February 2026 - vsnet-grb-info - ooruri.kusastro.kyoto-u.ac.jp

[vsnet-grb-info 41919] EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43807 SUBJECT: EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate DATE: 26/02/22 19:53:08 GMT FROM: Rob Eyles-Ferris at U of Leicester <raje1(a)leicester.ac.uk> R. A. J. Eyles-Ferris and P. T. O’Brien (Leicester) report on behalf of a larger collaboration: We observed the field of EP260221a (Zhang et al., GCN 43791; Liu et al., GCN 43802) with the 2m Liverpool Telescope on La Palma using the IO:O instrument. We obtained 6x200s exposures in the SDSS i’ and 8x200s exposures in the SDSS z’ filters starting at 2026-02-22 00:47:58 UT, approximately 14.1 hours after the X-ray detection. Within the EP/FXT localisation (Liu et al., GCN 43802), we detect no new sources in our stacked images consistent with the results of Mandarakas et al. (GCN 43793), Kumar et al. (GCN 43794), He et al. (GCN 43798), Lipunov et al. (GCN 43803), and Levan et al. (GCN 43805). At the position of the candidate counterpart identified by Watson et al. (GCN 43806), we measure i’ = 22.21 +/- 0.12 and z’ = 22.29 +/- 0.18 with photometry calibrated to Pan-STARRS and not corrected for Galactic extinction. As pointed out by Watson et al. (GCN 43806), this is significantly brighter than the magnitudes catalogued in Legacy DR10 and suggests this could indeed be the counterpart of EP260221a. We derive 3-sigma upper limits of i’ > 23.4 and z’ > 23.0 for our stacked images. View this GCN Circular online at https://gcn.nasa.gov/circulars/43807. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41918] EP260221a: COLIBRÍ optical counterpart candidate
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43806 SUBJECT: EP260221a: COLIBRÍ optical counterpart candidate DATE: 26/02/22 17:22:21 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Antonio de Ugarte Postigo (LAM), Rosa L. Becerra (UNAM), Benjamin Schneider (LAM), Jean-Grégoire Ducoin (CPPM), 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), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Asuka Kuwata (UNAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), and Fredd Sánchez Álvarez (UNAM) report: We reobserved the field of the EP260221a (Zhang et al., GCN Circ. 43791) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-02-22 05:55 to 10:54 UTC (from 18.20 to 23.20 hours after the trigger) and obtained 71 minutes of simultaneous exposure in the r and z filters. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ ASU pipeline. The photometry was calibrated using nearby stars from the Pan-STARRS-DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. When we subtract the r-band image from our second epoch from the one from our first (Mandarakas et al., GCN Circ. 43793), we detect a residual source with a SNR of about 5 at: RA (J2000) = 11:55:01.22 = 178.7551 deg Dec (J2000) = -20:58:57.6 = -20.9827 deg The uncertainty on this position is 0.5 arcsec. The source is also seen in subtractions against PS1 images, but at a lower significance, and lies within the enhanced FXT uncertainty region (Liu et al., GCN Circ. 43802). We suggest it is the optical counterpart of the EP source. We notice that these coordinates are consistent with the position of a galaxy present in the Legacy Survey catalog (Dey et al., 2019) with magnitudes g = 23.78 +/- 0.13, r = 23.68 +/- 0.14, i = 23.86 +/- 0.27 and z = 23.56 +/- 0.37 and with a photo-z = 1.22 +/- 0.55. In the r band, the total magnitude of the galaxy and the candidate counterpart faded from 22.54 +/- 0.08 in our first epoch to 23.39 +/- 0.15 in our second epoch (a difference of 0.85 +/- 0.17) and in the z band it faded from 22.03 +/- 0.17 to 22.69 +/- 0.16 (a difference of 0.66 +/- 0.23). These fadings have significances of 5.0- and 2.8-sigma, respectively. The detection of this candidate in r as well as z is consistent with the photo-z of the coincident galaxy Therefore, we suggest that this galaxy might be the host. The non-detection of this source in deep imaging by Levan et al. (GCN Circ. 43805) suggests that it faded very quickly. This is perhaps consistent with temporal decay estimated from the two values reported in X-rays by (Liu et al., GCN Circ. 43802) alpha of approximately 2.2 and suggests the presence of an early jet break. 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/43806. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41917] EP260221a: Gemini South z-band upper limit
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43805 SUBJECT: EP260221a: Gemini South z-band upper limit DATE: 26/02/22 11:42:57 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> Andrew J. Levan (Radboud), G. Corcoran (UCD), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), J. A. Quirola-Vasquez (Radboud), R. A. J. Eyles-Ferris (Leicester), J. Sanchez-Sierras (Radboud), D. Xu (NAOAC), report on behalf of a larger collaboration We observed the field of the fast X-ray transient EP260221a (Zhang et al., GCN 43791; Liu et al., GCN 43802) using the GMOS-S instrument mounted on the Gemini South telescope (Cerro Pachon, Chile). A single 300 s z-band observation was secured starting on 2026 Feb 22 at 08:20 UT (20.62 hr after trigger). No new source is detected within the EP/FXT error circle, down to a limiting magnitude z = 24.8 (AB, calibrated against nearby sources from the Pan-STARRS catalog, and not corrected for Galactic extinction). A number of faint sources are visible consistent with the EP/FXT position, but they are all present in archival imaging from the Legacy survey and from DECam. Our results are consistent with other non-detection reports (Mandarakas et al., GCN 43793; Kumar et al., GCN 43794; He et al., GCN 43798; Lipunov et al., GCN 43803). We thank excellent support from the Gemini staff, in particular Lindsay Magill. View this GCN Circular online at https://gcn.nasa.gov/circulars/43805. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41916] GRB 260222A: Fermi GBM Final Real-time Localization
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43804 SUBJECT: GRB 260222A: Fermi GBM Final Real-time Localization DATE: 26/02/22 10:20:22 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 10:09:38 UT on 22 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260222A (trigger 793447783.750804 / 260222423). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 336.2, Dec = 61.7 (J2000 degrees, equivalent to J2000 22h 24m, 61d 42'), with a statistical uncertainty of 4.4 degrees. The angle from the Fermi LAT boresight is 36.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260222423/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260222423/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260222423/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43804. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41915] EP260221a: Global MASTER-Net observations report
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43803 SUBJECT: EP260221a: Global MASTER-Net observations report DATE: 26/02/22 08:54:25 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 EP260221a ( EP Team et al., GCN 43791) errorbox 44530 sec after notice time and 51263 sec after trigger time at 2026-02-22 01:57:37 UT, with upper limit up to 13.5 mag. The observations began at zenith distance = 76 deg. The sun altitude is -22.8 deg. MASTER-OAFA robotic telescope located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP260221a errorbox 53402 sec after notice time and 60136 sec after trigger time at 2026-02-22 04:25:30 UT, with upper limit up to 20.7 mag. The observations began at zenith distance = 27 deg. The sun altitude is -48.3 deg. The galactic latitude b = 40 deg., longitude l = 286 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3149283 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 51354 | 2026-02-22 01:57:37 | MASTER-Kislovodsk | (11h 54m 51.01s , -20d 28m 04.3s) | C | 180 | 13.5 | 60167 | 2026-02-22 04:25:30 | MASTER-OAFA | (11h 50m 53.67s , -20d 40m 02.3s) | C | 60 | 20.3 | 60227 | 2026-02-22 04:25:30 | MASTER-OAFA | (11h 50m 53.67s , -20d 40m 02.4s) | C | 180 | 20.5 | Coadd 60243 | 2026-02-22 04:26:46 | MASTER-OAFA | (11h 50m 48.37s , -20d 40m 39.3s) | C | 60 | 20.3 | 60317 | 2026-02-22 04:28:00 | MASTER-OAFA | (11h 50m 49.21s , -20d 39m 36.9s) | C | 60 | 18.6 | 60395 | 2026-02-22 04:29:18 | MASTER-OAFA | (11h 59m 28.08s , -20d 41m 19.6s) | C | 60 | 19.8 | 60455 | 2026-02-22 04:29:18 | MASTER-OAFA | (11h 59m 28.07s , -20d 41m 19.6s) | C | 180 | 20.7 | Coadd 60474 | 2026-02-22 04:30:37 | MASTER-OAFA | (11h 59m 24.96s , -20d 40m 07.1s) | C | 60 | 20.2 | 60551 | 2026-02-22 04:31:54 | MASTER-OAFA | (11h 59m 25.03s , -20d 41m 43.3s) | C | 60 | 20.2 | 75471 | 2026-02-22 08:39:34 | MASTER- | (11h 56m 08.31s , -21d 31m 03.3s) | C | 180 | 19.7 | 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/43803. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41914] EP260221a: EP-FXT follow-up observation
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43802 SUBJECT: EP260221a: EP-FXT follow-up observation DATE: 26/02/22 05:03:51 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Tian-Yu Liu, X. X. Sun, M.-H. Zhang, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260221a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Zhang et al., GCN 43791). The optical upper limits were reported by COLIBRI telescope, GOTO and the 2.16m Xinglong Telescope (GCN 43793, GCN 43794, GCN 43798). The refined analysis of the WXT data shows that the event started at T0=2026-02-21T11:39:48 (UTC) and lasted for 550 seconds. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 3.5 x 10^20 cm^-2 and a photon index of 2.9 (-0.3/+0.4). The derived average unabsorbed 0.5-4 keV flux is 3.1 (-0.7/+0.5) x 10^(-10)erg/s/cm^2. The Follow-up X-ray Telescope (FXT) on board EP observed this source at 2026-02-21T12:44:34 (UTC), about 1 hour 5 minutes after T0. The exposure time of this observation is 5997s. On-ground analysis of the FXT data found an uncatalogued source at R.A. = 178.7560, DEC = -20.9819 (J2000) with an uncertainty of about 10 arcsec (radius, 90% C.L. statistical and systematic), which is consistent with the WXT position. The average 0.5-10 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 3.5 x 10^20 cm^-2 and a photon index of 1.36 (-0.22/+0.22). The derived average unabsorbed 0.5-10 keV flux is 6.9 (-1.6/+2.0) x 10^(-13)erg/s/cm^2. 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/43802. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41913] Fermi GRB 260221B: Global MASTER-Net observations report
by GCN Circulars 22 Feb '26

22 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43801 SUBJECT: Fermi GRB 260221B: Global MASTER-Net observations report DATE: 26/02/22 02:30:42 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 260221B ( Fermi GBM team, GCN 43800) errorbox 9789 sec after notice time and 9824 sec after trigger time at 2026-02-22 02:02:07 UT, with upper limit up to 15.3 mag. The observations began at zenith distance = 52 deg. The sun altitude is -22.0 deg. The galactic latitude b = 16 deg., longitude l = 112 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3150150 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 9855 | 2026-02-22 02:02:07 | MASTER-Kislovodsk | (21h 49m 42.78s , +74d 56m 55.5s) | C | 60 | 12.5 | 9970 | 2026-02-22 02:04:03 | MASTER-Kislovodsk | (21h 29m 11.14s , +73d 03m 13.8s) | C | 60 | 15.3 | 10074 | 2026-02-22 02:05:47 | MASTER-Kislovodsk | (21h 30m 08.15s , +73d 03m 12.4s) | C | 60 | 12.1 | 10227 | 2026-02-22 02:08:19 | MASTER-Kislovodsk | (21h 23m 43.72s , +76d 53m 40.4s) | C | 60 | 14.2 | 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/43801. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41912] GRB 260221B: Fermi GBM Final Real-time Localization
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43800 SUBJECT: GRB 260221B: Fermi GBM Final Real-time Localization DATE: 26/02/21 23:29:14 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 SHORT GRB At 23:18:22 UT on 21 Feb 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260221B (trigger 793408707.776836 / 260221971). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 328.4, Dec = 75.0 (J2000 degrees, equivalent to J2000 21h 53m, 75d 00'), with a statistical uncertainty of 8.4 degrees. The angle from the Fermi LAT boresight is 12.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221971/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221971/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260221971/… View this GCN Circular online at https://gcn.nasa.gov/circulars/43800. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41911] EP-WXT01709258519: Xinglong optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43799 SUBJECT: EP-WXT01709258519: Xinglong optical upper limit DATE: 26/02/21 21:25:15 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Min-He (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration: Following the detection of EP-WXT01709258519, we observed the field of EP-WXT01709258519 ( +11:05:00.96 +38:12:32.40 ) using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x300s clear-band frames with a median time of 2026-02-21T19:28:39, 11 hr after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (WXT01709258519), down to 3-sigma limiting magnitudes of 21.01 mag for 2.16-m, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43799. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 41910] EP-WXT01709258519: Xinglong optical upper limit
by GCN Circulars 21 Feb '26

21 Feb '26

TITLE: GCN CIRCULAR NUMBER: 43799 SUBJECT: EP-WXT01709258519: Xinglong optical upper limit DATE: 26/02/21 21:25:15 GMT FROM: Xinglong Observatory at National Astronomical Observatories (NAOC), Chinese Academy of Sciences (CAS) <xinglong(a)nao.cas.cn> Min-He (NAOC), Junjie-Jin (NAOC), Haiyang-Mu (NAOC), Feng-Xiao (NAOC), Pengliang-Du (NAOC), Zhou-Fan (NAOC), Hong-Wu (NAOC) report on behalf of a large collaboration: Following the detection of EP-WXT01709258519, we observed the field of EP-WXT01709258519 ( +11:05:00.96 +38:12:32.40 ) using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x300s clear-band frames with a median time of 2026-02-21T19:28:39, 11 hr after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (WXT01709258519), down to 3-sigma limiting magnitudes of 21.01 mag for 2.16-m, calibrated with Pan-STARRS sources in the field. Also there is no apparent brightening for the catalogued sources within the error circle. View this GCN Circular online at https://gcn.nasa.gov/circulars/43799. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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