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

[vsnet-grb-info 40065] GRB 250925A: JinShan optical observations
by GCN Circulars 26 Sep '25

26 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41998 SUBJECT: GRB 250925A: JinShan optical observations DATE: 25/09/26 09:44:45 GMT FROM: liuxing(a)nao.cas.cn GRB 250925A: JinShan optical observations X. Liu (NAOC), S.Y. Fu (HUST) S.Q. Jiang, J. An, Z.P. Zhu, D. Xu (NAOC), A.D. Zhu, L. Lei (HUST), J.Z. Liu (XAO) report on behalf of a large collaboration: We observed the field of GRB 250925A detected by Swift/BAT (Dichiara, GCN 41985), using the 100cm-A (100A) and 100cm-C telescope (100C) of the JinShan project, located at Altay, Xinjiang, China. The 100A observation automatically started at 17:05:21.07 UT on 2025-09-25, i.e., 54.57 seconds after the BAT trigger, and the 100C observation started one hour later. A series of frames were obtained in the Sloan r- and z- bands. The reported optical afterglow (Corcoran et al., GCN41990; Bochenek et al., GCN 41991; Masi et al., GCN 41992; Méndez et al., GCN 41995; Méndez et al., GCN 41995) was detected in our stacked 100C images in both r- and z- bands. Preliminary photometric results are as follows: T-mid (hr) | Filter | Exposure | Mag 2.05 | z | 24x180s | 20.26 +/- 0.15 3.02 | r | 8x200s | 22.10 +/- 0.20 calibrated with nearby Pan-STARRS1 DR2 stars without the Galactic extinction correction. We acknowledge the excellent support from T.Q. Chen and J.F. Zhang for enabling these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/41998. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40064] GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+
by GCN Circulars 26 Sep '25

26 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41997 SUBJECT: GRB 250925A: 1.5m OSN optical detection and redshift with the 10.4m GTC/OSIRIS+ DATE: 25/09/26 09:41:57 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> A. J. Castro-Tirado, A. Sota, R. Sanchez-Ramirez, S. Guziy, M.D. Caballero-Garcia, S.-Y. Wu and I. Perez-Garcia (IAA-CSIC), D. Garcia-Alvarez (GTC, IAC), A. Perez-Romero (GTC), A. Cabrera-Lavers (IAC, GTC), S. B. Pandey (ARIES), M. Gritsevich (Univ. of Helsinki), Y.-D. Hu (GXI), A. Nicuesa Guelbenzu (Tautenburg Obs.), L. Piro (INAF/IAPS) and B.-B. Zhang (NJU), on behalf of a larger collaboration, report: Following the detection of GRB 250925A by Swift (Dichiara et al. GCNC 41985) we conducted optical follow-up observations with the 1.5m OSN at Observatorio de Sierra Nevada (Granada), starting on Sep 25 at 21:47 UT. At the position of the X-ray afterglow (Page et al. GCNC 41988), we detect the optical afterglow (with I = 19.7 +/- 0.1) previously discovered at the NOT (Corcoran et al. (GCNC 41990) and also reported by means of other ground-based telescopes (Bochenek et al. GCNC 41991, Masi et al. GCNC 41992, Moreno Mendez et al. GCNC 41995). Additional observations were conducted with the 10.4m GTC telescope, at the Spanish Roque de los Muchachos Observatory, on the island of La Palma, equipped with the OSIRIS+ instrument. The spectroscopic observations consisted of 900s exposures using grisms R1000B and R2500I, with a joint spectral coverage between 3,600 and 10,000 A. The observations started on Sep 25, 21:57 UT (i.e. 4.9 h after the burst trigger). We detect a strong DLA at ~6000 A, among a plethora of metal absorption lines, that we interpret as coming from NV, SiII, SiII*, OI, CII, SiIV, CIV, FeII, FeII*, AlII, AlII, NiII, MgII, MgI at z=3.899, consistent with the COLIBRI photometry as suggested (Moreno Mendez et al. GCNC 41995). The detection of fine structure features confirms the association of this absorption system to GRB 250925A. View this GCN Circular online at https://gcn.nasa.gov/circulars/41997. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40063] GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations
by GCN Circulars 26 Sep '25

26 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41996 SUBJECT: GRB 250919A / EP250919a: Global MASTER Net before, during and after trigger optical observations DATE: 25/09/26 06:58:48 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> R.Podesta, C.Francile, F. Podesta, E. Gonzalez (OAFA, San Juan Uni., Argentina); N.Tiurina, E.Gorbovskoy, V.Lipunov, A.Kuznetsov, A.Sankovich, G.Antipov, P.Balanutsa, Yu. Tselik, A. Sosnovskiy, M.Shilova, A.Chasovnikov, V.Topolev, K.Zhirkov, Ya.Kechin, V.Senik, D.Vlasenko(Lomonosov MSU, SAI, Moscow), D.Buckley, (SAAO, South Africa) O.Gress, N.Budnev (ISU, Irkutsk), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity), V.M.Pillet, R.Rebolo Lopez (The Instituto de Astrofisica de Canarias, Spain), L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez,A.R.Corella, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysic Observatory, Mexico) The MASTER-OAFA robotic wide-field camera, located in Argentina (OAFA observatory of San Juan National University [1], during a regular survey, obtained an image of the region of the sky containing the point with coordinates MASTER OT J195412.89-485016.4 (GCN 41893) and source (Li et al., GCN 41877) before, during and after the Fermi trigger moment (GBM GCN 41874, GCN 41876, GCN 41890; LAT GCN 41884, Ttrigger=00:28:52) of GRB 250919A . Very bright optical counterpart MASTER OT J195412.89-485016.4 promptly detected at the agnitude ~ 9 m. This transient was first publishied as EP250919a optical counterpart by Las Cumbres observatory (GCN 41877, t_detection=03:02:52.800 UTC) and as Fermi GRB 250919A/EP250919a optical counterpart by Gemini-South (LEvan et al. GCN 41883) with reshift detection z = 1.145 X-ray counterpart was also detected by Swift (Osborne et al. GCN 41885) with OT afterglow detection by UVOT (Oates et al. GCN 41886), NuSTAR (GCN 41888) and Svom (41882). The full 4 nights light curve is currently being processed. [1] - V.M. Lipunov, V.G. Kornilov, E.S. Gorbovskoy, N.A. Tiurina & A.S.Kuznetsov, 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics, Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/41996. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40062] GRB 250925A: COLIBRÍ optical photometry of the afterglow
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41995 SUBJECT: GRB 250925A: COLIBRÍ optical photometry of the afterglow DATE: 25/09/26 05:52:29 GMT FROM: enriquemm(a)astro.unam.mx Enrique Moreno Méndez (UNAM), N. A. Rakotondrainibe (LAM), Alan M. Watson (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (OCA), Rosa L. Becerra (U Roma), Nathaniel R. Butler (ASU) , Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Kin Ocelotl López (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), and Antonio de Ugarte Postigo (LAM): We imaged the field of the Swift GRB 250925A (Dichiara et al., GCN Circ. 41985) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2025-09-26 02:45 to 04:30 UTC (from 9.7 to 11.4 hours after the trigger) and obtained 32/32/64 minutes of exposure in the r/i/z 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 source reported by Corcoran et al. (GCN Circ. 41990) at preliminary magnitudes of: r = 23.07 +/- 0.18 i = 21.62 +/- 0.07 z = 21.02 +/- 0.06 The source has faded, confirming that it is the afterglow. Compared to the early observations reported by Corcoran et al., we derive a temporal index of about -0.9 in z. The very red r-i color is suggestive of a GRB at a moderately high redshift with a break in r. 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. 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/41995. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40061] Fermi GRB 250926A: Global MASTER-Net observations report
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41994 SUBJECT: Fermi GRB 250926A: Global MASTER-Net observations report DATE: 25/09/26 01:31:05 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 250926A ( Fermi GBM team, GCN 41993) errorbox 71 sec after notice time and 114 sec after trigger time at 2025-09-26 00:23:18 UT, with upper limit up to 19.5 mag. The observations began at zenith distance = 53 deg. The sun altitude is -47.4 deg. The galactic latitude b = -20 deg., longitude l = 210 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3000001 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 124 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 28m 42.38s , -08d 02m 54.5s) | C | 20 | 18.4 | 159 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 28m 42.37s , -08d 02m 54.4s) | C | 90 | 19.4 | Coadd 124 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 30m 34.49s , -08d 18m 14.3s) | C | 20 | 18.4 | 159 | 2025-09-26 00:23:18 | MASTER-SAAO | (05h 30m 34.49s , -08d 18m 14.2s) | C | 90 | 19.5 | Coadd 168 | 2025-09-26 00:23:57 | MASTER-SAAO | (05h 28m 42.29s , -08d 02m 53.3s) | C | 30 | 18.6 | 168 | 2025-09-26 00:23:57 | MASTER-SAAO | (05h 30m 34.43s , -08d 18m 12.4s) | C | 30 | 18.7 | 222 | 2025-09-26 00:24:46 | MASTER-SAAO | (05h 28m 42.23s , -08d 02m 51.9s) | C | 40 | 18.8 | 222 | 2025-09-26 00:24:46 | MASTER-SAAO | (05h 30m 34.40s , -08d 18m 10.2s) | C | 40 | 18.8 | 286 | 2025-09-26 00:25:45 | MASTER-SAAO | (05h 28m 42.20s , -08d 02m 50.5s) | C | 50 | 18.9 | 286 | 2025-09-26 00:25:45 | MASTER-SAAO | (05h 30m 34.36s , -08d 18m 08.0s) | C | 50 | 19.0 | 360 | 2025-09-26 00:26:54 | MASTER-SAAO | (05h 28m 42.14s , -08d 02m 49.6s) | C | 60 | 19.1 | 360 | 2025-09-26 00:26:54 | MASTER-SAAO | (05h 30m 34.29s , -08d 18m 06.4s) | C | 60 | 19.2 | 651 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 28m 05.28s , -07d 01m 44.0s) | C | 60 | 18.7 | 711 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 28m 05.28s , -07d 01m 44.0s) | C | 180 | 19.4 | Coadd 651 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 29m 57.17s , -07d 16m 59.6s) | C | 60 | 18.8 | 711 | 2025-09-26 00:31:44 | MASTER-SAAO | (05h 29m 57.17s , -07d 16m 59.6s) | C | 180 | 19.5 | Coadd 731 | 2025-09-26 00:33:04 | MASTER-SAAO | (05h 28m 05.23s , -07d 01m 43.2s) | C | 60 | 18.7 | 731 | 2025-09-26 00:33:04 | MASTER-SAAO | (05h 29m 57.12s , -07d 16m 58.5s) | C | 60 | 18.8 | 810 | 2025-09-26 00:34:23 | MASTER-SAAO | (05h 28m 05.16s , -07d 01m 43.1s) | C | 60 | 18.7 | 810 | 2025-09-26 00:34:23 | MASTER-SAAO | (05h 29m 57.08s , -07d 16m 58.0s) | C | 60 | 18.8 | 890 | 2025-09-26 00:35:43 | MASTER-SAAO | (05h 28m 05.10s , -07d 01m 42.8s) | C | 60 | 18.6 | 890 | 2025-09-26 00:35:43 | MASTER-SAAO | (05h 29m 57.06s , -07d 16m 57.6s) | C | 60 | 18.8 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. View this GCN Circular online at https://gcn.nasa.gov/circulars/41994. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40060] GRB 250926A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41993 SUBJECT: GRB 250926A: Fermi GBM Final Real-time Localization DATE: 25/09/26 00:31:52 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 00:21:23 UT on 26 Sep 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 250926A (trigger 780538888.96614 / 250926015). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 83.0, Dec = -7.0 (J2000 degrees, equivalent to J2000 05h 31m, -7d 00'), with a statistical uncertainty of 1.8 degrees. The angle from the Fermi LAT boresight is 79.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926015/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926015/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn250926015/… View this GCN Circular online at https://gcn.nasa.gov/circulars/41993. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40059] GRB 250925A: Optical Observations via Virtual Telescope Project, Italy
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41992 SUBJECT: GRB 250925A: Optical Observations via Virtual Telescope Project, Italy DATE: 25/09/26 00:08:38 GMT FROM: Gianluca Masi at Virtual Telescope Project <gianluca(a)bellatrixobservatory.org> Gianluca Masi, Virtual Telescope Project (Italy), reports: We attempted to observe the optical counterpart (Dichiara et al., GCN 41985) of GRB 250925A with the 14” robotic unit available at the Virtual Telescope Project facility in Manciano, Italy, equipped with a KAF-3200E based CCD camera, its QE peaking (90%) in the red part of the spectrum. We collected 9, 300-second unfiltered exposures, then we averaged them. The central time of the resulting stack was 25 Sept., 23:27 UTC, that is about 6.38 hours after the burst. We detected a faint object at the following position (J2000.0): RA: 22 44 51.32 Decl.: +46 33 20.7 R= 21.5 (assuming R-mags from Gaia DR2 for the reference stars). This position is consistent with Corcoran et al., GCN 41990 and Bochenek et al., GCN 41991 View this GCN Circular online at https://gcn.nasa.gov/circulars/41992. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40058] GRB250925A: Liverpool Telescope optical observations
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41991 SUBJECT: GRB250925A: Liverpool Telescope optical observations DATE: 25/09/25 21:46:51 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek and D. A. Perley (LJMU) report: We observed the field of GRB250925a detected by Swift (Dichiara et al., GCN 41915) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x100s exposures in the SDSS i’ filter starting at 2025-09-25 20:59:51 UT, approximately 3.92 hours after the trigger. We report a detection in the stacked image at the position of the candidate optical counterpart (Corcoran et al., GCN 41990), inside the XRT error field (Page et al., GCN 41988). The magnitude of the candidate afterglow is i = 20.78 ± 0.03. The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/41991. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40057] GRB 250925A: NOT optical afterglow candidate
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41990 SUBJECT: GRB 250925A: NOT optical afterglow candidate DATE: 25/09/25 21:19:47 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> G. Corcoran (UCD), L. Cotter (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), A. de Ugarte Postigo (LAM), B. Schneider (LAM), K. Valeckas (NOT and NBI), report on behalf of a larger collaboration: We observed the field of GRB 250925A (Dichiara et al., GCN 41985) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC imager. Observations started on 2025 Sep 25.847 UT (3.254 hr after trigger) and consisted of 3x300 s and 5x200 s in each of the SDSS r and z bands. Within the UVOT-enhanced XRT position (Page et al., GCN 41988), we detect an object which is not seen in Pan-STARRS archival imaging of this field. Its coordinates are: RA(J2000) = 22:44:51.31 Dec(J2000) = +46:33:21.3 with an estimated error of 0.3”. Calibrated against nearby objects from Pan-STARRS, we measure AB magnitudes (not corrected for Galactic extinction): r = 21.99 +- 0.10 (3.30 hr after the trigger) z = 19.96 +- 0.05 (3.69 hr after the trigger) We note that this is a rather red r-z color, even considering the non-negligible but still modest Galactic extinction A_V ~ 0.75 mag along this line of sight (Schlafly & Finkbeiner 2011; doi:10.1088/0004-637X/737/2/103). This might indicate either an intrinsic spectral slope, or unaccounted extinction in our Galaxy or in the GRB host. View this GCN Circular online at https://gcn.nasa.gov/circulars/41990. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40056] GRB 250925A: Leavitt Observatory optical upper limit
by GCN Circulars 25 Sep '25

25 Sep '25

TITLE: GCN CIRCULAR NUMBER: 41989 SUBJECT: GRB 250925A: Leavitt Observatory optical upper limit DATE: 25/09/25 21:19:01 GMT FROM: leavittob(a)gmail.com E. Pavoni, L. Moretti (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 observed the field of GRB 250925A detected by Swift (Dichiara et al., GCN 41985), using our Ritchey-Chrétien telescope (D=250 mm, F/D=8). The observations began approximately 128 minutes after the trigger, stacking a set of CCD images of 180 seconds each, with good weather conditions. All images were processed by a single data processing pipeline based on astropy package (Astropy Collaboration et al., 2022ApJ...935..167A). No credible candidate was detected in our stacked frame within the Swift error circle. We derived the following upper limit: | Mid-Time (UTC) | Filter | Exp. Time | Upper limit (3-sigma) | | ------------------- | ------ | ----------- | ----------------------| | 2025-09-25T19:42:51 | CR | 20x180 sec | 20.49 | CR magnitude is unfiltered with R zero point. The photometry was calibrated with the Pan-STARRS cat. (R-mags obtained via Lupton 2005 transformations). Not corrected for the Galactic extinction. This upper limit is consistent with the report by GROWTH-India Telescope (Saikia et al., GCN 41986). This message may be cited. Reference: https://leavittobservatory.altervista.org View this GCN Circular online at https://gcn.nasa.gov/circulars/41989. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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