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

[vsnet-grb-info 39318] GRB 250807A: Swift detection of a burst with an optical counterpart
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41262 SUBJECT: GRB 250807A: Swift detection of a burst with an optical counterpart DATE: 25/08/07 11:03:36 GMT FROM: noelklin(a)umbc.edu N. J. Klingler (GSFC/UMBC/CRESSTII), R. Brivio (INAF-OAB), J. J. DeLaunay (PSU), R. Gupta (NASA GSFC), J. A. Kennea (PSU), K. L. Page (U Leicester) and C. Salvaggio (INAF-OAB) report on behalf of the Neil Gehrels Swift Observatory Team: At 10:46:08.44 UT, the Swift Burst Alert Telescope (BAT) triggered and located GRB 250807A (trigger=1340514). Swift slewed immediately to the burst. The BAT on-board calculated location is RA, Dec 51.420, -47.877 which is RA(J2000) = 03h 25m 41s Dec(J2000) = -47d 52' 38" 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 80 sec. The peak count rate was ~19000 counts/sec (15-350 keV), at ~35 sec after the trigger. The XRT began observing the field at 10:47:49.5 UT, 101.1 seconds after the BAT trigger. XRT found a bright, uncatalogued X-ray source located at RA, Dec 51.4478, -47.8880 which is equivalent to: RA(J2000) = 03h 25m 47.47s Dec(J2000) = -47d 53' 16.8" with an uncertainty of 4.8 arcseconds (radius, 90% containment). This location is 77 arcseconds from the BAT onboard position, within the BAT error circle. No event data are yet available to determine the column density using X-ray spectroscopy. UVOT took a finding chart exposure of 150 seconds with the White filter starting 111 seconds after the BAT trigger. There is a candidate afterglow in the rapidly available 2.7'x2.7' sub-image at RA(J2000) = 03:25:47.59 = 51.44829 DEC(J2000) = -47:53:16.2 = -47.88782 with a 90%-confidence error radius of about 0.75 arc sec. This position is 1.3 arc sec. from the center of the XRT error circle. The estimated magnitude is 17.98 with a 1-sigma error of about 0.14. No correction has been made for the expected extinction corresponding to E(B-V) of 0.011. Burst Advocate for this burst is N. J. Klingler (noelklin AT umbc.edu). 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/41262. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39317] IceCube Alert 250804.84: Global MASTER-Net observations report
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41261 SUBJECT: IceCube Alert 250804.84: Global MASTER-Net observations report DATE: 25/08/07 10:39:22 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 IceCube Alert 250804.84 (trigger No 19914656,05h 18m 00.00s , +16d 39m 00.0s, R=0.7) errorbox 2 days 50708 sec after notice time and 2 days 50755 sec after trigger time at 2025-08-07 10:22:22 UT, with upper limit up to 18.3 mag. Observations started at twilight. The observations began at zenith distance = 58 deg. The sun altitude is -12.1 deg. The galactic latitude b = -11 deg., longitude l = 187 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2960236 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 223586 | 2025-08-07 10:22:22 | MASTER-OAFA | (05h 15m 58.59s , +15d 20m 12.5s) | C | 60 | 18.3 | 223646 | 2025-08-07 10:22:22 | MASTER-OAFA | (05h 15m 58.59s , +15d 20m 12.5s) | C | 180 | 18.1 | Coadd 223662 | 2025-08-07 10:23:38 | MASTER-OAFA | (05h 15m 57.44s , +15d 21m 13.0s) | C | 60 | 17.5 | 223737 | 2025-08-07 10:24:53 | MASTER-OAFA | (05h 16m 04.31s , +15d 20m 13.9s) | C | 60 | 15.5 | 223811 | 2025-08-07 10:26:07 | MASTER-OAFA | (05h 18m 10.03s , +16d 30m 57.3s) | C | 60 | 15.8 | 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/41261. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39316] GRB 250806A: EP-FXT observation
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41260 SUBJECT: GRB 250806A: EP-FXT observation DATE: 25/08/07 09:46:25 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R. D. Liang, H. N. Yang (NAO, CAS), Y. J. Zhang (THU), W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team: GCN #41243 reported the detection of GRB 250806A with SVOM on 2025-08-06T08:00:11 UTC (T0) and the X-ray conterpart was detected with swift-XRT (GCN #41249). The Follow-up X-ray Telescope (FXT) on board Einstein Probe observed GRB 250806A about 4 ks (2025-08-06T09:04:02, UTC) after T0, with an exposure time of 790 seconds. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 348.4308, DEC =1.3556 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent positionally with the swift-XRT transient (GCN #41249). The angular distance between the FXT position and SVOM-MXT detection (GCN #41243) is 106 arcseconds. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 4.5 x 10^20 cm^-2 and a photon index of 1.25 (-1.14/+1.11). The derived average unabsorbed 0.5-10 keV flux is 1.49 (-0.98/+6.08) x 10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. 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/41260. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39315] EP#01709198415/EP250806a: Swift-XRT observations
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41259 SUBJECT: EP#01709198415/EP250806a: Swift-XRT observations DATE: 25/08/07 09:00:17 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 Einstein Probe/WXT-detected source EP250806a (EP trigger 01709198415, GCN #41246), collecting 1.5 ks of Photon Counting (PC) mode data between T0+11 ks and T0+13 ks after the trigger. No X-ray sources have been detected in the WXT error region. 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/EP_FIELD00057. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/41259. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39314] EP250806a: Global MASTER-Net observations report
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41258 SUBJECT: EP250806a: Global MASTER-Net observations report DATE: 25/08/07 08:54:20 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 EP250806a ( EP Team et al., GCN 41246) errorbox 28505 sec after notice time and 32341 sec after trigger time at 2025-08-06 18:17:21 UT, with upper limit up to 17.5 mag. The observations began at zenith distance = 72 deg. The sun altitude is -28.1 deg. The galactic latitude b = -57 deg., longitude l = 25 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=2962585 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 32371 | 2025-08-06 18:17:21 | MASTER-SAAO | (22h 16m 28.41s , -27d 00m 15.2s) | C | 60 | 17.4 | 32371 | 2025-08-06 18:17:21 | MASTER-SAAO | (22h 18m 28.98s , -27d 15m 51.3s) | 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/41258. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39313] EP250802a: EP-FXT follow-up observation
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41257 SUBJECT: EP250802a: EP-FXT follow-up observation DATE: 25/08/07 08:39:07 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (NJU), X. Mao, T. Zhao, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT performed a follow-up observation of EP250802a (GCN 41221) at 2025-08-04T04:10:31 (UTC), about 42 hours after the WXT detection, with an exposure time of 1.5 ks. The source was also followed by several optical telescopes (GCN 41222, GCN 41223, GCN 41224, GCN 41227). Three uncatalogued sources are detected within the WXT error circle, among which Source 1 is spatially consistent with a known star TYC 2158-1481-1. Preliminary analysis on these sources are automatically conducted, and the details are listed as follows. Source 1: EPF_J201319.4+244937 RA (J2000): 303.3308 Dec (J2000): 24.8268 Flux: 4.63 x 10^-13 erg/s/cm^2 (observed, 0.5-10 keV) Flux_err: 1.25 x 10^-13 erg/s/cm^2 (1 sigma) Note: This source is spatially consistent with the a known star TYC 2158-1481-1. Source 2: EPF_J201330.2+244901 RA (J2000): 303.3759 Dec (J2000): 24.8168 Flux: 2.21 x 10^-13 erg/s/cm^2 (observed, 0.5-10 keV) Flux_err: 6.99 x 10^-14 erg/s/cm^2 (1 sigma) Source 3: EPF_J201318.2+245121 RA (J2000): 303.3260 Dec (J2000): 24.8559 Flux: 3.56 x 10^-13 erg/s/cm^2 (observed, 0.5-10 keV) Flux_err: 9.84 x 10^-14 erg/s/cm^2 (1 sigma) 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/41257. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39312] EP250806a: refined analysis of the EP-WXT and EP-FXT observations
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41256 SUBJECT: EP250806a: refined analysis of the EP-WXT and EP-FXT observations DATE: 25/08/07 04:42:31 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> R. D. Liang, H. N. Yang (NAO, CAS), Y. J. Zhang (THU), W. D. Zhang (NAO, CAS) report on behalf of the Einstein Probe team: The X-ray transient EP250806a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Yang et al., GCN 41246). Refined analysis of the WXT data shows that the event started at T0=2025-08-06 09:02:10.82 (UTC) and lasted for about 50 s. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.47 x 10^20 cm^-2 and a photon index of 2.3 (-/+0.6). The derived average unabsorbed 0.5-4 keV flux is 4.1(-/+0.5) x 10^(-11) erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source autonomously about 1 ks after T0. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 335.1028, DEC = 26.8738 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent positionally with the WXT transient. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a Galactic hydrogen column density of 1.47 x 10^20 cm^-2 and a photon index of 3.24 (-/+0.25). The derived average unabsorbed 0.5-10 keV flux is 8.42 (-/+0.47) x 10^(-13) erg/s/cm^2 during the time interval from 0 to 1000 seconds after the start of the observation. The uncertainties are at the 90% confidence level for the above parameters. 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/41256. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39311] EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41255 SUBJECT: EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS DATE: 25/08/07 03:11:09 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Rosa L. Becerra (U Roma), Alan M. Watson (UNAM), Fredd Sánchez Álvarez (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Camila Angulo (UNAM), Jean-Luc Atteia (IRAP), Dalya Akl (AUS), Sarah Antier (OCA), 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), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: In Fortin et al. (GCN Circ. 41248), we reported no optical counterpart of the EP X-ray transient EP250806a (Yang et al., GCN Circ. 41246) in a 32-minute exposure in i taken with COLIBRÍ. We here discuss our full 60-minute exposure in i taken from 2025-08-06 10:27 to 11:48 UTC (from 1.1 to 2.5 hours after the trigger). 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. At the position of the VT optical candidate reported by Xin et al. (GCN Circ. 41254), we detect a source with i = 22.47 +/- 0.11 This magnitude is similar to the magnitude of VT_R = 22.6 +/- 0.2 about 8 hours after the trigger reported by Xin et al. Furthermore, the source is visible in the Legacy Survey DR10 (Dey et al. 2019) catalog with i = 22.0 +/- 0.07 In both our image and the LS image, the source appears to be resolved. Given the detection in the LS image, the lack of fading between our observations and the VT observations, and the resolved appearance, we suggest that this is not the optical counterpart of the EP transient. 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/41255. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39310] EP250806a: SVOM /VT optical candidate
by GCN Circulars 07 Aug '25

07 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41254 SUBJECT: EP250806a: SVOM /VT optical candidate DATE: 25/08/07 01:45:11 GMT FROM: Liping Xin at NAOC, SVOM <xlp(a)nao.cas.cn> L. P. Xin, H. L. Li, Y. N. Ma, Y. L. Qiu, C. Wu, Z. H. Yao, 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), H. N. Yang, R. D. Liang (NAOC), Y. J. Zhang (THU), W. D. Zhang (NAOC) report on behalf of the SVOM and EP teams. SVOM performed a Target of Opportunity observation of EP250806a detected by EP/WXT (Yang et al., GCN 41246). SVOM/VT began observing the field at 2025-08-06T17:09:08 UTC, 7.9 hours after the EP trigger time, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. An uncatalogued source is found using VT X-band data within the errorbox of EP/FXT (Yang et al., GCN 41246), compared to Legacy survey. The optical source is at R.A., Dec 335.103182, -26.877607 degrees: RA (J2000) = 22:20:24.76 Dec (J2000) = -26:52:39.38 with an uncertainty of 0.5 arcsec. The source is detected in both VT_B and VT_R images. The magnitudes are derived as below: DeltaT(Mid time) | exposure time (s) | band | mag (AB) | mag err -------------------- |-------------------|------|----------|-------- 8.19 hours | 49*50 | VT_B | 23.3 | 0.2 8.19 hours | 49*50 | VT_R | 22.6 | 0.2 Our photometry is 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 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/41254. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 39309] GRB 250806A: J-band upper limit from WINTER
by GCN Circulars 06 Aug '25

06 Aug '25

TITLE: GCN CIRCULAR NUMBER: 41253 SUBJECT: GRB 250806A: J-band upper limit from WINTER DATE: 25/08/06 20:53:38 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> GRB 250806A: J-band upper limit from WINTER Benjamin Schneider (LAM), Robert Stein (UMD), Geoffrey Mo (MIT), Tomas Ahumada (Caltech), Viraj Karambelkar (Caltech), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of the SVOM GRB 250806A (Xie et al., GCN 41243; Wu et al., GCN 41244; Fortin et al., GCN 41245; Freeberg et al., GCN 41247; Campana et al., GCN 41249; Xin et al., GCN 41250; Zheng et al., GCN 41251) in the near-infrared with the Palomar 1-m telescope, equipped with the 1-square degree WINTER camera (Lourie et al. 2020, Frostig et al. 2024). Observations started on 2025-08-06 at 08:16:51 UT (18.62 min after the trigger) and consisted of 15 exposures of 120 s in the J-band. In the stacked image, we do not detect any new source at the X-ray afterglow position reported by Xie et al., GCN 41243 and Campana et al., GCN 41249 down to the following 3-sigma AB magnitude: J > 19.7 The images were processed using the WINTER data reduction pipeline implemented with mirar (https://github.com/winter-telescope/mirar, https://doi.org/10.5281/zenodo.13352565). The photometric calibration was performed using nearby stars from the 2MASS catalog and the magnitude is not corrected for Galactic extinction. WINTER (Wide-field INfrared Transient ExploreR) is a partnership between MIT and Caltech, housed at Palomar Observatory, and funded by NSF MRI, NSF AAG, the David and Lucile Packard Foundation, and the MIT Kavli Institute for Astrophysics and Space Research. View this GCN Circular online at https://gcn.nasa.gov/circulars/41253. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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