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[vsnet-grb-info 41871] EP260214a: Optical upper limits with Kinder observations
by GCN Circulars 16 Feb '26

16 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43761 SUBJECT: EP260214a: Optical upper limits with Kinder observations DATE: 26/02/16 10:22:14 GMT FROM: Amar Aryan at National Central University, Institute of Astronomy (NCUIA) <amararyan941(a)gmail.com> A. Aryan, C.-S. Lin, T.-W. Chen (all NCU), A. K. H. Kong (NTHU), J. H. Gillanders, S. J. Smartt (both Oxford), Y. J. Yang (NYUAD), Y.-H. Lee, A. Sankar.K, M.-H. Lee, C.-H. Lai, Y.-C. Pan, C.-C. Ngeow, W.-J. Hou, H.-Y. Hsiao, H.-C. Lin, 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: We observed the field of the fast X-ray transient EP260214a (Li et al., GCN 43742 & GCN 43751) using the 40cm SLT at the Lulin observatory, as part of the Kinder collaboration (Chen & Yang et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The FXT was found to be coincident with GRB 260214A (Ravasio et al., GCN 43759). The first SLT epoch of observations in r-band started at 20:46 UTC on 14th of February 2026 (MJD 61085.865), 0.13 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 used the Python-based AutoPhOT package (Brennan & Fraser 2022, A&A, 667, A62) to perform template subtraction with the DESI Legacy Survey (Dey et al. 2019, AJ 157, 168) DR10 image using the 'SFFT' (Hu et al. 2022, ApJ, 936, 157) algorithm. Either in the stacked frame or in the difference image, we do not detect any new or uncataloged sources within the 10" refined EP-FXT localization circle (Li et al. GCN 43751). Moreover, we used AutoPhOT to perform PSF photometry. The details of the observations and the measured 3-sigma upper limits (in the AB system) are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude | avg. Seeing | med. Airmass SLT | r | 61085.865 | 0.13 | 300 * 6 | >20.6 | 2".62 | 1.79 The non-detection in our observations is consistent with those reported by Lipunov et al. (GCN 43743), Li et al. (GCN 43746), Watson et al. (GCN 43753), and He et al. (GCN 43754). The presented magnitude is calibrated using the field stars from the Pan-Starrs catalog and is not corrected for the expected Galactic foreground extinction of A_r = 0.16 mag in the direction of the transient (Schlafly & Finkbeiner 2011). 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 are presented 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/43761. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41870] EP260214b: EP-FXT follow-up observation
by GCN Circulars 16 Feb '26

16 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43760 SUBJECT: EP260214b: EP-FXT follow-up observation DATE: 26/02/16 05:59:28 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> J. Yang (ZZU), A. Li (BNU), Y. H. Jiang (NJU), Y. Liu (NAOC) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260214b was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Yang et al., GCN 43744), whose optical counterpart was detected by several optical telescopes (He et al., GCN 43745, Watson et al., GCN 43747, Pérez-Fournon et al., GCN 43750, Russeil et al., GCN 43752, Li et al., GCN 43755, Becerra et al., GCN 43758) at a resdhift z = 1.208 (Le Floch et al., GCN 43749). EP-FXT performed a follow-up observation of EP260214b about 5.8 hours after the WXT detection, with an exposure time of 2.8 ks. The FXT telemetry data shows that an uncatalogued source was detected within the WXT error circle at R.A. = 191.2581, DEC = 23.8529 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT X-ray spectrum of this uncatalogued source can be fitted with an absorbed powerlaw with a hydrogen column density fixed at the Galactic value of 1.57 x 10^20 cm^-2 and a photon index of 2.2 (+0.3/-0.3). The derived unabsorbed 0.5-10 keV flux is approximately 2.8 (+0.7/-0.5) x 10^-13 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/43760. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41869] EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43759 SUBJECT: EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection DATE: 26/02/15 20:20:37 GMT FROM: mariaedvige.ravasio(a)ru.nl M. E. Ravasio (Radboud Univ.), P.G. Jonker (Radboud Univ.) and E. Burns (LSU), R. Hamburg (USRA) report on behalf of the Fermi-GBM Team: Fermi-GBM had full spatial and temporal coverage of the transient EP260214a detected by EP-WXT (Li et al., GCN 43742, Li et al., GCN 43751). There was no Fermi-GBM onboard trigger around the EP refined starting time T0=2026-02-14T20:37:00 (UTC). The GBM Targeted Search [1], the most sensitive, coherent search for GRB-like signals, was run in the time interval [-50;+500] s from the EP T0. A weak transient signal was found most significantly at ~T0+35 s on a 16 s timescale, with a false alarm rate of 2.27e-04 Hz. The localisation is consistent with the EP one, with a spatial association probability of 87.4%. Among the three spectral templates tested, the transient was best-fit with a "soft" spectrum (i.e., a Band function with Epeak = 70 keV, alpha = -1.9, beta = -3.7) for a GRB. [1] Goldstein et al. 2019 arXiv:1903.12597 View this GCN Circular online at https://gcn.nasa.gov/circulars/43759. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41868] EP260214b: DDOTI Optical Detection
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43758 SUBJECT: EP260214b: DDOTI Optical Detection DATE: 26/02/15 20:17:14 GMT FROM: Rosa L. Becerra at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Nat Butler (ASU), Simone Dichiara (Penn State University), Tsvetelina Dimitrova (ASU), Alexander Kutyrev (GSFC/UMD), William H. Lee (UNAM), Océlotl López (UNAM), Margarita Pereyra (UNAM) and Eleonora Troja (U Roma) report: We observe the field of EP260214b (Yang et al., GCN Circ. 43744) with the DDOTI/OAN wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir (http://ddoti.astroscu.unam.mx) on the night of 2026-02-15 UTC. DDOTI observed from 05:32 UTC to 13:08 UTC (T+8.9 h to T+16.5 h after the trigger), with a total exposure time of 3.7 hours. These observations were interleaved with other scientific programs. Comparing our observations to the USNO-B1 and Pan-STARRS PS1 DR2 catalogues, we detect the optical counterpart reported by He et al. (GCN Circ. 43745), at preliminary AB magnitude of: w = 21.08 +/- 0.23. This value is consistent with previous observations reported (He et al., GCN Circ. 43745; Watson et al., GCN Circ. 43747; Pérez-Fournon et al., GCN Circ. 43750; Russeil et al., GCN Circ. 43752; Li et al., GCN Circ. 43755; Vijaykumar et al., GCN Circ. 43757) and is not corrected for the Galactic extinction. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/43758. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41867] EP260214b: GROWTH-India Telescope optical upper limit
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43757 SUBJECT: EP260214b: GROWTH-India Telescope optical upper limit DATE: 26/02/15 18:57:19 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> V. Vijaykumar, A. Khade, V. Swain, S. Patil, A.P. Saikia, T. Mohan, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and K. Angail (IAO) report on behalf of the GIT team: We observed the field of EP260214b detected by the Einstein Probe (EP) mission (EP mission, GCN 43744), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-02-15 16:28:03 (UTC), i.e., 18.40 hours after the trigger and obtained a single exposure in r' filter. We did not detect any transient in our image. The photometric upper limit is as follows: | MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | --------------- | ------------------- | ---------------- | | 61086.68614 | r' | 18.40 | 650 | 20.9 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our magnitude is consistent with other optical observations (He. et al., GCN 43745; Watson et.al., GCN 43747; Pérez-Fournon et.al GCN 43750; Russeil et.al GCN 43752; Li et.al GCN 43755). 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/43757. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41866] EP250214a: VLT near-infrared observation
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43756 SUBJECT: EP250214a: VLT near-infrared observation DATE: 26/02/15 18:04:57 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva(a)uniroma1.it> Niccolò Passaleva, Massine El Kabir, Narges Shahamat, Eleonora Troja (U Rome) on behalf of the ERC BHianca team: We observed the field of EP260214a (Li et al., GCN 43742) with the HAWKI imager on the ESO VLT UT4 (Yepun). Observations began at ~11.9 hr after the EP/WXT trigger and were carried out at an average airmass of about 1.0 in the J filter. Several extended sources are visible close to or within the EP/FXT error region (Li et al., GCN 43751), however no uncatalogued source is clearly identified in our observations down to a 3 sigma limiting magnitude J~25 AB mag calibrated using nearby stars in the 2MASS Catalogue (Skrutskie et al. 2006) and not corrected for Galactic extinction. We thank the staff at the VLT, for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43756. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41865] EP250214a: VLT near-infrared observation
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43756 SUBJECT: EP250214a: VLT near-infrared observation DATE: 26/02/15 18:04:57 GMT FROM: N. Passaleva at Sapienza University of Rome <niccolo.passaleva(a)uniroma1.it> Niccolò Passaleva, Massine El Kabir, Narges Shahamat, Eleonora Troja (U Rome) on behalf of the ERC BHianca team: We observed the field of EP260214a (Li et al., GCN 43742) with the HAWKI imager on the ESO VLT UT4 (Yepun). Observations began at ~11.9 hr after the EP/WXT trigger and were carried out at an average airmass of about 1.0 in the J filter. Several extended sources are visible close to or within the EP/FXT error region (Li et al., GCN 43751), however no uncatalogued source is clearly identified in our observations down to a 3 sigma limiting magnitude J~25 AB mag calibrated using nearby stars in the 2MASS Catalogue (Skrutskie et al. 2006) and not corrected for Galactic extinction. We thank the staff at the VLT, for the rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/43756. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41864] EP260214b: SVOM/VT optical observation
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43755 SUBJECT: EP260214b: SVOM/VT optical observation DATE: 26/02/15 16:46:31 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, X. H. Han, Y. Xu, J. Wang, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. R. Xu, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of EP260214b detected by Einstein Probe (Yang et al., GCN 43744). The observation started on 2026-02-15T03:52:22 UTC, i.e. 5.81 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. The optical counterpart (He et al., GCN 43745; Watson et al., GCN 43747; Le Floch et al., GCN 43749; Pérez-Fournon et al., GCN 43750; Russeil et al., GCN 43752) were detected in both channels. The measurements in AB magnitude are derived as follows: Mid time | Band | Exposure Time | 3 sigma limit magnitude 6.93 hours VT_B 80*50 sec 21.29 +/-0.08 mag 6.94 hours VT_R 67*50 sec 20.84 +/- 0.07 mag The counterpart show no significant variation during our observation from 5.81 hours to 8.08 hours. Our photometry was 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/43755. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41863] EP260214a: NOT optical upper limits
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43754 SUBJECT: EP260214a: NOT optical upper limits DATE: 26/02/15 15:07:18 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He (NAOC), S.Y. Fu (HUST), J. An, X. Liu, S.Q. Jiang, Z.P. Zhu, D. Xu (NAOC), J.P.U. Fynbo (DAWN/NBI), K. Valeckas (NOT) report on behalf of a large collaboration: We observed the field of EP260214a (Li et al., GCN 43742) using the 2.56-m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observations started at 03:39:29.978 UT on 2026-02-15, i.e., 7.02 hrs after the EP trigger, and we obtained 3x300 s frames in the Sloan r-band and 5 x 200 s frames in the Sloan z- band. No new optical source is detected within the EP/FXT error circle (Li et al., GCN 43751), down to 5-sigma upper limits of r ~ 23.1 and z ~ 21.8, calibrated with nearby Pan-STARRS stars and not corrected for Galactic extinction. These upper limits are consistent with the ones previously reported (Li et al., GCN 43746; Watson et al. GCN 43753). View this GCN Circular online at https://gcn.nasa.gov/circulars/43754. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41862] EP260214a: COLIBRÍ optical upper limits
by GCN Circulars 15 Feb '26

15 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43753 SUBJECT: EP260214a: COLIBRÍ optical upper limits DATE: 26/02/15 14:43:58 GMT FROM: Rosa L. Becerra at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Alan M. Watson (UNAM), Damien Dornic (CPPM), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of EP260214a (Li et al., GCN Circ. 43742) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-15 10:20 to 11:32 UTC (from 13.70 to 14.92 hours after the trigger) and obtained 53 minutes of exposure, in r and z filters. The data were reduced, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR1 catalog, is in the AB system, and is not corrected for Galactic extinction. In the stacked images, we do not detect any new source at the refined FXT position (Li et al., GCN Circ. 43751) down to the following 3-sigma limits: r > 23.6 z > 22.2 These upper limits are consistent with the ones reported by SVOM/VT (Li et al. GCN Circ. 43746). 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/43753. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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