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

[vsnet-grb-info 37878] GRB 250322A: Swift/UVOT Upper Limits
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39861 SUBJECT: GRB 250322A: Swift/UVOT Upper Limits DATE: 25/03/24 12:52:39 GMT FROM: Sam Shilling at Lancaster University <shilling.sam(a)gmail.com> S. P. R. Shilling (Lancaster U.) and R. Gupta (NASA/GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250322A 77 s after the BAT trigger (Gupta et al., GCN Circ. 39835). No optical afterglow consistent with the enhanced XRT position (Goad et al., GCN Circ. 39841) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 77 226 147 >20.5 u_FC 291 541 246 >19.8 white 77 1711 411 >20.9 v 620 1760 136 >18.9 b 546 1686 117 >19.7 u 291 1661 343 >20.0 w1 669 1807 134 >19.2 m2 644 1785 136 >19.0 w2 596 1736 136 >19.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.153 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/39861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37877] EP250324A: COLIBRÍ/DDRAGO Optical Observations
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39860 SUBJECT: EP250324A: COLIBRÍ/DDRAGO Optical Observations DATE: 25/03/24 11:57:56 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Jean-Grégoire Ducoin (CPPM), Rosa L. Becerra (U Roma), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), Margarita Pereyra (UNAM), Stéphane Basa (LAM), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Jean-Luc Atteia (IRAP), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Francis Fortin (IRAP), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM) and Ny Avo Rakotondrainibe (LAM) report: We observed the field of EP250324A (ID=01709133021) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-03-24 10:12 to 10:27 UTC (0.6 to 0.8 hours after the trigger). The data were coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1. Our photometry is in the AB system and is not corrected for Galactic extinction. Within the EP/WXT localization, we do not detect any uncatalogued sources to a 5-sigma limiting magnitude of : i > 22.20 Further analysis of the additional images is 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/39860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37876] GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39859 SUBJECT: GRB 250322A: VLT/X-shooter redshift confirmation of the putative host galaxy DATE: 25/03/24 11:41:00 GMT FROM: Yu-Han Yang at University of Rome Tor Vergata <yyang(a)roma2.infn.it> Yu-Han Yang (U Rome), Eleonora Troja (U Rome), Rosa Becerra (U Rome), Massine El Kabir (U Rome) report on behalf of the ERC BHianca team: We observed the bright galaxy within the localization of GRB 250322A (Gupta et al., GCN 39835, Goad et al. GCN 39841, Martin-Carillo et al. GCN 39842) with the X-Shooter spectrograph on the ESO VLT UT3 (Melipal). Observations began at T+32.2 hours and obtained a total of 2x600s spectra at an average airmass of about 1.2 and seeing of 0.6”. We detect a bright continuum in the VIS and NIR arms and identify multiple emission lines, including H_alpha, H_beta, NII, OII, SII, at a common redshift of 0.4215±0.0005, consistent with measurement by Fong et al. (GCN 39852). We estimated that the chance coincidence between the bright galaxy and the XRT localization is <2% (Bloom et al. 2002), supporting it as a likely host galaxy of the GRB. We thank the staff at the VLT, for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37875] FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060
by GCN Circulars 24 Mar '25

24 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39858 SUBJECT: FRB 250316A: COLIBRÍ/DDRAGO Optical follow up of the X ray source EP J120944.2+585060 DATE: 25/03/24 05:14:31 GMT FROM: Margarita Pereyra Talamantes at IA-UNAM Ensenada <mpereyra(a)astro.unam.mx> Margarita Pereyra (UNAM), Rosa L. Becerra (U Roma), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Damien Dornic (CPPM), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Einstein Probe source EP J120944.2+585060 (Sun et al., GCN Circ. 39834) possibly associated with FRB 250316A (ID=439373176) detected by CHIME/FRB (Mason et al., ATel #[17081](https://www.astronomerstelegram.org/?read=17081) with the DDRAGO wide-field imager on the COLIBRÍ telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed the field centred in the position of EP J120944.2+585060 from 2025-03-23 08:23:56 to 12:32:11 UTC (6.99 to 7.17 days after the discovery of FRB 250316A) and obtained 2.82 hrs of exposure in the i filter. The data were coadded with custom software and analyzed in STDWeb/STDPipe (Karpov 2021), with photometric calibration against Pan-STARRS DR1 and image subtraction against Pan-STARRS DR2. Our photometry is in the AB system and is not corrected for Galactic extinction. Consistent with previous reports (Becerra et al. ATel #[17082](https://www.astronomerstelegram.org/?read=17082), Niuno et al. ATel #[17084](https://www.astronomerstelegram.org/?read=17084), Hashimoto et al. ATel #[17095](https://www.astronomerstelegram.org/?read=17095), Aryan et al. Circ. GCN 39839, Yang et al. ATel #[17101](https://www.astronomerstelegram.org/?read=17101), Becerra et al. GCN 39843 and Becerra et al. GCN 39853), we do not detect any uncatalogued source to an estimated 5-sigma upper limit of i > 23.6 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/39858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37874] GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst
by GCN Circulars 23 Mar '25

23 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39857 SUBJECT: GRB 250322B: NuSTAR detection of the prompt emission and regular dips during the burst DATE: 25/03/23 17:06:49 GMT FROM: Brian Grefenstette at Caltech/NuSTAR <bwgref(a)srl.caltech.edu> B. Grefenstette (Caltech) reports on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the Long GRB 250322B in both the NuSTAR CsI anti-coincidence shields and in the CdZnTe detectors. This GRB was identified through a blind search using the CsI shield rates. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm triggered at 2025-03-22 20:08:06.000 with a resolution ~5-seconds. This is consistent with the detection by AstroSat CZT (Waratkar et al., GCN circ. 39848). The NuSTAR CsI shield data are recorded at 1 Hz. The GRB appears to be a complex, broad burst with peak count rates near 4,000 cps over a baseline of ~1,000 cps. The burst lasts for over 100-s above background. We see clear evidence for correlated >100 keV X-rays in both CdZnTe focal planes for at least one of the multiple peaks in the burst. Offline analysis of the CsI lightcurve shows complex features, including at least four quasi-periodic “dips” in the emission with intervals of roughly 20-s between the dips. A more detailed analysis of these features will follow. Discovery report and a preliminary lightcurve for this GRB showing the dips can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/250322B/ Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA’s Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/39857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37873] GRB 250321B: Swift-XRT observations
by GCN Circulars 23 Mar '25

23 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39856 SUBJECT: GRB 250321B: Swift-XRT observations DATE: 25/03/23 16:57:22 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M. Capalbi (INAF-IASFPA), M. Perri (SSDC & INAF-OAR), S. Dichiara (PSU), J.A. Kennea (PSU), D.N. Burrows (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), V. D'Elia (SSDC & INAF-OAR) and P.A. Evans (U. Leicester) reports on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected burst GRB 250321B, collecting 2.7 ks of Photon Counting (PC) mode data between T0+81.0 ks and T0+92.8 ks. No X-ray sources have been detected. The 3-sigma upper limit in the field ranges from ~0.005 to ~0.006 ct s^-1, corresponding to a 0.3-10 keV observed flux of 2.1e-13 to 2.4e-13 erg cm^-2 s^-1 (assuming a typical GRB spectrum). The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/ToO_GRBs/00021824. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37872] GRB 250322A: Swift-XRT refined Analysis
by GCN Circulars 23 Mar '25

23 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39855 SUBJECT: GRB 250322A: Swift-XRT refined Analysis DATE: 25/03/23 16:54:19 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M. Perri (SSDC & INAF-OAR), J.A. Kennea (PSU), D.N. Burrows (PSU), M. A. Williams (PSU), A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 3.7 ks of XRT data for GRB 250322A, from 58 s to 22.2 ks after the BAT trigger. The data comprise 7 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=2.28 (+0.18, -0.17). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 2.09 (+0.49, -0.26). The best-fitting absorption column is consistent with the Galactic value of 2.7 x 10^21 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 3.6 x 10^-11 (5.4 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.7 (+/-2.3) x 10^21 cm^-2 Galactic foreground: 2.7 x 10^21 cm^-2 Excess significance: <1.6 sigma Photon index: 2.09 (+0.49, -0.26) If the light curve continues to decay with a power-law decay index of 2.28, the count rate at T+24 hours will be 2.2 x 10^-7 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 7.9 x 10^-18 (1.2 x 10^-17) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01297832. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37871] EP250321a: TNOT Observation of Optical Counterpart
by GCN Circulars 23 Mar '25

23 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39854 SUBJECT: EP250321a: TNOT Observation of Optical Counterpart DATE: 25/03/23 16:31:37 GMT FROM: Xiaofeng Wang at Tsinghua University <wang_xf(a)mail.tsinghua.edu.cn> Haichang Zhu (THU), A. Iskandar(XAO), Xiaofeng Wang (THU), and Letian Wang (XAO) report the detection of the optical counterpart that is associated with the X-ray transient EP250321a (Hu et al., GCN 39800; Fu et al., GCN 39804; Perez-Garcia et al al., GCN 39805; Brivio et al., GCN 39807; Zhu et al., GCN 39809; Becerra et al., GCN 39810; Pérez-Fournon et al., GCN 39812; Lee et al., GCN 39815; Ghosh et al., GCN 39816; Han et al., GCN 39817; Jin et al., GCN 39822; Zhu et al., GCN 39827; Gill et al., GCN 39831). We obtained the r-band images (~12.44 hours after the burst) with the 80~cm Tsinghua-Nanshan Optical Telescope (TNOT) located at Nanshan Station of Xinjiang Astronomy observatory, starting on 2025-03-21 (UT)18:36:10. From the stacked images with a total exposure time of 100sx15, we did not detect the optical afterglow down to a limiting magnitude of about 22.2 mag (MJD=60755.775). The above photometric result is calibrated using the field stars from the Pan-STARRS catalog and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37870] FRB 250316A: DDOTI Continued Optical Observations (Third Epoch)
by GCN Circulars 23 Mar '25

23 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39853 SUBJECT: FRB 250316A: DDOTI Continued Optical Observations (Third Epoch) DATE: 25/03/23 15:37:35 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Eleonora Troja (U Roma), Margarita Pereyra (UNAM), Simone Dichiara (Penn State University), Camila Angulo Valdez (UNAM), Sahil Atri (U Roma), Nat Butler (ASU), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), and Océlotl López (UNAM) report: We observed the field of FRB 250316A (ID=439373176) detected by CHIME/FRB (Mason, ATel #17081) 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 2025-03-23 UTC. DDOTI observed the field centred in the position of EP J120944.2+585060 RA = 182.4341 deg, Dec = 58.8499 deg (J2000) from 03:00 UTC to 12:18 UTC (from T+6.8 days to T+7.2 days after the discovery of FRB 250316A) with a total exposure of 240 minutes. Comparing our observations to the USNO-B1 and PanSTARRS PS1 DR2 catalogues, we detect no evident uncatalogued sources within the observed field to a 3-sigma limiting AB magnitude of w > 22.4 This non-detection is consistent with those reported by Becerra et al. 2025 ATel 17082, Niuno et al. 2025, ATel 17084, Hashimoto ATel 17095, Aryan et al. 2025, Circ. GCN 39839, Yang et al. 2025, ATel 17101, and Becerra et al. GCN 39843. 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/39853. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37869] GRB 250322A: Gemini-North redshift of candidate host galaxy
by GCN Circulars 23 Mar '25

23 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39852 SUBJECT: GRB 250322A: Gemini-North redshift of candidate host galaxy DATE: 25/03/23 13:40:27 GMT FROM: Wen-fai Fong at Northwestern University <wfong(a)northwestern.edu> W. Fong (Northwestern), A. J. Levan (Radboud), J.C. Rastinejad (Northwestern), N. R. Tanvir (Leicester), C. D. Kilpatrick (Northwestern) report on behalf of a larger collaboration: We observed the putative host galaxy within the XRT localization (Goad et al., GCN 39841) of the short-duration GRB 250322A (Gupta et al., GCN 39835; Tembhurnikar et al., GCN 39849) using the Gemini Multi-Object Spectrograph (GMOS-N) mounted on Gemini-North telescope in Hawaii. We obtained 4x900-sec exposures using the R400 grating, spanning approximately 5000A to 9500A, starting at 2025-03-23 05:33:34 UT (approx 13.5 hr post-burst), under Program GN-2025A-Q-114 (PI: Fong). The continuum is well-detected along with several prominent emission lines. In particular, we identify emission lines of H-alpha, NII, OIII (5007), H-beta and H-gamma, corresponding to a common redshift of z=0.42. We thank Jennifer Andrews, Adam Smith, and Hyewon Suh for the rapid scheduling and execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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