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

[vsnet-grb-info 38757] sb25061207: EP-FXT follow-up observation and afterglow candidate
by GCN Circulars 13 Jun '25

13 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40718 SUBJECT: sb25061207: EP-FXT follow-up observation and afterglow candidate DATE: 25/06/13 07:28:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. J. Song (NAO, CAS), Y.L. Hua (PMO, CAS), T. Zhao, J. W. Hu , W. Yuan (NAO, CAS), A. Foisseau, C. Lachaud (APC), M. Brunet (IRAP), N. Dagoneau (CEA) report on behalf of the Einstein Probe and SVOM team We performed a follow-up observation of sb25061207 (detected by SVOM/ECLAIRs, Zhang et al, GCN #40697; followed by SVOM/VT, Li et al. GCN #40707 and Swift/XRT, Evans et al. GCN #40711), with the Follow-up X-ray Telescope (FXT) on board the Einstein Probe (EP) mission. The observation began at 2025-06-12 18:37:49, about 8 hours after the detection, and the exposure time is about 6.0 ks. Only 1 uncatalogued source was detected by both FXT-A and FXT-B in the 90% localization error circle provided by SVOM/VT (with a radius of 0.5 arcsec centered at R.A., DEC = 198.09415, +0.07508 deg), as listed below (the FXT flux is taken from FXT-B module). Source name | RA | DEC | Estimated Flux | SNR | Dist from SVOM/VT | | deg | deg | (erg/s/cm^2) | | offset (in arcsec) | ----------------------------------------------------------------------------- EP_J131222.6+000433 | 198.0939 | 0.0753 | 5.4(+/-1.7) x 10^-14 | 5.6 | 1.1 (with an uncertainty of 10 arcsec) | ----------------------------------------------------------------------------- Note: * EP_J131222.6+000433 was also detected by Swift/XRT (GCN #40711) in a ~2.6 ks observation conducted at T0+8.8 ks after the trigger, with a flux of ~6.0e-13 erg/s/cm^2. The source thus exhibits a decreasing trend in the X-ray flux within two epochs. The above observation was made with the EP-FXT instrument. 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). EP is a mission of the Chinese Academy of Sciences in collaboration with ESA, MPE and CNES. View this GCN Circular online at https://gcn.nasa.gov/circulars/40718. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38756] GRB 250612B: Fermi GBM Observation
by GCN Circulars 13 Jun '25

13 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40717 SUBJECT: GRB 250612B: Fermi GBM Observation DATE: 25/06/13 06:34:50 GMT FROM: Rushikesh Sonawane at IISER, TVM <rushikesh23(a)iisertvm.ac.in> R. Sonawane (IISER, TVM) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 12:27:56.19 UT on 12 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250612B (trigger 771424081/250612519). which was also detected by EP-WXT (Hua et al. 2025, GCN 40700). The Fermi GBM on-ground location is consistent with the EP-WXT position. The angle from the Fermi LAT boresight is 68 degrees. The GBM light curve consists of single emission episode with a duration (T90) of about 10.8 s (50-300 keV). The time-averaged spectrum from T0-4.4 to T0+18.2 s is best fit by a Band function with Epeak = 47.80 +/- 1.53 keV, alpha = -0.92 +/- 0.09, and beta = -3.47 +/- 0.39. A Comp model fits the spectrum equally well, with a power-law index = –0.98 +/- 0.07 and cutoff energy parameterized as Epeak = 49.14 +/- 1.26 keV. The event fluence (10-1000 keV) in this time interval is (5.2 +/- 0.2)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+2.9 s in the 10-1000 keV band is 12.1 +/- 0.3 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/40717. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38755] EP250612a: SVOM/VT optical candidate
by GCN Circulars 13 Jun '25

13 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40716 SUBJECT: EP250612a: SVOM/VT optical candidate DATE: 25/06/13 02:45:04 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, Y. N. Ma, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), Y. L. Hua (PMO, CAS), T. Zhao, Y. J. Song, J. W. Hu , W. Yuan (NAO, CAS) report on behalf of the SVOM and EP Teams: SVOM/VT observed the field of EP250612a (Hua et al., GCN 40700) in ToO mode in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The observation started at 2025-06-12T21:08:02 UT, about 8.67 hours after the trigger time. One uncatalogued source, compared to Legacy Survey, was detected within FXT error circle (Hua et al., GCN 40700), RA = 229.65265, DEC = -26.76771, corresponding to: R. A. (J2000) = 15:18:36.6 DEC. (J2000) = -26:46:03.8 Error = 0.5 arcseconds The brightness of the candidate is derived as below : mid-time band mag(AB) exposure 9.45 hour VT_B 22.3+/-0.1 20*70 sec 9.46 hour VT_R 21.8+/-0.1 19*70 sec Our photometry was derived in AB magnitude and not corrected for Galactic extinction. 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/40716. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38754] Fermi trigger No 771424081: Global MASTER-Net observations report
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40715 SUBJECT: Fermi trigger No 771424081: Global MASTER-Net observations report DATE: 25/06/12 23:30:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB250612.52 (trigger No 771424081,15h 27m 31.20s , -29d 52m 48.0s, R=2.4) errorbox 35391 sec after notice time and 35422 sec after trigger time at 2025-06-12 22:18:18 UT, with upper limit up to 19.0 mag. The observations began at zenith distance = 24 deg. The sun altitude is -80.1 deg. The galactic latitude b = 21 deg., longitude l = 339 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2901131 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 35453 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 17m 45.90s , -26d 51m 07.4s) | C | 60 | 18.5 | 35453 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 15m 46.32s , -26d 35m 46.7s) | C | 60 | 18.8 | 35644 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 17m 42.75s , -26d 50m 04.0s) | C | 60 | 18.6 | 35644 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 15m 43.63s , -26d 34m 41.7s) | C | 60 | 18.9 | 35836 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 17m 49.62s , -26d 49m 56.6s) | C | 60 | 18.6 | 35836 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 15m 50.50s , -26d 34m 33.7s) | C | 60 | 18.8 | 36028 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 17m 48.24s , -26d 50m 30.1s) | C | 60 | 18.6 | 36028 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 15m 49.05s , -26d 35m 06.7s) | C | 60 | 18.8 | 36220 | 2025-06-12 22:31:06 | MASTER-SAAO | (15h 17m 45.74s , -26d 50m 25.6s) | C | 60 | 18.5 | 36220 | 2025-06-12 22:31:06 | MASTER-SAAO | (15h 15m 46.54s , -26d 35m 01.8s) | C | 60 | 18.8 | 36412 | 2025-06-12 22:34:18 | MASTER-SAAO | (15h 17m 43.26s , -26d 49m 35.9s) | C | 60 | 18.6 | 36412 | 2025-06-12 22:34:18 | MASTER-SAAO | (15h 15m 44.01s , -26d 34m 11.9s) | C | 60 | 18.9 | 36819 | 2025-06-12 22:41:05 | MASTER-SAAO | (15h 17m 27.58s , -29d 16m 42.2s) | C | 60 | 18.8 | 36819 | 2025-06-12 22:41:05 | MASTER-SAAO | (15h 15m 25.41s , -29d 01m 18.1s) | C | 60 | 19.0 | 36913 | 2025-06-12 22:42:39 | MASTER-SAAO | (15h 26m 33.96s , -29d 15m 28.8s) | C | 60 | 18.7 | 36913 | 2025-06-12 22:42:39 | MASTER-SAAO | (15h 24m 31.63s , -29d 00m 04.3s) | C | 60 | 18.9 | 37006 | 2025-06-12 22:44:12 | MASTER-SAAO | (15h 17m 32.04s , -31d 08m 59.1s) | C | 60 | 18.6 | 37006 | 2025-06-12 22:44:12 | MASTER-SAAO | (15h 15m 27.34s , -30d 53m 34.4s) | C | 60 | 18.8 | 37101 | 2025-06-12 22:45:46 | MASTER-SAAO | (15h 24m 40.84s , -30d 54m 55.8s) | C | 60 | 18.9 | 37101 | 2025-06-12 22:45:46 | MASTER-SAAO | (15h 26m 45.73s , -31d 10m 20.7s) | C | 60 | 18.6 | 37400 | 2025-06-12 22:50:46 | MASTER-SAAO | (15h 32m 46.05s , -29d 00m 20.4s) | C | 60 | 18.9 | 37400 | 2025-06-12 22:50:46 | MASTER-SAAO | (15h 34m 48.67s , -29d 15m 47.0s) | C | 60 | 18.7 | 37496 | 2025-06-12 22:52:21 | MASTER-SAAO | (15h 41m 54.86s , -29d 02m 31.9s) | C | 60 | 18.9 | 37496 | 2025-06-12 22:52:21 | MASTER-SAAO | (15h 43m 57.74s , -29d 17m 58.3s) | C | 60 | 18.6 | 37589 | 2025-06-12 22:53:55 | MASTER-SAAO | (15h 15m 24.67s , -28d 59m 08.1s) | C | 60 | 18.8 | 37589 | 2025-06-12 22:53:55 | MASTER-SAAO | (15h 17m 27.19s , -29d 14m 33.9s) | C | 60 | 18.8 | 37683 | 2025-06-12 22:55:28 | MASTER-SAAO | (15h 24m 28.23s , -29d 00m 36.4s) | C | 60 | 18.8 | 37683 | 2025-06-12 22:55:28 | MASTER-SAAO | (15h 26m 30.96s , -29d 16m 02.0s) | C | 60 | 18.6 | 37989 | 2025-06-12 23:00:35 | MASTER-SAAO | (15h 15m 27.98s , -30d 53m 53.2s) | C | 60 | 18.8 | 37989 | 2025-06-12 23:00:35 | MASTER-SAAO | (15h 17m 33.30s , -31d 09m 17.4s) | C | 60 | 18.6 | 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/40715. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38753] EP250612a: Global MASTER-Net observations report
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40714 SUBJECT: EP250612a: Global MASTER-Net observations report DATE: 25/06/12 22:36:21 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, 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.Sosnovskij (CrAO), 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-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the EP250612a ( EP Team et al., GCN 40700) errorbox 33238 sec after notice time and 35413 sec after trigger time at 2025-06-12 22:18:18 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 24 deg. The sun altitude is -80.1 deg. The galactic latitude b = 25 deg., longitude l = 340 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2901165 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 17m 45.90s , -26d 51m 07.4s) | C | 60 | 18.5 | 35444 | 2025-06-12 22:18:18 | MASTER-SAAO | (15h 15m 46.32s , -26d 35m 46.7s) | C | 60 | 18.8 | 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 17m 42.75s , -26d 50m 04.0s) | C | 60 | 18.6 | 35635 | 2025-06-12 22:21:29 | MASTER-SAAO | (15h 15m 43.63s , -26d 34m 41.7s) | C | 60 | 18.9 | 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 17m 49.62s , -26d 49m 56.6s) | C | 60 | 18.6 | 35828 | 2025-06-12 22:24:42 | MASTER-SAAO | (15h 15m 50.50s , -26d 34m 33.7s) | C | 60 | 18.8 | 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 17m 48.24s , -26d 50m 30.1s) | C | 60 | 18.6 | 36019 | 2025-06-12 22:27:53 | MASTER-SAAO | (15h 15m 49.05s , -26d 35m 06.7s) | C | 60 | 18.8 | 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/40714. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38752] GRB 250612C: Fermi GBM Observation
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40713 SUBJECT: GRB 250612C: Fermi GBM Observation DATE: 25/06/12 21:54:11 GMT FROM: eliza.neights(a)gmail.com E. Neights (GWU, NASA GSFC) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 14:53:16.58 UT on 12 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250612C (trigger 771432801/250612620). which was also detected by SVOM/GRM (Wang et al. 2025, GCN 40708). The Fermi-GBM position was reported in GCN 40708 (Fermi GBM Team 2025). The angle from the Fermi LAT boresight is 96 degrees. The GBM light curve consists of multiple emission episodes with a duration (T90) of about 1.62 s (50-300 keV). The time-averaged spectrum from T0-0.128 to T0+2.688 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.97 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 2110 +/- 70 keV. A Band function fits the spectrum equally well with Epeak = 2110 +/- 70 keV, alpha = -0.97 +/- 0.01, and beta = -4 +/- 1. The event fluence (10-1000 keV) in this time interval is (2.80 +/- 0.02)E-05 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.77 s in the 10-1000 keV band is 154 +/- 3 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/40713. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38751] sb25061218: SVOM detection of a X-ray transient
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40712 SUBJECT: sb25061218: SVOM detection of a X-ray transient DATE: 25/06/12 21:40:47 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. Rodriguez, T. Sadibekova, B. Cordier, N. Dagoneau (CEA), U. Jacob (LUPM) on behalf of the SVOM mission team. At 2025-06-12T20:36:00 UTC (T0), SVOM/ECLAIRs triggered and located the X-ray transient sb25061218 (SVOM burst-id sb25061218). 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 Image Trigger (IMT), which produced a sequence of 1 alert. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 7.01 in the [8-120] keV energy band over a time window of 81.92 seconds starting at 2025-06-12T20:34:38. The localization of the best alert is R.A., Dec. 198.5028, 54.6582 degrees: R.A. (J2000) = 13h14m00.67s Dec. (J2000) = 54d39m29.47s with a 90% confidence level (C.L.) radius of 11.16 arcmin (including systematic error of 2 arcmin added in quadrature). This burst was also detected by SVOM/GRM with a significance of 5.80. Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. 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 Jerome Rodriguez: jerome.rodriguez(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/40712. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38750] sb25061207: Swift-XRT observations
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40711 SUBJECT: sb25061207: Swift-XRT observations DATE: 25/06/12 21:12:28 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans (U. Leicester), J.A. Kennea (PSU), E. Ambrosi (INAF-IASFPA) , A.P. Beardmore (U. Leicester), M.G. Bernardini (INAF-OAB), R. Brivio (INAF-OAB), D.N. Burrows (PSU), S. Campana (INAF-OAB), M. Capalbi (INAF-OAR), A. D'Ai (INAF-IASFPA), P. D'Avanzo (INAF-OAB), V. D'Elia (SSDC & INAF-OAR), S. Dichiara (PSU), M. Ferro (INAF-OAB), A. Melandri (INAF-OAR), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), M. Perri (SSDC & INAF-OAR), C. Salvaggio (INAF-OAB), T. Sbarrato (INAF-OAB), B. Sbarufatti (INAF-OAB), M.A. Williams (PSU) report on behalf of the Swift-XRT team: Swift-XRT has performed follow-up observations of the SVOM/ECLAIRs-detected source sb25061207, collecting 2.6 ks of Photon Counting (PC) mode data between T0+8.8 ks and T0+20 ks after the trigger. We have detected 4 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 4 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 1 (SWIFT J131222.8+000431): ================================== RA (J2000.0): 198.0954 = 13h 12m 22.90s Dec (J2000.0): +0.0753 = +00d 04' 31.1" Error: 6.4 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 7.2 arcmin from the SVOM/ECLAIRs position; 4.6 arcsec from SVOM/VT counterpart (GCN 40707). Mean rate: 0.0133 [+0.0031, -0.0028] ct s^-1 Mean flux: (6.0 [+1.4, -1.3])e-13 erg cm^-2 s^-1 Peak rate: 0.0147 +/- 0.0037 ct s^-1 Peak flux: (6.6 +/- 1.7)e-13 erg cm^-2 s^-1 ECF: 4.50e-11 erg cm^-2 ct^-1, assuming NH=2.24e+20 cm^-2, gamma=1.42; determined from a spectral fit. XMM UL: 2.7e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 12.4-sigma above this 3-sigma upper limit. The source may be fading, at the 0.6-sigma level. Source 2 (SWIFT J131136.2+000123): ================================== RA (J2000.0): 197.9010 = 13h 11m 36.24s Dec (J2000.0): +0.0233 = +00d 01' 23.9" Error: 5.9 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 5.2 arcmin from the SVOM/ECLAIRs position. Mean rate: (7.2 +/- 2.1)e-3 ct s^-1 Mean flux: (7.4 +/- 2.1)e-13 erg cm^-2 s^-1 Peak rate: (7.2 +/- 2.1)e-3 ct s^-1 Peak flux: (7.4 +/- 2.1)e-13 erg cm^-2 s^-1 ECF: 1.03e-10 erg cm^-2 ct^-1, assuming NH=2.41e+21 cm^-2, gamma=0.47; determined from a spectral fit. XMM UL: 4.4e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 17.2-sigma above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `MGC 42939' is 5.7" away. Source 3 (SWIFT J131139.2-000814): ================================== RA (J2000.0): 197.9134 = 13h 11m 39.22s Dec (J2000.0): -0.1375 = -00d 08' 15.0" Error: 7.3 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 10.5 arcmin from the SVOM/ECLAIRs position. Mean rate: (6.3 [+2.4, -1.9])e-3 ct s^-1 Mean flux: (1.36 [+0.52, -0.42])e-18 erg cm^-2 s^-1 Peak rate: (6.3 [+2.4, -1.9])e-3 ct s^-1 Peak flux: (1.36 [+0.52, -0.42])e-18 erg cm^-2 s^-1 ECF: 2.14e-16 erg cm^-2 ct^-1, assuming NH=4.37e+21 cm^-2, gamma=96.83; determined from a spectral fit. XMM UL: 2.7e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 5817530.8-sigma above this 3-sigma upper limit. There is no evidence for fading. Source 4 (SWIFT J131140.3-000120): ================================== RA (J2000.0): 197.9181 = 13h 11m 40.34s Dec (J2000.0): -0.0225 = -00d 01' 21.0" Error: 6.1 (arcsec, radius, 90% confidence). Detect flag: REASONABLE Distance: 4.9 arcmin from the SVOM/ECLAIRs position. Mean rate: (2.6 [+1.5, -1.2])e-3 ct s^-1 Mean flux: (1.61 [+0.96, -0.73])e-13 erg cm^-2 s^-1 Peak rate: (2.6 [+1.5, -1.2])e-3 ct s^-1 Peak flux: (1.61 [+0.96, -0.73])e-13 erg cm^-2 s^-1 ECF: 6.23e-11 erg cm^-2 ct^-1, assuming NH=3.65e+22 cm^-2, gamma=2.45; determined from a spectral fit. XMM UL: 4.8e-12 erg cm^-2 s^-1, (0.3-10 keV) so the source is 55.2-sigma above this 3-sigma upper limit. There is no evidence for fading. All fluxes are 0.3-10 keV, observed. For all flux conversions and comparisons with catalogues and upper limits from other missions, we assumed a power-law spectrum with NH=3x10^20 cm^-2 and photon index (Gamma)=1.7 unless otherwise stated. The results of the XRT-team automatic analysis of the XRT observations, including a position-specific upper limit calculator, are available at https://www.swift.ac.uk/SVOM. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40711. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38749] EP250612a/GRB 250612B: JinShan optical upper limit
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40710 SUBJECT: EP250612a/GRB 250612B: JinShan optical upper limit DATE: 25/06/12 17:24:35 GMT FROM: liuxing(a)nao.cas.cn X. Liu, Z.P. Zhu, J. An, S.Q. Jiang, D. Xu (NAOC), S.Y. Fu(HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of EP250612a detected by EP/WXT (Hua et al., GCN 40700), which is very likely GRB 250612B by Fermi/GBM (Preis & Greiner, GCN 40701; Fermi GBM tea, GCN 40702), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 15:45:13 UT on 2025-06-12, i.e., 3.29 hr after the EP trigger, and 18 x 200 s frames were obtained in the Sloan i-band. No new optical source is detected within the EP/FXT error circle (Hua et al., GCN 40700), down to a 3-sigma upper limit of i ~ 20.2 mag (AB), calibrated with nearby PanSTARRS stars and not corrected for Galactic extinction. We acknowledge the excellent support from T.Q. Chen for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40710. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38748] EP 250612a: AST3-3 Yaoan Optical Observation
by GCN Circulars 12 Jun '25

12 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40709 SUBJECT: EP 250612a: AST3-3 Yaoan Optical Observation DATE: 25/06/12 16:49:28 GMT FROM: ylhua(a)pmo.ac.cn Yan-Long Hua, Tian-Rui Sun, Lei Hu, Jin-Jun Geng, Xue-Feng Wu (PMO, CAS), report on behalf the AST3 Team: Following the detection of EP 250612a detected by Einstein Probe (Hua et al., GCN 40700), and its potential gamma-ray counterpart by Fermi (Fermi GBM team, GCN 40702), we use Antarctic Survey Telescope 3-3 at Yaoan Astronomy Observation (China, Yunnan) to follow up for the afterglow. We observed the target position with 30 x 180s exposure in g-band starting from 2025-06-12T13:12:59.95 about 0.75 hours after the burst. No new optical source was detected within the error box (Hua et al., GCN 40700) down to 20.27 mag in the coadd image (total 30x180s, g-band). View this GCN Circular online at https://gcn.nasa.gov/circulars/40709. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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