0198 = +00 01 11.3
Error: 3.5 (arcsec, radius, 90% confidence).
Detect flag: GOOD
Distance: 5.9 arcmin from the SVOM/ECLAIRs position.
Mean rate: 1.785 +/- 0.088 ct s^-1
Mean flux: (5.76 +/- 0.28)e-11 erg cm^-2 s^-1
Peak rate: 2.72 +/- 0.62 ct s^-1
Peak flux: (8.8 +/- 2.0)e-11 erg cm^-2 s^-1
ECF: 3.23e-11 erg cm^-2 ct^-1
assuming NH=1.00e+21 cm^-2, gamma=2.03
determined from a spectral fit.
This matches a catalogued X-ray source 4XMM J011326.8+000107
in the XMM-NEWTON/XMMSSC catalogue. Details:
Separation: 3.3" from the XRT source
Cat Rate: 2.7e-01 +/- 1.0e-02 ct s^-1
Cat Flux: 2.4e-12 +/- 8.9e-14 erg cm^-2 s^-1 (0.3-10 keV)
so the source is 4.3-sigma above the catalogued flux.
The source may be fading, at the 0.3-sigma level.
A SIMBAD object `Gaia DR3 2534635509050352256' is 4.2" away.
There is 1 2MASS object within the source's 3-sigma error radius.
As pointed out by Malesani et al. (GCNs 42979), Brunet et al. (GCN 42981) and
Perez-Garcia at al. (GCN 42982) this suggest that the transient is due to flaring
activity from this star.
We have detected a total of 4 sources. These have been automatically classified as
follows:
* 0 likely counterparts
* 1 candidate counterpart
* 3 uncatalogued X-ray sources
* 0 known X-ray sources
Uncatalogued X-ray sources
--------------------------
Source 2 (SWIFT J011329.9-000900):
==================================
RA (J2000.0): 18.3746 = 01 13 29.90
Dec (J2000.0): -0.1502 = -00 09 00.7
Error: 7.9 (arcsec, radius, 90% confidence).
Detect flag: POOR
Distance: 10.3 arcmin from the SVOM/ECLAIRs position.
Mean rate: (6.9 [+4.4, -3.1])e-3 ct s^-1
Mean flux: (3.0 [+1.9, -1.3])e-13 erg cm^-2 s^-1
Peak rate: (6.9 [+4.4, -3.1])e-3 ct s^-1
Peak flux: (3.0 [+1.9, -1.3])e-13 erg cm^-2 s^-1
XMM UL: 1.8e-14 erg cm^-2 s^-1, (0.3-10 keV)
so the source is not above this 3-sigma upper limit.
There is no evidence for fading.
Source 3 (SWIFT J011422.6+000036):
==================================
RA (J2000.0): 18.5945 = 01 14 22.68
Dec (J2000.0): +0.0102 = +00 00 36.7
Error: 8.3 (arcsec, radius, 90% confidence).
Detect flag: POOR
Distance: 8.1 arcmin from the SVOM/ECLAIRs position.
Mean rate: (6.2 [+4.0, -2.8])e-3 ct s^-1
Mean flux: (2.6 [+1.7, -1.2])e-13 erg cm^-2 s^-1
Peak rate: (6.2 [+4.0, -2.8])e-3 ct s^-1
Peak flux: (2.6 [+1.7, -1.2])e-13 erg cm^-2 s^-1
XMM UL: 1.1e-14 erg cm^-2 s^-1, (0.3-10 keV)
so the source is not above this 3-sigma upper limit.
There is no evidence for fading.
Source 4 (SWIFT J011327.9-000300):
==================================
RA (J2000.0): 18.3663 = 01 13 27.91
Dec (J2000.0): -0.0501 = -00 03 00.4
Error: 9.4 (arcsec, radius, 90% confidence).
Detect flag: POOR
Distance: 6.4 arcmin from the SVOM/ECLAIRs position.
Mean rate: (-1.0 +/- -1.0)e0 ct s^-1
Mean flux: (-4.3 +/- -4.3)e-11 erg cm^-2 s^-1
Peak rate: (4.0 [+3.3, -2.3])e-3 ct s^-1
Peak flux: (1.7 [+1.4, -1.0])e-13 erg cm^-2 s^-1
XMM UL: 3.6e-14 erg cm^-2 s^-1, (0.3-10 keV)
so the source is not above this 3-sigma upper limit.
There is no evidence for fading.
There is 1 2MASS object within the source's 3-sigma error radius.
All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with
catalogues and upper limits from other missions, we assumed a power-law spectrum
with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated.
The results of the XRT-team automatic analysis of the XRT observations, including a
position-specific upper limit calculator, are available at
https://www.swift.ac.uk/SVOM/SVOM_FIELD00054.
This circular is an official product of the Swift-XRT team.
GCN Circular 42982
Subject
GRB 251203B: confirmation of a stellar flare by BOOTES-2
Date
2025-12-03T21:59:40Z (2 days ago)
From
I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg@iaa.es>
Via
Web form
I. Perez-Garcia, M.D. Caballero-Garcia, E. J. Fernandez-Garcia, R. Sanchez-Ramirez, S.-Y. Wu, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC, Granada), Y.-D. Hu (GXU), C. Perez del Pulgar and A. Reina (Univ. of Malaga), M. Gritsevich (Univ. of Helsinki), R. Fernandez-Munoz (IHSM/UMA-CSIC), D. R. Xiong (Yunnan Observatories of CAS), and M. Jelinek (ASU-CAS, Ondrejov Obs.), on behalf of a larger collaboration, report:
Following the detection of trigger sb25120304 by SVOM (Brunet et al. GCN 42973), the 0.6m robotic telescope BOOTES-2/TELMA at IHSM La Mayora/UMA-CSIC (Malaga, Spain) responded to the alert on Dec 3, 18:16 UT (i.e. 7 min after detection). A serie of 3 sec images in clear fiter were taken. As reported by Palmerio et al. (GCN 42978) and Malesani et al. (GCN 42979) we measure the star Gaia DR3 2534635509050352256 to fade by ~1.8 mag over a ~20 min interval, consistent with a stellar flare and confirming its non-GRB origin, as stated in Brunet et al. (GCN 42981).
We thank the staff at IHSM La Mayora/UMA-CSIC for their excellent support.
GCN Circular 42981
Subject
GRB 251203B : SVOM trigger sb25120304 is not a GRB
Date
2025-12-03T21:50:09Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet, N. A. Webb (IRAP), D. B. Malesani (DAWN/NBI and Radboud),report on behalf of the SVOM mission team:
At 2025-12-03T18:10:27 SVOM issued an alert with burst-id: sb25120304.
The following circulars have been published regarding this event: GCN 42973, GCN 42974, GCN 42978, GCN 42979, with the event labelled as GRB 252103B.
Given the VT (Palmerio et al., GCN 42978), LCO (Malesani et al., GCN 42979), and XRT observations (https://www.swift.ac.uk/SVOM/SVOM_FIELD00054/), this event is most likely associated with a flare from the star Gaia DR3 2534635509050352256 (also a historical X-ray emitter), and is no longer considered a GRB.
We apologize for any inconvenience this may have caused.
The Burst Advocate (BA) on shift for this alert is Marius Brunet: mbrunet@irap.omp.eu.
Please contact the BA by email if you require additional information.
GCN Circular 42979
Subject
GRB 251203B: LCO optical upper limits
Date
2025-12-03T21:22:36Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
D. B. Malesani (DAWN/NBI and Radboud), D. Turpin, A. Saccardi, J. T. Palmerio (CEA/Irfu), L. P. Xin, C. Wu (NAOC), B. Cordier (CEA/Irfu), M. Brunet, N. A. Webb (IRAP), report on behalf of the SVOM mission team:
We observed the field of the SVOM GRB 251203B (Brunet et al., GCN 42973) with the LCO 1m telescope at South African Astronomical Observatory equipped with the Sinistro instrument.
Our observation started on 2025-12-03 at 19:14:38 UT (about 64 min after the trigger) and we obtained 3x200 s exposures in the SDSS r and 3x200 s exposures in the PanSTARRS z filters. In the stacked image, we do not detect any new source within the MXT error circle.
We measure the following upper limits calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction:
r > 20.8 AB (mid-time 1.16 hr after the trigger);
z > 20.1 AB (mid-time 1.29 hr after the trigger).
As already noted by Brunet et al. (GCN 42973) and Palmerio et al. (GCN 42978), within the MXT error circle there is a bright star at RA = 01:13:26.89, Dec = +00:01:07.7, also a possible historical X-ray emitter. Recent Swift/XRT observations (https://www.swift.ac.uk/SVOM/SVOM_FIELD00054/) show this star to be coincident with the only X-ray source within the MXT error circle. This suggests the transient is due to activity from this star.
In our z-band image, the star appears about 0.6 mag brighter than its archival Pan-STARRS magnitude (though we caution possible saturation effects), a behavior also consistent with a stellar flare origin of the burst.
This project is funded by the SVOM collaboration.
GCN Circular 42978
Subject
GRB 251203B: SVOM/VT optical observation
Date
2025-12-03T20:48:28Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
J. T. Palmerio (CEA), D. B. Malesani (DAWN/NBI and Radboud), Y. L. Qiu, C. Wu, H. L. Li, L. P. Xin (NAOC) on behalf of the SVOM/VT team.
After the trigger by SVOM/ECLAIRs at 2025-12-03T18:10:27 UTC (T0), SVOM performed an automatic slew on the burst location (Brunet et al., GCN 42973). SVOM/VT began observing the field at 2025-12-03T18:16:09, 341.62 seconds after T0, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, no credible candidate is identified down to VT_R~21 mag within the error box provided by MXT (Brunet et al. GCN 42973).
We note the presence of the bright star Gaia DR3 2534635509050352256 within the error box of MXT which appeared to fade in our observations from magnitude VT_B = 12.4 to 14.0 over the course of ~1 hr. Despite the difference in photometric filters, this is brighter than its catalogued magnitude of mag g = 15.2 in Pan-STARRS1.
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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS.
GCN Circular 42974
Subject
SVOM GRB251203B: Global MASTER-Net observations report
Date
2025-12-03T18:56:30Z (2 days ago)
Edited On
2025-12-04T15:25:18Z (20 hours ago)
From
Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov@xray.sai.msu.ru>
Edited By
Judith Racusin at NASA/GSFC <judith.racusin@nasa.gov> on behalf of Vladimir Lipunov at Lomonosov Moscow State University <lipunov@sai.msu.ru>
Via
email
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),
C.Francile, 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the SVOM GRB251203.76 (trigger No 1764785366,01h 13m 50.30s , -00d 00m 00.4s, R=0.1345) errorbox 927 sec after notice time and 1072 sec after trigger time at 2025-12-03 18:27:18 UT, with upper limit up to 14.1 mag. The observations began at zenith distance = 44 deg. The sun altitude is -52.1 deg.
The galactic latitude b = -62 deg., longitude l = 136 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=3059683
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
1103 | 2025-12-03 18:27:18 | MASTER-Kislovodsk | (01h 13m 06.79s , +00d 09m 15.4s) | C | 60 | 14.1 |
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
GCN Circular 42973
Subject
GRB 251203B: SVOM detection of a burst
Date
2025-12-03T18:54:01Z (2 days ago)
From
SVOM_group <svomgroup@bao.ac.cn>
Via
Web form
M. Brunet, N. A. Webb (IRAP), N. Dagoneau, M. Moita (CEA), report on behalf of the SVOM mission team
At 2025-12-03T18:10:27 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 251203B (SVOM burst-id sb25120304).
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 9 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 9.85 in the [5-20] keV energy band over a time window of 81.92 seconds starting at 2025-12-03T18:09:25.
The localization of the best alert is R.A., Dec. 18.4596, -0.0001 degrees (J2000) with a 90% confidence level (C.L.) radius of 8.07 arcmin (including systematic error of 2 arcmin added in quadrature).
SVOM slewed to the burst.
SVOM/MXT began observing the field at 2025-12-03T18:18:55 UTC, 509 seconds after T0. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 18.3720, 0.0157 degrees:
R.A. (J2000) = 01h13m29.27s
Dec. (J2000) = 00d00m56.42s
with a 90% C.L. radius of 35.36 arcseconds.
This location is 5.34 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.
We note the presence of an X-ray source (2E 0110.9-0014) located 20.06 arcsec away from the MXT position.
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 Marius Brunet: mbrunet@irap.omp.eu.
Please contact the BA by email if you require additional information.