- GCN Circular #38594
Brunet Marius, Fortin Francis (IRAP), Turpin Damien, Stéphane Schanne, Clara Plasse (CEA), Frédéric Piron (LUPM), Shi-Jie Zheng (IHEP)
report on behalf of the SVOM team:
During the commissioning phase, the SVOM/ECLAIRs telescope triggered and located the long duration GRB 241217A (sb24121704) starting at 2024-12-17T16:57:13 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 9 alerts were received. The best detection is obtained by IMT with a signal-to-noise ratio of 11.9 in the 8-120 keV energy band over a time window of 82 s starting at Tb. The light light curve shows multiple broad peaks in 5-50 keV in ECLAIRs and below 550 keV in GRM.
The localization of the best Alert is RA, Dec = 84.160, -25.324 (J2000).
The statistical uncertainty on this position is 6.8 arcminutes, which includes a systematic uncertainty of 2 arcminutes in quadrature.
SVOM slewed automatically on this burst.
MXT began observing the field at 2024-17-12T17:01:36, 263 seconds after Tb.
Using onboard processed data we found one very bright uncatalogued X-ray source located at RA, Dec 84.152, -25.295 degrees with a 90% C.L. radius of 25 arcsec (statistic + systematic), corresponding to:
R.A. = 05h 36m 36s
Dec = -25° 17' 33"
This location is 1.8 arcminutes from the ECLAIRs onboard position.
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: Brunet Marius (marius.brunet@irap.omp.eu)
- GCN Circular #38597
T. Hussenot-Desenonges (IJCLAB), L. De Almeida, W. Corradi, N. Sasaki, F. Navarete (LNA), H. Peng (THU), H. Lau Jun Xian (Tsinghua Univ.), A. Klotz (IRAP), S. Antier (OCA), C. Andrade (UMN), S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), on behalf of the GRANDMA collaboration:
We observed the field of GRB 241217A, detected by SVOM/ECLAIRs (GCN 38594) using TAROT/TRE. Observations (unfiltered) began at 2024-12-17T17:22:00UTC, 19 min after T0 and continued up to 45 min after T0.
We did not detect any optical afterglow candidate in our stacked images within a 5-sigma upper limit of r > 18.1 (AB magnitude, calibrated with PanSTARRS).
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022).
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).
- GCN Circular #38598
D. Turpin, J. T. Palmerio (CEA/Irfu), S. Vergani (GEPI/Obs. de Paris), A. Saccardi (CEA/Irfu), S. Basa (UAR Pytheas, OHP, LAM), E. Le Floc'h (CEA Paris-Saclay, DAp/AIM), L.-P Xin (NAOC) on behalf of a larger collaboration.
We observed the field of GRB 241217A detected by SVOM (Brunet et al., GCN 38594) with the LCO 1.0m telescope at the Sutherland Observatory (SAAO) equipped with the Sinistro instrument. Our observation started at 2024-12-17 19:17:34.013 UTC (T - TGRB ~ 2.3 h) with 4 x 180s exposure using the sdss-r filter. Despite good weather conditions, we note a slightly loss of telescope tracking during our single exposures which reduced a bit our image quality.
We did not detect any uncatalogued optical source inside the refined SVOM/MXT afterglow candidate position (Brunet et al., GCN 37594). In our first image, we derived the preliminary following upper limit (3 sigma, AB system) calibrated with the PanSTARRS DR1 catalog and not corrected from the galactic extinction E(B-V): 0.03:
Tmid-T0 | mag (AB) | filter |
------------------------------
2.36h |21.6 (U.L.)| sdssr |
This project has received funding from the European Union’s Horizon 2020 research and innovation programme under grant agreement No 101004719
- GCN Circular #38599
M. A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U.
Leicester), A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB),
E. Ambrosi (INAF-IASFPA) , M. Capalbi (INAF-IASFPA), S. Dichiara
(PSU), J.A. Kennea (PSU) and P.A. Evans (U. Leicester) report on
behalf of the Swift-XRT team:
Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 241217A. We searched for X-ray sources in 1.4 ks of Photon Counting (PC) mode data. The total exposure at the position of the afterglow (see below) is 1.4 ks, obtained between T0+2.2 ks and T0+7.6 ks.
An uncatalogued X-ray source is detected within the estimated 3-sigma SVOM/ECLAIRs error region (6.8 arcmin) and is above the RASS 3-sigma upper limit at this position and fading with 5.3 sigma significance, and is therefore likely the GRB afterglow. Using 1404 s of PC mode data and 1 UVOT image, we find an enhanced XRT position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 84.15110, -25.29680 which is equivalent to:
RA (J2000): 05h 36m 36.26s
Dec(J2000): -25d 17' 48.5"
with an uncertainty of 2.5 arcsec (radius, 90% confidence). This position is 1.7 arcmin from the SVOM/ECLAIRs position. The peak count rate is 36 (±6) ct s^-1 (0.3 - 10 keV).
- GCN Circular #38600
Y. L. Qiu, H. L. Li, L. P. Xin (NAOC), D. B. Malesani (DAWN/NBI and Radboud Univ.), S. D. Vergani (Obs.Paris), J. T. Palmerio (CEA), M. Brunet (IRAP), D. Turpin (CEA),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 (NAOC), J. Zhang, L. J. Dan, G. Y. Zou, C. J. Wang, Y. F. Du, C. Huang (XIOPM), H. Zhou (PMO)，R. Z. Li (YNAO)
report on behalf of the SVOM team:
GRB 241217A (Brunet et al., GCN circular 38594) was observed by on-board SVOM/VT after the automatic slew of the satellite. The VT conducted observations in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously.
With the downlinked X band data an uncatalogued optical source was detected in stacked images in both VT_B and VT_R bands within the error box of SVOM/ECLAIRs (6.8 arcmin radius at 90% C.L.), SVOM/MXT (25 arcsec radius at 90% C.L.), compared to the DESI Dr10 catalog.
The source is located at RA, Dec = 84.1513626, -25.2970374, which is equivalent to:
RA (J2000) : 05:36:36.327
Dec (J2000): -25:17:49.33
with an uncertainty of 0.5 arcsec.
This source overlaps a faint extended source visible in archival DESI images of the field.
This position is consistent with the X-ray counterpart position of Swift/XRT reported by Williams et al. (GCN 38599).
The light curve of the counterpart in VT_R decayed from 240 s to 500 s after the burst and then a re-brightening occurred with a maximum at around 1000 s and then re-decayed. The magnitude was VT_B=22.4, VT_R=21.4 mag in AB magnitude about 300 seconds after the trigger.
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 #38602
R.-Z. Li, B.-T. Wang, F.-F. Song, J. Mao, H.-C. Feng and J.-M. Bai (YNAO, CAS) report:
We observed the field of GRB 241217A (Marius et al., GCN 38594, T0 at 2024-12-17T16:57:13) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2024-12-17T17:30:55, about 0.56 hours after the trigger.
No new uncataloged optical source was detected within the SVOM/VT error circle (GCN 38600).
The preliminary analysis results are shown as follows:
+----------------+------------+----------+----------------+
| Tmid-T0 [hr] | Exp. [s] | Filter | 5-sigma U.L. |
+================+============+==========+================+
| 0.65 | 600 | r | 20.6 |
+----------------+------------+----------+----------------+
The given magnitudes are derived based on calibrating against Pan-STARRS1 field stars.
- GCN Circular #38606
TITLE: GCN CIRCULAR
NUMBER: 38606
SUBJECT: EP241217b/GRB 241217A: EP detection of the prompt X-ray emssion
DATE: 24/12/18 06:20:25 GMT
FROM: EP Team at NAOC/CAS
EP241217b/GRB 241217A: EP detection of the prompt X-ray emssion
H. Zhou (PMO, CAS), S.-F. Zhu (USTC), M. H. Zhang (NAO, CAS), C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team:
We report on the detection of an X-ray transient by the Einstein Probe (EP), designated as EP241217b (Trigger ID: 01709129080).
About 10 seconds after the trigger of GRB 241217A (GCN 38594), the Einstein Probe (EP) began to observe the scheduled field which happened to cover GRB 241217A. EP241217b triggered the on-board processing unit of the Wide-field X-ray Telescope (WXT) at 2024-12-17T16:58:04.349 (UTC), i.e., about 53 seconds after the trigger of GRB 241217A. The WXT position of the X-ray source is R.A. = 84.167 deg, Dec. = -25.281 deg, with an uncertainty of 2.8 arcmin (90%).
About 134 seconds after the trigger of the GRB, the Follow-up X-ray Telescope (FXT) onborad EP performed an autonomous follow-up observation, and found an uncatalogued X-ray source, located at R.A., Dec. = 84.1499, -25.3003 deg with an uncertainty of about 20 arcsec (90%). The FXT position is consistent with the X-ray/optical afterglow positions of GRB 241217A (GCN 38594, 38599, 38600).
EP241217b was detected by the WXT at the begining of the scheduled observation, i.e., 10 seconds after the GRB trigger. The WXT light curve (including the follow-up observation) clearly shows 2 pulses seperated in time. The first one lasts from 10 to 620s, and it is composed of two short pulses peaked at 150s and 260s, respectively (from 53 to 134 seconds, EP was slewing, the possiblity there could be other pulses in this period can not be ruled out). The second one lasts from 1000 to 1500s. The similar temporal behavior is also seen in the FXT light curve.
The time averaged WXT spectrum (about 134 to 2000 seconds after the trigger of the GRB) was fitted by an absorbed powerlaw model with the fixed Milky Way equivalent hydrogen column density of 1.79 x 10^20 cm^-2 and an intrinsic absorber assuming the redshift of the absorper is 1.195 (the Legacy Survey dr9 photo-z of the extended source overlayed with EP241217b/GRB 241217A). The best fitted model shows the equivalent hydrogen column density of the intrinsic absorption is 1.42(-0.46, +0.51) x 10^22 cm^-2, the spectral index is 1.57(-0.21, +0.22) and the unabsorbed 0.5-4 keV flux is (1.19+/-0.10) x 10^-9 erg/s/cm^2.
The FXT-A spectrum (about 134 to 7800 seconds after the triger of the GRB) is extracted with an annular region to mitigate the potential pile-up effect. The FXT spectrum is then fitted using the same model as the WXT spectrum. The best-fit intrinsic nH is 0.85(+/-0.06) x 10 ^ 22 cm^-2, with a power-law photon index of 1.58(+/-0.04). The unabsorbed 0.5-10 keV flux is measured at 1.1 x 10 ^-9 erg/s/cm^2.
A further FXT follow-up observation has been arranged.
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 #38609
V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko,
A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, 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. 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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP241217b ( EP Team et al., GCN 38606) errorbox 313 sec after notice time and 48497 sec after trigger time at 2024-12-18 06:26:21 UT, with upper limit up to 19.7 mag. The observations began at zenith distance = 28 deg. The sun altitude is -29.0 deg.
The galactic latitude b = -26 deg., longitude l = 229 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2713458
We obtain a following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
_________|_____________________|_____________________|____________________________________|_____|_______|_______|________
48527 | 2024-12-18 06:26:21 | MASTER-OAFA | (05h 36m 52.07s , -25d 04m 22.7s) | C | 60 | 19.7 |
Filter C is a clear (unfiltred) band.
The observation and reduction will continue.
The message may be cited.
- GCN Circular #38616
A. Bochenek and D. A. Perley (LJMU) report:
We observed the field of GRB 241217a (Marius et al., GCN 38594) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 4x200s exposures with the SDSS r’ and SDSS i’ filters starting at 2024-18-09 01:09:11 UT, approximately 8.2 hours after the trigger.
We do not detect any new sources at the Swift/XRT afterglow position (Williams et al. GCN 38599) nor within the SVOM/VT error circle (Qiu et al. GCN 38600). The 3-sigma limiting magnitudes on the stacked images are r > 21.7 mag and i > 22.0 mag. The photometry was obtained using nearby PanSTARRS secondary standards and was not corrected for extinction.
- GCN Circular #38619
M. Ferro, R. Brivio, P. D’Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of GRB 241217A detected by SVOM (Brunet et al., GCN 38594), also detected by Swift-XRT (Williams et al., GCN 38599) and EP-WXT (Zhou et al., GCN 38606) with the REM 60cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, K bands, starting on 2024 December 18 at 03:02:28 UT (i.e. 10.1 hours after the SVOM trigger), and lasting for about 1.5 hour.
From preliminary photometry we do not detect any optical or NIR counterpart at the XRT position down to the following 3sigma magnitude upper limits:
r > 20.9 (AB; calibrated against the Pan-STARRS catalogue)
at a mid-time of t - t0 = 10.9 hr after the trigger,
H > 16.6 (Vega; calibrated against the 2MASS catalogue)
at a mid-time of t - t0 = 10.8 hr after the trigger.
- GCN Circular #38621
Z.P. Zhu, X. Liu, D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud Univ.), A. Amanda Djupvik (NOT), Laura Cotter, Antonio Martin-Carrillo (UCD), Jesse Palmerio (CEA/Irfu) and Susanna D. Vergani (GEPI / Obs. de Paris) report on behalf of a large collaboration:
We observed the field of GRB 241217A / EP241217b detected by SVOM (Marius et al., GCN 38594) and Einstein Probe (Zhou et al., GCN 37492), using the StanCam and NOTCam instruments mounted on the Nordic Optical Telescope (NOT), with 9x200s in the SDSS-z band and 18x60 s photometry in the J band. Observations started at 23:09:34 UT on 2024-12-17, i.e. 6.2 hr after the trigger.
The optical afterglow (Qiu et al., GCN 38600) is not detected in any of the stacked images, down to the following 5-sigma upper limits:
T_mid (UT) | T_mid (hr) | filter | Exposue|5-sigma U.L. (AB)
2024-12-17T23:20:59 | 6.396 | J | 18x60s | 19.5
2024-12-18T01:05:01 | 8.130 | z | 9x200s | 21.3
calibrated with nearby Pan-STARRS and 2MASS stars, and not accounting for any Galactic extinction correction.
- GCN Circular #38622
D. Götz, H. Goto, P. Ferrando, A. Meuris, M. Moita, C. Plasse, A. Sauvageon (CEA),
P. Maggi, L. Michel (ObAS), C. van Hove, F. Robinet, N. Leroy (IJCLab), A. Fort, J. Joubert, K. Mercier, S. Crepaldi (CNES) on behalf of the MXT Commissioning Team,
SVOM JSWG: Jian-Yan Wei (NAOC), Bertrand Cordier (CEA), Shuang-Nan Zhang (IHEP), Stéphane Basa (LAM), Olivier Godet (IRAP), Arnaud Claret (CEA), Zi-Gao Dai (USTC), Frédéric Daigne (IAP), Jin-Song Deng (NAOC), 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), Shaolin Xiong (IHEP), Bing Zhang (UNLV),
M. Brunet (IRAP)
report on behalf of the SVOM team:
GRB 241217A (Brunet et al. GCN 38594, Zhou et al. GCN 38606) was observed by SVOM/MXT after an automatic SVOM slew starting at 17:01:09 UT for 12.8 ks (3.5 hr) after the slew. Its position measured with the full MXT dataset is consistent with the one reported by SVOM/VT (Qiu et al. GCN 38600) and Swift/XRT (Williams et al. GCN 38599).
After an initial decrease lasting about 300 s, possibly related to the end of the prompt emission, the X-ray light curve enters a bright long lasting emission phase (average 0.5-10 keV flux 8.5e-10 erg/cm2/s) with a superimposed flaring activity up to the end of the observation. If the initial decay is indeed related to the prompt emission, the duration of the GRB would be about 550 s (assuming the trigger time of 16:57:13 UTC, GCN 38594).
If we consider the X-ray long lasting emission being part of the prompt emission, GRB 241217A would qualify as an ultra-long GRB, as also suggested by the EP/WXT light curve (Zhou et al. GCN 38606), or potentially as a jetted TDE. Further X-ray observations are planned.
The average spectrum of the X-ray emission can be well fit by an absorbed single power law model with a power law photon index of 1.38+/-0.05 and an NH value of 0.12+/-0.01 x 1e22 /cm2.
Follow-up observations at other wavelengths are encouraged.
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. MXT was developed jointly by CEA, CNES, University of Leicester, IJCLab and MPE.
The SVOM point of contact for this burst is: Brunet Marius (marius.brunet@irap.omp.eu)
- GCN Circular #38623
Z.P. Zhu, X. Liu, S.Y. Fu, J. An, S.Q. Jiang, D. Xu (NAOC), X. Gao (Urumqi No.1 Senior High School), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 241217A/EP241217b detected by SVOM (Marius et al., GCN 38594) and Einstein Probe (Zhou et al., GCN 37492), using the HMT-0.5m telescope located at Nanshan, Xinjiang, China. Observations started at 17:18:54 UT on 2024-12-17, i.e. 21.7 mins after the trigger.
The reported optical afterglow (Qiu et al., GCN 38600) is not detected in our stacked image, down to a 5-sigma limiting magnitude of ~ 18.5 mag (AB) at 0.84 hr post-burst, calibrated against G-band of Gaia DR3 and not corrected for Galactic extinction.
- GCN Circular #38625
M. E. Ravasio (Radboud Univ.), P. Veres (UAH), R. Hamburg (USRA), E. Burns (LSU) and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team:
Fermi-GBM had full spatial and temporal coverage of the transient GRB 241217A/EP241217B detected by SVOM and EP (GCN 38594; GCN 38606). There was no Fermi-GBM onboard trigger around the SVOM trigger time T0=2024-12-17T16:57:13 UTC or the EP trigger time at T0+53 s (16:58:04 UTC). Fermi-GBM had exited SAA approximately 7 mins before T0, and given the rapidly decreasing background, on-board triggering was difficult during this time.
The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals in GBM identified a transient most significantly at T0+156 s (16:59:48 UTC) on a 32 s timescale with a false alarm rate of 6.5e-05 Hz. The localization is consistent with the SVOM and EP locations. The transient was best-fit with a "soft" spectrum (i.e., a Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB.
The full GBM light curve consists of multiple peaks and the time-averaged spectrum from T0-44 s (16:56:29 UTC) to T0+190 s (17:00:23 UTC) is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.68 +/- 0.21 and the cutoff energy, parameterized as Epeak, is 36 +/- 2 keV. The event fluence (10-1000 keV) in this time interval is (1.24 +/- 0.05)E-05 erg/cm^2.
The spectral analysis results presented above are preliminary.
[1] Goldstein et al. 2019 arXiv:1903.12597
- GCN Circular #38628
T. Hussenot-Desenonges (IJCLAB), F.Colas (Obs-Paris), L. De Almeida, W. Corradi, N. Sasaki, F. Navarete (LNA), H. Peng (THU), H. Lau Jun Xian (Tsinghua Univ.), S. Antier (OCA), C. Andrade (UMN), S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), A. Klotz (IRAP), D. Turpin (CEA-Saclay/Irfu) on behalf of the GRANDMA collaboration:
We observed the field of GRB 241217A / EP241217B, detected by SVOM/ECLAIRs (GCN 38594) and Einstein Probe (GCN 38606), using T1MPicduMidi, starting 5 hours after T0.
We obtain the following optical 5-sigma upperlimit at the SVOM/VT position (GCN 38600):
| Tstart (UTC) | Telescope | Exposure | Filter | Magnitude |
| 2024-12-17T22:09:50 | T1MPicduMidi | 126x60s | r | >21.46 (AB) |
We also do not detect any uncatalogued sources within the SVOM/ECLAIRs error region, down to a 5-sigma upper limit of r > 21.35 (AB).
All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022), and calibrated with the Pan-STARRS DR1 catalogue.
GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518).
- GCN Circular #38635
Xiangkun Liu, Yu Pan, Dezi Liu, Brajesh Kumar, Xianao Wang, Chenxi Shang, Xufeng Zhu, Xingzhu Zou, Xinlei Chen, Yuanpei Yang, Yehao Cheng, Tao Wang, Guowang Du, Yuan Fang, Jinghua Zhang (all SWIFAR, YNU), Xuhui Han, Pinpin Zhang, Liping Xin, Chao Wu (all NAOC), Xiaowei Liu (SWIFAR, YNU) report on behalf of the Mephisto Team:
The field of GRB 241217A/EP241217B detected by SVOM/ECLAIRs (GCN 38594) and Einstein Probe (GCN 38606) 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 17:09:14 2024/12/17 UT (~12 min after the SVOM/ECLAIRs trigger) and multiple frames with different exposure times were taken. We do not detect any uncatalogued sources in the stacked images within the SVOM/ECLAIRs error region and the 3 sigma upper limits are below.
UT start band Exp LimMag (AB)
2024/12/17/T17:09:14 u 300s*3 >21.6
2024/12/17/T17:09:14 g 300s*2, 50s*3 >21.6
2024/12/17/T17:09:14 i 300s*2, 79s*2 >20.6
2024/12/17/T17:13:48 v 300s*3 >21.0
2024/12/17/T17:13:48 r 300s*2, 50s*3 >21.6
2024/12/17/T17:13:48 z 300s*2, 79s*2 >20.3
-------------------------------------------------------------------------------------------------
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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- GCN Circular #38637
B. Schneider (LAM), D. B. Malesani (DAWN/NBI and Radboud Univ.), J. T. Palmerio (CEA/Irfu), A. Saccardi (CEA/Irfu), S. D. Vergani (GEPI/Obs. de Paris), Z. P. Zhu (NAOC), D. Xu (NAOC), G. Pugliese (UvA), J. P. U. Fynbo (DAWN/NBI), L. Izzo (INAF-OACn and DARK/NBI), A. Martin-Carrillo (UCD), N. R. Tanvir (U. Leicester), A. J. Levan (Radboud Univ. and Warwick Univ.), A. Rossi (INAF-OAS), S. Savaglio (Univ. Calabria) report on behalf of the Stargate collaboration:
We observed the optical afterglow (Qiu et al., GCN 38600) of the SVOM GRB 241217A / EP241217b (Brunet et al., GCN 38594; William et al., GCN 38599; Zhou et al., GCN 38606) with the X-shooter spectrograph mounted on the ESO VLT UT3 (Melipal). The observation consisted of 4x1200 s with a mid-time at 2024-12-18 06:52.46 UT (13.93 hr after the trigger).
In images taken with the acquisition camera, the counterpart is detected with AB magnitude r = 23.44 +/- 0.11 (mid time 13.1 hr after the trigger), which is about 1 mag brighter than the archival value from the Legacy Survey (r = 24.35 +/- 0.14). The target contained thus a mix of both afterglow and host galaxy light.
From a preliminary reduction of the spectra, a faint continuum is detected in the NIR arm from 10500 to 18000 AA, likely due to the afterglow. A single emission line is very significantly detected in the near-infrared arm at 14410 AA. We note that this wavelength region is severely affected by telluric absorption, whose effect could slightly shift the observed line centroid. No other strong lines are confidently detected.
The likely interpretation is that the emission line is from [O III] 5007 AA at z = 1.879. At this redshift, other commonly observed emission lines, Halpha, Hbeta and [O III] 4959 all fall in regions of strong telluric absorption. A marginal detection of an emission line at 18990 AA is consistent with Halpha strongly attenuated by telluric absorption at this redshift. A low-significance emission feature can also be seen corresponding to [O II] 3729.
An alternative scenario would be that the emission line is due to Halpha at z = 1.196. In this case, we would expect to detect [O III] 5007 around 11000 AA, a region free from telluric absorption. Significant dust extinction must be invoked to suppress it and the other nebular lines.
The photometric redshift determination of the extended object visible in the Legacy Survey (z = 1.20 +/- 0.48; Zhou et al. 2021, MNRAS, 501, 3309) does not allow to strongly discriminate between the two values. We also warn that for such a faint object the Legacy Survey photometric redshifts are prone to systematic errors.
Even if the detection of a single line is ambiguous for redshift determination, we view the option z = 1.879 as the more likely scenario and we propose it as being the redshift of GRB 241217A / EP241217b. Further analysis is ongoing, and we will update the community should this reveal a stronger conclusion regarding the burst redshift.
We acknowledge the expert support from the ESO observing staff at Paranal, in particular Jesus Corral-Santana.
- GCN Circular #38642
J. Freeburn (Swinburne/OzGrav), I. Andreoni (UNC), J. Carney (UNC)
We observed the optical counterpart (Qiu et al., GCN 38600) to SVOM GRB 241217A / EP241217b (Brunet et al., GCN 38594; William et al., GCN 38599; Zhou et al., GCN 38606), with the Goodman High Throughput Spectrograph mounted on the SOAR telescope in imaging mode. We took six 300s exposures in r-band between 2024-12-19T04:23:12 and 2024-12-19T04:54:57 UTC.
We detect the optical counterpart associated with GRB 241217A / EP241217b. With difference imaging using a template from the Dark Energy Survey (Abbott et al., 2021, ApJ, 255, 20) and photometric calibration using the Pan-STARRS1 catalogue, we measure r = 24.28 +/- 0.26 AB magnitude.
While this is a low significance result, our measurement agrees with the photometry reported in Schneider et al. (GCN 38637). Measuring from the science and template images respectively, we obtain 23.41 +/- 0.14 and 24.49 +/- 0.18 AB magnitude respectively. These measurements are consistent with the results of GCN 38637 and the Legacy Survey catalog measurement.
- GCN Circular #38649
Tao An, Yuanqi Liu (Shanghai Astronomical Observatory, China), Jinjun Geng, Xuefeng Wu (Purple Mountain Observatory, China) report on behalf of the EP radio follow-up team:
GRB241217A/EP241217b was initially discovered and reported by the SVOM team (Marius et al. GCN 38594), followed by EP detection post-trigger (Zhou et al. GCN 38606). In response to the optical counterpart detections (Qiu et al., GCN 38600; Schneider et al. GCN 38637), we conducted radio follow-up observations using the Australia Telescope Compact Array (ATCA).
We observed the SVOM/VT-reported position [RA(J2000) = 05:36:36.327, Dec(J2000) = -25:17:49.33] during two epochs: UTC 13:00-18:00 on December 20, 2024, and UTC 14:00-18:30 on December 21, 2024. In the images made using natural weighting, no significant emission was detected at either 5.5 GHz or 9 GHz, with 3σ upper limits of 27 μJy and 24 μJy, respectively.
We thank the ATCA team for their rapid scheduling and excellent support.
- GCN Circular #38676
J. Freeburn (Swinburne/OzGrav), I. Andreoni (UNC)
We observed the location of the optical counterpart (Qiu et al., GCN 38600) to SVOM GRB 241217A / EP241217b (Brunet et al., GCN 38594; William et al., GCN 38599; Zhou et al., GCN 38606), with the Goodman High Throughput Spectrograph mounted on the SOAR telescope in imaging mode. We took six 300s exposures in r-band between 2024-12-24T04:43:11 and 2024-12-24T05:14:22 UTC.
With difference imaging using a template from the Dark Energy Survey (Abbott et al., 2021, ApJ, 255, 20) and photometric calibration using the Pan-STARRS1 catalogue, we do not detect the optical counterpart and place an upper limit of r > 24.5 AB magnitude.
- GCN Circular #38750
Tao An, Yuanqi Liu (Shanghai Astronomical Observatory, China), Jinjun Geng, Xuefeng Wu (Purple Mountain Observatory, China) report on behalf of the EP radio follow-up team:
We report continued radio follow-up observations of GRB 241217A/EP241217b (Marius et al. GCN 38594; Zhou et al. GCN 38606) with the Australia Telescope Compact Array (ATCA), following our initial observations (GCN 38649).
In our subsequent observation on December 24 (UT14:00-18:30), we detect significant radio emission (>6σ) at both 5.5 GHz and 9 GHz frequencies. After careful reanalysis of our first epoch data (December 20 UT13:00-18:00), we detect a 5σ radio source at 5.5 GHz, while the 9 GHz band shows no significant detection.
Further ATCA observations are scheduled to monitor the temporal and spectral evolution of this source.
We thank the CSIRO Space and Astronomy staff, in particular Jamie Stevens, for supporting these observations in a timely manner. We acknowledge the Gomeroi people as the traditional owners of the Observatory site. The Australia Telescope Compact Array is part of the Australia Telescope National Facility which is funded by the Australian Government for operation as a National Facility managed by CSIRO.
- GCN Circular #38966
S. Giarratana (INAF-OAB), M. Giroletti (INAF-IRA),
G. Ghirlanda (INAF-OAB), N. Di Lalla (Stanford Univ.),
N. Omodei (Stanford Univ.), O. S. Salafia (INAF-OAB)
At 07:53:14 UT on 2024 Dec 22 (T_mid = 4.65 days post-burst)
the Karl G. Jansky VLA observed the field of GRB 241217A /
EP241217B (Brunet et al., GCN 38594; Williams et al., GCN 38599;
Zhou et al., GCN 38606; Ravasio et al., GCN 38625) in three bands,
with central frequencies of 6, 10 and 15 GHz.
The standard 3C147 was used as bandpass and flux density
calibrator, while J0530-2503 was used as phase calibrator.
From a preliminary analysis, an unresolved radio source
is tentatively detected at a position (J2000):
RA: 05:36:36.321 +- 0.003
Dec: -25:17:49.39 +- 0.04
consistent with the X-ray (Williams et al., GCN 38599), optical
(Qiu et al., GCN 38600; Freeburn et al., GCN 38642), and radio
(An et al., GCN 38750) position of the transient.
The preliminary analysis yields the following results:
================================================================
T_mid Freq Peak r.m.s. Beam PA
[days] [GHz] [uJy/b] [uJy/b] [arcsec^2] [deg]
================================================================
4.65 6 32 7 0.77x0.28 26
4.65 10 36 8 0.51x0.18 32
4.65 15 38 7 0.30x0.11 24
================================================================
No source is detected with a >3sigma confidence at the
aforementioned position in previous radio surveys (NVSS,
VLASS, RACS), all of which have r.m.s. noise levels above
100 uJy/b.
We would like to thank the staff of the VLA for approving, executing,
and processing the observations.
The National Radio Astronomy Observatory is a facility of the National
Science Foundation operated under cooperative agreement by Associated
Universities, Inc.
These observations were carried out as part of project SF171028,
approved in the framework of the Fermi - NRAO joint program agreement.
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