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

[vsnet-grb-info 38630] Fermi GRB 250531A: Global MASTER-Net observations report
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40594 SUBJECT: Fermi GRB 250531A: Global MASTER-Net observations report DATE: 25/05/31 19:31:27 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 250531A ( Fermi GBM team, GCN 40593) errorbox 1696 sec after notice time and 1758 sec after trigger time at 2025-05-31 18:31:43 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 40 deg. The sun altitude is -35.3 deg. The galactic latitude b = 60 deg., longitude l = 256 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2887934 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 1789 | 2025-05-31 18:31:43 | MASTER-SAAO | (11h 22m 12.13s , +04d 56m 45.8s) | C | 60 | 19.5 | 1789 | 2025-05-31 18:31:43 | MASTER- | (11h 20m 21.93s , +05d 14m 38.0s) | C | 60 | 18.2 | 2577 | 2025-05-31 18:44:51 | MASTER-SAAO | (11h 30m 08.86s , +04d 56m 11.0s) | C | 60 | 19.3 | 2577 | 2025-05-31 18:44:51 | MASTER- | (11h 28m 19.20s , +05d 14m 00.4s) | C | 60 | 18.0 | 3202 | 2025-05-31 18:55:16 | MASTER-SAAO | (11h 22m 07.05s , +04d 58m 37.2s) | C | 60 | 19.5 | 3202 | 2025-05-31 18:55:16 | MASTER- | (11h 20m 17.21s , +05d 16m 27.2s) | C | 60 | 18.1 | 3797 | 2025-05-31 19:05:11 | MASTER-SAAO | (11h 30m 09.65s , +04d 57m 47.3s) | C | 60 | 19.3 | 3797 | 2025-05-31 19:05:11 | MASTER- | (11h 28m 19.98s , +05d 15m 38.0s) | C | 60 | 18.1 | 4208 | 2025-05-31 19:12:03 | MASTER-SAAO | (11h 22m 12.67s , +04d 57m 20.7s) | C | 60 | 19.4 | 4208 | 2025-05-31 19:12:03 | MASTER- | (11h 20m 22.82s , +05d 15m 08.3s) | C | 60 | 18.1 | 4404 | 2025-05-31 19:15:18 | MASTER-SAAO | (11h 30m 12.61s , +04d 57m 31.8s) | C | 60 | 19.3 | 4404 | 2025-05-31 19:15:18 | MASTER- | (11h 28m 22.60s , +05d 15m 21.9s) | C | 60 | 18.1 | 4501 | 2025-05-31 19:16:55 | MASTER-SAAO | (11h 20m 30.68s , +03d 04m 26.2s) | C | 60 | 19.4 | 4501 | 2025-05-31 19:16:55 | MASTER- | (11h 18m 41.05s , +03d 22m 16.5s) | C | 60 | 18.2 | 4594 | 2025-05-31 19:18:28 | MASTER-SAAO | (11h 28m 31.94s , +03d 05m 15.3s) | C | 60 | 19.4 | 4594 | 2025-05-31 19:18:28 | MASTER- | (11h 26m 42.18s , +03d 23m 06.9s) | C | 60 | 18.2 | 4688 | 2025-05-31 19:20:02 | MASTER-SAAO | (11h 24m 27.91s , +06d 51m 33.1s) | C | 60 | 19.4 | 4688 | 2025-05-31 19:20:02 | MASTER- | (11h 22m 37.83s , +07d 09m 23.1s) | C | 60 | 17.9 | 4783 | 2025-05-31 19:21:37 | MASTER-SAAO | (11h 32m 38.83s , +06d 51m 42.0s) | C | 60 | 19.2 | 4783 | 2025-05-31 19:21:37 | MASTER- | (11h 30m 48.71s , +07d 09m 32.8s) | C | 60 | 17.9 | 4877 | 2025-05-31 19:23:11 | MASTER-SAAO | (11h 22m 08.08s , +04d 59m 13.6s) | C | 60 | 19.5 | 4877 | 2025-05-31 19:23:11 | MASTER- | (11h 20m 18.35s , +05d 17m 04.3s) | C | 60 | 18.4 | 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/40594. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38629] GRB 250531A: Fermi GBM Final Real-time Localization
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40593 SUBJECT: GRB 250531A: Fermi GBM Final Real-time Localization DATE: 25/05/31 18:12:52 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 18:02:24 UT on 31 May 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250531A (trigger 770407349.523472 / 250531752). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 170.8, Dec = 5.4 (J2000 degrees, equivalent to J2000 11h 23m, 5d 24'), with a statistical uncertainty of 6.4 degrees. The angle from the Fermi LAT boresight is 37.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250531752/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250531752/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250531752/… View this GCN Circular online at https://gcn.nasa.gov/circulars/40593. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38628] EP#01709177494: Swift-XRT counterpart detection of known source
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40592 SUBJECT: EP#01709177494: Swift-XRT counterpart detection of known source DATE: 25/05/31 17:47:34 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-IASFPA), 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 Einstein Probe/WXT-detected source EP#01709177494, collecting 2.0 ks of Photon Counting (PC) mode data between T0+388 s and T0+6.2 ks after the trigger. A candidate counterpart has been found. The details of this source are: Source 1 (SWIFT J170930.3-263917): ================================== RA (J2000.0): 257.3766 = 17h 09m 30.38s Dec (J2000.0): -26.6548 = -26d 39' 17.3" Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 20 arcsec from the Einstein Probe/WXT position. Mean rate: 11.35 +/- 0.22 ct s^-1 Mean flux: (4.665 +/- 0.088)e-10 erg cm^-2 s^-1 Peak rate: 18.7 +/- 3.1 ct s^-1 Peak flux: (7.7 +/- 1.3)e-10 erg cm^-2 s^-1 ECF: 4.11e-11 erg cm^-2 ct^-1, assuming NH=4.40e+21 cm^-2, gamma=1.98; determined from a spectral fit. This matches a catalogued X-ray source LSXPS J170930.1-263918 in the LSXPS catalogue. Details: Separation: 3.2" from the XRT source Cat Rate: 1.2e+00 +/- 9.0e-03 ct s^-1 Cat Flux: 4.7e-11 +/- 3.7e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 5.7-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `RX J1709.5-2639' is 8.3" 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. 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/EP. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38627] EP#01709177494: Swift-XRT counterpart detection of known source
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40592 SUBJECT: EP#01709177494: Swift-XRT counterpart detection of known source DATE: 25/05/31 17:47:34 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-IASFPA), 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 Einstein Probe/WXT-detected source EP#01709177494, collecting 2.0 ks of Photon Counting (PC) mode data between T0+388 s and T0+6.2 ks after the trigger. A candidate counterpart has been found. The details of this source are: Source 1 (SWIFT J170930.3-263917): ================================== RA (J2000.0): 257.3766 = 17h 09m 30.38s Dec (J2000.0): -26.6548 = -26d 39' 17.3" Error: 3.5 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 20 arcsec from the Einstein Probe/WXT position. Mean rate: 11.35 +/- 0.22 ct s^-1 Mean flux: (4.665 +/- 0.088)e-10 erg cm^-2 s^-1 Peak rate: 18.7 +/- 3.1 ct s^-1 Peak flux: (7.7 +/- 1.3)e-10 erg cm^-2 s^-1 ECF: 4.11e-11 erg cm^-2 ct^-1, assuming NH=4.40e+21 cm^-2, gamma=1.98; determined from a spectral fit. This matches a catalogued X-ray source LSXPS J170930.1-263918 in the LSXPS catalogue. Details: Separation: 3.2" from the XRT source Cat Rate: 1.2e+00 +/- 9.0e-03 ct s^-1 Cat Flux: 4.7e-11 +/- 3.7e-13 erg cm^-2 s^-1 (0.3-10 keV) so the source is 5.7-sigma above the catalogued flux. There is no evidence for fading. A SIMBAD object `RX J1709.5-2639' is 8.3" 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. 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/EP. This circular is an officicial product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40592. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38626] GRB 250530C: BOOTES-7 optical upper limit
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40591 SUBJECT: GRB 250530C: BOOTES-7 optical upper limit DATE: 25/05/31 17:31:45 GMT FROM: I. Perez-Garcia at Institute of Astrophysics of Andalusia <ipg(a)iaa.es> I. Perez-Garcia, E. Fernandez-Garcia, S.-Y. Wu, M. D. Caballero-Garcia, R. Sanchez-Ramirez, S. Guziy, and A. J. Castro-Tirado (IAA-CSIC, Granada), C. Perez del Pulgar (Univ. of Malaga), L. Hernandez-Garcia (Univ. of Valparaiso), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXU), B.-B. Zhang (Nanjing Univ.), and A. Maury (Space Obs., San Pedro de Atacama), on behalf of a larger collaboration, report: Following the detection of GRB 250530C by Swift (Osborne et al., GCNC [40586](https://gcn.nasa.gov/circulars/40586)) the 0.6m BOOTES-7 robotic telescope at Space Observatory (San Pedro de Atacama, Chile) automatically responded to this high-energy event starting on May 21, 09:42:59 UT (i.e., 14.73 hour after detection), observing at low elevation (airmass ≈ 5). No optical transient is detected down to 16.4 mag (clear filter). On a coadd (11) of images at 09:51:43 UT (mid exposure time; i.e. 14.88 post burst), nothing is detected down to 18.2 mag. We would like to thank the staff at San Pedro de Atacama Space Observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/40591. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38625] GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40590 SUBJECT: GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations DATE: 25/05/31 15:39:50 GMT FROM: Rosa L. Becerra at Tor Vergata, Roma <rosa.becerra(a)roma2.infn.it> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Francis Fortin (IRAP), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Fredd Alvarez (UNAM), Dalya Akl (AUS), Camila Angulo (UNAM), Sarah Antier (OCA), 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 ZTF25aarhkyn/AT2025mgj (Andreoni et al., GCN Circ. 40566) using the DDRAGO wide-field imager on the COLIBRÍ telescope. We observed from 2025-05-31 03:33 to 04:32 UTC, after 9.6 days after the trigger of GRB 250521C (Fermi GBM team, GCN 40515) and obtained 16 minutes of exposure in each of the g, r and i filters. The data were reduced and stacked using the COLIBRÍ pipeline. 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 candidate ZTF25aarhkyn/AT2025mgj (Andreoni et al., GCN Circ. 40566), at preliminary magnitudes of: g = 19.34 +/- 0.03 r = 19.46 +/- 0.03 i = 19.50 +/- 0.05 Compared with the NOT observations reported by Martin-Carrillo et al. (GCN Circ. 40584), we estimate a steeper temporal decay index of ~1.5. The measured colours are consistent with those typically observed in GRBs, suggesting a similar nature. Additionally, the temporal evolution may indicate that AT2025mgj is a possible off-axis GRB; however, the absence of a nearby galaxy makes this scenario unlikely. Further observations are planned in order to unravel the nature of this object. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and Mexico (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, Mexico. View this GCN Circular online at https://gcn.nasa.gov/circulars/40590. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38624] GRB 250530C: Swift-XRT refined Analysis
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40589 SUBJECT: GRB 250530C: Swift-XRT refined Analysis DATE: 25/05/31 11:31:46 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> M.A. Williams (PSU), J.P. Osborne (U. Leicester), K.L. Page (U. Leicester), A.P. Beardmore (U. Leicester), M. Ferro (INAF-OAB), R. Brivio (INAF-OAB), A. D'Ai (INAF-IASFPA), S. Dichiara (PSU), J.A. Kennea (PSU) and P.A. Evans report on behalf of the Swift-XRT team: We have analysed 7.7 ks of XRT data for GRB 250530C, from 90 s to 52.0 ks after the trigger. The data comprise 9 s in Windowed Timing (WT) mode (taken while Swift was slewing), with the remainder in Photon Counting (PC) mode. The light curve can be modelled with a power-law decay with a decay index of alpha=0.80 (+/-0.04). A spectrum formed from the PC mode data can be fitted with an absorbed power-law with a photon spectral index of 1.55 (+0.20, -0.19). The best-fitting absorption column is 2.8 (+1.1, -0.9) x 10^21 cm^-2, in excess of the Galactic value of 1.7 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 5.0 x 10^-11 (6.1 x 10^-11) erg cm^-2 count^-1. A summary of the PC-mode spectrum is thus: Total column: 2.8 (+1.1, -0.9) x 10^21 cm^-2 Galactic foreground: 1.7 x 10^20 cm^-2 Excess significance: 4.7 sigma Photon index: 1.55 (+0.20, -0.19) If the light curve continues to decay with a power-law decay index of 0.80, the count rate at T+24 hours will be 0.012 count s^-1, corresponding to an observed (unabsorbed) 0.3-10 keV flux of 6.0 x 10^-13 (7.3 x 10^-13) erg cm^-2 s^-1. The results of the XRT-team automatic analysis are available at http://www.swift.ac.uk/xrt_products/01319125. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/40589. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38623] GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40588 SUBJECT: GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle DATE: 25/05/31 09:10:56 GMT FROM: Paolo D'Avanzo at INAF - OAB <paolo.davanzo(a)inaf.it> P. D'Avanzo, (INAF-OAB), A. Melandri (INAF-OAR), L. Izzo (INAF - OACn), M. G. Bernardini (INAF-OAB & LUPM), R. Brivio, M. Ferro (INAF-OAB), M. Pedani (INAF-TNG) on behalf of the CIBO collaboration report: We observed the field of the GRB 250530A detected by SVOM (Wang et al., GCN Circ. 40576) with the Italian 3.6m TNG telescope, located in Canary Islands (Spain), equipped with the near-infrared camera NICS in imaging mode. A series of images were obtained with the J filters starting on 2025-05-30T20:57:35 UT (i.e. 14.4 hours post T0). Within the refined Swift/XRT error circle (Evans et al., GCN Circ. 40579; see also: https://www.swift.ac.uk/SVOM/SVOM_FIELD00017/Source1.php) a faint object is detected in the co-added image at the following coordinates: RA (J2000) = 12:26:50.53 Dec (J2000) = -02:34:32.0 +/- 0.3" We note that these coordinates are consistent (within 0.4") with those of a catalogue source reported in the DESI Legacy Imaging Survey (Duncan et al., 2022, MNRAS, 512, 366). From preliminary photometry, we estimate for this source J ~ 21.0 mag (Vega; calibrated against the 2MASS catalogue). This research has made use of the VizieR catalogue access tool, CDS, Strasbourg, France (DOI : 10.26093/cds/vizier). The original description of the VizieR service was published in 2000, A&AS 143, 23. View this GCN Circular online at https://gcn.nasa.gov/circulars/40588. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38622] Swift GRB 250530C: Global MASTER-Net observations report
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40587 SUBJECT: Swift GRB 250530C: Global MASTER-Net observations report DATE: 25/05/31 04:17:20 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> V.Lipunov, E.Gorbovskoy, A.Kuznetsov, K.Zhirkov, I.Panchenko, N.Tiurina, P.Balanutsa, V.Topolev, D.Vlasenko, G.Antipov, A.Sankovich, Yu.Tselik, Ya.Kechin, V.Senik, A.Chasovnikov, K.Labsina, I. Gorbunov (Lomonosov MSU), O.Gress, N.Budnev (ISU), C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A.Sosnovskij (CrAO), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez, J.Martinez, A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) MASTER-SAAO robotic telescope (Global MASTER-Net: http://observ.pereplet.ru, Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L) located in South Africa (South African Astronomical Observatory) was pointed to the Swift GRB 250530C ( R. Caputo et al., GCN 40585) errorbox 31007 sec after notice time and 31055 sec after trigger time at 2025-05-31 03:36:18 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 79 deg. The sun altitude is -23.6 deg. The galactic latitude b = -51 deg., longitude l = 216 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2887090 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 31086 | MASTER-SAAO | C | 60 | 18.6 | 31086 | MASTER- | C | 60 | 13.1 | 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/40587. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38621] GRB 250530C: Enhanced Swift-XRT position
by GCN Circulars 31 May '25

31 May '25

TITLE: GCN CIRCULAR NUMBER: 40586 SUBJECT: GRB 250530C: Enhanced Swift-XRT position DATE: 25/05/31 00:38:35 GMT FROM: Phil Evans at U of Leicester <pae9(a)star.le.ac.uk> J.P. Osborne, A.P. Beardmore, P.A. Evans and M.R. Goad (U. Leicester) report on behalf of the Swift-XRT team. Using 2203 s of XRT Photon Counting mode data and 5 UVOT images for GRB 250530C, 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 = 55.17085, -22.44801 which is equivalent to: RA (J2000): 03h 40m 41.00s Dec (J2000): -22d 26' 52.8" with an uncertainty of 2.0 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/40586. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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