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

[vsnet-grb-info 38156] EP250227a: Further NOT optical observations
by GCN Circulars 10 Apr '25

10 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40132 SUBJECT: EP250227a: Further NOT optical observations DATE: 25/04/10 09:17:11 GMT FROM: Daniele B. Malesani at IMAPP / Radboud University <d.malesani(a)astro.ru.nl> D. B. Malesani (DAWN/NBI and Radboud), J. Sanchez-Sierras (Radboud), P. G. Jonker (Radboud), A. Martin-Carrillo (UCD), A. J. Levan (Radboud and Warwick), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration: We obtained ten 300-s observations in the r … [View More]

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[vsnet-grb-info 38155] GRB 250320B: cubesat Avion detection
by GCN Circulars 10 Apr '25

10 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40131 SUBJECT: GRB 250320B: cubesat Avion detection DATE: 25/04/10 08:46:40 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2025-03-20 ~23:15:22 UT the long-duration GRB 250320B (Fermi GBM detection: GCN #39792; SVOM detection: GCN #39813, AstroSat CZTI detection: GCN #39808) was detected by the … [View More]

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[vsnet-grb-info 38154] IceCube-250406A: Swift-XRT observations
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40130 SUBJECT: IceCube-250406A: Swift-XRT observations DATE: 25/04/09 14:22:44 GMT FROM: P.A. Evans at U. Leicester <pae9(a)leicester.ac.uk> P.A. Evans (U. Leicester) and J.A. Kennea (PSU) report on behalf of the Swift-XRT team, Swift-XRT observed the field of IceCube-250406A (IceCube Collaboration, GCN 40103) between 22:21 UT on 2025 April 7 and 03:36 UT on 2025 April 8 (85 to 104 ks after the trigger), gathering 4.1 ks over 7 pointings centred on … [View More]the position from the refined position notice. Three X-ray sources are detected, all of which have counterparts in the 1RXS Rosat catalogue (Voges et al., 1999) and show no sign of elecated flux compared to those data. The sources are: Source 1: Swift J052456.1+170357 at RA, Dec = 81.23375, +17.0660 which is equivalent to: RA (J2000): 05h 24m 56.10s Dec (J2000): +17d 03' 57.8" with an uncertainty of 4.7 arcsec (radius, 90% confidence), and consistent with the position of 1RXS J052456.3+170400. The mean 0.3-10 keV count-rate is 0.030 (+/-0.007) ct/sec, which corresponds to 1.3 (+/-0.3) x 10^-12 erg/cm^2/s. Source 2: Swift J052427.1+172323 at RA, Dec = 81.11301, +17.3898 which is equivalent to: RA (J2000): 05h 24m 27.12s Dec (J2000): +17d 23' 23.2" with an uncertainty of 5.7 arcsec (radius, 90% confidence), and consistent with the position of 1RXS J052425.7+172301. The mean 0.3-10 keV count-rate is 0.051 (+0.016, -0.013) ct/sec, which corresponds to 2.2 (+0.7, -0.6) x 10^-12 erg/cm^2/s. Source 3: Swift J052425.1+172240 at RA, Dec = 81.10483, +17.3780 which is equivalent to: RA (J2000): 05h 24m 25.16s Dec (J2000): +17d 22' 40.9" with an uncertainty of 8.0 arcsec (radius, 90% confidence), and consistent with the position of 1RXS J052425.7+172301 . The mean 0.3-10 keV count-rate is 0.042 (+0.015, -0.012) ct/sec, which corresponds to 1.8 (+0.6, -0.5) x 10^-12 erg/cm^2/s. Note that sources 2 and 3 correspond to the same Rosat source (due to the comparitively large Rosat position errors). In fact, neither source looks particularly point-like and both are within 30" of * 111 Tau -- a fifth magnitude BY Dra star. At this brightness the star will cause optical loading -- the detection of spurious 'X-rays' which are actually an accumulation of optical photons. We therefore view both of these sources with scepticism. A fourth source is also detected, Swift J052440.8+163236 at RA, Dec = 81.17009, 16.5435 degrees and an uncertainty of 8.4 arcsec (radius, 90% confidence). However, this is classified "poor" which corresponds approximately to a 1-sigma detection and is thus likely spurious. The full XRT analysis can be viewed online at https://www.swift.ac.uk/neutrino/NEUTRINO_FIELD00043/. View this GCN Circular online at https://gcn.nasa.gov/circulars/40130. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38153] IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a)
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40129 SUBJECT: IPN triangulation of GRB 250321D (consistent with the fast X-ray transient EP250321a) DATE: 25/04/09 14:22:43 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> D. Svinkin, D. Frederiks, A. Ridnaia, A. Lysenko, and T. Cline on behalf of the Konus-Wind team, E. Burns on behalf of the IPN, and E. Bozzo, C. Ferrigno, and S. Mereghetti on behalf of the INTEGRAL SPI-ACS GRB team, report: The long-duration GRB 250321D … [View More]

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[vsnet-grb-info 38152] AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40128 SUBJECT: AMON Coincidence Alert from the sub-threshold IceCube-HAWC search NuEm-250409A DATE: 25/04/09 12:52:44 GMT FROM: Hugo Ayala at Pennsylvania State University <hgayala(a)psu.edu> The AMON, IceCube, and HAWC collaborations report: The AMON NuEm stream channel found a coincidence alert from the IceCube online neutrino selection + HAWC daily monitoring analysis. The analysis looks for IceCube neutrino events -mostly atmospheric in origin- … [View More]

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[vsnet-grb-info 38151] IPN triangulation of GRB 250407A
by GCN Circulars 09 Apr '25

09 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40127 SUBJECT: IPN triangulation of GRB 250407A DATE: 25/04/09 07:14:45 GMT FROM: Dmitry Svinkin at Ioffe Institute <svinkin(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the MGNS/BepiColombo team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi GBM team, report: … [View More]

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[vsnet-grb-info 38150] EP250407a: Global MASTER-Net observations report
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40126 SUBJECT: EP250407a: Global MASTER-Net observations report DATE: 25/04/08 23:27:52 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.… [View More]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-OAFA robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP250407a ( EP Team et al., GCN 40118) errorbox 49972 sec after notice time and 85240 sec after trigger time at 2025-04-08 23:08:03 UT, with upper limit up to 18.5 mag. Observations started at twilight. The observations began at zenith distance = 18 deg. The sun altitude is -10.6 deg. The galactic latitude b = 5 deg., longitude l = 262 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2836941 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 85271 | 2025-04-08 23:08:03 | MASTER-OAFA | (08h 59m 01.05s , -38d 53m 39.6s) | C | 60 | 18.2 | 85448 | 2025-04-08 23:11:01 | MASTER-OAFA | (08h 59m 05.07s , -38d 53m 10.9s) | C | 60 | 18.5 | 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/40126. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38149] GRB 250407A: LCO detection of a fading optical counterpart
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40125 SUBJECT: GRB 250407A: LCO detection of a fading optical counterpart DATE: 25/04/08 21:48:17 GMT FROM: Ismael Perez-Fournon at Instituto de Astrofisica de Canarias <ipf(a)iac.es> I. Pérez-Fournon, F. Poidevin (IAC and ULL), D. Cano-Morales, A.E. Hernández-Díaz, I. Correa-Plasencia (ULL), and A. López-Oramas (IAC and ULL) Following the detection by Fermi GBM of the bright and likely long Gamma-Ray Burst GRB 250407A (Fermi GBM team, GCN circ. … [View More]40104; Preis and Greiner, GCN circ. 40105; and Mukherjee et al., GCN circ. 40114) and the associated X-ray afterglow by SRG/ART-XC (Molkov et al., GCN circ. 40110), we observed the field with the two Las Cumbres Observatory Global Telescope network (LCOGT) 1-m telescopes, equipped with Sinistro cameras, located at the LCOGT node at Teide Observatory (Tenerife, Spain) in the SDSS g, r, and i filters. The observations started at 2025-04-07 21:06:04 UTC, about 5.29 hours after the Fermi trigger. We detect the optical afterglow in the r and i filters, but not in the g filter, at the position reported by Zheng and Filippenko (GCN circ. 40116) and Ducoin et al. (GCN circ. 40117), that is consistent within the errors with the SRG/ART-XC (Molkov et al., GCN circ. 40110), Swift-XRT (Dichiara et al., GCN circ. 40113) and EP-WXT (Zheng et al., GCN circ. 40119) X-ray afterglow positions. GRB 250407A has also been detected by SVOM/GRM (Wang et al., GCN circ. 40120) and Konus-Wind (Frederiks et al., GCN circ. 40121). A fading of the optical brightness between our LCOGT observations and those of KAIT (Zheng and Filippenko, GCN circ. 40116) and COLIBRÍ/DDRAGO (Ducoin et al., GCN circ. 40117) is detected. We measure the following preliminary r and i magnitudes and limiting (5-sigma) g-band magnitude, calibrated against Pan-STARRS DR2 stars, that are not corrected for Galactic extinction: Date | UT start | mag | error | filter | exposure time (sec) | limiting magnitude (5 sigma) ------------------------------------------------------------------------------------------------------ 2025-04-07 21:06:04 19.67 0.11 r 300 ----- 2025-04-07 21:10:26 ----- ---- g 180 20.45 2025-04-07 22:01:01 19.92 0.20 r 180 ----- 2025-04-07 22:15:32 19.53 0.19 i 180 ----- This work makes use of observations from the Las Cumbres Observatory global telescope network (LCOGT observing programme IAC2025A-009, SGLF). View this GCN Circular online at https://gcn.nasa.gov/circulars/40125. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38148] Fermi-LAT gamma-ray observations of IceCube-250406A
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40124 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-250406A DATE: 25/04/08 19:44:10 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), C. Bartolini (INFN Bari), S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the high-energy IC250406A neutrino event (GCN … [View More]40103) 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 2025-04-06 at 22:50:35.34 UTC (T0) with J2000 position RA = 81.47 (+0.54, -0.53) deg, Decl. = 16.96 (+0.42, -0.50) deg 90% PSF containment (J2000). No cataloged gamma-ray sources are found within the 90% IC250406A localization error (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, 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 IC250406A 90% confidence localization. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250406A best-fit position, the >100 MeV flux upper limit (95% confidence) is <1.72e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), <2.13e-08 (<1.58e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. The closest catalogued gamma-ray source to the IC250406A best-fit position is 4FGL J0521.2+1637 (The Fermi-LAT collaboration 2020, ApJS, 247, 33), associated with the compact steep spectrum quasar 3C 138, located approximately 1.15° away from the IceCube event, outside the 90% neutrino localization region. Since October 2024, the source has exhibited strong and prolonged gamma-ray flaring activity (see ATel #16845, ATel #17107). A preliminary analysis confirms that this enhanced activity is ongoing, with a daily averaged gamma-ray flux (E > 100 MeV) of (0.39± 0.29) × 10^-6 photons cm^-2 s^-1 (statistical uncertainty only), as observed on April 6, 2025. This represents an increase in flux by a factor of approximately 93 compared to the average flux reported in the 4FGL-DR4. 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 L. Pfeiffer (leonard.pfeiffer 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/40124. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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[vsnet-grb-info 38147] EP250407a: Swift-XRT observations
by GCN Circulars 08 Apr '25

08 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40123 SUBJECT: EP250407a: Swift-XRT observations DATE: 25/04/08 19:20:26 GMT FROM: Maia Williams at PSU <mjw6837(a)psu.edu> M. A. Williams (PSU), S. Dichiara (PSU), K.L. Page (U. Leicester) and P.A. Evans (U. Leicester) report on behalf of the Swift-XRT team: We have analyzed 2100 s of XRT data for the recently reported transient EP250407a (GCN #40118), from T0+36.5 ks to T0+42.4 ks after detection by Einstein Probe WXT. The data are entirely in … [View More]

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vsnet-grb-info April 2025