- GCN Circular #39915
Alan M. Watson (UNAM), Ramandeep Gill (UNAM), Sarah Antier (OCA/IJCLAB), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Francesco Magnani (CPPM), Diego López-Cámara (UNAM), Benjamin Schneider (LAM), Dalya Akl (AUS), Camila Angulo (UNAM), 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), Kin Ocelotl López (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Antonio de Ugarte Postigo (LAM) report:
We imaged the field of the SVOM/ECLAIRs GRB 250329A (sb25032901) with the DDRAGO wide-field imager on the SVOM/COLIBRÍ (F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico.
We observed from 2025-03-29 04:18 to 04:55 UTC (55 to 2256 seconds after the trigger) and obtained 26 minutes of exposure in the i filter. The data were coadded with custom software and analyzed in STDWeb/STDPipe (Karpov 2024), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction.
Within the SVOM/ECLAIRs error box, we detect a bright uncatalogued source at RA = 197.44679 and Dec = 9.49533 (J2000) with a magnitude of
i = 17.91 +/- 0.03
Further observations are planned.
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 #39916
B.-T.Wang(YNAO, CAS), Y.H. Cheng (SWIFAR, YNU), W.J. Xie, D.H. Zhao (NAOC), C.W. Wang (IHEP), and D. Götz (CEA) on behalf of the SVOM mission team.
At 2025-03-29T04:17:54 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250329A (SVOM burst-id sb25032901). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network.
The burst was only detected by the Count-Rate Trigger (CRT), which produced a sequence of 17 alerts. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 37.28 in the [8-50] keV energy band over a time window of 5.10 seconds starting at Tb.
The localization of the best alert is R.A., Dec 197.4374, 9.4849 degrees (J2000) with a 90% C.L.radius of 2.88 arcmin (including systematic error of 2 arcmin added in quadrature).
The burst was also detected by GRM. The GRM light curve shows that this burst consists of a single main pulse.
The SVOM/GRM lightcurve can be found here:
https://www.bursthub.cn//admin/static/svgrb250329A.png
SVOM slewed to the burst position.
MXT began observing the field at 2025-03-29T04:20:20 UTC, 146 seconds after Tb.
Using onboard processed data we found a faint uncatalogued X-ray source located at R.A., Dec 197.4168, 9.5412 degrees:
RA (J2000) = 13h09m40s
DEC (J2000) = 9d32m28s
with a 90% C.L. radius of 2.5 arc minutes.
This location is 3.59 arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received.
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 #39917
B.-T. Wang (YNAO, CAS), Y.H. Cheng (SWIFAR, YNU), W.J. Xie, L.P. Xin, Y. L. Qiu, H. L. Li, C. Wu (NAOC), J. T. Palmerio(CEA/Irfu), Z. H. Yao, Y. Xu, P. P. Zhang, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC) report on behalf of the SVOM team:
SVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Wang et al., GCN 39916). SVOM/VT began observing the field automatically with the slew of the platform triggered on-board, in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
With VHF downlinked data, an uncatalogued source was found in VT_R channel, and fading for about 0.4 mag in the third and fourth sequences.
The coordinates are
R.A (J2000) =13:09:47.23 (197.44674 deg)
DEC.(J2000) = +09:29:43.2 (+9.49532 deg)
Error=0.5 arcseconds.
The coordinates are consistent with the candidate reported (Watson et al., GCN 39915).
The magnitude is VT_R=20.1+/- 0.04 mag(AB) and VT_B>22.0 mag(AB,3sigma) with the mid time of 1.25 hours after the burst. We propose it is possible a medium/high redshift GRB, given on red coulor (Wang et al., 2020).
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 #39918
B. Schneider (LAM), G. Corcoran (UCD), E. Le Floc’h (CEA), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), N. R. Tanvir (Leicester), report on behalf of the Stargate collaboration:
We observed the optical counterpart (Watson et al., GCN 39915, Wang et al. GCN 39917) of the SVOM/ECLAIRs GRB 250329A (Wang et al., GCN 39916) using the ESO/VLT UT3 (Melipal) equipped with the X-shooter spectrograph.
In a 10-s r-band exposure taken with the acquisition camera (1.58 hr after the SVOM trigger), a source is well detected at the location of the counterpart reported by Watson et al., GCN 39915 with a magnitude r = 21.9 +/- 0.1 (AB, calibrated against a single Pan-STARRS object). Our measurement is consistent with Wang et al. GCN 39917 and confirms the fast fading nature of this source and its likely association with GRB 250329A.
Our spectra, covering the wavelength range 3000-21000 AA, consist of 4 exposures of 600 s each. The observation mid time was on 2025 Mar 29.2611 UT (1.97 hr after the SVOM trigger). In a preliminary reduction of the spectra, a break is visible at ~4775 AA, which we identify as due to HI Lyman-alpha absorption. From the detection of multiple narrow absorption features, including OI, Si II, C II, Si IV, C IV, Fe II, Al II, Al III, Mg I, Ni II*, Fe II*, Mg II, Ca II, we infer a redshift of z = 2.921.
We acknowledge excellent support from the ESO observing staff in Paranal, in particular Martina Baratella, Felipe Gaete, Rob van Holstein, and Vincent Megevand. We would like to thank especially the two visitors at UT3, Helmut Wiesemeyer and Mario van den Ancker for their patience while our observation was being taken.
- GCN Circular #39922
Ankur Ghosh, Soebur Razzaque (CAPP, University of Johannesburg), Rahul Gupta (NASA GSFC), Alexander Moskvitin, Yulia Sotnikova (SAO RAS), Naveen Dukiya (ARIES) on behalf of a larger collaboration.
We observed the field of the GRB 250329A triggered by the SVOM/ECLAIRs (Wang et al., GCN 39916) in the B, V filter of the 1-meter Sinistro telescope at the Las Cumbres Observatory Global Telescope (LCOGT) node located at McDonald Observatory. The 1-m Sinistro telescope is equipped with a 4K x 4K CCD (FOV: 26 x 26 arcmin, scale: 0.39 arcsec/pixel).
Observations began on March 29, 2025, starting 1.49 hours after the GRB trigger.
We clearly detect the optical transient (OT) reported by GCNs (Watson et al., GCN 39915, Wang et al. GCN 39917, Schneider et al., GCN 39918) in our B, V band image.
--------------------------------------------------------------------------------------------------
|Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude|
--------------------------------------------------------------------------------------------------
2025-03-21 05:46:30.432 1.49 1 x 600 B B = 22.28 +/- 0.08
2025-03-21 05:47:59.424 1.51 3 x 300 V V = 21.95 +/- 0.16
--------------------------------------------------------------------------------------------------
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 #39924
S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U.
Leicester), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), R. Brivio
(INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans (U.
Leicester) reports on behalf of the Swift-XRT team:
We have analysed 1.6 ks of XRT data for the SVOM/ECLAIRs-detected burst GRB 250329A, from 6.8 ks to 13.1 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. Using 1005 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 = 197.44646, +9.49619 which is equivalent to:
RA (J2000): 13h 09m 47.15s
Dec(J2000): +09d 29' 46.3"
with an uncertainty of 4.7 arcsec (radius, 90% confidence). This position is 51 arcsec from the SVOM/ECLAIRs position, and 3.3 arcsec from the optical candidate first reported by Watson et al., (GCN. Circ 39915).
The source has a mean count rate of 3.0e-02 ct/sec and shows weak (1.4-sigma) indications of fading.
The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/00019666.
This circular is an official product of the Swift-XRT team.
- GCN Circular #39927
M. Ferro, R. Brivio, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB), and A. Melandri (INAF-OAR) report on behalf of the REM team:
We observed the field of GRB250329A (Wang et al., GCN 39916) 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 2025 March 29 at 04:19:30 UT (i.e. 96 s after the SVOM trigger), and lasting for about 3 hours.
From preliminary photometry we detect the counterpart in the optical images at the position of the optical afterglow (Watson et al., GCN 39915; Wang et al., GCN 39917; Schneider et al., GCN 39918; Ghosh et al., GCN 39922) with the following magnitude:
r = 17.2 +/- 0.1 (AB; calibrated against the Pan-STARRS catalogue)
at a mid-time of t - t0 = 165 s after the trigger.
- GCN Circular #39985
N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP),
R. Ya. Inasaridze (AbAO), A. S. Moskvitin (SAO RAS), O. I. Spiridonova (SAO
RAS), Yu. V. Sotnikova (SAO RAS), A. Ghosh (CAPP,
University of Johannesburg), S. Razzaque (CAPP, University of Johannesburg)
and IKI GRB-FuN report
We observed the field of GRB 250329A (Wang et al., GCN 39916;
Dichiara et al., GCN 39924) in the R filter with the 0.7-meter AS-32
telescope of the Abastumani Observatory (AbAO), in the R filter with the
1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy) and in
the Rc filter with the 1-meter Zeiss-1000 of SAO RAS.
We do not detect the OT (Watson et al., GCN 39915; Wang et al.,
GCN 39917; Schneider et al., GCN 39918; Ghosh et al., GCN 39922; Ferro et
al., GCN 39927) down to the following limits.
Date UT start t-T0 Filter Exp. UL(3sigma) Telescope
(mid, d) (s)
2025-03-29 17:07:10 0.56824 R 98 x 60 21.7 AS-32
2025-03-29 19:11:57 0.64726 R 38 x 120 22.7 AZT-33IK
2025-03-29 20:00:02 0.66837 Rc 7 x 300 22.3 Zeiss-1000
Photometry is based on nearby USNO-B1.0 stars and is not corrected for
Galactic extinction
RA Dec R2
197.4269 9.4669 15.26
197.4732 9.4981 13.49
197.4408 9.5091 15.64
- GCN Circular #40010
M.H. Siegel (PSU) and R. Caputo (GSFC) reports on behalf of the Swift/UVOT team:
The Swift/UVOT began settled observations of the field of GRB 250329A 6.8ks after the SVOM trigger sb25032901 (Wang et al., GCN Circ. 39916). We do not detect an afterglow at the position of the XRT counterpart (Dichiara et al., GCN Circ. 39924) or optical-infrared counterparts (Watson et al., GCN Circ. 39915; Want et al., GCN Circ. 39917; Ghosh et al., GCN Circ. 39922). The lack of detection in the u-band for this bright burst would be consistent with the redshift of z=2.9 reported by Schneider et al. (GCN Circ. 39918).
Preliminary detections and 3-sigma upper limits for the early exposures are:
Filter T_start(s) T_stop(s) Exp(s) Mag(AB)
u 6812 13135 1551 >20.95
The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.021 in the direction of the burst (Schlegel et al. 1998).
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