- GCN Circular #39719
Y. Wang (PMO, CAS), Rui-Zhi Li (YNAO, CAS), M. Brunet, H. Yang (IRAP), T.Maiolino (LUPM)
on behalf of the SVOM mission team.
SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250314A (SVOM burst-id sb25031405) starting at 2025-03-14T12:56:42 UTC (Tb).
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), from which we received 1 alert. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 9.18 in the 8-120 keV energy band
over a time window of 10.2 seconds starting at Tb.
The light curve shows a single main episode, lasting ~20 s in ECLAIRs (5-120 keV) and ~10 s in GRM (5-550 keV).
The localization of the best alert is R.A., Dec 201.272, -5.293 degrees:
RA (J2000) = 13h25m05.28s
Dec (J2000) = -05d17m36.30s
with a 90% C.L. radius of 8.62 arcmin (including systematic error of 2 arcmin added in quadrature).
The SVOM/GRM light curve can be found here:
https://www.bursthub.cn//admin/static/svgrb250314A.png
SVOM slewed to the burst.
MXT and VT began observing the field after the slew. The analysis of the recorded data will be published in a future circular.
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 Y. Wang: wangyun@pmo.ac.cn.
Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst.
- GCN Circular #39722
J. T. Palmerio (CEA), L.P. Xin (NAOC), S. D. Vergani (Obs. Paris), Y. Wang (PMO, CAS), Rui-Zhi Li (YNAO, CAS), Y. L. Qiu, H.L. Li., C. Wu, Z.H. Yao, Y.N. Ma, X.H. Han, H.B. Cai, J.Y. Wei (NAOC), Y. Canton, M. Garnichey, (Obs. Paris) report on behalf of the SVOM/VT team:
After the trigger by SVOM/ECLAIRs at 2025-03-14T12:56:42 UTC (Tb), SVOM performed an automatic slew on the burst. SVOM/VT began observing the field at 2025-03-14T13:01:28, 285 seconds after the SVOM trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously.
From a preliminary analysis of the 1bit subimage and source list donwloaded via VHF, no credible candidate is identified down to VT_R~20. The subimage and source list cover ~55% of the ECLAIRs uncertainty region (Wang et al. GCN 39719).
Further analysis will be performed once the full dataset is received via X-Band.
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 #39727
D. B. Malesani (DAWN/NBI), G. Corcoran (UCD), L. Izzo (INAF/OAC and DARK/NBI), B. Schneider (LAM), J. Palmerio (CEA/Irfu), A. Henderson de la Fuente (NOT) report on behalf of a larger collaboration:
We observed the field of the SVOM GRB 250314A (Wang et al., GCN 39719) using the Nordic Optical Telescope equipped with the NOTCam near-infrared camera. Observations were carried out in the J band, for a total exposure time of 18 min on source, at a mean epoch of March 15.0523 UT (12.3 hr after the trigger).
A faint object is apparent at coordinates (J2000):
RA = 13:25:12.16
Dec = -05:16:55.1
Calibrating against nearby 2MASS stars, we measure J = 20.85 +- 0.15 (Vega).
Nothing is visible at this location in the Legacy Survey nor in the Vista Hemisphere Survey (VHS), down to limits r > 24.5 (AB) and J > 20 (Vega).
The position of this object is consistent with a bright X-ray source visible in public observations carried out by the Neil Gehrels Swift Observatory X-ray telescope (XRT; target ID 19616, PI Kennea). We thus consider this source as a plausible NIR counterpart candidate of GRB 250314A, though detection of fading will be necessary to confirm this hypothesis.
- GCN Circular #39728
H.L. Li (NAOC), R.-Z. Li (YNAO, CAS), Y. Wang (PMO, CAS), J.X. Cao, D.F. Kong (GXU), L.P. Xin, Y. L. Qiu, C. Wu, Z.H. Yao, Y.N. Ma, X.H. Han, J. Wang, W.J. Xie, Y. Xu, H.B. Cai, J.Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM team:
SVOM performed an automatic slew on the burst triggered by SVOM/ECLAIRs (Wang et al., GCN 39719). 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 X band downlinked data, no any credible candidates were found in our single or stacked images within the errorbox of Eclairs (Wang et al., GCN 39719) compared to DESI catalog, or at the position of NOT candidate (Malesani et al., GCN 39727) in J-band.
The 3 sigma limits in AB magnitude were derived as follows:
---------------------------------------------------------
(t-T0)_mid(hr) exptime(ks) Band upperlim (3sigma)
2.2 2.85 VT_R 23.3
2.2 3.30 VT_B 23.3
If the NOT candidate is confirmed as the counterpart of the burst, given the non-detection in the VT-B and VT-R stacked images at early phase, it is likey the high-z GRB candidate.
More deeper photometries in near-inferred or spectroscopies of the source are encouraged to confirm the nature of the event.
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 #39729
D. Götz (CEA), F. Robinet (IJCLab), H. Goto (CEA), C. Plasse (CEA), P. Maggi (ObAS), M. Moita (CEA), C. van Hove (IJCLab) on behalf of the MXT team report:
The field of GRB 250310A (Wange et al. GCN 39719, Li et al. 39728) was observed by MXT promptly after the SVOM slew starting at 12:59:55 UT, i.e. 193 s after ECLAIRs trigger. The analysis conducted on board did not reveal any significant source in the field of view of the telescope.
By analyzing the full available MXT data set, we do not detect any X-ray counterpart within the ECLAIRs error box, nor at the position of the possible J-band/X-ray afterglow (Malesani et al. GCN 39727), down to a 3 sigma upper limit of about 5.5e-11 ergs/cm^2/s in the 0.5-10 keV energy range. This upper limit likely favours a high-z scenario, rather than a nearby highly extinguished GRB.
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. MXT has been developed by CNES in collaboration with CEA, IJCLab, University of Leicester and MPE.
- GCN Circular #39732
D. B. Malesani (DAWN/NBI and Radboud), G. Pugliese (API-UvA), J. P. U. Fynbo (DAWN/NBI), B. Schneider (LAM), V. D’Elia (SSDC and INAF-OAR), A. de Ugarte Postigo (LAM), L. Izzo (INAF-OACn and DARK/NBI), P. G. Jonker (Radboud), A. J. Levan (Radboud and Warwick), J. T. Palmerio (CEA/Irfu), N. A. Rakotondrainibe (LAM), A. Saccardi (CEA/Irfu), N. R. Tanvir (U. Leicester), A. L. Thakur (INAF-IAPS), S. D. Vergani (CNRS, Obs. Paris/LUX), D. Xu (NAOC), Z.P. Zhu (NAOC) report on behalf of the Stargate collaboration:
We observed the near-infrared candidate counterpart (Malesani et al., GCN 39727) of the long SVOM/ECLAIRs GRB 250314A (Wang et al., GCN 39719) at the ESO VLT, using the HAWK-I near-infrared imager (on UT4, Kueyen) and the X-shooter spectrograph (on UT3, Melipal).
The object is well detected in the Y, J and H filters. HAWK-I observations started on 2025 Mar 15 at 05:23:28 UT (about 16.5 hr after the GRB). We measure preliminary AB magnitudes:
Y = 23.2 +/- 0.15
J = 22.4 +/- 0.1
H = 22.5 +/- 0.1
For the spectra, the observation mid time was 2025 Mar 15.26 UT (about 17.4 hr after the GRB). The data cover the wavelength range 3000-21,000 AA and consist of 4 exposures of 1200 s each.
In a preliminary reduction of the spectra, a faint continuum is confidently detected all across the NIR arm (down to 10,300 AA). Tentative signal is also seen in the very red end of the VIS arm, with a drop around 10,090 AA. While the S/N is too low to confidently identify individual metal absorption features, the break in the VIS is consistent with the onset of the Lyman forest (with possible contribution from damped Lyman-alpha absorption in the GRB host galaxy). The implied redshift is z ~ 7.3.
The HAWK-I photometry is consistent with a break, rather than with a generically red shape of the continuum, given the red Y-J vs blue J-H color, consistent with the Y filter being partly dropped out. Assuming a power law model (no dust extinction), a fit to the available photometry provides a redshift z = 7.21 +0.18 -0.38 (1 sigma c.l.), fully consistent with the spectroscopic value.
We acknowledge expert support from the ESO staff in Paranal.
- GCN Circular #39734
J. A. Kennea (PSU), V. D'Elia (SSDC & INAF-OAR), P. A. Evans (Leicester) report on behalf of the Swift/XRT Team
At 14:28UT on March 14, 2024 Swift began a Target-of-Opportunity observation of GRB 250314A, a SVOM ECLAIRs detected GRB (GCN #39719). Swift finds a uncatalogued point source inside the ECLAIRS error region at the following position: RA(J2000) = 201.30136, -5.2823:
RA(J2000) = 13h 25m 12.22s,
Dec(J2000) = -05h 16' 56.1'',
with an estimated uncertainty of 3.5 arc-seconds radius (90% confidence). This position matches the reported optical counterpart (GCN #39727) with a reported redshift of z = 7.21 (GCN #39732). The XRT source has a peak flux of 2.2 x 10^-12 erg/s/cm^2 (0.3 - 10 keV).
As Swift has performed only a single observation, we cannot confirm fading. We note also the presence of 2 other X-ray sources in the XRT field of view, source #2 lies at the edge of the ECLAIRs error region, source #3 lies outside. Given reported observations of source #1 and it's redshift, we do not believe these sources are credible afterglow candidates:
Source no: 2
RA (J2000): 201.33727 [degrees] = 13h 25m 20.94s
Dec (J2000): -5.16436 [degrees] = -05d 09' 51.7"
Error: +4.8 [arcsec, 90% conf. radius]
Flag: Good
Source no: 3
RA (J2000): 201.44746 [degrees] = 13h 25m 47.39s
Dec (J2000): -5.27117 [degrees] = -05d 16' 16.2"
Error: +5.3 [arcsec, 90% conf. radius]
Flag: Good
- GCN Circular #39737
M. H. Siegel (PSU) reports on behalf of the Swift/UVOT team:
Swift/UVOT observed the field of GRB250314A (Wange et al., GCN 39719) for a total of 1.6 ks
in the U-band from 5.7 ks to 7.4 ks after the SVOM/ECLAIRs detection. We detect no optical/UV source at the position of the infrared (Malesani et al., GCN Circ 39727) and XRT (Kennea et al., GCN Circ. 39734) detections to an upper limit of u>20.94. This lack of detection would be consistent with the redshift reported by Malesani et al. (GCN Circ. 39732).
XRT source #2 corresponds to a known optical source with a u-band magnitude of 16.99+-0.03. XRT source #3 is off the edge of the UVOT field.
- GCN Circular #39739
D. Turpin, B. Cordier (CEA), H. Q. Cheng, H. N. Yang (NAO, CAS), P. Y. Han (WHU), W. Yuan (NAO, CAS) Y. Wang (PMO, CAS), Rui-Zhi Li (YNAO, CAS) on behalf of the SVOM and Einstein Probe teams
We performed a follow-up observation of GRB 250314A (Wang et al., GCN 39719) with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation started at 2025-03-14 21:48:20 (T-TGRB ~ 8.9 hr) for about 1.1ks of exposure in total.
A fading uncatalogued X-ray source is detected by both FXT-A and FXT-B at the position (J2000) RA, DEC = 201.3007, -5.2822 (error=10", 90% C.L.), 1.8 arcminute away from the SVOM/ECLAIRs position (Wang et al., GCN 39719). This position is consistent with the infrared afterglow candidate detected by the NOT and VLT/X-shooter (Malesani et al. GCN 39727; GCN 39732) and the Swift-XRT afterglow candidate source 1 (Kennea et al., GCN 39734).
The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 2.8 x 10^21 cm^-2 and a photon index of ~2.4. The derived average unabsorbed 0.5-10 keV flux is 5.2 (-/+1.6) x 10^(-13) erg/s/cm^2. Compared to the Swift-XRT epoch (Kennea et al., GCN 39734), the flux of the source 1 has shown a significant fading. We thus conclude this source is indeed the x-ray afterglow of GRB 250314A.
Further observations of the GRB 250314A are planned with EP-FXT.
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 #39743
N. A. Rakotondrainibe (LAM), A. de Ugarte Postigo (LAM), L. Izzo (INAF/OACN), D. B. Malesani (DAWN/NBI and Radboud), J. F. Agui Fernandez (CAHA), J. P. U. Fynbo (DAWN/NBI), S. Geier (GTC), G. Lombardi (GTC), A. Martin-Carrillo (UCD), N. R. Tanvir (Leicester), C. C. Thoene (AbAO), and G. Gomez Velarde (GTC) report on behalf of a larger collaboration:
We observed the optical counterpart (Malesani et al., GCN 39727; see also Kennea et al., GCN 39734; Turpin et al., GCN 39739) of the SVOM/ECLAIRs GRB 250314A (Wang et al., GCN 39719), using the Gran Telescopio Canarias equipped with the OSIRIS+ camera. A sequence of 30 exposures of 30 s each (15 min in total) was secured in the z band, with mid time 2025 March 15.24 UT (16.8 hr after the GRB).
In a preliminary reduction, no source is detected down to a 3-sigma limiting magnitude z > 24.4 (AB), calibrated against nearby stars from the Legacy Survey.
Adding our z-band limit to the nearly simultaneous YJH photometry provided by VLT/HAWK-I (Malesani et al., GCN 39732) allows us to derive a more refined photometric redshift of z = 7.27 +0.14 -0.19 (1 sigma c.l.), assuming a power-law afterglow model with no dust extinction.
The lack of optical detection is consistent with, and provides further evidence for, the high redshift of this GRB (Malesani et al., GCN 39732).
- GCN Circular #39746
SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP)
SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM)
Report on behalf of the SVOM team:
With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of the high redshift burst, GRB 250314A (Wang et al., GCN #39719). The GRM light curve shows that this burst consists of a single main episode with a T90 of 7.0 +3.6/-3.7 s in the 15-5000 keV band, which is consistent with the result from VHF data.
The GRM on-ground localization of this burst is consistent with ECLAIRs (Wang et al., GCN #39719). With the localization of ECLAIRs (RA=201.272, DEC=-5.293), the time-averaged spectrum from T0-1 to T0+9 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.75 +0.19/-0.46 and the cutoff energy, parameterized as Epeak, is 43 +26/-19 keV. The event fluence (10-1000 keV) in this time interval is (3.1 +0.5/-0.8)E-07 erg/cm^2.
With the measured redshift z=7.3 (D. B. Malesani et al., GCN 39732), we calculate the isotropic energy Eiso is about 4.6E52 erg. Thus GRB 250314A is well consistent with Type II GRBs in the 'Amati' relation diagram, as shown at:
https://www.bursthub.cn//admin/static/grb250314A_amati.png
We note that the calibration of SVOM/GRM is undergoing thus these results are preliminary. Refined analysis will be reported later.
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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS.
The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang@ihep.ac.cn)
- GCN Circular #39761
R. Brivio, M. Ferro, S. Covino, P. D'Avanzo, S. Campana (INAF-OAB), D. B. Malesani (DAWN/NBI and Radboud), A. Melandri (INAF-OAR), D. Fugazza (INAF-OAB) report on behalf of the REM team:
We observed the field of the SVOM GRB 250314A (Wang et al., GCN 39719), followed-up by Swift/XRT (Kennea et al., GCN 39734) and EP/FXT (Turpin et al., GCN 39739), with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, J, H, and K bands, started on 2025 March 15 at 01:18:28 UT (i.e. 12.4 hr after the burst), and lasted for about 1 hour.
From preliminary inspection, we do not find any counterpart at the position of the reported NIR afterglow (Malesani et al., GCN 39727; Malesani et al., GCN 39732) down to the following 3sigma limits:
r > 18.1 (AB; calibrated against the Pan-STARRS catalogue),
at a mid-time of 12.9 hours after the trigger,
H > 16.1 (Vega; calibrated against the 2MASS catalogue),
at a mid-time of 12.8 hours after the trigger,
J > 16.8 (Vega; calibrated against the 2MASS catalogue)
at a mid-time of 13.0 hours after the trigger.
- GCN Circular #39779
Tao An, Yuanqi Liu, Kexuan Chong (SHAO), Jinjun Geng, Xuefeng Wu (PMO), report on behalf of a large collaboration:
We have conducted radio observations of the high-redshift gamma-ray burst GRB 250314A (GCN 39719, 39729; redshift z ~ 7.3, GCN 39732, 39743) using the Australia Telescope Compact Array (ATCA). Our observations were performed on 2025 March 15, from UT 13:00 to 19:00, simultaneously at central frequencies of 5.5 GHz and 9 GHz. The achieved 1-sigma image rms noise levels are approximately 13 microJy/beam at 5.5 GHz and 9 microJy/beam at 9 GHz. At the position of the potential optical counterpart reported in GCN 39727, we find no significant radio emission above a 3-sigma threshold at either frequency.
We thank Jamie Stevens for his rapid response in scheduling these observations.
We thank the CSIRO Space and Astronomy staff for supporting these observations. 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 #39797
WeiKang Zheng, Alexei V. Filippenko (UC Berkeley), Chris Fassnacht,
Prayaag Katta (UC Davis), D. B. Malesani (DAWN/NBI) and Jing Wang (NAOC),
report on behalf of the KAIT GRB team:
We observed the field of the SVOM GRB 250314A (Wang et al., GCN 39719)
with the NIRC2 camera on the Keck II 10 m telescope. The observations
were performed in the J band (without AO) starting on 2025 March 16 at
12:54:21 UTC (i.e., 2.0 days after the burst), and consisted of 2x120 s
exposures. At the reported NIR afterglow position (Malesani et al.,
GCN 39727; Malesani et al., GCN 39732), we do not detect any counterpart
with an upper limit of J > 19.4 mag (Vega).
- GCN Circular #39954
Nayana A. J. (UC Berkeley), T. Laskar (University of Utah), R. Margutti (UC Berkeley), K. D. Alexander (University of Arizona), R. Chornock (UC Berkeley), E. Berger (Harvard University), W. Fong (Northwestern University), P. Schady (University of Bath), and G. Schroeder (Cornell University) report:
"We carried out Karl G. Jansky Very Large Array (VLA) observations of the high-redshift (z ~ 7.3; Malesani et al., GCN 39732; Rakotondrainibe et al., GCN 39743) SVOM/ECLAIRs GRB 250314A (Wang et al., GCN 39719) beginning on 2025 March 21 06:26 UTC (6.7 days after the burst) at multiple frequencies. In preliminary analysis, we detect a radio counterpart with a flux density of ~ 0.1 mJy at 17 GHz, and position:
RA (J2000) = 13:25:12.16
Dec (J2000) = -05:16:55.07
with a (statistical) uncertainty of 0.6" in each coordinate. This position is consistent with the optical position (Malesani et al., GCN 39727). Further observations are planned.
We thank the VLA staff for scheduling and executing these observations"
- GCN Circular #40012
T. Laskar (University of Utah), R. Margutti, R. Chornock, Nayana A. J. (UC Berkeley), K. D. Alexander (University of Arizona), and H. Sears (Rutgers University) report:
“We observed the high-redshift (z ~ 7.3; Malesani et al., GCN 39732; Rakotondrainibe et al., GCN 39743) SVOM/ECLAIRs GRB 250314A (Wang et al., GCN 39719) with the Atacama Large Millimeter/Submillimeter Array (ALMA) beginning on 2025 March 26 02:55 UTC (11.6 days after the burst) at multiple frequencies.
Preliminary analysis reveals a mm source with flux density of ~ 40 microJy at 42 GHz at position:
RA (J2000) = 13:25:12.14
Dec (J2000) = -05:16:55.29
with an uncertainty of 0.18" in each coordinate. This is consistent with the optical position (Malesani et al., GCN 39727) and radio position (Nayana A. J. et al., GCN 39954). We note that GRBs 250314A and 090423 (z ~ 8.2; Tanvir et al., Nature, 461, 7268, 1254; Castro Tirado et al., GCN 9273; de Ugarte Postigo et al., A&A, 538, A44, 2012) are the highest-redshift GRBs with mm-band detections so far. Further ALMA observations are planned.
We thank the ALMA Director for rapidly granting our DDT request and the JAO staff, AoD, P2G, and the entire ALMA team for their help with these observations."
- GCN Circular #40134
A.L. Thakur [1], G. Bruni [1], L. Piro [1] and G. Gianfagna [1] report:
We observed the z=7.3 GRB 250314A (SVOM GCN 39719, VLT/X-shooter GCN 39732, GTC/OSIRIS+ GCN 39743), with the e-MERLIN radio telescope under project RR19004 (PI: Thakur) at 5 GHz starting from Mar 31 (~17 days post-GRB) for three runs of ~12 hours each.
1331+3030 was used for flux scale calibration, and 1332-0509 for complex gain. The beam size was 122x34 milli-arcsec. Data were reduced with the e-MERLIN pipeline and imaged with CASA. The image RMS was 18 uJy/beam.
We do not find statistically significant emission at a level above 5-sigma at the position of the NOT counterpart (GCN 39727) or in the broader 2x2 arcsec field. We thus set a 5-sigma upper limit of 90 uJy at 5 GHz.
Further e-MERLIN observations are planned.
We thank the e-MERLIN director for promptly approving these DDT observations and acknowledge Justin Bray's excellent support in scheduling and executing them. e-MERLIN is a National Facility operated by the University of Manchester at Jodrell Bank Observatory on behalf of STFC, part of UK Research and Innovation.
—------------------------
[1] INAF-IAPS
- GCN Circular #40553
Z.-Y. Zheng (SHAO), S.R. Zhu (SHAO), J. X. Wang (USTC), J. E. Rhoads (NASA/GSFC), S. Malhotra (NASA/GSFC), I. G. B. Wold (NASA/GSFC), F. Barrientos (PUC), L. Infante (LCO), W. Hu (TAMU), C. Jiang (SHAO), D. Xu (NAOC), and F. Valdes (NOIRLab) report on behalf of the CIDER collaboration:
We observed the near-infrared NB1008 narrowband counterpart (Malesani et al., GCN 39727; see also Kennea et al., GCN 39734; Turpin et al., GCN 39739) of the SVOM/ECLAIRs GRB 250314A (Wang et al., GCN 39719), using the Blanco 4m Telescope equipped with the Dark Energy Camera and a small fraction of the CIDER project’s observing time. A sequence of 19 exposures of 540 s each and 4 exposures of 180s each (3.1 hrs in total) was secured in the NB1008 band, with mid time 2025 April 3 (on Apr. 2-4, about 20 days after the GRB).
In a preliminary reduction, no source is detected at the GRB position down to a 1-sigma upper limiting magnitude NB1008 ~ 23.5 (AB), calibrated with the communication pipeline for DES.
We also took a 0.35 hrs exposure in the i-band with DECam and no source is detected down to a 1-sigma upper limiting magnitude of i ~ 26.7 (AB), consistent with the high redshift of this GRB.
If the redshift 7.27 is correct from the previous spectroscopic and photometric confirmation (z ~ 7.27; Malesani et al., GCN 39732; Rakotondrainibe et al., GCN 39743), the NB1008 filter would cover the pure Lya flux of the GRB host galaxy. The NB1008 band‘s 1-sigma upper limit of 23.5 (AB) can be converted to a Lya flux of < 4.2e-17 erg/cm^2/s, and a Lya luminosity of < 3.1e+43 erg/s at z=7.27. Based on the line emission ratio of Lya to Ha in Case B recombination (Osterbrock et al. 1989) and the relation between SFR and the Ha luminosity (Kennicutt 1998), the derived SFR of the GRB host galaxy is < 28 M_sun/yr (1-sigma upper limit).
- Cordier et al., Astron.Astrophys. 704 (2025) L7
z=7.3 and SVOM capabilities
- Levan et al., Astron.Astrophys. 704 (2025) L8
GRB-supernova revealed with JWST/NIRCAM
Previous IAU Circulars 
