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

[vsnet-grb-info 37848] EP250321A: COLIBRÍ Continuing Optical Observations
by GCN Circulars 22 Mar '25

22 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39831 SUBJECT: EP250321A: COLIBRÍ Continuing Optical Observations DATE: 25/03/22 05:50:58 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Ramandeep Gill (UNAM), Ny Avo Rakotondrainibe (LAM), Alan M. Watson (UNAM), Rosa L. Becerra (U Roma), Jean-Grégoire Ducoin (CPPM), Benjamin Schneider (LAM), Stéphane Basa (UAR Pytheas), 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), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM) and Antonio de Ugarte Postigo (LAM), and report: We continued our observations of the field of EP250321A (Hu et al., GCN Circ. 39800) 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 2025-03-22 03:55 to 05:25 UTC (21.75 to 23.26 hours after the trigger). The data were coadded with the custom software 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. We detect the optical counterpart (Fu et al. 2025, GCN Circ. 39804; Perez-Garcia et al. 2025, GCN Circ. 39805; Brivio et al. 2025, GCN Circ. 39807; Zhu et al. 2025, GCN Circ. 39809; Becerra et al. 2025, GCN Circ. 39810; Pérez-Fournon et al. 2025, GCN Circ. 39812; Lee et al. 2025, GCN Circ. 39815; Han et al. 2025, GCN Circ. 39817; Sharma et al. 2025, GCN Circ. 39822) with a magnitude of: i = 22.5 +/- 0.1 Compared to the latest reported measurement in i (Lee et al, GCN Circ. 39815), this corresponds to a decay with a power-law index of approximately -1.3. 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 View this GCN Circular online at https://gcn.nasa.gov/circulars/39831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37847] GRB 250225B: GECAM-A detection
by GCN Circulars 22 Mar '25

22 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39830 SUBJECT: GRB 250225B: GECAM-A detection DATE: 25/03/22 05:45:38 GMT FROM: zhengchao_astro(a)foxmail.com Jia-Cong Liu, Shao-Lin Xiong, Peng Zhang, Yan-Qiu Zhang, Chen-Wei Wang (IHEP) report on behalf of the GECAM team: GECAM-A detected a long burst, GRB 250225B, at 2025-02-25T19:39:13 UTC (denoted as T0), which was also observed by Swift/BAT (H. A. Krimm et al. 2025, GCN 39473), SVOM/GRM (Yan-Qiu Zhang et al. 2025, GCN 39493), Fermi/GBM (M. Godwin et al. 2025, GCN 39502), and Konus-Wind (A. Tsvetkova et al. 2025, GCN 39498). According to the GECAM-A light curves in about 50-200 keV, this burst mainly consists of multiple pulses with a T90 of about 63.2 ± 2.5 s. The GECAM light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250225B.png We note that these results are preliminary. Refined analysis will be reported. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/39830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37846] GRB 250312A: GECAM-A detection
by GCN Circulars 22 Mar '25

22 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39829 SUBJECT: GRB 250312A: GECAM-A detection DATE: 25/03/22 05:44:25 GMT FROM: zhengchao_astro(a)foxmail.com Jia-Cong Liu, Shao-Lin Xiong, Peng Zhang, Yan-Qiu Zhang, Chen-Wei Wang (IHEP) report on behalf of the GECAM team: GECAM-A detected a long burst, GRB 250312A, at 2025-03-12T13:24:17 UTC (denoted as T0), which was also observed by Swift/BAT (A. Melandri et al. 2025, GCN 39686). According to the GECAM-A light curves in about 50-200 keV, this burst mainly consists of a pulse with a T90 of about 5.0 ± 0.2 s. The GECAM light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250312A.png We note that these results are preliminary. Refined analysis will be reported. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two microsatellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/39829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37845] GRB 250321B: Swift ToO observations
by GCN Circulars 22 Mar '25

22 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39828 SUBJECT: GRB 250321B: Swift ToO observations DATE: 25/03/22 03:45:08 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P. A. Evans (U. Leicester) reports on behalf of the Swift team: Swift has initiated a ToO observation of the SVOM/ECLAIRs GRB 250321B. Automated analysis of the XRT data will be presented online at https://www.swift.ac.uk/ToO_GRBs/00021824 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. These are not necessarily related to the SVOM/ECLAIRs event. Any X-ray source considered to be a probable afterglow candidate will be reported via a GCN Circular after manual consideration. Details of the XRT automated analysis methods are detailed in Evans et al. (2007, A&A, 469, 379; 2009, MNRAS, 397, 1177 and 2014, ApJS, 210, 8). This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/39828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37844] EP250321a: WFST optical observations
by GCN Circulars 22 Mar '25

22 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39827 SUBJECT: EP250321a: WFST optical observations DATE: 25/03/22 02:51:05 GMT FROM: Jin-Jun Geng at PMO <jjgeng(a)pmo.ac.cn> Jia-Zheng Zhu, Jin-Jun Geng, Ze-Lin Xu, Ning Jiang, Yan-Long Hua, Yi-Fang Liang, Ding-Fang Hu, Ji-An Jiang, Xue-Feng Wu, and Tian-Rui Sun report on behalf of the WFST team: Following the detection of EP250321a by Einstein Probe (Hu et al., GCN 39800), we use the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at Lenghu Astronomical Observation Base (Qinghai province, China) to search and follow up its afterglow. We observed the target position with 3x120s exposure in r-band starting from 2025-03-21T14:17:14. We clearly detect the optical transient (OT) reported by GCNs (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) in our image. Our preliminary results are as follows: |Date| |UTstart| |t-T0 (hours)| |Exp (sec)| |Filter| |Magnitude| ---------------------------------------------------------------------------------------------- 2025-03-21 14:17:14 8.12 3 x 120 r 22.57 +/- 0.12 We thank the WFST staff for supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37843] GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis
by GCN Circulars 21 Mar '25

21 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39826 SUBJECT: GRB 250320B: NuSTAR detection of the prompt emission from two broad bursts and preliminary analysis DATE: 25/03/21 21:58:08 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 250320B 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 2025-03-20 23:16:29.000 on the second of two bright, broad bursts (with a resolution ~5-seconds). This is consistent with the detections by the Fermi LAT (Airasca et al, GCN circ. 39819), Fermi GBM (Neights et al., GCN circ. 39823), AstroSat CZT (Waratkar et al., GCN circ. 39808) and SVOM/GRM (Zhang et al., GCN circ. 39813). The NuSTAR CsI shield data are recorded at 1 Hz. The GRB appears to be composed of two, broad bursts, each strongly detected above background with peak count rates near 3,000 cps over a baseline of ~1,000 cps. We see clear evidence for correlated >100 keV X-rays in both CdZnTe focal planes for both bursts at the time of the GRB. Using the localization from Fermi LAT at RA = 244.66, Dec = -30.37 implies an offset from the NuSTAR boresight of only 60.49 (e.g., through the side of the instrument) and the offset from the geocenter of 143.51-deg. Discovery report and preliminary reports for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/250320B/ Additional analysis will follow. 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/39826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37842] GRB 250321C: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Mar '25

21 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39825 SUBJECT: GRB 250321C: Fermi GBM Final Real-time Localization DATE: 25/03/21 21:57:57 GMT FROM: Fermi GBM Team at MSFC/Fermi-GBM <do_not_reply(a)GIOC.nsstc.nasa.gov> The Fermi GBM team reports the detection of a likely LONG GRB At 21:47:36 UT on 21 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250321C (trigger 764286461.175894 / 250321908). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 89.3, Dec = -28.5 (J2000 degrees, equivalent to J2000 05h 57m, -28d 30'), with a statistical uncertainty of 5.0 degrees. The angle from the Fermi LAT boresight is 53.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250321908/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250321908/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250321908/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37841] GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results
by GCN Circulars 21 Mar '25

21 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39824 SUBJECT: GRB 250320A: NuSTAR Detection of the Prompt Emission and Preliminary Results DATE: 25/03/21 21:49:59 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 250320A in both the NuSTAR CsI anti-coincidence shields. 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 2025-03-20 06:06:19.000 (with a resolution ~5-seconds). This is consistent with the detections by the Fermi GBM (Fermi GBM Team, GCN circ. 39789). The NuSTAR CsI shield data are recorded at 1 Hz. The GRB appears to be composed of a single, broad burst with a duration of over a minute. The peak count rate is roughly 1,500 cps over a baseline rate is ~1,000 cps during this time period. We do not see a clear evidence in the signal above 100 keV in the CdZnTe detectors. Using the localization from Fermi GBM at RA = 263.0, Dec = 47.3 implies an offset from the NuSTAR boresight of only 17.52 (e.g., through the front of the instrument) and the offset from the geocenter of 103-deg. Discovery report and preliminary reports for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2025/250320A/ Additional analysis will follow. 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/39824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37840] GRB 250320B: Fermi GBM Observation
by GCN Circulars 21 Mar '25

21 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39823 SUBJECT: GRB 250320B: Fermi GBM Observation DATE: 25/03/21 21:09:51 GMT FROM: eliza.neights(a)gmail.com E. Neights (GWU, NASA/GSFC), R. Hamburg (UAH), C. Meegan (UAH) and O.J. Roberts (USRA) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 23:15:22.02 UT on 20 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250320B (trigger 764205327/250320969). which was also detected by AstroSat CZTI (Joshi et al. 2025, GCN 39808), SVOM/GRM (Zhang et al. 2025, GCN 39813), and Fermi LAT (Holzmann Airasca et al. 2025, GCN 39819). The Fermi GBM on-ground location is consistent with the LAT position. The angle from the Fermi LAT boresight is 40 degrees. The GBM light curve consists of multiple emission episodes with a duration (T90) of about 86 s (50-300 keV). The time-averaged spectrum from T0-2.0 to T0+107.5 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.16 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 570 +/- 20 keV. The event fluence (10-1000 keV) in this time interval is (9.02 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+75 s in the 10-1000 keV band is 21.6 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 547 +/- 22 keV, alpha = -1.16 +/- 0.01 and beta = -2.7 +/- 0.2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/39823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37839] EP250321a: Xinglong 216 decaying optical observations
by GCN Circulars 21 Mar '25

21 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39822 SUBJECT: EP250321a: Xinglong 216 decaying optical observations DATE: 25/03/21 19:24:45 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Jinlei-Zhang (NAOC), Pengliang-Du (NAOC), Feng-Xiao(NAOC),Zhou-Fan (NAOC), Hong-Wu (NAOC) We performed optical observations of the field of a fast X-Ray transient EP250321a【( Zhu】 et. al, GCN 【39550】; ) in the Free filter using 2.16-m telescope located at Xinglong, Hebei, China. In the band a 600 s exposures were taken , with a median observation time of 2025-03-02T20:32:28, approximately 5 hours after the EP FXT trigger (2025-03-21T17:04:56). We measure a preliminary magnitude of 20.697 +/- 0.267, mag (AB), calibrated against nearby stars from the Pan-STARRS catalog. We summarize our observation results as follows: 1 | 2025-03-02T20:32:28 | 600 s | Free |20.697 +/- 0.267| 2.16-m telescope View this GCN Circular online at https://gcn.nasa.gov/circulars/39822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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