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

[vsnet-grb-info 37678] GRB 250311B: SVOM detection of a burst
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39662 SUBJECT: GRB 250311B: SVOM detection of a burst DATE: 25/03/11 08:25:41 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C.W. Wang (IHEP), R.C. Chen (NJU), H. Goto, D. Turpin (CEA), M. G. Bernardini (INAF-OAB, LUPM) on behalf of the SVOM mission team. At 2025-03-11T07:08:05.065 UTC (Tb) SVOM/ECLAIRs triggered on the gamma-ray burst GRB 250311B (SVOM burst-id sb25031101). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was only detected by the Count rate Trigger (CRT), from which we received 1 alert. CRT provided the alert with the best signal-to-noise-ratio (SNR) of 7.45 in the [8-120] keV energy band over a time window of 10.2 seconds starting at Tb. The localization of the best alert is R.A., Dec 146.885, 29.891 degrees: RA (J2000) = 9h47m32.36s Dec (J2000) = 29d53m26.62s with a 90% C.L. radius of 10.53 arcmin (including systematic error of 2 arcmin added in quadrature). No immediate slew was performed on this burst. A SVOM ToO has been requested. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. The Burst Advocate (BA) on shift for this burst is C.W. Wang: cwwang(a)ihep.ac.cn. Please contact the BA by email if you require additional information regarding the SVOM follow-up of this burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/39662. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37677] GRB 250309B: SVOM/VT optical observation
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39661 SUBJECT: GRB 250309B: SVOM/VT optical observation DATE: 25/03/11 06:47:44 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Z. M. Wang, A. Li (BNU), Y. F. Liang (PMO), L. P. Xin, Y. L. Qiu, H. L. Li, Z. H. Yao, Y. Xu, P. P. Zhang, W. J. Xie, J. Wang, X. H. Han, Y. J. Xiao, H. B. Cai, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM team: The SVOM/VT conducted a ToO follow-up observation of ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639) which is considered as the optical candidate of Fermi GRB 250309B (Preis & Greiner, GCN 39629; McDermott et al., GCN 39635; McDermott et al., GCN circ. 39642) in VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously, The optical candidate ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639; Pérez-Fournon et al., GCN 39643; Stein and Ahumada, GCN 39644; Moskvitin et al., GCN 39645; Perley et al., GCN 39646; Malesani et al., GCN 39647; Ducoin et al., GCN 39650; Shin et al, GCN 39654) is clearly detected in images. The brightness in AB manigutude was estimated to be 20.20+/0.04 mag in VT_R, and 20.72+/-0.05 mag in VT_B stacked images, with an exposure time of 46*60 seconds, at the mid time of 0.974 days post the burst. 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. VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC),CAS. View this GCN Circular online at https://gcn.nasa.gov/circulars/39661. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37676] GRB 250311A/MAXI J1457-026: MAXI/GSC detection
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39660 SUBJECT: GRB 250311A/MAXI J1457-026: MAXI/GSC detection DATE: 25/03/11 03:47:32 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> K. Tatano, H. Negoro, M. Nakajima (Nihon U.), M. Serino, Y. Kawakubo (AGU), Y. Kudo, H. Shibui, K. Takagi, H. Takahashi, H. Nishio (Nihon U.), T. Mihara, S. Yamada, S. Wang, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, H. Hiramatsu, H. Nishikawa, Y. Kondo, S. Sasao, A. Yoshida (AGU), Y. Tsuboi, H. Sugai, N. Nagashima (Chuo U.), M. Shidatsu, Y. Niida (Ehime U.), I. Takahashi, M. Niwano, N. Higuchi, Y. Yatsu (Tokyo Tech), S. Nakahira, S. Ueno, H. Tomida, M. Ishikawa, S. Ogawa, M. Kurihara (JAXA), Y. Ueda, Y. Okada, K. Fujiwara (Kyoto U.), M. Yamauchi, Y. Otsuki, T. Hasegawa, M. Nishio (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), W. Iwakiri (Chiba U.), T. Kawamuro (Osaka U.) report on behalf of the MAXI team: The MAXI/GSC nova alert system triggered a bright uncatalogued X-ray transient source at 01:55:22 UT on March 11, 2025. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (224.318 deg, -2.613 deg) = (14 57 16, -02 36 46) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.33 deg and 0.28 deg, respectively. The roll angle of long axis from the north direction is 9.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 75 +- 18 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (223.607, -1.537) deg = (14 54 25, -01 32 13) (J2000) (223.164, -1.982) deg = (14 52 39, -01 58 55) (J2000) (225.099, -3.901) deg = (15 00 23, -03 54 03) (J2000) (225.542, -3.455) deg = (15 02 10, -03 27 18) (J2000) There was no significant excess flux in the previous transit at 00:22 UT and in the next transit at 03:28 UT with an upper limit of 20 mCrab for each. We note that the source position is consistent with the position of GRB 250305A reported by Fermi-GBM (#39597). We encourage follow-up observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/39660. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37675] The EP-WXT trigger 01709132425 is not a real source
by GCN Circulars 11 Mar '25

11 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39659 SUBJECT: The EP-WXT trigger 01709132425 is not a real source DATE: 25/03/11 02:14:26 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.L. Hua (PMO), Y. J. Zhang (THU), X. Mao, Z. X. Ling (NAO, CAS) report on behalf of the Einstein Probe team: Further analysis of the data suggests that the EP-WXT on-board trigger (ID: 01709132425) at 2025-03-10 18:42:15 (UTC) is not a real source. Launched on January 9, 2024, EP is a space X-ray observatory to monitor the soft X-ray sky with onboard X-ray follow-up capability (Yuan et al. 2022, Handbook of X-ray and Gamma-ray Astrophysics) View this GCN Circular online at https://gcn.nasa.gov/circulars/39659. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37674] GRB 250309B / AT2025dws: further SAO RAS optical observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39658 SUBJECT: GRB 250309B / AT2025dws: further SAO RAS optical observations DATE: 25/03/10 23:50:28 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin, O. I. Spiridonova (SAO RAS), A. S. Pozanenko (IKI), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg), Yu. V. Sotnikova (SAO RAS) report on behalf of a larger collaboration. We observed the field of GRB 250309B / AT2025dws (Preis and Greiner, GCN 39629; Fermi GBM team, GCN 39635; McDermott et al., GCN 39642; Wang et al., GCN 39648; Page and Evans, GCN 39649; Kozyrev et al., GCN 39652; Frederiks et al., GCN 39655; Scotton, GCN 39657) with Zeiss-1000 1-m telescope of SAO RAS, equipped with the CCD-photometer. We obtained 19 x 300 sec. images in Rc band on March 10, 21:37:13 -- 23:23:40 UT (t_mid - T0 = 1.6194 days). The optical candidate ZTF25aaitvjt / AT2025dws (Stein et al., GCN 39639; Pérez-Fournon et al., GCN 39643; Stein and Ahumada, GCN 39644; Moskvitin et al., GCN 39645; Perley et al., GCN 39646; Malesani et al., GCN 39647; Ducoin et al., GCN 39650; Shin et al, GCN 39654) is clearly detected in the stacked image with the brightness of R = 20.65 +/- 0.13. We do not performed host galaxy subtraction. The photometry is based on nearby stars from the USNO-B1.0 catalog (R2 magnitudes) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/39658. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37673] IceCube-250309A: Upper limits from Fermi-GBM Observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39657 SUBJECT: IceCube-250309A: Upper limits from Fermi-GBM Observations DATE: 25/03/10 23:19:19 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi-GBM Team: For the IceCube high-energy neutrino candidate event IceCube-250309A (GCN 39631), at the event time Fermi-GBM was observing the reported neutrino location at: RA: 211.07 (+0.31 -0.30 deg 90% PSF containment) J2000 Dec: -10.73 (+0.26 -0.30 deg 90% PSF containment) J2000 Fermi-GBM detected GRB 250309B (GCNs 39635, 39642) around 146s after the time of the neutrino candidate. However, the ZTF and GROWTH collaborations reported the detection of a potential optical counterpart ZTF25aaitvjt | AT2025dws (R. Stein et al, GCN 39639), suggesting that GRB 250309B and IceCube-250309A are unrelated. The IPN triangulation (Kozyrev A. S. et al, GCN 39652) also suggests that GRB 250309B and IceCube-250309A are unrelated. An automated, blind search for short gamma-ray bursts below the onboard triggering threshold in Fermi-GBM also identified no counterpart candidates. The GBM targeted search, the most sensitive, coherent search for GRB-like signals, was run from +/-30 s around the neutrino candidate time. From this search, no significant signal was found related to IceCube-250309A. Using the representative soft, normal, and hard GRB-like templates described in arXiv:2308.13666, we set the following 3 sigma flux upper limits over 10-1000 keV (in units of 10^-7 erg/s/cm^2): Timescale Soft Normal Hard ------------------------------------------- 0.128 s: 1.0 1.8 3.7 1.024 s: 0.35 0.56 1.3 8.192 s: 0.11 0.11 0.24 These results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39657. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37672] EP250308a: 1.6m Mephisto optical upper limits
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39656 SUBJECT: EP250308a: 1.6m Mephisto optical upper limits DATE: 25/03/10 17:46:43 GMT FROM: Brajesh Kumar at SWIFAR, YNU <brajesh(a)ynu.edu.cn> Shiyan Zhong, Jinghua Zhang, Guowang Du, Xin Chang, Bin Yan, Xingzhu Zou, Brajesh Kumar, Yuan Fang, Helong Guo, Edoardo P. Lagioia, Yuanpei Yang, Xiangkun Liu, Xiaowei Liu (all SWIFAR, YNU) report on behalf of the Mephisto Team: The field of EP250308a (Yin et al., GCN 39625) was observed with the 1.6m Multi-channel Photometric Survey Telescope (Mephisto) of Yunnan University located at Lijiang Observatory. Two exposures of 180s in the MEPHISTO u band, and six exposures of 50s in the MEPHISTO g band were simultaneously (ug) obtained starting from 2025-03-09T20:07:03 (~27h after the trigger). In our stacked u and g band images, we did not detect any source at the position reported by Yin et. al., GCN 39625. The preliminary 3-sigma upper limits are below, which is consistent with previously reported GCN (Zhu et al., GCN 39624; Busmann et al., GCN 39626; Lipunov et al. GNC 39628). Start_Time(UT) | Band | Exp(s) | LimMag(AB) --------------------|------|--------|------------ 2025-03-09T20:07:03 | u | 180*2 | >22.20 2025-03-09T20:07:03 | g | 50*6 | >22.38 ------------------------------------------------------------------------------------------------- Mephisto (Multi-channel Photometric Survey Telescope) is a 1.6-m wide-field multi-channel telescope, the first of its type in the world, capable of imaging the same field of view in three optical bands simultaneously. It provides real-time, high-quality colors of stellar objects. The on-site telescope assemblage and commissioning were carried out in September 2022. The first light in all three channels was achieved on 2023 December 21. ------------------------------------------------------------------------------------------------- View this GCN Circular online at https://gcn.nasa.gov/circulars/39656. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37671] Konus-Wind detection of GRB 250309B
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39655 SUBJECT: Konus-Wind detection of GRB 250309B DATE: 25/03/10 17:17:33 GMT FROM: Dmitry Frederiks at Ioffe Institute <fred(a)mail.ioffe.ru> D. Frederiks, A.Lysenko, A. Ridnaia, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 250309B ( Fermi-GBM BALROG localization: Preis and Greiner, GCN 39629; Fermi-GBM detection: The Fermi GBM team, GCN 39635; McDermott et al., GCN 39642; GECAM-B detection: Wang et al., GCN 39648; IPN triangulation: Kozyrev et al., GCN 39652) triggered Konus-Wind (KW) at T0=27513.791 s UT (07:38:33.791). The burst light curve shows a multi-peaked structure which starts at ~T0-0.5 s and has a total duration of ~8 s. The emission is seen up to ~1 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250309_T27513/ As observed by Konus-Wind, the burst had a fluence of (5.79 ± 0.48)x10^-6 erg/cm^2 and a 64-ms peak energy flux, measured from T0 + 1.024 s, of (4.35 ± 0.43)x10^-6 erg/cm^2/s (both in the 20 keV - 10 MeV energy range). The time-integrated spectrum (measured from T0 to T0+8.448 s) is best fit in the 20 keV - 15 MeV range by a power law with exponential cutoff (CPL) model: dN/dE ~ (E^alpha)*exp(-E*(2+alpha)/Ep) with alpha = -1.03(-0.20,+0.22) and Ep = 106(-7,+8) keV (chi2 = 80/79 dof). Fitting this spectrum by a Band function yields the same values of alpha and Ep, and an upper limit on the high energy photon index beta of -3.1 (chi2 = 79/78 dof). Assuming the redshift z=1.898 ( Malesani et al., GCN 39647) of ZTF25aaitvjt/AT 2025dws, the candidate counterpart to GRB 250309B (Stein et al., GCN 39639), 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 burst isotropic energy release E_iso to (5.3 ± 0.4)x10^52 erg, the isotropic peak luminosity L_iso to (1.2 ± 0.12)x10^53 erg/s, and the rest-frame peak spectral energy Ep,z to (306 ± 21) keV. With the obtained estimates, GRB 250309B is consistent with 68% prediction band of the 'Amati' relation and 90% prediction band of the 'Yonetoku' relation 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/GRB250309_T27513/GRB250309B_rest_frame.pdf All the quoted errors are estimated at the 68% confidence level. All the presented results are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/39655. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37670] GRB 250309B / AT2025dws: KMTNet-CTIO optical observations
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39654 SUBJECT: GRB 250309B / AT2025dws: KMTNet-CTIO optical observations DATE: 25/03/10 16:46:17 GMT FROM: Min-Su Shin at Korea Astronomy and Space Science Institute <msshin(a)kasi.re.kr> Min-Su Shin (Korea Astronomy and Space Science Institute; KASI), Jae-Woo Kim (KASI), and Seo-Won Chang (Seoul National University) report on behalf of the KMTNet neutrino ToO program: We observed the area corresponding to the neutrino event IceCube-250309A with the KMTNet-CTIO for the initial coordinates of Zegarelli et. al, GCN 39631. The KMTNet-CTIO observation started at 2025-03-09 09:44 (UTC), and we acquired I-band images for four pointings covering the entire 90% uncertainty area for the alert. The source AT2025dws (Stein et al., GCN 39639, Pérez-Fournon et al. GCN 39643, Moskvitin et al. GCN 39645, Perley et al. GCN 39646) is clearly found in the images with the following photometric measurements: MJD mag err 60743.40574 17.88 0.02 60743.40723 17.87 0.02 We thank the KMTNet operators for their support. View this GCN Circular online at https://gcn.nasa.gov/circulars/39654. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 37669] IPN triangulation of GRB 250308A (short)
by GCN Circulars 10 Mar '25

10 Mar '25

TITLE: GCN CIRCULAR NUMBER: 39653 SUBJECT: IPN triangulation of GRB 250308A (short) DATE: 25/03/10 16:02:51 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 HEND/Mars Odyssey team, D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, and T. Cline on behalf of the Konus-Wind team, Y. Zhang, C. Wang, S. Xiong, J. Wei, and B. Cordier on behalf of the SVOM-GRM team, S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, and A. Tohuvavohu on behalf of the Swift-BAT team, E. Burns on behalf of the IPN, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The short-duration GRB 250308A (SVOM-GRM detection: Wang et al., GCN 39632, 39636) was detected by SVOM (GRM), Konus-Wind, Swift (BAT), CALET (GBM), and Mars-Odyssey (HEND) at about 65191 s UT (18:06:31). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 160.761 (10h 43m 03s) +23.741 (+23d 44' 26") Corners: 160.858 (10h 43m 26s) +24.405 (+24d 24' 18") 160.981 (10h 43m 55s) +24.338 (+24d 20' 15") 160.655 (10h 42m 37s) +23.074 (+23d 04' 27") 160.536 (10h 42m 09s) +23.145 (+23d 08' 43") --------------------------------------------- The error box area is 578 sq. arcmin, and its maximum dimension is 1.3 deg (the minimum one is 7.4 arcmin). The Sun distance was 159 deg. This localization may be improved. The distance between the center of SVOM (GRM) localization (GCN 39636) and the IPN box center is 9.4 deg. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250308_T65194/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/39653. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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