TITLE: GCN CIRCULAR
NUMBER: 40712
SUBJECT: sb25061218: SVOM detection of a X-ray transient
DATE: 25/06/12 21:40:47 GMT
FROM: SVOM_group <svomgroup(a)bao.ac.cn>
J. Rodriguez, T. Sadibekova, B. Cordier, N. Dagoneau (CEA), U. Jacob (LUPM)
on behalf of the SVOM mission team.
At 2025-06-12T20:36:00 UTC (T0), SVOM/ECLAIRs triggered and located the X-ray transient sb25061218 (SVOM burst-id sb25061218).
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 1 alert. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.01 in the [8-120] keV energy band over a time window of 81.92 seconds starting at 2025-06-12T20:34:38.
The localization of the best alert is R.A., Dec. 198.5028, 54.6582 degrees:
R.A. (J2000) = 13h14m00.67s
Dec. (J2000) = 54d39m29.47s
with a 90% confidence level (C.L.) radius of 11.16 arcmin (including systematic error of 2 arcmin added in quadrature).
This burst was also detected by SVOM/GRM with a significance of 5.80.
Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst.
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. GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE.
The Burst Advocate (BA) on shift for this alert is Jerome Rodriguez: jerome.rodriguez(a)cea.fr.
Please contact the BA by email if you require additional information.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40712.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40711
SUBJECT: sb25061207: Swift-XRT observations
DATE: 25/06/12 21:12:28 GMT
FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk>
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
sb25061207, collecting 2.6 ks of Photon Counting (PC) mode data between T0+8.8 ks
and T0+20 ks after the trigger. We have detected 4 sources. These have been
automatically classified as follows:
* 0 likely counterparts
* 0 candidate counterparts
* 4 uncatalogued X-ray sources
* 0 known X-ray sources
Uncatalogued X-ray sources
--------------------------
Source 1 (SWIFT J131222.8+000431):
==================================
RA (J2000.0): 198.0954 = 13h 12m 22.90s
Dec (J2000.0): +0.0753 = +00d 04' 31.1"
Error: 6.4 (arcsec, radius, 90% confidence).
Detect flag: GOOD
Distance: 7.2 arcmin from the SVOM/ECLAIRs position;
4.6 arcsec from SVOM/VT counterpart (GCN 40707).
Mean rate: 0.0133 [+0.0031, -0.0028] ct s^-1
Mean flux: (6.0 [+1.4, -1.3])e-13 erg cm^-2 s^-1
Peak rate: 0.0147 +/- 0.0037 ct s^-1
Peak flux: (6.6 +/- 1.7)e-13 erg cm^-2 s^-1
ECF: 4.50e-11 erg cm^-2 ct^-1, assuming NH=2.24e+20 cm^-2,
gamma=1.42; determined from a spectral fit.
XMM UL: 2.7e-12 erg cm^-2 s^-1, (0.3-10 keV)
so the source is 12.4-sigma above this 3-sigma upper limit.
The source may be fading, at the 0.6-sigma level.
Source 2 (SWIFT J131136.2+000123):
==================================
RA (J2000.0): 197.9010 = 13h 11m 36.24s
Dec (J2000.0): +0.0233 = +00d 01' 23.9"
Error: 5.9 (arcsec, radius, 90% confidence).
Detect flag: GOOD
Distance: 5.2 arcmin from the SVOM/ECLAIRs position.
Mean rate: (7.2 +/- 2.1)e-3 ct s^-1
Mean flux: (7.4 +/- 2.1)e-13 erg cm^-2 s^-1
Peak rate: (7.2 +/- 2.1)e-3 ct s^-1
Peak flux: (7.4 +/- 2.1)e-13 erg cm^-2 s^-1
ECF: 1.03e-10 erg cm^-2 ct^-1, assuming NH=2.41e+21 cm^-2,
gamma=0.47; determined from a spectral fit.
XMM UL: 4.4e-12 erg cm^-2 s^-1, (0.3-10 keV)
so the source is 17.2-sigma above this 3-sigma upper limit.
There is no evidence for fading.
A SIMBAD object `MGC 42939' is 5.7" away.
Source 3 (SWIFT J131139.2-000814):
==================================
RA (J2000.0): 197.9134 = 13h 11m 39.22s
Dec (J2000.0): -0.1375 = -00d 08' 15.0"
Error: 7.3 (arcsec, radius, 90% confidence).
Detect flag: GOOD
Distance: 10.5 arcmin from the SVOM/ECLAIRs position.
Mean rate: (6.3 [+2.4, -1.9])e-3 ct s^-1
Mean flux: (1.36 [+0.52, -0.42])e-18 erg cm^-2 s^-1
Peak rate: (6.3 [+2.4, -1.9])e-3 ct s^-1
Peak flux: (1.36 [+0.52, -0.42])e-18 erg cm^-2 s^-1
ECF: 2.14e-16 erg cm^-2 ct^-1, assuming NH=4.37e+21 cm^-2,
gamma=96.83; determined from a spectral fit.
XMM UL: 2.7e-12 erg cm^-2 s^-1, (0.3-10 keV)
so the source is 5817530.8-sigma above this 3-sigma upper limit.
There is no evidence for fading.
Source 4 (SWIFT J131140.3-000120):
==================================
RA (J2000.0): 197.9181 = 13h 11m 40.34s
Dec (J2000.0): -0.0225 = -00d 01' 21.0"
Error: 6.1 (arcsec, radius, 90% confidence).
Detect flag: REASONABLE
Distance: 4.9 arcmin from the SVOM/ECLAIRs position.
Mean rate: (2.6 [+1.5, -1.2])e-3 ct s^-1
Mean flux: (1.61 [+0.96, -0.73])e-13 erg cm^-2 s^-1
Peak rate: (2.6 [+1.5, -1.2])e-3 ct s^-1
Peak flux: (1.61 [+0.96, -0.73])e-13 erg cm^-2 s^-1
ECF: 6.23e-11 erg cm^-2 ct^-1, assuming NH=3.65e+22 cm^-2,
gamma=2.45; determined from a spectral fit.
XMM UL: 4.8e-12 erg cm^-2 s^-1, (0.3-10 keV)
so the source is 55.2-sigma above this 3-sigma upper limit.
There is no evidence for fading.
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.
This circular is an official product of the Swift-XRT team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40711.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40710
SUBJECT: EP250612a/GRB 250612B: JinShan optical upper limit
DATE: 25/06/12 17:24:35 GMT
FROM: liuxing(a)nao.cas.cn
X. Liu, Z.P. Zhu, J. An, S.Q. Jiang, D. Xu (NAOC), S.Y. Fu(HUST), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of EP250612a detected by EP/WXT (Hua et al., GCN 40700), which is very likely GRB 250612B by Fermi/GBM (Preis & Greiner, GCN 40701; Fermi GBM tea, GCN 40702), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:45:13 UT on 2025-06-12, i.e., 3.29 hr after the EP trigger, and 18 x 200 s frames were obtained in the Sloan i-band.
No new optical source is detected within the EP/FXT error circle (Hua et al., GCN 40700), down to a 3-sigma upper limit of i ~ 20.2 mag (AB), calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.
We acknowledge the excellent support from T.Q. Chen for enabling these observations.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40710.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40709
SUBJECT: EP 250612a: AST3-3 Yaoan Optical Observation
DATE: 25/06/12 16:49:28 GMT
FROM: ylhua(a)pmo.ac.cn
Yan-Long Hua, Tian-Rui Sun, Lei Hu, Jin-Jun Geng, Xue-Feng Wu (PMO, CAS), report on behalf the AST3 Team:
Following the detection of EP 250612a detected by Einstein Probe (Hua et al., GCN 40700), and its potential gamma-ray counterpart by Fermi (Fermi GBM team, GCN 40702), we use Antarctic Survey Telescope 3-3 at Yaoan Astronomy Observation (China, Yunnan) to follow up for the afterglow.
We observed the target position with 30 x 180s exposure in g-band starting from 2025-06-12T13:12:59.95 about 0.75 hours after the burst.
No new optical source was detected within the error box (Hua et al., GCN 40700) down to 20.27 mag in the coadd image (total 30x180s, g-band).
View this GCN Circular online at https://gcn.nasa.gov/circulars/40709.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40708
SUBJECT: GRB 250612C: SVOM/GRM observation an intermedium duration burst
DATE: 25/06/12 16:01:33 GMT
FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn>
SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Ulysse Jacob (LUPM), Jean-Luc Atteia (IRAP)
Report on behalf of the SVOM team:
SVOM/GRM was triggered in-flight by a bright burst GRB 250612C (SVOM trigger reference: sb25061214) at 2025-06-12T14:53:16.700 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40704).
The real-time alert data and light curves of SVOM/GRM were downlinked to the ground through the VHF system with low latency. With the VHF data, the GRM light curve shows that this burst consists of a single spike with a T90 of 2.4 +/-0.8 s in the 15-5000 keV band. This burst is clearly detected in GRM VHF data beyond 550 keV, indicating a hard spectrum.
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250612C.png
At the time of the burst, ECLAIRs was not taking data.
Refined analysis will be reported later.
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 point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn)
View this GCN Circular online at https://gcn.nasa.gov/circulars/40708.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40707
SUBJECT: sb25061207: SVOM/VT optical counterpart
DATE: 25/06/12 15:40:31 GMT
FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn>
H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), L. Zhang (IHEP), Y.-D. Hu (GXU), X.-L. Chen (YNU) report on behalf of the SVOM mission team
SVOM performed an automatic slew on the burst (sb25061207) triggered by SVOM/ECLAIRs (Zhang et al., GCN 40697). SVOM/VT began observing the field at 2025-06-12T10:30:44 UTC, 202 seconds after Tb, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
A candidate is found using VT X-band data, compared to Legacy survey, within the error box of SVOM/Eclairs (Zhang et al., GCN 40697) at R.A., Dec 198.09415, +0.07508 degrees:
RA (J2000) = 13:12:22.597
Dec (J2000) = +00:04:30.28
with an uncertainty of 0.5 arcsec.
The source is detected in both VT_R and VT_B bands. With the data available, the light curve shows that this source was fading at first time, and then rebrightening to the peak of VT_R ~ 18.0 mag at around 1000 seconds after the trigger time, and then decayed.
mid-time | exposure time | band | mag (AB)
------------ |----------------- |-------------------
1.79 hour | 50 sec | VT_B | 21.6+/-0.2
1.79 hour | 50 sec | VT_R | 20.8+/-0.1
Given the VT colour of the candidate, it might be a low redshift transient.
We also noticed that there is a faint blue source at the Legacy survey image at the location of the candidate, which might be the host.
More followups are encouraged.
The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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.
The Burst Advocate (BA) on shift for this alert is Y.-D. Hu : hyd(a)gxu.edu.cn.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40707.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40706
SUBJECT: GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
DATE: 25/06/12 15:19:24 GMT
FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de>
T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report:
The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger
771432801 at 14:53:16 on 12 June 2025 were automatically fitted for spectrum
and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427;
Berlato et al. 2019, ApJ 873, 60).
The best-fit position is:
RA(2000.0) = 118.9 deg
Decl.(2000.0) = 18.8 deg
The 1 sigma statistical error radius is 1.1 deg.
We estimate an additional systematic error of 1 deg.
Further details are available at:
https://grb.mpe.mpg.de/grb/GRB250612620/
The Healpix map can be downloaded from:
https://grb.mpe.mpg.de/grb/GRB250612620/healpix
The location parameters are available as JSON at:
https://grb.mpe.mpg.de/grb/GRB250612620/json
View this GCN Circular online at https://gcn.nasa.gov/circulars/40706.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40705
SUBJECT: GRB 250610B: Swift-XRT refined Analysis
DATE: 25/06/12 15:11:21 GMT
FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk>
P. D'Avanzo (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A.
Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U.
Leicester), M.G. Bernardini (INAF-OAB), E. Ambrosi (INAF-IASFPA) and
P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team:
We have analysed 5.0 ks of XRT data for GRB 250610B, from 2.9 ks to
105.7 ks after the SVOM/ECLAIRs trigger. The data are entirely in
Photon Counting (PC) mode. Using 2013 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 =
200.17991, +31.10477 which is equivalent to:
RA (J2000): 13h 20m 43.18s
Dec(J2000): +31d 06' 17.2"
with an uncertainty of 2.8 arcsec (radius, 90% confidence).
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.68 (+0.12, -0.10).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.86 (+0.33, -0.25). The
best-fitting absorption column is 3.1 (+7.7, -2.0) x 10^20 cm^-2,
consistent with the Galactic value of 1.1 x 10^20 cm^-2 (Willingale et
al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux
conversion factor deduced from this spectrum is 3.5 x 10^-11 (3.7 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 3.1 (+7.7, -2.0) x 10^20 cm^-2
Galactic foreground: 1.1 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.86 (+0.33, -0.25)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00019863.
This circular is an official product of the Swift-XRT team.
View this GCN Circular online at https://gcn.nasa.gov/circulars/40705.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…
TITLE: GCN CIRCULAR
NUMBER: 40703
SUBJECT: EP250610a: Upper limit from Fermi-GBM Observations
DATE: 25/06/12 14:32:39 GMT
FROM: mariaedvige.ravasio(a)ru.nl
M. E. Ravasio (Radboud Univ.), E. Burns (LSU), and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team:
Fermi-GBM had full spatial coverage of the transient EP250610a detected by EP-WXT (Zhang et al., GCN 40660, Lian et al. GCN 40669). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-06-10T04:23:24 UTC.
The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. No signal consistent with the EP transient, both temporally and spatially, is identified, as confirmed also by visual inspection of the data.
Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 2.8e-08 erg/cm2/s in the energy band 10-1000 keV.
[1] Goldstein et al. 2019 arXiv:1903.12597
View this GCN Circular online at https://gcn.nasa.gov/circulars/40703.
---
To unsubscribe, open this link in a web browser:
https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…