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

[vsnet-grb-info 38246] EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963
by GCN Circulars 23 Apr '25

23 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40219 SUBJECT: EP250416a / GRB 250416C: Gemini GMOS-S likely host galaxy redshift z = 0.963 DATE: 25/04/23 18:19:28 GMT FROM: Jonathan Quirola at Radboud University <jaquirola1990(a)gmail.com> Andrew J. Levan (Radboud), Jonathan Quirola-Vásquez (Radboud), Peter G. Jonker (Radboud), Franz E. Bauer (UTA), Antonio Martin-Carrillo (UCD), Daniele B. Malesani (DAWN/ NBI and Radboud), Javi Sánchez-Sierras (Radboud), Maria E. Ravasio (Radboud), Agnes van Hoof (Radboud), Jennifer Chacon (PUC), Joyce van Dalen (Radboud), Gregory Corcoran (UCD) report on behalf of a larger collaboration: We observed the optical and X-ray counterpart (Levan et al., GCN 40160; Sbarrato et al., GCN 40166) of the Einstein Probe (EP) transient EP250416a (Zhao et al., GCN 40154, 40165), also identified as GRB 250416C (Svinkin et al., GCN 40167; Wang et al., GCN 40184). Observations were carried out using the Gemini South telescope located on Cerro Pachon, Chile, equipped with the GMOS-S instrument in spectroscopy mode. Observations started on 2025-04-17 at 07:44:43 (i.e., ~0.58 days after the EP detection), and consisted of 4 exposures of 900 s each using the B480 grating, covering the wavelength range between ~4000 and 9500 AA. In our spectrum, we clearly detect an emission line at 7317 AA. Considering the most likely options for this feature (Halpha, Hbeta, [O III], [O II]), the interpretation more consistent with the data is the (unresolved) [O II] 3727/3729 doublet at z = 0.963. In all other cases, we would expect to see other features which would fall over well-covered regions of the spectrum, which are not observed. We thus suggest that this is the redshift of the host galaxy of EP250416a. The spectrum shows tentative absorption features at the expected locations of Mg II (2796, 2803 AA) and Mg I (2852 AA) at z = 0.962, although the signal to noise in the blue region of the spectrum is badly affected by the bright Moon, hence we cannot conclusively determine an absorption redshift. We acknowledge excellent support from the Gemini South staff. View this GCN Circular online at https://gcn.nasa.gov/circulars/40219. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38245] EP250421a: Upper limits from Fermi-GBM Observations
by GCN Circulars 23 Apr '25

23 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40218 SUBJECT: EP250421a: Upper limits from Fermi-GBM Observations DATE: 25/04/23 14:26:25 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (Radboud Univ.), E. Burns (LSU), C. Malacaria (INAF-OAR) and P.G. Jonker (Radboud Univ.) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial coverage of the transient EP250421a detected by EP-WXT (Zhao et al., GCN 40198). There was no Fermi-GBM onboard trigger around the EP starting time T0=2025-04-21T16:16:28 UTC. The GBM targeted search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [T0-50;T0+500] s, seeking signals between 64 ms and 32.768 s in duration. A candidate was found at T0+380 s, but its location is not consistent with the EP transient. No signal consistent with the EP transient, both temporally and spatially, is identified, as confirmed also by visual inspection of the data. Assuming a “soft” spectral template (Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7), and a duration of 8.192 s, we derive a flux upper limit of 3.7e-08 erg/cm2/s in the energy band 10-1000 keV. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/40218. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38244] SVOM/sb25042207: XRT observations
by GCN Circulars 23 Apr '25

23 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40217 SUBJECT: SVOM/sb25042207: XRT observations DATE: 25/04/23 13:45:35 GMT FROM: Antonino D'Ai' at IASF-PA <antonino.dai(a)inaf.it> Antonino D'Aì (INAF/IASFPA), J. A. Kennea (PSU), Elena Ambrosi (INAF/IASFPA), Valerio D'Elia (SSDC & INAF-OAR), Andrea Melandri (INAF-OAR) reports on behalf of the Swift-XRT team: We have analysed 1.8 ks of XRT data for the SVOM/ECLAIRs-detected X-ray transient sb25042207 (Liang et al., GCN Circ. 40213), from T0+3.8 ks to T0+5.6 ks after the SVOM/ECLAIRs trigger. The data are entirely in Photon Counting (PC) mode. We detect two previously known X-ray sources and two uncatalogued X-ray sources within the ECLAIRs error circle. We note that the ECLAIRs error region overlaps with the Coma cluster region, a well-known galaxy cluster that exhibits significant diffuse X-ray emission. Details of the uncatalogued sources: Source 2: RA (J2000): 194.93972 = 12:59:45.53 Dec (J2000): +27.8781 = +27:52:41.0 Error: 6.0 arcsec (radius, 90% confidence) Count rate: 8 (+5, -4) x 10^-3 ct/s Flux: [3.5 (+2.1, -1.9)] x 10^-13 erg/cm^2/s (observed, 0.3–10 keV) Source 4: RA (J2000): 195.13942 = 13:00:33.46 Dec (J2000): +27.7478 = +27:44:52.0 Error: 7.5 arcsec (radius, 90% confidence) Count rate: 0.011 (+0.005, -0.004) ct/s Flux: [4.8 (+2.1, -1.8)] x 10^-13 erg/cm^2/s (observed, 0.3–10 keV) Both sources are below the RASS limit and show no definitive signs of fading. The results of the XRT team's automatic analysis of the tiled XRT observations, including a position-specific upper limit calculator, are available at: https://www.swift.ac.uk/SVOM/SVOM_FIELD00013/ This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40217. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38243] SVOM/sb25042207: BOOTES-2 early optical upper limit
by GCN Circulars 23 Apr '25

23 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40216 SUBJECT: SVOM/sb25042207: BOOTES-2 early optical upper limit DATE: 25/04/23 07:34:37 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> M. Gritsevich (Univ. of Helsinki), I. Perez-Garcia, M.D. Caballero-Garcia, E. J. Fernandez-Garcia, R. Sanchez-Ramirez, S.-Y. Wu, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC, Granada), Y.-D. Hu (GXU), C. Perez del Pulgar and A. Reina (Univ. of Malaga), R. Fernandez-Munoz (IHSM/UMA-CSIC), and M. Jelinek (ASU-CAS, Ondrejov Obs.), on behalf of a larger collaboration, report: Following the detection of the X-ray transient sb25042207 by SVOM (Liang et al. GCNC [40213](https://gcn.nasa.gov/circulars/40213)) the 0.6m BOOTES-2/TELMA robotic telescope at IHSM UMA “La Mayora” (Malaga, Spain) automatically responded to this high-energy event starting on Apr 22, 23:38:10 UT (i.e. 2 min after alert). On a coadd (20) of images at 00:00:50 UT (mid exposure time; i.e. 24 min post detection), nothing is detected down to 18.1 mag (clear filter), in agreement with the deeper observations taken later on (Belkin et al., GCNC [40215](https://gcn.nasa.gov/circulars/40215)) We would like to thank the staff at IHSM-/UMA-CSIC “La Mayora” for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/40216. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38242] SVOM/sb25042207: GOTO optical upper limits
by GCN Circulars 23 Apr '25

23 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40215 SUBJECT: SVOM/sb25042207: GOTO optical upper limits DATE: 25/04/23 06:57:54 GMT FROM: Sergey Belkin at Monash University <sergey.belkin(a)monash.edu> S. Belkin, 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 optical observations with the Gravitational-wave Optical Transient Observer (GOTO, Steeghs et al. 2022; Dyer et al. 2024) in response to the SVOM/ECLAIRs alert sb25042207 (Liang et al., GCN 40213). Targeted observations were performed on April 22 2025 23:39:55 UT (+1.06 h post trigger) and on April 23 2025 01:20:48 UT (+2.74 h post trigger). The first epoch of observations consisted of 4x90 s exposures, while the second epoch was obtained in survey mode with 4x45 s exposures. All images were taken 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. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. No new transients that could be credibly associated with SVOM/ECLAIRs sb25042207 were detected down to a 5-sigma L-band limiting magnitude of 20.4. Additionally, no source is detected prior to the GRB trigger time in archival GOTO observations (4x45 s; in survey mode) taken 1.347 h before the trigger, down to a 5-sigma L-band upper limit of 19.7 mag. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40215. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38241] GRB 250421A: AstroSat CZTI detection
by GCN Circulars 23 Apr '25

23 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40214 SUBJECT: GRB 250421A: AstroSat CZTI detection DATE: 25/04/23 06:55:12 GMT FROM: Varun Bhalerao at IIT Bombay <varunb(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long-duration GRB 250421A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40191) and Konus-Wind (IPN Notices). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2025-04-21 10:38:34.50 UTC. The measured peak count rate associated with the burst is 137 (+34, -32) counts/s above the background in the combined data of three quadrants (out of four), with a total of 294 (+129, -105) counts. The local mean background count rate was 230 (+3, -5) counts/s. Using cumulative rates, we measure a T90 of 5.6 (+1.7, -3.3) s. The source was also faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2025-04-21 10:38:34.17 UTC. The measured peak count rate associated with the burst is 261 (+67, -71) counts/s above the background in the combined data of all quadrants, with a total of 623 (+290, -324) counts. The local mean background count rate was 1349 (+10, -10) counts/s. We measure a T90 of 4.8 (+1.3, -3.1) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40214. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38240] SVOM/sb25042207: SVOM detection of an X-ray transient
by GCN Circulars 22 Apr '25

22 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40213 SUBJECT: SVOM/sb25042207: SVOM detection of an X-ray transient DATE: 25/04/22 23:53:42 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Yifang Liang (PMO), Ziqi Wang (GXU), Wenjin Xie (NAOC), Stephane Schanne (CEA) report on behalf of the SVOM mission team: SVOM/ECLAIRs triggered on the X-ray transient labelled sb25042207 (SVOM burst-id sb25042207) starting at 2025-04-22T22:36:17 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 Image Trigger (IMT), which produced a sequence of 1 alert. IMT provided the alert with the best signal-to-noise ratio (SNR) of 7.01 in the 5-8 keV energy band over a time window of 1310.72 seconds starting at Tb. The localization of the best alert is R.A., Dec 194.9273, 27.7745 degrees: RA (J2000) = 12h59m42.56s Dec (J2000) = 27d46m28.13s with a 90% C.L. radius of 11.17 arcmin (including systematic error of 2 arcmin added in quadrature). We notice the presence of many X-ray candidate sources inside the error region, including 2 QSOs, as well as 2 nearby AGNs including Mrk 60. SVOM did not slew to this transient because it did not exceed the slew threshold. SVOM follow-up observations will be scheduled. 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 transient is Yifang Liang: yfliang(a)pmo.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/40213. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38239] GRB250419A: VLA radio detection
by GCN Circulars 22 Apr '25

22 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40212 SUBJECT: GRB250419A: VLA radio detection DATE: 25/04/22 21:29:01 GMT FROM: Genevieve Schroeder at Cornell University <genevieveschroeder(a)u.northwestern.edu> 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. View this GCN Circular online at https://gcn.nasa.gov/circulars/40212. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38238] IceCube-250421A: DDOTI Detection of the LAST Candidate
by GCN Circulars 22 Apr '25

22 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40211 SUBJECT: IceCube-250421A: DDOTI Detection of the LAST Candidate DATE: 25/04/22 19:03:39 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (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-250421A (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 2025-04-22 UTC. DDOTI automatically pointed to the region centred in RA, Dec (J2000)= 16:03:46.49 +28:43:50.8, covering about 96% of the IceCube error region. DDOTI observed from 04:50 UTC to 11:47 UTC (from T+ 11.74 h to T+ 18.69 h after the trigger) with a total exposure of 3.5 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect the candidate reported by SN 2025cbj at w=18.53+/0.04, consistent with the observations from the Large Array Survey Telescope (Garrappa et al., GCN Circ. 40208). No other uncatalogued sources within the observed field to an average 10-sigma limiting AB magnitude of: w > 20.7 This value is not corrected for the Galactic extinction. 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/40211. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 38237] IceCube-250421A: DDOTI Detection of the LAST Candidate
by GCN Circulars 22 Apr '25

22 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40211 SUBJECT: IceCube-250421A: DDOTI Detection of the LAST Candidate DATE: 25/04/22 19:03:39 GMT FROM: sahil.atri(a)students.uniroma2.eu Sahil Atri (U Roma), Rosa L. Becerra (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-250421A (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 2025-04-22 UTC. DDOTI automatically pointed to the region centred in RA, Dec (J2000)= 16:03:46.49 +28:43:50.8, covering about 96% of the IceCube error region. DDOTI observed from 04:50 UTC to 11:47 UTC (from T+ 11.74 h to T+ 18.69 h after the trigger) with a total exposure of 3.5 hours, alternating with other scientific programs. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect the candidate reported by SN 2025cbj at w=18.53+/0.04, consistent with the observations from the Large Array Survey Telescope (Garrappa et al., GCN Circ. 40208). No other uncatalogued sources within the observed field to an average 10-sigma limiting AB magnitude of: w > 20.7 This value is not corrected for the Galactic extinction. 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/40211. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0