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[vsnet-grb-info 38921] GRB 250628B: Swift-XRT observations
by GCN Circulars 30 Jun '25

30 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40877 SUBJECT: GRB 250628B: Swift-XRT observations DATE: 25/06/30 15:04:43 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 GRB 250628B/sb25062804, collecting 1.4 ks of Photon Counting (PC) mode data between T0+2.9 ks and T0+8.9 ks after the trigger. We have detected 2 sources, outside the SVOM/ECLAIRs error circle. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 1 uncatalogued X-ray source * 1 known X-ray source Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J221311.1-454427): ================================== RA (J2000.0): 333.2963 = 22h 13m 11.11s Dec (J2000.0): -45.7408 = -45d 44' 26.9" Error: 6.8 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 12.0 arcmin from the SVOM/ECLAIRs position. Mean rate: (7.7 [+3.9, -3.0])e-3 ct s^-1 Mean flux: (2.9 [+1.5, -1.1])e-13 erg cm^-2 s^-1 Peak rate: (7.7 [+3.9, -3.0])e-3 ct s^-1 Peak flux: (2.9 [+1.5, -1.1])e-13 erg cm^-2 s^-1 ECF: 3.78e-11 erg cm^-2 ct^-1, assuming NH=2.76e+22 cm^-2, gamma=2.97; determined from a spectral fit. RASS UL: 1.0e-01 ct s^-1 (converted to XRT; 0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. Known X-ray sources ------------------- Source 1 (SWIFT J221222.2-452220): ================================== RA (J2000.0): 333.0927 = 22h 12m 22.25s Dec (J2000.0): -45.3724 = -45d 22' 20.6" Error: 6.3 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 11.9 arcmin from the SVOM/ECLAIRs position. Mean rate: 0.0141 [+0.0050, -0.0041] ct s^-1 Mean flux: (3.16 [+1.12, -0.91])e-13 erg cm^-2 s^-1 Peak rate: 0.0141 [+0.0050, -0.0041] ct s^-1 Peak flux: (3.16 [+1.12, -0.91])e-13 erg cm^-2 s^-1 ECF: 2.24e-11 erg cm^-2 ct^-1, assuming NH=1.46e+20 cm^-2, gamma=3.23; determined from a spectral fit. This matches a catalogued X-ray source LSXPS J221222.5-452221 in the LSXPS catalogue. Details: Separation: 3.6" from the XRT source Cat Rate: 2.4e-02 +/- 2.1e-03 ct s^-1 Cat Flux: 5.3e-13 +/- 4.7e-14 erg cm^-2 s^-1 (0.3-10 keV) so the source is not above the catalogued flux. There is no evidence for fading. A SIMBAD object `TYC 8438-268-1' is 3.7" away. There is 1 2MASS object within the source's 3-sigma error radius. 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. We did not detect any sources consistent with the five EP-FXT candidates reported by Zhang et al. (GCN #40874). 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/40877. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38920] Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB
by GCN Circulars 30 Jun '25

30 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40876 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772981768/250630548 is not a GRB DATE: 25/06/30 14:44:50 GMT FROM: Peter Veres at University of Alabama in Huntsville <veresp(a)gmail.com> Peter Veres (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 772981768/250630548 at 13:09:23.19 UT on 30 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/40876. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38919] GRB 250628B: SVOM/VT optical upper limit
by GCN Circulars 30 Jun '25

30 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40875 SUBJECT: GRB 250628B: SVOM/VT optical upper limit DATE: 25/06/30 09:34:49 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. L. Qiu, L. P. Xin, C. Wu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, Z. H. Yao, Y. N. Ma, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA), D. Dornic (CPPM)，J-G. Ducoin（CPPM）report on behalf of the SVOM/VT team. SVOM/VT performed ToO follow-up observations on the GRB 250628B (SVOM burst-id sb25062804, Dornic et al., GCN 40862) in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The observation started on 2025-06-28T20:33:10 UT, ie. 4.06 hours after the SVOM T0 time. No uncatalogued sources are detected in single or stacked images at the position of the Swift/XRT (https://www.swift.ac.uk/SVOM/SVOM_FIELD00021/) and EP (Zhang et al., GCN 40874), compared to the Legacy survey. The 3 sigma upper limit magnitudes are derived as below: Mid_time | Band | Exposure Time | Upper limit (AB) 5.8 hour VT_B 50*70 sec 23.6 mag 5.8 hour VT_R 49*70 sec 23.4 mag Also no apparent variation is found for the catalogued sources that lie within the errorbox of the Swift/XRT (https://www.swift.ac.uk/SVOM/SVOM_FIELD00021/) and EP (Zhang et al., GCN 40874). 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/40875. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38918] GRB 250628B: EP-FXT counterpart detection
by GCN Circulars 30 Jun '25

30 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40874 SUBJECT: GRB 250628B: EP-FXT counterpart detection DATE: 25/06/30 06:04:47 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> W. J. Zhang, X. Mao (NAO, CAS), Y. C. Fu (BNU), H. W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of the SVOM/ECLAIRs-detected burst GRB 250628B (SVOM/sb25062804, Dornic et al. GCN #40862) at 2025-06-28T18:51:59 (UTC), about 140 minutes after the SVOM/ECLAIRs trigger, with an exposure time of ~5000s. Five uncatalogued sources are detected within the ECLAIRs error circle. Preliminary analysis of these sources has been conducted automatically, and the details are listed below. Source 1: EPF_J221230.7-453117 RA (J2000): 333.1278 Dec (J2000): -45.5213 Flux: 6.57 x 10^-14 erg/s/cm2 (FXT-A observed, 0.5-10 kev) Flux_err: 2.48 x 10^-14 erg/s/cm2 (1 sigma) Source 2: EPF_J221214.3-453344 RA (J2000): 333.0595 Dec (J2000): -45.5621 Flux: 2.13 x 10^-13 erg/s/cm2 (FXT-A observed, 0.5-10 kev) Flux_err: 4.30 x 10^-14 erg/s/cm2 (1 sigma) Source 3: EPF_J221327.1-453729 RA (J2000): 333.3628 Dec (J2000): -45.6247 Flux: 1.89 x 10^-13 erg/s/cm2 (FXT-A observed, 0.5-10 kev) Flux_err: 4.06 x 10^-14 erg/s/cm2 (1 sigma) Source 4: EPF_J221218.2-453223 RA (J2000): 333.0758 Dec (J2000): -45.5397 Flux: 9.71 x 10^-14 erg/s/cm2 (FXT-A observed, 0.5-10 kev) Flux_err: 2.74 x 10^-14 erg/s/cm2 (1 sigma) Source 5: EPF_J221226.9-453909 RA (J2000): 333.1120 Dec (J2000): -45.6525 Flux: 4.23 x 10^-14 erg/s/cm2 (FXT-B observed, 0.5-10 kev) Flux_err: 1.54 x 10^-14 erg/s/cm2 (1 sigma) Note: Sources 1-3 were simultaneously detected by both FXT-A and FXT-B, while Source 4 and Source 5 were individually detected by FXT-A and FXT-B, respectively. The position uncertainties of the sources are about 10 arcsec in radius (90% C.L. statistical and systematic). 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40874. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38917] LIGO/Virgo/KAGRA S250629bs: Updated Sky localization
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40873 SUBJECT: LIGO/Virgo/KAGRA S250629bs: Updated Sky localization DATE: 25/06/29 16:37:41 GMT FROM: John Veitch at U of Glasgow <john.veitch(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) data around the time of the compact binary merger (CBC) candidate S250629bs (GCN Circular 40869). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250629bs For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 2998 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4847 +/- 1746 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/40873. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38916] GRB 250627A: Insight-HXMT detection
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40872 SUBJECT: GRB 250627A: Insight-HXMT detection DATE: 25/06/29 15:49:05 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong, and Chao Zheng report on behalf of the Insight-HXMT team: At 2025-06-27T16:46:23 (T0), Insight-HXMT/HE detected the short burst GRB 250627A, which is also detected by SVOM/GRM (Wang et al., GCN #40871). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.9 +0.1/-0.2 s. The 1s peak rate, measured from T0+0.175 s, is 7839 cnts/sec. The total counts from this burst is 8292 counts. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb250627A.png All measurements above are made with the CsI detectors operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://www.hxmt.org. View this GCN Circular online at https://gcn.nasa.gov/circulars/40872. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38915] GRB 250627A: SVOM/GRM detection of a short burst
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40871 SUBJECT: GRB 250627A: SVOM/GRM detection of a short burst DATE: 25/06/29 14:35:58 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Jean-Luc Atteia (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a hard short burst GRB 250627A (SVOM trigger reference: sb25062711) at 2025-06-27T16:46:23 UTC (T0). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a single pulse with a T90 of 0.9 +0.2/-0.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250627A.png In addition, ECLAIRs was collecting data at the time of this burst and also detected this burst in the energy range of above 50 keV, although this burst is outside ECLAIRs FOV. 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40871. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38914] LIGO/Virgo/KAGRA S250629ae: Updated Sky localization
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40870 SUBJECT: LIGO/Virgo/KAGRA S250629ae: Updated Sky localization DATE: 25/06/29 13:31:48 GMT FROM: Aditya Vijaykumar <aditya.vijaykumar(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250629ae (GCN Circular 40867). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250629ae For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 2834 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 7075 +/- 2116 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/40870. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38913] LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40869 SUBJECT: LIGO/Virgo/KAGRA S250629bs: Identification of a GW compact binary merger candidate DATE: 25/06/29 13:05:07 GMT FROM: rodrigo.cuzinatto(a)unifal-mg.edu.br The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250629bs during real-time processing of data from LIGO Hanford Observatory (H1) and LIGO Livingston Observatory (L1) at 2025-06-29 12:13:04.377 UTC (GPS time: 1435234402.377). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], and MBTA [4] analysis pipelines. S250629bs is an event of interest because its false alarm rate, as estimated by the online analysis, is 4.3e-08 Hz, or about one in 8 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250629bs The classification of the GW signal, in order of descending probability, is BBH (94%), Terrestrial (6%), BNS (<1%), or NSBH (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [5] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [5] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (22.0, 44.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [6], distributed via GCN and SCiMMA notices about 23 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [6], distributed via GCN and SCiMMA notices about 4 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 3008 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1811 +/- 561 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [4] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [5] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [6] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/40869. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38912] LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40868 SUBJECT: LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate DATE: 25/06/29 12:55:27 GMT FROM: rodrigo.cuzinatto(a)unifal-mg.edu.br The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250628am during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-06-28 18:23:19.785 UTC (GPS time: 1435170217.785). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S250628am is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.7e-14 Hz, or about one in 1e6 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250628am The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (5.5, 11.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 32 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 427 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1112 +/- 273 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [4] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/40868. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38911] LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate
by GCN Circulars 29 Jun '25

29 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40867 SUBJECT: LIGO/Virgo/KAGRA S250629ae: Identification of a GW compact binary merger candidate DATE: 25/06/29 06:56:02 GMT FROM: 林峻哲Lin, Chun-Che <lupin(a)phys.ncku.edu.tw> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250629ae during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-06-29 05:50:36.925 UTC (GPS time: 1435211454.925). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], and PyCBC Live [5] analysis pipelines. S250629ae is an event of interest because its false alarm rate, as estimated by the online analysis, is 3.2e-08 Hz, or about one in 11 months. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250629ae The classification of the GW signal, in order of descending probability, is BBH (98%), Terrestrial (2%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [6] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [6] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (22.0, 44.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [7], distributed via GCN and SCiMMA notices about 40 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [7], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 3184 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 4550 +/- 1295 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [4] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [7] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/40867. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38910] LIGO/Virgo/KAGRA S250628am: Updated Sky localization
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40866 SUBJECT: LIGO/Virgo/KAGRA S250628am: Updated Sky localization DATE: 25/06/28 21:09:56 GMT FROM: Aditya Vijaykumar <aditya.vijaykumar(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We have conducted further analysis of the LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) data around the time of the compact binary merger (CBC) candidate S250628am (GCN Circular 40863). Parameter estimation has been performed using Bilby [1] and a new sky map, Bilby.multiorder.fits,0, distributed via GCN and SCiMMA notices, is available for retrieval from the GraceDB event page: https://gracedb.ligo.org/superevents/S250628am For the Bilby.multiorder.fits,0 sky map, the 90% credible region is 287 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 902 +/- 223 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Ashton et al. ApJS 241, 27 (2019) doi:10.3847/1538-4365/ab06fc and Morisaki et al. PRD 108, 123040 (2023) doi:10.1103/PhysRevD.108.123040 View this GCN Circular online at https://gcn.nasa.gov/circulars/40866. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38909] GRB 250628A: REM optical/NIR upper limits
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40865 SUBJECT: GRB 250628A: REM optical/NIR upper limits DATE: 25/06/28 20:02:00 GMT FROM: Matteo Ferro at INAF-OAB <matteo.ferro(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 GRB 250628A detected by Swift/BAT (Ferro et al., GCN 40853) 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 28 at 06:17:20 UT (i.e. 5.4 hr after the burst), and lasted for about 1 hour. From preliminary inspection, we do not detect any possible counterpart within the Swift/XRT error region (Evans et al., GCN 40854) down to the following 3sigma limits: r > 20.1 (AB; calibrated against the SkyMapper catalogue), at a mid-time of 5.9 hr after the trigger; H > 14.8 (Vega; calibrated against the 2MASS catalogue), at a mid-time of 5.4 hr after the trigger. View this GCN Circular online at https://gcn.nasa.gov/circulars/40865. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38908] GRB 250628C: Fermi GBM Final Real-time Localization
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40864 SUBJECT: GRB 250628C: Fermi GBM Final Real-time Localization DATE: 25/06/28 19:25:46 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 19:15:16 UT on 28 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250628C (trigger 772830921.339792 / 250628802). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 169.9, Dec = -6.9 (J2000 degrees, equivalent to J2000 11h 19m, -6d 54'), with a statistical uncertainty of 3.7 degrees. The angle from the Fermi LAT boresight is 11.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250628802/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250628802/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250628802/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40864. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38907] LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40863 SUBJECT: LIGO/Virgo/KAGRA S250628am: Identification of a GW compact binary merger candidate DATE: 25/06/28 19:08:45 GMT FROM: F. Llamas <francisco.llamas(a)ligo.org> The LIGO Scientific Collaboration, the Virgo Collaboration, and the KAGRA Collaboration report: We identified the compact binary merger candidate S250628am during real-time processing of data from LIGO Hanford Observatory (H1), LIGO Livingston Observatory (L1), and Virgo Observatory (V1) at 2025-06-28 18:23:19.785 UTC (GPS time: 1435170217.785). The candidate was found by the cWB [1], cWB BBH [2], GstLAL [3], MBTA [4], PyCBC Live [5], and SPIIR [6] analysis pipelines. S250628am is an event of interest because its false alarm rate, as estimated by the online analysis, is 1.7e-14 Hz, or about one in 1e6 years. The event's properties can be found at this URL: https://gracedb.ligo.org/superevents/S250628am The classification of the GW signal, in order of descending probability, is BBH (>99%), Terrestrial (<1%), NSBH (<1%), or BNS (<1%). Assuming the candidate is astrophysical in origin, the probability that at least one of the compact objects is consistent with a neutron star mass (HasNS) is <1%. [7] Using the masses and spins inferred from the signal, the probability of matter outside the final compact object (HasRemnant) is <1%. [7] Both HasNS and HasRemnant consider the support of several neutron star equations of state for maximum neutron star mass. The probability that either of the binary components lies between 3 and 5 solar masses (HasMassGap) is <1%. The source chirp mass falls with highest probability in the bin (5.5, 11.0) solar masses, assuming the candidate is astrophysical in origin. Two sky maps are available at this time and can be retrieved from the GraceDB event page: * bayestar.multiorder.fits,1, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 32 seconds after the candidate event time. * bayestar.multiorder.fits,2, an initial localization generated by BAYESTAR [8], distributed via GCN and SCiMMA notices about 5 minutes after the candidate event time. The preferred sky map at this time is bayestar.multiorder.fits,2. For the bayestar.multiorder.fits,2 sky map, the 90% credible region is 427 deg2. Marginalized over the whole sky, the a posteriori luminosity distance estimate is 1112 +/- 273 Mpc (a posteriori mean +/- standard deviation). For further information about analysis methodology and the contents of this alert, refer to the LIGO/Virgo/KAGRA Public Alerts User Guide https://emfollow.docs.ligo.org/. [1] Klimenko et al. PRD 93, 042004 (2016) doi:10.1103/PhysRevD.93.042004 [2] T. Mishra et al. PRD 105, 083018 (2022) doi:10.1103/PhysRevD.105.083018 [3] Tsukada et al. PRD 108, 043004 (2023) doi:10.1103/PhysRevD.108.043004 and Ewing et al. PRD 109, 042008 (2024) doi:10.1103/PhysRevD.109.042008 [4] Alléné et al. CQG 42, 105009 (2025) doi:10.1088/1361-6382/add234 [5] Dal Canton et al. ApJ 923, 254 (2021) doi:10.3847/1538-4357/ac2f9a [6] Chu et al. PRD 105, 024023 (2022) doi:10.1103/PhysRevD.105.024023 [7] Chatterjee et al. ApJ 896, 54 (2020) doi:10.3847/1538-4357/ab8dbe [8] Singer & Price PRD 93, 024013 (2016) doi:10.1103/PhysRevD.93.024013 View this GCN Circular online at https://gcn.nasa.gov/circulars/40863. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38906] GRB 250628B: SVOM detection of a long burst
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40862 SUBJECT: GRB 250628B: SVOM detection of a long burst DATE: 25/06/28 17:30:16 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> D. Dornic, J-G. Ducoin, J-L. Atteia, O. Godet, C. Plasse, report on behalf of the SVOM mission team: At 2025-06-28T16:29:30 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 250628B (SVOM burst-id sb25062804). 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 6.90 in the [5-20] keV energy band over a time window of 20.48 seconds starting at 2025-06-28T16:29:10. The localization of the best alert is R.A., Dec. 333.1563, -45.5663 degrees: R.A. (J2000) = 22h12m37.51s Dec. (J2000) = -45d33m58.52s with a 90% confidence level (C.L.) radius of 11.33 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a single/multiple broad/narrow peak structure with a T90 duration of about 33.51s (-3.02 +4.13). Due to the detection significance being below the slew threshold, no immediate slew was performed on this burst. A SVOM ToO has been programmed for follow-up. No X-ray observation could be performed by SVOM/MXT for the time being.No optical observation could be performed by SVOM/VT for the time being. 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. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Dornic Damien: dornic(a)cppm.in2p3.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/40862. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38905] Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40861 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772811638/250628579 is not a GRB DATE: 25/06/28 16:15:00 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 772811638/250628579 at 13:53:53.18 UT on 28 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/40861. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38904] GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40860 SUBJECT: GRB 250625A: VLT/X-shooter spectroscopic observations at the afterglow position DATE: 25/06/28 14:57:40 GMT FROM: J. An <jiean0813(a)foxmail.com> J. An (NAOC), B. Schneider (LAM), L. Izzo (INAF/OAC), R. Brivio (INAF/OABr), G. Corcoran (UCD), A. de Ugarte Postigo (LAM), B. P. Gompertz (Birmingham), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration: We observed the optical afterglow of GRB 250625A detected by Fermi/GBM (Godwin et al., GCN 40833) and Swift/BAT (Ferro et al., GCN 40825) using the ESO VLT UT3 (Melipal) equipped with the X-shooter spectrograph. Our spectra cover the wavelength range 3000-21000 AA, and consist of 4 exposures of 1200 s each. The observation mid time was 2025 Jun 27.128 UT (34.98 hr after the GRB). The slit was aligned to cover the optical afterglow (Moskvitin et al., GCN 40828; Xin et al., GCN 40830; Zhu et al., GCN 40834; Fortin et al., GCN 40837; Adami et al., GCN 40838; Brosio et al., GCN 40839; de Ugarte Postigo et al., GCN 40486). In a preliminary reduction of the spectra, we detect no obvious continuum nor any emission lines across the entire covered wavelength range. This could simply indicate that the emission lines of the actual (faint) GRB host galaxy are below our detection sensitivity, or, alternatively, would be consistent with an association with the nearby galaxy at z = 0.655 reported by de Ugarte Postigo et al. (GCN 40486). We acknowledge excellent support from the ESO observing staff in Paranal, in particular Célia Desgrange, Rodrigo Palominos, and Boris Häußler. We also thank Liping Xin (NAOC) and the SVOM/VT team for sharing accurate coordinates of the afterglow (see also GCN 40830). View this GCN Circular online at https://gcn.nasa.gov/circulars/40860. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38903] GRB 250628A: VLT/X-shooter upper limits
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40859 SUBJECT: GRB 250628A: VLT/X-shooter upper limits DATE: 25/06/28 14:12:36 GMT FROM: Riccardo Brivio at INAF-OAB <riccardo.brivio(a)inaf.it> R. Brivio (INAF-OABr), A. Martin-Carrillo (UCD), G. Corcoran (UCD), L. Izzo (INAF/OAC), A. Rossi (INAF/OAS), D. B. Malesani (DAWN/NBI and Radboud), N. R. Tanvir (Leicester) report on behalf of the Stargate collaboration: We observed the field of GRB 250628A detected by Swift/BAT (Ferro et al., GCN 40853) using the ESO VLT UT3 (Melipal) equipped with the X-shooter acquisition camera. A short sequence of imaging was secured in the r (3x30 s), g (3x40 s), and z (3x60 s) bands. No afterglow is detected within the Swift/XRT enhanced error region (Evans et al., GCN 40854). From preliminary analysis, we measure the following 3sigma upper limits, calibrated against nearby stars from the Legacy Survey (DR9): g > 23.7 (AB) on Jun 28 at 08:51:48 UT (7.93 hr after the GRB trigger), r > 23.6 (AB) on Jun 28 at 08:45:04 UT (7.82 hr after the GRB trigger), z > 22.8 (AB) on Jun 28 at 08:48:21 UT (7.87 hr after the GRB trigger). We note the detection of significant excess absorption in the X-ray spectrum (Evans, GCN 40857; https://www.swift.ac.uk/xrt_spectra/01328546/). This argues against a high-redshift origin for GRB 250628A and likely indicates some dust extinction. We acknowledge excellent support from the ESO observing staff in Paranal, in particular Boris Häußler. View this GCN Circular online at https://gcn.nasa.gov/circulars/40859. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38902] GRB 250628A: Swift/UVOT Upper Limits
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40858 SUBJECT: GRB 250628A: Swift/UVOT Upper Limits DATE: 25/06/28 12:44:42 GMT FROM: Paul Kuin at MSSL <npkuin(a)gmail.com> Paul Kuin (MSSL/UCL) and M Ferro (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250628A 130 s after the BAT trigger (Ferro et al., GCN Circ. 40853). No optical afterglow consistent with the enhanced XRT position (Evans et al. GCN Circ. 40854) is detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 130 280 147 >20.8 u_FC 342 591 246 >19.3 white 130 641 167 >20.8 v 671 691 19 >17.8 b 597 617 19 >18.5 u 342 591 246 >19.3 w1 720 740 19 >18.2 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.023 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40858. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38901] GRB 250628A: Swift-XRT refined Analysis
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40857 SUBJECT: GRB 250628A: Swift-XRT refined Analysis DATE: 25/06/28 10:41:22 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore (U. Leicester), J.P. Osborne (U. Leicester), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), B. Sbarufatti (INAF-OAB), J.A. Kennea (PSU), D.N. Burrows (PSU), M.A. Williams (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 8.2 ks of XRT data for GRB 250628A, from 127 s to 27.6 ks after the trigger. The data comprise 47 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=5.0 (+0.6, -0.5). At T+358 s the decay flattens to an alpha of -0.01 (+0.11, -0.13) before breaking again at T+14.4 ks to a final decay with index alpha=2.6 (+/-0.6). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.92 (+0.17, -0.16). The best-fitting absorption column is 3.2 (+0.8, -0.7) x 10^21 cm^-2, in excess of the Galactic value of 2.3 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.0 x 10^-11 (5.8 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 3.2 (+0.8, -0.7) x 10^21 cm^-2 Galactic foreground: 2.3 x 10^20 cm^-2 Excess significance: 6.8 sigma Photon index: 1.92 (+0.17, -0.16) If the light curve continues to decay with a power-law decay index of 2.6, the count rate at T+24 hours will be 1.6 x 10^-3 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.5 x 10^-14 (9.3 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01328546. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40857. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38900] Fermi GRB 250626A: Global MASTER-Net observations report
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40856 SUBJECT: Fermi GRB 250626A: Global MASTER-Net observations report DATE: 25/06/28 09:15:21 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-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) started inspect of the Fermi GRB 250626A ( Fermi GBM team, GCN 40845) errorbox 42909 sec after notice time and 42944 sec after trigger time at 2025-06-27 10:09:38 UT, with upper limit up to 20.6 mag. The observations began at zenith distance = 33 deg. The sun altitude is -17.4 deg. The galactic latitude b = -60 deg., longitude l = 174 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2917440 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 42975 | 2025-06-27 10:09:38 | MASTER-OAFA | (01h 27m 40.95s , -06d 22m 32.0s) | C | 60 | 20.0 | 43050 | 2025-06-27 10:10:53 | MASTER-OAFA | (01h 35m 38.27s , -06d 23m 08.1s) | C | 60 | 20.0 | 43110 | 2025-06-27 10:10:53 | MASTER-OAFA | (01h 35m 38.27s , -06d 23m 08.1s) | C | 180 | 20.6 | Coadd 43127 | 2025-06-27 10:12:11 | MASTER-OAFA | (01h 43m 25.19s , -08d 17m 09.9s) | C | 60 | 20.0 | 43187 | 2025-06-27 10:12:11 | MASTER-OAFA | (01h 43m 25.19s , -08d 17m 09.9s) | C | 180 | 20.5 | Coadd 43202 | 2025-06-27 10:13:26 | MASTER-OAFA | (01h 51m 23.61s , -08d 18m 09.1s) | C | 60 | 20.0 | 43262 | 2025-06-27 10:13:26 | MASTER-OAFA | (01h 51m 23.61s , -08d 18m 09.0s) | C | 180 | 20.6 | Coadd 43279 | 2025-06-27 10:14:43 | MASTER-OAFA | (01h 27m 42.13s , -06d 23m 32.1s) | C | 60 | 20.0 | 43356 | 2025-06-27 10:16:00 | MASTER-OAFA | (01h 35m 41.34s , -06d 22m 03.8s) | C | 60 | 20.0 | 43432 | 2025-06-27 10:17:15 | MASTER-OAFA | (01h 43m 21.97s , -08d 17m 48.3s) | C | 60 | 19.9 | 43507 | 2025-06-27 10:18:31 | MASTER-OAFA | (01h 51m 30.29s , -08d 16m 20.6s) | C | 60 | 19.9 | 43584 | 2025-06-27 10:19:48 | MASTER-OAFA | (01h 27m 36.11s , -06d 22m 51.4s) | C | 60 | 19.9 | 43662 | 2025-06-27 10:21:06 | MASTER-OAFA | (01h 35m 38.40s , -06d 21m 53.5s) | C | 60 | 19.9 | 43740 | 2025-06-27 10:22:24 | MASTER-OAFA | (01h 43m 24.60s , -08d 16m 55.6s) | C | 60 | 19.9 | 43817 | 2025-06-27 10:23:40 | MASTER-OAFA | (01h 51m 25.10s , -08d 17m 56.0s) | C | 60 | 19.9 | 43895 | 2025-06-27 10:24:58 | MASTER-OAFA | (01h 27m 42.16s , -06d 23m 26.4s) | C | 60 | 19.9 | 43955 | 2025-06-27 10:24:58 | MASTER-OAFA | (01h 27m 42.16s , -06d 23m 26.4s) | C | 180 | 20.4 | Coadd 43976 | 2025-06-27 10:26:20 | MASTER-OAFA | (01h 35m 41.71s , -06d 22m 14.2s) | C | 60 | 19.7 | 44036 | 2025-06-27 10:26:20 | MASTER-OAFA | (01h 35m 41.71s , -06d 22m 14.2s) | C | 180 | 20.3 | Coadd 44052 | 2025-06-27 10:27:35 | MASTER-OAFA | (01h 43m 22.34s , -08d 17m 41.1s) | C | 60 | 19.7 | 44128 | 2025-06-27 10:28:51 | MASTER-OAFA | (01h 51m 30.01s , -08d 16m 15.3s) | C | 60 | 19.9 | 44188 | 2025-06-27 10:28:51 | MASTER-OAFA | (01h 51m 30.01s , -08d 16m 15.3s) | C | 180 | 20.1 | Coadd 44205 | 2025-06-27 10:30:08 | MASTER-OAFA | (01h 27m 36.78s , -06d 22m 37.6s) | C | 60 | 19.6 | 44280 | 2025-06-27 10:31:23 | MASTER-OAFA | (01h 35m 38.45s , -06d 21m 40.2s) | C | 60 | 19.7 | 44357 | 2025-06-27 10:32:40 | MASTER-OAFA | (01h 43m 24.82s , -08d 16m 42.8s) | C | 60 | 19.6 | 44432 | 2025-06-27 10:33:55 | MASTER-OAFA | (01h 51m 24.68s , -08d 17m 43.2s) | C | 60 | 19.4 | 44509 | 2025-06-27 10:35:12 | MASTER-OAFA | (01h 27m 41.68s , -06d 23m 28.0s) | C | 60 | 19.3 | 44586 | 2025-06-27 10:36:29 | MASTER-OAFA | (01h 35m 42.04s , -06d 21m 57.7s) | C | 60 | 19.1 | 44661 | 2025-06-27 10:37:44 | MASTER-OAFA | (01h 43m 22.75s , -08d 17m 23.0s) | C | 60 | 19.2 | 44737 | 2025-06-27 10:39:00 | MASTER-OAFA | (01h 51m 30.94s , -08d 15m 47.5s) | C | 60 | 19.0 | 44813 | 2025-06-27 10:40:16 | MASTER-OAFA | (01h 27m 36.58s , -06d 22m 24.0s) | C | 60 | 18.7 | 44891 | 2025-06-27 10:41:35 | MASTER-OAFA | (01h 35m 38.99s , -06d 21m 26.8s) | C | 60 | 18.7 | 44967 | 2025-06-27 10:42:50 | MASTER-OAFA | (01h 43m 25.32s , -08d 16m 28.8s) | C | 60 | 18.5 | 45041 | 2025-06-27 10:44:05 | MASTER-OAFA | (01h 51m 24.79s , -08d 17m 30.2s) | C | 60 | 18.5 | 45119 | 2025-06-27 10:45:22 | MASTER-OAFA | (01h 27m 41.21s , -06d 23m 11.7s) | C | 60 | 18.2 | 45195 | 2025-06-27 10:46:39 | MASTER-OAFA | (01h 35m 42.25s , -06d 21m 27.0s) | C | 60 | 18.1 | 45270 | 2025-06-27 10:47:54 | MASTER-OAFA | (01h 43m 23.07s , -08d 17m 00.6s) | C | 60 | 16.4 | 123302 | 2025-06-28 08:28:25 | MASTER-OAFA | (01h 34m 53.55s , -07d 07m 29.7s) | C | 60 | 19.8 | 123376 | 2025-06-28 08:29:39 | MASTER-OAFA | (01h 34m 53.39s , -07d 06m 26.5s) | C | 60 | 19.8 | 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/40856. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38899] Swift GRB 250628A: Global MASTER-Net observations report
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40855 SUBJECT: Swift GRB 250628A: Global MASTER-Net observations report DATE: 25/06/28 05:58:35 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-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 Swift GRB 250628A ( M. Ferro et al., GCN 40853) errorbox 17683 sec after notice time and 17722 sec after trigger time at 2025-06-28 05:51:18 UT, with upper limit up to 16.0 mag. The observations began at zenith distance = 81 deg. The sun altitude is -72.0 deg. The galactic latitude b = -66 deg., longitude l = 246 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2918453 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 17812 | MASTER-OAFA | C | 180 | 16.0 | 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/40855. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38898] GRB 250628A: Enhanced Swift-XRT position
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40854 SUBJECT: GRB 250628A: Enhanced Swift-XRT position DATE: 25/06/28 04:48:11 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> P.A. Evans, M.R. Goad, J.P. Osborne and A.P. Beardmore (U. Leicester) report on behalf of the Swift-XRT team. Using 1647 s of XRT Photon Counting mode data and 4 UVOT images for GRB 250628A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 38.55311, -38.07894 which is equivalent to: RA (J2000): 02h 34m 12.75s Dec (J2000): -38d 04' 44.2" with an uncertainty of 2.4 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40854. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38897] GRB 250628A: Swift detection of a burst
by GCN Circulars 28 Jun '25

28 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40853 SUBJECT: GRB 250628A: Swift detection of a burst DATE: 25/06/28 01:13:26 GMT FROM: James DeLaunay at PSU <jjd330(a)psu.edu> M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC) and D. M. Palmer (LANL) report on behalf of the Neil Gehrels Swift Observatory Team: At 00:55:56.71 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250628A (trigger=1328546). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 38.551, -38.081 which is RA(J2000) = 02h 34m 12s Dec(J2000) = -38d 04' 50" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed two emission pulses with the first brighter pulse starting from T0-20 sec to T0+20 sec and the second fainter pulse from T0+25 end T0+60 sec. The peak count rate was ~1066 counts/sec (15-350 keV), at ~1 sec after the trigger. The XRT began observing the field at 00:57:57.7 UT, 121.1 seconds after the BAT trigger. Using promptly downlinked data we find a bright, uncatalogued X-ray source with an enhanced position: RA, Dec 38.55240, -38.07909 which is equivalent to: RA(J2000) = 02h 34m 12.58s Dec(J2000) = -38d 04' 44.7" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 7.9 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (2.30 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 4.1 (+4.01/-3.17) x 10^21 cm^-2 (90% confidence). The initial flux in the 2.5 s image was 9.47e-10 erg cm^-2 s^-1 (0.2-10 keV). UVOT took a finding chart exposure of 150 seconds with the White filter starting 129 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.023. Burst Advocate for this burst is M. Ferro (matteo.ferro AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/40853. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38896] GRB 250625A: Swift-BAT refined analysis
by GCN Circulars 27 Jun '25

27 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40852 SUBJECT: GRB 250625A: Swift-BAT refined analysis DATE: 25/06/27 23:16:03 GMT FROM: Amy <yarleen(a)gmail.com> A. Y. Lien (U Tampa), S. D. Barthelmy (GSFC), M. Ferro (INAF-OAB), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), 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+100 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250625A (trigger #1327910) (Ferro et al., GCN Circ. 40825). The BAT ground-calculated position is RA, Dec = 261.517, 22.245 deg which is RA(J2000) = 17h 26m 04.1s Dec(J2000) = +22d 14' 40.7" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 68%. The mask-weighted light curve shows a single-pulse structure that starts at ~T0, peaks at ~T+2 s, and ends at ~T+6 s. T90 (15-350 keV) is 4.00 +- 1.41 sec (estimated error including systematics). The time-averaged spectrum from T-0.35 to T+3.65 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.00 +- 0.22. The fluence in the 15-150 keV band is 2.8 +- 0.4 x 10^-07 erg/cm2. The 1-sec peak photon flux measured from T+1.65 sec in the 15-150 keV band is 0.8 +- 0.2 ph/cm2/sec. 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/1327910 View this GCN Circular online at https://gcn.nasa.gov/circulars/40852. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38895] GRB 250625A: Leavitt Observatory afterglow detection
by GCN Circulars 27 Jun '25

27 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40851 SUBJECT: GRB 250625A: Leavitt Observatory afterglow detection DATE: 25/06/27 19:20:11 GMT FROM: leavittob(a)gmail.com L. Moretti, E. Pavoni (Leavitt Observatory, Italy) Members of: GRB/UAI - Gamma Ray Burst Section of Unione Astrofili Italiani ATA - Associazione Tuscolana di Astronomia In a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy), K. Kalinowski (Aarhus University, Department of Physics and Astronomy), report: We imaged the field of GRB 250625A, which was detected by Swift-BA (Ferro et al., GCN 40825) and Fermi-GBM (GCN 40824) with our RC telescope (D=250 mm, F/D=8) of Leavitt Observatory. The observations began approximately 4.6 hours after the trigger, with good weather conditions, stacking a series of 12 exposures of 120 seconds each. All images are unfiltered and were processed by a single data processing pipeline based on astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). In the stacked frame, we detected a very faint object at the following position: R.A. (J2000) = 17:26:01.92 Dec. (J2000) = +22:16:04.31 with the following photometry: Date UT at mid-exposure Filter Mag. Err. 2025-06-25 20:58:29 UTC CR 21.4 +/-0.2 CR magnitude is unfiltered with R zero point. Magnitudes were estimated with the Pan-STARRS cat. and are derived using Lupton (2005) equations. Not corrected for galactic dust extinction. This measure is consistent with the optical afterglow reported by Moskvitin et al. (GCN 40828), Xin et al. (GCN 40830), Zhu et al. (GCN 40834), Fortin et al. (GCN 40837), Adami et al. (GCN 40838), Brosio et al. (GCN 40839), Wang et al. (GCN 40841), Ruocco et al. (GCN 40843), de Ugarte Postigo et al. (GCN 40846). The message may be cited. Reference: https://leavittobservatory.altervista.org View this GCN Circular online at https://gcn.nasa.gov/circulars/40851. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38894] Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB
by GCN Circulars 27 Jun '25

27 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40850 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772732642/250627665 is not a GRB DATE: 25/06/27 17:30:12 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> L. Scotton (UAH) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 772732642/250627665 at 15:57:17.97 UT on 27 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/40850. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38893] Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB
by GCN Circulars 27 Jun '25

27 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40849 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772720540/250627525 is not a GRB DATE: 25/06/27 13:51:38 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova (MUNI) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "The Fermi Gamma-ray Burst Monitor (GBM) trigger 772720540/250627525 at 12:35:35.78 UT on 27 June 2025, tentatively classified as a GRB, is in fact not due to a GRB. This trigger is likely due to SAA entry." View this GCN Circular online at https://gcn.nasa.gov/circulars/40849. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38892] GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations
by GCN Circulars 27 Jun '25

27 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40848 SUBJECT: GRB 250625A: AbAO and INASAN Kislovodsk Optical Observations DATE: 25/06/27 11:55:09 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), R. Ya. Inasaridze (AbAO), A. Tarasenkov (INASAN), A. Pozanenko (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 250625A (Fermi GBM Team, GCN 40824; Ferro et al., GCN 40825; Beardmore et al., GCN 40827; Dichiara et al., GCN 40835; Di Lalla et al., GCN 40836) using the 0.7-meter AS-32 telescope of Abastumani Observatory (AbAO) and the 0.5-meter RC-500 telescope of INASAN Kislovodsk Observatory. The observations at AbAO started on 2025-06-25 at 17:41:35 UT and consisted of 71*60 sec exposures. The observations at RC-500 were carried out between 2025-06-25 18:19:40 UT and 2025-06-26 00:09:04 UT using 120 sec exposures. We do not detect the optical afterglow reported/followed by (Moskvitin et al., GCN 40828, Xin et al., GCN 40830; Malesani et al., GCN 40831; Lipunov et al., GCN 40826/40832; Zhu et al., GCN 40834, Fortin et al., GCN 40837; Adami et. al, GCN 40838; Brosio et. al, GCN 40839; Breeveld & Ferro, GCN 40840; WU et. al, GCN 40842; Ruocco et. al, GCN 40843; de Ugarte Postigo et. al, GCN 40846) in the R-band co-add images. The preliminary photometry is as follows: Date UT start t-T0 Exp. Filter OT Err. UL Telescope (mid, days) (n*s) (3sigma) 2025-06-25 17:41:35 0.09176 71*60 R n/d n/d 20.0 AS-32 2025-06-25 18:38:08 0.14735 59*120 R n/d n/d 21.5 RC-500 The photometry has calibrated using stars from USNO-B1.0 (see Moskvitin et al., GCN 40828) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40848. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38891] The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
by GCN Circulars 27 Jun '25

27 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40847 SUBJECT: The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg DATE: 25/06/27 04:28:06 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> B.-T. Wang (YNAO,CAS), J. H. Wu (GZHU), W. F. Wen(SZTU), J. W. Hu, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709179435 at the time of 2025-06-27T03:38:47, is likely a new outburst associated with CV SS Cyg. The estimated flux of the outburst is around 2e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 3e+32 erg/s. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40847. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38890] GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40846 SUBJECT: GRB 250625A: GTC/OSIRIS+ spectroscopic observations of the potential host galaxy DATE: 25/06/26 23:08:02 GMT FROM: Antonio de Ugarte Postigo at LAM, CNRS <adeugartepostigo(a)gmail.com> A. de Ugarte Postigo (LAM), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), J. F. Agui Fernandez (CAHA), M. A. Aloy (UV), J. P. U. Fynbo (DAWN/NBI), L. Galbany (IEEC-CSIC), S. Geier (GTC), B. Schneider (LAM), L. Izzo (INAF/OACN and DARK/NBI), G. Lombardi (GTC), N. A. Rakotondrainibe (LAM), N. R. Tanvir (Univ. Leicester), C. C. Thoene (AbAO), F. Pérez (GTC), D. Pérez Valladares (GTC) and A. Cabrera Lavers (GTC) report: We observed the optical afterglow of the GRB 250607A detected by Fermi/GBM and Swift/BAT (Fermi GBM team, GCN 40824; Ferro et al., GCN 40825) using the 10.4 m GTC located at the Roque de los Muchachos Observatory in the island of La Palma (Spain) equipped with the OSIRIS+ instrument. In a 3x30 s acquisition image in the z-band, with a mean time of 2025-06-26T01:09:07 (~9.07 hr after the Swift trigger), we detect two objects consistently with the Swift/XRT position (REF). The first is the optical afterglow reported by Moskvitin et al. (GCN 40828), Xin et al. (GCN 40830), Zhu et al. (GCN 40834), Fortin et al. (GCN 40837), Adami et al. (GCN 40838) and Brosio et al. (GCN 40839), for which we measure a magnitude z = 23.75 +/- 0.20 (AB, calibrated against nearby Legacy Survey objects). The second (at RA =17:26:02.17, Dec = +22:16:02.8) has an AB magnitude z = 23.69 +/- 0.18, with a separation of ~1.4" from the afterglow. Our spectroscopic observations started on 2025-06-26T01:44:27.5 UT (9.67 hr after the Swift trigger) and consisted of 3x1200 s exposures using grism R1000R, covering the range between 5100 and 10,000 AA. In the acquisition process, the slit was placed on top of this second object, not the afterglow. For this target, in a preliminary reduction of the spectra, we detect a continuum and a few emission lines, including the [O II] doublet, [O III] 5008 and H-beta, from which we infer a redshift of z = 0.655. At this distance, if this galaxy is associated with the optical afterglow, the offset between the galaxy and the optical afterglow would be ~10 kpc. We note that the probability of chance coincidence is not negligible (~2.5%). We cannot thus conclude that GRB 250625A is at redshift z = 0.655. Further observations to confirm their association are planned and encouraged. We thank Liping Xin (NAOC) for sharing accurate coordinates of the afterglow from SVOM/VT. View this GCN Circular online at https://gcn.nasa.gov/circulars/40846. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38889] GRB 250626A: Fermi GBM Final Real-time Localization
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40845 SUBJECT: GRB 250626A: Fermi GBM Final Real-time Localization DATE: 25/06/26 22:24:29 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 SHORT GRB At 22:13:53 UT on 26 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250626A (trigger 772668838.960546 / 250626926). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 35.5, Dec = -6.6 (J2000 degrees, equivalent to J2000 02h 22m, -6d 35'), with a statistical uncertainty of 19.9 degrees. The angle from the Fermi LAT boresight is 58.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250626926/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250626926/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250626926/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40845. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38888] Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40844 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772647532/250626680 is not a GRB DATE: 25/06/26 17:15:57 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 772647532/250626680 at 16:18:47.72 UT on 26 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/40844. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38887] GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40843 SUBJECT: GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart DATE: 25/06/26 17:11:34 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the Swift trigger no. 1327910 (GCN 40825 M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU),R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL),B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf ofthe Neil Gehrels Swift Observatory Team) from the Swift Burst Alert Telescope (BAT), we pointed at the coordinates RA(J2000)=17h 26m 02.09s: Dec(J2000)= +22d 16' 03.5" and started our observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. The observations started at 19:30 UT of 2025/06/25, after about 3.30 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME I took 13 unfiltered images of 120 sec . Start End 19:30:01 UT 19:56:45 UT All images, calibrated with masterdark and masterflat have been measured with Thycho Tracker software We have detected a faint source at the enhanced position reported by Swift Burst Alert Telescope (BAT) at following position RA (J2000.0) 17 26 02.13 Dec (J2000.0) +22 16 07.7 with the following photometry and astrometry: GRB 250625A 17 26 02.13 +22 16 07.7 20.2 V C82 Magnitudes were estimated with the ATLAS cat. and are not corrected for galactic dust extinction. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38886] GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40843 SUBJECT: GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart DATE: 25/06/26 17:11:34 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the Swift trigger no. 1327910 (GCN 40825 M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU),R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL),B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf ofthe Neil Gehrels Swift Observatory Team) from the Swift Burst Alert Telescope (BAT), we pointed at the coordinates RA(J2000)=17h 26m 02.09s: Dec(J2000)= +22d 16' 03.5" and started our observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. The observations started at 19:30 UT of 2025/06/25, after about 3.30 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME I took 13 unfiltered images of 120 sec . Start End 19:30:01 UT 19:56:45 UT All images, calibrated with masterdark and masterflat have been measured with Thycho Tracker software We have detected a faint source at the enhanced position reported by Swift Burst Alert Telescope (BAT) at following position RA (J2000.0) 17 26 02.13 Dec (J2000.0) +22 16 07.7 with the following photometry and astrometry: GRB 250625A 17 26 02.13 +22 16 07.7 20.2 V C82 Magnitudes were estimated with the ATLAS cat. and are not corrected for galactic dust extinction. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38885] GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40843 SUBJECT: GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart DATE: 25/06/26 17:11:34 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the Swift trigger no. 1327910 (GCN 40825 M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU),R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL),B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf ofthe Neil Gehrels Swift Observatory Team) from the Swift Burst Alert Telescope (BAT), we pointed at the coordinates RA(J2000)=17h 26m 02.09s: Dec(J2000)= +22d 16' 03.5" and started our observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. The observations started at 19:30 UT of 2025/06/25, after about 3.30 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME I took 13 unfiltered images of 120 sec . Start End 19:30:01 UT 19:56:45 UT All images, calibrated with masterdark and masterflat have been measured with Thycho Tracker software We have detected a faint source at the enhanced position reported by Swift Burst Alert Telescope (BAT) at following position RA (J2000.0) 17 26 02.13 Dec (J2000.0) +22 16 07.7 with the following photometry and astrometry: GRB 250625A 17 26 02.13 +22 16 07.7 20.2 V C82 Magnitudes were estimated with the ATLAS cat. and are not corrected for galactic dust extinction. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38884] GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40843 SUBJECT: GRB 250625A: Osservatorio Astronomico "Nastro Verde" optical observations: detection of an optical counterpart DATE: 25/06/26 17:11:34 GMT FROM: Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy - MPC Code C82 <osservatorionastroverde(a)gmail.com> Nello Ruocco at Osservatorio Nastro Verde - Sorrento (Naples) - Italy in a large collaboration with: M.G. Dainotti (National Astronomical Observatory of Japan), Y. Niino (Tokyo University, Institute of Astronomy) and K. Kalinowski (Aarhus University, Department of Physics and Astronomy) report: Following the Swift trigger no. 1327910 (GCN 40825 M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU),R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL),B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf ofthe Neil Gehrels Swift Observatory Team) from the Swift Burst Alert Telescope (BAT), we pointed at the coordinates RA(J2000)=17h 26m 02.09s: Dec(J2000)= +22d 16' 03.5" and started our observations with telescope of Nastro Verde Observatory - Sorrento (Naples), Italy. Member of: AAVSO - American Association of Variable Star Observers. GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. The observations started at 19:30 UT of 2025/06/25, after about 3.30 hours after the GRB trigger, with clear sky, with principal telescope SC 0.35 f/10 with focal reduced + CCD Sbig ST10 XME I took 13 unfiltered images of 120 sec . Start End 19:30:01 UT 19:56:45 UT All images, calibrated with masterdark and masterflat have been measured with Thycho Tracker software We have detected a faint source at the enhanced position reported by Swift Burst Alert Telescope (BAT) at following position RA (J2000.0) 17 26 02.13 Dec (J2000.0) +22 16 07.7 with the following photometry and astrometry: GRB 250625A 17 26 02.13 +22 16 07.7 20.2 V C82 Magnitudes were estimated with the ATLAS cat. and are not corrected for galactic dust extinction. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40843. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38883] GRB 250625A: SVOM/C-GFT upper limit in early phase
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40842 SUBJECT: GRB 250625A: SVOM/C-GFT upper limit in early phase DATE: 25/06/26 15:29:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chao WU (NAOC), Zhe Kang (CHO), Liping Xin(NAOC), Xuhui Han(NAOC), Pinpin Zhang (NAOC), Xiaomeng Lu (NAOC), Zhenwei Li (CHO), You Lv (CHO), Ruosong Zhang (NAOC), Yujie Xiao(NAOC), Yulei, Qiu(NAOC), Jing Wang (NAOC), Jinsong Deng(NAOC), Lei Huang(NAOC), Jianyan Wei (NAOC), report on behalf of the SVOM/C-GFT team: We observed the field of GRB 250625A detected by Swift-BAT（Ferro et al., GCN 40825) and Fermi-GBM (GCN 40824) with LATIOS on SVOM/C-GFT. Observations started at 2025-06-25T16:06:18 UTC, ~82 seconds after the trigger. A series of g, r, and i band images were obtained. The optical afterglow reported by Moskvitin et al. (GCN 40828), Xin et al. (GCN 40830), Zhu et al. (GCN 40834), Fortin et al. (GCN 40837), Adami et al. (GCN 40838) and Brosio et al. (GCN 40839) is not detected in the images after preliminary processing. The three sigma upper limits are: | date-obs|mid-time | exposure time (s) | band | upper limit (AB) | |--------------------|-------------------|------|-------------------| |2025-06-25T16:08:18 | 170 | i | 20.00 | |2025-06-25T16:27:53 | 180 | g | 20.59 | |2025-06-25T16:31:28 | 180 | r | 20.52 | The photometry was calibrated with nearby UCAC4 catalogue. This result is consistent with the report by Breeveld & Ferro (GCN 40840). We thank the observation assistants Chunlei Guo and Shuai Liu at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/40842. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38882] GRB 250625A: GECAM-B detection
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40841 SUBJECT: GRB 250625A: GECAM-B detection DATE: 25/06/26 14:18:47 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 250625A at 2025-06-25T16:04:56 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40824), Swift/BAT (David Palmer et al., GCN#40825), Fermi/LAT (Davide Depalo et al., GCN#40836). According to the GECAM-B light curves in about 40-6000 keV, this burst mainly consists of a single pulse with a duration (T90) of 6.0 +3.5/-5.5 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecamgrb250625A.png The time-averaged spectrum from T0 to T0+4 s is best fitted by a power law function. The power law index is -1.52 +0.29/-0.20. The event fluence (10-1000 keV) in this time interval is (1.39 +/-0.24)E-06 erg/cm^2. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/40841. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38881] GRB 250625A: Swift/UVOT Upper Limits
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40840 SUBJECT: GRB 250625A: Swift/UVOT Upper Limits DATE: 25/06/26 11:21:27 GMT FROM: Alice Breeveld at MSSL-UCL <a.breeveld(a)ucl.ac.uk> A.A. Breeveld (UCL-MSSL) and M. Ferro (INAF-OAB) report on behalf of the Swift/UVOT team: The Swift/UVOT began settled observations of the field of GRB 250625A 125 s after the BAT trigger (Ferro et al., GCN Circ. 40825). The optical afterglow reported by Moskvitin et al. (GCN Circ. 40828), Xin et al. (GCN Cir. 40830), Zhu et al. (GCN Circ. 40834) Fortin et al. (GCN Circ. 40837), Adami et al. (GCN Circ. 40838) and Brosio et al. (GCN Circ. 40839) is not detected in the initial UVOT exposures. Preliminary 3-sigma upper limits using the UVOT photometric system (Breeveld et al. 2011, AIP Conf. Proc. 1358, 373) for the first finding chart (FC) exposure and subsequent exposures are: Filter T_start(s) T_stop(s) Exp(s) Mag white_FC 125 275 147 >20.9 u_FC 283 533 246 >20.5 white 125 1529 392 >21.7 v 613 1579 117 >19.2 b 539 1505 97 >20.4 u 283 1480 324 >20.6 w1 662 1628 117 >19.6 m2 637 1431 78 >20.1 w2 589 1383 97 >20.6 The magnitudes in the table are not corrected for the Galactic extinction due to the reddening of E(B-V) = 0.054 in the direction of the burst (Schlegel et al. 1998). View this GCN Circular online at https://gcn.nasa.gov/circulars/40840. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38880] GRB 250625A: ABObservatory afterglow detection
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40839 SUBJECT: GRB 250625A: ABObservatory afterglow detection DATE: 25/06/26 11:06:58 GMT FROM: A. Brosio at ABObservatory Rosarno <antonino.brosio(a)gmail.com> A. Brosio (ABObservatory Rosarno), S. Savaglio (University of Calabria), G. Bracco, P. Cianfarra, L. Sangaletti, S. Tosi & S. Zappatore (University of Genoa), S. Benatti & M. G. Guarcello (INAF Palermo), L. Cabona, M. Rainer & F. M. Zerbi (INAF Brera), D. Ricci (INAF Padova), A. Di Dato (INAF Capodimonte), S. Masiero & A. Nastasi (GAL Hassin), D. Liguori (Osservatorio "G. Galilei" Cariati), L. Betti (Osservatorio Polifunzionale del Chianti), R. Nesci (Associazione Astronomica Antares APS di Foligno), for the NOCTIS team report We observed the field of GRB 250625A, which was detected by Swift-BA (Ferro et al., GCN 40825) and Fermi-GBM (GCN #40824) with the 30-cm automated telescope at ABObservatory (Rosarno, Italy) in clear filter. The observations began on 2025 june 25 at 19:34:37 UT, approximately 3.34 hours after the trigger. The observation consisted of 85 exposures of 90 seconds each, with good sky condictions. The mid-exposure time was 20:21:42 UT, and the final exposure ended at 21:09:59 UT. From photometry, we detect the optical counterpart in our images at the at the following coordinates: R.A (J2000.0) = 17:26:01.56 Dec. (J2000.0) = +22 16 12.3 The measured magnitude is: V = 21.13 +/- 0.28 with SNR 5.4 (AB, calibrated against the Pan-STARRS catalogue on SIMBAD). View this GCN Circular online at https://gcn.nasa.gov/circulars/40839. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38879] GRB 250625A: OHP/T193 optical detection
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40838 SUBJECT: GRB 250625A: OHP/T193 optical detection DATE: 25/06/26 11:02:44 GMT FROM: Christophe Adami at LAM <christophe.adami(a)lam.fr> C. Adami (LAM/Pytheas/AMU), S. Basa (LAM/OHP/Pytheas/AMU), B. Schneider (LAM), E. Le Floc'h (CEA/Irfu), A. Ugarte Postigo (LAM), M. Dennefeld (IAP/CNRS/Sorbonne U.), report on behalf of a larger collaboration: We observed the field of the GRB 250625A (Fermi GBM Team, GCN 40824; Ferro et al., GCN 40825; Beardmore et al., GCN 40827; Dichiara et al., GCN 40835; Di Lalla et al., GCN 40836) using the T193cm telescope at Observatoire de Haute-Provence (France) equipped with the MISTRAL spectro-imager. We obtained 8 exposures (for a total of 81min) in the r-band starting at 20:34:39 UT on 2025-06-25 (4.50 hours after the trigger). We also obtained 2 exposures (for a total of 30min) in the i-band starting at 22:28:55 UT on 2025-06-25 (6.40 hours after the trigger). In the stacked images, we detected the optical counterpart reported/followed by Moskvitin et al., GCN 40828, Xin et al., GCN 40830; Malesani et al., GCN 40831; Lipunov et al., GCN 40826/40832; Zhu et al., GCN 40834, Fortin et al., GCN 40837; in the r-band image. The preliminary magnitude derived for that source is: r = 22.95 +/- 0.23 mag (AB) We do not detect the optical counterpart in the i-band image with a 3-sigma upper limit of: i < 22.2 The photometric calibration was performed using nearby stars from the PanSTARRS catalog and the magnitudes are not corrected for Galactic extinction. We used the STDWeb/STDPipe tools (Karpov 2025). We acknowledge the excellent support from the Observatoire de Haute-Provence and in particular Jean Balcaen and R.P. Nelson for the MISTRAL observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40838. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38878] GRB 250625A: COLIBRÍ optical observations
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40837 SUBJECT: GRB 250625A: COLIBRÍ optical observations DATE: 25/06/26 09:35:11 GMT FROM: F. Fortin at IRAP <ffortin.sci.edu(a)gmail.com> Francis Fortin (IRAP), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Fredd Alvarez (UNAM), Camila Angulo (UNAM), Dalya Akl (AUS), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM): We imaged the field of the Fermi/Swift co-detection of GRB 250625A (Fermi GBM Team, GCN Circ. 40824, Ferro et al., GCN Circ. 40825) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-06-26T03:42:43 to 05:49:43 UTC (from 11.41 to 13.53 hours after the trigger) and obtained 32 minutes of exposure in each of the g, r and i filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. We detected the optical counterpart reported by Moskvitin et al. (GCN 40828), Xin et al. (GCN 40830), and Zhu et al. (GCN 40834), at a magnitude of: g = 24.22 +/- 0.34 r = 23.43 +/- 0.21 i = 24.01 +/- 0.58 Further observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. View this GCN Circular online at https://gcn.nasa.gov/circulars/40837. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38877] GRB 250625A: Fermi-LAT detection
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40836 SUBJECT: GRB 250625A: Fermi-LAT detection DATE: 25/06/26 08:10:58 GMT FROM: Davide Depalo at Politecnico and INFN Bari <davide.depalo(a)ba.infn.it> N. Di Lalla (Stanford Univ.), A. Holzmann Airasca (UniTrento and INFN Bari), R. Gupta (NASA GSFC), and D. Depalo (Politecnico and INFN Bari) report on behalf of the Fermi-LAT Collaboration: On June 25, 2025, Fermi-LAT detected high-energy emission from GRB 250625A, which was also detected by Fermi-GBM (trigger 772560301 / 250625670, GCN 40824), Swift-BAT/XRT (GCN 40825) and SVOM/VT (GCN 40830). The best LAT on-ground location is found to be: RA, Dec = 261.2, 22.4 (J2000) with an error radius of 0.6 deg (90 % containment, statistical error only). This was 32 deg from the LAT boresight at the time of the GBM trigger (T0 = 16:04:57.51 UT). The data from the Fermi-LAT shows a significant increase in the event rate that is spatially and temporally correlated with the GBM emission with high significance. The photon flux above 100 MeV in the time interval 0 - 100 s after the GBM trigger is (1.12 ± 0.48) E-5 ph/cm2/s. The estimated photon index above 100 MeV is -2.00 ± 0.38. The highest-energy photon is a 580 MeV event which is observed ~ 27 seconds after the GBM trigger. The Fermi-LAT point of contact for this burst is Davide Depalo (d.depalo2(a)phd.poliba.it). 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/40836. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38876] GRB 250625A: Swift-XRT refined Analysis
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40835 SUBJECT: GRB 250625A: Swift-XRT refined Analysis DATE: 25/06/26 05:57:53 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> S. Dichiara (PSU), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Capalbi (INAF-OAR), M. Perri (SSDC & INAF-OAR), V. D'Elia (SSDC & INAF-OAR), J.A. Kennea (PSU), D.N. Burrows (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 6.0 ks of XRT data for GRB 250625A, from 123 s to 45.1 ks after the trigger. The data comprise 58 s in Windowed Timing (WT) mode with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a series of power-law decays. The initial decay index is alpha=0.8 (+1.1, -1.2). At T+174 s the decay steepens to an alpha of 6.3 (+/-1.7) before breaking again at T+238 s to a final decay with index alpha=1.19 (+0.17, -0.15). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.68 (+0.32, -0.29). The best-fitting absorption column is 1.7 (+1.3, -1.0) x 10^21 cm^-2, in excess of the Galactic value of 5.5 x 10^20 cm^-2 (Willingale et al. 2013). The counts to observed (unabsorbed) 0.3-10 keV flux conversion factor deduced from this spectrum is 4.3 x 10^-11 (5.2 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 1.7 (+1.3, -1.0) x 10^21 cm^-2 Galactic foreground: 5.5 x 10^20 cm^-2 Excess significance: 1.9 sigma Photon index: 1.68 (+0.32, -0.29) If the light curve continues to decay with a power-law decay index of 1.19, the count rate at T+24 hours will be 5.0 x 10^-4 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 2.2 x 10^-14 (2.6 x 10^-14) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01327910. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40835. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38875] GRB 250625A: JinShan optical observations
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40834 SUBJECT: GRB 250625A: JinShan optical observations DATE: 25/06/26 04:25:58 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.P. Zhu, S.Q. Jiang, X. Liu, J. An, D. Xu (NAOC), S.Y. Fu (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of GRB 250625A detected by the Fermi/GBM and Swift/BAT (the Fermi GBM Team, GCN 40824; Ferro et al., GCN 40825), using the 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. Observations started at 16:11:04 UT on 2025-06-25, i.e., 6.1 min after the BAT trigger, and a series of frames were obtained in the Sloan r-, i-, z-bands. In the first round of r-band exposures, an uncatalogued optical source is marginally detected within the Swift/XRT enhanced error circle (Beardmore et al., GCN 40827), which is consistent with the reported optical counterpart by SAO RAS (Moskvitin et al., GCN 40828) and SVOM/VT (Xin et al., GCN 40830). The source is not detected in i-band and z-band (see also Malesani et al., GCN 40831), as well as in the second r-band exposures. Our preliminary results are summarized as follows: T-mid (hr) | Filter | Mag 0.387 | r | 22.5 +/- 0.3 1.237 | i | > 21.7 (5$\sigma$) 1.935 | z | > 20.5 (5$\sigma$) 2.761 | r | > 21.1 (5$\sigma$) calibrated with nearby Pan-STARRS stars without the Galactic extinction correction. We acknowledge the excellent support from T.Q. Chen and J.L. He for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/40834. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38874] GRB250625A: Fermi GBM Observation
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40833 SUBJECT: GRB250625A: Fermi GBM Observation DATE: 25/06/26 03:47:05 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH), O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:04:57.51 UT on 25 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB250625A (trigger 772560302/250625670). Which was also detected by Swift BAT/XRT (Ferro et al. 2025, GCN 40825) and SVOM/VT (Xin et al. 2025, GCN 40830). The Fermi GBM on-ground location is consistent with the Swift position. The angle from the Fermi LAT boresight is 32 degrees. The GBM light curve consists of one strong peak and a few weaker peaks with a duration (T90) of about 5.4 s (50-300 keV). The time-averaged spectrum from T0-2.0 to T0+5.0 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.27 +/- 0.05 and the cutoff energy, parameterized as Epeak, is 1301.00 +/- 1190.00 The event fluence (10-1000 keV) in this time interval is (1.8 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.13 s in the 10-1000 keV band is 3 +/- 0.2 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/40833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38873] Swift GRB 250625A: Global MASTER-Net observations report
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40832 SUBJECT: Swift GRB 250625A: Global MASTER-Net observations report DATE: 25/06/26 02:24:25 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) was pointed to the Swift GRB 250625A ( M. Ferro et al., GCN 40825) errorbox 16240 sec after notice time and 16278 sec after trigger time at 2025-06-25 20:36:14 UT, with upper limit up to 14.7 mag. The observations began at zenith distance = 22 deg. The sun altitude is -20.8 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the Swift GRB 250625A errorbox 35307 sec after notice time and 35345 sec after trigger time at 2025-06-26 01:54:01 UT, with upper limit up to 18.9 mag. The observations began at zenith distance = 60 deg. The sun altitude is -53.1 deg. The galactic latitude b = 28 deg., longitude l = 45 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2916460 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 16368 | MASTER-Tavrida | C | 180 | 14.7 | 35435 | MASTER-OAFA | C | 180 | 18.5 | 35630 | MASTER-OAFA | C | 180 | 18.2 | 35825 | MASTER-OAFA | C | 180 | 18.9 | 36026 | MASTER-OAFA | C | 180 | 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/40832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38872] GRB 250625A: NOT z-band upper limit
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40831 SUBJECT: GRB 250625A: NOT z-band upper limit DATE: 25/06/26 00:25:21 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. de Ugarte Postigo (LAM), G. Corcoran (UCD), B. P. Gompertz (Birmingham), D. Xu (NAOC), M. A. Diaz Teodori (NOT and Turku Univ.), report on behalf of a larger collaboration: We observed the position of the X-ray and optical afterglow (Beardmore et al., GCN 40827; Moskvitin & Spiridonova, GCN 40828) of GRB 250625A (Ferro et al., GCN 40825; Fermi GBM team, GCN 40824) using the Nordic Optical Telescope, using the “standby” StanCam instrument. In a sequence of 3 exposures of 200 s each, with mean time 2025 Jun 25.948 UT (6.67 hr after the trigger), we detect no object consistent with the X-ray afterglow, down to a limiting magnitude z > 21 AB, calibrated against the Pan-STARRS catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/40831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38871] GRB 250625A: SVOM/VT optical confirmation
by GCN Circulars 26 Jun '25

26 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40830 SUBJECT: GRB 250625A: SVOM/VT optical confirmation DATE: 25/06/26 00:20:46 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. L. Qiu, C. Wu, Y.N. Ma, Z. H. Yao, 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), J. Palmerio (CEA), A. Li (BNU) report on behalf of the SVOM/VT team SVOM/VT performed a Target of Opportunity observation of GRB 250625A detected by Swift-BAT（Ferro et al., GCN 40825) and Fermi-GBM (GCN #40824). The observation began at 2025-06-25T16:50:36 UTC, 45.7 minutes after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (Moskvitin et al., GCN 40828) within the errorbox of Swift/XRT (Beardmore et al., GCN 40827) was detected in the 38*70 sec stack image with a magnitude of VT_B=22.5+/-0.15 mag in AB magnitude with a mid time of 69 min after the burst. The counterpart is also detected in VT_R band in the stack image, but it has some contaimination from the blooming light from the nearby bright source. More detailed data analysis is on going. Our photometry was 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 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/40830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38870] GRB 250620B: Fermi GBM Observation
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40829 SUBJECT: GRB 250620B: Fermi GBM Observation DATE: 25/06/25 23:57:52 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:22:56.94 UT on 20 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB250620B (trigger 772118581/250620558). which was also detected by Swift/BAT-GUANO (S. Ronchini et al. 2025, GCN 40800). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 90 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 23 s (50-300 keV). The time-averaged spectrum from T0-2 to T0+23.6 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.3 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 430 +/- 236 keV. The event fluence (10-1000 keV) in this time interval is (2.7 +/- 0.4)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.7 s in the 10-1000 keV band is 1.9 +/- 0.2 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/40829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38869] GRB 250625A: SAO RAS possible optical afterglow
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40828 SUBJECT: GRB 250625A: SAO RAS possible optical afterglow DATE: 25/06/25 21:47:40 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova (SAO RAS), report on behalf of a GRB follow-up collaboration. We observed the field of the GRB 250625A (The Fermi GBM team, GCN 40824; Ferro et al., GCN 40825) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. We obtained 6 x 300 sec. exposures in Rc band on June 25, 20:39:03--21:12:11 UT (t_mid - T0 = 4.8447 hours). Withtin the enhanced XRT error circle (Beardmore et al., GCN 40827) we detect single object with the coordinates: R.A. (J2000.0) = 17:26:02.1 Dec. (J2000.0) = +22:16:03.6 +/- 0".3 and brightness of R = 22.97 +/- 0.17, possible GRB OT. Observations are ongoing to confirm variability of the object. Preliminary photometry is based on the nearby USNO-B1.0 and has not corrected for the Galactic extinction. R.A. Dec. (2000) R2 17:26:06.4 +22:16:29.4 14.75 17:26:03.7 +22:15:09.9 15.42 17:26:10.0 +22:13:56.8 15.03 17:26:01.4 +22:18:39.0 14.59 View this GCN Circular online at https://gcn.nasa.gov/circulars/40828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38868] GRB 250625A: Enhanced Swift-XRT position
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40827 SUBJECT: GRB 250625A: Enhanced Swift-XRT position DATE: 25/06/25 21:43:16 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> A.P. Beardmore, P.A. Evans, M.R. Goad and J.P. Osborne (U. Leicester) report on behalf of the Swift-XRT team. Using 2454 s of XRT Photon Counting mode data and 3 UVOT images for GRB 250625A, we find an astrometrically corrected X-ray position (using the XRT-UVOT alignment and matching UVOT field sources to the USNO-B1 catalogue): RA, Dec = 261.50887, +22.26729 which is equivalent to: RA (J2000): 17h 26m 2.13s Dec (J2000): +22d 16' 02.3" with an uncertainty of 2.3 arcsec (radius, 90% confidence). This position may be improved as more data are received. The latest position can be viewed at http://www.swift.ac.uk/xrt_positions. Position enhancement is described by Goad et al. (2007, A&A, 476, 1401) and Evans et al. (2009, MNRAS, 397, 1177). This circular was automatically generated, and is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38867] Fermi GRB 250625A: Global MASTER-Net observations report
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40826 SUBJECT: Fermi GRB 250625A: Global MASTER-Net observations report DATE: 25/06/25 21:15:24 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-Tavrida robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, SAI Crimea astronomical station) started inspect of the Fermi GRB 250625A ( Fermi GBM team, GCN 40824) errorbox 16256 sec after notice time and 16277 sec after trigger time at 2025-06-25 20:36:14 UT, with upper limit up to 14.7 mag. The observations began at zenith distance = 22 deg. The sun altitude is -20.8 deg. The galactic latitude b = 33 deg., longitude l = 49 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2916483 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 16367 | 2025-06-25 20:36:14 | MASTER-Tavrida | (17h 25m 02.21s , +22d 17m 15.8s) | C | 180 | 14.7 | 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/40826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38866] GRB 250625A: Swift detection of a burst
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40825 SUBJECT: GRB 250625A: Swift detection of a burst DATE: 25/06/25 16:20:37 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), D. M. Palmer (LANL), B. Sbarufatti (INAF-OAB) and M. H. Siegel (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 16:04:56 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250625A (trigger=1327910). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 261.519, +22.265 which is RA(J2000) = 17h 26m 04s Dec(J2000) = +22d 15' 55" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The BAT light curve showed a complex structure with a duration of about 8 sec. The peak count rate was ~2200 counts/sec (15-350 keV), at ~2 sec after the trigger. The XRT began observing the field at 16:06:56.2 UT, 119.8 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 261.50871, 22.26763 which is equivalent to: RA(J2000) = 17h 26m 02.09s Dec(J2000) = +22d 16' 03.5" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 35 arcseconds from the BAT onboard position, within the BAT error circle. This position may be improved as more data are received; the latest position is available at https://www.swift.ac.uk/sper. We cannot determine whether the source is fading at the present time. A power-law fit to a spectrum formed from promptly downlinked event data gives a column density in excess of the Galactic value (5.47 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 8 (+10.81/-7.26) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 124 seconds after the BAT trigger. No credible afterglow candidate has been found in the initial data products. The 2.7'x2.7' sub-image covers 100% of the XRT error circle. The typical 3-sigma upper limit has been about 19.6 mag. The 8'x8' region for the list of sources generated on-board covers 100% of the XRT error circle. The list of sources is typically complete to about 18 mag. No correction has been made for the expected extinction corresponding to E(B-V) of 0.055. This is co-detection with Fermi/GBM (GCN #40824). Burst Advocate for this burst is M. Ferro (matteo.ferro AT inaf.it). Please contact the BA by email if you require additional information regarding Swift followup of this burst. In extremely urgent cases, after trying the Burst Advocate, you can contact the Swift PI by phone (see Swift TOO web site for information: http://www.swift.psu.edu/) View this GCN Circular online at https://gcn.nasa.gov/circulars/40825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38865] GRB 250625A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40824 SUBJECT: GRB 250625A: Fermi GBM Final Real-time Localization DATE: 25/06/25 16:15:37 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 16:04:57 UT on 25 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250625A (trigger 772560302.510236 / 250625670). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 257.2, Dec = 27.0 (J2000 degrees, equivalent to J2000 17h 08m, 27d 00'), with a statistical uncertainty of 6.9 degrees. The angle from the Fermi LAT boresight is 28.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250625670/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38864] GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40823 SUBJECT: GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24 DATE: 25/06/25 15:10:36 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova (SAO RAS), N. Pankov (HSE, IKI), E. Klunko (ISTP), A. Pozanenko (IKI) report on behalf of GRB follow-up and IKI-GRB-FuN collaborations. We observed the field of the GRB 250617B (Page et al., GCN 40760; Fermi GBM team, GCN 40763; Bala and Meegan, GCN 40766; Osborne et al., GCN 40767; Williams et al., GCN 40773; Laha et al., GCN 40812) at the redshift of z = 1.396 (Corcoran et al., GCN 40776) with the 1.5-meter AZT-33IK telescope of Mondy observatory on 2025-06-23 and with the 1-m telescope Zeiss-1000 of the SAO RAS on 2025-06-24. The OT (Page et al., GCN 40760; Moskvitin et al., GCN 40761; Jelinek et al., GCN 40762; Grossan et al., GCN 40771; Ma et al., GCN 40772; Antier et al., GCN 40775; Corcoran et al., GCN 40776; Turpin et al., GCN 40777; Siegel and Page, GCN 40778; Pankov et al., GCN 40783; Gendreau-Distler et al., GCN 40789; Calapai, GCN 40804; also detected in NIR by Schneider et al., GCN 40774) is marginally detected in AZT-33IK stacked image and clearly detected in Zeiss-1000 stacked image. Preliminary results are as following. Date UT start t-T0 Exp. Filter OT Err. UL telescope (mid, days) (s) (3 sigma) 2025-06-23 16:37:49 5.84791 45*120 R 22.9 0.4 22.7 AZT-33IK 2025-06-24 22:44:03 7.09417 12*300 Rc 23.4 0.2 23.9 Zeiss-1000 This photometry is based on the USNO-B1.0 stars given in Moskvitin et. al, (GCN 40761) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38863] GRB 250620A: AstroSat CZTI detection
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40822 SUBJECT: GRB 250620A: AstroSat CZTI detection DATE: 25/06/25 11:52:12 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> M. Tembhurnikar (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of GRB 250620A which was also detected by Fermi/GBM (Fermi GBM Team, GCN Circ. 40791), Swift/BAT-GUANO (DeLaunay et al., GCN Circ. 40796), and SVOM/GRM (Wang et al., GCN Circ. 40806). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. We see only the initial short duration spike in the CZT detector data. The light curve peaks at 2025-06-20 08:05:18.89 UTC. The measured peak count rate associated with the burst is 853 (+613, -193) counts/s above the background in the combined data of three quadrants (out of four), with a total of 45 (+31, -13) counts. The local mean background count rate was 118 (+14, -102) counts/s. Using cumulative rates, we measure a T90 of 0.11 (+0.03, -0.03) s for the first spike. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. We see both episodes in Veto detectors, separated by about 10 s. The light curve, showing two burst episodes, peaks at 2025-06-20 08:05:27.70 UTC. The measured peak count rate associated with the burst is 368 (+65, -69) counts/s above the background in the combined data of all quadrants, with a total of 821 (+368, -375) counts. The local mean background count rate was 1184 (+7, -8) counts/s. We measure a T90 of 12 (+2, -10) s from the cumulative Veto light curve. The large negative uncertainty arises from the relatively weak detection of the first spike. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38862] The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40821 SUBJECT: The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580 DATE: 25/06/25 11:27:58 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO), W. X. Wang (NAO, CAS), J. H. Wu (GZHU), W. F. Wen(SZTU), W. D. Zhang(NAO, CAS), report on behalf of the Einstein Probe team: The EP-WXT trigger 01709179396 at the time of 2025-06-25T09:21:20, is likely a stellar flare associated with CSTAR 38580. The estimated flux of the flare is around 8 x 10^-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 3.2 x 10^31 erg/s. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40821. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38861] GRB 241018A: Maidanak optical observations
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40820 SUBJECT: GRB 241018A: Maidanak optical observations DATE: 25/06/25 10:30:21 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A. Volnova (IKI), A. Pozanenko (IKI), N. Pankov (HSE,IKI), O. Burhonov (UBAI), Sh. Ehgamberdiev (UBAI) report on behalf of GRB IKI FuN: We observed the field of GRB 241018A (SVOM team, GCN 37812) with AZT-22 1.5m telescope of Maidanak observatory in R-filter on 2024-10-18 (UT) 20:12:00 and in I-filter on 2024-10-19 (UT) 19:07:59 under very good weather conditions (seeing ~1"). The afterglow (SVOM/VT: GCN 37819; Swift XRT: Osborne et al., GCN 37823, Optical NOT: Malesani et al. GCN 37821; SVOM/VT commissioning team, GCN 37826; SVOM/C-GFT team, GCN 37841) is marginally detected in stacked images of 1 hour total exposure each. Preliminary photometry of the source is the following: Date UT start t-T0 Exp. Filter OT Err. UL(3 sigma) (mid, days) (s) 2024-10-18 20:12:00 0.37616 60x60 R 22.2 0.3 22.3 2024-10-19 19:07:59 1.33287 61x60 I 22.4 0.3 22.4 The photometry is based on nearby USNO-B1.0 stars: USNO-B_id RA Dec R2 I 1330-00124435 04:32:02.23 +43:02:33.2 17.00 16.39 1330-00124413 04:32:00.31 +43:01:30.1 16.80 15.94 1330-00124450 04:32:03.82 +43:01:22.9 16.55 16.24 The result is consistent with previously reported optical non-detection (Turpin et al., GCN 37818; Ferro et al., GCN 37822; Song et al., GCN 37824; Mohan et al., GCN 37825; Pankov et al., GCN 37827; Fernandez-Garcia et al., GCN 37828; Liu et al., GCN 37830; Ror et al., GCN 37837). View this GCN Circular online at https://gcn.nasa.gov/circulars/40820. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38860] GRB 250620C: AstroSat CZTI detection
by GCN Circulars 25 Jun '25

25 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40819 SUBJECT: GRB 250620C: AstroSat CZTI detection DATE: 25/06/25 07:20:43 GMT FROM: Gaurav Waratkar at IIT Bombay <gauravwaratkar(a)iitb.ac.in> S.Salunke (IUCAA), G. Waratkar (IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long and bright GRB 250620C which was also detected by Fermi/GBM (Fermi GBM team, GCN Circ. 40794), SVOM/GRM (Chen-Wei Wang et al, GCN Circ. 40807), and Konus-Wind (Svinkin et al, GCN Circ. 40810). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-06-20 16:07:11.50 UTC. The measured peak count rate associated with the burst is 1004 (+55, -46) counts/s above the background in the combined data of two quadrants (out of four), with a total of 8579 (+269, -224) counts. The local mean background count rate was 150 (+2, -3) counts/s. Using cumulative rates, we measure a T90 of 31.3 (+0.3, -0.4) s. In the preliminary analysis, we find 1018 Compton events associated with this event. The source was also clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2025-06-20 16:07:10.63 UTC. The measured peak count rate associated with the burst is 4717 (+120, -137) counts/s above the background in the combined data of all quadrants, with a total of 17904 (+519, -667) counts. The local mean background count rate was 1222 (+6, -5) counts/s. We measure a T90 of 31 (+1, -2) s from the cumulative Veto light curve. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/40819. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38859] Fermi GRB 250624A: Global MASTER-Net observations report
by GCN Circulars 24 Jun '25

24 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40818 SUBJECT: Fermi GRB 250624A: Global MASTER-Net observations report DATE: 25/06/24 20:30:25 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB 250624A ( Fermi GBM team, GCN 40817) errorbox 542 sec after notice time and 573 sec after trigger time at 2025-06-24 19:45:55 UT, with upper limit up to 14.4 mag. Observations started at twilight. The observations began at zenith distance = 57 deg. The sun altitude is -8.0 deg. The galactic latitude b = -46 deg., longitude l = 121 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2915767 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 574 | 2025-06-24 19:45:55 | MASTER-Tunka | (00h 36m 20.26s , +16d 05m 54.9s) | C | 1 | 14.4 | 584 | 2025-06-24 19:46:05 | MASTER-Tunka | (00h 36m 20.23s , +16d 05m 54.7s) | C | 1 | 14.4 | 590 | 2025-06-24 19:46:10 | MASTER-Tunka | (00h 36m 20.23s , +16d 05m 54.6s) | C | 1 | 14.4 | 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/40818. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38858] GRB 250624A: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Jun '25

24 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40817 SUBJECT: GRB 250624A: Fermi GBM Final Real-time Localization DATE: 25/06/24 19:46:55 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 19:36:21 UT on 24 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250624A (trigger 772486586.849764 / 250624817). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 10.6, Dec = 16.6 (J2000 degrees, equivalent to J2000 00h 42m, 16d 36'), with a statistical uncertainty of 5.3 degrees. The angle from the Fermi LAT boresight is 56.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250624817/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250624817/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250624817/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40817. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38857] sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis
by GCN Circulars 24 Jun '25

24 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40816 SUBJECT: sb25061207/GRB 250612D - SVOM/ECLAIRs refined analysis DATE: 25/06/24 11:04:07 GMT FROM: ogodet(a)irap.omp.eu Authors: O. Godet (IRAP), N. Dagoneau (CEA), F. Cangemi (APC), M. Brunet (IRAP), L. Zhang (IHEP), Y.-D. Hu (GXU), X.-L. Chen (YNU) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of the event sb25061207 that we confirm to be a GRB (GRB 250612D) based on the detection of a fading afterglow in both visible (GCN #40707) and X-rays (GCN #40718). The burst that triggered ECLAIRs onboard (GCN #40697) displays a faint and soft emission with most photons emitted below 20 keV. The duration of this event is around 32 s in the 4-20 keV energy band. The time-averaged spectrum from T0-32s to T0 (T0 = 2025-06-12T10:27:22 UTC) in the energy range 5-20 keV is best fitted by a powerlaw model with a photon index = 1.7 +/-0.3. With this model, the total 4-120 keV fluence is (7.4 +0.3/-4.2)e-7 erg/cm^2. All the quoted errors are at the 68% confidence level. We note that the calibration of SVOM/ECLAIRs is undergoing thus these results are preliminary. 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. The SVOM/ECLAIRs point of contact for this burst is: Olivier Godet (IRAP) (ogodet at irap.omp.eu) View this GCN Circular online at https://gcn.nasa.gov/circulars/40816. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38856] Fermi GRB 250623A: Global MASTER-Net observations report
by GCN Circulars 23 Jun '25

23 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40815 SUBJECT: Fermi GRB 250623A: Global MASTER-Net observations report DATE: 25/06/23 20:15:30 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 GRB 250623A ( Fermi GBM team, GCN 40814) errorbox 12254 sec after notice time and 12285 sec after trigger time at 2025-06-23 19:35:57 UT, with upper limit up to 19.6 mag. The observations began at zenith distance = 26 deg. The sun altitude is -48.5 deg. The galactic latitude b = 38 deg., longitude l = 359 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2914124 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 12315 | 2025-06-23 19:35:57 | MASTER-SAAO | (15h 27m 52.76s , -06d 33m 00.0s) | C | 60 | 19.2 | 12315 | 2025-06-23 19:35:57 | MASTER-SAAO | (15h 26m 04.67s , -06d 17m 23.3s) | C | 60 | 19.2 | 12408 | 2025-06-23 19:37:30 | MASTER-SAAO | (15h 35m 45.45s , -06d 34m 17.7s) | C | 60 | 19.2 | 12408 | 2025-06-23 19:37:30 | MASTER-SAAO | (15h 33m 57.55s , -06d 18m 40.9s) | C | 60 | 19.3 | 12502 | 2025-06-23 19:39:03 | MASTER-SAAO | (15h 23m 10.48s , -04d 22m 29.2s) | C | 60 | 19.5 | 12595 | 2025-06-23 19:40:36 | MASTER-SAAO | (15h 32m 55.26s , -04d 39m 53.0s) | C | 60 | 19.3 | 12595 | 2025-06-23 19:40:36 | MASTER-SAAO | (15h 31m 07.96s , -04d 24m 16.4s) | C | 60 | 19.3 | 12689 | 2025-06-23 19:42:11 | MASTER-SAAO | (15h 31m 46.60s , -08d 26m 56.3s) | C | 60 | 19.5 | 12689 | 2025-06-23 19:42:11 | MASTER-SAAO | (15h 29m 58.43s , -08d 11m 19.1s) | C | 60 | 19.5 | 12783 | 2025-06-23 19:43:44 | MASTER-SAAO | (15h 39m 47.59s , -08d 26m 17.1s) | C | 60 | 19.3 | 12783 | 2025-06-23 19:43:44 | MASTER-SAAO | (15h 37m 59.47s , -08d 10m 39.5s) | C | 60 | 19.4 | 12876 | 2025-06-23 19:45:18 | MASTER-SAAO | (15h 40m 02.82s , -04d 40m 16.4s) | C | 60 | 19.4 | 12876 | 2025-06-23 19:45:18 | MASTER-SAAO | (15h 38m 15.65s , -04d 24m 39.4s) | C | 60 | 19.5 | 12969 | 2025-06-23 19:46:51 | MASTER-SAAO | (15h 48m 06.97s , -04d 40m 30.1s) | C | 60 | 19.3 | 12969 | 2025-06-23 19:46:51 | MASTER-SAAO | (15h 46m 19.81s , -04d 24m 52.8s) | C | 60 | 19.4 | 13062 | 2025-06-23 19:48:24 | MASTER-SAAO | (15h 27m 56.33s , -06d 31m 53.7s) | C | 60 | 19.3 | 13062 | 2025-06-23 19:48:24 | MASTER-SAAO | (15h 26m 08.67s , -06d 16m 16.9s) | C | 60 | 19.4 | 13156 | 2025-06-23 19:49:57 | MASTER-SAAO | (15h 35m 55.61s , -06d 33m 31.4s) | C | 60 | 19.3 | 13156 | 2025-06-23 19:49:57 | MASTER-SAAO | (15h 34m 07.99s , -06d 17m 54.2s) | C | 60 | 19.4 | 13249 | 2025-06-23 19:51:30 | MASTER-SAAO | (15h 25m 07.12s , -04d 37m 46.5s) | C | 60 | 19.3 | 13249 | 2025-06-23 19:51:30 | MASTER-SAAO | (15h 23m 19.89s , -04d 22m 09.6s) | C | 60 | 19.6 | 13342 | 2025-06-23 19:53:04 | MASTER-SAAO | (15h 33m 00.14s , -04d 38m 44.7s) | C | 60 | 19.3 | 13342 | 2025-06-23 19:53:04 | MASTER-SAAO | (15h 31m 12.86s , -04d 23m 07.5s) | C | 60 | 19.4 | 13435 | 2025-06-23 19:54:37 | MASTER-SAAO | (15h 31m 52.38s , -08d 25m 39.2s) | C | 60 | 19.4 | 13435 | 2025-06-23 19:54:37 | MASTER-SAAO | (15h 30m 04.09s , -08d 10m 01.9s) | C | 60 | 19.5 | 13528 | 2025-06-23 19:56:10 | MASTER-SAAO | (15h 40m 00.69s , -08d 27m 01.6s) | C | 60 | 19.3 | 13528 | 2025-06-23 19:56:10 | MASTER-SAAO | (15h 38m 12.35s , -08d 11m 24.2s) | C | 60 | 19.5 | 13621 | 2025-06-23 19:57:43 | MASTER-SAAO | (15h 40m 11.81s , -04d 40m 00.8s) | C | 60 | 19.3 | 13621 | 2025-06-23 19:57:43 | MASTER-SAAO | (15h 38m 24.33s , -04d 24m 24.1s) | C | 60 | 19.6 | 13714 | 2025-06-23 19:59:16 | MASTER-SAAO | (15h 48m 14.27s , -04d 40m 05.3s) | C | 60 | 19.4 | 13714 | 2025-06-23 19:59:16 | MASTER-SAAO | (15h 46m 26.76s , -04d 24m 28.5s) | C | 60 | 19.5 | 13808 | 2025-06-23 20:00:49 | MASTER-SAAO | (15h 28m 03.37s , -06d 31m 40.0s) | C | 60 | 19.4 | 13808 | 2025-06-23 20:00:49 | MASTER-SAAO | (15h 26m 15.29s , -06d 16m 03.5s) | C | 60 | 19.6 | 13906 | 2025-06-23 20:02:28 | MASTER-SAAO | (15h 36m 02.97s , -06d 33m 23.3s) | C | 60 | 19.4 | 13906 | 2025-06-23 20:02:28 | MASTER-SAAO | (15h 34m 14.81s , -06d 17m 46.2s) | C | 60 | 19.5 | 13999 | 2025-06-23 20:04:01 | MASTER-SAAO | (15h 25m 14.02s , -04d 37m 33.0s) | C | 60 | 19.5 | 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/40815. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38855] GRB 250623A: Fermi GBM Final Real-time Localization
by GCN Circulars 23 Jun '25

23 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40814 SUBJECT: GRB 250623A: Fermi GBM Final Real-time Localization DATE: 25/06/23 16:21:45 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 16:11:12 UT on 23 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250623A (trigger 772387877.080294 / 250623674). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 233.4, Dec = -6.0 (J2000 degrees, equivalent to J2000 15h 33m, -6d 00'), with a statistical uncertainty of 10.2 degrees. The angle from the Fermi LAT boresight is 68.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250623674/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250623674/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250623674/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40814. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38854] GRB 250521A: VZLUSAT-2 detection
by GCN Circulars 23 Jun '25

23 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40813 SUBJECT: GRB 250521A: VZLUSAT-2 detection DATE: 25/06/23 15:09:37 GMT FROM: Marianna Dafčíková at Masaryk University <500025(a)mail.muni.cz> M. Dafcikova, J. Ripa (Masaryk U.), A. Pal (Konkoly Observatory), N. Werner (Masaryk U.), M. Ohno (Hiroshima U.), L. Meszaros, B. Csak (Konkoly Observatory), H. Takahashi (Hiroshima U.), F. Munz , M. Topinka, F. Hroch, N. Husarikova, J.-P. Breuer (Masaryk U.), J. Hudec, J. Kapus, M. Frajt, M. Rezenov (Spacemanic s.r.o), R. Laszlo (Needronix), G. Galgoczi (Wigner Research Center/Eotvos U.), N. Uchida (ISAS/JAXA), T. Enoto (Kyoto U.), Zs. Frei (Eotvos U.), Y. Fukazawa, K. Hirose, H. Matake (Hiroshima U.), S. Hisadomi (Nagoya U.), Y. Ichinohe (Rikkyo U.), L. L. Kiss (Konkoly Observatory), T. Mizuno (Hiroshima U.), K. Nakazawa (Nagoya U.), H. Odaka (Univ of Tokyo), K. Torigoe (Hiroshima U.), P. Svoboda, V. Daniel, J. Dudas, M. Junas, J. Gromes (VZLU), I. Vertat (FEL ZCU) -- the VZLUSAT-2/GRB payload collaboration. The long-duration GRB 250521A (Fermi/GBM detection: GCN 40508; GRBAlpha detection: GCN 40541; Wind/Konus detection trigger at 2025-05-21 04:27:04.888 UTC) was detected by the GRB detectors on board of the VZLUSAT-2 3U CubeSat (https://www.vzlusat2.cz/en/). The data acquisition was performed by the GRB detector units no. 0 and no. 1. The detection was confirmed at the peak time 2025-05-21 04:27:09 (04:27:02) UTC. The T90 duration is 33 s (35 s) and the significance during T90 reaches 10 sigma (15 sigma) for detector unit no. 0 (no. 1). The light curve obtained by VZLUSAT-2 is available here: https://vzlusat2.konkoly.hu/static/share/GRB250521A_GCN_VZLUSAT2.pdf All VZLUSAT-2 detections are listed at: https://monoceros.physics.muni.cz/hea/VZLUSAT-2/ The GRB detectors on VZLUSAT-2 are a demonstration payload for a future CubeSat constellation (Werner et al. Proc. SPIE 2018). Two GRB modules of VZLUSAT-2 are placed in a perpendicular manner and each consists of a 75 x 75 x 5 mm3 CsI scintillator read out by a SiPM array, covering the energy range from ~30 keV to ~1000 keV. VZLUSAT-2 was launched on 2022 January 13 from Cape Canaveral. View this GCN Circular online at https://gcn.nasa.gov/circulars/40813. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38853] GRB 250617B: Swift-BAT refined analysis
by GCN Circulars 23 Jun '25

23 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40812 SUBJECT: GRB 250617B: Swift-BAT refined analysis DATE: 25/06/23 11:39:14 GMT FROM: Takanori Sakamoto at AGU <tsakamoto(a)phys.aoyama.ac.jp> S. Laha (GSFC/UMBC), S. D. Barthelmy (GSFC), R. Gupta (GSFC), H. A. Krimm (NSF), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), K. L. Page (U Leicester), 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-273 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250617B (trigger #1325580) (Page, et al., GCN Circ. 40760). The BAT ground-calculated position is RA, Dec = 332.883, 32.721 deg which is RA(J2000) = 22h 11m 31.8s Dec(J2000) = +32d 43' 14.5" with an uncertainty of 1.9 arcmin, (radius, sys+stat, 90% containment). The partial coding was 10%. The mask-weighted light curve shows two peaks. The emission starts at T-30 sec, peaks at T+1 sec, and ends at T+18 sec. T90 (15-350 keV) is 36.5 +- 6.9 sec (estimated error including systematics). The time-averaged spectrum from T-29.32 to T+14.30 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.13 +- 0.22. The fluence in the 15-150 keV band is 2.3 +- 0.3 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+0.19 sec in the 15-150 keV band is 2.9 +- 0.8 ph/cm2/sec. 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/1325580 View this GCN Circular online at https://gcn.nasa.gov/circulars/40812. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38852] Fermi trigger No 772190032: Global MASTER-Net observations report
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40811 SUBJECT: Fermi trigger No 772190032: Global MASTER-Net observations report DATE: 25/06/22 17:45:33 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 GRB250621.38 (trigger No 772190032,18h 06m 48.00s , -20d 49m 58.8s, R=13.3) errorbox 41094 sec after notice time and 41126 sec after trigger time at 2025-06-21 20:39:13 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 17 deg. The sun altitude is -62.0 deg. The galactic latitude b = -1 deg., longitude l = 10 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2911222 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 41157 | 2025-06-21 20:39:13 | MASTER-SAAO | (17h 03m 51.42s , -21d 48m 23.9s) | C | 60 | 18.5 | 41250 | 2025-06-21 20:40:46 | MASTER-SAAO | (17h 12m 24.87s , -21d 47m 48.3s) | C | 60 | 18.4 | 43099 | 2025-06-21 21:11:35 | MASTER-SAAO | (17h 04m 13.21s , -21d 48m 47.1s) | C | 60 | 18.5 | 43192 | 2025-06-21 21:13:08 | MASTER-SAAO | (17h 12m 43.81s , -21d 47m 46.4s) | C | 60 | 18.3 | 45253 | 2025-06-21 21:47:29 | MASTER-SAAO | (17h 04m 32.28s , -21d 47m 18.3s) | C | 60 | 18.5 | 45348 | 2025-06-21 21:49:05 | MASTER-SAAO | (17h 12m 59.51s , -21d 48m 45.5s) | C | 60 | 18.3 | 46601 | 2025-06-21 22:09:58 | MASTER-SAAO | (17h 04m 34.91s , -21d 46m 48.7s) | C | 60 | 18.5 | 46694 | 2025-06-21 22:11:31 | MASTER-SAAO | (17h 13m 09.50s , -21d 46m 18.7s) | C | 60 | 18.3 | 47940 | 2025-06-21 22:32:16 | MASTER-SAAO | (17h 04m 45.05s , -21d 47m 05.2s) | C | 60 | 18.5 | 48033 | 2025-06-21 22:33:50 | MASTER-SAAO | (17h 13m 21.76s , -21d 46m 08.2s) | C | 60 | 18.4 | 50042 | 2025-06-21 23:07:19 | MASTER-SAAO | (17h 04m 55.78s , -21d 46m 23.4s) | C | 60 | 18.6 | 50136 | 2025-06-21 23:08:52 | MASTER-SAAO | (17h 13m 27.52s , -21d 45m 19.7s) | C | 60 | 18.3 | 115062 | 2025-06-22 17:10:59 | MASTER-SAAO | (18h 11m 33.03s , -24d 48m 18.7s) | C | 60 | 17.0 | 115278 | 2025-06-22 17:14:34 | MASTER-SAAO | (18h 11m 29.34s , -24d 47m 56.5s) | C | 60 | 16.9 | 115928 | 2025-06-22 17:25:25 | MASTER-SAAO | (18h 11m 32.62s , -24d 47m 32.4s) | C | 60 | 16.8 | 116140 | 2025-06-22 17:28:57 | MASTER-SAAO | (18h 11m 32.10s , -24d 48m 31.6s) | C | 60 | 16.9 | 116348 | 2025-06-22 17:32:25 | MASTER-SAAO | (18h 11m 28.31s , -24d 48m 25.1s) | C | 60 | 16.9 | 116555 | 2025-06-22 17:35:52 | MASTER-SAAO | (18h 11m 24.50s , -24d 47m 38.3s) | C | 60 | 16.8 | 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/40811. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38851] Konus-Wind detection of GRB 250620C
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40810 SUBJECT: Konus-Wind detection of GRB 250620C DATE: 25/06/22 10:03:09 GMT FROM: Dmitry Svinkin at Ioffe Institute <dmitrysvinkin(a)gmail.com> D. Svinkin, D. Frederiks, A. Lysenko, A. Ridnaia, A. Tsvetkova, M. Ulanov, and T. Cline on behalf of the Konus-Wind team, report: The bright,long-duration GRB 250620C (Fermi-GBM detection: The Fermi GBM team, GCN 40794; Mukherjee, GCN 40799; SVOM-GRM detection: Wang et al., GCN 40807; IPN triangulation: Svinkin et al., GCN 40809) triggered Konus-Wind at T0=58026.172 s UT (16:07:06.172). The burst light curve shows a multipeaked structure which starts at ~T0-0.2 s and has a total duration of ~39 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB250620_T58026/ As observed by Konus-Wind, the burst had a fluence of 7.87(-0.47,+0.43)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+1.344 s, of 4.05(-0.28,+0.28)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+39.424 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -1.00(-0.03,+0.03), the high energy photon index beta = -2.83(-0.42,+0.21), the peak energy Ep = 363(-17,+19) keV (chi2 = 116/97 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+1.536 s) is best fit in the 20 keV - 15 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.71(-0.05,+0.05), the high energy photon index beta = -2.44(-0.14,+0.12), the peak energy Ep = 618(-45,+47) keV (chi2 = 85/59 dof). 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/40810. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38850] IPN triangulation of GRB 250620С (long/bright)
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40809 SUBJECT: IPN triangulation of GRB 250620С (long/bright) DATE: 25/06/22 09:58:12 GMT FROM: Dmitry Svinkin at Ioffe Institute <dmitrysvinkin(a)gmail.com> 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, and S. Barthelmy, J. Cummings, H. Krimm, D. Palmer, A. Tohuvavohu, and J. DeLaunay on behalf of the Swift-BAT team, report: The bright long-duration GRB 250620C (Fermi-GBM detection: The Fermi GBM team, GCN 40794; Mukherjee, GCN 40799; SVOM-GRM detection: Wang et al., GCN 40807) was detected by Fermi (GBM trigger 772128434), Swift (BAT), Konus-Wind, and SVOM (GRM) at about 58030 s UT (16:07:10). The burst was outside the coded field of view of the BAT. We have triangulated it to a preliminary, 3 sigma error box whose area is 17.6 sq. deg, and its maximum dimension is 25.5 deg (the minimum one is 51.0 arcmin). The Sun distance was ~50 deg. This localization may be improved. The IPN localization is consistent with, but reduces the area of, the Fermi-GBM (GCN 40794) and BALROG (https://grb.mpe.mpg.de/grb/GRB250620672/?data_version=tte_v00) localizations. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB250620_T58026/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/40809. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38849] GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40808 SUBJECT: GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst DATE: 25/06/22 06:07:38 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Piron (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a short burst GRB 250621B (SVOM trigger reference: sb25062104) at 2025-06-21T09:13:47.100 UTC (T0), which is also detected by Fermi/GBM (TrigNum 772190032). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 0.11 +0.02/-0.03 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250621B.png The SVOM/GRM on-ground localization of this burst is (J2000): RA: 273.9 deg DEC: -24.8 deg Error: 2.9 deg (1sigma, statistical only) We caution that the calibration of SVOM/GRM is undergoing and this localization is subject to systematic errors. In addition, the position of this burst, as determined by GRM, is located at about 8 degrees from the SVOM optical axis, but ECLAIRs was not collecting data at the time of this burst. With this localization, the time-averaged spectrum from T0-0.3 to T0+0.2 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.05 +0.25/-0.27 and the cutoff energy, parameterized as Epeak, is 31 +/- 3 keV. The event fluence (10-1000 keV) in this time interval is (3.79 +/-0.15)E-07 erg/cm^2. We note that the localization of this burst is relatively close to the Galactic disk and compatible with the position of SGR 1806-20, as well as the hardness and duration all suggest a magnetar X-ray 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40808. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38848] GRB 250620C: SVOM/GRM observation
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40807 SUBJECT: GRB 250620C: SVOM/GRM observation DATE: 25/06/22 05:55:58 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a bright burst GRB 250620C (SVOM trigger reference: sb25062006) at 2025-06-20T16:07:10.100 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40794). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 30.1 +/-1.5 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250620C.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 142.6, DEC= 55.0, GCN#40794), is located at about 161 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-1 to T0+40 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.22 +0.13/-0.12 and the cutoff energy, parameterized as Epeak, is 502 +74/-55 keV. The event fluence (10-1000 keV) in this time interval is (9.15 +0.26/-0.28)E-07 erg/cm^2. The localization of GRB 250620C in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/grb250620C_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40807. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38847] GRB 250620A: SVOM/GRM observation of a short burst
by GCN Circulars 22 Jun '25

22 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40806 SUBJECT: GRB 250620A: SVOM/GRM observation of a short burst DATE: 25/06/22 05:55:18 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Ulysse Jacob (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a bright burst GRB 250620A (SVOM trigger reference: sb25062002) at 2025-06-20T08:05:19 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN#40791) and Swift/BAT (James DeLaunay et al., GCN#40796). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 0.15 +/-0.05 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb250620A.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 46.2, DEC= 65.8, GCN#40791), is located at about 111 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-0.2 to T0 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.64 +0.25/-0.19 and the cutoff energy, parameterized as Epeak, is 1310 +1780/-780 keV. The event fluence (10-1000 keV) in this time interval is (8.36 +0.89/-0.87)E-07 erg/cm^2. The localization of GRB 250620A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/grb250620A_amati.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/40806. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38846] GRB250620A: Fermi GBM Observation
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40805 SUBJECT: GRB250620A: Fermi GBM Observation DATE: 25/06/21 23:52:54 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 08:05:18.94 UT on 20 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250620A (trigger 772099523/250620337) which was also detected by Swift/BAT-GUANO (DeLaunay et al. 2025, GCN 40796). The angle from the Fermi LAT boresight is 164 degrees. The GBM light curve two pulses with a duration (T90) of about 12 s (50-300 keV). The time-averaged spectrum from T0-0.3 to T0+10 s is best fit by a simple power law function with index -1.6 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (1.1 +/- 1.3)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.8 s in the 10-1000 keV band is 9 +/- 2 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak = 2000 +/- 200 keV, alpha = -1.08 +/- 0.03 and beta = -2.44 +/- 0.09. 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/40805. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38845] GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40804 SUBJECT: GRB 250617B: Calapai Observatory, Massa S. Giorgio (Messina), optical observation. DATE: 25/06/21 21:08:57 GMT FROM: Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, Messina, Italy <giovannicalapai(a)tiscali.it> Giovanni Calapai at Calapai Astronomical Observatory, Massa S. Giorgio, (Messina) Italy Member of: GRB/UAI Gamma Ray Burst Section of Unione Astrofili Italiani. Report: We observed the field of GRB 250617B detected by Swift/BAT (Page et al. GCN 40760) with the 11 inches Schmidt-Cassegrain (Celestron 11) telescope F/D=6,3. The observations were started at 2025-06-17 23:10:55 UT (approximately 2.15 hours after burst) stacking a two consecutive sets of unfiltered CCD image. The observations were carried out with visibility disturbed by passing clouds. The OT was detected at the following position: RA (J2000.0) 22h 11m 35.21s +/- 0.02 Decl. (J2000.0) +32° 43' 57.6" +/- 1.1 The results of our photometry are: Observation Mid-Time T-T0 (hr) Exposure Filter Mag. S/N Mag. err. 2025-06-18 00:05:21 UT 3.06 90x60s CR 19.24 9.1 +/-0.17 2025-06-18 01:47:28 UT 4.76 88x60s CR 20.75 3.4 +/-0.30 Given the low S/N for the OT of second set, we cannot completely rule out it being due to background fluctuation. Along the span of our observations and within our uncertainties, the afterglow evolves in agreement with a power-law decay index of ~0.89. Magnitude was calibrated with the nearby PanSTARRS stars converted using Lupton (2005) equations. No correction for galactic dust extinction was applied. Our observations are consistent with other already reported Moskvitin et al. (GCN 40761); Jelinek et al. (GCN 40762); Kumar et al. (GCN 40768); Lipunov et al. (GCN 40769); Grossan et al. (GCN 40771); Ma et al. (GCN 40772); Williams et al. (GCN 40773); Schneider et al. (GCN 40774); Antier et al. (GCN 40775); Corcoran et al. (GCN 40776); Turpin et al. (GCN 40777); Siegel et al. (GCN 40778); Pankov et al. (GCN 40783); Gendreau-Distler et al. (GCN 40789). The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/40804. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38844] Fermi GRB 250621A: Global MASTER-Net observations report
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40803 SUBJECT: Fermi GRB 250621A: Global MASTER-Net observations report DATE: 25/06/21 02:30:51 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-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) started inspect of the Fermi GRB 250621A ( Fermi GBM team, GCN 40801) errorbox 79 sec after notice time and 111 sec after trigger time at 2025-06-21 01:16:46 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 77 deg. The sun altitude is -45.4 deg. The galactic latitude b = 10 deg., longitude l = 248 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2910652 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 122 | 2025-06-21 01:16:46 | MASTER-OAFA | (08h 35m 57.13s , -26d 43m 55.5s) | C | 20 | 17.4 | 161 | 2025-06-21 01:17:21 | MASTER-OAFA | (08h 46m 34.40s , -23d 40m 16.6s) | C | 30 | 17.8 | 202 | 2025-06-21 01:17:57 | MASTER-OAFA | (08h 46m 34.42s , -23d 40m 16.3s) | C | 40 | 17.9 | 253 | 2025-06-21 01:18:43 | MASTER-OAFA | (08h 46m 34.45s , -23d 40m 16.4s) | C | 50 | 18.0 | 315 | 2025-06-21 01:19:40 | MASTER-OAFA | (08h 46m 34.42s , -23d 40m 15.2s) | C | 60 | 17.9 | 386 | 2025-06-21 01:20:46 | MASTER-OAFA | (08h 46m 34.44s , -23d 40m 15.4s) | C | 70 | 18.2 | 472 | 2025-06-21 01:22:02 | MASTER-OAFA | (08h 46m 34.52s , -23d 40m 15.8s) | C | 90 | 18.2 | 573 | 2025-06-21 01:23:38 | MASTER-OAFA | (08h 46m 34.55s , -23d 40m 15.7s) | C | 100 | 18.2 | 702 | 2025-06-21 01:25:32 | MASTER-OAFA | (08h 39m 15.15s , -24d 49m 47.5s) | C | 130 | 18.1 | 848 | 2025-06-21 01:27:48 | MASTER-OAFA | (08h 39m 15.35s , -24d 49m 48.3s) | C | 150 | 17.9 | 1019 | 2025-06-21 01:30:24 | MASTER-OAFA | (08h 39m 15.58s , -24d 49m 49.7s) | C | 180 | 17.8 | 1205 | 2025-06-21 01:33:30 | MASTER-OAFA | (08h 39m 15.88s , -24d 49m 51.5s) | C | 180 | 17.6 | 1392 | 2025-06-21 01:36:36 | MASTER-OAFA | (08h 39m 16.16s , -24d 49m 53.1s) | C | 180 | 17.5 | 1578 | 2025-06-21 01:39:42 | MASTER-OAFA | (08h 39m 16.38s , -24d 49m 59.7s) | C | 180 | 17.2 | 1763 | 2025-06-21 01:42:48 | MASTER-OAFA | (08h 39m 16.61s , -24d 50m 07.5s) | C | 180 | 16.8 | 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/40803. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38843] GRB 250619B: Fermi GBM Observation
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40802 SUBJECT: GRB 250619B: Fermi GBM Observation DATE: 25/06/21 01:38:07 GMT FROM: Jacob Smith at Fermi-GBM Team <jrs0118(a)uah.edu> Jacob Smith (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: At 23:36:17.17 UT on 19 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250619B (trigger 772068982/250619984). which was also detected by Swift/BAT-GUANO (J. DeLaunay et al. 2025, GCN 40795). The Fermi GBM on-ground location is consistent with the Swift/BAT-GUANO position. The angle from the Fermi LAT boresight is 48 degrees. The GBM light curve consists of a double emission episode with a duration (T90) of about 29 s (50-300 keV). The time-averaged spectrum from T0-1 to T0+28.7 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.1 +/- 0.2 and the cutoff energy, parameterized as Epeak, is 67 +/- 9 keV. A Band function fits the spectrum equally well with Epeak = 57 +/- 13 keV, alpha = -1 +/- 0.4 and beta = -2.5 +/- 0.4. The event fluence (10-1000 keV) in this time interval is (1.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0-0.32 s in the 10-1000 keV band is 2.2 +/- 0.2 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/40802. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38842] GRB 250621A: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40801 SUBJECT: GRB 250621A: Fermi GBM Final Real-time Localization DATE: 25/06/21 01:25:28 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 01:14:55 UT on 21 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250621A (trigger 772161300.203902 / 250621052). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 129.7, Dec = -25.1 (J2000 degrees, equivalent to J2000 08h 38m, -25d 06'), with a statistical uncertainty of 1.9 degrees. The angle from the Fermi LAT boresight is 50.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250621052/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40801. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38841] GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 21 Jun '25

21 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40800 SUBJECT: GRB 250620B: Swift/BAT-GUANO localization skymap of a burst DATE: 25/06/21 00:30:05 GMT FROM: Samuele Ronchini at PSU <sjs8171(a)psu.edu> Samuele Ronchini (PSU), James DeLaunay (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (PSU) report: Swift/BAT did not localize GRB 250620B onboard (T0: 2025-06-20T13:22:56.94 UTC, Fermi/GBM GCN 40792) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 13.83 in a 4.096 s analysis time bin, starting at T0 - 1.024 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 8,562 deg2 and the 50% credible area is 2,685 deg2. The integrated probability inside the coded field of view is 8%. The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 40792). The combined Fermi/GBM+NITRATES 90% credible area is 158 deg2 and the 50% credible area is 51 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=772118612/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/772118612/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/772118612/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=772118612 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/40800. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38840] GRB250620C: Fermi GBM Observation
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40799 SUBJECT: GRB250620C: Fermi GBM Observation DATE: 25/06/20 23:48:00 GMT FROM: oindabimukherjee(a)gmail.com O. Mukherjee (USRA) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 16:07:09.92 UT on 20 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB250620C (trigger 772128434/250620672). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 142.61, Dec = 54.96 (J2000 degrees, equivalent to J2000 9h 30m, +54d 57'), with a statistical uncertainty of 1.00 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 124 degrees. The GBM light curve consists of multiple emission episodes with a duration (T90) of about 32 s (50-300 keV). The time-averaged spectrum from T0 to T0+35.7 s is best fit by a Band function with Epeak= 371 +/- 15 keV, alpha = -0.93 +/- 0.02 and beta = -2.6 +/- 0.2. The event fluence (10-1000 keV) in this time interval is (6.64 +/- 0.07)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+0.96 s in the 10-1000 keV band is 50.1 +/- 0.7 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/40799. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38839] GRB 260506A - SVOM/ECLAIRs Refined analysis
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40798 SUBJECT: GRB 260506A - SVOM/ECLAIRs Refined analysis DATE: 25/06/20 22:04:35 GMT FROM: sebastien.guillot(a)irap.omp.eu Authors: S. Guillot (IRAP), F. Cangemi, A. Coleiro (APC), M.-G. Bernardini (INAF-OAB, LUPM), O. Godet (IRAP), Chenwei WANG (IHEP), Lin LAN (NAOC) Using the event-by-event data downloaded through the X-band ground station, we report further analysis of ECLAIRs observations of GRB 250506A (SVOM burst-id sb25050601). The burst that triggered ECLAIRs onboard (GCN 40358) consists of a single pulse with a duration of T90 = 6.4 +1.0/-0.6 s in the 4-120 keV energy band. We note that ECLAIRs only saw the first peak of this GRB since the source passed behind the Earth during the burst. Therefore, this T90 value is only for the first peak, and is shorter than those measured by Fermi/GBM (GCN 40362) and GECAM (GCN 40396). The time-averaged spectrum of the burst from T0 + 4.12 sec to T0 + 12.12 sec (T0 = 2025-05-06T02:23:16.88) in the energy range 5-115 keV is best fit by a broken power-law model with a break energy of 14.2 +3.8/-1.9 keV, a photon index of -0.3 +/- 0.2 before the break, and of -0.97 +0.06/-0.08 after the break. The photon index after the break is broadly consistent with the PL index (50-300 keV) reported from the Fermi/GBM analysis (GCN 40362). With this model, the total 4-120 keV fluence, assuming the T90 measured, is 1.75 +0.28/-0.5 x 10^-6 erg/cm^2. All the quoted errors are at the 90% confidence level. Other models (power law, cutoff power law, blackbody + power law, gamma-ray burst continuum) do not satisfactorily fit the data. The comparison of the power-law and broken power-law fits yields a spectral break significance of 5.1 sigma (Gaussian two-sided). We note that the calibration of SVOM/ECLAIRs is undergoing thus these results are preliminary. 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. The SVOM/ECLAIRs point of contact for this burst is: Sébastien Guillot (IRAP) (sebastien.guillot at irap.omp.eu) View this GCN Circular online at https://gcn.nasa.gov/circulars/40798. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38838] The EP-WXT trigger 01709179071 is likely a flaring star
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40797 SUBJECT: The EP-WXT trigger 01709179071 is likely a flaring star DATE: 25/06/20 20:59:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> X. Mao, Y. J. Song, T. Zhao, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709179071 at the time of 2025-06-20T19:46:46, is likely a stellar flare associated with 2MASS J21370885-6036054. The estimated flux of the flare is around 1e-10 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.4e31 erg/s. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40797. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38837] GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40796 SUBJECT: GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst DATE: 25/06/20 19:50:54 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Rachel Hamburg (USRA), Oindabi Mukherjee (USRA), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (PSU), Gayathri Raman (PSU) report: Swift/BAT did not localize GRB 250620A onboard (T0: 2025-06-20T08:05:18.94 UTC, Fermi/GBM trig 772099523) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 7.3 in a 0.512 s analysis time bin, starting at T0 + 8.96 s. This corresponds to a FAR ~ 5e-4 Hz. This is ~9 s after the initial short spike detected by Fermi/GBM, but is temporally coincident with a separate pulse seen in the Fermi/GBM lightcurve. The initial short spike is also detected by NITRATES, but very weakly with a sqrt(TS) of 6.8 (FAR ~ 2e-3 Hz) in a 0.256 s analysis time bin, starting at T0 - 0.128 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 15,094 deg2 and the 50% credible area is 5,333 deg2. The integrated probability inside the coded field of view is 1%. The NITRATES skymap is very large but is consistent with the Fermi localization reported in the final position notice (GCN 40791). A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=772099554/#:~:te… The probability skymap file can be downloaded from the link here [skymap_fits_file](https://guano.swift.psu.edu/files/772099554/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/772099554/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=772099554 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/40796. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38836] GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40795 SUBJECT: GRB 250619B: Swift/BAT-GUANO localization skymap of a burst DATE: 25/06/20 17:11:42 GMT FROM: Jimmy DeLaunay at Penn State <delauj2(a)gmail.com> James DeLaunay (PSU), Samuele Ronchini (PSU), Aaron Tohuvavohu (Caltech), Jamie A. Kennea (PSU), Tyler Parsotan (NASA GSFC), Maia Williams (PSU) report: Swift/BAT did not localize GRB 250619B onboard (T0: 2025-06-19T23:36:17.17 UTC, Fermi/GBM trig 772068982) The Fermi notice, distributed in near real-time, triggered the Swift Mission Operations Center operated Gamma-ray Urgent Archiver for Novel Opportunities (GUANO; Tohuvavohu et al. 2020, ApJ, 900, 1). Upon trigger by this notice, GUANO sent a command to the Swift Burst Alert Telescope (BAT) to save 200 seconds of BAT event-mode data from [-50,+150] seconds around the time of the burst. All the requested event mode data was delivered to the ground. The BAT likelihood search, NITRATES (DeLaunay + Tohuvavohu 2022, ApJ, 941, 169), performed on the temporal window [T0-20 s, T0+20 s], detects the burst with a sqrt(TS) of 7.9 in a 8.192 s analysis time bin, starting at T0 - 2.048 s. Using the NITRATES analysis, parameter estimation was performed to obtain the localization of this burst in the form of a HEALPIX Multi-Order Coverage (MOC) skymap. This localization accounts for both statistical and systematic errors. More details in the creation and calibration of these maps will soon be published (DeLaunay et al. 2025. in prep) The 90% credible area is 10,760 deg2 and the 50% credible area is 1,197 deg2. The integrated probability inside the coded field of view is 30%. The NITRATES skymap is consistent with the Fermi localization reported in the final position notice (GCN 40788). The combined Fermi/GBM+NITRATES 90% credible area is 652 deg2 and the 50% credible area is 146 deg2. A plot of the probability skymap can be viewed here: [skymap_plot](https://guano.swift.psu.edu/trigger_report?id=772069012/#:~:te… The probability skymap and joint skymap files can be downloaded from the links here [skymap_fits_file](https://guano.swift.psu.edu/files/772069012/0_n_PROBMAP) [joint_skymap_fits_file](https://guano.swift.psu.edu/files/772069012/0_n_JOI… Instructions on how to read and manipulate this map can be found here: https://guano.swift.psu.edu/documentation More details about this burst can be found on the trigger report page here: https://guano.swift.psu.edu/trigger_report?id=772069012 GUANO is a fully autonomous, extremely low latency, spacecraft commanding pipeline designed for targeted recovery of BAT event mode data around the times of compelling astrophysical events to enable more sensitive GRB searches. A live reporting of Swift/BAT event data recovered by GUANO can be found at: https://www.swift.psu.edu/guano/ View this GCN Circular online at https://gcn.nasa.gov/circulars/40795. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38835] GRB 250620C: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40794 SUBJECT: GRB 250620C: Fermi GBM Final Real-time Localization DATE: 25/06/20 16:18:37 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 16:07:09 UT on 20 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250620C (trigger 772128434.916854 / 250620672). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 142.6, Dec = 55.0 (J2000 degrees, equivalent to J2000 09h 30m, 55d 00'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 124.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620672/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620672/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620672/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40794. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38834] Fermi trigger No 772128434: Global MASTER-Net observations report
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40793 SUBJECT: Fermi trigger No 772128434: Global MASTER-Net observations report DATE: 25/06/20 16:16:06 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-Tunka robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Applied Physics Institute, Irkutsk State University) started inspect of the Fermi GRB250620.67 (trigger No 772128434,09h 30m 26.40s , +54d 57m 36.0s, R=1) errorbox 96 sec after notice time and 133 sec after trigger time at 2025-06-20 16:09:23 UT, with upper limit up to 15.7 mag. Observations started at twilight. The observations began at zenith distance = 58 deg. The sun altitude is -14.4 deg. The galactic latitude b = 45 deg., longitude l = 161 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2910184 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 148 | 2025-06-20 16:09:23 | MASTER-Tunka | (09h 40m 06.83s , +56d 13m 43.0s) | P- | 30 | 14.9 | 148 | 2025-06-20 16:09:23 | MASTER- | (09h 21m 21.53s , +56d 18m 40.7s) | C | 30 | 14.5 | 250 | 2025-06-20 16:10:55 | MASTER-Tunka | (09h 40m 05.78s , +56d 08m 46.7s) | P- | 50 | 15.7 | 250 | 2025-06-20 16:10:55 | MASTER- | (09h 21m 23.28s , +56d 13m 19.9s) | C | 50 | 15.3 | 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/40793. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38833] GRB 250620B: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40792 SUBJECT: GRB 250620B: Fermi GBM Final Real-time Localization DATE: 25/06/20 13:33:28 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 13:22:56 UT on 20 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250620B (trigger 772118581.936592 / 250620558). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 67.1, Dec = -30.2 (J2000 degrees, equivalent to J2000 04h 28m, -30d 11'), with a statistical uncertainty of 6.0 degrees. The angle from the Fermi LAT boresight is 90.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620558/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620558/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620558/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40792. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38832] GRB 250620A: Fermi GBM Final Real-time Localization
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40791 SUBJECT: GRB 250620A: Fermi GBM Final Real-time Localization DATE: 25/06/20 08:15:50 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 SHORT GRB At 08:05:18 UT on 20 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250620A (trigger 772099523.9444 / 250620337). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 46.2, Dec = 65.8 (J2000 degrees, equivalent to J2000 03h 04m, 65d 47'), with a statistical uncertainty of 6.2 degrees. The angle from the Fermi LAT boresight is 164.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620337/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620337/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250620337/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40791. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38831] EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40790 SUBJECT: EP-WXT trigger 01709179036: a new outburst of GRS 1739-278 DATE: 25/06/20 05:30:21 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Sun (NAO, CAS), J. Yang (NJU), H. Z. Wu (HUST), X. L. Chen (YNU), W. D. Zhang (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a new X-ray outburst from the black hole low-mass X-ray binary GRS 1739-278, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The source exhibited a rapid rise in its 0.5-4 keV flux since June 15th, 2025 and triggered EP-WXT (ID: 01709179036) at 2025-06-19T14:54:11 (UTC, ATel #17238). A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP was performed automatically around 2 minutes after the trigger, with an exposure time of 1.2 ks. A bright X-ray source, whose position is consistent with GRS 1739-278, was detected by FXT, thus confirming the new outburst of GRS 1739-278. The FXT spectrum can be fitted by an absorbed power-law with a photon index of 2.1 (+/-0.1) and a neutral hydrogen column density of 2.3 (+/-0.1) x 10^22 cm^-2. The derived unabsorbed flux in 0.5-10 keV is 1.8 (+/-0.1) x 10^-9 erg/s/cm^2. Multi-wavelength follow-up observations are strongly encouraged. 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). View this GCN Circular online at https://gcn.nasa.gov/circulars/40790. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38830] GRB 250617B: Nickel telescope optical observations
by GCN Circulars 20 Jun '25

20 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40789 SUBJECT: GRB 250617B: Nickel telescope optical observations DATE: 25/06/20 00:49:40 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> Eli Gendreau-Distler, Gracelynn Jost, William Wu, WeiKang Zheng and Alex Filippenko (UC Berkeley) report on behalf of the KAIT GRB team: We observed the field of GRB 250617B (Page et. al, GCN 40760; The Fermi GBM team, GCN 40763) with the 1-m Nickel telescope located at Lick observatory, California. Observations were performed in R band with 600s x 5 exposure time started at 09:46 UT on June 18. We clearly detected the optical afterglow (Page et. al, GCN 40760, Moskvitin et. al, GCN 40761, Jelinek et. al, GCN 40762; Kumar et. al, GCN 40768; Lipunov et. al, GCN 40769; Grossan et. al, GCN 40771; Ma et. al, GCN 40772; Schneider et. al, GCN 40774; Antier et. al, GCN 40775; Corcoran et. al, GCN 40776; Turpin et. al, GCN 40777; Siegel & Page, GCN 40778; Pankov et al., GCN 40783) in our coadd image with 21.4 +/- 0.1 mag at a mid time of 13.10 hours after the burst. View this GCN Circular online at https://gcn.nasa.gov/circulars/40789. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38829] GRB 250619B: Fermi GBM Final Real-time Localization
by GCN Circulars 19 Jun '25

19 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40788 SUBJECT: GRB 250619B: Fermi GBM Final Real-time Localization DATE: 25/06/19 23:46:58 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 23:36:17 UT on 19 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250619B (trigger 772068982.168064 / 250619984). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 25.4, Dec = -24.8 (J2000 degrees, equivalent to J2000 01h 41m, -24d 48'), with a statistical uncertainty of 13.4 degrees. The angle from the Fermi LAT boresight is 48.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250619984/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250619984/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250619984/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40788. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38828] Fermi trigger No 772058337: Global MASTER-Net observations report
by GCN Circulars 19 Jun '25

19 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40787 SUBJECT: Fermi trigger No 772058337: Global MASTER-Net observations report DATE: 25/06/19 22:45:44 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB250619.86 (trigger No 772058337,03h 12m 26.40s , +44d 13m 48.0s, R=2.33) errorbox 4841 sec after notice time and 4865 sec after trigger time at 2025-06-19 21:59:58 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 80 deg. The sun altitude is -22.6 deg. The galactic latitude b = -11 deg., longitude l = 148 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2908907 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 4896 | 2025-06-19 21:59:58 | MASTER-Kislovodsk | (03h 06m 25.90s , +44d 50m 12.6s) | C | 60 | 17.2 | 5071 | 2025-06-19 22:02:53 | MASTER-Kislovodsk | (03h 12m 52.91s , +46d 45m 24.6s) | C | 60 | 17.2 | 5154 | 2025-06-19 22:04:16 | MASTER-Kislovodsk | (03h 24m 34.40s , +46d 45m 56.5s) | C | 60 | 17.3 | 5403 | 2025-06-19 22:08:25 | MASTER-Kislovodsk | (03h 02m 27.80s , +46d 47m 07.6s) | C | 60 | 17.3 | 5578 | 2025-06-19 22:11:20 | MASTER-Kislovodsk | (03h 06m 28.14s , +44d 52m 52.9s) | C | 60 | 17.3 | 5661 | 2025-06-19 22:12:43 | MASTER-Kislovodsk | (03h 17m 38.96s , +44d 51m 28.3s) | C | 60 | 17.2 | 5743 | 2025-06-19 22:14:05 | MASTER-Kislovodsk | (03h 12m 54.50s , +46d 46m 42.9s) | C | 60 | 17.4 | 5826 | 2025-06-19 22:15:28 | MASTER-Kislovodsk | (03h 24m 40.11s , +46d 45m 13.5s) | C | 60 | 17.3 | 6077 | 2025-06-19 22:19:39 | MASTER-Kislovodsk | (03h 02m 27.42s , +46d 47m 10.1s) | C | 60 | 17.4 | 6244 | 2025-06-19 22:22:26 | MASTER-Kislovodsk | (03h 06m 28.86s , +44d 53m 25.7s) | C | 60 | 17.5 | 6327 | 2025-06-19 22:23:49 | MASTER-Kislovodsk | (03h 17m 40.69s , +44d 52m 12.9s) | C | 60 | 17.3 | 6412 | 2025-06-19 22:25:14 | MASTER-Kislovodsk | (03h 12m 57.33s , +46d 47m 26.3s) | C | 60 | 17.4 | 6495 | 2025-06-19 22:26:37 | MASTER-Kislovodsk | (03h 24m 41.92s , +46d 45m 56.0s) | C | 60 | 17.3 | 6754 | 2025-06-19 22:30:56 | MASTER-Kislovodsk | (03h 02m 30.16s , +46d 48m 08.5s) | C | 60 | 17.4 | 6837 | 2025-06-19 22:32:19 | MASTER-Kislovodsk | (03h 00m 34.54s , +43d 00m 19.8s) | C | 60 | 17.1 | 6920 | 2025-06-19 22:33:42 | MASTER-Kislovodsk | (03h 11m 23.71s , +42d 59m 05.0s) | C | 60 | 17.4 | 7003 | 2025-06-19 22:35:05 | MASTER-Kislovodsk | (03h 06m 25.12s , +44d 54m 19.2s) | C | 60 | 17.5 | 7084 | 2025-06-19 22:36:26 | MASTER-Kislovodsk | (03h 17m 47.10s , +44d 52m 51.5s) | C | 60 | 17.4 | 7167 | 2025-06-19 22:37:49 | MASTER-Kislovodsk | (03h 12m 58.65s , +46d 46m 06.0s) | C | 60 | 17.5 | 7249 | 2025-06-19 22:39:11 | MASTER-Kislovodsk | (03h 24m 43.51s , +46d 45m 51.7s) | C | 60 | 17.5 | 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/40787. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38827] Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
by GCN Circulars 19 Jun '25

19 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40786 SUBJECT: Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB DATE: 25/06/19 21:58:33 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 772058337/250619860 at 20:38:52.44 UT on 19 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/40786. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38826] GRB 250615A: Kilonova-Catcher optical upper limits
by GCN Circulars 19 Jun '25

19 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40785 SUBJECT: GRB 250615A: Kilonova-Catcher optical upper limits DATE: 25/06/19 21:45:50 GMT FROM: Damien Turpin at CEA-Saclay <dturpin-astro(a)hotmail.com> D. Turpin (CEA-Saclay/Irfu), R. Hellot, M. Freeberg (KNC), C. Andrade(UMN), M. Pillas (ULiege), M. Tanasan (NARIT), S. Antier (OCA/IJCLAB) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 250615A (Dichiara et al., GCN 40736) detected by Swift/BAT with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the TEC160FL telescope operated by M. Freeberg and a CDK17 telescope located at AITP San Pedro Chile Observatory operated by R. Hellot. Our observations started at TGRB+7.6hr. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we do not detect any optical counterpart inside the Swift/XRT refined position (Goad et al., GCN 40739). We report our follow-up results in the table below: +---------------+-------------+---------+---------------------+--------------+ | Tmid-TGRB (hr)| Exp (s) | Filter | Magnitude | Instrument | +===============+=============+=========+=====================+==============+ | 7.9 | 6 x 300s | r (AB) | 20.1 (U.L., 5sigma) | TEC160FL | | 8.1 | 11 x 300s | g (AB) | 20.8 (U.L., 5sigma) | CDK17-AITP | | 8.5 | 6 x 300s | g (AB) | 20.4 (U.L., 5sigma) | TEC160FL | | 9.0 | 6 x 300s | i (AB) | 19.2 (U.L., 5sigma) | TEC160FL | | 9.6 | 11 x 300s | r (AB) | 20.2 (U.L., 5sigma) | CDK17-AITP | +---------------+-------------+---------+---------------------+--------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the sloan images were calibrated using the PanSTARRS DR1 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/40785. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38825] GRB 250619A: Fermi GBM Final Real-time Localization
by GCN Circulars 19 Jun '25

19 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40784 SUBJECT: GRB 250619A: Fermi GBM Final Real-time Localization DATE: 25/06/19 15:25:10 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 15:14:36 UT on 19 Jun 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250619A (trigger 772038881.892868 / 250619635). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 35.1, Dec = 27.0 (J2000 degrees, equivalent to J2000 02h 20m, 27d 00'), with a statistical uncertainty of 3.9 degrees. The angle from the Fermi LAT boresight is 40.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250619635/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250619635/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250619635/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40784. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38824] GRB 250617B: Assy AZT-20 Optical Observations
by GCN Circulars 19 Jun '25

19 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40783 SUBJECT: GRB 250617B: Assy AZT-20 Optical Observations DATE: 25/06/19 14:26:12 GMT FROM: Nicolai Pankov at HSE, IKI RAS <colinsergesen(a)gmail.com> N. Pankov (HSE, IKI), V. Kim (FAI), A. Pozanenko (IKI), M. Krugov (FAI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of GRB 250617B (Page et. al, GCN 40760; The Fermi GBM team, GCN 40763) using the 1.5-meter AZT-20 of the Assy-Turgen Observatory. The observations were conducted starting on 2025-06-18 at 18:02:27 UT, i.e. ~0.87 days since the Swift trigger. The series of 53*60 sec images was taken in the r'-filter. We detect the optical afterglow (Page et. al, GCN 40760, Moskvitin et. al, GCN 40761, Jelinek et. al, GCN 40762; Kumar et. al, GCN 40768; Lipunov et. al, GCN 40769; Grossan et. al, GCN 40771; Ma et. al, GCN 40772; Schneider et. al, GCN 40774; Antier et. al, GCN 40775; Corcoran et. al, GCN 40776; Turpin et. al, GCN 40777; Siegel & Page, GCN 40778). The preliminary photometry is given below: Date UT start t-T0 Exp. Filter OT Err. UL (mid, days) (n*s) (3sigma) 2025-06-18 18:02:27 0.87577 53*60 r' 21.58 0.04 22.5 The photometry has calibrated using nearby stars from PS1 (at the same coordinates as USNO-B1.0 stars given in Moskvitin et. al, GCN 40761) and has not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/40783. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38823] GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40782 SUBJECT: GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis DATE: 25/06/18 22:43:10 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> H. A. Krimm (NSF), S. D. Barthelmy (GSFC), R. Gupta (GSFC), 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), M. H. Siegel (PSU) (i.e. the Swift-BAT team): Using the data set from T-240 to T+962 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250612A (trigger #1323295) (Siegel, et al., GCN Circ. 40694). The BAT ground-calculated position is RA, Dec = 250.873, -38.948 deg which is RA(J2000) = 16h 43m 29.6s Dec(J2000) = -38d 56' 53.9" with an uncertainty of 4.3 arcmin, (radius, sys+stat, 90% containment). The partial coding was 64%. The BAT mask-weighted light curve showed a complex structure with a duration of about 300 sec. T90 (15-350 keV) is 274.17 +- 66.54 sec (estimated error including systematics). The time-averaged spectrum from T-0.58 to T+291.52 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 2.55 +- 0.43. The fluence in the 15-150 keV band is 1.0 +- 0.2 x 10^-06 erg/cm2. The 1-sec peak photon flux measured from T+0.62 sec in the 15-150 keV band is 0.9 +- 0.2 ph/cm2/sec. All the quoted errors are at the 90% confidence level. Given the BAT detection at a Galactic latitude of 4.6 deg and the absence of a detected X-ray afterglow in XRT observations ~ 17 hours post-trigger, a Galactic origin of this source remains plausible. If confirmed as a new Galactic transient, it would be designated Swift J1643.6−3854. The results of the batgrbproduct analysis are available at https://swift.gsfc.nasa.gov/results/batgrbcat/BAT_refined_circular/1323295 View this GCN Circular online at https://gcn.nasa.gov/circulars/40782. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38822] Fermi GRB 250617A: Global MASTER-Net observations report
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40781 SUBJECT: Fermi GRB 250617A: Global MASTER-Net observations report DATE: 25/06/18 22:15:43 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-Kislovodsk robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 250617A ( Fermi GBM team, GCN 40758) errorbox 1 days 17814 sec after notice time and 1 days 17823 sec after trigger time at 2025-06-18 21:06:16 UT, with upper limit up to 17.7 mag. The observations began at zenith distance = 66 deg. The sun altitude is -23.6 deg. The galactic latitude b = -25 deg., longitude l = 107 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2905762 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 104253 | 2025-06-18 21:06:16 | MASTER-Kislovodsk | (23h 40m 51.75s , +35d 31m 02.8s) | C | 60 | 17.7 | 104540 | 2025-06-18 21:11:02 | MASTER-Kislovodsk | (23h 27m 52.38s , +37d 23m 28.9s) | C | 60 | 16.0 | 104624 | 2025-06-18 21:12:26 | MASTER-Kislovodsk | (23h 37m 52.75s , +37d 24m 33.4s) | C | 60 | 16.3 | 104845 | 2025-06-18 21:16:08 | MASTER-Kislovodsk | (23h 46m 54.05s , +37d 24m 18.0s) | C | 60 | 17.3 | 104928 | 2025-06-18 21:17:31 | MASTER-Kislovodsk | (23h 57m 02.84s , +37d 22m 47.1s) | C | 60 | 16.6 | 105010 | 2025-06-18 21:18:53 | MASTER-Kislovodsk | (23h 40m 51.77s , +35d 28m 47.9s) | C | 60 | 17.1 | 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/40781. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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