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

[vsnet-grb-info 37658] GRB 250309B: Fermi GBM Observation
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39642 SUBJECT: GRB 250309B: Fermi GBM Observation DATE: 25/03/10 00:47:24 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> P. McDermott (UCD), P. Veres (UAH) and L. Scotton (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:38:30.66 UT on 09 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250309B (trigger 763198715/250309318). The Fermi GBM on-ground location was reported in GCN 39635. The angle from the Fermi LAT boresight is 77 degrees. The GBM light curve consists of an emission episode with multiple peaks, with a duration (T90) of about 6.4 s (50-300 keV). The time-averaged spectrum from T0+0.003 to T0+8.192 s is best fit by a Band function with Epeak = 93 +/- 5 keV, alpha = -0.98 +/- 0.06 and beta = -2.40 +/- 0.08. The event fluence (10-1000 keV) in this time interval is (1.07 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.8 s in the 10-1000 keV band is 23 +/- 0.4 ph/s/cm^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/39642. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37657] Fermi GRB 250309B: Global MASTER-Net observations report
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39641 SUBJECT: Fermi GRB 250309B: Global MASTER-Net observations report DATE: 25/03/09 22:31:38 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250309B ( Fermi GBM team, GCN 39635) errorbox 53228 sec after notice time and 53238 sec after trigger time at 2025-03-09 22:25:49 UT, with upper limit up to 17.4 mag. The observations began at zenith distance = 61 deg. The sun altitude is -48.7 deg. The galactic latitude b = 44 deg., longitude l = 331 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2805642 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 53269 | 2025-03-09 22:25:49 | MASTER-Kislovodsk | (13h 59m 30.46s , -13d 45m 18.7s) | C | 60 | 17.4 | 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/39641. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37656] Fermi GRB 250309A: Global MASTER-Net observations report
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39640 SUBJECT: Fermi GRB 250309A: Global MASTER-Net observations report DATE: 25/03/09 22:31:05 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250309A ( Fermi GBM team, GCN 39623) errorbox 71845 sec after notice time and 71879 sec after trigger time at 2025-03-09 20:40:03 UT, with upper limit up to 16.2 mag. The observations began at zenith distance = 81 deg. The sun altitude is -50.2 deg. The galactic latitude b = 0 deg., longitude l = 140 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2805313 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 71900 | 2025-03-09 20:40:03 | MASTER-Kislovodsk | (02h 47m 28.83s , +38d 43m 03.4s) | C | 40 | 15.5 | 71955 | 2025-03-09 20:40:03 | MASTER-Kislovodsk | (02h 47m 28.84s , +38d 43m 03.3s) | C | 150 | 16.2 | Coadd 71965 | 2025-03-09 20:41:03 | MASTER-Kislovodsk | (02h 47m 28.70s , +38d 42m 52.8s) | C | 50 | 15.4 | 72040 | 2025-03-09 20:42:13 | MASTER-Kislovodsk | (02h 47m 28.63s , +38d 42m 43.8s) | C | 60 | 15.6 | 72130 | 2025-03-09 20:43:33 | MASTER-Kislovodsk | (02h 47m 28.55s , +38d 42m 35.0s) | C | 80 | 15.7 | 72240 | 2025-03-09 20:43:33 | MASTER-Kislovodsk | (02h 47m 28.54s , +38d 42m 34.9s) | C | 300 | 16.1 | Coadd 72240 | 2025-03-09 20:45:13 | MASTER-Kislovodsk | (02h 47m 28.42s , +38d 42m 25.5s) | C | 100 | 15.8 | 72370 | 2025-03-09 20:47:13 | MASTER-Kislovodsk | (02h 47m 28.29s , +38d 42m 16.6s) | C | 120 | 15.7 | 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/39640. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37655] GRB250309B: One candidate counterpart from the Zwicky Transient Facility
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39639 SUBJECT: GRB250309B: One candidate counterpart from the Zwicky Transient Facility DATE: 25/03/09 18:25:09 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Tomas Ahumada (Caltech), Jannis Necker, Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum), Jesper Sollerman (Stockholm) report: On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: We observed the localisation of Gamma-Ray Burst GRB 250309B (McDermott et al., GCN 39635) with the Palomar 48-inch telescope equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). This GRB was reported to be in spatial/temporal coincidence with high-energy neutrino IC250309A (Zegarelli et. al, GCN 39631), and our observations included ToO observations (Stein et al., GCN 39638) conducted as part of the ZTF neutrino follow up program (Stein et al. 2023). We started serendiptious observations of the GRB skymap in the g- and r-band beginning at 2025-03-09 07:51 UTC, approximately 0.3 hours after event time. We covered 80% of the reported localization region. This estimate accounts for chip gaps. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). After applying standard candidate vetting procedures, we identified the following candidate optical afterglow: ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF25aaitvjt | AT2025dws | 210.801761 | -8.502842 | r | 18.48| 0.107 | ±–––––––––––––––––––––––––––––––––––––––-+ Using the smaller BALROG localisation (Greiner et al, GCN 39629), we covered 76.8% (1.9 sq deg) of the reported localization region. This estimate accounts for chip gaps. Repeating the same search, AT2025dws is again the only candidate found within the error contour of the GRB. AT2025dws is red (g−r>0.4 mag) and is coincident with a faint Legacy Survey source that appears to be a possible host galaxy. From the ATLAS forced photometry service, we find that the transient had deeper upper limit (m>19.2) 1.67 hours before the GRB trigger. This suggests that AT2025dws is both fast-evolving, and temporally coincident with the GRB. Given this, we consider AT2025dws to be the likely afterglow counterpart. We encourage spectroscopic observations to confirm the nature of AT2025dws as an afterglow. ToO observations have been requested with the Neil Gehrels Swift Observatory. We note that none of ZTF25aaitvjt/AT2025dws is located 2.24 degrees from the center of the neutrino localisation. If this is indeed the afterglow, then the offset to the reported neutrino uncertainty region is >5 sigma, suggesting that the neutrino and GRB are not associated. We will continue to observe this field as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). 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), Caltech/IPAC, and the University of Washington at Seattle, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39639. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37654] IceCube-250309A: No candidates from the Zwicky Transient Facility
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39638 SUBJECT: IceCube-250309A: No candidates from the Zwicky Transient Facility DATE: 25/03/09 18:24:08 GMT FROM: Robert David Stein at JSI <rdstein(a)umd.edu> Robert Stein (JSI), Jannis Necker, Akshay Eranhalodi (DESY), and Anna Franckowiak (Ruhr University Bochum), Tomas Ahumada (Caltech), Jesper Sollerman (Stockholm) report: On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-250309A (Zegarelli et. al, GCN 39631) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started deep observations in the g- and r-band beginning at 2025-03-09 10:16 UTC while the same field was also observed by the routine ZTF survey at 08:18 UTC, approximately 0.7 hours after event time. We covered 92.9% (0.3 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019). We are left with one candidate within the 90.0% localization of the skymap. ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF Name | IAU Name | RA (deg) | DEC (deg) | Filter | Mag | MagErr | ±–––––––––––––––––––––––––––––––––––––––-+ | ZTF25aaiurnn | –––- | 211.3537073 | -10.4938701 | g | 20.82 | 0.18 | ±–––––––––––––––––––––––––––––––––––––––-+ ZTF25aaiurnn was first detected on 2025-03-02 in the r-band, roughly one week before the neutrino arrival. It has a match in the MILLIQUAS catalog at a distance of 0.18 arcsec as a 95% probable QSO. The match in the AllWISE source catalog (WISEA J140524.90-102938.0, 0.22 arcsec) shows a red color of W1-W2=1), consistent with an AGN. Although there is only one detection per band, there is no clear evidence for coincident flaring activity. We will continue to observe this field as part of our standard ToO cadence for high-energy neutrinos (Stein et al. 2023). 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), Caltech/IPAC, and the University of Washington at Seattle, USA. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/39638. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37653] Fermi-LAT gamma-ray observations of IceCube-250309A
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39637 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-250309A DATE: 25/03/09 17:38:48 GMT FROM: Sara Buson at DESY, Univ. of Wurzburg <sara.buson(a)gmail.com> S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science), L. Pfeiffer (Univ. of Wuerzburg), N. Di Lalla (Stanford Univ.), M. Arimoto (Kanazawa University), R. Gupta (NASA GSFC) and A. Holzmann Airasca (UniTrento and INFN Bari) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250309A neutrino event (GCN 39631) with all-sky survey data from the Large Area Telescope (LAT) on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 2025-03-09 07:36:04.75 UTC (T0) with J2000 position RA = 211.07 (+0.31, -0.30) deg, Decl. = -10.73 (+0.26, -0.30) deg 90% PSF containment. No cataloged gamma-ray sources are found within the 90% IC250309A localization error (The Fourth Fermi-LAT catalog, 4FGL-DR4, The Fermi-LAT collaboration 2023, arXiv:2307.12546). We searched for the existence of intermediate (days to years) timescale emission from a new gamma-ray transient source. Preliminary analysis indicates no significant (>5sigma) new excess emission (> 100 MeV) within the IC250309A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IceCube best-fit position, the >100 MeV flux upper limit (95% confidence) is <2.4e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <6.8e-09 (<9.3 e-8) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. The IceCube event IC250309A occurred near the GRB 250309B (GCN 39635), with a detection time 145.91 seconds after the Fermi-GBM trigger and a positional separation of 0.50 deg. An analysis of the LAT data conducted over a ±1000-second window centered on T0, shows no significant excess emission, neither associated with IC250309A nor GRB 250309B. The >100 MeV flux upper limit (95% confidence) at IC250309A best-fit position for this time interval is < 5.3 e-6 ph cm^-2 s^-1. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this source will continue. For this source, the Fermi-LAT contact person is S. Buson (sara.buson at uni-wuerzburg.de). The Fermi LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/39637. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37652] GRB 250308A: SVOM/GRM detection of QPO in the tail emission
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39636 SUBJECT: GRB 250308A: SVOM/GRM detection of QPO in the tail emission DATE: 25/03/09 16:00:23 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Wen-Jun Tan, Zheng-Hang Yu, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Nicolas Dagoneau (CEA), Maria-Grazia Bernardini (INAF-OAB), Jean-Luc Atteia (IRAP), Frédéric Piron (LUPM) Report on behalf of the SVOM team: The bright short burst, GRB 250308A (GCN #39632), consists of a narrow spike followed by a short tail emission (from T0-0.15 to T0+0.15 s), which shows a feature of QPO, with a center frequency at approximately 31 Hz. The on-ground localization of this burst is (J2000): RA: 170.9 deg DEC: 25.6 deg Error: 5.2 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. With this localization, the time-averaged spectrum from T0-0.3 to T0+0.2 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.28 +/- 0.04 and the cutoff energy, parameterized as Epeak, is 452 +/- 56 keV. The event fluence (10-1000 keV) in this time interval is (4.9 +/- 0.2)E-06 erg/cm^2. The feature of QPO in the tail emission and the spectrum parameters are consistent with the scenario of magnetar giant flare. Follow-up observations are strongly encouraged. We note that these results are preliminary. Refined analysis will be reported later. The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM/GRM point of contact for this burst is: Chen-Wei Wang (IHEP) (cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/39636. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37651] GRB 250309B: Fermi GBM Final Localization
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39635 SUBJECT: GRB 250309B: Fermi GBM Final Localization DATE: 25/03/09 15:47:40 GMT FROM: Padraig McDermott at University College Dublin <padraig.mcdermott(a)ucdconnect.ie> The Fermi GBM team reports the detection of a likely LONG GRB "At 07:38:30.66 UT on 09 March 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250309B (trigger 763198715/250309318). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 210.58, Dec = -10.86 (J2000 degrees, equivalent to J2000 14h 02m, -10d 51'), with a statistical uncertainty of 1.2 degrees. The angle from the Fermi LAT boresight is 77 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250309318/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/39635. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37650] Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A!
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39634 SUBJECT: Correction to GCN 39633 - Swift is observing GRB 250309B/IceCube-250309A! DATE: 25/03/09 13:20:55 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> P.A. Evans reports on behalf of the Swift-XRT team, There was an error in GCN Circ. 39633 — Swift is not observing a 22-month old GRB, but is in fact observing combined error locatlisation of GRB 250309B and IceCube 250309A. Apologies for any confusion caused by my errant fingers, and thanks to Kim Page for spotting this. We will request a correction in the GCN archives. View this GCN Circular online at https://gcn.nasa.gov/circulars/39634. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37649] GRB 230509B: Tiled Swift observations
by GCN Circulars 09 Mar '25

09 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39633 SUBJECT: GRB 230509B: Tiled Swift observations DATE: 25/03/09 13:15:21 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 series of observations, tiled on the sky, of the Fermi/GBM GRB 230509B. Automated analysis of the XRT data will be presented online at http://www.swift.ac.uk/xrt_products/TILED_GRB00134 Any uncatalogued X-ray sources detected in this analysis will be reported on this website and via GCN COUNTERPART notices. The probability of finding serendipitous sources, unrelated to the Fermi/GBM event is high: 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/39633. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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