April 2025 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 38196] GRB 250419A: SVOM/VT optical bright counterpart confirmation
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40170 SUBJECT: GRB 250419A: SVOM/VT optical bright counterpart confirmation DATE: 25/04/19 05:05:51 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/40170. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38195] GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40169 SUBJECT: GRB 250419A: SVOM/COLIBRÍ (FM-GFT) Detection of the Optical Counterpart DATE: 25/04/19 04:51:59 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/40169. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38194] GRB 250419A: SVOM detection of a soft burst
by GCN Circulars 19 Apr '25

19 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40168 SUBJECT: GRB 250419A: SVOM detection of a soft burst DATE: 25/04/19 03:22:36 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> 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(a)ynao.ac.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40168. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38193] Konus-Wind detection of GRB 250416C (a counterpart of EP250416a)
by GCN Circulars 18 Apr '25

18 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40167 SUBJECT: Konus-Wind detection of GRB 250416C (a counterpart of EP250416a) DATE: 25/04/18 17:38:33 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A.Lysenko, A. Ridnaya, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250416C was detected by Konus-Wind (KW) in the waiting mode at about T0=64427 s UT (17:53:47). A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~7 sigma count-rate increase in the interval from T0-6.3 s to T0+11.4 s. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB250416C/ The total burst fluence is 1.50(-0.42,+1.04)x10^-6 erg/cm^2, and the 2.944 s peak energy flux, measured from T0-0.405 s, is 1.57(-0.57,+1.15)x10^-7 erg/cm^2. (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum of the burst, measured from T0-6.3 s to T0+11.4 s, can be described by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.35(-0.36,+0.66) and Ep = 228(-110,+735) keV. The burst was detected simultaneously with the fast X-ray transient EP250416a (T0(EP)=17:53:59 UT; Zhao et al., GCN 40154; Zhou et al., GCN 40165). The positional and temporal coincidence of this burst with the transient supports the conclusion that the EP250416a is the GRB counterpart. All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40167. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38192] EP250416a: Swift/XRT counterpart fading
by GCN Circulars 18 Apr '25

18 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40166 SUBJECT: EP250416a: Swift/XRT counterpart fading DATE: 25/04/18 14:31:17 GMT FROM: Tullia Sbarrato at INAF-OAB <tullia.sbarrato(a)inaf.it> T. Sbarrato (INAF-OAB), R. Brivio (INAF-OAB), C. Salvaggio (INAF-OAB), M. Ferro (INAF-OAB), D. Malesani (DAWN/NBI and Radboud), K. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf the Swift-XRT team: Swift-XRT has performed further follow-up observations of the EP-WXT transient EP250416a (Zhao et al., GCN 40154), collecting a total of 4.0 ks of Photon Counting (PC) mode data between T0+17.1 ks and T0+79.8 ks. The X-ray source detected in the first 2.0 ks of data reported as “Source 1”, consistent with the optical counterpart (Levan et al., GCN 40160), and presented as the possible transient counterpart (Sbarrato et al., GCN 40163) has faded more than 3 sigma in the latest observation, confirming the trend observed by EP-FXT about 12.3 hours after the trigger (Zhou et al., GCN 40165). The flux derived from the follow-up observation is 1.8 (+/-0.4) x 10^-2 cts/s, that corresponds to 6.5 (+/-1.3) x 10^-13 erg cm^-2 s^-1. The light curve can be modelled with a power-law decay with an index of alpha=1.18 A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.0 (+0.5, -0.4). The best-fitting absorption column is 1.6 (+1.7, -1.3) x 10^21 cm^-2. The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.65 x 10^-11 (5.01 x 10^-11) erg cm^-2 count^-1. The observed (unabsorbed) flux obtained from all the PC mode data is thus 1.8 x 10^-12 (2.5 x 10^-12) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/EP/EP_FIELD00034/ This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40166. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38191] EP250416a: refined EP-WXT and EP-FXT analysis
by GCN Circulars 18 Apr '25

18 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40165 SUBJECT: EP250416a: refined EP-WXT and EP-FXT analysis DATE: 25/04/18 01:30:04 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), G.Y. Zhao (SYSU), C. Zhou (HUST), X.L. Chen, K. Chatterjee (YNU) and C.C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: We reduced and analyzed the telemetry data of EP250416a, and all uncertainties reported here are at the 90% confident level. EP250416a became detectable by WXT from ~30 seconds before the trigger time (2025-04-16T17:53:59 UTC, Zhao et al. GCN 40154), and the WXT light curve lasts for ~30 seconds (interupted by the autonomous follow-up observation) with a peak occuring at ~20 seconds after the time when EP250416a became detectable. Lipunov et al. (GCN 40156) and Li et al. (GCN 40157) performed follow-up observations for EP250416a but did not find new optical transient down to i ~20 mag. Later, a possible candidate was detected by Gemini-South (Levan et al. GCN 40160). The WXT spectrum is fitted by an absorbed powerlaw model, which counts for absorption of the Milky Way and the host galaxy. As suggested by Levan et al. (GCN 40160), the redshift of the host is set to 0.72. The equivalent hydrogen column density of the host, NH, is constrained to be less than ~1.9x10^22 cm^-2 by the WXT spectrum. The photon index of the WXT spectrum is hard, 0.32 (-0.78, +1.00). The mean and peak unabsorbed fluxes (0.5-4 keV) are (5.66+/-1.77)x10^-9 erg/s/cm^2 and (1.92+/-0.76)x10^-8 erg/s/cm^2. The autonomous EP-FXT follow-up observation starts about 2 minutes after the trigger and lasts for 2 orbits with total on-source time of 3936 seconds. In addition, about 12.3 hours after the trigger, another follow-up observation with the EP-FXT was performed for 2962 seconds. Results of the autonomous and the follow-up observations are summarized: +--------------------------------------------------------------------------------+ T_Start^a [UTC] | T_mid - T0^b [h] | Exp [s] | Flux (0.5-10 keV) [erg/s/cm^2] +--------------------------------------------------------------------------------+ 2025-04-16T17:54:53 | 0.17 | 929 | (2.56+/-0.17) x 10^-11 2025-04-16T18:55:35 | 1.49 | 3007 | (7.86+/-0.48) x 10^-12 2025-04-17T06:08:14 | 12.68 | 2962 | (1.64+/-0.20) x 10^-12 +--------------------------------------------------------------------------------+ All fluxes are unabsorbed values derived from FXT-A & FXT-B data. a. The first and the second rows represent the first and the second orbits of the autonomous observation. b. Here T0 is the time that EP250416a became detectable, about 30 seconds before the trigger time. The inferred 0.5-10 keV flux at the XRT epoch is consistent the value derived from the XRT observation (Sbarrato et al. GCN 40163). The model, which is same as the model applied to WXT data, is applied to fit FXT spectra. For the three epochs listed in the above table, the best fitted photon indices are 1.88+/-0.14, 1.98+/-0.15 and 2.23+/-0.38, and the NH of the host are (5.06+/-1.74)x10^21 cm^-2, (5.33+/-1.77)x10^21 cm^-2 and (6.66+/-4.54)x10^21 cm^-2. The contact TA of EP250416a is Guo-Ying Zhao. Please contact her via email zhaogy28(a)mail2.sysu.edu.cn if needed. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40165. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38190] Konus-Wind detection of GRB 250403A
by GCN Circulars 17 Apr '25

17 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40164 SUBJECT: Konus-Wind detection of GRB 250403A DATE: 25/04/17 17:43:37 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaya, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report The long GRB 250403A (Fermi GBM detection: Fermi GBM team, GCN 40025; Veres et al., GCN 40060; SVOM detection: Julacanti et al., GCN 40026; AstroSat CZTI detection: Tembhurnikar et al., GCN 40077) was detected by Konus-Wind (KW) in the waiting mode. A Bayesian block analysis of the KW waiting mode data in the 20-400 keV band reveals a ~12 sigma count-rate increase in the interval from T0-0.4 s to T0+11.5 s where T0 = 15:15:22 UT. The KW light curve of this burst is available at http://www.ioffe.ru/LEA/GRBs/GRB250403A/ Modeling the time-integrated spectrum of the burst by a power law with exponential cutoff (CPL) model dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) yields alpha = -1.14 (-0.23, + 0.23) and Ep = 83(-6,+6) keV. In the 10 keV -10 MeV band, standard for the KW analysis, the burst fluence is (2.55 ± 0.18)x10^-6 erg/cm^2 and the 2.944 s peak energy flux is (2.51 ± 0.22)x10^-7 erg/cm^2/s. Assuming the redshift z=1.847 (de Ugarte Postigo et al., GCN 40162) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the burst isotropic energy release E_iso to (2.2 ± 0.2)x10^52 erg, the isotropic peak luminosity L_iso to (6.3 ± 0.6)x10^51 erg/s, and the rest-frame peak spectral energy Ep,z to (236 ± 11) keV. With the obtained estimates, GRB 250403A is consistent (inside 68% prediction bands) of both 'Amati' and 'Yonetoku' relations for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250403A/GRB250403A_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40164. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38189] EP20250416a: Swift/XRT counterpart detection
by GCN Circulars 17 Apr '25

17 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40163 SUBJECT: EP20250416a: Swift/XRT counterpart detection DATE: 25/04/17 15:06:58 GMT FROM: Tullia Sbarrato at INAF-OAB <tullia.sbarrato(a)inaf.it> T. Sbarrato (INAF-OAB), R. Brivio (INAF-OAB), M. Ferro (INAF-OAB), C. Salvaggio (INAF-OAB) and P.A. Evans (U. Leicester) report on behalf the Swift-XRT team: Swift-XRT has performed follow-up observations of EP/WXT-detected transient EP 250416a (Zhao et al., GCN 40154). We searched for X-ray sources in 2.0 ks of Photon Counting (PC) mode data, from T0+17.1 ks to T0+23.2 ks after the EP/WXT trigger. An uncatalogued X-ray source is detected within the estimated 3-sigma EP/WXT error region. Using 2000 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 = 256.41935, +25.7751 which is equivalent to: RA (J2000): 17h 05m 40.64s Dec(J2000): +25d 46’ 30.4" with an uncertainty of 3.1 arcsec (radius, 90% confidence). This position is 1 arcmin from the EP/WXT position, and consistent with the optical candidate reported by Levan et al., (GCN 40160). The source has a mean count rate of 9.9e-02 ct/sec and currently shows no signs of fading. The results of the XRT-team automatic analysis are available at https://www.swift.ac.uk/EP/EP_FIELD00034/ This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40163. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38188] GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847
by GCN Circulars 17 Apr '25

17 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40162 SUBJECT: GRB 250403A: VLT/FORS2 spectroscopic redshift z = 1.847 DATE: 25/04/17 14:35:25 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> A. de Ugarte Postigo (LAM), A. Saccardi (CEA/Irfu), B. Schneider (LAM), L. Izzo (INAF/OAC and DARK/NBI), J. P. U. Fynbo (DAWN/NBO), Y. Julakanti (Univ. Leicester), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. T. Palmerio (CEA/Irfu), S. Savaglio (Univ. Calabria), N. R. Tanvir (Univ. Leicester), S. D. Vergani (LUX-Obs. de Paris, CNRS), report on behalf of the Stargate collaboration: We observed the optical and NIR counterpart (Starling et al., GCN 40028; Wu et al., GCN 40029; Du et al., GCN 40031; Li et al., GCN 40032; Julakanti et al., GCN 40034; Ghosh et al., GCN 40039; Jiang et al., GCN 40041; Pérez-Fournon et al., GCN 40043; Brivio et al., GCN 40044; Xin et al., GCN 40045; Shilling et al., GCN 40048; Zheng et al., GCN 40065; Leonini et al., GCN 40068) of the SVOM/ECLAIRs (Julakanti et al., GCN 40026), Fermi/GBM (Veres et al., GCN 40060), and AstroSat CZTI (Tembhurnikar et al., GCN 40077) GRB 250403A using the ESO/VLT UT1 (Antu) equipped with the FORS2 spectrograph. The 300V grism with no order-blocking filter was adopted, covering the wavelength range 3300-9600 AA (with potential second-order contamination redward of 6600 AA). Observations started on 2025 April 4 at 02:15:01 UT (10.99 hr after the burst). Two exposures of 600 s each were obtained. From a 60 s acquisition image obtained on 2025 April 4 at 02:01:37 UT (10.76 hr after the burst), we measure R ~ 21.1 +/- 0.2 mag (AB) calibrated against nearby Pan-STARRS objects. From a preliminary reduction of the spectrum, continuum is detected over the wavelength range 3600-9600 AA. While the spectrum is noisy blueward of 3720 AA, we can set an upper limit to the redshift z < 2.06 due to the lack of Lyman forest. Four clear absorption features are apparent in clean regions of the spectrum, three of which match Si IV 1393, Si IV 1402 and the (blended) C IV doublet 1548,1550 at a common redshift z = 1.847. The fourth line seems marginally split and could be an intervening C IV doublet at z = 1.763, although no other features are seen to confirm this value. The observed absorption system is somewhat peculiar (but not unprecedented), as some typically strong low-ionization features common in long GRB spectra (de Ugarte Postigo et al. 2012, doi:10.1051/0004-6361/201219894) are either non-detected or only marginally detected. This indicates a high-ionization environment, which has been previously linked to systems with low H I column density (e.g. Jakobsson et al. 2006, doi:10.1051/0004-6361:20066405; Thoene et al. 2011, doi:10.1111/j.1365-2966.2011.18408.x; Vielfaure et al. 2020, doi:10.1051/0004-6361/202038316). We thus consider z = 1.847 a viable possibility, and the most likely redshift of GRB 250403A. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Matias Jones, Claudia Paladini, Jesus Corral-Santana, and Cecilia Bustos. View this GCN Circular online at https://gcn.nasa.gov/circulars/40162. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38187] IceCube-250416A: DDOTI Optical Observations
by GCN Circulars 17 Apr '25

17 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40161 SUBJECT: IceCube-250416A: DDOTI Optical Observations DATE: 25/04/17 14:21:17 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Sahil Atri (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM) and Margarita Pereyra (UNAM) report: We observe the field of the IceCube-250416A (bronze) event with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on the Sierra of San Pedro Martir (http://ddoti.astroscu.unam.mx) on the night of 2025-04-17 UTC. DDOTI observed from 03:20 UTC to 04:31 UTC (from T+8.8 h to T+10.0 h after the trigger) with a total exposure of 24 min, alternating with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues and after performed image subtraction against PanSTARRS PS1 DR2, we detect no uncatalogued sources within the observed field to an average 5-sigma limiting AB magnitude of: w > 20.5. This value has not been corrected for Galactic extinction (A_r∼1.7 mag; Schlafly et al. 2011). We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/40161. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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