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

[vsnet-grb-info 37808] GRB250309B: Proof-of-concept for Joint ZTF+EP Experiment
by GCN Circulars 20 Mar '25

20 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39791 SUBJECT: GRB250309B: Proof-of-concept for Joint ZTF+EP Experiment DATE: 25/03/20 20:29:02 GMT FROM: Tomas Ahumada Mena at Caltech <tahumada(a)caltech.edu> T. Ahumada (Caltech), E. C. Bellm (UW), L. Yan, T. du Laz, M. M. Kasliwal (Caltech), Q. Y. Wu, S. Q. Jiang (NAOC, CAS), J. H. Wu (GZHU), Y. Liu, C. Jin, W. Yuan (NAOC, CAS) report on behalf of the Zwicky Transient Facility Partnership and Einstein Probe Team Starting Feb 27, 2025, the Zwicky Transient Facility (ZTF) partnership is collaborating with the Einstein Probe (EP) team to map multiple EP pointings concurrently every night with ZTF. By cross-matching ZTF alerts with EP alerts, we report our first proof-of-concept cross-match. On March 9, 2025, Fermi-GBM detected GRB 250309B at 07:38:30 UTC (Preis and Greiner, GCN 39629; Fermi GBM team, GCN 39635; McDermott et al., GCN 39642). As part of the regular schedule, EP was set to cover the region, with ZTF scheduled to shadow EP. Both EP and ZTF subsequently observed the afterglow, ZTF25aaitvjt/AT2025dws. The Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission began observations from 2025-03-09T10:38:05(UTC) (~T0+3h) with an exposure time of 4.8 ks. The WXT position of the source is R.A. = 210.800 deg, DEC = -8.500 deg (J2000) with an uncertainty of 3.1 arcmin in radius (90% C.L. statistical and systematic), which is consistent with the optical counterpart AT2025dws (Stein et al., GCN 39639) and the X-ray counterpart (Page and Evans, GCN 39649). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 3.0 x 10^20 cm^-2 and a photon index of 1.8 (-1.2/+1.6). The derived average unabsorbed 0.5-4 keV flux is 9.2 (-5.3/+10.8) x 10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. In this particular example, we clarify that ZTF was double-triggered to observe this field - once by the joint ZTF+EP experiment and once by the IceCube neutrino experiment. Both experiments recovered AT2025dws. We observed a fading rate of 2.5 mag / hour in the r-band. This source was promptly reported by ZTF in Stein et al. GCN 39639. 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). Based on observations obtained with the Samuel Oschin Telescope 48-inch and the 60-inch Telescope at the Palomar Observatory as part of the Zwicky Transient Facility project. ZTF is supported by the National Science Foundation under Award #2407588 and a partnership including Caltech, USA; Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; University of Wisconsin at Milwaukee, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; Operations are conducted by Caltech's Optical Observatory (COO) and Caltech/IPAC. View this GCN Circular online at https://gcn.nasa.gov/circulars/39791. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37807] GRB 250317B: Mondy AZT-33IK Optical Observations
by GCN Circulars 20 Mar '25

20 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39772 SUBJECT: GRB 250317B: Mondy AZT-33IK Optical Observations DATE: 25/03/18 15:19:56 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 250317B (Zhao et. al, GCN 39753; Götz et. al, GCN 39756; Melandri et. al, GCN 39763) at the redshift of z=3.44 (Thoene et. al, GCN 39769) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations started on (UT) 2025-03-17 15:41:49, i.e. about 0.58 days since trigger. The optical afterglow (Watson et. al, GCN 39754; Pérez-Fournon et. al, GCN 39757; Ghosh et. al, GCN 39759; Ferro et. al, GCN 39764; Schneider et. al, GCN 39767; Thoene et. al, GCN 39769; Zhu et. al, GCN 39770) is clearly visible in the stacked image. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err UL(3sigma) (mid, days) (s) 2025-03-17 15:41:49 0.58173 28*120 R 20.88 0.13 22.8 Ref. stars from SDSS-DR12 RA Dec R R_err 211.6590 +40.0703 16.451 0.029 211.5997 +40.0619 18.859 0.055 The photometry is based on nearby stars (see the list above) from the SDSS-DR12 catalog (R magnitudes were obtained using Lupton 2005 transformations) and has not been corrected for the Galactic extinction. Using a simple power law fit to the observed data in the r and R filters, we estimate the light curve decay index to be about -1.5. View this GCN Circular online at https://gcn.nasa.gov/circulars/39772. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37806] GRB 250317B: Mondy AZT-33IK Continued Optical Observations
by GCN Circulars 20 Mar '25

20 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39790 SUBJECT: GRB 250317B: Mondy AZT-33IK Continued Optical Observations DATE: 25/03/20 13:21:09 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 250317B (Zhao et. al, GCN 39753; Götz et. al, GCN 39756; Melandri et. al, GCN 39763) at the redshift of z=3.44 (Thoene et. al, GCN 39769) in the R filter with the 1.5-meter AZT-33IK telescope of the Sayan Solar Observatory (Mondy). The observations started on 2025-03-18 at 18:45:47 (UT), i.e. about 1.72 days since trigger. The optical afterglow (Watson et. al, GCN 39754; Pérez-Fournon et. al, GCN 39757; Ghosh et. al, GCN 39759; Ferro et. al, GCN 39764; Schneider et. al, GCN 39767; Thoene et. al, GCN 39769; Zhu et. al, GCN 39770; Pankov et. al, GCN 39772; Moretti & Pavoni, GCN 39774; Schneider et. al, GCN 39777; Atteia et. al, GCN 39784) is not detected. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err UL(3sigma) (mid, days) (s) 2025-03-18 18:45:47 1.72130 45*120 R n/d n/d 22.9 2025-03-19 18:02:14 2.70077 59*120 R n/d n/d 23.3 Ref. stars from SDSS-DR12 RA Dec R R_err 211.6590 +40.0703 16.451 0.029 211.5997 +40.0619 18.859 0.055 The photometry is based on nearby stars (see the list above) from the SDSS-DR12 catalog (R magnitudes were obtained using Lupton 2005 transformations) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39790. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37805] GRB 250320A: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Mar '25

20 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39789 SUBJECT: GRB 250320A: Fermi GBM Final Real-time Localization DATE: 25/03/20 06:16:17 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 06:05:44 UT on 20 Mar 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250320A (trigger 764143549.57948 / 250320254). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 263.0, Dec = 47.3 (J2000 degrees, equivalent to J2000 17h 32m, 47d 17'), with a statistical uncertainty of 1.2 degrees. The angle from the Fermi LAT boresight is 105.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250320254/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250320254/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250320254/… View this GCN Circular online at https://gcn.nasa.gov/circulars/39789. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37804] Fermi GRB 250319B: Global MASTER-Net observations report
by GCN Circulars 20 Mar '25

20 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39788 SUBJECT: Fermi GRB 250319B: Global MASTER-Net observations report DATE: 25/03/20 05:30:23 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, N.Tiurina, P.Balanutsa, , D.Vlasenko, I.Panchenko, A.Kuznetsov, G.Antipov, A.Sankovich, A.Sosnovskij, Yu.Tselik, M.Gulyaev, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250319B ( Fermi GBM team, GCN 39783) errorbox 44851 sec after notice time and 82295 sec after trigger time at 2025-03-20 03:59:04 UT, with upper limit up to 16.7 mag. Observations started at twilight. The observations began at zenith distance = 40 deg. The sun altitude is -9.9 deg. The galactic latitude b = -15 deg., longitude l = 319 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2817489 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 82326 | 2025-03-20 03:59:04 | MASTER-SAAO | (16h 07m 31.63s , -71d 07m 28.6s) | C | 60 | 16.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/39788. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37803] FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations
by GCN Circulars 20 Mar '25

20 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39787 SUBJECT: FRB 20250316A: Upper limits for gamma-ray transient from Insight-HXMT/HE observations DATE: 25/03/20 02:49:24 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Yan-Qiu Zhang, Wang-Chen Xue, Shao-Lin Xiong, Yue Wang (IHEP) and Ce Cai (HEBNU) report on behalf of the Insight-HXMT team: At the event time 2025-03-16T08:33:50.842 UTC (T0) of FRB 20250316A (Ng et al., ATel 17081; Leung et al., ATel 17086), Insight-HXMT/HE was observing normally and monitored the full location error region of FRB 20250316A. The routine blind search of Insight-HXMT/HE data found no burst candidate around the time of FRB 20250316A. Thus, we implemented a targeted search [1] from T0 - 100 s to T0 + 5 s, and identified no candidate above 3 sigma. Considering three typical spectral models (i.e. soft, normal and hard Band functions), three timescales and the FRB localization (RA = 182.476 deg, Dec = +58.8494 deg (J2000)), the 3 sigma upper limits of the gamma-ray transient energy flux (10 keV-1 MeV, in units of 10^-7 erg/s/cm^2) are reported below: Timescale (s) Soft Normal Hard 0.1 7.17 7.48 3.27 1 2.26 2.36 1.03 10 0.72 0.75 0.33 With the distance of 40.8 Mpc from NGC 4141, the probable host galaxy of this FRB, we further calculate the following upper limits of the gamma-ray transient intrinsic isotropic luminosity (1 keV-10 MeV, in units of 10^47 erg/s): Timescale (s) Soft Normal Hard 0.1 1.43 1.49 0.65 1 0.45 0.47 0.21 10 0.14 0.15 0.07 We note that the above results are preliminary. Refined results will be reported. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/. [1] C. Cai et al. MNRAS, 508, 3910–3920 (2021) https://doi.org/10.1093/mnras/stab2760 View this GCN Circular online at https://gcn.nasa.gov/circulars/39787. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37802] GRB 250313A: GRBAlpha detection
by GCN Circulars 19 Mar '25

19 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39786 SUBJECT: GRB 250313A: GRBAlpha detection DATE: 25/03/19 21:08:05 GMT FROM: Michaela Ďuríšková at Masaryk University <505876(a)mail.muni.cz> M. Duriskova, M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno, H. Takahashi (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, L. Szakszonova, M. Kolar,J.-P. Breuer, F. Hroch (Masaryk U.), T. Urbanec, M. Kasal, A. Povalac (Brno U. of Technology), J. Hudec, J. Kapus, M. Frajt (Spacemanic s.r.o), R. Laszlo, M. Koleda (Needronix s.r.o), M. Smelko, P. Hanak, P. Lipovsky (Technical U. of Kosice), G. Galgoczi (Wigner Research Center/Eotvos U.), Y. Uchida, H. Poon, H. Matake (Hiroshima U.), N. Uchida (ISAS/JAXA), T. Bozoki (Eotvos U.), G. Dalya (Eotvos U.), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), G. Friss (Eotvos U.), Y. Fukazawa, K. Hirose (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), K. Kapas (Eotvos U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), J. Takatsy (Eotvos U.), K. Torigoe (Hiroshima U.), N. Kogiso, M. Yoneyama (Osaka Metropolitan U.), M. Moritaki (U. Tokyo), T. Kano (U. Michigan) -- the GRBAlpha collaboration. The long-duration GRB 250313A (FERMI/GBM: GCN Circular 39703, FERMI/LAT: GCN Circular 39711, AstroSat/CZTI: GCN Circular 39714, SVOM/GRM: GCN Circular 39716, Konus-Wind: GCN Circular 39721, CALET/CGBM: GCN Circular 39725) was observed by the GRBAlpha 1U CubeSat (Pal et al. 2023, A&A, 677, 40; https://ui.adsabs.harvard.edu/abs/2023A%26A...677A..40P/abstract). The detection was confirmed at the peak time 2025-03-13 14:34:41.7 UTC. The T90 duration measured by GRBAlpha is 13 s and the overall significance during T90 reaches 52.3 sigma. The light curve obtained by GRBAlpha is available here: https://grbalpha.konkoly.hu/static/share/GRB250313A_GCN.pdf All GRBAlpha detections are listed at: https://monoceros.physics.muni.cz/hea/GRBAlpha/ GRBAlpha, launched on 2021 March 22, is a demonstration mission for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). The detector of GRBAlpha consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~50 keV to ~1000 keV. To increase the duty cycle and the downlink rate, the upgrade of the on-board data acquisition software stack is in progress. The ground segment is also supported by the radio amateur community and it takes advantage of the SatNOGS network for increased data downlink volume. View this GCN Circular online at https://gcn.nasa.gov/circulars/39786. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37801] LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn
by GCN Circulars 19 Mar '25

19 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39785 SUBJECT: LIGO/Virgo/KAGRA S250206dm: LIGHETR followup observations of AT2025azn DATE: 25/03/19 17:15:20 GMT FROM: Hsin-Yu Chen at The University of Texas at Austin <hsinyu(a)austin.utexas.edu> Hsin-Yu Chen (UT Austin), Greg Zeimann (UT McDonald Observatory), J. Craig Wheeler (UT Austin), and Jozsef Vinko (Konkoly Observatory) report on behalf of the LIGHETR Collaboration: We conducted targeted follow-up observations of AT 2025azn (Hosseinzadeh et al., GCN 39191), a potential electromagnetic counterpart to the LIGO/Virgo/KAGRA gravitational-wave event S250206dm (LVK Collaboration, GCN 39175), using the Low Resolution Spectrograph (LRS2) on the Hobby-Eberly Telescope (HET) [1]. The observations were carried out 9 to 14 days after the gravitational-wave event and consisted of two 1800s exposures with LRS2-R (covering 650–842 nm and 818–1050 nm) and two 1800s exposures with LRS2-B (covering 370–470 nm and 460–700 nm) [2]. Our preliminary analysis did not reveal any emission beyond that of the host galaxy. Further analysis is ongoing. [1] Bustamante Rosell et al, ApJ (2023) [2] Chonis et al, Proceedings of the SPIE (2014) View this GCN Circular online at https://gcn.nasa.gov/circulars/39785. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37800] GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations
by GCN Circulars 19 Mar '25

19 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39784 SUBJECT: GRB 250317B: SVOM/COLIBRI (F-GFT) follow-up observations DATE: 25/03/19 17:09:35 GMT FROM: Jean-Luc Atteia at IRAP <jean-luc.atteia(a)irap.omp.eu> Jean-Luc Atteia (IRAP), Sarah Antier (OCA/IJCLAB), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU), Francis Fortin (IRAP), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Antonio de Ugarte Postigo (LAM), Benjamin Schneider (LAM) report: We imaged the field of the SVOM/ECLAIRs GRB 250317B (Zhao et al. GCN Circ. 39752, Zhao et al. GCN Circ. 39753) with the DDRAGO imager on the COLIBRÍ (SVOM/F-GFT) telescope at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir in Mexico. We observed from 2025-03-19 06:32 to 11:00 UTC and obtained 200 minutes of exposure in the r filter at a mean observing time To+54.5h. The data were coadded with custom software and analyzed with STDpipe (Karpov 2024) 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 afterglow (Watson et al. GCN Circ. 39754, Pérez-Fournon et al. GCN Circ. 39757, Ghosh et al. GCN Circ. 39759, Ferro et al. GCN Circ. 39764, Schneider et al. GCN Circ. 39767, Schneider et al. GCN Circ. 39767, Thoene et al. GCN Circ. 39769, Zhu et al. GCN Circ. 39770, Zhu et al. GCN Circ. 39770, Pankov et al. GCN Circ. 39772, Moretti et al. GCN Circ. 39774, Schneider et al. GCN Circ. 39777) with a magnitude of r = 23.95 +/- 0.25 This confirms the break of the optical light-curve pointed by Schneider et al. in GCN Circ. 39777. We acknowledge excellent support from the staff of the Observatorio Astronómico Nacional. View this GCN Circular online at https://gcn.nasa.gov/circulars/39784. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37799] GRB 250319B: Fermi GBM Final Localization
by GCN Circulars 19 Mar '25

19 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39783 SUBJECT: GRB 250319B: Fermi GBM Final Localization DATE: 25/03/19 15:50:43 GMT FROM: Cuán de Barra at UCD <cuan.debarra(a)ucdconnect.ie> The Fermi GBM team reports the detection of a likely SHORT GRB "At 05:07:28.91 UT on 19 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250319B (trigger 764053653/250319214). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 246.18, Dec = -70.90 (J2000 degrees, equivalent to J2000 16h 25m, 70d 54'), with a statistical uncertainty of 3.18 degrees. The angle from the Fermi LAT boresight is 29 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250319214/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250319214/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250319214/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/39783. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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