- GCN Circular #40168
B.-T. Wang (YNAO, CAS), Y.H. Cheng (SWIFAR,YNU), W. J. Xie, D. H. ZHAO (NAO, CAS), C. W. WANG (IHEP) on behalf of the SVOM mission team.
At 2025-04-19T02:29:32 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250419A (SVOM burst-id sb25041901).
The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 5 alerts. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 8.62 in the [5-8] keV energy band over a time window of 20.40 seconds starting at Tb.
The localization of the best alert is R.A., Dec 202.387, 7.086 degrees:
RA (J2000) = 13h29m32.97s
Dec (J2000) = 7d05m09.92s
with a 90% C.L. radius of 9.15 arcmin (including systematic error of 2 arcmin added in quadrature).
SVOM slewed to the burst.
No prompt X-ray observation could be performed by MXT.
VT began observing the field after the slew. The analysis of the recorded images will be published in a future circular gathering information on the follow-up of the SVOM optical instruments.
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.
The Burst Advocate (BA) on shift for this burst is Boting Wang: wangbaiting@ynao.ac.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
- GCN Circular #40169
Kin Ocelotl López (UNAM), Alan Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and B.-T. Wang (YNAO, CAS) report:
We imaged the field of the SVOM GRB 250419A (Wang et al., GCN Circ. 40168) with the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico on the night of 2025-04-19 UTC.
We observed from 2025-04-19 03:04 to 03:07 (35 to 38 minutes after the trigger) and obtained 3 minutes of exposure in the i filter. The data were coadded with the COLIBRÍ pipeline and analysed in STDWeb/STDPipe (Karpov 2025), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
We detect an uncataloged source at RA, Dec = 202.40535, 7.04108 degrees (J2000) with a magnitude of
i = 17.87 +/- 0.01
We suggest this is the optical counterpart of the GRB.
Further observations and analysis are ongoing.
We warmly thank the COLIBRÍ and DDRAGO engineering teams and the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir.
- GCN Circular #40170
L. P. Xin, Y. L. Qiu, C. Wu, H. L. Li., Z. H. Yao, Y. N. Ma, X. H. Han, H. B. Cai,J.Y. Wei (NAOC), J. T. Palmerio (CEA), B.-T. Wang (YNAO, CAS), Y.H. Cheng (SWIFAR,YNU), W. J. Xie(NAOC), report on behalf of SVOM/VT team:
After the trigger by SVOM/ECLAIRs at 2025-04-19T02:29:32 UTC (Tb), SVOM performed an automatic slew on the burst. SVOM/VT began observing the field at 45.26 min after the SVOM trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
An uncatalogued and bright source, compared to DESI catalog, is found by automatic ground pipeline based on VHF data within the error box of SVOM/ECLAIRs (Wang et al. GCN 40168) at ra=202.40533, dec=7.04106 (J2000), corresponding to:
RA (J2000) = 13:29:37.28
Dec (J2000) = +07:02:27.8
with an uncertainty of 0.5 arcsec.
The source is detected in both VT_R and VT_B in the third VT observing sequence, the magnitudes are given below:
MidTime min | exposure time (s) | mag(AB) | mag err | band
47.767 | 6x50 | 17.790| 0.02 | VT_R
47.767 | 6x50 | 18.220| 0.01 | VT_B
The position and the brightness are consistent with the report (López et al., GCN 40169).
Given the VT color of the counterpart, it might be a low redshift gamma-ray 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.
- GCN Circular #40171
WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and
Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team:
The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at
Lick Observatory, observed the field of SVOM GRB 250403A (Wang
et al., GCN 40168) with a set of clear (roughly R) images starting
at 1.47 hours after the trigger. We clearly detected the optical
afterglow (López et al., GCN 40169; Xin et al., GCN 40170) in our
single image. The afterglow is measured at 18.0 +/- 0.2 mag (Vega)
at 1.47 hours after the trigger. It remained to be similar brightness
for about 40 minutes then decayed after that. Observation is on
going.
- GCN Circular #40172
A. Kumar, G. Ramsay, B. P. Gompertz, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. O'Neill, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration:
We report on observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the SVOM GRB 250419A (sb25041901; Wang et al., GCN 40168). The observations were conducted with GOTO-North between 2025-04-19 02:55:03 (25.5 min post-trigger) and 2025-04-19 04:03:07 (93.6 min post-trigger). Each observation 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.
We detect the reported optical afterglow, discovered by SVOM/COLIBRÍ FM-GFT (López et al., GCN 40169) and confirmed by SVOM/VT (Xin et al., GCN 40170), and KAIT (Zheng et al., GCN 40171). We obtained the following 3-sigma detections of the optical counterpart:
Date | T-T0 (min) | Filter | Mag (AB)
---------------------------------------------------------------------------
2025-04-19T02:55:03 | 25.5 | L | 18.22 ± 0.05
2025-04-19T04:03:07 | 93.6 | L | 18.39 ± 0.07
Based on our observations, the afterglow exhibits a power-law decay with an index of α = -0.12 between these two epochs.
We find no evidence of the source prior to the GRB trigger time in archival GOTO observations taken 14.07 min before the trigger, down to a 3-sigma L-band upper limit of 20.26 mag.
Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction.
Observations are ongoing.
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 #40173
K.L. Page (U. Leicester), B. Sbarufatti (INAF-OAB), C. Salvaggio
(INAF-OAB), M. Ferro (INAF-OAB), S. Dichiara (PSU), J.A. Kennea (PSU),
D.N. Burrows (PSU), A.P. Beardmore (U. Leicester) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
We have analysed 2.0 ks of XRT data for the SVOM/ECLAIRs-detected burst
GRB 250419A (SVOM burst-id sb25041901), from 3.8 ks to 9.6 ks after the
SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC)
mode. The light curve is consistent with a constant source of mean
count rate 1.1e-01 ct/sec. A power-law fit gives an index of 0.3 (+0.6,
-0.5). Despite a constant count rate, we are likely detecting the GRB
afterglow. The source is consistent with the position of the optical
afterglow detected by the SVOM/COLIBRÍ (FM-GFT) telescope (Lopez et
al., GCN 40169), SVOM/VT (Xin et al., GCN 40170), KAIT (Zheng et al.,
GCN 40171), GOTO (Kumar et al., GCN 40172).
A spectrum formed from the PC mode data can be fitted with an absorbed
power-law with a photon spectral index of 1.9 (+0.4, -0.3). The
best-fitting absorption column is 7.7 (+9.9, -5.5) x 10^20 cm^-2,
consistent with the Galactic value of 2.2 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 (4.1 x
10^-11) erg cm^-2 count^-1.
A summary of the PC-mode spectrum is thus:
Total column: 7.7 (+9.9, -5.5) x 10^20 cm^-2
Galactic foreground: 2.2 x 10^20 cm^-2
Excess significance: <1.6 sigma
Photon index: 1.9 (+0.4, -0.3)
The results of the XRT-team automatic analysis are available at
http://www.swift.ac.uk/xrt_products/00019724.
This circular is an official product of the Swift-XRT team.
- GCN Circular #40174
A. L. Thakur (INAF-IAPS), M. Garnichey (LUX-Paris Obs.), G. Corcoran (UCD), A. J. Levan (Radboud), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), G. Pugliese (API-UvA), A. Saccardi (CEA/Irfu), S. D. Vergani (LUX-Paris Obs.) report on behalf of the Stargate collaboration:
We observed the optical counterpart (Lopez et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172) of the SVOM/ECLAIRs GRB 250419A (Wang et al., GCN 40168) using the ESO/VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Observations started on 2025 April 19 at 07:10:59 UT (4.69 hr after the burst). Our spectra cover the wavelength range 3000-21000 AA and consist of 4 exposures of 600 s each. Seeing conditions were very poor at ~3".
In a preliminary reduction of the spectra, we clearly detect a continuum over the entire wavelength range. From the detection of multiple absorption features, including Fe II, Mg II, Mg I, Ca II and Ca I we infer a redshift of z = 0.845.
We note that no object is visible in the Legacy Survey at the coordinates of the optical transient (López et al., GCN 40169; Xin et al., GCN 40170), down to a magnitude r ~ 24. This is consistent with the lack of emission lines in our spectrum.
We acknowledge the prompt response and excellent support of the ESO observing staff in Paranal, particularly from Martina Baratella. This analysis was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495).
- GCN Circular #40176
K.L. Page, P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report on
behalf of the Swift-XRT team:
The XRT afterglow of the SVOM/ECLAIRs-detected burst GRB 250419A, reported
in GCN Circ. 40173, is located at a position of RA, Dec = 202.40554,
7.03987 which is equivalent to
RA (J2000): 13h 29m 37.33s
Dec (J2000): +07d 02' 23.5"
with an uncertainty of 3.8 arcsec (radius, 90% confidence).
This circular is an official product of the Swift-XRT team.
- GCN Circular #40179
V.Lipunov, A.Kuznetsov, G.Antipov, V.Topolev, K.Zhirkov, N.Tyurina, P.Balanutsa, A.Chasovnikov,
Ya.Kechin, V.Senik, K. Labzina, D.Vlasenko, E.Gorboskoy(Lomonosov MSU),
O.Gress, N.Budnev (ISU),
C.Francile, F. Podesta, R.Podesta, E. Gonzalez (OAFA),
A.Sosnovskij (Crao RAS),
A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory),
A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity),
R.Rebolo (The Instituto de Astrofisica de Canarias),
D.Buckley (SAAO),
L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro AstrophysicsObservatory)
MASTER-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru,Lipunov et al., 2010, Advances in Astronomy, v. 2010, 30L)
located in Argentina (OAFA observatory of San Juan National University)
was pointed to the SVOM Alert 250419.10 (trigger No 1745029772,13h 29m 32.88s , +07d 05m 09.6s, R=0.1525, Wang et al. GCN 40168, Ocelotl López et al. GCN40169, Xin etl al. GCN40170)
3960 sec after trigger time at 2025-04-19 03:35:32 UT, with upper limit up to 19.9 mag.
The observations began at zenith distance = 39 deg. The sun altitude is -66.0 deg.
The galactic latitude b = 68 deg., longitude l = 330 deg.
Real time updated cover map and OT discovered available here:
https://master.sai.msu.ru/site/master2/observ.php?id=2847195
We obtained the following upper limits.
Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment
3991 | 2025-04-19 03:35:32 | MASTER-OAFA | (13h 29m 02.64s , +07d 04m 50.6s) | C | 60 | 19.7 |
5446 | 2025-04-19 03:59:47 | MASTER-OAFA | (13h 28m 54.60s , +07d 03m 09.9s) | C | 60 | 19.7 |
6895 | 2025-04-19 04:23:56 | MASTER-OAFA | (13h 29m 35.13s , +07d 25m 23.4s) | C | 60 | 19.6 |
6955 | 2025-04-19 04:23:56 | MASTER-OAFA | (13h 29m 35.12s , +07d 25m 23.4s) | C | 180 | 19.9 | Coadd
8383 | 2025-04-19 04:48:45 | MASTER-OAFA | (13h 29m 28.53s , +07d 25m 00.4s) | C | 60 | 19.5 |
9666 | 2025-04-19 05:10:08 | MASTER-OAFA | (13h 29m 34.89s , +07d 26m 24.5s) | C | 60 | 19.4 |
10159 | 2025-04-19 05:18:20 | MASTER-OAFA | (13h 29m 31.07s , +07d 26m 26.7s) | C | 60 | 19.5 |
Filter C is a clear (unfiltred) band.
There is MASTER OT J132937.28+070227.8 since 2025-04-19 03:35:32 with m_OT=18.0 (unfiltered, Lipunov et al. 2010, 2019, 2022, 2023) up to 2025-04-19 05:18:20UT
at SVOM VT position (GCN 40170 Xin et al.)
The reduction will be continued
- GCN Circular #40180
Mohammad Odeh (Al-Khatim Observatory, AKO, operated by the International
Astronomical Center in Abu Dhabi, UAE), and Shaikha Alshamsi, and Nidhal
Guessoum (American University of Sharjah, UAE), report:
We observed the field of GRB 250419A detected by SVOM (Wang et al., GCN
40168), using our 0.36m f/7.7 robotic telescope. The observation session
began on 19 April 2025 at 15:49 UT and continued until 18:48 UT, with a
midpoint at 17:18 UT, approximately 14.8 hours after the trigger.
We obtained multiple 180-second exposures using the Ic filter. The optical
afterglow was clearly detected at:
R.A. (J2000): 13:29:37.30
Dec. (J2000): +07:02:27.7
Our detection is consistent with the results of (López et al., GCN 40169;
Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172;
Lipunov et al., GCN 40179).
The following observation was calculated using the Atlas catalogue as a
reference:
----------------------------------------------------------------------------
-
ObsTime (mid), Exposure (sec), Filter, Mag
----------------------------------------------------------------------------
-
2025-04-19T17:18:06Z, 57 x 180s (stacked), Ic, 18.7 +/- 0.16
----------------------------------------------------------------------------
-
The magnitude is not corrected for galactic extinction.
- GCN Circular #40181
D. A. Perley and A. Bochenek (LJMU) report:
We obtained imaging observations of the SVOM-detected GRB250419A (Wang et al., GCN 40168) with IO:O on the Liverpool Telescope on the night of 2025-04-19 between 22:02 and 22:26 UT. 6x100s exposures were acquired in both SDSS r-band and SDSS i-band. We clearly detect the optical counterpart (e.g. Ocelotl López et al., GCN 40169; Xin et al., GCN 40170) at the following magnitudes, calibrated using PanSTARRS secondary standards:
MJD dt filter mag +/- unc
60784.91810 0.814 r 19.96 +/- 0.06
60784.92664 0.822 i 19.76 +/- 0.06
- GCN Circular #40182
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP), R. Ya. Inasaridze (AbAO) report on behalf of IKI-GRB-FuN:
We observed the field of a soft long GRB 250419A detected by far by SVOM (Wang et al., GCN 40168), and Swift (Page et al., GCN 40111; Page et al., GCN 40176) at the redshhift of z = 0.845 (Thakur et al., GCN 40174) with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy), and the 0.7-meter AS-32 telescope of the Abastumani Astrophysical Observatory (AbAO). The R-band observations began on 2025-04-19 at 15:21:16 UT, i.e. ~0.55 days since trigger at Mondy. The optical counterpart (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181) is detected in the stacked image from both telescopes. The preliminary photometry is as follows:
Date UTstart Exptime t-T0 Filter OT Err UL Telescope
(s) (mid, days) (3sigma)
2025-04-19 15:21:16 21*120 0.55052 R 19.68 0.05 22.2 AZT-33IK
2025-04-19 17:15:36 76*60 0.64172 R 19.72 0.25 20.2 AS-32
Ref. stars
USNO-B1.0
RA Dec R2
202.4329 7.0165 15.18
202.3871 7.0378 16.79
The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes) and has not been corrected for the Galactic extinction
- GCN Circular #40183
I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL)
Following the detection of the Gamma-Ray Burst GRB 250419A by SVOM/ECLAIRs (Wang et al., GCN circ. 40168) and of the X-ray afterglow by Swift-XRT (Page et al., GCN circ. 40173), we observed the GRB field with the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Siding Spring Observatory (Australia) in the SDSS u, g, r, and i filters. The observations started at 2025-04-19 11:20:00 UTC, about 8.84 hours after the SVOM trigger, with simultaneous observations in the r and i filters followed by simultaneous observations in the u and g filters. An uncatalogued source is detected in the four filters at the position of the optical afterglow reported first by Ocelotl López et al. (GCN circ. 40169), that is consistent with the Swift-XRT position (Page et al., GCN circ. 40176) and with other optical detections reported by Xin et al. (GCN circ. 40170), Zheng et al. (GCN circ. 40171), Kumar et al. (GCN circ. 40172), Thakur et al. (GRB redshift of z = 0.845, GCN circ. 40174), Lipunov et al. (GCN circ. 40179), Odeh et al. (GCN circ. 40180), Perley and Bochenek (GCN circ. 40181), and Pankov et al. (GCN circ. 40182).
We measure the following magnitudes, calibrated against SDSS DR16 (Ahumada et al. 2020, ApJS, 249, 3A) stars, that are not corrected for Galactic extinction:
Date | UT start | mag | error | filter | exposure time (sec) |
------------------------------------------------------------------------
2025-04-19 11:20:00 19.15 0.07 i 300
2025-04-19 11:20:03 19.40 0.06 r 300
2025-04-19 11:45:15 20.13 0.17 u 300
2025-04-19 11:45:32 19.76 0.09 g 300
This work makes use of observations from the Las Cumbres Observatory global telescope network
(LCOGT observing programme IAC2025A-009, SGLF).
- GCN Circular #40185
Paul Kuin (MSSL/UCL) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began observations of the field of SVOM detected GRB
250419A/(SVOM burst-id sb25041901) 3790s after the SVOM ECLAIR
trigger at 2025-04-19T02:29:32 (Wang et al., GCN Circ. 40168).
A source consistent with the position reported by Kin Ocelotl López
et al. (Colibri - GCN Circ. 40169) and Liping Xin at al. (SVOM-VT
GCN Circ 40170), also reported by Weikang Zheng et al. (KAIT - GCN
Circ. 40171) and Amit Kumar et al. (GCN Circ. 40172) has been
detected in the initial UVOT exposures.
The detections using the UVOT photometric system (Breeveld et al.
2011, AIP Conf. Proc. 1358, 373) for the early exposures are:
Filter T_start(s) Exp(s) Mag (Vega)
u 3790 1667 17.73 +/- 0.04
u 9323 259 18.19 +/- 0.10
u 48658 1206 19.64 +/- 0.14
u 54296 1028 19.52 +/- 0.13
The magnitudes in the table are not corrected for the Galactic
extinction due to the reddening of E(B-V) = 0.085 in the direction
of the burst (Schlegel et al. 1998).
- GCN Circular #40186
GRB 250419A: SVOM/C-GFT optical observations
Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), B.-T. Wang (YNAO, CAS), Y.H. Cheng (SWIFAR,YNU) report on behalf of the SVOM/C-GFT team:
We observed the field of GRB 250419A detected by SVOM/ECLAIRs (sb25041901, Wang et al., GCN 40168) with C-GFT. Our observations were started on 2025-04-19T13:08:53 UTC, ~10.66 hr after the trigger.
The optical counterpart (reported by Ocelotl López et al. GCN 40169, Xin et al. GCN 40170, Zheng et al. GCN 40171, Kumar et al. GCN 40172, Lipunov et al. GCN 40179, Odeh et al. GCN circ. 40180, Perley and Bochenek GCN circ. 40181, Pankov et al. GCN 40182, and Pérez-Fournon et al. GCN 40183, Kuin et al. GCN 40185) was detected in the stacked g, r, and i-band images. The results are,
(T-T0)_mid(sec) exptime(s) mag mag_err band
-----------------------------------------------
46935 10x30s 19.38 0.17 r
47723 10x30s 19.25 0.21 i
49013 10x30s 19.98 0.22 g
The photometry was calibrated with nearby UCAC4 stars. Further analysis is on-going.
We thank the observation assistants Shuai Liu and Chunlei Guo 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 #40187
W. J. Xie, L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. Xu, Y. N. Ma, X. H. Han, P. P. Zhang, J. Wang, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA), B.-T. Wang (YNAO, CAS), Y.H. Cheng (SWIFAR,YNU) reported on behalf of SVOM/VT team:
Several ToO observations were performed by SVOM/VT for GRB 250419A (sb25041901, Wang et al., GCN 40168) in both VT_B (400nm-650nm) and VT_R (650nm-1000nm) band. The optical counterpart (Ocelotl López et al. GCN 40169, Xin et al. GCN 40170, Zheng et al. GCN 40171, Kumar et al. GCN 40172, Lipunov et al. GCN 40179, Odeh et al. GCN circ. 40180, Perley and Bochenek GCN circ. 40181, Pankov et al. GCN 40182, and Pérez-Fournon et al. GCN 40183, Kuin et al. GCN 40185, Wu et al. GCN 40186) was clearly detected in our observations.
The observations show that a re-brightening phase arise during 16.0 to 24.0 hours post the trigger, followed by a short-term plateau and then a decay later. The latest magnitude of the optical counterpart detected by SVOM/VT are:
MidTime (hours) | exposure time (s) | mag(AB) | mag err | band
48.133 | 28x60 | 20.388 | 0.08 | VT_R
48.103 | 26x60 | 20.924 | 0.07 | VT_B
More follow-ups are encouraged.
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.
- GCN Circular #40188
S.Q. Jiang (NAOC), S.Y. Fu (HUST), J. An, X. Liu, Z.P. Zhu, D. Xu (NAOC), J.Z. Liu (XAO) report on behalf of a large collaboration:
We observed the field of GRB 250419A detected by SVOM/ECLAIRs (Wang et al., GCN 40168), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:46:46.98 UT on 2025-04-20, i.e., 37.287 hr after the SVOM/ECLAIRs trigger, and a series of 600 s frames were obtained in the Sloan g-, r-, i- and z- bands.
The optical afterglow (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley et al., GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon GCN 40183; Kuin et al., GCN 40185; WU et al., GCN 40186; Xie et al., GCN 40187), which is consistent with the X-ray observed result (Page et al., GCN 40173 and GCN 40176), of GRB 250419A is clearly detected in our stacked images. Preliminary photometry results are as follows:
T_mid(hr) Filter Mag(AB) MagErr
38.707 g 20.83 0.04
39.552 r 20.47 0.03
40.396 i 20.20 0.04
41.156 z 20.04 0.07
calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction.
We acknowledge the excellent support from T.Q. Chen and Z.K. Feng for enabling these observations.
- GCN Circular #40189
Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES), Rahul Gupta (NASA GSFC) on behalf of a larger collaboration.
We observed the field of the GRB 250419A triggered by SVOM/ECLAIRs (Wang et al., GCN 40168) in V, r filters of the 1-meter Sinistro and B filter of 0.4 m SCICAM QHY600 telescopes at the Las Cumbres Observatory Global Telescope (LCOGT) node located at Siding Spring New South Wales, Australia. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel). The 0.4 m SCICAM QHY600 is equipped with 9576 x 6388 pixel CCD (FOV: 1.9 x 1.2 degrees, scale: 0.74 arcsec/pixel) but we only used the FOV of 30 x 30 arcmin for our observation.
Observations began on , starting from 2025-04-19T10:30:01.728 UT, 8.00 hours after the GRB trigger. Observation for later epochs are still going on.
We clearly detect the optical transient (OT) reported by GCNs (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley et al., GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon GCN 40183; Kuin et al., GCN 40185; WU et al., GCN 40186; Xie et al., GCN 40187, Jiang et al., GCN 40188) in our B, V, r band images.
|Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude|
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2025-04-19 10:30:01.728 8.00 1 x 600 V V = 19.50+/- 0.02
2025-04-19 10:41:55.392 8.21 1 x 600 r r = 19.35+/- 0.01
2025-04-19 14:57:03.744 12.46 2 x 450 B B = 20.51 +/- 0.11
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The field was calibrated against nearby APASS stars, with magnitudes converted using Lupton (2005) equations, and has not been corrected for Galactic extinction.
- GCN Circular #40190
A. Bochenek and D. A. Perley (LJMU) report:
We observed the SVOM-detected GRB250419a (Wang et al., GCN 40168) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 6x100s exposures in the SDSS r’ and i’ filters starting at 2025-04-20 21:43:22 UT, approximately 1.80 days after the trigger.
We report a detection in both bands at the position of the optical counterpart (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley et al., GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon GCN 40183; Kuin et al., GCN 40185; WU et al., GCN 40186; Xie et al., GCN 40187, Jiang et al., GCN 40188, Ghosh et al., GCN 40189). The obtained magnitudes are r = 20.61 ± 0.09 and i = 20.41 ± 0.08. The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction.
MJD (mid) T_mid-T_0 Filter Mag. (AB)
60785.90925 43.33 h r 20.61 ± 0.09
60785.91782 43.54 h i 20.41 ± 0.08
- GCN Circular #40202
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:
We continued observations of the field of GRB 250419A (Wang et al., GCN 40168; Page et al., GCN 40111; Page et al., GCN 40176) at the redshift of z = 0.845 (Thakur et al., GCN 40174) with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The R-band observations began on 2025-04-20 at 15:54:03 UT, i.e. ~1.58 days since trigger. The optical counterpart (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon et al., GCN 40183; Kuin, GCN 40185; Wu et al., GCN 40186; Xie et al., GCN 40187; Jiang et al., GCN 40188; Ghosh et al., GCN 40189; Bochenek & Perley, GCN 40190) is detected in the stacked image. The preliminary photometry is as follows:
Date UTstart Exptime t-T0 Filter OT Err UL
(s) (mid, days) (3sigma)
2025-04-20 15:54:03 45*120 1.58995 R 20.00 0.06 22.6
The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes, provided in Pankov et al., GCN 40182) and has not been corrected for the Galactic extinction.
- GCN Circular #40206
Gianluca Masi, Virtual Telescope Project (Italy), reports:
We observed the field of GRB 250419A (Wang et al., GCN 40168) with the 14” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-3200E based CCD camera.
We collected 3, 300-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 19 April, 21:07 UTC, that is about 18.6 hours after the burst.
We clearly detect the optical counterpart of GRB 250419A.
The position of the source is RA: 13 29 37.26; Decl.: +07 02 28.0 (J2000.0, mean residuals of 0.05”, reference stars from GaiaDR2) and the magnitude was estimated to be 19.3 (SNR=12, assuming R mags for the reference stars from GaiaDR2).
The image is available here:
https://www.virtualtelescope.eu/2025/04/22/grb-250419a-detection-of-the-optical-afterglow-19-apr-2025/
- GCN Circular #40209
Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy
Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani.
Report:
We observed the field of GRB 250419A detected by SVOM/ECLAIRs (Wang et al. GCN 40168) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3.
The observations were started at 2025-04-19 23:55 UT (approximately 21.43 hours after burst) stacking a set of unfiltered CCD image. The observations were carried out with clear skies
and good visibility conditions.
The OT was detected at the following position:
RA (J2000.0) 13h 29m 37.33s
Decl. (J2000.0) +07° 02' 27.5"
Photometry was obtained using nearby PanSTARRS stars as follows:
Observation Mid-Time T-T0 (hr) Exposure Filter Mag. Err.
2025-04-20 01:19:29 UT 22.83 164x60s CR 19.76 +/-0.06
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 López et al. (GCN 40169), Xin et al. (GCN 40170), Zheng et al. (GCN 40171), Kumar et al. (GCN 40172), Lipunov et al. (GCN 40179), Odeh et al. (GCN 40180), Perley & Bochenek (GCN 40181), Pankov et al. (GCN 40182), Pérez-Fournon et al. (GCN 40183), Kuin (GCN 40185), Wu et al. (GCN 40186), Xie et al. (GCN 40187), Jiang et al. (GCN 40188), Ghosh et al. (GCN 40189), Bochenek & Perley (GCN 40190), Pankov et al. (GCN 40202), Masi (GCN 40206).
The message may be cited.
- GCN Circular #40210
Edoardo Lagioia, Chenxu Liu, Yuan Fang, Guowang Du, Donglin Gao, Zhang Zepeng, Jinghua Zhang, Brajesh Kumar, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team:
We conducted simultaneous multi-band photometric observations of the gamma-ray burst GRB 250419A (SVOM/ECLAIRs trigger sb25041901 at 2025-04-19T02:29:32 UTC; Wang et al. GCN 40168) with the Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University, located at the Lijiang Observatory. The observations extend over two nights from 19 to 20 April 2025. An optical counterpart is detected in the u-, g-, r-, i-band stacked images but not in the v-, z-band stack. The preliminary photometry and the 3σ upper limits are listed below.
UT start |T-T0 (hr)| Band | Exp | Mag/LimMag (AB)
-------------------|---------|------|--------|--------------------------
2025/4/19 21:13:29 | 18.73 | u | 2x300s | > 20.63
2025/4/19 21:25:42 | 18.94 | v | 2x300s | > 20.91
2025/4/19 21:13:29 | 18.73 | g | 2x300s | 19.84 +/- 0.19
2025/4/19 21:25:42 | 18.94 | r | 2x300s | 19.92 +/- 0.10
2025/4/19 21:13:29 | 18.73 | i | 2x300s | 19.58 +/- 0.12
2025/4/19 21:25:42 | 18.94 | z | 2x300s | > 20.27
* Note: The above two sets of 300s exposures are taken at altitude ~ 23 deg.
UT start |T-T0 (hr)| Band | Exp | Mag/LimMag (AB)
-------------------|---------|------|--------|--------------------------
2025/4/20 17:10:04 | 38.68 | u | 2x300s | 21.47 +/- 0.39
2025/4/20 17:10:06 | 38.68 | g | 2x300s | 21.00 +/- 0.17
2025/4/20 17:10:04 | 38.68 | i | 2x300s | 20.42 +/- 0.18
-------------------|---------|------|--------|--------------------------
2025/4/20 19:50:05 | 41.34 | v | 1x300s | > 22.18
2025/4/20 19:50:04 | 41.34 | r | 1x300s | 21.15 +/- 0.29
2025/4/20 19:50:07 | 41.34 | z | 1x300s | > 21.30
Follow-up observations have already confirmed the presence of an optical counterpart ((López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon et al., GCN 40183; Kuin, GCN 40185; Wu et al., GCN 40186; Xie et al., GCN 40187; Jiang et al., GCN 40188; Ghosh et al., GCN 40189; Bochenek & Perley, GCN 40190; Pankov et al., GCN 40202; Gianluca Masi, GCN 40206; Giovanni Calapai & Massa S. Giorgio, GCN 40209). The ESO/X-Shooter spectroscopic observations identify a redshift of z = 0.845 (Thakur et al., GCN 40174).
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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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- GCN Circular #40212
Genevieve Schroeder (Cornell), Anna Ho (Cornell), Daniel Perley (LJMU) report:
We observed the position of the SVOM/ECLAIRs GRB 250419A (Wang et al. GCN 40168), with the NSF’s Karl G. Jansky Very Large Array (VLA) under program 25A-374 (PI Perley) beginning on 2025 April 22 at 06:37 UT (3.2 days post discovery) at a mean frequency of 10 GHz (4 GHz bandwidth). Based on preliminary analysis, we clearly detect a radio source with a 10 GHz flux density of ~320 uJy and a position of:
RA(J2000) = 13:29:37.275
Dec(J2000) = +07:02:27.63
with an uncertainty of ~0.2" in each coordinate. This is consistent with the location of the optical counterpart of GRB 250419A (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon et al., GCN 40183; Kuin, GCN 40185; Wu et al., GCN 40186; Xie et al., GCN 40187; Jiang et al., GCN 40188; Ghosh et al., GCN 40189; Bochenek & Perley, GCN 40190; Pankov et al., GCN 40202; Gianluca Masi, GCN 40206; Giovanni Calapai & Massa S. Giorgio, GCN 40209; Lagioia et al., GCN 40210).
At the redshift of GRB 250419A (Thakur et al., GCN 40174), the VLA observation corresponds to a 18.5 GHz (rest-frame) luminosity of ~1e31 erg/s/Hz. This luminosity is similar to a typical long GRB radio afterglow at a similar epoch (e.g., Chandra & Frail 2012, ApJ 746, 156, Laskar et al. 2023, ApJ, 946, 23).
Additional followup is planned.
We thank the VLA staff for quickly approving and executing these observations.
- GCN Circular #40234
M. Brunet (IRAP), M. G. Bernardini (INAF-OAB, LUPM), A. Coleiro, F. Cangemi (APC), O. Godet (IRAP), W. J. Xie, D. H. ZHAO (NAO, CAS), B.-T. Wang (YNAO, CAS), Y. H. Cheng (SWIFAR,YNU)
Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 250419A (SVOM burst-id sb25041901).
The burst that triggered ECLAIRs onboard (GCN 40168) consists of a single pulse with a duration of T90 = 11.44 -2.58/+2.85 s in the 5-8 keV energy band. However, the full dataset shows another pulse with a duration of ~15 s at ~Tb-120 s. No counts are detected above 12 keV for the first pulse and above 10 keV for the second one, making this event very soft.
The time-averaged spectrum of the first pulse (from Tb-118s to Tb-102s) in the energy range 4-12 keV is best fit by a simple power-law model with a photon index 3.01 -0.69/+0.80.
The time-averaged spectrum of the second pulse (from Tb to Tb+20s) in the energy range 4-10 keV is best fit by a simple power-law model with a photon index 3.02 -0.53/+0.56.
The total fluence in the 4-10 keV band is (1.41 -0.37/+0.03) e-7 erg/cm^2.
In both time intervals, a black-body model (zbb model in Xspec with z = 0.845, GCN 40174) provides an adequate fit to the data. The first pulse has a temperature of 2.44 -0.54/+0.64 keV, and the second one a temperature of 2.28 - 0.31/+0.38 keV. In that case, the total fluence is (1.38 0.10/+0.06) e-7 erg/cm^2.
All the quoted errors are at the 90% confidence level.
The spectral fits suggest that the Epeak of this burst is below the ECLAIRs energy range, i.e. <4 keV. Therefore this burst could be classified as an X-Ray Flash (XRF).
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.
- GCN Circular #40238
Dimple and B. P. Gompertz (U. Birmingham) report:
We conducted follow-up observations of GRB 250419A (Wang et al., GCN 40168) with the IO:O camera on the 2m robotic Liverpool Telescope (LT). Observations began at 21:52:15.745 UT on 2025-04-23 and consisted of 5x120 s exposures in each of the SDSS g and r filters. We do not detect the optical afterglow (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon et al., GCN 40183; Kuin et al., GCN 40185; Wu et al., GCN 40186; Xie et al., GCN 40187; Jiang et al., GCN 40188; Ghosh et al., GCN 40189; Bochenek & Perley, GCN 40190; Pankov et al., GCN 40202; Masi, GCN 40206; Calapai, GCN 40209) to 3-sigma limiting AB magnitudes of g > 22.42 and r >22.45, at a mid-time of 4.82 days after trigger. Observations were calibrated against nearby Pan-STARRS stars and are not corrected for foreground extinction.
- GCN Circular #40239
A. Bochenek and D. A. Perley (LJMU) report:
We have been regularly observing the optical afterglow of SVOM-detected GRB250419a (Wang et al., GCN 40168, Brunet et al. GCN 40234), first reported by López et al. (GCN 40169) and Xin et al. (GCN 40170), using the IO:O optical camera on the 2m robotic Liverpool Telescope in the SDSS r and i filters. Observations began on 2025-04-19 (Perley & Bochenek, GCN 40181) and have continued nightly since.
The most recent set of observations was a set of 8x100s exposures starting at 2025-04-23 21:52:15 UT, approximately 4.86 days after the trigger. We report a detection, given below, in both bands.
MJD (mid) T_mid-T_0 Filter Mag. (AB)
60788.97067 4.86 d r 23.20 ± 0.27
60788.98199 4.87 d i 22.91 ± 0.22
The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. The magnitudes are consistent with the upper limit from earlier in the night reported by Gompertz et al. (GCN 40238).
The source is currently fading rapidly: a fit to our observations taken 2 days and later after the trigger gives a power-law decay index of approximately -2.1, consistent with a post-jet-break evolution.
- GCN Circular #40245
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN:
We continued observations of the field of GRB 250419A (Wang et al., GCN 40168; Page et al., GCN 40111; Page et al., GCN 40176) at the redshift of z = 0.845 (Thakur et al., GCN 40174) with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The R-band observations began on 2025-04-22 at 17:29:31 UT, i.e. ~3.65 days since trigger. The field of the optical counterpart was observed by (López et al., GCN 40169; Xin et al., GCN 40170; Zheng et al., GCN 40171; Kumar et al., GCN 40172; Thakur et al., GCN 40174; Lipunov et al., GCN 40179; Odeh et al., GCN 40180; Perley & Bochenek, GCN 40181; Pankov et al., GCN 40182; Pérez-Fournon et al., GCN 40183; Kuin, GCN 40185; Wu et al., GCN 40186; Xie et al., GCN 40187; Jiang et al., GCN 40188; Ghosh et al., GCN 40189; Bochenek & Perley, GCN 40190; Pankov et. al, GCN 40202; Masi, GCN GCN 40206; Calapai, GCN 40209; Lagioia et al., GCN 40210; Dimple & Gompertz, GCN 40238; Bochenek & Perley, GCN 40239). We detect the OT in the stacked image. The preliminary photometry is as follows:
Date UTstart Exptime t-T0 Filter OT Err UL
(s) (mid, days) (3sigma)
2025-04-22 17:29:31 45*120 3.65625 R 21.83 0.15 22.5
The photometry is based on nearby USNO-B1.0 stars (R2 magnitudes, provided in Pankov et al., GCN 40182) and has not been corrected for the Galactic extinction.
Previous IAU Circulars 