- GCN Circular #38786
Y. Wang (PMO, CAS), J-X. Cao (GXU), D. Turpin (CEA), S. Guillot (IRAP), H. Goto (CEA), F. Daigne (IAP), L. Zhang (IHEP) report on behalf of the SVOM team:
The SVOM/ECLAIRs telescope triggered and located the long duration GRB 250103A (sb25010301) starting at 2025-01-03T09:56:33.551 UTC (Tb).
The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network.
The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 18 alerts were received. The best detection is obtained by CRT with a signal-to-noise ratio of 18.6 in the 8-50 keV energy band over a time window of 20 s starting at Tb.
The localization of the best Alert is RA, Dec = 22.083, -5.096 (J2000). The statistical uncertainty on this position is 4.6 arcminutes, which includes a systematic uncertainty of 2 arcminutes in quadrature.
The light curve shows multiple broad peaks in 5-120 keV in ECLAIRs and below 550 keV in GRM with a preliminary T90 duration greater than 250 s (5-120 keV).
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250103A.png
SVOM slewed automatically on this burst.
MXT began observing the field at 2025-01-03T10:12:28 UTC, 955 seconds after Tb. No X-ray afterglow candidate has been detected in the MXT field of view by the on-board software. Further analysis will be conducted once the X-band telemetry data are received.
The Space 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.
The SVOM point of contact for this burst is: Yun Wang (wangyun@pmo.ac.cn)
- GCN Circular #38787
Y. Wang (PMO, CAS), J-X. Cao (GXU), D. Turpin (CEA), S. Guillot (IRAP), H. Goto (CEA), F. Daigne (IAP), L, Zhang (IHEP) report on behalf of the SVOM team:
The SVOM/ECLAIRs telescope triggered and located the long duration GRB 250103A (sb25010301) starting at 2025-01-03T09:56:33.551 UTC (Tb).
The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network.
The burst was detected by both the on-board Count-Rate Trigger (CRT) and Image Trigger (IMT) and 18 alerts were received. The best detection is obtained by CRT with a signal-to-noise ratio of 18.6 in the 8-50 keV energy band over a time window of 20 s starting at Tb.
The localization of the best Alert is RA, Dec = 22.083, -5.096 (J2000). The statistical uncertainty on this position is 4.6 arcminutes, which includes a systematic uncertainty of 2 arcminutes in quadrature.
The light curve shows multiple broad peaks in 5-120 keV in ECLAIRs and below 550 keV in GRM with a preliminary T90 duration greater than 250 s (5-120 keV).
The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250103A.png
SVOM slewed automatically on this burst.
MXT began observing the field at 2025-01-03T10:12:28 UTC, 955 seconds after Tb. No X-ray afterglow candidate has been detected in the MXT field of view by the on-board software. Further analysis will be conducted once the X-band telemetry data are received.
The Space 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.
The SVOM point of contact for this burst is: Yun Wang (wangyun@pmo.ac.cn)
- GCN Circular #38791
SVOM/C-GFT team: Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC),Yulei Qiu (NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC)
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC),Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV)
We observed the field of GRB 250103A (Wang et al., GCN 38787) starting at 2025-01-03T09:57:26, ~83 sec after the burst trigger with C-GFT. A series of g,r,i band images were obtained with exposure time of 10s for each frame. No any uncataloged sources were detected within the SVOM/ECLAIRs error circle (Wang et al., GCN 38787) compared to PanSTARRS1 catalog. 3 sigma limit magnitude of i=19.4 was derived at the middle time of ~120 s after the trigger.
We thank the observation assistant Guangsheng Zhang and Yinhuai Hao at Jilin observatory for their excellent support.
Chinese Ground Follow-up Telescope of SVOM mission is located at Jilin, Changchun Observatory, National Astronomical Observatories, CAS. It has FOV of 1.28 deg x 1.28 deg with a 4k*4k CMOS detector mounted on the primary focus of 1.2-meter-aperure telescope.
- GCN Circular #38792
R. Starling, D. O’Neill, A. Kumar, B. Godson, B. P. Gompertz, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, E. Palle and D. Pollacco report on behalf of the GOTO collaboration:
The Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) serendipitously covered the field of SVOM-triggered GRB 250103A (Wang et al. GCN 38787) at 11:06:02 UT on 2025-01-03 (1.17 hours after the trigger). The observation was taken by GOTO-South, and consisted of 4x90s exposures in the GOTO L-band (400-700 nm).
Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations of the same pointings. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogues.
We do not identify any candidate optical counterparts within the SVOM localisation uncertainty region, down to a 3-sigma limiting magnitude of L > 19.8, consistent with the non-detection reported by Wu et al. (GCN 38791).
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC).
- GCN Circular #38795
R.-Z. Li, B.-T. Wang, J. Mao (YNAO, CAS), L. P. XIN, J. Y. Wei, H. L. Li, Y. L. Qiu, J. Wang, C. Wu, X. H. Han (NAOC), J. X. Cao, D. F. Kong (GXU) and Y. Wang (PMO, CAS) report on behalf of SVOM team:
We observed the field of GRB 250103A (Wang et al., GCN 38786) using the 2.16m telescope at the Xinglong Observatory, China. The observation began at 2025-01-03T11:41:12 UTC, about 1.74 hours after the trigger. 5*200 sec I-band images were obtained.
An uncataloged bright source was detected in I-band images within the error box of SVOM/ECLAIR (Wang et al., GCN 38786), compared to Pan-STARRS1 image. The coordinates (J2000):
R.A. = 01:28:15.29
DEC. = -05:03:06.4
with an uncertainty of 0.5 arcseconds.
The preliminary analysis results are shown as follows:
+-------------------+------------+----------+--------------+----------------+
| Tstart (UTC) | Exp. [s] | Filter | Mag | 5-sigma U.L. |
+===================+============+==========+==============+================+
|2025-01-03T11:41:12| 5*200 | I | 19.49 ± 0.04 | 21.5 |
+-------------------+------------+----------+--------------+----------------+
We propose it is the candidate of the burst. More follow-ups are encouraged to confirm the nature of the source.
The given magnitudes are derived based on calibration against Pan-STARRS1 field stars, and are not corrected for the expected Galactic foreground extinction, corresponding to a reddening of E(B-V) = 0.0362 mag in the direction of the optical counterpart (Schlafly & Finkbeiner 2011).
- GCN Circular #38800
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 250103A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021752
Any uncatalogued X-ray sources detected in this analysis will be
reported on this website and via GCN COUNTERPART notices. These are
not necessarily related to the SVOM/ECLAIRs event. Any X-ray source
considered to be a probable afterglow candidate will be reported via a
GCN Circular after manual consideration.
Details of the XRT automated analysis methods are detailed in Evans et
al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8).
This circular is an official product of the Swift-XRT team.
- GCN Circular #38802
SVOM/VT commissioning team: Y. L. Qiu, H. L. Li, L. P. Xin, C. Wu, X. H. Han, J. Wang, W. J. Xie, H. B. Cai, Y. Xu, Y. J. Xiao, P. P. Zhang, J. S. Deng, L. Lan, X. M. Lu, R. S. Zhang, D. H. Zhao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM), R.-Z. Li, J. X. Cao, D. F. Kong (GXU) and Y. Wang (PMO, CAS)
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), Olivier Godet (IRAP), Andrea Goldwurm (APC), Diego Götz (CEA), Xu-Hui Han (NAOC), Cyril Lachaud (APC), En-Wei Liang (GXU), Yu-Lei Qiu (NAOC), Susanna Vergani (Obs.Paris), Jing Wang (NAOC), Chao Wu (NAOC), Li-Ping Xin (NAOC), Shao-Lin Xiong (IHEP), Bing Zhang (UNLV)
report on behalf of the SVOM team:
GRB 250103A (Wang et al., GCN 38786) was observed by on-board VT after the automatic slew of the platform. The VT conducted observations in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
With the X band downlinked data, the optical candidate reported (Li et al., GCN 38795) was detected in VT_B and VT_R band images.
Its brightness was rising for 1.0 mag from 500 sec to 2000 sec after the burst and then decays. The magnitude was VT_B=21.8+/0.1 mag and VT_R=20.1+/0.1 mag in AB magnitude, at about 8000 seconds post the trigger.
We confirm that this source is the optical counterpart of the burst.
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 #38806
A. C. Trigg (LSU), U. Pathak (IITB) reports on behalf of the Fermi Gamma-ray Burst Monitor Team:
"At 09:57:46.56 UT on 03 January 2025, the Fermi Gamma-ray Burst Monitor (GBM)
triggered and located GRB 250103A (trigger 757591071/250103415).
which was also detected by SVOM (Y. Wang et al. 2025, GCN 38787).
The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position.
The angle from the Fermi LAT boresight is 28 degrees.
The GBM light curve an initial emission followed by two smaller peaks with a duration (T90)
of about 118 s (50-300 keV). The time-averaged spectrum
from T0-7.6 to T0+112.3 s is best fit by
a power law function with an exponential high-energy cutoff.
The power law index is -1.75 +/- 0.09 and the cutoff energy,
parameterized as Epeak, is 33 +/- 5 keV.
The event fluence (10-1000 keV) in this time interval is
(5.5 +/- 0.3)E-06 erg/cm^2. The 1-sec peak photon flux measured
starting from T0+4.3 s in the 10-1000 keV band is 2.8 +/- 0.2 ph/s/cm^2.
A Band function fits the spectrum equally well
with Epeak= 32 +/- 4 keV, alpha = -1.70+/- 0.13 and beta = -2.65 +/- 0.38.
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/"
- GCN Circular #38807
I. Reva (FAI), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (HSE, IKI)
report on behalf of GRB IKI FuN:
We observed the field of GRB 250103A (Wang et al., GCN 38786) which also
triggered GBM/Fermi (Trigg et al., GCN 38806) with Zeiss-1000 telescope of
THSAO observatory in R-filter starting on 2025-01-03 (UT) 16:12:14.05. In a
stacked image we do not detect the optical afterglow (Li et al., GCN 38795;
SVOM/VT commissioning team, GCN 38802), and which is consistent with non
detection of the afterglow (SVOM/C-GFT team, GCN 38791; Starling et al.,
GCN 38792).
Preliminary photometry of the field is the following
Date UT start t-T0 Filter Exp. OT Err UL(3sigma)
mid, days
2025-01-03 16:12:14 0.26231 R 11*120 n/d n/d 19.0
The photometry is based on nearby USNO-B1.0 (R2) stars.
- GCN Circular #38808
D. Xu (NAOC), Z. P. Zhu (NAOC), D. B. Malesani (DAWN/NBI and Radboud Univ.), L. Izzo (INAF/OACn), A. de Ugarte Postigo (CNRS, OCA and LAM), A. Saccardi (CEA/Irfu), K. Valeckas (NBI), report on behalf of a larger collaboration:
We observed the optical counterpart (Li et al., GCN 38795; Qiu et al., GCN 38802) of the SVOM GRB 250103A (Wang et al., GCN 38786, 38787), using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Two observations by 200 s each were secured in the i band, with a mean time 2025 Jan 3.90 UT (8.16 hr after the GRB).
The optical counterpart is well detected, with an AB magnitude i = 21.14 +- 0.04, calibrated against nearby objects from the Pan-STARRS catalog.
We note that a relatively bright object (i ~ 22.8) is detected in the Legacy survey directly underlying the position of the optical afterglow.
- GCN Circular #38809
A. de Ugarte Postigo (CNRS, OCA and LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), C. C. Thoene (ASU-CAS, AbAO), J. F. Agui Fernandez (CAHA), N. R. Tanvir (Univ. Leicester), L. Izzo (INAF/OACn and DARK/NBI), J. P. U. Fynbo (DAWN/NBI), S. Geier (GTC), G. Lombardi (GTC), A. Martin-Carrillo (UCD), N. A. Rakotondrainibe (LAM), Riccardo Scarpa (GTC) and Alvaro Tejero (GTC), report:
We observed the optical counterpart of GRB 250103A (Wang et al. GCN 38786, Li et al. GCN 38795, Qiu et al. GCN 38802, Trigg et al. GCN 38806, Xu et al. GCN 38808) with OSIRIS+, mounted on the 10.4 m GTC, at Roque de los Muchachos Observatory, in the island of La Palma (Spain). The observation started at 2025-01-03T22:03:11.011 UT (12.11 hr after the burst) consisted of an r-band acquisition followed by a single 1200 s spectrum with grism R1000B, covering the range between 3600 and 7800 AA. Although the planned observation was longer, weather and technical issues prevented us from completing the planned observation.
In a preliminary reduction, the spectrum shows a red trace with strong features that we identify as being due to the Lyman-alpha forest, a broad damped Lyman-alpha feature, and strong lines of SiII, SiII*, SiIV, OI, CII, CIV, amongst others, at a common redshift of 4.01. Further analysis is ongoing.
The underlying galaxy mentioned by Xu et al. (GCN 38808) has AB magnitudes in the Legacy survey of g=24.55, r=23.16, i=22.77, z=22.52. We note that this photometry does show a break in the g-band, which would be consistent with the Lyman break at z = 4. However, if this object is indeed the host galaxy, it would have an extraordinary luminosity at z=4.01, with an absolute magnitude M(UV) ~ -23 mag.
- GCN Circular #38811
S. Leonini, M. Conti, P. Rosi, L.M. Tinjaca Ramirez (Montarrenti Observatory, Siena, Italy, part of UAI/SSV-GRB section), M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report:
We observed the field of SVOM triggered GRB 250103A (Wang et al., GCN 38786, GCN 38787) with the automated and remoted 0.53m Ritchey-Chretien telescope at Montarrenti Observatory (Siena, Italy, IAU code C88).
The observations were started at 2025-01-03 17:58:28 UT (approximately 8 hours after burst) stacking a set of Ic-band CCD images. Observations were performed under thin cloud cover in the first part of the night.
The OT was barely detected (S/N =1.7) at the following position:
RA (J2000.0) 01h 28m 15.28s +/-0.05
Decl. (J2000.0) -05° 03' 06.59" +/-0.12
Preliminary photometry was obtained using nearby PanSTARRS stars as follows:
Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err. UL (3-sigma)
2025-01-03 18:55:32 UT 8.98 111x40s Ic 20.7 S/N =1.7 >20.4
Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied.
Our observations are consistent with other already reported (Li et al., GCN 38795; Qiu et al., GCN 38802; Xu et al., GCN 38808).
- GCN Circular #38814
Z.P. Zhu, D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Saccardi (CEA/Irfu), K. Valeckas (NBI) report on behalf of a large collaboration:
We carried out spectroscopy of the optical counterpart (e.g., Li et al., GCN 38795; Qiu et al., GCN 38802; Xu et al., GCN 38808; Leonini et al., GCN 38811) of GRB 250103A detected by SVOM/ECLAIRs (Wang et al., GCN 38786) and Fermi/GBM (Trigg et al., GCN 38806), using the the ALFOSC instruments mounted on the Nordic Optical Telescope (NOT). Observations started at 21:49:26 UT on 2025-01-04, i.e., 11.88 hrs after the burst, consisted of 2 exposures of 1200 s each, and the spectra cover the wavelength range 3600 - 9000 AA.
The whole spectrum has a fairly low S/N, but absorption features are evident. From the detection of a Lya absorption feature at ~ 6088 AA and multiple absorption features, which interpreted as being due to Si II, C II, Si IV, C IV, Fe II, and Al II, we infer a common redshift of z = 4.01, fully consistent with the measurement from GTC (de Ugarte Postigo et al., GCN 38809). We conclude this is the redshift of the burst.
- GCN Circular #38819
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri
(INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea
(PSU), D.N. Burrows (PSU), M. A. Williams (PSU) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the
SVOM/ECLAIRs-detected burst GRB 250103A, collecting 2.0 ks of Photon
Counting (PC) mode data between T0+24.1 ks and T0+47.2 ks.
One uncatalogued X-ray source has been detected within the estimated
3-sigma SVOM/ECLAIRs error region (454 arcsec), it is below the RASS
limit and shows no definitive signs of fading. However, it is
consistent with the position of the optical afterglow candidate (Li et
al. GCN 38795, Qiu et al. GCN 38802, Xu et al. GCN 38808). Details of
this source are given below:
Source 1:
RA (J2000.0): 22.0647 = 01:28:15.54
Dec (J2000.0): -5.0517 = -05:03:06.0
Error: 4.3 arcsec (radius, 90% conf.)
Count-rate: 0.0853 +/- 0.0076 ct s^-1
Distance: 172 arcsec from SVOM/ECLAIRs position.
Flux: (2.93 +/- 0.26)e-12 erg cm^-2 s^-1 (observed, 0.3-10 keV)
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/ToO_GRBs/00021752.
This circular is an official product of the Swift-XRT team.
- GCN Circular #38821
U.Quadri, L.Strabla and P.Madurini (Bassano Bresciano Astronomical Observatory)
Members of:
GRB/UAI - Gamma ray Burst section of Unione Astrofili Italiani.
AAVSO - American Association of Variable Star Observers.
GAC - Gruppo Astrofili Cremonesi.
In a large collaboration with:
M.G. Dainotti (National Astronomical Observatory of Japan),
Y. Niino (Tokyo University, Institute of Astronomy),
K. Kalinowski (Aarhus University, Department of Physics and Astronomy),
B. De Simone (Universita' degli Studi Di Salerno)
report:
We imaged the field of GRB 250103A detected by SVOM with the robotic telescope of (IAU station 565) Bassano Bresciano Observatory, Italy.
The observations started 7h 55m after the GRB trigger with our Newton telescope D=450 mm F/D=4.5.
We co-added 2 series of 100 exposures of 20 sec each.
Start T0+ End T0+ Rc lim. Err.
7h 46m 8h 27m 20.2 +/- 0.1
8h 28m 9h10m 20.2 +/- 0.1
We did not found any optical uncatalogued object within the SVOM error circle.
Magnitudes were estimated with the pan-STARRS cat and are derived using Lupton (2005) equations.
Not corrected for galactic dust extinction.
Reference:
http://www.osservatoriobassano.org
The message may be cited.
- GCN Circular #38849
A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), A. Melandri
(INAF-OAR), T. Sbarrato (INAF-OAB), P. D'Avanzo (INAF-OAB), J.A. Kennea
(PSU), D.N. Burrows (PSU), M. A. Williams (PSU) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
Swift-XRT has conducted further observations of the field of the
SVOM/ECLAIRs-detected burst GRB 250103A. The observations now extend
from T0+24.3 ks to T0+432.8 ks and have a total exposure time of 5.5
ks. The source previously reported, "Source 1", is fading with >3-sigma
significance, and is therefore likely the GRB afterglow. Using 1509 s
of PC mode data and 3 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 = 22.06415, -5.05179 which is equivalent
to:
RA (J2000): 01h 28m 15.40s
Dec(J2000): 05d 03' 06.4"
with an uncertainty of 2.5 arcsec (radius, 90% confidence). This
position is 2.9 arcmin from the SVOM/ECLAIRs position.
The light curve can be modelled with a power-law decay with a decay
index of alpha=0.82 (+0.24, -0.18).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 2.14 (+0.31, -0.28). The
best-fitting absorption column is 1.4 (+0.9, -0.7) x 10^21 cm^-2, in
excess of the Galactic value of 4.5 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 3.2 x 10^-11 (4.4 x 10^-11) erg
cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 1.4 (+0.9, -0.7) x 10^21 cm^-2
Galactic foreground: 4.5 x 10^20 cm^-2
Excess significance: 2.3 sigma
Photon index: 2.14 (+0.31, -0.28)
The results of the XRT-team automatic analysis of the likely afterglow
are at https://www.swift.ac.uk/ToO_GRBs/00021752/Source1.php.
The results of the full analysis of the XRT observations are available
at https://www.swift.ac.uk/ToO_GRBs/00021752.
This circular is an official product of the Swift-XRT team.
- GCN Circular #38854
Guowang Du, Jinghua Zhang, Yangwei Zhang, Brajesh Kumar, Xufeng Zhu, Fanchuan Kong, Chenxi Shang, Yuan Fang, Xinlei Chen, Xingzhu Zou, Yu Pan, Yuanpei Yang (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of GRB 250103A (sb25010301) detected by SVOM/ECLAIRs (Wang et al. GCN 38786) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Simultaneous uvgriz band photometric observations were conducted starting from 11:35:51 2025-01-03 UT (~1.65 hr after the SVOM/ECLAIRs trigger) and several frames with different exposure times were taken. There is detection of the optical candidate (Li et al., GCN 38795; Qiu et al., GCN 38802; Xu et al., GCN 38808; Leonini et al., GCN 38811) in our r and i band single frames but not in the stacked images of uvgz bands. The preliminary photometry and 3 sigma upper limits are below:
Start_Time(UT) | Band | Exp(s) | Mag/LimMag (AB)
---------------------------|--------|----------------
2025-01-03T11:35:52 | u | 180*2 | >21.89
2025-01-03T11:43:02 | v | 180*2 | >22.28
2025-01-03T11:35:52 | g | 50*6 | >22.15
2025-01-03T11:43:03 | r | 50*1 | 20.91(+/-0.35)
2025-01-03T11:35:51 | i | 79*1 | 19.72(+/-0.32)
2025-01-03T11:43:02 | z | 79*4 | >20.46
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Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21.
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