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[vsnet-grb-info 42313] GRB 260402A: WINTER J-band upper limit
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44192 SUBJECT: GRB 260402A: WINTER J-band upper limit DATE: 26/04/02 18:08:21 GMT FROM: Benjamin Schneider at MIT <bschn(a)mit.edu> Benjamin Schneider (LAM), Geoffrey Mo (Caltech/Carnegie), Robert Stein (UMD), Viraj Karambelkar (Columbia), Tomas Ahumada (NOIRLab), Danielle Frostig (CfA), Nathan Lourie (MIT), Robert Simcoe (MIT), and Mansi Kasliwal (Caltech) report: We observed the field of GRB 260402A detected by SVOM/ECLAIRs (Tan et al., GCN 44181) and EP/WXT (Zhao et al., GCN Circ. 44186) 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 2026-04-02 at 10:58:52 UT (28.58 min after the trigger) and consisted of 30 exposures of 120 s in the J-band. 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. The magnitude is in the AB system and is not corrected for Galactic extinction. In the stacked image, we do not detect any new source at the FXT position (Zhao et al., GCN Circ. 44186) or MXT position (Gotz et al., GCN Circ. 44182) and derive the following 5-sigma upper limit: J > 18.9 Our upper limit is consistent with previously reported optical upper limits from Antier et al. (GCN Circ. 44183), Carrasco et al. (GCN Circ. 44184), Freeberg et al. (GCN Circ. 44185), Wu et al. (GCN Circ. 44189), Li et al. (GCN Circ. 44190), and Vijaykumar et al. (GCN Circ. 44191). 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/44192. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42312] GRB260402A: GROWTH-India Telescope optical upper limit
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44191 SUBJECT: GRB260402A: GROWTH-India Telescope optical upper limit DATE: 26/04/02 17:45:27 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> V. Vijaykumar, A. Khade, R. Arya, V. Swain, S. Patil, A.P. Saikia, T. Mohan, V. Bhalerao (IITB), G.C. Anupama, S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team: We observed the field of GRB260402A detected by SVOM/ECLAIRs (SVOM, GCN 44181), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-04-02 14:10:35 (UTC), i.e., 3.65 hours after the trigger, and obtained multiple exposures in the r' filter. We do not detect any transient in our image within the uncertainty region of source position reported by ECLAIRs and MXT (Tan et al., GCN Circ. 44181, Gotz et al., GCN Circ.44182). The photometric upper limit is as follows: | MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Magnitude (AB) | | ------------ | ------ | -------------- | ------------------- | -------------- | | 61132.590| r' | 3.92 | 5x360 | 20.5 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our magnitude for the optical counterpart is consistent with other optical observations (GCN 44190 Li et al.; GCN 44189 Wu et al.; GCN 44185 Freeberg et al.; GCN 44184 Carrasco et al.; GCN 44183 Antier et al.) 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/44191. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42311] GRB 260402A / EP260402a: SVOM/VT optical upper limits
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44190 SUBJECT: GRB 260402A / EP260402a: SVOM/VT optical upper limits DATE: 26/04/02 16:30:34 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, C. Wu, Y. L. Qiu, L. P. Xin, Y. N. Ma, Z. H. Yao, J. R. Xu, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, L. Lan, J. S. Deng, J. Y. Wei (NAOC), J. Palmerio (CEA/Irfu), W. Tan (IHEP) and R. Li (YNAO) report on behalf of the SVOM/VT team. SVOM/VT performed observations with automatic slew to the field of GRB 260402A triggered by SVOM/ECLAIRs (sb26032123, Tan et al., GCN 44181), SVOM/GRM (Tan et al., GCN 44181) and Einstein Probe (EP260402a, Zhao et al., GCN 44186). The observation started at 2026-04-02T10:44:07 UTC, approximately 13.8 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. No uncatalogued sources are detected in single or stacked images within the error box of SVOM/MXT (Gotz et al., GCN 44182) or EP-FXT (Zhao et al., GCN 44186), compared to the Legacy Survey. The 3-sigma limit magnitudes are VT_B ~ 23.1 mag and VT_R ~ 23.0 mag at 31.3 minutes post trigger. Our result is consistent with the non-detection reports from SVOM/COLIBRÍ (Antier et al., GCN 44183), MASTER (Carrasco et al., GCN 44184), Kilonova-Catcher (Freeberg et al., GCN 44185) and SVOM/C-GFT (Wu et al., GCN 44189). Given the early optical non-detection, near-infrared follow-up observations are encouraged. 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/44190. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42310] EP260402a/GRB 260402A: SVOM/C-GFT upper limit
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44189 SUBJECT: EP260402a/GRB 260402A: SVOM/C-GFT upper limit DATE: 26/04/02 15:30:47 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> C. Wu (NAOC), Z. Kang (CHO), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) , W. Tan, R. Li (IHEP) report on behalf of the SVOM/C-GFT team: We observed the field of GRB 260402A (SVOM burst-id sb26040203) detected by SVOM/ECLAIRs (Tan et al., GCN 44181) with LATIOS on SVOM/C-GFT. Observations started at 2026-04-02T12:50:51 UTC, ~2.34 hr after the trigger. We obtained i-band follow-up imaging. After preliminary analysis，no credible candidate was detected within the error box provided by SVOM/MXT (Gotz et al., GCN 44182) and EP/MXT (Zhao et al., GCN 44186) in our stacked image. The 3-sigma upper limit is: | Mid_t - T0 (hr) | Exposure Time (s) | Band | Upper Limit (AB) | |----------------|-------------------|------|------------------| | 2.69 | 30×30 | i | 19.0 | The photometry was calibrated against Pan-STARRS1 stars and no correction for Galactic dust extinction was applied. This result is consistent with Antier et al. (GCN 44183) and Freeberg et al.(GCN 44185). We thank the observation assistants Ying-huai Hao and Chun-lei Guo at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcsec x 21 arcsec FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/44189. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42309] GRB 260401A: SVOM/GRM observation
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44188 SUBJECT: GRB 260401A: SVOM/GRM observation DATE: 26/04/02 15:06:11 GMT FROM: renyz16607(a)163.com SVOM/GRM team: Yang-Zhao Ren, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Hui Yang (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by GRB 260401A (SVOM trigger reference: sb26040101) at 2026-04-01T10:53:33.600 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44174), MAXI/GSC (Usuki et. al., GCN #44176), CALET/GBM (Cannady et al., GCN #44177), NuSTAR (Waratkar et al., GCN #44178), and GECAM-B (Ren et al., GCN #44187). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of multiple pulses with a T90 of 24 +2/-2 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260401A.png In addition, the position of this burst, as determined by Fermi/GBM (RA = 219.5, Dec = -17.4, GCN #44174), is located at about 74 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view, but this burst still clearly detected by ECLAIRs through the shield. With this localization, the time-averaged spectrum from T0-10 to T0+10 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.64 +0.06/-0.06 and the cutoff energy, parameterized as Epeak, is 321 +141/-77 keV. The event fluence (10-1000 keV) in this time interval is (1.44 +0.06/-0.07)E-05 erg/cm^2. The 1s peak spectrum, measured from T0-0.1 to T0+0.9 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.26 +0.07/-0.07 and the cutoff energy, parameterized as Epeak, is 391 +84/-59 keV. The flux (10-1000 keV) in this time interval is (3.28 +0.14/-0.15)E-06 erg/cm^2/s. The localization of GRB 260401A in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260401A_amati.png The localization of GRB 260401A in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260401A_yonetoku.png 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. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Yang-Zhao Ren (IHEP)(renyz(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44188. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42308] GRB 260401A: GECAM-B observation
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44187 SUBJECT: GRB 260401A: GECAM-B observation DATE: 26/04/02 15:01:22 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260401A, at 2026-04-01T10:53:29.200 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44174), MAXI/GSC (Usuki et. al., GCN #44176), CALET/GBM (Cannady et al., GCN #44177), and NuSTAR (Waratkar et al., GCN #44178). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 28.8 +0.1/-0.2 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260401A.png The time-averaged spectrum from T0 to T0 + 15 s is best fitted by a power law function. The power law index is -1.51 +0.08/-0.07. The event fluence (10-1000 keV) in this time interval is (2.20 +0.11/-0.10) E-05 erg/cm^2. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/44187. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42307] EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44186 SUBJECT: EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient DATE: 26/04/02 14:16:37 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. Q. Zhao (USTC,PRIC), C. L. Guo, J. W. Hu, C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of an X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260402a. The transient triggered EP-WXT (ID: 01709259488) at 2026-04-02T10:30:41 (UTC). The WXT position of the source is R.A. = 170.994 deg, DEC = 63.604 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). EP260402a is temporally and spatially consistent with GRB 260402A (GCN #44181). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically triggered by SVOM GRB detection, began at 2026-04-02T12:55:33Z. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 170.9607 deg, DEC = 63.6128 deg (J2000) with an uncertainty of 20 arcsec in radius (90% C.L. statistical and systematic). Further information will be updated when the telemetry data is received. 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/44186. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42306] GRB 260402A: Kilonova-Catcher optical upper limit
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44185 SUBJECT: GRB 260402A: Kilonova-Catcher optical upper limit DATE: 26/04/02 13:09:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Freeberg (KNC), D. Turpin (CEA-Saclay/Irfu), C. Andrade(UMN), S. Antier (IJCLab), M. Coughlin (UMN), S. Karpov (FZU), P. Hello (IJCLAB), M. Pillas (IAP) on behalf of the GRANDMA/Kilonova-Catcher collaboration: We observed the field of GRB 260402A detected by SVOM/ECLAIRs (Tan et al., GCN 44181) with the GRANDMA citizen science project Kilonova-catcher (KNC). Our observations were performed with the TEC160FL telescope operated by M. Freeberg. Our observations started at TGRB+20.8 min and were taken with the sdssr filter. In our stacked frames, subtracted from the PanSTARRS DR2 template image, we do not detect any optical counterpart in the SVOM/ECLAIRs error radius. We report our follow-up results in the table below: +----------------+----------+---------+---------------+--------------+ | Tmid-TGRB (min)| Exp (s) | Filter | Magnitude | Instrument | +================+==========+=========+===============+==============+ | 29.97 | 5 x 180s | r (AB) | 19.5 (5 sigma)| TEC160FL | +----------------+----------+---------+---------------+--------------+ All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. We use the SkyPortal application (skyportal.io) to monitor our observational campaign (Coughlin et al. 2023). GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44185. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42305] GRB 260402A: MASTER optical observations
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44184 SUBJECT: GRB 260402A: MASTER optical observations DATE: 26/04/02 12:22:04 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> L.Carrasco, J.R.Valdes, V.Chavushyan, V.M.Patino Alvarez,J.Martinez, A.R.Corella, J.Tanori, L. Villalobos, L.H.Rodriguez (INAOE, Guillermo Haro Astrophysics Observatory) V.Lipunov, A.Kuznetsov, I.Panchenko, P.Balanutsa, G.Antipov, E.Gorbovskoy, N.Tiurina, V.Senik, A.Chasovnikov, Ya.Kechin, V.Topolev, D.Vlasenko, A.Sankovich,Yu.Tselik (Lomonosov MSU), M.J. Segura, C.Francile, F. Podesta, R.Podesta, E. Gonzalez (Observatorio Astronomico Felix Aguilar (OAFA), A. Tlatov, D. Dormidontov (Kislovodsk Solar Station of the Pulkovo Observatory), N.Budnev, O.Gress (ISU), A.Sosnovskij (CrAO), D.Buckley (SAAO), R.Rebolo (The Instituto de Astrofisica de Canarias), A. Gabovich, V.Yurkov (Blagoveschensk Educational StateUniversity) MASTER-OAGH robotic telescope of MASTER Global Robotic Net [1-4] started SVOM GRB 260302A (Tan et al. GCN 44181, Gotz et al. GCN 44182 Ttrigger=2026-04-02 10:30:17UT) at 2026-04-02 10:55:46UT (25min after trigger time) with m_lim=19.1m(unfiltered) at 1st image. We didn't find new object inside error-box at single images.Observations and reduction will be continued. Error-box altitude was 34deg, the sun_alt=-28deg, the FULL moon (0.99) alt=27deg (in 75 deg from erro-box) Cover map is available here https://master.sai.msu.ru/site/master2/event.php?id=3227188 [1] Lipunov et al., 2010, Advances in Astronomy, vol. 2010, 30L [2] Lipunov et al. 2022, Universe, Vol. 8(5), id.271 [3] Lipunov et a. 2019, ARep, vol.63, 293 [4] Lipunov et al. 2023, Astronomical Robotic Networks and Operative Multichanel Astrophysics,Lomonosov MSU PRESS, 591pp. http://www.pereplet.ru/lipunov/625.html#625 View this GCN Circular online at https://gcn.nasa.gov/circulars/44184. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42304] GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
by GCN Circulars 02 Apr '26

02 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44183 SUBJECT: GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit DATE: 26/04/02 12:17:52 GMT FROM: antier(a)ijclab.in2p3.fr Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Alan M. Watson (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), 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), Antonio de Ugarte Postigo (LAM), W. Tan (IHEP), R. Li (IHEP) report: We imaged the field of the SVOM GRB 260402A (Tan et al., GCN Circ. 44181) using the DDRAGO wide-field imager on the SVOM/COLIBRÍ (FM-GFT) telescope. We observed from 2026-04-02 10:37:04 to 11:52:05 UTC (from 7 minutes after the trigger) and obtained about 45 min of exposure in the r/z filters. The data were reduced and coadded with the ASU and Colibri 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 image, we do not detect any new source at the ECLAIRs and MXT source position (Tan et al., GCN Circ. 44181, Gotz et al., GCN Circ.44182) and down to the following 3-sigma limit: r > 22.6 z > 22.0 Further observations are ongoing. We thank the staff of the Observatorio Astronómico Nacional at Sierra de San Pedro Mártir, as well as the technical and engineering teams at CEA, CPPM, IRAP, LAM, OHP, OSU Pytheas, and UNAM. 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/44183. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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