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[vsnet-grb-info 38810] Swift GRB 250617B: Global MASTER-Net observations report
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40769 SUBJECT: Swift GRB 250617B: Global MASTER-Net observations report DATE: 25/06/18 06:36:55 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 250617B ( K. L. Page et al., GCN 40760) errorbox 30652 sec after notice time and 30775 sec after trigger time at 2025-06-18 05:34:46 UT, with upper limit up to 18.6 mag. The observations began at zenith distance = 80 deg. The sun altitude is -74.8 deg. The galactic latitude b = -19 deg., longitude l = 89 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2906362 We obtain a following upper limits. Tmid-T0 | Site |Filt.| Expt. | Limit| Comment _________|_____________________|_____|_______|______|________ 30866 | MASTER-OAFA | C | 180 | 17.3 | 31415 | MASTER-OAFA | C | 60 | 17.4 | 31495 | MASTER-OAFA | C | 60 | 17.7 | 32132 | MASTER-OAFA | C | 180 | 18.2 | 32767 | MASTER-OAFA | C | 60 | 18.1 | 32845 | MASTER-OAFA | C | 60 | 18.1 | 33417 | 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/40769. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38809] GRB 250617B: GOTO optical upper limit
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40768 SUBJECT: GRB 250617B: GOTO optical upper limit DATE: 25/06/18 06:29:28 GMT FROM: Amit Kumar at Royal Holloway - UoL/ U of Warwick, UK <amitkundu515(a)gmail.com> A. Kumar, B. P. Gompertz, G. Ramsay, R. Starling, K. Ackley, M. J. Dyer, J. Lyman, K. Ulaczyk, D. O'Neill, B. Godson, D. Steeghs, D. K. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. P. Breton, L. K. Nuttall, and J. Casares report on behalf of the GOTO collaboration: We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022; Dyer et al. 2024) in response to the Swift/BAT and Fermi/GBM detected GRB 250617B (Page et al., GCN 40760; Fermi GBM Team, GCN 40763). Targeted observations were performed by GOTO-North at 2025-06-18T01:03:23 (4.03 hours after the trigger). The observation consisted of 4x90s exposures in the GOTO L-band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. We do not detect the optical afterglow of GRB 250617B (Page et al., GCN 40760; Moskvitin et al., 40761; Jelinek et al., 40762) down to a 3-sigma limiting magnitude of L > 20.3 AB mag. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/40768. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38808] GRB 250617B: Enhanced Swift-XRT position
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40767 SUBJECT: GRB 250617B: Enhanced Swift-XRT position DATE: 25/06/18 04:53:33 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 1717 s of XRT Photon Counting mode data and 2 UVOT images for GRB 250617B, 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 = 332.89670, +32.73250 which is equivalent to: RA (J2000): 22h 11m 35.21s Dec (J2000): +32d 43' 57.0" 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/40767. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38807] GRB 250617B: Fermi GBM Observation
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40766 SUBJECT: GRB 250617B: Fermi GBM Observation DATE: 25/06/18 04:32:42 GMT FROM: sumanbala2210(a)gmail.com S. Bala (USRA) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 21:01:28.19 UT on 17 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250617B (trigger 771886893/250617876). which was also detected by Swift BAT (Page et al. 2025, GCN 40760). The Fermi GBM on-ground location is consistent with the Swift BAT position. The angle from the Fermi LAT boresight is 91 degrees. The GBM light curve consists of two distinct emission episodes with a duration (T90) of about 32 s (50-300 keV). The time-averaged spectrum from T0-4.6 to T0+32.3 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.2 +/- 0.1 and the cutoff energy, parameterized as Epeak, is 40 +/- 2 keV. The event fluence (10-1000 keV) in this time interval is (3.4 +/- 0.1)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+23 s in the 10-1000 keV band is 6.9 +/- 0.3 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/40766. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38806] GRB 250615A: Swift-BAT refined analysis
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40765 SUBJECT: GRB 250615A: Swift-BAT refined analysis DATE: 25/06/18 02:48:55 GMT FROM: Takanori Sakamoto at AGU <tsakamoto(a)phys.aoyama.ac.jp> S. D. Barthelmy (GSFC), S. Dichiara (PSU), R. Gupta (GSFC), H. A. Krimm (NSF), S. Laha (GSFC/UMBC), A. Y. Lien (U Tampa), C. B. Markwardt (GSFC), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Parsotan (GSFC), D. Sadaula (GSFC/UMBC), T. Sakamoto (AGU) (i.e. the Swift-BAT team): Using the data set from T-239 to T+963 sec from the recent telemetry downlink, we report further analysis of BAT GRB 250615A (trigger #1324646) (Dichiara, et al., GCN Circ. 40736). The BAT ground-calculated position is RA, Dec = 290.384, 4.679 deg which is RA(J2000) = 19h 21m 32.1s Dec(J2000) = +04d 40' 44.0" with an uncertainty of 1.0 arcmin, (radius, sys+stat, 90% containment). The partial coding was 56%. The mask-weighted light curve shows a complex structure that starts at T-5 sec, peaks at T+5 sec, and ends at T+77 sec. T90 (15-350 keV) is 52.5 +- 10.3 sec (estimated error including systematics). The time-averaged spectrum from -5.2 to 77.3 sec is best fit by a simple power-law model. The power law index of the time-averaged spectrum is 1.22 +- 0.08. The fluence in the 15-150 keV band is 3.8 +- 0.2 x 10^-6 erg/cm2. The 1-sec peak photon flux measured from T+3.29 sec in the 15-150 keV band is 4.1 +- 0.3 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/1324646 View this GCN Circular online at https://gcn.nasa.gov/circulars/40765. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38805] The EP-WXT trigger 01709178990 is likely a flaring star
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40764 SUBJECT: The EP-WXT trigger 01709178990 is likely a flaring star DATE: 25/06/18 01:33:37 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-F. Liang (PMO, CAS), R.-Z. Li (YNAO, CAS), X.-L. Chen (YNU), H.-Z. Wu (HUST), X.-P. Xu and W.-M. Yuan (NAOC) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709178990 at the time of 2025-06-17T20:58:00, is likely a stellar flare associated with GQ Lup (Orion Variable). 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 2.2 X 10^32 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/40764. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38804] GRB 250617B: Fermi GBM Final Localization
by GCN Circulars 18 Jun '25

18 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40763 SUBJECT: GRB 250617B: Fermi GBM Final Localization DATE: 25/06/18 00:14:26 GMT FROM: sumanbala2210(a)gmail.com The Fermi GBM team reports the detection of a likely LONG GRB "At 21:01:28.19 UT on 17 June 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250617B (trigger 771886893/250617876). It is also detected by Swift-BAT/XRT (Page et al. 2025, GCN 40760) The Fermi GBM on-ground location is consistent with the Swift-XRT position. The angle from the Fermi LAT boresight is 91 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250617876/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250617876/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250617876/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/40763. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38803] GRB 250617B: Ondrejov D50 optical afterglow detection
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40762 SUBJECT: GRB 250617B: Ondrejov D50 optical afterglow detection DATE: 25/06/17 22:55:14 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny, A. Malenakova and R. Hudec (ASU CAS Ondrejov) report: We observed the position of the Swift-detected GRB 250617B (Page et al. GCN 40760) with the D50 telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. Our observation started at 21:29:35 UT, i.e. 27.8 min after the initial trigger and was performed without filter. We detect the optical afterglow (Page et al. GCN 40760) in a combined image with exp. mean time ~37.3 min after trigger (exposed 21:29:35-21:39:35 UT). The AB magnitude of the object at this frame is R = 18.64 +/- 0.27. We can confirm a decaying nature of the object with a temporal decay index of alpha = 0.85 ± 0.13. View this GCN Circular online at https://gcn.nasa.gov/circulars/40762. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38802] GRB 250617B: SAO RAS optical observations
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40761 SUBJECT: GRB 250617B: SAO RAS optical observations DATE: 25/06/17 22:54:57 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin, O. Spiridonova, Yu. Sotnikova (SAO RAS), A. Ghosh, S. Razzaque (CAPP, University of Johannesburg) We observed the field of the GRB 250617B (Page et al., GCN 40760) with SAO RAS 1-m telescope Zeiss-1000 equipped with CCD-photometer. We obtained series of 60, 120 and 300 sec. exposures in Rc band and also one BVIc series. Observations started on 21:28:06 UT, since 26 minutes after the trigger. The OT (Page et al., GCN 40760) is clearly visible in individual images with the brightness of R = 18.31 +/- 0.04 (t_mid - T0 = 0.5444 hours) and R = 18.66 +/- 0.04 (t_mid - T0 = 0.7635 hours). This preliminary photometry is calibrated against R2 magnitudes of following nearby USNO-B1 stars and not corrected for the Galaxy extinction. R.A. Dec. (2000) R2 22:11:38.4 +32:43:48.4 14.880 22:11:19.9 +32:44:17.5 15.280 22:11:41.0 +32:40:41.2 15.070 22:11:45.2 +32:42:19.8 14.690 Observations are ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/40761. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 38801] GRB 250617B: Swift detection of a burst with an optical counterpart
by GCN Circulars 17 Jun '25

17 Jun '25

TITLE: GCN CIRCULAR NUMBER: 40760 SUBJECT: GRB 250617B: Swift detection of a burst with an optical counterpart DATE: 25/06/17 21:24:27 GMT FROM: David Palmer at LANL <palmer(a)lanl.gov> K. L. Page (U Leicester), R. Gupta (NASA GSFC), A. Y. Lien (U Tampa), M. J. Moss (GSFC), D. M. Palmer (LANL), T. Sakamoto (AGU), M. H. Siegel (PSU) and M. A. Williams (PSU) report on behalf of the Neil Gehrels Swift Observatory Team: At 21:01:50.11 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250617B (trigger=1325580). Swift did not slew immediately to the burst. The BAT on-board calculated location is RA, Dec 332.902, +32.727 which is RA(J2000) = 22h 11m 37s Dec(J2000) = +32d 43' 38" with an uncertainty of 3 arcmin (radius, 90% containment, including systematic uncertainty). The currently available BAT light curve showed a complex structure with a duration of at least 10 sec. However, the light curve data from ~T+8 s to ~T+100 s is unavailable in the immediate data downlink. The peak count rate was ~900 counts/sec (15-350 keV), at ~0 sec after the trigger. The XRT began observing the field at 21:15:03.4 UT, 793.4 seconds after the BAT trigger. Using promptly downlinked data we find an uncatalogued X-ray source with an enhanced position: RA, Dec 332.89735, 32.73270 which is equivalent to: RA(J2000) = 22h 11m 35.36s Dec(J2000) = +32d 43' 57.7" with an uncertainty of 1.9 arcseconds (radius, 90% containment). This location is 24 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 (9.66 x 10^20 cm^-2, Willingale et al. 2013), with an excess column of 5.7 (+4.15/-3.46) x 10^21 cm^-2 (90% confidence). UVOT took a finding chart exposure of 150 seconds with the White filter starting 796 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 22:11:35.25 = 332.89686 DEC(J2000) = +32:43:56.9 = 32.73247 with a 90%-confidence error radius of about 0.62 arc sec. This position is 1.9 arc sec. from the center of the XRT error circle. The estimated magnitude is 18.17 with a 1-sigma error of about 0.15. No correction has been made for the expected extinction corresponding to E(B-V) of 0.087. Burst Advocate for this burst is K. L. Page (klp5 AT leicester.ac.uk). 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/40760. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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