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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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[vsnet-grb-info 40892] GRB 251121B: Fermi GBM Final Localization
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42823 SUBJECT: GRB 251121B: Fermi GBM Final Localization DATE: 25/11/24 16:55:01 GMT FROM: atrigg2(a)lsu.edu The Fermi GBM team reports the detection of a likely SHORT GRB "At 23:44:26.90 UT on 22 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251121B (trigger 785547871/251122989). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 336.52, Dec = -55.63 (J2000 degrees, equivalent to J2000 22h 26m, -55d 38'), with a statistical uncertainty of 10.74 degrees. The angle from the Fermi LAT boresight is 36.00 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251122989/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251122989/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2025/bn251122989/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/42823. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40891] EP251118A: 6 GHz VLA Detection
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42822 SUBJECT: EP251118A: 6 GHz VLA Detection DATE: 25/11/24 15:40:05 GMT FROM: muskan.yadav(a)students.uniroma2.eu Muskan Yadav, Roberto Ricci, Eleonora Troja (U Rome) report: We observed the position of EP251118A (Jiang et al., GCN 42749; Malesani et al., GCN 42751) with the Karl G. Jansky Very Large Array (VLA) on 2025 November 20, starting at 13:52 UT (~1.88 days after the EP/WXT trigger), at a central frequency of 6 GHz. In our preliminary analysis, we detect a radio counterpart at 6 GHz with a flux density of ∼74 μJy. The position is consistent with the optical counterpart (An et al., GCN 42756; Belkin et al., GCN 42758; Yadav et al., GCN 42760; Busmann et al., GCN 42763; Francile et al., GCN 42767; Urquijo-Rodríguez et al., GCN 42773; Lee et al., GCN 42780; Li et al., GCN 42776; Liu et al., GCN 42793; Moskvitin et al., GCN 42785; Aryan et al., GCN 42798; Gupta et al., GCN 42787) and the X-ray counterpart (Shi et al., GCN 42754). We thank the VLA staff for rapidly executing these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/42822. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40890] Fermi GRB 251124a: Global MASTER-Net observations report
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42821 SUBJECT: Fermi GRB 251124a: Global MASTER-Net observations report DATE: 25/11/24 15:30:22 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-Kislovodsk robotic telescope [1] located in Russia (Lomonosov MSU, Kislovodsk Solar Station of Pulkovo observatory) started inspect of the Fermi GRB 251124a ( Fermi GBM team, GCN 42820) errorbox 5857 sec after notice time and 5878 sec after trigger time at 2025-11-24 14:36:01 UT, with upper limit up to 13.0 mag. Observations started at twilight. The observations began at zenith distance = 62 deg. The sun altitude is -10.2 deg. The galactic latitude b = 29 deg., longitude l = 38 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3050796 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 5938 | 2025-11-24 14:36:01 | MASTER-Kislovodsk | (17h 11m 31.23s , +16d 54m 33.8s) | P- | 120 | 12.6 | 6078 | 2025-11-24 14:38:21 | MASTER-Kislovodsk | (17h 11m 31.15s , +16d 54m 22.6s) | P- | 120 | 12.5 | 6218 | 2025-11-24 14:40:41 | MASTER-Kislovodsk | (17h 11m 32.20s , +17d 16m 49.8s) | P| | 120 | 12.2 | 6218 | 2025-11-24 14:40:41 | MASTER-Kislovodsk | (17h 11m 31.11s , +16d 54m 13.1s) | P- | 120 | 13.0 | 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/42821. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40889] GRB 251124a: Fermi GBM Final Localization
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42820 SUBJECT: GRB 251124a: Fermi GBM Final Localization DATE: 25/11/24 15:09:47 GMT FROM: Andreas von Kienlin at MPE <azk(a)mpe.mpg.de> The Fermi GBM team reports the detection of a LONG GRB "At 12:58:03.47 UT on 24 November 2025, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 251124a (trigger 785681888/251124540). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 258.14, Dec = 16.86 (J2000 degrees, equivalent to J2000 17h 12m, +16d 51'), with a statistical uncertainty of 1.00 degrees. The angle from the Fermi LAT boresight is 63 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/42820. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40888] LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42819 SUBJECT: LIGO/Virgo/KAGRA S251105aj: SVOM/VT optical observations and preliminary results on SVOM J2320.0-2901 DATE: 25/11/24 15:06:20 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, H. L. Li, L. P. Xin, Z. H. Yao, Y. L. Qiu, C. Wu, X. H. Han, 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. Yang, O. Godet, J.-L. Atteia, M. Brunet, S. Guillot (IRAP), M. Pillas (IAP) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of the high-energy transient SVOM J2320.0-2901 detected by SVOM/ECLAIRs (Yang et al., GCN 42797), right after S251105aj reported by LIGO/Virgo/KAGRA (The LIGO-Virgo-Kagra Collaboration, GCN 42587; GCN 42616). The observation began at 2025-11-16T00:47:45 UT, 10.5 days after SVOM/ECLAIRs detection, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The VT field of view covered 96% of the 90% C.L. ECLAIRs error region, but no uncataloged sources were detected within the error box of ECL. VT also covered three EP/FXT sources (source#1: RA, Dec = 349.8643, -29.0602 deg; source#2: 350.1419, -29.0148 deg; source#3: 349.9737, -28.8522 deg) reported by Guillot et al. (GCN 42818). None of the known sources became apparent brighter within errorbox of three FXT candidates compared with Legacy Survey DR10. The 3 sigma upper limit was VT_R > 23.6 mag and VT_B > 23.8 mag with the exposure time of 65*70 sec. Further analysis is ongoing. 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/42819. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40887] LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42818 SUBJECT: LIGO/Virgo/KAGRA S251105aj: EP-FXT follow-up observations and preliminary results on SVOM J2320.0-2901 DATE: 25/11/24 15:05:57 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S. Guillot, H. Yang, O. Godet, J.-L. Atteia (IRAP), M. Pillas (IAP), L. P. Xin, Y. N. Ma, H. W. Pan, T. Zhao (NAOC), Y. J. Yi, A. Li (BNU), R. X. Hu (WHU), D. Z. Du (ZJU), C. Y. Wang (THU) on behalf of the Einstein Probe (EP) team: EP-FXT performed a Target of Opportunity observation of the high-energy transient SVOM J2320.0-2901 detected by SVOM/ECLAIRs (Yang et al., GCN 42797), in a search for possible counterparts of the compact binary merger candidate S251105aj (The LIGO-Virgo-Kagra Collaboration, GCN 42587). The observation was conducted at 2025-11-15T21:39:22 UTC with an exposure of 5 ks, about 10.36 days after the GW trigger and the detection time of SVOM J2320.0-2901. EP-FXT covered the full area of the 90% C.L. ECLAIRs error region and detected six sources above a SNR of 4.5 within 15 arcminutes from SVOM J2320.0-2901. Their information is summarized below (RA/Dec in degrees with 10" error radius (90% C.L.); fluxes are the observed ones in 0.5–10 keV): # | Name | RA | Dec | Flux (erg/s/cm^2) | SNR —---------------------------------------------------------------------------------------------------- 1 | EPF_J231927.4-290337 | 349.8643 | -29.0602 | 1.4e-13 | 4.7 2 | EPF_J232034.0-290053 | 350.1419 | -29.0148 | 2.2e-13 | 10.0 3 | EPF_J231953.7-285108 | 349.9737 | -28.8522 | 1.7e-13 | 5.7 4 | EPF_J231906.2-290806 | 349.7760 | -29.1351 | 3.4e-13 | 5.8 5 | EPF_J232051.4-285356 | 350.2140 | -28.8990 | 2.4e-13 | 8.4 6 | EPF_J232108.1-290032 | 350.2839 | -29.0088 | 2.6e-13 | 7.9 We cross-matched all six FXT detections against the SIMBAD, NED, and Vizier catalogues, using a 20″ matching radius (for a galaxy at 2000 Mpc, this corresponds to an offset of ~200 kpc). Five FXT detections (#2,3,4,5,6) are matched to five optical quasars correspondingly, with their redshifts in a range of 0.721 to 1.641, higher than z=0.374 estimated for the GW event. The remaining source (#1) is matched to a source from the KiDSDR4 QSOs photometric redshifts catalog (Nakoneczny et al., 2021), which is classified as a quasar with 68% probability and a photometric redshift of 0.5 +/- 1.2 based on machine learning estimates. We conducted SVOM/VT on this field with the results reported in GCN 42819. Further FXT observations of these candidates will be conducted. 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/42818. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 40886] EP251124a: GROWTH-India Telescope optical upper limits
by GCN Circulars 24 Nov '25

24 Nov '25

TITLE: GCN CIRCULAR NUMBER: 42817 SUBJECT: EP251124a: GROWTH-India Telescope optical upper limits DATE: 25/11/24 15:02:41 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> T. Mohan (IITB), S. Patil (IITB), D. Eappachen (IIA), V.Swain (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP transient (Zhou et al., GCN 42816), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2025-11-24T13:25:59 UT, i.e., about 2.27 hours after the EP-WXT trigger. Two exposures were obtained each in r' and g' filters. We did not detect any transient in our images within the WXT localization region and at the position of FXT sources - FXTA, FXTB1, and FXTB2. The photometric upper limits are as follows: | MJD (mid) | Filter | tmid-t0 (min) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | ------------- | ------------------- | ---------------- | | 61003.55971 | r' | 135.9 | 300 | 20.5 | | 61003.56539 | g' | 144.1 | 300 | 20.8 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. The GROWTH India Telescope (GIT; Kumar et al. 2022) is a 70-cm telescope with a 0.7-degree field of view, set up by the Indian Institute of Astrophysics (IIA) and the Indian Institute of Technology Bombay (IITB) with funding from DST-SERB and IUSSTF. It is located at the Indian Astronomical Observatory (Hanle), operated by IIA. We acknowledge funding by the IITB alumni batch of 1994, which partially supports the operations of the telescope. Telescope technical details are available at https://sites.google.com/view/growthindia/. View this GCN Circular online at https://gcn.nasa.gov/circulars/42817. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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