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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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