- GCN Circular #38697
Yifang Liang (PMOC), An Li (BNU), Wenjin Xie, Donghua Zhao (NAOC), Hui Yang (IRAP), Hatsune Goto (CEA), Li Zhang (IHEP), Lipin Xin (NAOC) report:
At 2024-12-29T00:04:21 (Tb) SVOM/ECLAIRs triggered on GRB 241229A (SVOM burst-id sb24122901).
The following trigger information was received on the ground with low-latency by the SVOM VHF Alert Network. A total of 8 Alerts were received from Count-Rate Trigger (CRT) and Image Trigger (IMT). The best Alert was produced by CRT with a signal-to-noise ratio of 11.0 in the 8-120 keV energy band over a time window of 20.48 s starting at Tb.
The localization of the best Alert is RA, DEC = 192.893, +31.857 (J2000) with a 90% C.L. radius of 7.6 arcmin (including a systematic error of 2 arcmin added in quadrature).
SVOM slewed automatically to the burst. GRM, MXT and VT data will be reported later.
Burst Advocate for this burst is Yifang Liang (yfliang@pmo.ac.cn). Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
- GCN Circular #38705
A. Kumar, S. Belkin, D. O'Neill, G. Ramsay, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, F. Jimenez-Ibarra, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, 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 241229A (Liang et al., GCN 38697) in survey mode at 03:42:28 UT on 2024-12-29 (3.64 hours after the trigger). The observation was taken by GOTO-North, and consisted of 3x45s 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.
No new optical source consistent with the SVOM/ECLAIRs localisation is identified to a 3-sigma limiting magnitude of L > 19.6.
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 #38711
P. A. Evans (U. Leicester) reports on behalf of the Swift team:
Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 241229A.
Automated analysis of the XRT data will be presented online at
https://www.swift.ac.uk/ToO_GRBs/00021751
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 #38726
S.Q. Jiang, J. W. Hu, W. J. Zhang, X.P. Xu (NAO, CAS), W.F. Wen (SZTU), J. H. Wu (GU), H.W. Pan, Z.X. Ling (NAO, CAS), B. Cordier (CEA) on behalf of Einstein Probe teams:
We performed a follow-up observation of GRB 241229A (SVOM/ECLAIRs, Liang et al., GCN 38697) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2024-12-29 14:11:35 (T-TGRB ~ 14.1 hr) for about 3 ks of exposure in total.
Three uncatalogued X-ray sources are detected by both FXT-A and FXT-B within the 7.6 arcmin error circle of SVOM/ECLAIRs (Liang et al., GCN 38697). We list the sources in the following table, with the seperations from the ECLAIRs source given. The observed 0.5-10 keV flux given in the table is a rough estimate assuming the same spectral paramters, and is not corrected for absorption.
| FXT source | R.A. (deg, J2000) | DEC (deg, J2000) | Sep. (arcmin) | Flux (erg/s/cm^2) |
| EPF_J125139.4+315311 | 192.9133 | 31.8867 | 2.06 | 6.82 x 10^(-14) |
| EPF_J125129.3+314453* | 192.8715 | 31.7484 | 6.61 | 7.73 x 10^(-13) |
| EPF_J125101.6+315007 | 192.7572 | 31.8356 | 7.04 | 9.25 x 10^(-14) |
* sources also detected by Swift/XRT (Evans et al., GCN 38711)
Further follow-up observation will be performed by the EP-FXT to confirm the afterglow of GRB 241229A.
The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
- GCN Circular #38728
M. A. Williams (PSU), S. Dichiara (PSU), J.P. Osborne (U. Leicester),
K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), R. Brivio
(INAF-OAB), A. D'Ai (INAF-IASFPA), A. Melandri (INAF-OAR), J.A. Kennea
(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 241229A, collecting 1.9 ks of Photon
Counting (PC) mode data between T0+65.5 ks and T0+72.9 ks.
One uncatalogued X-ray source has been detected, it is below the RASS
limit and shows no definitive signs of fading. Therefore, at the
present time we cannot confirm this as the afterglow.
This source is 7.1 arc-seconds from the 2nd source in the list of the
afterglow candidates reported by Einstein Probe/FXT (GCN #38726).
Details of this source are given below:
Source 1:
RA (J2000.0): 192.8735 = 12:51:29.63
Dec (J2000.0): +31.7474 = +31:44:50.6
Error: 4.3 arcsec (radius, 90% conf. [Enhanced position])
Count-rate: 0.0172 +/- 0.0038 ct s^-1
Distance: 399 arcsec from SVOM/ECLAIRs position.
Flux: (4.32 +/- 0.96)e-13 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/00021751.
This circular is an official product of the Swift-XRT team.
- GCN Circular #38731
A. S. Moskvitin, O. I. Spiridonova (SAO RAS), A. S. Pozanenko (IKI RAS)
report on behalf of the GRB follow-up team.
We partially covered the error circle of SVOM/ECLAIRs GRB 241229A
(Liang et al., GCN 38697) with the 1-m telescope of SAO RAS, Zeiss-1000
equipped with the CCD-photometer. We obtained 6 x 300 sec. images
in Rc band on 2024-12-29T23:40:01--2024-12-30T00:16:47
(t_mid - T0 = 23.9 hours).
Within the enhanced XRT position (Williams et al., GCN 38728)
of X-ray candidate previously reported by Evans (GCN 38711) and
Jiang et al. (GCN 38726, EP-FXT candidate #2) we did not detect any new
source down to the limiting magnitude of R_lim = 22.3.
We should note the presence of the nearby galaxy J125129.26+314455.4
visible in archive images with the brightness of R2 = 20.39 (USNO-B1)
and r = 20.402 +/- 0.043 (SDSS). In our stacked frame we measured
the brightness of the galaxy as R = 20.26 +/- 0.05 (diameter
of aperture 9".94, calibrated against R2 magnitudes of nearby USNO-B1
stars). The angular distance from EP candidate position
to the measured center of the galaxy is 2".5 (corresponding 18 kpc,
z_phot = 0.2875, H0 = 72 km/s/Mpc), and 6".7 (47 kpc)
from XRT position to the galaxy.
- GCN Circular #38740
S. Q. Jiang, J. W. Hu, H. Sun, W. J. Zhang, X. P. Xu (NAO, CAS), W. F. Wen (SZTU), J. H. Wu (GU), H.W. Pan, Z. X. Ling (NAO, CAS), B. Cordier (CEA) on behalf of Einstein Probe teams:
We performed further follow-up observations of GRB 241229A (SVOM/ECLAIRs, Liang et al., GCN 38697) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The first epoch of the observation started at 2024-12-30T09:24:30 (T-TGRB ~ 1.39 days) with an exposure time of 2 ks, and a second epoch was performed at 2024-12-30T16:06:04 (T-TGRB ~ 1.67 days) with an exposure time of 5 ks.
The flux of the first (EPF_J125139.4+315311) and the third (EPF_J125101.6+315007) sources reported in Jiang et al., GCN 38726 remained almost constant over all the observations.
The second source EPF_J125129.3+314453, which is also detected by Swift/XRT (Williams et al., GCN 38728) shows a clear flux decay with a powerlaw index of ~ 0.8. The unabsorbed 0.5-10 keV flux given in the below table is calculated by assuming the same spectral index 1.86 and fixed with the Milky Way equivalent hydrogen column density nH of 1.43 x 10^20 cm^-2:
Observation start time [UTC] | exposure time [s] | 0.5 - 10 keV unabsorbed flux [erg/s/cm2]
2024-12-29T14:11:35 | 2828 | 7.94 (+2.12 -1.53) x 10^(-13)
2024-12-30T09:24:30 | 2212 | 4.19 (+0.81 -0.72) x 10^(-13)
2024-12-30T16:06:04 | 4898 | 3.50 (+1.14 -0.77) x 10^(-13)
Thus we claim that this source is very likely the afterglow of GRB 241229A.
The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES.
- GCN Circular #38817
Anshika Gupta, Amit K. Ror, Pranshu, Kuntal Mishra, and Shashi B. Pandey (ARIES) report:
We observed the field of GRB 241229A detected by SVOM (Liang et al 2024, GCN 38697) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations were started on 2024-12-31 at 21:30:48 UT, i.e., ~ 2.89 days after the SVOM trigger. We have taken multiple frames with an exposure time of 300 s in the R filter. We stacked the images after the alignment. We could not detect the optical emission in our stacked image within the error box of SVOM/ECLAIRs (Liang et al. 2024, GCN 38697) and Swift-XRT (Williams et al. 2024, GCN 38728). We obtain the following 3-sigma upper limit in the stacked image:
Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude
=========================================================
2024-12-31 21:30:48 ~2.89 R 300s*24 >21.4
The non-detection of the burst is consistent with the upper limits reported by Kumar et al. 2024, GCN 38705; Moskvitin et al. 2024, GCN 38731.
The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalogue. This circular may be cited.
- GCN Circular #38824
SVOM/VT commissioning team: Y. L. Qiu, H. L. Li (NAOC), Y. F. Liang (PMOC), A. Li, Z. M. Wang (BNU), 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, Z. H. Yao (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM)
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 241229A (Liang et al., GCN 38697) was observed by SVOM/VT after the automatic slew of the platform. Additional ToO follow-up observation was also carried out. The VT conducted observations in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channel simultaneously.
No any new source was detected in single or stacked images within the errorbox of Swift/XRT (M. A. Williams et al., GCN 38728) and Einstein Probe/FXT (S. Q. Jiang et al., GCN 38726, GCN 38740).
The 3 sigma limits in AB magnitude were derived as follows:
VT_B=21.8 mag and VT_R=21.8 mag with an exposure time of 100 sec at the mid time of about 1.4 hours after the burst.
VT_B=23.2 mag with exposure time of 1980 sec and VT_R= 22.5 mag with exposure time of 960 sec, at the mid time of about 10.9 hours after 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.
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