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

[vsnet-grb-info 38276] IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube
by GCN Circulars 25 Apr '25

25 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40247 SUBJECT: IceCube-250421A: Upper limits from a search for additional neutrino events in IceCube DATE: 25/04/25 14:18:59 GMT FROM: Jessie Thwaites at IceCube/U Wisc-Madison <thwaites(a)wisc.edu> The IceCube Collaboration (http://icecube.wisc.edu/) reports: IceCube has performed a search [1] for additional track-like muon neutrino events arriving from the direction of IceCube-250421A (https://gcn.nasa.gov/circulars/40195) in a time range of 1000 … [View More]

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[vsnet-grb-info 38275] GRB 250424A: SVOM/VT optical observation
by GCN Circulars 25 Apr '25

25 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40246 SUBJECT: GRB 250424A: SVOM/VT optical observation DATE: 25/04/25 11:38:33 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z.H. Yao(NAOC), X. H. Han(NAOC), Y. D. Hu(GXU),L. Zhang(IHEP), X. L. Chen(YNU), L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, Y. J. Xiao, H. B. Cai, L. Lan, J. Y. Wei (NAOC) report on behalf of the SVOM mission team. SVOM/VT conducted ToO follow-up observations of the GRB 250424A(… [View More]

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[vsnet-grb-info 38274] GRB 250419A: Mondy Optical Observations
by GCN Circulars 25 Apr '25

25 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40245 SUBJECT: GRB 250419A: Mondy Optical Observations DATE: 25/04/25 07:34:22 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), A. Pozanenko (IKI), E. Klunko (ISTP) report on behalf of IKI-GRB-FuN: We continued observations of the field of GRB 250419A (Wang et al., GCN 40168; Page et al., GCN 40111; Page et al., GCN 40176) at the redshift of z = 0.845 (Thakur et al., GCN 40174) with the 1.5-meter AZT-33IK … [View More]

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[vsnet-grb-info 38273] GRB 250424A: Swift/UVOT Detection
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40244 SUBJECT: GRB 250424A: Swift/UVOT Detection DATE: 25/04/24 23:09:21 GMT FROM: Mike Siegel at PSU/Swift MOC <mhs18(a)psu.edu> M.H. Siegel (PSU) and S. B. Cenko (GSFC) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250424A 254 s after the BAT trigger (Cenko et al., GCN Circ. 40224). A source consistent with the XRT position (Evans et al., GCN Circ. 40232) and the optical transient (Francile … [View More]

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[vsnet-grb-info 38272] Konus-Wind detection of GRB 250424A
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40243 SUBJECT: Konus-Wind detection of GRB 250424A DATE: 25/04/24 22:12:37 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB GRB 250424A (Swift-BAT detection: Cenko et al., GCN 40224; AstroSat CZTI detection: Harsha et al., GCN 40231) triggered Konus-Wind at T0=24733.431 s UT (06:… [View More]52:13.431). The burst light curve shows a single pulse which starts at ~T0-17.9 s and has a total duration of ~40.5 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/ As observed by Konus-Wind, the burst had a fluence of 5.83(-0.16,+0.16)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.192 s, of 8.88(-0.94,+0.95)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+21.760 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.30(-0.06,+0.06), the high energy photon index beta = -2.87(-0.15,+0.11), the peak energy Ep = 104(-3,+3) keV (chi2 = 94/82 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+5.376 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.09(-0.06,+0.07), the high energy photon index beta = -2.91(-0.15,+0.12), the peak energy Ep = 129(-4,+5) keV (chi2 = 72/66 dof). Assuming the redshift z=0.310 (Saccardi et al., GCN 40228) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 1.49(-0.04,+0.04)x10^52 erg, the peak luminosity L_iso is 2.97(-0.31,+0.32)x10^51 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 137(-4,+4) keV and the spectrum near the maximum count rate Ep,p,z is 169(-5,+7) keV. With the obtained estimates, GRB 250424A is inside 68% prediction bands for both 'Amati' and 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/GRB250424A_rest_frame.pdf All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40243. --- 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 38271] Konus-Wind detection of GRB 250424A
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40243 SUBJECT: Konus-Wind detection of GRB 250424A DATE: 25/04/24 22:12:37 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB GRB 250424A (Swift-BAT detection: Cenko et al., GCN 40224; AstroSat CZTI detection: Harsha et al., GCN 40231) triggered Konus-Wind at T0=24733.431 s UT (06:… [View More]52:13.431). The burst light curve shows a single pulse which starts at ~T0-17.9 s and has a total duration of ~40.5 s. The emission is seen up to ~2 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/ As observed by Konus-Wind, the burst had a fluence of 5.83(-0.16,+0.16)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+4.192 s, of 8.88(-0.94,+0.95)x10^-6 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+21.760 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.30(-0.06,+0.06), the high energy photon index beta = -2.87(-0.15,+0.11), the peak energy Ep = 104(-3,+3) keV (chi2 = 94/82 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+5.376 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.09(-0.06,+0.07), the high energy photon index beta = -2.91(-0.15,+0.12), the peak energy Ep = 129(-4,+5) keV (chi2 = 72/66 dof). Assuming the redshift z=0.310 (Saccardi et al., GCN 40228) and a standard cosmology with H_0 = 67.3 km/s/Mpc, Omega_M = 0.315, and Omega_Lambda = 0.685 (Planck Collaboration, 2014), we estimate the following rest-frame parameters: the isotropic energy release E_iso is 1.49(-0.04,+0.04)x10^52 erg, the peak luminosity L_iso is 2.97(-0.31,+0.32)x10^51 erg/s, the rest-frame peak energy of the time-averaged spectrum Ep,i,z is 137(-4,+4) keV and the spectrum near the maximum count rate Ep,p,z is 169(-5,+7) keV. With the obtained estimates, GRB 250424A is inside 68% prediction bands for both 'Amati' and 'Yonetoku' relations derived for the sample of >300 long KW GRBs with known redshifts (Tsvetkova et al., 2017; Tsvetkova et al., 2021), see http://www.ioffe.ru/LEA/GRBs/GRB250424_T24733/GRB250424A_rest_frame.pdf All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/40243. --- 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 38270] Fermi-LAT gamma-ray observations of IceCube-250421A
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40242 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-250421A DATE: 25/04/24 20:30:21 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the IC250421A high-energy neutrino event (GCN 40195) with all-sky survey … [View More]data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-04-21 at 17:06:08.07 UT (T0) with J2000 position RA = 240.91 (+2.62, -4.44) deg, Decl. = +28.67 (+1.70, -1.70) deg (90% PSF containment). There are five catalogued gamma-ray sources (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546) located within the 90% IC250421A localization region. These are: 4FGL J1606.5+2717, associated with B2 1604+27; 4FGL J1556.1+2812, associated with NVSS J155611+281134; 4FGL J1612.2+2828, associated with TXS 1610+285; 4FGL J1545.5+2839, associated with WISEA J154520.76+283508.6; 4FGL J1555.3+2903 (unassociated). Based on a preliminary analysis of the LAT data over the timescale of one day and one month prior T0, these objects are not significantly detected at gamma-rays. 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) at the IC250421A bestfit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250421A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.21 e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), < 4.61e-09 (<1.01e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Within the error circle for the direction of the neutrino, 1.39 deg offset from the best-fitIC250421 position, a ~14 sigma excess of gamma rays, Fermi J1605.3+2959, was detected in an analysis of the integrated LAT data (0.1 - 300 GeV) between 2008-08-04 and T0. Assuming a power-law spectrum, the candidate gamma-ray source has best-fit localization of RA = 241.39 deg, Dec = +30.00 deg (0.16 deg 99% containment, 0.13 deg 95% containment, 0.08 deg 68% containment) with best fit spectral parameters flux = (1.20± 0.12) × 10^-8 ph cm^-2 s^-1, index = 3.18 ± 0.23. A possible counterpart for Fermi J1605.3+2959 is the FSRQ CGRaBS J1605+3001 (a.k.a. BZQ J1605+3001, Stephen E. & Healey et al 2007, ApJS, 171, 61) with a redshift of 2.41 (Sloan Digital Sky Survey 2017, ApJS, 233, 25), located at 0.03 deg from the Fermi J1605.3+2959 best-fit position, within the 68% localization error. A preliminary analysis of the temporal variability at the position of Fermi J1605.3+2959 reveals that the source underwent an approximately six-months long period of enhanced activity between late 2023 and early 2024. In addition, in a preliminary analysis of the LAT data over 1-month timescale, we test the presence of an additional point source at the position of the optical transient SN2025cbj, a ~60-days old SN of Type-IIn which was reported in spatial coincidence with IC250421A in GCN#40208. No significant gamma-ray emission was detected. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the SN2025cbj best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.13e-08 ph cm^-2 s^-1 for a 1-month integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For these observations 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/40242. --- 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 38269] Fermi-LAT gamma-ray observations of IceCube-250421A
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40242 SUBJECT: Fermi-LAT gamma-ray observations of IceCube-250421A DATE: 25/04/24 20:30:21 GMT FROM: Leo Pfeiffer at University of Würzburg <pfeiffer.leo(a)gmail.com> L. Pfeiffer (Univ. of Wuerzburg), S. Buson (DESY, Univ. of Wuerzburg), S. Garrappa (Weizmann Institute of Science) on behalf of the Fermi-LAT collaboration: We report an analysis of observations of the vicinity of the IC250421A high-energy neutrino event (GCN 40195) with all-sky survey … [View More]data from the Large Area Telescope (LAT), on board the Fermi Gamma-ray Space Telescope. The IceCube event was detected on 25-04-21 at 17:06:08.07 UT (T0) with J2000 position RA = 240.91 (+2.62, -4.44) deg, Decl. = +28.67 (+1.70, -1.70) deg (90% PSF containment). There are five catalogued gamma-ray sources (4FGL-DR4; The Fourth Fermi-LAT catalog Data Release 4, The Fermi-LAT collaboration 2023, arXiv:2307.12546) located within the 90% IC250421A localization region. These are: 4FGL J1606.5+2717, associated with B2 1604+27; 4FGL J1556.1+2812, associated with NVSS J155611+281134; 4FGL J1612.2+2828, associated with TXS 1610+285; 4FGL J1545.5+2839, associated with WISEA J154520.76+283508.6; 4FGL J1555.3+2903 (unassociated). Based on a preliminary analysis of the LAT data over the timescale of one day and one month prior T0, these objects are not significantly detected at gamma-rays. 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) at the IC250421A bestfit position. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the IC250421A best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.21 e-10 ph cm^-2 s^-1 for ~16-years (2008-08-04 / T0), < 4.61e-09 (<1.01e-07) ph cm^-2 s^-1 for a 1-month (1-day) integration time before T0. Within the error circle for the direction of the neutrino, 1.39 deg offset from the best-fitIC250421 position, a ~14 sigma excess of gamma rays, Fermi J1605.3+2959, was detected in an analysis of the integrated LAT data (0.1 - 300 GeV) between 2008-08-04 and T0. Assuming a power-law spectrum, the candidate gamma-ray source has best-fit localization of RA = 241.39 deg, Dec = +30.00 deg (0.16 deg 99% containment, 0.13 deg 95% containment, 0.08 deg 68% containment) with best fit spectral parameters flux = (1.20± 0.12) × 10^-8 ph cm^-2 s^-1, index = 3.18 ± 0.23. A possible counterpart for Fermi J1605.3+2959 is the FSRQ CGRaBS J1605+3001 (a.k.a. BZQ J1605+3001, Stephen E. & Healey et al 2007, ApJS, 171, 61) with a redshift of 2.41 (Sloan Digital Sky Survey 2017, ApJS, 233, 25), located at 0.03 deg from the Fermi J1605.3+2959 best-fit position, within the 68% localization error. A preliminary analysis of the temporal variability at the position of Fermi J1605.3+2959 reveals that the source underwent an approximately six-months long period of enhanced activity between late 2023 and early 2024. In addition, in a preliminary analysis of the LAT data over 1-month timescale, we test the presence of an additional point source at the position of the optical transient SN2025cbj, a ~60-days old SN of Type-IIn which was reported in spatial coincidence with IC250421A in GCN#40208. No significant gamma-ray emission was detected. Assuming a power-law spectrum (photon index = 2.0 fixed) for a point source at the SN2025cbj best-fit position, the >100 MeV flux upper limit (95% confidence) is < 1.13e-08 ph cm^-2 s^-1 for a 1-month integration time before T0. Since Fermi normally operates in an all-sky scanning mode, regular monitoring of this region will continue. For these observations 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/40242. --- 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 38268] GRB 250424A: Skynet Optical Observations
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40241 SUBJECT: GRB 250424A: Skynet Optical Observations DATE: 25/04/24 20:17:01 GMT FROM: Dylan Dutton at UNC Chapel Hill <ddutton59(a)gmail.com> Dylan Dutton, Daniel Reichart, Joshua Haislip, Vladimir Kouprianov, and Donovan Schlekat report on behalf of the Skynet Robotic Telescope Network at the University of North Carolina at Chapel Hill. We observed the field of GRB 250424A detected by Swift (Cenko, GCN 40224) with one of Skynet's PROMPT … [View More]

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[vsnet-grb-info 38267] GRB 250424A: Kilonova-Catcher optical afterglow detection
by GCN Circulars 24 Apr '25

24 Apr '25

TITLE: GCN CIRCULAR NUMBER: 40240 SUBJECT: GRB 250424A: Kilonova-Catcher optical afterglow detection DATE: 25/04/24 18:25:31 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin (CEA-Saclay/Irfu), R. Hellot, P. Jaquiery, M. Freeberg (KNC), C. Andrade(UMN), S. Antier (OCA), M. Coughlin (UMN),S. Karpov (FZU), I. Tosta e Melo (UniCT-DFA), P. Hello (IJCLAB), P-A Duverne (APC), T. Pradier (Unistra/IPHC), N. Guessoum (AUS), M. Pillas (ULiege) on behalf of the … [View More]GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250424A (Cenko et al., GCN 40224) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the iT30 telescope at the Siding Spring Observatory, a Celestron C14 telescope at Beverly Begg Observatory (New Zealand) and a CDK17 telescope located at AITP San Pedro Chile Observatory starting from TGRB+1.3hr. In our stacked frames, subtracted from the Legacy Survey DR10 template image, we detect the optical afterglow at the position reported by Swift/UVOT (Cenko et al., GCN 40224), REM (Brivio et al., GCN 40225), DDOTI (Becerra et al., GCN 40226), VLT/X-Shooter (Saccardi et al., GCN 40228), BlackGEM (de Wet et al., GCN 40229)and COLIBRI (Ducoin et al., GCN 40230). We report some of our detections in the table below: +---------------+-----------+-----------+----------------+------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+===========+===========+================+============+ | 1.3 | 1 x 300s | r (AB) | 19.34 +/- 0.09 | CDK17-AITP | | 4.0 | 20 x 120s | r (AB) | 19.74 +/- 0.07 | C14-BBO | | 6.8 | 17 x 180s | Rc (Vega) | 19.95 +/- 0.09 | iT30 | +---------------+-----------+-----------+----------------+------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained in Johnson Cousin filters were calibrated using the Gaia DR3 Synphot catalog while the sloan images were calibrated using the SkyMapper DR4 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/). View this GCN Circular online at https://gcn.nasa.gov/circulars/40240. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L… [View Less]

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