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

[vsnet-grb-info 38711] GRB 250610B : SVOM/GWAC-F60A and F50 observations
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40672 SUBJECT: GRB 250610B : SVOM/GWAC-F60A and F50 observations DATE: 25/06/10 18:53:15 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> J. Wang, W. L. Dong, L. P. Xin(NAOC), L. J. Chen(GXU), Y. G. Yang(HNU), X. H. Han, C. WU, Y. L. Qiu, H. L. Li, X .M. Lu, R. S. Zhang, Y. Xu, L. Huang, H. B. Cai, Y. J. Xiao, P. P. Zhang, L. Lan, W. J. Xie, Z. H. Yao, J. Y. Wei(NAOC), X. G. Wang, E. W. Liang(GXU) and W. Zheng (UCB) report on behalf of the SVOM follow-up team: We observed the field of SVOM GRB 250610B (Saccardi et al., GCN 40671) with the GWAC-F60A and GWAC-F50 at Xinglong Observatory, China. F60A started observing at 2025-06-10T17:14:17.39 UTC with a set of 34 images in R-band. F50 started observing at 2025-06-10T17:14:17.39 UTC and with a set of 9 images in R-band. After coadding the images, we do not find any uncatalog candidate within the SVOM/ECLAIRs error box. We estimate the upper limit of 16.0 mag for GWAC-F60A at mid time of 54.5 minutes after brust, and upper limit of 17.5 mag for GWAC-F50 at mid time of 54.0 minutes after brust. Two 60cm GWAC-F60(A/B) are operated by Guangxi University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 19*19 arcmin. The 50cm telescope (F50A) is operated by Huaibei Normal University and NAOC, CAS, at Xinglong Observatory, China. The field of view is 27*27 arcmin. View this GCN Circular online at https://gcn.nasa.gov/circulars/40672. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38710] GRB 250610B: SVOM detection of a long burst
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40671 SUBJECT: GRB 250610B: SVOM detection of a long burst DATE: 25/06/10 17:27:30 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> A. Saccardi, J. Rodriguez, N. Dagoneau (CEA), C. Van Hove (IJCLab) report on behalf of the SVOM mission team. At 2025-06-10T16:32:58 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250610B (SVOM burst-id sb25061018). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 40 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 30.55 in the [8-50] keV energy band over a time window of 81.92 seconds starting at 2025-06-10T16:33:19. The localization of the best alert is R.A., Dec. 200.1831, 31.1028 degrees: R.A. (J2000) = 13h20m43.94s Dec. (J2000) = 31d06m10.04s with a 90% confidence level (C.L.) radius of 3.22 arcmin (including systematic error of 2 arcmin added in quadrature). The ECLAIRs light curve may show a double narrow peak structure with a T90 duration of about 134.368 (-13.465 +23.518) s. The ECLAIRs peak count rate was ~496.6503 ± 191.3858 counts/sec in the band [20-50] keV, ~5.6 seconds after the trigger. This burst was also detected by SVOM/GRM with a significance of 14.30. The GRM light curve showed a single broad peak structure with a T90 duration of about 69.237 (-6.343 +6.558) s. The GRM peak count rate was ~470.4469 ± 82.6942 counts/sec in the band [4-5000] keV, ~34.4 seconds after the trigger. A SVOM ToO has been executed for follow-up and started to observe at 2025-06-10T16:59 UTC. 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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Andrea Saccardi: andrea.saccardi(a)cea.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/40671. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38709] Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40670 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB DATE: 25/06/10 14:25:40 GMT FROM: eliza.neights(a)gmail.com E. Neights (GWU, NASA GSFC) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 771256110/250610575 at 13:48:25.58 UT on 10 June 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to local particles." View this GCN Circular online at https://gcn.nasa.gov/circulars/40670. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38708] EP250610a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40669 SUBJECT: EP250610a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/06/10 14:16:44 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T.Y. Lian, H. Q. Cheng (NAO, CAS), Y. J. Zhang (THU) and C. C. Jin (NAO, CAS) report on behalf of the Einstein Probe team: The fast X-ray transient EP250610a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 40660), and followed up by several optical and X-ray telescopes (Schneider et al., GCN 40661, Brivio et al., GCN 40665, Evans et al., GCN 40662). Refined analysis of the WXT data shows that the event started at T0=2025-06-10T04:23:24 (UTC) and lasted for about 140s before the interruption by the autonomous follow-up observation. The peak flux (0.5-4 keV) is estimated to be 2.2 x 10^-9 erg/s/cm^2. The averaged 0.5-4 keV spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 0.7 (-/+0.8). The derived average unabsorbed 0.5-4 keV flux is 5.2 (-2.3, +4.2) x 10^-10 erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously at 2025-06-10T04:26:32, about 3 minutes after T0, with an exposure time of 3946 seconds. Within the WXT error circle, on-ground analysis of the FXT data found an uncatalogued source at R.A. = 248.3567, DEC = 38.5362 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic), which is spatially consistent with the candidate X-ray counterpart detected by Swift/XRT (Source 1 in Evans et al., GCN 40662). The averaged 0.5-10 keV FXT spectrum can be fitted with an absorbed power-law with a Galactic hydrogen column density of 9.5 x 10^19 cm^-2 and a photon index of 2.34 (-0.12, +0.12). The derived unabsorbed 0.5-10 keV flux is 1.87 (-0.17, +0.19) x 10^-12 erg/s/cm^2. The uncertainties are at the 90% confidence level for all the above parameters. 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). The contact TAs of this source are Tianying Lian and Huaqing Cheng, please contact them via the email tylian(a)nao.cas.cn and hqcheng(a)nao.cas.cn if needed. View this GCN Circular online at https://gcn.nasa.gov/circulars/40669. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38707] GRB 250610A: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40668 SUBJECT: GRB 250610A: Fermi GBM Final Real-time Localization DATE: 25/06/10 13:58:44 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 13:48:25 UT on 10 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250610A (trigger 771256110.581806 / 250610575). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 359.9, Dec = 65.1 (J2000 degrees, equivalent to J2000 23h 59m, 65d 05'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 0.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250610575/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250610575/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250610575/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40668. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38706] GRB 250605A: Swift-BAT refined analysis
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40667 SUBJECT: GRB 250605A: Swift-BAT refined analysis DATE: 25/06/10 13:23:05 GMT FROM: Mike Moss at NASA GSFC <mikejmoss3(a)gmail.com> R. Gupta (GSFC), S. D. Barthelmy (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250605A (trigger #1321323) (Gupta, et al., GCN Circ. 40633). The BAT ground-calculated position is RA, Dec = 166.963, -19.786 deg which is RA(J2000) = 11h 07m 51.1s Dec(J2000) = -19d 47' 10.5" with an uncertainty of 1.2 arcmin, (radius, sys+stat, 90% containment). The partial coding was 35%. The BAT light curve shows a complex light curve with multiple emission episodes: a period of very dim extended emission between ~T0-100 sec to T0-10 leading up to one strong pulse between T0-10 sec to T0+10 sec and followed by a dim broad pulse between T0+40 sec to ~T0+125 sec. T90 (15-350 keV) is 176.05 +- 5.15 sec (estimated error including systematics). The time-averaged spectrum from T-100.30 to T+126.69 sec is best fit by a power law with an exponential cutoff. This fit gives a photon index 1.50 +- 0.22, and Epeak of 76.7 +- 27.6 keV (chi squared 71.54 for 56 d.o.f.). For this model the total fluence in the 15-150 keV band is 1.2 +- 0.0 x 10^-05 erg/cm2 and the 1-sec peak flux measured from T-0.00 sec in the 15-150 keV band is 6.1 +- 0.4 ph/cm2/sec. A fit to a simple power law gives a photon index of 1.83 +- 0.05 (chi squared 79.05 for 57 d.o.f.). All the quoted errors are at the 90% confidence level. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1321323 View this GCN Circular online at https://gcn.nasa.gov/circulars/40667. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38705] EP250610a: SVOM/VT optical upper limit
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40666 SUBJECT: EP250610a: SVOM/VT optical upper limit DATE: 25/06/10 12:55:24 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> Z. H. Yao, L. P. Xin, Y. L. Qiu, H. L. Li, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA),Y. J. Zhang (THU), T. Y. Lian, H. Q. Cheng, C. C. Jin (NAO, CAS), Lin Lan (NAOC), Run-Chao Chen (NJU), Chen-Wei Wang, Wen-Jun Tan (IHEP) report on behalf of the SVOM and EP mission team: SVOM performed a Target of Opportunity observation of EP250610a detected by EP/WXT (Zhang et al., GCN 40660). SVOM/VT began observing the field at 2025-06-10 06:16:38 UTC, 1.85 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. No credible candidate was detected in our single or stacked images within the errorbox of EP/FXT (Zhang et al., GCN 40660) or Swift/XRT (Evans et al., GCN 40662 ), the three sigma limits are: [date-obs|mid-time] | exposure time (s) | band | upper limit (AB) ----------- --------|-------------------|------|----------------- 2025-06-10T07:29:10 | 76×70 | VT_B | 23.93 2025-06-10T07:29:10 | 76×70 | VT_R | 23.45 The upper limit is consistent with reports (Schneider et al., GCN 40661, Brivio et al., GCN 40665). Deeper or redder follow-ups are encouraged to investigate the nature of the transient。 The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Centre 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/40666. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38704] EP250610a: REM optical/NIR observations
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40665 SUBJECT: EP250610a: REM optical/NIR observations DATE: 25/06/10 12:20:35 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio, M. Ferro, P. D'Avanzo, S. Covino, D. Fugazza (INAF-OAB) report on behalf of the REM team: We observed the field of EP 250610a detected by EP/WXT (Zhang et al., GCN 40660) with the REM 60 cm robotic telescope located at the ESO observatory of La Silla (Chile). The observations were carried in the g, r, i, z, and H bands, started on 2025 June 10 at 05:02:09 UT (i.e. 36 min after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any possible counterpart at the position of the candidate detected by Swift/XRT (source 1, Evans et al., GCN 40662) down to the following 3sigma limits: r > 18.7 (AB; calibrated against the Pan-STARRS catalogue), at a mid-time of 66 min after the trigger; H > 16.6 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 39 min after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40665. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38703] GRB 250609A: Fermi GBM Observation
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40664 SUBJECT: GRB 250609A: Fermi GBM Observation DATE: 25/06/10 09:59:45 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> C. Malacaria (ISSI) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 08:47:18.61 UT on 09 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250609A (trigger 771151643/250609366). which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 40658). The Fermi GBM on-ground location was reported by the Fermi-GBM team in GCN 40652. The angle from the Fermi LAT boresight is 81 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 1 s (50-300 keV). The time-averaged spectrum from T0-5.5 to T0+1.7 s is best fit by a simple power law function with index -1.3 +/- 0.1. The event fluence (10-1000 keV) in this time interval is (4.5 +/- 0.9)E-07 erg/cm^2. The 64-ms peak photon flux measured starting from T0-0.13 s in the 10-1000 keV band is 4 +/- 1 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/40664. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38702] GRBAlpha reentry on June 9, 2025
by GCN Circulars 10 Jun '25

10 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40663 SUBJECT: GRBAlpha reentry on June 9, 2025 DATE: 25/06/10 09:37:37 GMT FROM: Andras Pal at Konkoly Observatory <apal(a)szofi.net> A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), L. Meszaros (Konkoly Observatory), J. Ripa (Masaryk U.), M. Ohno (Hiroshima U.), M. Dafcikova (Masaryk U.), H. Takahashi (Hiroshima U.), B. Csak (Konkoly Observatory), N. Husarikova, F. Munz , M. Topinka, M. Duriskova, M. Kolar, L. Szakszonova, 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. After more than 4 years of scientific operations, on June 9, 2025, GRBAlpha, an 1U CubeSat reentered the Earth's atmosphere. GRBAlpha was the first GRB detecting CubeSat of this size and the smallest astrophysical space observatory (Pál et al. 2023, A&A, 677, A40). With 127 GRBs and a similar number of solar flare detections it successfully demonstrated that monitoring of gamma-ray transients can be effectively performed by CubeSats. We thank for the support of the radio amateur community, especially the maintainers and the station owners of the SatNOGS network. We look forward to more successful nanosatellite missions! View this GCN Circular online at https://gcn.nasa.gov/circulars/40663. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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