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

[vsnet-grb-info 40902] EP251124a: Xinglong GWAC-F60A optical observation
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42833 SUBJECT: EP251124a: Xinglong GWAC-F60A optical observation DATE: 25/11/25 09:48:40 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, J. Wang, X. H. Han, P. P. Zhang, H. L. Li, Z. H. Yao, J. Y. Wei (NAOC) report on behalf of SVOM follow-up team: We observed the field of EP251124a triggered by EP/WXT (Zhou et al., GCN 42816; GCN 42832) using the GWAC-F60A telescope located at Xinglong observatory, China. We obtained a series of frames in R-band, starting at 2025-11-24T11:22:30 UTC, about 12.42 minutes after the trigger. No uncataloged sources were detected in our single or stacked images within the error box provided by EP/FXT (Zhou et al., GCN 42816) and Swift/XRT (Evans et al., GCN 42827), the three sigma limit is: mid-time | exposure time | band | upper limit ----------- -|-----------------|-------|------------- 19.5 minutes | 10*50 sec | R | 19.5 mag None of the known sources showed significant brightness variations within EP/FXT and Swift/XRT errorbox compared with USNO-B1.0 catalog. Our results are consistent with GIT (Mohan et al., GCN 42817), Kinder (Wang et al., GCN 42824), MASTER (Lipunov et al., GCN 42828), and NOT (van Hoof et al., GCN 42829). Our photometry was not corrected for Galactic extinction. We thank the staff at Xinglong observatory for their excellent support. View this GCN Circular online at https://gcn.nasa.gov/circulars/42833. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40901] EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42832 SUBJECT: EP251124a (EP-WXT trigger 01709248862) is triggered by the known source AWM 7 DATE: 25/11/25 09:23:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H.Zhou (PMO, CAS), J.-Y. Cao (IHEP), H.-N. Yang, and Z.-X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: Refined analysis of the WXT data shows that EP251124a (GCN #42816) is associated with the Cluster of Galaxies AWM 7. The estimated flux is ~6.17e-11 erg/cm2/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/42832. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40900] Fermi GRB 251125A: Global MASTER-Net observations report
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42831 SUBJECT: Fermi GRB 251125A: Global MASTER-Net observations report DATE: 25/11/25 01:15:21 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251125A ( Fermi GBM team, GCN 42830) errorbox 29 sec after notice time and 35 sec after trigger time at 2025-11-25 01:00:14 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 58 deg. The sun altitude is -35.2 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 251125A errorbox 58 sec after notice time and 64 sec after trigger time at 2025-11-25 01:00:43 UT, with upper limit up to 19.3 mag. The observations began at zenith distance = 65 deg. The sun altitude is -25.5 deg. The galactic latitude b = 44 deg., longitude l = 259 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3051146 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 40 | 2025-11-25 01:00:14 | MASTER-Kislovodsk | (10h 47m 41.84s , -02d 16m 18.0s) | C | 10 | 16.6 | 69 | 2025-11-25 01:00:43 | MASTER-SAAO | (10h 46m 14.24s , -02d 25m 57.0s) | C | 10 | 17.6 | 69 | 2025-11-25 01:00:43 | MASTER-SAAO | (10h 48m 05.24s , -02d 41m 35.6s) | C | 10 | 17.7 | 70 | 2025-11-25 01:00:44 | MASTER-Kislovodsk | (10h 47m 41.88s , -02d 16m 25.2s) | C | 10 | 16.7 | 103 | 2025-11-25 01:01:12 | MASTER-SAAO | (10h 46m 14.21s , -02d 25m 59.4s) | C | 20 | 18.1 | 103 | 2025-11-25 01:01:12 | MASTER-SAAO | (10h 48m 05.20s , -02d 41m 35.0s) | C | 20 | 18.5 | 106 | 2025-11-25 01:01:14 | MASTER-Kislovodsk | (10h 47m 41.94s , -02d 16m 40.7s) | C | 20 | 17.2 | 147 | 2025-11-25 01:01:51 | MASTER-SAAO | (10h 46m 14.28s , -02d 25m 58.7s) | C | 30 | 18.5 | 147 | 2025-11-25 01:01:51 | MASTER-SAAO | (10h 48m 05.23s , -02d 41m 33.9s) | C | 30 | 18.8 | 146 | 2025-11-25 01:01:54 | MASTER-Kislovodsk | (10h 47m 41.97s , -02d 16m 43.6s) | C | 20 | 17.2 | 181 | 2025-11-25 01:01:54 | MASTER-Kislovodsk | (10h 47m 41.96s , -02d 16m 43.7s) | C | 90 | 18.2 | Coadd 195 | 2025-11-25 01:02:38 | MASTER-Kislovodsk | (10h 47m 41.94s , -02d 16m 44.6s) | C | 30 | 17.5 | 201 | 2025-11-25 01:02:40 | MASTER-SAAO | (10h 46m 14.26s , -02d 25m 58.4s) | C | 40 | 18.8 | 201 | 2025-11-25 01:02:40 | MASTER-SAAO | (10h 48m 05.20s , -02d 41m 33.1s) | C | 40 | 18.9 | 250 | 2025-11-25 01:03:28 | MASTER-Kislovodsk | (10h 47m 41.92s , -02d 16m 45.1s) | C | 40 | 17.8 | 265 | 2025-11-25 01:03:39 | MASTER-SAAO | (10h 46m 14.24s , -02d 25m 58.5s) | C | 50 | 18.9 | 265 | 2025-11-25 01:03:39 | MASTER-SAAO | (10h 48m 05.17s , -02d 41m 32.9s) | C | 50 | 19.0 | 315 | 2025-11-25 01:04:28 | MASTER-Kislovodsk | (10h 47m 41.90s , -02d 16m 45.0s) | C | 50 | 17.8 | 315 | 2025-11-25 01:04:28 | MASTER-Kislovodsk | (10h 52m 01.99s , -02d 40m 47.8s) | C | 50 | 12.0 | 340 | 2025-11-25 01:04:48 | MASTER-SAAO | (10h 46m 14.20s , -02d 25m 58.8s) | C | 60 | 19.1 | 340 | 2025-11-25 01:04:48 | MASTER-SAAO | (10h 48m 05.12s , -02d 41m 32.9s) | C | 60 | 19.3 | 395 | 2025-11-25 01:05:38 | MASTER-Kislovodsk | (10h 47m 41.86s , -02d 16m 44.4s) | C | 70 | 18.1 | 480 | 2025-11-25 01:07:08 | MASTER-Kislovodsk | (10h 51m 53.78s , -02d 19m 53.0s) | C | 60 | 17.8 | 560 | 2025-11-25 01:08:28 | MASTER-Kislovodsk | (10h 51m 23.73s , -00d 26m 51.2s) | C | 60 | 18.0 | 639 | 2025-11-25 01:09:48 | MASTER-Kislovodsk | (10h 36m 38.70s , -02d 21m 11.9s) | C | 60 | 17.0 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [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 View this GCN Circular online at https://gcn.nasa.gov/circulars/42831. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40899] GRB 251125A: Fermi GBM Final Real-time Localization
by GCN Circulars 25 Nov '25

25 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42830 SUBJECT: GRB 251125A: Fermi GBM Final Real-time Localization DATE: 25/11/25 01:09:58 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 00:59:38 UT on 25 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251125A (trigger 785725183.783164 / 251125041). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 161.9, Dec = -7.6 (J2000 degrees, equivalent to J2000 10h 47m, -7d 35'), with a statistical uncertainty of 7.6 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/bn251125041/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251125041/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42830. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40898] EP251124a: NOT r- and z-band optical upper limits
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42829 SUBJECT: EP251124a: NOT r- and z-band optical upper limits DATE: 25/11/24 23:32:52 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> A. P. C. van Hoof (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. N. D. van Dalen (Radboud), P. G. Jonker (Radboud), Shilpa Bijavara Seshashayana (NOT and Malmo Univ.), report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP251124a (Zhou et al., GCN 42816) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations were obtained in the r (3x300 s) and z (3x200 s) bands, starting on 2025-11-24 at 21:34:32 UTC (10.4 hr after the WXT trigger). No new source is detected within any of the X-ray error circles provided by EP/FXT (Zhou et al., GCN 42816) and Swift/XRT (Evans et al., GCN 42827). From the stacked images we obtain the following 3-sigma upper limits: r > 24.4 z > 23.0 These upper limits are in AB magnitudes and were calibrated using nearby stars from the Pan-STARRS catalog and are not corrected for Galactic extinction. The upper limits are consistent with previously reported upper limits in r-band (Mohan et al., GCN 42817; Wang et al., GCN 42824). View this GCN Circular online at https://gcn.nasa.gov/circulars/42829. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40897] EP251124a: Global MASTER-Net observations report
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42828 SUBJECT: EP251124a: Global MASTER-Net observations report DATE: 25/11/24 21:09:29 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) was pointed to the EP251124a ( EP Team et al., GCN 42816) errorbox 21097 sec after notice time and 28845 sec after trigger time at 2025-11-24 19:10:50 UT, with upper limit up to 18.2 mag. The observations began at zenith distance = 7 deg. The sun altitude is -58.5 deg. The galactic latitude b = -15 deg., longitude l = 147 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3050758 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 28935 | 2025-11-24 19:10:50 | MASTER-Kislovodsk | (02h 53m 11.63s , +41d 55m 39.9s) | C | 180 | 18.2 | 28935 | 2025-11-24 19:10:50 | MASTER-Kislovodsk | (02h 53m 47.32s , +41d 32m 52.8s) | C | 180 | 12.7 | Filter C is a clear (unfiltred) band. The observation and reduction will continue. The message may be cited. [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 View this GCN Circular online at https://gcn.nasa.gov/circulars/42828. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40896] EP251124a: Swift-XRT observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42827 SUBJECT: EP251124a: Swift-XRT observations DATE: 25/11/24 17:36:48 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 EP251124a, collecting 2.5 ks of Photon Counting (PC) mode data between T0+5.1 ks and T0+11 ks after the trigger. The field is full of extended emission due to a cluster of galaxies. We have detected 3 sources. These have been automatically classified as follows: * 0 likely counterparts * 0 candidate counterparts * 3 uncatalogued X-ray sources * 0 known X-ray sources Uncatalogued X-ray sources -------------------------- Source 2 (SWIFT J025449.9+413724): ================================== RA (J2000.0): 43.7081 = 02 54 49.94 Dec (J2000.0): +41.6234 = +41 37 24.2 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: GOOD Distance: 3.0 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-2.1 +/- -2.1)e-11 erg cm^-2 s^-1 Peak rate: (8.5 [+3.4, -3.0])e-3 ct s^-1 Peak flux: (1.80 [+0.71, -0.63])e-13 erg cm^-2 s^-1 ECF: 2.12e-11 erg cm^-2 ct^-1 assuming NH=2.22e+22 cm^-2, gamma=5.93 determined from a spectral fit. LSXPS UL: 1.0e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. A SIMBAD object `2MASX J02544959+4137278' is 5.1" away. There is 1 2MASS object within the source's 3-sigma error radius. Source 3 (SWIFT J025510.5+413444): ================================== RA (J2000.0): 43.7940 = 02 55 10.56 Dec (J2000.0): +41.5789 = +41 34 44.0 Error: 5.7 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.8 arcmin from the Einstein Probe/WXT position. Mean rate: (-1.0 +/- -1.0)e0 ct s^-1 Mean flux: (-1.6 +/- -1.6)e-10 erg cm^-2 s^-1 Peak rate: (3.8 [+2.5, -2.2])e-3 ct s^-1 Peak flux: (6.0 [+4.0, -3.4])e-13 erg cm^-2 s^-1 ECF: 1.57e-10 erg cm^-2 ct^-1 assuming NH=2.84e+21 cm^-2, gamma=0.31 determined from a spectral fit. LSXPS UL: 1.6e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. Source 6 (SWIFT J025445.0+413429): ================================== RA (J2000.0): 43.6876 = 02 54 45.02 Dec (J2000.0): +41.5749 = +41 34 29.6 Error: 5.4 (arcsec, radius, 90% confidence). Detect flag: POOR Distance: 2.0 arcmin from the Einstein Probe/WXT position. Mean rate: 0.0245 [+0.0084, -0.0071] ct s^-1 Mean flux: (8.9 [+3.1, -2.6])e-13 erg cm^-2 s^-1 Peak rate: 0.043 [+0.022, -0.018] ct s^-1 Peak flux: (1.56 [+0.81, -0.66])e-12 erg cm^-2 s^-1 ECF: 3.63e-11 erg cm^-2 ct^-1 assuming NH=1.20e+21 cm^-2, gamma=1.87 determined from a spectral fit. LSXPS UL: 3.2e-02 ct/sec, (0.3-10 keV) so the source is not above this 3-sigma upper limit. There is no evidence for fading. 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/EP_FIELD00083. This circular is an official product of the Swift-XRT team. View this GCN Circular online at https://gcn.nasa.gov/circulars/42827. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40895] GRB 251124b: Fermi GBM Final Real-time Localization
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42826 SUBJECT: GRB 251124b: Fermi GBM Final Real-time Localization DATE: 25/11/24 17:34:45 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 12:58:03 UT on 24 Nov 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251124b (trigger 785681888.46989 / 251124540). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 262.1, Dec = 18.4 (J2000 degrees, equivalent to J2000 17h 28m, 18d 23'), with a statistical uncertainty of 13.1 degrees. The angle from the Fermi LAT boresight is 52.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251124540/… View this GCN Circular online at https://gcn.nasa.gov/circulars/42826. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40894] LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42825 SUBJECT: LIGO/Virgo/KAGRA S251112cm: AT 2025adht Kinder follow-up observations DATE: 25/11/24 17:22:31 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> J. H. Gillanders (Oxford), A. Aryan, T.-W. Chen, Y.-H. Lee, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), S. J. Smartt (Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, W.-J. Hou, H.-C. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), S. Yang, Z. N. Wang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: Here we report follow-up observations of the candidate optical counterpart AT 2025adht (first reported by Franz et al., GCN 42675; see also Anand et al., GCN 42677; Burkhonov et al., GCN 42798) to the LIGO-Virgo-KAGRA (LVK) gravitational-wave event S251112cm (LVK Collaboration, GCN 42650). We observed AT 2025adht utilizing the 1m LOT at Lulin Observatory in Taiwan, as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first LOT epoch of observations began at 20:31 UTC on November 21, 2025 (MJD 61000.855), 9.225 days after the GW trigger. The second LOT epoch began at 20:16 UTC, or MJD 61001.845, 10.207 days after the GW trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We utilized the Python-based package AutoPhOT (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 images using the 'hotpants' (Becker 2015, ascl.soft. ascl:1504.004) algorithm. Moreover, we further utilized AutoPhOT to perform PSF photometry. The details of the observations and the measured magnitudes (in the AB system) are as follows: Telescope | Filter | MJD (start) | t - t0 (d) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass LOT | r | 61000.855 | 9.225 | 300 * 6 | 21.83 +/- 0.06 | 1".2 | 1.41 LOT | r | 61001.845 | 10.207 | 300 * 6 | 21.86 +/- 0.08 | 1".2 | 1.46 Burkhonov et al. (GCN 42698) report a (PS1-equivalent) r-band magnitude of 21.64 +/- 0.1 on MJD 60994.009 (2.37 days post-GW trigger). Our observations indicate that AT 2025adht has faded only slightly in the ~week since detection. The slow evolution indicates that AT 2025adht is not some rapidly declining kilonova-like transient; we instead suspect that AT 2025adht is a background supernova near peak, hence the slow evolution. This interpretation is supported by the Legacy Survey's host galaxy phot-z estimate (0.139 +/- 0.033; see also Anand et al., GCN 42677). The presented magnitudes are calibrated using field stars from the ATLAS-RefCat2 catalog from MAST (Tonry et al. 2018, ApJ, 867, 105) and are not corrected for the expected Galactic foreground extinction of A_r = 0.06 mag in the direction of the transient (Schlafly & Finkbeiner 2011). The methodology and details on the capabilities of Lulin observatory telescopes can be found in Aryan et al. 2025, ApJS, 281, 20. doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/42825. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40893] EP251124a: Optical upper limit with Kinder observations
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42824 SUBJECT: EP251124a: Optical upper limit with Kinder observations DATE: 25/11/24 17:15:34 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> Z. N. Wang (HNAS), A. Aryan, T.-W. Chen, W.-J. Hou, Y.-H. Lee (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), A. Sankar.K, Y.-C. Pan, C.-C. Ngeow, M.-H. Lee, C.-H. Lai, H.-C. Lin, C.-S. Lin, H.-Y. Hsiao, J.-K. Guo (all NCU), S. Yang, L. L. Fan, G. H. Sun (all HNAS), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, T. Moore, K. W. Smith, C. Angus, A. Aamer (all QUB), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the fast X-ray transient EP251124a (Zhou et al., GCN 42816) using the 40cm SLT at Lulin Observatory in Taiwan as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). Our SLT observation started at 16:21 UTC on the 24th of November 2025 (MJD 61003.477), 0.27 hr after the EP-WXT trigger. We utilized the astroalign (Beroiz et al. 2020, A&C, 32, 100384) and astropy (Astropy Collaboration et al. 2022, ApJ, 935, 167) packages to align and stack the individual frames. We utilised the Python-based package AutoPhOT (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the Pan-STARRS1 3Pi archive image (Chambers et al. 2016, arXiv:1612.05560) using the 'hotpants' (Becker 2015, ascl.soft. ascl:1504.004) algorithm. In the difference image, we do not detect any uncataloged sources within the 20" error circle, for each of the three EP-FXT positions reported. We note that the position of FXTB-2 is not covered by Pan-STARRS1. Although this field is included in SDSS DR14 (Abolfathi et al. 2018, arXiv:1707.09322), we do not find any new or uncataloged sources by eye within the 20″ error circle of FXTB-2. Moreover, we further utilized AutoPhOT to perform the PSF photometry. The details of the observations and the 3-sigma upper limit (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61003.477 | 0.27 | 300 * 24 | >21.7 | 1".40 | 1.19 The presented magnitude is calibrated using the field stars from the ATLAS-RefCat2 catalog from MAST (Tonry et al. 2018, ApJ, 867, 105) and is not corrected for the expected Galactic foreground extinction of A_r = 0.27 mag in the direction of the transient (Schlafly & Finkbeiner 2011). Our observation agrees with Mohan et al. (GCN 42817) and provides a deeper constraint. The methodology, details on the Lulin observatory telescopes, and a compilation of our optical follow-up campaign for FXTs discovered within the first year of operation of the Einstein-Probe mission can be found in Aryan et al. 2025, ApJS, 281, 20. doi:10.3847/1538-4365/adfc69. View this GCN Circular online at https://gcn.nasa.gov/circulars/42824. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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