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[vsnet-grb-info 42474] EP-WXT trigger 01709260303: KAIT optical observations
by GCN Circulars 20 Apr '26

20 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44352 SUBJECT: EP-WXT trigger 01709260303: KAIT optical observations DATE: 26/04/20 06:33:01 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, automatically responded to the EP-WXT trigger 01709260303 (Yin et al., GCN 44350) starting at 10:53 UT, about 3.5 hours after the trigger. A set of B,V,R,I and clear (roughly R) filter images were obtained and lasted for ~0.9 hours. We performed photometry on the suggested flare star Gaia DR3 4524306802880186496 and did not find obvious variability on its brightness at 0.1 mag level. View this GCN Circular online at https://gcn.nasa.gov/circulars/44352. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42473] EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
by GCN Circulars 20 Apr '26

20 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44351 SUBJECT: EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring DATE: 26/04/20 04:03:59 GMT FROM: Alberto Castro-Tirado at Inst.de Astro. de Andalucia <ajct(a)iaa.es> S. Guziy, F. J. Aceituno, A. J. Castro-Tirado, M.D. Caballero-García, M. Gritsevich, I. Pérez-García, R. Sánchez-Ramírez, S.-Y. Wu (IAA-CSIC) and A. Fernández-Martin and M. M. Sánchez-Andújar (CAHA), on behalf of a larger collaboration,report: We observed EP260416a (Hu et al., GCN 44307) with both the 1.5m telescope at Observatorio de Sierra Nevada (OSN) and the 2.2m telescope at Calar Alto Observatory (CAHA), in Southern Spain. A series of 300 s BVRI exposures were obtained at the 1.5m OSN starting on Apr 17, 21:04 UT, complemented by one 100s i-band image at the 2.2m CAHA, on Apr 18, 01:04 UT., i.e. 39.6 h and 43.6 h respectively, after the initial trigger. The optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al., GCN 44334, He et al. GCN 44336, An et al. GCN 44339, Jelinek et al. GCN 44341) is well detected in our images. We measure B = 21.08 +/- 0.14 and R = 20.99 +/- 0.07 on Apr 17, 21:15 UT and I = 19.82 +/-0.18 on Apr 18, 01:04 UT (none corrected for Galactic extinction). The night after, a second epoch BVRI observation was conducted at the 1.5m OSN, for which measure R = 21.59 +/- 0.10 on Apr 18, 20:14 UT. Our measurement is consistent with the continued fading of the afterglow. Further optical monitoring is being carried out. View this GCN Circular online at https://gcn.nasa.gov/circulars/44351. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42472] The EP-WXT trigger 01709260303 is likely a flaring star
by GCN Circulars 20 Apr '26

20 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44350 SUBJECT: The EP-WXT trigger 01709260303 is likely a flaring star DATE: 26/04/20 02:32:00 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), Z.-C. Zou (NJU), H.Q. Cheng and H. Sun (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709260303 at the time of 2026-04-19T07:22:35, is likely a stellar flare associated with Gaia DR3 4524306802880186496. The estimated flux of the flare is around 8e-11 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.1e31 erg/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/44350. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42471] GRB 260417A: SVOM/GRM observation
by GCN Circulars 19 Apr '26

19 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44349 SUBJECT: GRB 260417A: SVOM/GRM observation DATE: 26/04/19 16:33:14 GMT FROM: zhangjinpeng(a)ihep.ac.cn SVOM/GRM team: Jin-Peng Zhang, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Sebastien Guillot (IRAP) Report on behalf of the SVOM team: SVOM/GRM detected GRB 260417A at 2026-04-17T00:10:11.500 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44317), AstroSat CZTI (S. Salunke et al., GCN #44330) and possibly by EP (K. R. Ni et al., GCN #44337). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst mainly consists of a pulse with a T90 of 38 +15/-10 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260417A.png In addition, the position of this burst, according to Fermi/GBM localization (RA = 252.0, Dec = -19.8, error(stat) = 3.4, Fermi GBM Team, GCN #44317), is located at about 90.3 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-20 to T0+20 s is fitted by a power law function. The power law index is -1.77 +0.09/-0.09. The event fluence (10-1000 keV) in this time interval is (9.1 +1.0/-1.1)E-06 erg/cm^2. 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/GRM point of contact for this burst is: Jin-Peng Zhang (IHEP) (zhangjinpeng(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44349. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42470] EP260321A/AT2026gzf: Optical observation from 1.3m DFOT
by GCN Circulars 19 Apr '26

19 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44348 SUBJECT: EP260321A/AT2026gzf: Optical observation from 1.3m DFOT DATE: 26/04/19 09:06:27 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Pankaj Pawar, Divyanshu Janghel, Dhruv Jain, Debalina Kar, and Kuntal Misra (ARIES) report: We observed the field of EP260321A/AT2026gzf detected by EP-WXT (Huang, GCN 44068) with the 1.3m Devasthal Fast Optical Telescope (DFOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. Observations began on 2026-04-16 at 14:22:58 UT, i.e., ~26.07 days after the EP-WXT trigger. We have taken multiple frames with an exposure time of 300s in the R filter. We stacked the images after the alignment. We detect an optical afterglow in our stacked image. We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (days) Filter Exp time (s) Magnitude ================================================================= 2026-04-16 14:22:58 ~26.07 R 300s*4 17.14 +- 0.01 The optical detection of the burst is consistent with Lipunov et al., GCN 44069; Lee et al., GCN 44070; Aryan et al., GCN 44081; Tanvir et al., GCN 44082; Moran et al., GCN 44083; Ahumada et al., GCN 44084; Liu et al., GCN 44087; Sankar et al. GCN 44089; de Ugarte Postigo et al., GCN 44091; Xu et al., GCN 44092; Pankov et al. GCN 44103; Corcoran et al., GCN 44105; Rastinejad et al., GCN 44107; Gao et al., GCN 44110; He et al., GCN 44117; Zhang et al., GCN 44171; Li et al., GCN 44284; Volnova et al., GCN 44295. The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the USNO-B1.0 catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/44348. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42469] GRB 260419B: Fermi GBM Final Real-time Localization
by GCN Circulars 19 Apr '26

19 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44347 SUBJECT: GRB 260419B: Fermi GBM Final Real-time Localization DATE: 26/04/19 08:00:23 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 07:49:50 UT on 19 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260419B (trigger 798277795.43596 / 260419326). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 137.1, Dec = -33.8 (J2000 degrees, equivalent to J2000 09h 08m, -33d 47'), with a statistical uncertainty of 9.6 degrees. The angle from the Fermi LAT boresight is 62.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260419326/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260419326/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260419326/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44347. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42468] GRB 260419A: Fermi GBM Final Real-time Localization
by GCN Circulars 19 Apr '26

19 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44346 SUBJECT: GRB 260419A: Fermi GBM Final Real-time Localization DATE: 26/04/19 07:20:17 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 07:09:40 UT on 19 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260419A (trigger 798275385.308626 / 260419298). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 317.4, Dec = -34.4 (J2000 degrees, equivalent to J2000 21h 09m, -34d 23'), with a statistical uncertainty of 2.3 degrees. The angle from the Fermi LAT boresight is 77.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260419298/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260419298/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260419298/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44346. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42467] Fermi trigger No 798275385: Global MASTER-Net observations report
by GCN Circulars 19 Apr '26

19 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44345 SUBJECT: Fermi trigger No 798275385: Global MASTER-Net observations report DATE: 26/04/19 07:16:07 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB260419.30 (trigger No 798275385,20h 50m 14.40s , -47d 41m 24.0s, R=4.3) errorbox 42 sec after notice time and 75 sec after trigger time at 2026-04-19 07:10:56 UT, with upper limit up to 19.4 mag. The observations began at zenith distance = 52 deg. The sun altitude is -48.6 deg. The galactic latitude b = -40 deg., longitude l = 352 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3259527 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 86 | 2026-04-19 07:10:56 | MASTER-OAFA | (20h 49m 30.10s , -47d 58m 25.7s) | C | 20 | 19.4 | 112 | 2026-04-19 07:11:22 | MASTER-OAFA | (20h 49m 30.11s , -47d 58m 24.7s) | C | 20 | 19.3 | 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/44345. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42466] EP260417a: GROWTH-India Telescope optical upper limit
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44344 SUBJECT: EP260417a: GROWTH-India Telescope optical upper limit DATE: 26/04/18 23:25:30 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> A. Khade (IITB), A. Kumar (IITB), V. Vijaykumar (IITB), T. Mohan (IITB), V. Swain (IITB), D. Eappachen (IIA), S. Patil (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team: We observed the field of EP260417a detected by Einstein Probe (Wang et al., GCN 44325), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-04-18 21:01:23 (UTC), i.e., 1.86 days after the trigger, and obtained multiple exposures in the r' filter. No optical counterpart is detected at the position reported by He et al. (GCN 44326) in our stacked image. The photometric upper limit is as follows: | MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | -------------- | ------------------- | ---------------- | | 61148.885 | r' | 44.85 | 4x360 | 20.64 | The measurement is calibrated against PanSTARRS DR1 (Chambers et al., 2016) and not corrected for Galactic extinction. Our upper limit is consistent with the reported optical measurements by He et al. (GCN 44326) and Lipunov et al. (GCN 44338). 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/44344. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42465] Fermi GRB 260417B: Global MASTER-Net observations report
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44343 SUBJECT: Fermi GRB 260417B: Global MASTER-Net observations report DATE: 26/04/18 23:15:27 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260417B ( Fermi GBM team, GCN 44331) errorbox 66043 sec after notice time and 66079 sec after trigger time at 2026-04-18 10:05:14 UT, with upper limit up to 18.4 mag. Observations started at twilight. The observations began at zenith distance = 31 deg. The sun altitude is -11.6 deg. MASTER-SAAO robotic telescope located in South Africa (South African Astronomical Observatory) started inspect of the Fermi GRB 260417B errorbox 1 days 23747 sec after notice time and 1 days 23783 sec after trigger time at 2026-04-18 22:20:18 UT, with upper limit up to 18.7 mag. The observations began at zenith distance = 48 deg. The sun altitude is -68.6 deg. The galactic latitude b = 1 deg., longitude l = 1 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3256668 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 23203 | 2026-04-17 22:10:08 | MASTER- | (17h 10m 25.00s , -22d 17m 31.5s) | C | 60 | 14.7 | 23280 | 2026-04-17 22:11:25 | MASTER- | (17h 25m 38.80s , -19d 39m 45.5s) | C | 60 | 13.2 | 23367 | 2026-04-17 22:12:52 | MASTER- | (17h 28m 29.57s , -18d 22m 14.8s) | C | 60 | 14.2 | 23445 | 2026-04-17 22:14:10 | MASTER- | (17h 09m 03.19s , -23d 33m 52.4s) | C | 60 | 14.9 | 24134 | 2026-04-17 22:25:39 | MASTER- | (17h 08m 12.30s , -24d 53m 35.2s) | C | 60 | 16.3 | 24217 | 2026-04-17 22:27:02 | MASTER- | (16h 56m 13.19s , -26d 09m 52.5s) | C | 60 | 15.3 | 66109 | 2026-04-18 10:05:14 | MASTER-OAFA | (17h 05m 41.45s , -21d 18m 08.8s) | C | 60 | 18.4 | 66184 | 2026-04-18 10:06:29 | MASTER-OAFA | (17h 14m 24.55s , -21d 19m 32.1s) | C | 60 | 18.0 | 66259 | 2026-04-18 10:07:44 | MASTER-OAFA | (17h 05m 42.90s , -21d 20m 07.9s) | C | 60 | 18.3 | 66335 | 2026-04-18 10:09:00 | MASTER-OAFA | (17h 14m 23.15s , -21d 20m 27.1s) | C | 60 | 18.0 | 66410 | 2026-04-18 10:10:14 | MASTER-OAFA | (17h 05m 44.83s , -21d 18m 07.3s) | C | 60 | 18.1 | 66561 | 2026-04-18 10:12:46 | MASTER-OAFA | (16h 54m 04.36s , -25d 06m 35.0s) | C | 60 | 17.9 | 110213 | 2026-04-18 22:20:18 | MASTER-SAAO | (17h 03m 25.97s , -21d 49m 48.4s) | C | 60 | 18.6 | 110399 | 2026-04-18 22:23:24 | MASTER-SAAO | (17h 17m 53.69s , -21d 35m 09.4s) | C | 60 | 18.1 | 110399 | 2026-04-18 22:23:24 | MASTER-SAAO | (17h 19m 53.70s , -21d 51m 16.9s) | C | 60 | 18.3 | 110492 | 2026-04-18 22:24:57 | MASTER-SAAO | (16h 59m 36.82s , -27d 32m 32.8s) | C | 60 | 17.5 | 110492 | 2026-04-18 22:24:57 | MASTER-SAAO | (16h 57m 30.65s , -27d 16m 26.2s) | C | 60 | 17.7 | 110586 | 2026-04-18 22:26:30 | MASTER-SAAO | (16h 59m 00.63s , -23d 27m 32.8s) | C | 60 | 18.7 | 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/44343. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42464] EP260417b: GROWTH-India Telescope optical upper limit
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44342 SUBJECT: EP260417b: GROWTH-India Telescope optical upper limit DATE: 26/04/18 22:00:13 GMT FROM: V. Swain at IIT Bombay <vishwajeet.s(a)iitb.ac.in> V. Vijaykumar (IITB), T. Mohan (IITB), V. Swain (IITB), D. Eappachen (IIA), S. Patil (IITB), A.P. Saikia (IITB), V. Bhalerao (IITB), G.C. Anupama (IIA), S. Barway (IIA) and R. Norbu (IAO) report on behalf of the GIT team: We observed the field of EP260417b detected by Einstein Probe (Ni et al., GCN 44323), with 0.7m GROWTH-India Telescope (GIT). We started the observation at 2026-04-18 19:04:51 (UTC), i.e., 1.74 days after the trigger, and obtained a single exposure in the r' filter. We did not detect any transient in our image within the uncertainty region of source position reported by EP. The photometric upper limit is as follows: | MJD (mid) | Filter | tmid-t0 (hours) | Exposure Time (sec) | Upper limit (AB) | | ------------ | ------ | -------------- | ------------------- | ---------------- | | 61149.797 | r' | 41.78 | 420 | 19.3 | 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/44342. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42463] EP260416a: Ondrejov D50 optical detection
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44341 SUBJECT: EP260416a: Ondrejov D50 optical detection DATE: 26/04/18 19:52:07 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny, A. Malenakova and R. Hudec (ASU CAS Ondrejov, CZ) report: We observed the field of EP260416a (Hu et al., GCN 44307) with the 50 cm robotic telescope (D50) of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We obtained a series of 120 s Sloan-r band exposures starting at 20:09 UT on 2026 April 17, i.e. 38.66 h after the initial trigger, and combined 68 frames with a mean exposure time of 40.03 h after the trigger. The optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al., GCN 44334) is detected in the combined image. The preliminary AB magnitude of the object is r = 21.08 +/- 0.23, calibrated against the ATLAS catalog and not corrected for Galactic extinction. Our measurement is consistent with the continued fading of the afterglow. View this GCN Circular online at https://gcn.nasa.gov/circulars/44341. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42462] GRB 260418B: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44340 SUBJECT: GRB 260418B: Fermi GBM Final Real-time Localization DATE: 26/04/18 16:30:58 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 16:20:21 UT on 18 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260418B (trigger 798222026.725586 / 260418681). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 34.7, Dec = -40.5 (J2000 degrees, equivalent to J2000 02h 18m, -40d 30'), with a statistical uncertainty of 4.0 degrees. The angle from the Fermi LAT boresight is 47.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418681/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418681/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418681/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44340. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42461] EP260416a: VLT/FORS2 spectroscopic redshift confirmation
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44339 SUBJECT: EP260416a: VLT/FORS2 spectroscopic redshift confirmation DATE: 26/04/18 12:32:28 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> J. An (NAOC), A. Saccardi (CEA/Irfu), L. Cotter (UCD), D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), A. L. Thakur (INAF-IAPS) report on behalf of the Stargate collaboration: We observed the optical counterpart (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328; Li et al,. GCN 44334) of EP260416a (Hu et al., GCNs 44307, 44324) using the ESO VLT UT1 (Antu) equipped with the FORS2 spectrograph. Our observation started on 2026 April 18 at 03:04:13 UT (1.90 days after the EP trigger). A series of 3 spectra of 900 s each were obtained with the 300V grism, covering the wavelength range 3500-8600 AA. From a 60 s acquisition image (1.89 days after trigger), we measure a magnitude R = 20.99 +/- 0.06 (Vega), calibrated against nearby stars from the Pan-STARRS catalog using the Lupton (2005) transformations, and not corrected for Galactic extinction. In a preliminary reduction of the spectra, we detect a continuum over the entire wavelength range. At the blue edge of the spectrum, even though the S/N is low, we identify a broad trough at around 3540 AA, likely due to H I. We also detect multiple absorption features including O I, C II, Si IV, C IV, Si II, Fe II, Al II, Al III, at a common redshift of z = 1.910, which we thus suggest to be the redshift of EP260416a. The lack of any further hydrogen absorption at higher redshift implies that the z = 1.910 system is indeed local to the GRB. Our results confirm the tentative redshift measurement reported by He et al. (GCN 44336). We acknowledge expert support from the ESO observing staff in Paranal, particularly Hannah Osborne and Diego Parraguez. The analysis of this spectrum was carried out with the help of the zHunter tool (https://doi.org/10.5281/zenodo.15189495) View this GCN Circular online at https://gcn.nasa.gov/circulars/44339. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42460] EP260417a: Global MASTER-Net observations report
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44338 SUBJECT: EP260417a: Global MASTER-Net observations report DATE: 26/04/18 09:45:27 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP260417a ( EP Team et al., GCN 44325) errorbox 12831 sec after trigger time at 2026-04-17 03:56:53 UT, with upper limit up to 19.9 mag. The observations began at zenith distance = 45 deg. The sun altitude is -67.6 deg. MASTER-OAGH robotic telescope located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) was pointed to the EP260417a errorbox 78480 sec after notice time and 1 days 33084 sec after trigger time at 2026-04-18 09:34:26 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 53 deg. The sun altitude is -36.9 deg. The galactic latitude b = 19 deg., longitude l = 355 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3256324 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 4312 | 2026-04-17 01:34:24 | MASTER- | (16h 25m 32.78s , -22d 27m 07.0s) | C | 60 | 16.8 | 12861 | 2026-04-17 03:56:53 | MASTER-OAFA | (16h 22m 03.10s , -23d 33m 17.7s) | C | 60 | 18.9 | 12921 | 2026-04-17 03:56:53 | MASTER-OAFA | (16h 22m 03.09s , -23d 33m 17.9s) | C | 180 | 19.7 | Coadd 13013 | 2026-04-17 03:59:24 | MASTER-OAFA | (16h 22m 05.31s , -23d 31m 13.7s) | C | 60 | 19.5 | 13243 | 2026-04-17 04:03:14 | MASTER-OAFA | (16h 22m 01.68s , -23d 31m 04.9s) | C | 60 | 19.4 | 13395 | 2026-04-17 04:05:46 | MASTER-OAFA | (16h 22m 02.65s , -23d 33m 00.6s) | C | 60 | 19.5 | 13455 | 2026-04-17 04:05:46 | MASTER-OAFA | (16h 22m 02.65s , -23d 33m 00.5s) | C | 180 | 19.9 | Coadd 15146 | 2026-04-17 04:34:57 | MASTER-OAFA | (16h 22m 04.82s , -23d 30m 29.9s) | C | 60 | 19.6 | 15221 | 2026-04-17 04:36:12 | MASTER-OAFA | (16h 22m 04.76s , -23d 32m 06.6s) | C | 60 | 19.7 | 15297 | 2026-04-17 04:37:28 | MASTER-OAFA | (16h 22m 07.64s , -23d 30m 28.6s) | C | 60 | 19.6 | 15357 | 2026-04-17 04:37:28 | MASTER-OAFA | (16h 22m 07.64s , -23d 30m 28.6s) | C | 180 | 19.9 | Coadd 15613 | 2026-04-17 04:42:44 | MASTER-OAFA | (16h 22m 02.17s , -23d 31m 58.9s) | C | 60 | 19.5 | 15688 | 2026-04-17 04:43:59 | MASTER-OAFA | (16h 22m 07.18s , -23d 31m 53.2s) | C | 60 | 19.5 | 15766 | 2026-04-17 04:45:17 | MASTER-OAFA | (16h 22m 04.70s , -23d 30m 07.5s) | C | 60 | 19.4 | 15826 | 2026-04-17 04:45:17 | MASTER-OAFA | (16h 22m 04.69s , -23d 30m 07.5s) | C | 180 | 19.9 | Coadd 17894 | 2026-04-17 05:20:45 | MASTER-OAFA | (16h 22m 01.37s , -23d 29m 11.6s) | C | 60 | 19.6 | 17967 | 2026-04-17 05:21:59 | MASTER-OAFA | (16h 22m 07.83s , -23d 30m 10.7s) | C | 60 | 19.6 | 18047 | 2026-04-17 05:23:18 | MASTER-OAFA | (16h 22m 00.60s , -23d 31m 09.3s) | C | 60 | 19.6 | 18107 | 2026-04-17 05:23:18 | MASTER-OAFA | (16h 22m 00.60s , -23d 31m 09.3s) | C | 180 | 19.5 | Coadd 18354 | 2026-04-17 05:28:26 | MASTER-OAFA | (16h 22m 07.10s , -23d 29m 32.0s) | C | 60 | 19.2 | 18433 | 2026-04-17 05:29:44 | MASTER-OAFA | (16h 22m 02.40s , -23d 30m 03.3s) | C | 60 | 18.9 | 18509 | 2026-04-17 05:31:00 | MASTER-OAFA | (16h 22m 00.62s , -23d 29m 01.8s) | C | 60 | 18.9 | 18569 | 2026-04-17 05:31:00 | MASTER-OAFA | (16h 22m 00.62s , -23d 29m 01.9s) | C | 180 | 19.4 | Coadd 21141 | 2026-04-17 06:14:52 | MASTER-OAFA | (16h 22m 06.99s , -23d 29m 57.4s) | C | 60 | 19.3 | 21216 | 2026-04-17 06:16:08 | MASTER-OAFA | (16h 22m 01.94s , -23d 30m 56.8s) | C | 60 | 19.2 | 21290 | 2026-04-17 06:17:21 | MASTER-OAFA | (16h 22m 08.44s , -23d 30m 33.6s) | C | 60 | 19.3 | 21350 | 2026-04-17 06:17:21 | MASTER-OAFA | (16h 22m 08.45s , -23d 30m 33.6s) | C | 180 | 19.6 | Coadd 21365 | 2026-04-17 06:18:36 | MASTER-OAFA | (16h 22m 04.86s , -23d 29m 08.6s) | C | 60 | 19.2 | 21439 | 2026-04-17 06:19:50 | MASTER-OAFA | (16h 22m 04.87s , -23d 30m 41.6s) | C | 60 | 18.7 | 21515 | 2026-04-17 06:21:07 | MASTER-OAFA | (16h 22m 08.53s , -23d 29m 14.9s) | C | 60 | 19.4 | 74895 | 2026-04-17 21:10:46 | MASTER- | (16h 16m 30.79s , -20d 56m 12.9s) | C | 60 | 13.1 | 110797 | 2026-04-18 07:09:09 | MASTER-OAFA | (16h 17m 04.14s , -21d 44m 07.5s) | C | 60 | 19.4 | 110874 | 2026-04-18 07:10:25 | MASTER-OAFA | (16h 25m 34.38s , -21d 45m 27.4s) | C | 60 | 19.5 | 110950 | 2026-04-18 07:11:42 | MASTER-OAFA | (16h 16m 57.59s , -21d 43m 52.3s) | C | 60 | 19.5 | 111028 | 2026-04-18 07:12:59 | MASTER-OAFA | (16h 25m 40.71s , -21d 45m 23.9s) | C | 60 | 19.5 | 111103 | 2026-04-18 07:14:15 | MASTER-OAFA | (16h 16m 57.41s , -21d 45m 48.8s) | C | 60 | 19.5 | 119575 | 2026-04-18 09:34:26 | MASTER-OAGH | (16h 20m 52.34s , -22d 05m 17.1s) | C | 180 | 19.2 | 119575 | 2026-04-18 09:34:26 | MASTER-OAGH | (16h 22m 13.44s , -22d 38m 32.3s) | C | 180 | 19.2 | 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/44338. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42459] EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44337 SUBJECT: EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations DATE: 26/04/18 08:34:24 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> K. R. Ni (CCNU), Y. L. Wang (NAO, CAS; ICE, CSIC), Y. Q. Zhao (USTC; PRIC) and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260417a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wang et al., GCN 44325) at 2026-04-17 00:23:02 (UTC). The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.32 × 10^21 cm^-2, and a photon index of 0.78 (+/-0.27). The derived average unabsorbed 0.5-4 keV flux is 1.57 (+0.49/-0.39) × 10^(-10) erg/s/cm^2. Follow-up observation by the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-04-17T14:24:17 (UTC), ~14 hours after the WXT detection. The exposure time of the observation is around 3 ks. The on-ground analysis of the FXT data found an uncatalogued source at R.A. = 245.3232, DEC = -22.0249 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT light curve shows no significant variability. The average FXT 0.5-10 keV spectra can be fitted with an absorbed power-law with a free hydrogen column density of 1.54 (+/-0.4) × 10^21 cm^-2, and a photon index of 1.68 (+/-0.13). The derived average unabsorbed 0.5-10 keV flux is 7.79 (-0.76/+0.89) × 10^(-12) erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. We note that the X-ray position determined from EP/FXT observation is ~6.6 degrees away from that of GRB 260417A, which is RA = 252.0, Dec = -19.8 (J2000) with a statistical uncertainty of 3.4 degrees, as reported by the Fermi GBM team (GCN 44317). The detection in X-rays by WXT was ~13 minutes later than the reported GBM detection time of GRB 260417A. Therefore it is possible that GRB 260417A is the Gamma-ray counterpart of EP260417a. 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/44337. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42458] EP260416a: NOT tentative spectroscopic redshift of z =1.909
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44336 SUBJECT: EP260416a: NOT tentative spectroscopic redshift of z =1.909 DATE: 26/04/18 05:02:56 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He, X. Liu, Z.P. Zhu, S.Q. Jiang, J. An, D. Xu (NAOC), S.Y. Fu (HUST), J. P. U. Fynbo (DAWN/NBI), L. Fuglsang (NOT) report: We observed the optical counterpart (e.g., Ducoin et al., 44310) of EP260416a (Hu et al., GCN 44307) using the Nordic Optical Telescope (NOT), equipped with the ALFOSC camera and spectrograph. Observations started at 2026-04-17T03:56:49, and 2x1800 s spectra were obtained, covering the wavelength range 3800-9000 AA. The trace has quite low signal-to-noise. The continuum is throughout the wavelength range. We identify two relatively prominent absorption lines as Mg II doublet at z = 1.909. Based on it, other weak lines as due to Fe II 2600, Fe II 2374, 2383, Al II 1671 are consistent with this redshift. We tentatively conclude that this is the redshift of EP260416a. View this GCN Circular online at https://gcn.nasa.gov/circulars/44336. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42457] GRB 260418A: Fermi GBM Final Real-time Localization
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44335 SUBJECT: GRB 260418A: Fermi GBM Final Real-time Localization DATE: 26/04/18 05:00:17 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 04:49:35 UT on 18 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260418A (trigger 798180580.203356 / 260418201). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 140.6, Dec = 29.3 (J2000 degrees, equivalent to J2000 09h 22m, 29d 18'), with a statistical uncertainty of 18.1 degrees. The angle from the Fermi LAT boresight is 60.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418201/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418201/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260418201/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44335. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42456] EP260416a: GMG Optical Observation
by GCN Circulars 18 Apr '26

18 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44334 SUBJECT: EP260416a: GMG Optical Observation DATE: 26/04/18 01:02:53 GMT FROM: Rui-Zhi Li at Yunnan Observatories, CAS <liruizhi(a)ynao.ac.cn> R.-Z. Li, B.-T. Wang, F.-F. Song, J. Mao, J.-G Wang and B. Wang (YNAO, CAS) report: We observed the field of EP260416a (Hu et al., GCN 44307, T0 at 2026-04-16T05:29:32) using the GMG-2.4m telescope at the Lijiang Observatory. The observation began at 2026-04-17T15:58:05, about 34.48 hours after the trigger. The optical counterpart of EP260416a (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319; Zheng et al., GCN 44321; Martin-Carrillo et al., GCN 44328) was well detected. The preliminary analysis results are shown as follows: +---------------+------------+----------+--------------+----------------+ | Tmid-T0 [h] | Exp. [s] | Filter | Mag | 5-sigma U.L. | +===============+============+==========+==============+================+ | 34.50 | 180 | r | 20.91 ± 0.07 | 22.3 | +---------------+------------+----------+--------------+----------------+ The given magnitudes are derived based on calibration against Pan-STARRS1 field stars, and are not corrected for the expected Galactic foreground extinction, corresponding to a reddening of E(B-V) = 0.008 mag in the direction of the optical counterpart (Schlafly & Finkbeiner 2011). View this GCN Circular online at https://gcn.nasa.gov/circulars/44334. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42455] Fermi GRB 260417A: Global MASTER-Net observations report
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44333 SUBJECT: Fermi GRB 260417A: Global MASTER-Net observations report DATE: 26/04/17 21:30:34 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260417A ( Fermi GBM team, GCN 44317) errorbox 14312 sec after notice time and 14368 sec after trigger time at 2026-04-17 04:09:33 UT, with upper limit up to 19.8 mag. The observations began at zenith distance = 45 deg. The sun altitude is -68.6 deg. MASTER-OAGH robotic telescope located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) started inspect of the Fermi GRB 260417A errorbox 29871 sec after notice time and 29926 sec after trigger time at 2026-04-17 08:28:52 UT, with upper limit up to 19.2 mag. The observations began at zenith distance = 57 deg. The sun altitude is -45.3 deg. The galactic latitude b = 15 deg., longitude l = 0 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3255373 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 740 | 2026-04-17 00:21:24 | MASTER- | (16h 47m 57.82s , -19d 41m 25.5s) | C | 120 | 18.4 | 870 | 2026-04-17 00:23:35 | MASTER- | (16h 47m 57.86s , -19d 41m 30.5s) | C | 120 | 17.7 | 982 | 2026-04-17 00:25:57 | MASTER- | (16h 41m 27.04s , -19d 45m 05.5s) | C | 60 | 16.7 | 1061 | 2026-04-17 00:27:16 | MASTER- | (16h 38m 52.56s , -21d 03m 50.4s) | C | 60 | 17.4 | 1135 | 2026-04-17 00:28:30 | MASTER- | (16h 52m 35.98s , -19d 46m 01.7s) | C | 60 | 18.1 | 1886 | 2026-04-17 00:41:00 | MASTER- | (16h 48m 15.35s , -17d 09m 21.3s) | C | 60 | 16.8 | 1966 | 2026-04-17 00:42:21 | MASTER- | (16h 37m 18.54s , -17d 09m 12.5s) | C | 60 | 17.6 | 2807 | 2026-04-17 00:56:22 | MASTER- | (16h 41m 21.64s , -15d 53m 39.3s) | C | 60 | 17.0 | 2892 | 2026-04-17 00:57:46 | MASTER- | (16h 46m 18.69s , -23d 39m 40.4s) | C | 60 | 17.6 | 2970 | 2026-04-17 00:59:05 | MASTER- | (16h 52m 17.13s , -15d 52m 05.1s) | C | 60 | 18.4 | 4185 | 2026-04-17 01:19:20 | MASTER- | (16h 59m 10.68s , -17d 13m 44.6s) | C | 60 | 16.9 | 5170 | 2026-04-17 01:35:44 | MASTER- | (16h 46m 07.39s , -14d 39m 25.0s) | C | 60 | 17.8 | 5246 | 2026-04-17 01:37:01 | MASTER- | (16h 45m 26.27s , -25d 02m 33.4s) | C | 60 | 18.4 | 5924 | 2026-04-17 01:48:19 | MASTER- | (17h 06m 41.90s , -18d 34m 04.5s) | C | 60 | 18.1 | 14398 | 2026-04-17 04:09:33 | MASTER-OAFA | (16h 29m 03.49s , -19d 43m 08.6s) | C | 60 | 19.5 | 14458 | 2026-04-17 04:09:33 | MASTER-OAFA | (16h 29m 03.49s , -19d 43m 08.6s) | C | 180 | 19.8 | Coadd 14552 | 2026-04-17 04:12:06 | MASTER-OAFA | (16h 28m 56.24s , -19d 43m 02.7s) | C | 60 | 19.5 | 14779 | 2026-04-17 04:15:54 | MASTER-OAFA | (16h 38m 39.66s , -23d 31m 48.1s) | C | 60 | 19.5 | 14839 | 2026-04-17 04:15:54 | MASTER-OAFA | (16h 38m 39.65s , -23d 31m 48.1s) | C | 180 | 19.8 | Coadd 14933 | 2026-04-17 04:18:28 | MASTER-OAFA | (16h 38m 41.76s , -23d 32m 12.6s) | C | 60 | 19.5 | 15084 | 2026-04-17 04:20:58 | MASTER-OAFA | (16h 32m 49.20s , -21d 38m 08.4s) | C | 60 | 19.3 | 15144 | 2026-04-17 04:20:58 | MASTER-OAFA | (16h 32m 49.20s , -21d 38m 08.4s) | C | 180 | 19.8 | Coadd 15160 | 2026-04-17 04:22:14 | MASTER-OAFA | (16h 41m 19.99s , -21d 39m 40.4s) | C | 60 | 19.2 | 15220 | 2026-04-17 04:22:14 | MASTER-OAFA | (16h 41m 19.99s , -21d 39m 40.4s) | C | 180 | 19.6 | Coadd 15235 | 2026-04-17 04:23:29 | MASTER-OAFA | (16h 32m 50.94s , -21d 39m 03.8s) | C | 60 | 19.4 | 15310 | 2026-04-17 04:24:45 | MASTER-OAFA | (16h 41m 23.57s , -21d 37m 54.0s) | C | 60 | 19.3 | 15386 | 2026-04-17 04:26:00 | MASTER-OAFA | (16h 32m 46.94s , -21d 38m 37.5s) | C | 60 | 19.5 | 16850 | 2026-04-17 04:50:25 | MASTER-OAFA | (16h 28m 56.55s , -19d 42m 02.5s) | C | 60 | 19.3 | 16925 | 2026-04-17 04:51:40 | MASTER-OAFA | (16h 29m 02.98s , -19d 43m 01.7s) | C | 60 | 18.9 | 16985 | 2026-04-17 04:51:40 | MASTER-OAFA | (16h 29m 02.97s , -19d 43m 01.8s) | C | 180 | 18.1 | Coadd 16998 | 2026-04-17 04:52:53 | MASTER-OAFA | (16h 28m 57.16s , -19d 43m 59.2s) | C | 60 | 16.6 | 17301 | 2026-04-17 04:57:55 | MASTER-OAFA | (16h 38m 42.29s , -23d 30m 44.7s) | C | 60 | 19.3 | 17375 | 2026-04-17 04:59:10 | MASTER-OAFA | (16h 38m 36.15s , -23d 31m 34.8s) | C | 60 | 19.3 | 17435 | 2026-04-17 04:59:10 | MASTER-OAFA | (16h 38m 36.15s , -23d 31m 34.8s) | C | 180 | 19.7 | Coadd 17453 | 2026-04-17 05:00:27 | MASTER-OAFA | (16h 38m 35.44s , -23d 30m 32.8s) | C | 60 | 19.3 | 17754 | 2026-04-17 05:05:29 | MASTER-OAFA | (16h 41m 22.90s , -21d 36m 58.6s) | C | 60 | 19.2 | 17831 | 2026-04-17 05:06:46 | MASTER-OAFA | (16h 41m 22.86s , -21d 37m 58.9s) | C | 60 | 19.3 | 17891 | 2026-04-17 05:06:46 | MASTER-OAFA | (16h 41m 22.86s , -21d 37m 58.9s) | C | 180 | 19.2 | Coadd 17908 | 2026-04-17 05:08:03 | MASTER-OAFA | (16h 41m 25.06s , -21d 36m 28.2s) | C | 60 | 18.8 | 17984 | 2026-04-17 05:09:18 | MASTER-OAFA | (16h 32m 42.35s , -21d 36m 55.9s) | C | 60 | 18.8 | 18044 | 2026-04-17 05:09:18 | MASTER-OAFA | (16h 32m 42.34s , -21d 36m 55.9s) | C | 180 | 19.4 | Coadd 18060 | 2026-04-17 05:10:35 | MASTER-OAFA | (16h 32m 43.80s , -21d 35m 53.7s) | C | 60 | 18.6 | 18136 | 2026-04-17 05:11:50 | MASTER-OAFA | (16h 32m 49.52s , -21d 36m 53.1s) | C | 60 | 19.2 | 19599 | 2026-04-17 05:36:13 | MASTER-OAFA | (16h 28m 58.57s , -19d 41m 32.5s) | C | 60 | 14.5 | 19676 | 2026-04-17 05:37:31 | MASTER-OAFA | (16h 28m 58.56s , -19d 43m 06.6s) | C | 60 | 19.1 | 19736 | 2026-04-17 05:37:31 | MASTER-OAFA | (16h 28m 58.56s , -19d 43m 06.6s) | C | 180 | 19.5 | Coadd 19751 | 2026-04-17 05:38:46 | MASTER-OAFA | (16h 29m 01.46s , -19d 41m 18.4s) | C | 60 | 18.9 | 20056 | 2026-04-17 05:43:51 | MASTER-OAFA | (16h 38m 36.75s , -23d 31m 41.7s) | C | 60 | 18.9 | 20131 | 2026-04-17 05:45:06 | MASTER-OAFA | (16h 38m 41.80s , -23d 31m 32.2s) | C | 60 | 19.0 | 20191 | 2026-04-17 05:45:06 | MASTER-OAFA | (16h 38m 41.80s , -23d 31m 32.2s) | C | 180 | 19.3 | Coadd 20206 | 2026-04-17 05:46:21 | MASTER-OAFA | (16h 38m 38.94s , -23d 29m 52.9s) | C | 60 | 19.3 | 20509 | 2026-04-17 05:51:24 | MASTER-OAFA | (16h 41m 20.29s , -21d 35m 43.1s) | C | 60 | 14.1 | 20584 | 2026-04-17 05:52:39 | MASTER-OAFA | (16h 41m 24.57s , -21d 36m 41.8s) | C | 60 | 15.4 | 20659 | 2026-04-17 05:53:54 | MASTER-OAFA | (16h 41m 19.16s , -21d 37m 41.1s) | C | 60 | 18.4 | 20734 | 2026-04-17 05:55:09 | MASTER-OAFA | (16h 32m 48.78s , -21d 37m 05.4s) | C | 60 | 19.2 | 20794 | 2026-04-17 05:55:09 | MASTER-OAFA | (16h 32m 48.80s , -21d 37m 05.3s) | C | 180 | 18.4 | Coadd 20812 | 2026-04-17 05:56:27 | MASTER-OAFA | (16h 32m 45.89s , -21d 35m 38.2s) | C | 60 | 18.1 | 20888 | 2026-04-17 05:57:43 | MASTER-OAFA | (16h 32m 45.82s , -21d 37m 12.7s) | C | 60 | 16.2 | 22370 | 2026-04-17 06:22:25 | MASTER-OAFA | (16h 28m 53.83s , -19d 42m 20.8s) | C | 60 | 19.1 | 22445 | 2026-04-17 06:23:39 | MASTER-OAFA | (16h 28m 54.52s , -19d 41m 20.3s) | C | 60 | 18.6 | 22526 | 2026-04-17 06:25:01 | MASTER-OAFA | (16h 28m 59.87s , -19d 42m 20.3s) | C | 60 | 18.4 | 22604 | 2026-04-17 06:26:18 | MASTER-OAFA | (16h 38m 35.62s , -23d 31m 33.0s) | C | 60 | 17.6 | 22682 | 2026-04-17 06:27:36 | MASTER-OAFA | (16h 38m 43.18s , -23d 31m 05.7s) | C | 60 | 15.2 | 29957 | 2026-04-17 08:28:52 | MASTER-OAGH | (16h 36m 33.19s , -19d 47m 23.6s) | C | 60 | 18.9 | 29957 | 2026-04-17 08:28:52 | MASTER-OAGH | (16h 37m 50.69s , -20d 20m 45.0s) | C | 60 | 18.7 | 30029 | 2026-04-17 08:30:04 | MASTER-OAGH | (16h 44m 56.42s , -19d 48m 38.0s) | C | 60 | 18.8 | 30029 | 2026-04-17 08:30:04 | MASTER-OAGH | (16h 46m 13.73s , -20d 22m 00.2s) | C | 60 | 18.5 | 30167 | 2026-04-17 08:32:21 | MASTER-OAGH | (16h 52m 42.81s , -19d 47m 51.8s) | C | 60 | 18.7 | 30167 | 2026-04-17 08:32:21 | MASTER-OAGH | (16h 53m 59.94s , -20d 21m 15.2s) | C | 60 | 18.5 | 30238 | 2026-04-17 08:33:33 | MASTER-OAGH | (17h 01m 06.21s , -19d 49m 06.7s) | C | 60 | 18.6 | 30238 | 2026-04-17 08:33:33 | MASTER-OAGH | (17h 02m 23.12s , -20d 22m 30.8s) | C | 60 | 18.4 | 30368 | 2026-04-17 08:35:42 | MASTER-OAGH | (16h 41m 21.49s , -17d 53m 37.9s) | C | 60 | 19.2 | 30368 | 2026-04-17 08:35:42 | MASTER-OAGH | (16h 42m 38.31s , -18d 26m 58.0s) | C | 60 | 18.9 | 30439 | 2026-04-17 08:36:54 | MASTER-OAGH | (16h 49m 40.61s , -17d 54m 51.2s) | C | 60 | 19.0 | 30439 | 2026-04-17 08:36:54 | MASTER-OAGH | (16h 50m 57.29s , -18d 28m 12.0s) | C | 60 | 18.7 | 30579 | 2026-04-17 08:39:13 | MASTER-OAGH | (16h 36m 25.99s , -19d 46m 31.3s) | C | 60 | 19.0 | 30579 | 2026-04-17 08:39:13 | MASTER-OAGH | (16h 37m 43.64s , -20d 19m 50.6s) | C | 60 | 18.7 | 30651 | 2026-04-17 08:40:26 | MASTER-OAGH | (16h 45m 03.36s , -19d 47m 45.4s) | C | 60 | 18.9 | 30651 | 2026-04-17 08:40:26 | MASTER-OAGH | (16h 46m 20.86s , -20d 21m 05.7s) | C | 60 | 18.6 | 30789 | 2026-04-17 08:42:43 | MASTER-OAGH | (16h 52m 35.27s , -19d 46m 58.1s) | C | 60 | 18.6 | 30789 | 2026-04-17 08:42:43 | MASTER-OAGH | (16h 53m 52.67s , -20d 20m 19.7s) | C | 60 | 18.3 | 30860 | 2026-04-17 08:43:55 | MASTER-OAGH | (17h 01m 11.22s , -19d 48m 13.0s) | C | 60 | 18.6 | 30860 | 2026-04-17 08:43:55 | MASTER-OAGH | (17h 02m 28.42s , -20d 21m 35.4s) | C | 60 | 18.5 | 31050 | 2026-04-17 08:47:05 | MASTER-OAGH | (16h 41m 16.84s , -17d 52m 41.9s) | C | 60 | 19.1 | 31050 | 2026-04-17 08:47:05 | MASTER-OAGH | (16h 42m 34.04s , -18d 26m 00.5s) | C | 60 | 18.9 | 31122 | 2026-04-17 08:48:17 | MASTER-OAGH | (16h 49m 47.00s , -17d 53m 56.4s) | C | 60 | 19.1 | 31122 | 2026-04-17 08:48:17 | MASTER-OAGH | (16h 51m 04.07s , -18d 27m 15.7s) | C | 60 | 18.6 | 31260 | 2026-04-17 08:50:34 | MASTER-OAGH | (16h 36m 26.98s , -19d 46m 35.0s) | C | 60 | 19.0 | 31260 | 2026-04-17 08:50:34 | MASTER-OAGH | (16h 37m 44.96s , -20d 19m 52.8s) | C | 60 | 18.7 | 31331 | 2026-04-17 08:51:45 | MASTER-OAGH | (16h 45m 02.69s , -19d 47m 50.4s) | C | 60 | 18.8 | 31331 | 2026-04-17 08:51:46 | MASTER-OAGH | (16h 46m 20.56s , -20d 21m 09.2s) | C | 60 | 18.7 | 31468 | 2026-04-17 08:54:03 | MASTER-OAGH | (16h 52m 35.52s , -19d 47m 03.7s) | C | 60 | 18.9 | 31468 | 2026-04-17 08:54:03 | MASTER-OAGH | (16h 53m 53.26s , -20d 20m 23.4s) | C | 60 | 18.6 | 31539 | 2026-04-17 08:55:14 | MASTER-OAGH | (17h 01m 10.49s , -19d 48m 19.4s) | C | 60 | 18.5 | 31539 | 2026-04-17 08:55:14 | MASTER-OAGH | (17h 02m 28.05s , -20d 21m 39.9s) | C | 60 | 18.3 | 31730 | 2026-04-17 08:58:25 | MASTER-OAGH | (16h 41m 15.86s , -17d 52m 46.1s) | C | 60 | 19.1 | 31730 | 2026-04-17 08:58:25 | MASTER-OAGH | (16h 42m 33.35s , -18d 26m 03.0s) | C | 60 | 18.8 | 31802 | 2026-04-17 08:59:37 | MASTER-OAGH | (16h 49m 46.34s , -17d 54m 01.2s) | C | 60 | 19.1 | 31802 | 2026-04-17 08:59:37 | MASTER-OAGH | (16h 51m 03.72s , -18d 27m 18.9s) | C | 60 | 18.7 | 31941 | 2026-04-17 09:01:56 | MASTER-OAGH | (16h 36m 25.67s , -19d 46m 37.8s) | C | 60 | 19.1 | 31942 | 2026-04-17 09:01:56 | MASTER-OAGH | (16h 37m 44.02s , -20d 19m 54.4s) | C | 60 | 18.7 | 32013 | 2026-04-17 09:03:08 | MASTER-OAGH | (16h 45m 01.71s , -19d 47m 54.4s) | C | 60 | 18.9 | 32013 | 2026-04-17 09:03:08 | MASTER-OAGH | (16h 46m 19.93s , -20d 21m 11.7s) | C | 60 | 18.6 | 32203 | 2026-04-17 09:06:18 | MASTER-OAGH | (16h 52m 34.62s , -19d 47m 08.4s) | C | 60 | 18.8 | 32203 | 2026-04-17 09:06:18 | MASTER-OAGH | (16h 53m 52.79s , -20d 20m 26.6s) | C | 60 | 18.5 | 32275 | 2026-04-17 09:07:29 | MASTER-OAGH | (17h 01m 10.22s , -19d 48m 25.0s) | C | 60 | 18.6 | 32275 | 2026-04-17 09:07:30 | MASTER-OAGH | (17h 02m 28.23s , -20d 21m 43.8s) | C | 60 | 18.5 | 32413 | 2026-04-17 09:09:48 | MASTER-OAGH | (16h 41m 15.97s , -17d 52m 49.5s) | C | 60 | 19.1 | 32413 | 2026-04-17 09:09:48 | MASTER-OAGH | (16h 42m 33.77s , -18d 26m 05.1s) | C | 60 | 18.9 | 32485 | 2026-04-17 09:11:00 | MASTER-OAGH | (16h 49m 46.18s , -17d 54m 05.0s) | C | 60 | 18.8 | 32485 | 2026-04-17 09:11:00 | MASTER-OAGH | (16h 51m 03.92s , -18d 27m 21.4s) | C | 60 | 18.5 | 32556 | 2026-04-17 09:12:11 | MASTER-OAGH | (16h 36m 25.00s , -19d 48m 39.6s) | C | 60 | 18.7 | 32556 | 2026-04-17 09:12:11 | MASTER-OAGH | (16h 37m 43.65s , -20d 21m 55.1s) | C | 60 | 18.6 | 32628 | 2026-04-17 09:13:23 | MASTER-OAGH | (16h 45m 01.47s , -19d 48m 46.4s) | C | 60 | 18.6 | 32628 | 2026-04-17 09:13:23 | MASTER-OAGH | (16h 46m 20.00s , -20d 22m 02.6s) | C | 60 | 18.4 | 32700 | 2026-04-17 09:14:35 | MASTER-OAGH | (16h 48m 58.70s , -21d 42m 47.7s) | C | 60 | 18.8 | 32700 | 2026-04-17 09:14:35 | MASTER-OAGH | (16h 50m 17.92s , -22d 16m 05.3s) | C | 60 | 18.4 | 32771 | 2026-04-17 09:15:46 | MASTER-OAGH | (16h 57m 38.81s , -21d 41m 35.9s) | C | 60 | 18.5 | 32771 | 2026-04-17 09:15:46 | MASTER-OAGH | (16h 58m 57.88s , -22d 14m 54.5s) | C | 60 | 18.4 | 32844 | 2026-04-17 09:16:58 | MASTER-OAGH | (16h 52m 34.06s , -19d 48m 12.2s) | C | 60 | 18.9 | 32844 | 2026-04-17 09:16:58 | MASTER-OAGH | (16h 53m 52.48s , -20d 21m 29.1s) | C | 60 | 18.5 | 32915 | 2026-04-17 09:18:10 | MASTER-OAGH | (17h 01m 04.38s , -19d 47m 28.3s) | C | 60 | 18.6 | 32915 | 2026-04-17 09:18:10 | MASTER-OAGH | (17h 02m 22.65s , -20d 20m 46.1s) | C | 60 | 18.5 | 32987 | 2026-04-17 09:19:22 | MASTER-OAGH | (16h 32m 33.11s , -21d 42m 33.0s) | C | 60 | 18.7 | 32987 | 2026-04-17 09:19:22 | MASTER-OAGH | (16h 33m 52.63s , -22d 15m 48.3s) | C | 60 | 18.5 | 33060 | 2026-04-17 09:20:35 | MASTER-OAGH | (16h 41m 17.47s , -21d 42m 27.3s) | C | 60 | 18.9 | 33060 | 2026-04-17 09:20:35 | MASTER-OAGH | (16h 42m 36.89s , -22d 15m 43.2s) | C | 60 | 18.7 | 33131 | 2026-04-17 09:21:46 | MASTER-OAGH | (16h 41m 17.42s , -17d 53m 13.2s) | C | 60 | 18.9 | 33132 | 2026-04-17 09:21:46 | MASTER-OAGH | (16h 42m 35.50s , -18d 26m 27.3s) | C | 60 | 18.9 | 33203 | 2026-04-17 09:22:58 | MASTER-OAGH | (16h 49m 41.56s , -17d 54m 40.7s) | C | 60 | 19.0 | 33203 | 2026-04-17 09:22:58 | MASTER-OAGH | (16h 50m 59.53s , -18d 27m 55.6s) | C | 60 | 18.6 | 33275 | 2026-04-17 09:24:10 | MASTER-OAGH | (16h 36m 29.72s , -19d 46m 57.4s) | C | 60 | 18.9 | 33275 | 2026-04-17 09:24:10 | MASTER-OAGH | (16h 37m 48.54s , -20d 20m 11.6s) | C | 60 | 18.6 | 33411 | 2026-04-17 09:26:25 | MASTER-OAGH | (16h 44m 54.82s , -19d 46m 58.7s) | C | 60 | 18.8 | 33411 | 2026-04-17 09:26:25 | MASTER-OAGH | (16h 46m 13.61s , -20d 20m 13.5s) | C | 60 | 18.5 | 33482 | 2026-04-17 09:27:37 | MASTER-OAGH | (16h 49m 01.73s , -21d 42m 06.9s) | C | 60 | 18.6 | 33482 | 2026-04-17 09:27:37 | MASTER-OAGH | (16h 50m 21.20s , -22d 15m 23.1s) | C | 60 | 18.5 | 33623 | 2026-04-17 09:29:57 | MASTER-OAGH | (16h 57m 31.70s , -21d 41m 24.1s) | C | 60 | 18.4 | 33623 | 2026-04-17 09:29:57 | MASTER-OAGH | (16h 58m 51.05s , -22d 14m 41.2s) | C | 60 | 18.4 | 33707 | 2026-04-17 09:31:22 | MASTER-OAGH | (16h 52m 40.16s , -19d 48m 15.7s) | C | 60 | 18.3 | 33707 | 2026-04-17 09:31:22 | MASTER-OAGH | (16h 53m 58.91s , -20d 21m 31.2s) | C | 60 | 18.2 | 33829 | 2026-04-17 09:33:24 | MASTER-OAGH | (17h 01m 02.95s , -19d 47m 31.7s) | C | 60 | 18.3 | 33829 | 2026-04-17 09:33:24 | MASTER-OAGH | (17h 02m 21.63s , -20d 20m 48.3s) | C | 60 | 18.2 | 33903 | 2026-04-17 09:34:38 | MASTER-OAGH | (16h 32m 37.41s , -21d 41m 32.3s) | C | 60 | 18.8 | 33903 | 2026-04-17 09:34:38 | MASTER-OAGH | (16h 33m 57.28s , -22d 14m 46.5s) | C | 60 | 18.4 | 34040 | 2026-04-17 09:36:54 | MASTER-OAGH | (16h 41m 08.87s , -21d 40m 50.5s) | C | 60 | 18.8 | 34040 | 2026-04-17 09:36:54 | MASTER-OAGH | (16h 42m 28.69s , -22d 14m 05.1s) | C | 60 | 18.5 | 34111 | 2026-04-17 09:38:06 | MASTER-OAGH | (16h 41m 19.27s , -17d 53m 52.1s) | C | 60 | 19.0 | 34111 | 2026-04-17 09:38:06 | MASTER-OAGH | (16h 42m 37.77s , -18d 27m 05.1s) | C | 60 | 18.8 | 34250 | 2026-04-17 09:40:25 | MASTER-OAGH | (16h 49m 38.03s , -17d 53m 08.4s) | C | 60 | 19.0 | 34250 | 2026-04-17 09:40:25 | MASTER-OAGH | (16h 50m 56.55s , -18d 26m 22.3s) | C | 60 | 18.7 | 34323 | 2026-04-17 09:41:37 | MASTER-OAGH | (16h 48m 59.07s , -21d 42m 07.0s) | C | 60 | 18.8 | 34323 | 2026-04-17 09:41:37 | MASTER-OAGH | (16h 50m 18.95s , -22d 15m 22.2s) | C | 60 | 18.5 | 34452 | 2026-04-17 09:43:47 | MASTER-OAGH | (16h 57m 30.68s , -21d 41m 25.0s) | C | 60 | 18.4 | 34452 | 2026-04-17 09:43:47 | MASTER-OAGH | (16h 58m 50.48s , -22d 14m 40.9s) | C | 60 | 18.3 | 34525 | 2026-04-17 09:45:00 | MASTER-OAGH | (16h 32m 37.27s , -21d 41m 30.9s) | C | 60 | 18.5 | 34525 | 2026-04-17 09:45:00 | MASTER-OAGH | (16h 33m 57.36s , -22d 14m 44.6s) | C | 60 | 18.4 | 34669 | 2026-04-17 09:47:23 | MASTER-OAGH | (16h 41m 07.06s , -21d 40m 49.7s) | C | 60 | 18.9 | 34669 | 2026-04-17 09:47:23 | MASTER-OAGH | (16h 42m 27.11s , -22d 14m 03.8s) | C | 60 | 18.3 | 34743 | 2026-04-17 09:48:38 | MASTER-OAGH | (16h 57m 12.13s , -17d 55m 25.8s) | C | 60 | 18.5 | 34743 | 2026-04-17 09:48:38 | MASTER-OAGH | (16h 58m 30.72s , -18d 28m 39.2s) | C | 60 | 18.4 | 34814 | 2026-04-17 09:49:49 | MASTER-OAGH | (17h 05m 40.56s , -17d 55m 27.6s) | C | 60 | 18.4 | 34814 | 2026-04-17 09:49:49 | MASTER-OAGH | (17h 06m 59.07s , -18d 28m 41.9s) | C | 60 | 18.2 | 34890 | 2026-04-17 09:51:05 | MASTER-OAGH | (16h 47m 08.33s , -16d 00m 04.5s) | C | 60 | 18.8 | 34890 | 2026-04-17 09:51:05 | MASTER-OAGH | (16h 48m 26.55s , -16d 33m 16.5s) | C | 60 | 18.4 | 34962 | 2026-04-17 09:52:16 | MASTER-OAGH | (16h 55m 21.65s , -16d 01m 22.1s) | C | 60 | 18.8 | 34962 | 2026-04-17 09:52:16 | MASTER-OAGH | (16h 56m 39.82s , -16d 34m 34.4s) | C | 60 | 18.4 | 35100 | 2026-04-17 09:54:35 | MASTER-OAGH | (16h 48m 51.47s , -21d 41m 06.9s) | C | 60 | 18.7 | 35100 | 2026-04-17 09:54:35 | MASTER-OAGH | (16h 50m 11.53s , -22d 14m 21.4s) | C | 60 | 18.2 | 35172 | 2026-04-17 09:55:47 | MASTER-OAGH | (16h 57m 36.62s , -21d 42m 25.9s) | C | 60 | 18.3 | 35172 | 2026-04-17 09:55:47 | MASTER-OAGH | (16h 58m 56.66s , -22d 15m 40.8s) | C | 60 | 18.1 | 35365 | 2026-04-17 09:59:00 | MASTER-OAGH | (16h 32m 28.88s , -21d 40m 27.7s) | C | 60 | 18.6 | 35365 | 2026-04-17 09:59:00 | MASTER-OAGH | (16h 33m 49.14s , -22d 13m 40.8s) | C | 60 | 18.5 | 35437 | 2026-04-17 10:00:12 | MASTER-OAGH | (16h 41m 11.93s , -21d 41m 48.2s) | C | 60 | 18.8 | 35437 | 2026-04-17 10:00:12 | MASTER-OAGH | (16h 42m 32.17s , -22d 15m 01.2s) | C | 60 | 18.5 | 35572 | 2026-04-17 10:02:26 | MASTER-OAGH | (16h 57m 09.74s , -17d 53m 25.2s) | C | 60 | 18.3 | 35572 | 2026-04-17 10:02:26 | MASTER-OAGH | (16h 58m 28.54s , -18d 26m 37.5s) | C | 60 | 18.2 | 35645 | 2026-04-17 10:03:39 | MASTER-OAGH | (17h 05m 40.51s , -17d 54m 44.2s) | C | 60 | 18.5 | 35645 | 2026-04-17 10:03:39 | MASTER-OAGH | (17h 06m 59.29s , -18d 27m 57.1s) | C | 60 | 18.3 | 35783 | 2026-04-17 10:05:58 | MASTER-OAGH | (16h 47m 01.28s , -15d 59m 01.9s) | C | 60 | 18.6 | 35783 | 2026-04-17 10:05:58 | MASTER-OAGH | (16h 48m 19.78s , -16d 32m 13.0s) | C | 60 | 18.5 | 35855 | 2026-04-17 10:07:09 | MASTER-OAGH | (16h 55m 27.36s , -16d 00m 20.8s) | C | 60 | 18.7 | 35855 | 2026-04-17 10:07:10 | MASTER-OAGH | (16h 56m 45.83s , -16d 33m 32.1s) | C | 60 | 18.3 | 35994 | 2026-04-17 10:09:29 | MASTER-OAGH | (16h 48m 51.27s , -21d 41m 03.9s) | C | 60 | 18.2 | 35994 | 2026-04-17 10:09:29 | MASTER-OAGH | (16h 50m 11.66s , -22d 14m 17.1s) | C | 60 | 18.0 | 36066 | 2026-04-17 10:10:40 | MASTER-OAGH | (16h 57m 33.67s , -21d 42m 23.9s) | C | 60 | 18.3 | 36066 | 2026-04-17 10:10:40 | MASTER-OAGH | (16h 58m 54.02s , -22d 15m 37.6s) | C | 60 | 18.2 | 36205 | 2026-04-17 10:13:00 | MASTER-OAGH | (16h 32m 27.34s , -21d 40m 22.7s) | C | 60 | 18.7 | 36205 | 2026-04-17 10:13:00 | MASTER-OAGH | (16h 33m 47.73s , -22d 13m 35.0s) | C | 60 | 18.5 | 36277 | 2026-04-17 10:14:12 | MASTER-OAGH | (16h 41m 10.39s , -21d 41m 43.7s) | C | 60 | 18.6 | 36277 | 2026-04-17 10:14:12 | MASTER-OAGH | (16h 42m 30.81s , -22d 14m 56.0s) | C | 60 | 18.3 | 36415 | 2026-04-17 10:16:30 | MASTER-OAGH | (16h 57m 09.16s , -17d 53m 23.0s) | C | 60 | 18.4 | 36415 | 2026-04-17 10:16:30 | MASTER-OAGH | (16h 58m 28.16s , -18d 26m 34.5s) | C | 60 | 18.3 | 36487 | 2026-04-17 10:17:42 | MASTER-OAGH | (17h 05m 39.73s , -17d 54m 43.0s) | C | 60 | 18.4 | 36487 | 2026-04-17 10:17:42 | MASTER-OAGH | (17h 06m 58.72s , -18d 27m 55.2s) | C | 60 | 18.3 | 36629 | 2026-04-17 10:20:03 | MASTER-OAGH | (16h 46m 59.46s , -15d 58m 58.3s) | C | 60 | 18.8 | 36629 | 2026-04-17 10:20:03 | MASTER-OAGH | (16h 48m 18.03s , -16d 32m 09.1s) | C | 60 | 18.5 | 36703 | 2026-04-17 10:21:18 | MASTER-OAGH | (16h 55m 25.86s , -16d 00m 18.3s) | C | 60 | 18.7 | 36703 | 2026-04-17 10:21:18 | MASTER-OAGH | (16h 56m 44.47s , -16d 33m 29.4s) | C | 60 | 18.4 | 36837 | 2026-04-17 10:23:31 | MASTER-OAGH | (16h 48m 49.03s , -21d 41m 00.1s) | C | 60 | 18.6 | 36837 | 2026-04-17 10:23:31 | MASTER-OAGH | (16h 50m 09.50s , -22d 14m 13.3s) | C | 60 | 18.3 | 36908 | 2026-04-17 10:24:43 | MASTER-OAGH | (16h 57m 32.40s , -21d 42m 21.3s) | C | 60 | 18.5 | 36908 | 2026-04-17 10:24:43 | MASTER-OAGH | (16h 58m 52.86s , -22d 15m 34.6s) | C | 60 | 18.4 | 37066 | 2026-04-17 10:27:21 | MASTER-OAGH | (16h 32m 33.54s , -21d 38m 42.0s) | C | 60 | 18.5 | 37066 | 2026-04-17 10:27:21 | MASTER-OAGH | (16h 31m 24.17s , -21d 05m 13.0s) | C | 60 | 18.2 | 37142 | 2026-04-17 10:28:37 | MASTER-OAGH | (16h 41m 16.30s , -21d 40m 15.8s) | C | 60 | 18.6 | 37142 | 2026-04-17 10:28:37 | MASTER-OAGH | (16h 40m 07.03s , -21d 06m 46.5s) | C | 60 | 18.3 | 39314 | 2026-04-17 11:04:49 | MASTER-OAGH | (16h 57m 11.67s , -17d 51m 44.4s) | C | 60 | 18.1 | 39314 | 2026-04-17 11:04:49 | MASTER-OAGH | (16h 56m 03.06s , -17d 18m 22.3s) | C | 60 | 18.0 | 39387 | 2026-04-17 11:06:01 | MASTER-OAGH | (17h 05m 42.07s , -17d 53m 17.1s) | C | 60 | 18.4 | 39387 | 2026-04-17 11:06:01 | MASTER-OAGH | (17h 04m 33.48s , -17d 19m 55.0s) | C | 60 | 18.1 | 39525 | 2026-04-17 11:08:20 | MASTER-OAGH | (16h 47m 04.61s , -15d 57m 26.8s) | C | 60 | 18.8 | 39525 | 2026-04-17 11:08:20 | MASTER-OAGH | (16h 45m 56.53s , -15d 24m 06.0s) | C | 60 | 18.5 | 39607 | 2026-04-17 11:09:42 | MASTER-OAGH | (16h 55m 29.68s , -15d 58m 54.6s) | C | 60 | 18.8 | 39607 | 2026-04-17 11:09:42 | MASTER-OAGH | (16h 54m 21.53s , -15d 25m 33.9s) | C | 60 | 18.6 | 39730 | 2026-04-17 11:11:44 | MASTER-OAGH | (16h 46m 23.07s , -23d 33m 54.5s) | C | 60 | 19.1 | 39730 | 2026-04-17 11:11:44 | MASTER-OAGH | (16h 45m 14.38s , -23d 00m 36.8s) | C | 60 | 18.6 | 39806 | 2026-04-17 11:13:01 | MASTER-OAGH | (16h 54m 59.24s , -23d 35m 22.5s) | C | 60 | 18.7 | 39806 | 2026-04-17 11:13:01 | MASTER-OAGH | (16h 53m 50.49s , -23d 02m 04.7s) | C | 60 | 18.3 | 39939 | 2026-04-17 11:15:14 | MASTER-OAGH | (16h 57m 12.00s , -17d 51m 51.3s) | C | 60 | 18.4 | 39939 | 2026-04-17 11:15:14 | MASTER-OAGH | (16h 56m 04.23s , -17d 18m 33.2s) | C | 60 | 18.1 | 40010 | 2026-04-17 11:16:25 | MASTER-OAGH | (17h 05m 41.32s , -17d 53m 18.8s) | C | 60 | 18.5 | 40010 | 2026-04-17 11:16:25 | MASTER-OAGH | (17h 04m 33.46s , -17d 20m 00.4s) | C | 60 | 18.3 | 40764 | 2026-04-17 11:28:58 | MASTER-OAGH | (16h 47m 07.63s , -15d 58m 21.3s) | C | 60 | 19.0 | 40764 | 2026-04-17 11:28:59 | MASTER-OAGH | (16h 46m 00.12s , -15d 24m 52.6s) | C | 60 | 18.6 | 40836 | 2026-04-17 11:30:11 | MASTER-OAGH | (16h 55m 24.77s , -15d 57m 26.6s) | C | 60 | 19.0 | 40836 | 2026-04-17 11:30:11 | MASTER-OAGH | (16h 54m 17.25s , -15d 23m 58.6s) | C | 60 | 18.8 | 40975 | 2026-04-17 11:32:30 | MASTER-OAGH | (16h 46m 14.22s , -23d 32m 25.7s) | C | 60 | 19.2 | 40975 | 2026-04-17 11:32:30 | MASTER-OAGH | (16h 45m 06.50s , -22d 58m 59.6s) | C | 60 | 18.6 | 41047 | 2026-04-17 11:33:42 | MASTER-OAGH | (16h 55m 05.07s , -23d 33m 56.5s) | C | 60 | 18.8 | 41047 | 2026-04-17 11:33:42 | MASTER-OAGH | (16h 53m 57.29s , -23d 00m 30.7s) | C | 60 | 18.4 | 41777 | 2026-04-17 11:45:52 | MASTER-OAGH | (17h 05m 34.84s , -17d 51m 28.6s) | C | 60 | 18.4 | 41777 | 2026-04-17 11:45:52 | MASTER-OAGH | (17h 04m 27.36s , -17d 18m 01.6s) | C | 60 | 18.0 | 41849 | 2026-04-17 11:47:03 | MASTER-OAGH | (16h 47m 07.80s , -15d 57m 31.8s) | C | 60 | 18.5 | 41849 | 2026-04-17 11:47:03 | MASTER-OAGH | (16h 46m 00.89s , -15d 24m 06.5s) | C | 60 | 18.1 | 41978 | 2026-04-17 11:49:13 | MASTER-OAGH | (16h 55m 21.03s , -15d 57m 01.0s) | C | 60 | 18.0 | 41978 | 2026-04-17 11:49:13 | MASTER-OAGH | (16h 54m 13.96s , -15d 23m 37.2s) | C | 60 | 17.9 | 42051 | 2026-04-17 11:50:26 | MASTER-OAGH | (16h 46m 19.67s , -23d 33m 05.3s) | C | 60 | 18.7 | 42051 | 2026-04-17 11:50:26 | MASTER-OAGH | (16h 45m 12.17s , -22d 59m 44.3s) | C | 60 | 18.1 | 42239 | 2026-04-17 11:53:34 | MASTER-OAGH | (16h 54m 57.43s , -23d 32m 33.4s) | C | 60 | 18.3 | 42239 | 2026-04-17 11:53:34 | MASTER-OAGH | (16h 53m 49.94s , -22d 59m 13.4s) | C | 60 | 17.9 | 42464 | 2026-04-17 11:57:19 | MASTER-OAGH | (17h 05m 18.40s , -21d 40m 12.2s) | C | 60 | 17.9 | 42464 | 2026-04-17 11:57:19 | MASTER-OAGH | (17h 04m 11.01s , -21d 06m 52.2s) | C | 60 | 17.5 | 42673 | 2026-04-17 12:00:48 | MASTER-OAGH | (16h 46m 14.08s , -23d 31m 54.8s) | C | 60 | 17.4 | 42673 | 2026-04-17 12:00:48 | MASTER-OAGH | (16h 45m 06.83s , -22d 58m 35.4s) | C | 60 | 16.9 | 42747 | 2026-04-17 12:02:02 | MASTER-OAGH | (17h 08m 38.03s , -19d 47m 26.3s) | C | 60 | 17.6 | 42747 | 2026-04-17 12:02:02 | MASTER-OAGH | (17h 07m 31.18s , -19d 14m 06.8s) | C | 60 | 17.3 | 42892 | 2026-04-17 12:04:27 | MASTER-OAGH | (16h 54m 57.84s , -23d 32m 21.8s) | C | 60 | 17.3 | 42892 | 2026-04-17 12:04:27 | MASTER-OAGH | (16h 53m 50.53s , -22d 59m 02.3s) | C | 60 | 16.8 | 43102 | 2026-04-17 12:07:57 | MASTER-OAGH | (16h 39m 31.20s , -15d 55m 41.1s) | C | 60 | 16.8 | 43102 | 2026-04-17 12:07:57 | MASTER-OAGH | (16h 38m 25.45s , -15d 22m 21.9s) | C | 60 | 16.5 | 43180 | 2026-04-17 12:09:14 | MASTER-OAGH | (17h 05m 18.13s , -21d 39m 56.8s) | C | 60 | 17.0 | 43180 | 2026-04-17 12:09:14 | MASTER-OAGH | (17h 04m 11.09s , -21d 06m 38.0s) | C | 60 | 16.5 | 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/44333. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42454] Konus-Wind detection of GRB 260411B
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44332 SUBJECT: Konus-Wind detection of GRB 260411B DATE: 26/04/17 17:11:27 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The long-duration GRB 260411B (Fermi-GBM detection: The Fermi GBM team, GCN 44262, Pathak & Sonawane, GCN 44266; BALROG localization: Preis & Greiner, GCN 44263; SVOM-GRM detection: Wang et al., GCN 44268; Fermi-LAT detection: Longo et al., GCN 44277; GECAM-B detection: Zao et al., GCN 44285; Glowbug detection: Woolf et al., GCN 44312; IPN triangulation: Kozyrev et al., GCN 44329) triggered Konus-Wind at T0=29079.388 s UT (08:04:39.388). The burst light curve shows a multipeaked structure which starts at ~T0-8.7 s and has a total duration of ~55.6 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260411_T29079/ As observed by Konus-Wind, the burst had a fluence of 4.50(-0.50,+0.50)x10^-5 erg/cm2, and a 64-ms peak flux, measured from T0+1.440 s, of 1.15(-0.14,+0.14)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+49.408 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.62(-0.18,+0.19), the high energy photon index beta = -2.12(-0.19,+0.12), the peak energy Ep = 290(-38,+52) keV (chi2 = 82/98 dof). The spectrum near the maximum count rate (measured from T0+0.256 to T0+8.448 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.16(-0.15,+0.16), the high energy photon index beta = -2.19(-0.10,+0.08), the peak energy Ep = 248(-19,+23) keV (chi2 = 87/82 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/44332. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42453] GRB 260417B: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44331 SUBJECT: GRB 260417B: Fermi GBM Final Real-time Localization DATE: 26/04/17 15:54:29 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 15:43:55 UT on 17 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260417B (trigger 798133440.23068 / 260417655). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 264.8, Dec = -27.4 (J2000 degrees, equivalent to J2000 17h 39m, -27d 23'), with a statistical uncertainty of 8.4 degrees. The angle from the Fermi LAT boresight is 29.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417655/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417655/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417655/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44331. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42452] GRB 260417A: AstroSat CZTI detection
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44330 SUBJECT: GRB 260417A: AstroSat CZTI detection DATE: 26/04/17 15:23:26 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), Harsha K. H. (IUCAA), A. Goyal (IITB), A. Arya (IITB), G. Waratkar (Caltech/IITB), A. Vibhute (IUCAA), V. Bhalerao (IITB), D. Bhattacharya (Ashoka University/IUCAA), A. R. Rao (IUCAA/TIFR), and S. Vadawale (PRL) report on behalf of the AstroSat CZTI collaboration: Analysis of AstroSat CZTI data with the CIFT framework (Sharma et al., 2021, JApA, 42, 73) showed the detection of a long GRB 260417A which was also detected by Fermi GBM (Fermi GBM Team, GCN Circ. 44317). The source was clearly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve peaks at 2026-04-17 00:10:09.33 UTC. The measured peak count rate associated with the burst is 117 (+25, -18) counts/s above the background in the combined data of all quadrants, with a total of 1532 (+379, -412) counts. The local mean background count rate was 744 (+3, -3) counts/s. We measure a T90 of 29 (+3, -15) s from the cumulative Veto light curve. The source was also faintly detected in the 20-200 keV energy range. CZTI is built by a TIFR-led consortium of institutes across India, including VSSC, URSC, IUCAA, SAC, and PRL. The Indian Space Research Organisation funded, managed, and facilitated the project. CZTI GRB detections are reported regularly on the payload site at: http://astrosat.iucaa.in/czti/?q=grb View this GCN Circular online at https://gcn.nasa.gov/circulars/44330. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42451] IPN triangulation of GRB 260411B
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44329 SUBJECT: IPN triangulation of GRB 260411B DATE: 26/04/17 15:16:20 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A.S. Kozyrev, D.V. Golovin, M.L. Litvak, I.G. Mitrofanov, and A.B. Sanin on behalf of the HEND/Mars Odyssey team, A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, and T. Cline on behalf of the Konus-Wind team, A. Goldstein, M. S. Briggs, C. Wilson-Hodge, and E. Burns on behalf of the Fermi-GBM team, and W. Boynton, C. Fellows, K. Harshman, H. Enos, R. Starr, and A.S. Gardner on on behalf of the GRS-Odyssey GRB team, report: The long-duration GRB 260411B (Fermi-GBM detection: The Fermi GBM team, GCN 44262, Pathak & Sonawane, GCN 44266; BALROG localization: Preis & Greiner, GCN 44263; SVOM-GRM detection: Wang et al., GCN 44268; Fermi-LAT detection: Longo et al., GCN 44277; GECAM-B detection: Zao et al., GCN 44285; Glowbug detection: Woolf et al., GCN 44312) was detected by Fermi (GBM, LAT), Konus-Wind, SVOM (GRM), GECAM-B, Glowbug, and Mars-Odyssey (HEND) at about 29075 s UT (08:04:35). We have triangulated it to a preliminary, 3 sigma error box whose coordinates are: --------------------------------------------- RA(2000), deg Dec(2000), deg --------------------------------------------- Center: 85.558 (05h 42m 14s) +2.297 ( +2d 17' 50") Corners: 85.572 (05h 42m 17s) -0.527 ( +0d 31' 39") 85.610 (05h 42m 26s) -0.425 ( +0d 25' 29") 85.523 (05h 42m 05s) +5.509 ( +5d 30' 32") 85.486 (05h 41m 57s) +5.372 ( +5d 22' 20") --------------------------------------------- The error box area is 844 sq. arcmin, and its maximum dimension is 6.0 deg (the minimum one is 2.4 arcmin). The Sun distance was 65 deg. This localization may be improved. The OT reported by GOTO (GOTO26dam, GCN 44265) is inside the IPN box, strengthening the association of the OT and GRB 260411B. A triangulation map and HEALPix FITS file are posted at http://www.ioffe.ru/LEA/GRBs/GRB260411_T29079/IPN/ The HEALPix triangulation map is the multi-order HEALPix in units of probability density. The Konus-Wind time history and spectrum will be given in a forthcoming GCN Circular. View this GCN Circular online at https://gcn.nasa.gov/circulars/44329. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42450] EP260416a: LCO observations confirm end of flaring phase
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44328 SUBJECT: EP260416a: LCO observations confirm end of flaring phase DATE: 26/04/17 13:52:03 GMT FROM: Antonio Martin-Carrillo at UCD,Space Science Group <antonio.martin-carrillo(a)ucd.ie> A. Martin-Carrillo (UCD), L. Cotter (UCD), A. J. Levan (Radboud & Warwick), J. A. Chácon (PUC), D. B. Malesani (DAWN/NBI and Radboud), P. G. Jonker (Radboud) report on behalf of a larger collaboration: We observed the field of EP260416a (Hu et al., GCN Circ. 44307) with the LCO 1m telescope located at the McDonald Observatory (Texas, USA) equipped with the SINISTRO instrument. We obtained 6x300s exposures in the r band starting at 09:58:28.32 UT on the 17th of April 2026, approximately 28.48 hr after the initial trigger. In the stacked images the optical counterpart (Ducoin et al., GCN 44310, Li et al., GCN 44315, Hua et al., GCN 44318, Lee et al., GCN 44319, Zheng et al., GCN 44321) is well detected, and we measure an AB magnitude of r = 20.78 +/- 0.06, calibrated using nearby stars from the Pan-STARRS catalogue and not corrected for Galactic extinction. Compared to the previous observations made by Lee et al. (GCN Circ. 44319) the counterpart seems to have faded by approximately 0.18 AB mag in 5.6 hr. View this GCN Circular online at https://gcn.nasa.gov/circulars/44328. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42449] EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44327 SUBJECT: EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope DATE: 26/04/17 13:01:53 GMT FROM: Qiang Wang at Peking University <2501110280(a)stu.pku.edu.cn> Qiang Wang, Yacheng Kang, Ruize Shi, Xinmiao Zhao, and Fangzhou Ren (PKU) report on behalf of the PKU HiTF (High-energy Transients Follow-up) group: We observed the field of EP260324a (Wu et al., ATel 17728; T0 = 2026-03-24T07:04:20) using the PKU 60cm telescope at Xinglong Observatory, NAOC. Observations were conducted over multiple epochs between 2026 Mar 30 and Apr 11, corresponding to ~ 6.3–18.3 days after the EP-WXT detection, in the g, r, and i bands. In the stacked images, we clearly detect the optical counterpart in the difference images at a position consistent with that of ZTF26aapviim / AT2026hir (Anumarlapudi et al., GCN 44120; Mohan et al., GCN 44128; Kang et al., GCN 44156; Stein et al., GCN 44194; Globus et al., GCN 44196; Watson et al., GCN 44216). Preliminary photometry is calibrated against nearby Pan-STARRS field stars and reported in the AB magnitude system, without correction for Galactic extinction. Combining these data with our earlier observations on 2026 March 27 (Kang et al., GCN 44156), we find that the optical emission likely peaked at ~ 1 week after the EP trigger. Following the peak, we estimate the temporal decay using a simple power-law model, yielding indices of alpha_g ~ 1.13 and alpha_r ~ 0.93. The observation log is summarized below following the time sequence: | Date | Start_UT | T_mid − T0 (days) | Filter | Exposure (s) | Magnitude (AB) | | :--------: | :---------: | :---------------: | :----: | :----------: | :------------: | | 2026-03-30 | 14:03:01.11 | 6.30 | g | 2 * 600 | 17.40 +/- 0.03 | | 2026-03-30 | 14:25:47.00 | 6.31 | r | 2 * 600 | 17.62 +/- 0.04 | | 2026-03-31 | 13:25:47.93 | 7.27 | g | 2 * 600 | 17.31 +/- 0.03 | | 2026-03-31 | 13:48:41.86 | 7.29 | r | 2 * 600 | 17.64 +/- 0.04 | | 2026-03-31 | 14:11:31.90 | 7.34 | i | 12 * 600 | 17.87 +/- 0.03 | | 2026-04-06 | 14:02:29.94 | 13.30 | i | 4 * 600 | 18.11 +/- 0.03 | | 2026-04-06 | 14:45:34.47 | 13.34 | g | 4 * 600 | 17.97 +/- 0.03 | | 2026-04-07 | 13:49:09.03 | 14.30 | g | 4 * 600 | 18.06 +/- 0.03 | | 2026-04-07 | 14:34:49.59 | 14.33 | r | 4 * 600 | 18.27 +/- 0.04 | | 2026-04-10 | 14:10:56.15 | 17.31 | g | 5 * 600 | 18.42 +/- 0.03 | | 2026-04-10 | 15:04:02.07 | 17.35 | r | 5 * 600 | 18.54 +/- 0.04 | | 2026-04-11 | 13:05:42.64 | 18.28 | r | 6 * 600 | 18.57 +/- 0.05 | Further analysis and follow-up observations are ongoing. The PKU 60cm Telescope is operated by the Department of Astronomy, Peking University. The PKU HiTF group is dedicated to rapid follow-up observations of high-energy transients. View this GCN Circular online at https://gcn.nasa.gov/circulars/44327. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42448] EP260417a: TRT optical counterpart detection
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44326 SUBJECT: EP260417a: TRT optical counterpart detection DATE: 26/04/17 11:48:23 GMT FROM: L. B. He at NAOC <helb(a)bao.ac.cn> L.B. He (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), S.Q. Jiang, X. Liu, Z.P. Zhu, J. An, D. Xu (NAOC), S.Y. Fu (HUST) report: We observed the field of EP260417a detected by EP (Wang et. al, GCN 44325), using the 0.7-m telescope of the Thai Robotic Telescope network, located at Cerro Tololo Inter-American Observatory, Chile (TRT-CTO). We obtained a series of frames in the Sloan-r band. An uncatalogued source is detected within the EP/WXT error circle at coordinates R.A. (J2000) = 16:21:17.47 (245.3228), Dec. (J2000) = -22:01:26.31 (-22.0240) with an uncertainty of ~ 1.0 arcsec. The source had r = 20.30 +/- 0.03 mag at a median time of ~ 7.92 hr post-trigger, calibrated with Pan-STARRS1 DR2 and not corrected for Galactic extinction. No NEO would be at the above position at the observational time by checking MPC. We thus think the source could be the optical counterpart of EP260417a. View this GCN Circular online at https://gcn.nasa.gov/circulars/44326. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42447] EP260417a: Einstein Probe detection of an X-ray transient
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44325 SUBJECT: EP260417a: Einstein Probe detection of an X-ray transient DATE: 26/04/17 11:44:47 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y. L. Wang (NAO, CAS; ICE, CSIC), Y. Q. Zhao (USTC; PRIC), K. R. Ni (CCNU) and Z. X. Ling (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 EP260417a. The source was detected at 2026-04-17 00:23:02 (UTC). The WXT light curve showed a slow decreasing trend. The WXT position of the source is R.A. = 245.324 deg, DEC = -22.023 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). Preliminary spectral analysis with an absorbed power-law model gave a best-fit photon index of 0.75 (-0.38/+0.97) and an unconstrained hydrogen column density of ~2.3e-20. The unabsorbed 0.5-4 keV flux is 1.3(-0.3/+0.4)e-10 erg/s/cm^2. Quoted uncertainties are at 90% confidence level. A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP has been scheduled. 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/44325. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42446] EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44324 SUBJECT: EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations DATE: 26/04/17 09:10:30 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. F. Hu (PMO, CAS), J. Yang (ZZU), M. J. Liu, Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The X-ray transient EP260416a was detected by the Wide-field X-ray Telescople (WXT) on board the Einstein Probe (EP) mission (Hu et al., GCN 44307), and followed by several optical telescopes (Ducoin et al., GCN 44310, Li et al., GCN 44315, Hua et al., GCN 44318, Lee et al., GCN 44319, Zheng et al., GCN 44321). The refined analysis of the WXT data shows that the event was detected at the beginning of the observation starting at T0=2026-04-16T05:25:24 (UTC), and lasted for about 250 s before the observation was interrupted by the autonomous follow-up observation. The average WXT 0.5-4 keV spectrum can be fitted with an absorbed power law with a fixed Galactic hydrogen column density of 1.02 × 10^20 cm^-2, and a photon index of 1.0 +/- 0.8. The derived average unabsorbed 0.5-4 keV flux is 3.2 (-1.4, +2.7) × 10^(-10) erg/s/cm^2. The autonomous observation by the Follow-up X-ray Telescope (FXT) was performed at 2026-04-16T05:33:14 (UTC), about 8 minutes after T0. The exposure time of the observation is 2.4 ks. The on-ground analysis of the FXT data found an uncatalogued source at R.A. = 198.8351, DEC = 31.5972 (J2000) with an uncertainty of 10 arcsec (radius, 90% C.L. statistical and systematic). The FXT light curve shows no significant variability. The average FXT 0.5-10 keV spectra can be fitted with an absorbed power-law with a free hydrogen column density of 1.62 +/- 0.18 × 10^21 cm^-2, and a photon index of 2.14 +/- 0.08. The derived average unabsorbed 0.5-10 keV flux is 3.4 (-0.1, +0.1) × 10^(-10) erg/s/cm^2. No significant variability is observed from T0 to T0+6 ks. The uncertainties are at the 90% confidence level for the above parameters. Further FXT follow-up observations have been arranged. 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/44324. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42445] EP260417b: Einstein Probe detection of a fast X-ray transient
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44323 SUBJECT: EP260417b: Einstein Probe detection of a fast X-ray transient DATE: 26/04/17 08:45:52 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> K. R. Ni (CCNU), Y. Q. Zhao (USTC; PRIC), Y. L. Wang (NAO, CAS; ICE, CSIC) and Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: We report on the detection of a fast X-ray transient by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission, designated EP260417b. The ground analysis of the WXT data shows that the event started at T0 = 2026-04-17T01:21:04 (UTC) and lasted for around 230 s. The WXT position of the source is R.A. = 151.114 deg, DEC = 51.964 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP has been scheduled. 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/44323. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42444] EP-WXT trigger 01709259586: KAIT optical observations
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44322 SUBJECT: EP-WXT trigger 01709259586: KAIT optical observations DATE: 26/04/17 06:57:45 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, automatically responded to the EP-WXT trigger 01709259586 (Wu et al., GCN 44213) starting at 05:46 UT, about 27 minutes after the trigger. A set of B,V,R,I and clear (roughly R) filter images were obtained and lasted for ~1.5 hours. We performed photometry on the suggested flare star UCAC4 498-055345 and did not find obvious variability on its brightness at 0.1 mag level. View this GCN Circular online at https://gcn.nasa.gov/circulars/44322. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42443] EP260416a: KAIT optical upper limit
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44321 SUBJECT: EP260416a: KAIT optical upper limit DATE: 26/04/17 06:10:43 GMT FROM: Weikang Zheng at UC Berkeley <weikang(a)berkeley.edu> WeiKang Zheng (UCB), Xuhui Han (NAOC), Pinpin Zhang (NAOC) and Alexei V. Filippenko (UCB) report on behalf of the KAIT GRB team: The 0.76-m Katzman Automatic Imaging Telescope (KAIT), located at Lick Observatory, observed the field of EP260416a (Hu et al., GCN 44307) starting at 05:36, Apr 16 UT, about 7.2 minutes after the burst. A set of 20s, 40s and 60s clear (roughly R) filter images were obtained. In our coadd image, we did not detect the OT (Ducoin et al., GCN 44310; Li et al., GCN 44315; Hua et al., GCN 44318; Lee et al., GCN 44319) down to a limiting mag of 21.0 mag (Vega) at a mid-time of 1.3 hours after the burst. Our result is consistent with the OT reported at a fatiner magnitude by COLIBRÍ at a similar time (Ducoin et al., GCN 44310). View this GCN Circular online at https://gcn.nasa.gov/circulars/44321. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42442] GRB 260414A: Insight-HXMT/HE detection
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44320 SUBJECT: GRB 260414A: Insight-HXMT/HE detection DATE: 26/04/17 05:57:10 GMT FROM: guohx(a)ihep.ac.cn Hao-Xuan Guo, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-14T06:32:07.400 (T0), Insight-HXMT/HE detected a long burst, GRB 260414A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44293) and Glowbug (C.C. Cheung et al., GCN #44297). The Insight-HXMT/HE light curve mainly consists of multiple pulses with a total duration (T90) of 34.5 +7/-11 s. The 1s peak rate, measured from T0+0.25 s, is 818 cnts/sec. Insight-HXMT/HE detected a total of 6318 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260414A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/44320. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42441] EP260416a: COLIBRÍ confirmation of the optical rebrightening
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44319 SUBJECT: EP260416a: COLIBRÍ confirmation of the optical rebrightening DATE: 26/04/17 05:36:55 GMT FROM: William H. Lee at UNAM <wlee(a)astro.unam.mx> William H. Lee (UNAM), Stéphane Basa (UAR Pytheas), Rosa L. Becerra (UNAM), Alan M. Watson (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), 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), Diego López-Cámara (UNAM), Nikos Mandarakas (LAM), Enrique Moreno Méndez (UNAM), Francesco Magnani (CPPM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM) and Antonio de Ugarte Postigo (LAM) report: We reimaged the field of the EP260416a (Hu et al., GCN Circ. 44307) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-04-17 04:20 to 04:43 UTC (from 22.85 to 23.24 hours after the trigger) and obtained 4/11/3/18 minutes of exposure in the g/r/i/z filters, respectively. The data were reduced and coadded with 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. The candidate reported previously by Ducoin et al. (GCN Circ. 44310) is clearly detected in all our filters with preliminary magnitudes of: r = 20.60 +/- 0.02 z = 19.88 +/- 0.02 Our values confirm the rebrightening reported by the WFST Collaboration (Hua et al. GCN Circ. 44318), and suggests a photo-z <2.5 (90% conf.). 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/44319. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42440] EP260416a: WFST optical observations and rebrightening
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44318 SUBJECT: EP260416a: WFST optical observations and rebrightening DATE: 26/04/17 03:55:29 GMT FROM: ylhua(a)pmo.ac.cn Yan-Long Hua, Ding-Fang Hu, Jin-Jun Geng, Xue-Feng Wu, Hui Sun, Ye Li, Zhi-Ping Jin, Tian-Rui Sun, Yi-Fang Liang, Yuan-Tai Yang, Ji-An Jiang report on behalf of the WFST team: Following the detection of EP260416a by Einstein Probe (Hu et al., GCN 44307). We performed follow-up observations using the Wide Field Survey Telescope (WFST Collaboration; arXiv:2306.07590) at the Lenghu Astronomical Observation Base in Qinghai Province, China. Observations in the r-band began at 2026-04-16T17:54:47 UTC, approximately 12.4208 hours after the trigger. The optical candidate reported by COLIBRÍ (Ducoin et al., GCN 44310) and SVOM/VT (Li et al., GCN 44315) was clearly detected in images in r band and showed significant rebrightening. The preliminary measurements are given in the AB magnitudes and are not corrected for Galactic extinction: r = 20.27 ± 0.01 (AB) We encourage further follow-up observations. We thank the WFST staff for supporting these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44318. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42439] GRB 260417A: Fermi GBM Final Real-time Localization
by GCN Circulars 17 Apr '26

17 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44317 SUBJECT: GRB 260417A: Fermi GBM Final Real-time Localization DATE: 26/04/17 00:21:39 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 00:10:05 UT on 17 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260417A (trigger 798077410.198084 / 260417007). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 252.0, Dec = -19.8 (J2000 degrees, equivalent to J2000 16h 48m, -19d 48'), with a statistical uncertainty of 3.4 degrees. The angle from the Fermi LAT boresight is 81.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417007/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417007/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260417007/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44317. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42438] GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44316 SUBJECT: GOTO26djh/AT2026jpw: ZTSh R,I bands observations of the transient DATE: 26/04/16 15:00:15 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), V. Rumyantsev (CrAO), A. Pozanenko (IKI), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We performed optical observations of the field of AT2026jpw (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303; Moskvitin and Spiridonova, GCN 44304; Xu et al., GCN 44305; The COLIBRÍ team, GCN 44306; Sosnovskij et al., GCN 44309; Ma et at., GCN 44314) in the R- and I-bands with the Shajn 2.6-meter telescope (ZTSh) of the Crimean Astrophysical Observatory (CrAO). The observations began on 2026-04-15 19:17 UT, i.e. ~1.84 days since GOTO detection. The series of 15x120s exposures were taken in the R-band and 21x120s exposures were taken in the I-band. The optical counterpart is clearly detected. The preliminary photometry and observation details are provided below: Date UT start t-T0 Exp. Filter OT Err. UL(3sigma) (mid, days) (s) 2026-04-15 19:17:42 1.84388 15x120 R 21.49 0.05 23.6 2026-04-15 19:56:05 1.87469 21x120 I 21.59 0.08 23.3 The photometry is calibrated using nearby stars from USNO-B1.0 (see Moskvitin and Spiridonova, GCN 44304) and has not been corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44316. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42437] EP260416a: SVOM/VT optical observation
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44315 SUBJECT: EP260416a: SVOM/VT optical observation DATE: 26/04/16 14:48:47 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, L. P. Xin, Y. L. Qiu, 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) report on behalf of the SVOM/VT team. SVOM/VT performed a ToO observation of EP260416a, triggered by Einstein Probe (Hu et al., GCN 44307). The observation started at 2026-04-16T06:17:46 UTC, i.e., approximately 46.8 minutes in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical candidate reported by COLIBRÍ (Ducoin et al., GCN 44310) was clearly detected in stack images in both channels. The preliminary measurements are given in the AB magnitudes and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 1.93 hr VT_B 99*50 sec 23.36+/-0.25 mag 1.93 hr VT_R 97*50 sec 22.91+/-0.20 mag 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/44315. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42436] GOTO26djh/AT2026jpw: SVOM/VT optical observation
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44314 SUBJECT: GOTO26djh/AT2026jpw: SVOM/VT optical observation DATE: 26/04/16 13:55:26 GMT FROM: Yinuo Ma <mayn(a)bao.ac.cn> Y. N. Ma, H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, Z. H. Yao, J. R. Xu, 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), W. L. Zhang (PMO), W. K. Zheng (UCB) report on behalf of the SVOM/VT team. SVOM/VT performed a Target of Opportunity observation of the transient GOTO26djh/AT2026jpw detected by GOTO (O'Neill et al., GCN 44301). SVOM/VT began observing the field at 2026-04-16T06:11:26 UTC, 54.9 hours after the trigger, in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. With X-band data available, the OT (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303; Moskvitin & Spiridonova, GCN 44304; Xu et al., GCN 44305; Sosnovskij et al., GCN 44306; Méndez et al., GCN 44309) was clearly detected in VT_R band. The magnitude is: mid time (h) | exposure time (s) | band | mag (AB) | mag err -------------|-------------------|------|----------|-------- 54.918 | 3*70 | VT_R | 21.5 | 0.2 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/44314. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42435] GRB 260415B: Glowbug gamma-ray detection
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44313 SUBJECT: GRB 260415B: Glowbug gamma-ray detection DATE: 26/04/16 13:41:43 GMT FROM: Richard S. Woolf at US Naval Research Laboratory <richard.s.woolf.civ(a)us.navy.mil> R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260415B, which was also detected by Fermi GBM (GCN 44300), NuSTAR (GCN 44302), and CALET (Trigger ID No. 1460255329). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-04-15 02:25:27.664 with a duration of 272.2 s and a total significance of about 33.0 sigma. The light curve comprises an initial peak at T0, followed by secondary emission, exhibiting four distinct peaks, spanning from ~T0+200s to ~T0+272s. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44313. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42434] GRB 260411B: Glowbug gamma-ray detection
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44312 SUBJECT: GRB 260411B: Glowbug gamma-ray detection DATE: 26/04/16 13:36:13 GMT FROM: Richard S. Woolf at US Naval Research Laboratory <richard.s.woolf.civ(a)us.navy.mil> R. Woolf, C.C. Cheung, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260411B, which was also detected by Fermi GBM (GCN 44262, 44266), SVOM/GRM (GCN 44268), Fermi LAT (GCN 44277), and GECAM (GCN 44285). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-04-11 08:04:43.568 with a duration of 3.1 s and a total significance of about 22.6 sigma. At the time of the detection, the ISS was entering a high background region and Glowbug captured the second, brighter peak visible in the GBM lightcurve. The initial, fainter peak near the GBM T0 may be detected by Glowbug at low significance. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44312. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42433] GRB 260415A: Insight-HXMT/HE detection
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44311 SUBJECT: GRB 260415A: Insight-HXMT/HE detection DATE: 26/04/16 12:39:40 GMT FROM: renyz16607(a)163.com Yang-Zhao Ren, Chen-Wei Wang, Cheng-Kui Li, Shao-Lin Xiong, and Chao Zheng (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-15T04:44:27.200 (T0), Insight-HXMT/HE detected a long burst, GRB 260415A, which is also detected by Fermi/GBM (Fermi GBM team, GCN #44299). The Insight-HXMT/HE light curve mainly consists of multi-pulses with T90 of 39 +3/-2 s. The 1s peak rate, measured from T0+0.75 s, is 2212 cnts/sec. Insight-HXMT/HE detected a total of 27305 counts from this burst. The Insight-HXMT /HE light curve can be found here: https://www.bursthub.cn/admin/static/hxmtgrb260415A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/44311. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42432] EP260416a: COLIBRÍ optical counterpart candidate
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44310 SUBJECT: EP260416a: COLIBRÍ optical counterpart candidate DATE: 26/04/16 09:22:19 GMT FROM: J.-G. Ducoin at CPPM <ducoin(a)cppm.in2p3.fr> Jean-Grégoire Ducoin (CPPM), Enrique Moreno Méndez (UNAM), 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), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (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), 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 the EP260416a (Hu et al., GCN Circ. 44307) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-04-16 05:36:04 to 06:51:03 UTC (from 0.11 to 1.36 hours after the trigger) and obtained 60 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with both the COLIBRÍ and COLIBRÍ ASU pipeline and analysed with STDWeb/STDPipe (Karpov 2025). 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 r band, we detect a source revealed by image subtraction using Legacy Survey as template and consistent with the FXT 20 arcsec error circle (Hu et al., GCN Circ. 44307) at: RA(J2000) = 13:15:20.49 = 198.8354 degrees Dec(J2000) = +31:35:49.4 = 31.5971 degrees with an uncertainty of 0.5 arcsec. The preliminary magnitude derived for that source is: r = 23.4 +/- 0.2 z > 22.8 (3 sigma-limit) The position of the source is coincident with a galaxy in the Legacy Survey catalog (Dey et al. 2019) with a photometry of g = 24.01 +/- 0.17 r = 24.05 +/- 0.30 z = 23.35 +/- 0.34. In our observations, we find evidence for brighter emission in the r band relative to the catalog value, suggesting tentative excess emission relative to the cataloged galaxy flux. However, the non-detection in the z band, combined with the lack of clear evidence for variability, prevents a firm confirmation . 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/44310. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42431] COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44309 SUBJECT: COLIBRI optical observations of the transient GOTO26djh/AT2026jpw DATE: 26/04/16 06:26:13 GMT FROM: enriquemm(a)astro.unam.mx GOTO26djh/AT2026jpw: COLIBRÍ optical observations. Enrique Moreno Méndez (UNAM), Jean-Grégoire Ducoin (CPPM), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Ramandeep Gill (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), Damien Dornic (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), 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 the orphan afterglow candidate GOTO26djh/AT2026jpw reported by O'Neill et al., (GCN Circ. 44301) and also observed by Corcoran et al. (GCN Circ. 44303), Moskvitin et al. (GCN Circ. 44304), Xu et al. (GCN Circ. 44305), and Sosnovskij et al. (GCN Circ. 44306) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-04-16 03:47:39 to 04:44:41 (from 52.50 to 53.45 hours after the trigger) and obtained 15/15/15/45 minutes of simultaneous exposure in the g/r/i/z filters. The data were reduced and coadded with the 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. We detected the optical counterpart reported by D. O'Neill et al., GCN Circ. 44301 at preliminary magnitudes of: g = 22.51 +/- 0.06 r = 22.10 +/- 0.06 i = 21.87 +/- 0.08 z = 21.55 +/- 0.07 Comparing our values with the reported by NOT (Corcoran et al. GCN Circ. 44303), we estimate an optical decay alpha 1.6. Moreover, the detection in the four filters suggests a photo-z < 2.7 using typical IGM absorption. Further observations and analysis 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/44309. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42430] EP260416a: Global MASTER-Net observations report
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44308 SUBJECT: EP260416a: Global MASTER-Net observations report DATE: 26/04/16 06:18:42 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) was pointed to the EP260416a ( EP Team et al., GCN 44307) errorbox 436 sec after trigger time at 2026-04-16 05:36:48 UT, with upper limit up to 20.7 mag. The observations began at zenith distance = 66 deg. The sun altitude is -64.5 deg. The galactic latitude b = 83 deg., longitude l = 71 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3254155 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 482 | 2026-04-16 05:36:48 | MASTER-OAFA | (13h 14m 35.21s , +31d 29m 47.4s) | C | 90 | 20.1 | 602 | 2026-04-16 05:36:48 | MASTER-OAFA | (13h 14m 35.21s , +31d 29m 47.4s) | C | 330 | 20.7 | Coadd 588 | 2026-04-16 05:38:25 | MASTER-OAFA | (13h 14m 34.93s , +31d 29m 48.7s) | C | 110 | 20.2 | 714 | 2026-04-16 05:40:21 | MASTER-OAFA | (13h 14m 34.60s , +31d 29m 49.8s) | C | 130 | 20.2 | 865 | 2026-04-16 05:42:37 | MASTER-OAFA | (13h 14m 34.22s , +31d 29m 50.9s) | C | 160 | 20.2 | 925 | 2026-04-16 05:42:37 | MASTER-OAFA | (13h 14m 34.22s , +31d 29m 50.8s) | C | 280 | 20.4 | Coadd 981 | 2026-04-16 05:45:23 | MASTER-OAFA | (13h 14m 33.92s , +31d 29m 51.3s) | C | 60 | 20.0 | 1047 | 2026-04-16 05:46:28 | MASTER-OAFA | (13h 14m 33.76s , +31d 29m 51.3s) | C | 60 | 20.0 | 1112 | 2026-04-16 05:47:34 | MASTER-OAFA | (13h 14m 33.59s , +31d 29m 51.5s) | C | 60 | 20.0 | 1172 | 2026-04-16 05:47:34 | MASTER-OAFA | (13h 14m 33.59s , +31d 29m 51.5s) | C | 180 | 20.3 | Coadd 1178 | 2026-04-16 05:48:40 | MASTER-OAFA | (13h 14m 33.42s , +31d 29m 51.9s) | C | 60 | 20.0 | 1244 | 2026-04-16 05:49:45 | MASTER-OAFA | (13h 14m 33.23s , +31d 29m 52.2s) | C | 60 | 20.0 | 1309 | 2026-04-16 05:50:51 | MASTER-OAFA | (13h 14m 33.04s , +31d 29m 52.8s) | C | 60 | 20.0 | 1369 | 2026-04-16 05:50:51 | MASTER-OAFA | (13h 14m 33.04s , +31d 29m 52.8s) | C | 180 | 20.3 | Coadd 1375 | 2026-04-16 05:51:57 | MASTER-OAFA | (13h 14m 32.87s , +31d 29m 52.7s) | C | 60 | 20.0 | 1441 | 2026-04-16 05:53:02 | MASTER-OAFA | (13h 14m 32.72s , +31d 29m 52.6s) | C | 60 | 20.0 | 1506 | 2026-04-16 05:54:08 | MASTER-OAFA | (13h 14m 32.54s , +31d 29m 52.7s) | C | 60 | 20.0 | 1566 | 2026-04-16 05:54:08 | MASTER-OAFA | (13h 14m 32.54s , +31d 29m 52.7s) | C | 180 | 20.4 | Coadd 1573 | 2026-04-16 05:55:15 | MASTER-OAFA | (13h 14m 32.35s , +31d 29m 52.6s) | C | 60 | 20.0 | 1639 | 2026-04-16 05:56:20 | MASTER-OAFA | (13h 14m 32.16s , +31d 29m 52.8s) | C | 60 | 20.0 | 1704 | 2026-04-16 05:57:26 | MASTER-OAFA | (13h 14m 32.01s , +31d 29m 52.6s) | C | 60 | 20.0 | 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/44308. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42429] EP260416a: Einstein Probe detection of an X-ray transient
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44307 SUBJECT: EP260416a: Einstein Probe detection of an X-ray transient DATE: 26/04/16 06:15:34 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. F. Hu (PMO, CAS), J. Yang (ZZU), M. J. Liu, Y. Liu (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 EP260416a. The transient triggered EP-WXT (ID: 01709260236) at 2026-04-16T05:29:32 (UTC). The WXT position of the source is R.A. = 198.836 deg, DEC = 31.590 deg (J2000) with an uncertainty of 3 arcmin in radius (90% C.L. statistical and systematic). A follow-up observation with the Follow-up X-ray Telescope (FXT) was performed automatically. Within the WXT error circle, an uncatalogued X-ray source was detected at R.A. = 198.8353 deg, DEC = 31.5986 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/44307. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42428] GOTO26djh/AT2026jpw : MASTER OT observation
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44306 SUBJECT: GOTO26djh/AT2026jpw : MASTER OT observation DATE: 26/04/16 01:58:03 GMT FROM: Vladimir Lipunov at Moscow State U/Krylov Obs <lipunov(a)xray.sai.msu.ru> A.Sosnovskij, V.Lipunov, A.Kuznetsov, E.Gorbovskoy, I.Panchenko, P.Balanutsa, G.Antipov, N.Tiurina, V.Senik, A.Chasovnikov, Ya.Kechin, V.Topolev, D.Vlasenko, A.Sankovich, I.Gorbunov (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), D.Buckley (SAAO), A. Gabovich (Blagoveschensk Educational StateUniversity) R.Rebolo (The Instituto de Astrofisica de Canarias), 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) MASTER-Tavrida robotic telescope of MASTER Global Robotic Net [1-4] started GOTO26djh/AT2026jpw (discovered by GOTO O'Neill et al., GCN 44301, also observed by NOT (Corcoran et al., GCN 44303) and Zeiss-1000 at SAO RAS (Moskvitin et al. GCN 44304) observations at 2026-04-15 23:10:27UT. There is optical transient at summary MASTER image (2520s exposition, mlim=22.2m) with unfiltered m_OT~21.5+-0.6m , calibrated by Pan-STARRs stars in our field. MASTER images are available on request. Observation and reduction will continue. [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/44306. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42427] GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44305 SUBJECT: GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection DATE: 26/04/16 01:54:19 GMT FROM: Dong Xu at NAOC/CAS <dxu(a)nao.cas.cn> D. Xu (NAOC), B. P. Gompertz (U. Birmingham), S.Q. Jiang (NAOC) report on behalf of a large group: We performed a ToO observation at the location of GOTO26djh/AT2026jpw, a candidate orphan GRB afterglow (O'Neill et al., GCN 44301) with the Follow-up X-ray Telescope (FXT) onboard the Einstein Probe (EP) mission. The observation started at 18:49:01 on 2026-04-15 UT with a total exposure time of ~3000 s. An uncatalogued X-ray source, with a flux of ~ 1.7 x 10^-13 erg/cm^2/s (0.5-10 keV; observed), is detected at coordinates R.A.(J2000) = 13:22:13.34 Dec.(J2000) = +37:02:26.88 with an uncertainty of 15 arcsec, being consistent with the location of GOTO26djh/AT2026jpw, confirming it's the soft X-ray counterpart of GOTO26djh/AT2026jpw. The X-ray counterpart detection at ~ 3 days since the event happening favors its nature of an afterglow of a high-energy burst. Further EP-FXT observations are scheduled. View this GCN Circular online at https://gcn.nasa.gov/circulars/44305. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42426] GOTO26djh/AT2026jpw transient: SAO RAS optical observations
by GCN Circulars 16 Apr '26

16 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44304 SUBJECT: GOTO26djh/AT2026jpw transient: SAO RAS optical observations DATE: 26/04/16 00:39:58 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. S. Moskvitin and O. I. Spiridonova (SAO RAS) report on behalf of GRB follow-up team. We observed the field of the fast-fading transient GOTO26djh/AT2026jpw (O'Neill et al., GCN 44301) with the Zeiss-1000 1m telescope of the SAO RAS on April 15/16 night. We obtained two series of images in Rc band. The OT (O'Neill et al., GCN 44301; Corcoran et al., GCN 44303) is clearly detected in the stacked images with the following brightness. Date UT start t-T0 Exp. Filter OT Err. UL (mid,days) (n*s) (3sigma) 2026-04-15T19:30:44 1.87945 8*300 Rc 21.6 +/- 0.1 23.3 2026-04-15T22:01:13 1.97747 13*300 Rc 22.0 +/- 0.1 23.8 This preliminary photometry is based on nearby stars from the USNO-B1 catalogue (R2 magnitudes) and is not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44304. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42425] NOT r-band observations of the transient GOTO26djh/AT2026jpw
by GCN Circulars 15 Apr '26

15 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44303 SUBJECT: NOT r-band observations of the transient GOTO26djh/AT2026jpw DATE: 26/04/15 23:26:03 GMT FROM: Laura Cotter at University College Dublin <laura.cotter(a)ucdconnect.ie> G. Corcoran (UCD), A. de Ugarte Postigo (LAM), L. Cotter (UCD), A. Martin-Carrillo (UCD), B. P. Gompertz (Birmingham), D. Xu (NAOC), D. B. Malesani (DAWN/NBI and Radboud), N. Pyykkinen (NOT and UTU), report on behalf of a larger collaboration: We observed the field of the transient GOTO26djh/AT2026jpw (O'Neill et al., GCN 44301) using the Nordic Optical Telescope (NOT) equipped with the ALFOSC instrument. Observations consisted of 3x500 s in the SDSS-r band starting at 21:01:12 UT on the 15th of April 2026 (45.73 hr after the GOTO discovery). In our stacked image, the transient is well detected. The calculated AB magnitude was found to be r = 21.85 +/- 0.05 (AB), calculated against the Pan-STARRS catalog, and is not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44303. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42424] GRB 260415B: NuSTAR detection of long prompt emission
by GCN Circulars 15 Apr '26

15 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44302 SUBJECT: GRB 260415B: NuSTAR detection of long prompt emission DATE: 26/04/15 22:13:57 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> G. Waratkar (Caltech) and B. Grefenstette (Caltech) report on behalf of the NuSTAR Search for INteresting Gamma-ray Signals (SINGS) working group: The NuSTAR SINGS working group reports the detection of prompt emission from the long-duration GRB 260415B in both the NuSTAR CsI anti-coincidence shields. Details of the search algorithm will be described in a future paper. The NuSTAR SINGS algorithm, triggered at 2026-04-15T02:28:55.54 UTC, shows a detection of GRB 260415B, also detected by Fermi/GBM (Fermi GBM Team, GCN 44300) and CALET/GBM (Trigger 1460255329). The NuSTAR CsI shield data are recorded at 1 Hz. We detect a ~30-s burst followed by a ~20-s burst after a ~20-s gap, consistent with CALET/GBM and the broad bright Fermi/GBM peak at ~200 s post-trigger. The peak count rate is ~1500-cps with a baseline rate of ~1000-cps during this time period. We do not see evidence in the signal above 100 keV in the CZT detectors. The Fermi/GBM localization (GCN 44300) at RA = 229.43, Dec = 24.94 implies an offset from the NuSTAR boresight of 71-deg (i.e. from the side of the instrument) and an offset from the geocenter of 107-deg. Lightcurves and analysis for this GRB can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/reports/2026/260415B Information on NuSTAR SINGS can be found here: https://nustarsoc.caltech.edu/NuSTAR_Public/grbs/ NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44302. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42423] GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
by GCN Circulars 15 Apr '26

15 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44301 SUBJECT: GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow DATE: 26/04/15 18:38:37 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, M. Wortley, M. Pursiainen, B. P. Gompertz, J. Lyman, R. Starling, G. Ramsay, K. Ackley, M. Dyer, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson, T. Killestein, A. Kumar, on behalf of GOTO collaboration, A. Aryan, T.-W. Chen, Y.-H. Lee, T. K. Ho Ngo, and H.-Y. Hsiao (all NCU), report: We report on the discovery of the rapidly-evolving transient GOTO26djh/AT2026jpw with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) during survey operations. The object was discovered at 2026-04-13 23:17:32 UT at co-ordinates: RA,DEC (J2000): = 13:22:13.21, +37:02:15.16, 200.555049, 37.03754 Observations consisted of 4 x 45s exposures taken in the L band (400-700 nm). Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. The source was initially detected with L = 19.00 ± 0.08 AB mag at t0=2026-04-13 23:17:32 UT before fading to L = 19.61 ± 0.18 AB mag at 2026-04-14 03:21:27 UT (t0 +4.06h), suggesting a decay rate of ~3.5 mag/d. No underlying source is detected in either the Pan-STARRS or SDSS surveys that would suggest the presence of a host galaxy or stellar counterpart. Additionally, the high Galactic latitude (b = +78.15 deg) would be unusual for a local stellar origin. We performed follow-up observations with the 1 m Lulin One-meter Telescope (LOT) at Lulin Observatory, Taiwan, as part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86). The first epoch of LOT observations began at 2026-04-15 14:41 UT (MJD 61145.612, t0 +39.40h). The transient was detected with an r-band magnitude r=21.55 ± 0.07 AB mag. Using this combined dataset, the estimated decay index ranges from -1.6 < alpha < -1.1, assuming explosion times of 12h to 6h pre-discovery, consistent with the decay indices seen in GRB afterglows. GOTO26djh/AT2026jpw is not detected in the most recent pre-discovery GOTO observations taken at 2026-04-12 00:00 UT (t0 -47.29h) to a 3-sigma limiting magnitude of L > 20.5. This constrains its onset to a window of < 2 days before discovery. Despite the apparent lack of an underlying star and an evolution consistent with GRB afterglows, a local stellar origin cannot be definitively excluded with the current data. We encourage further follow-up to determine the nature of this transient. EP/FXT ToO observations have been scheduled. GOTO magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018). LOT magnitudes were calibrated using SDSS stars. Observations are not corrected for Galactic extinction. GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44301. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42422] GRB 260415B: Fermi GBM Final Localization
by GCN Circulars 15 Apr '26

15 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44300 SUBJECT: GRB 260415B: Fermi GBM Final Localization DATE: 26/04/15 05:51:24 GMT FROM: Lorenzo Scotton at UAH <lscottongcn(a)outlook.com> The Fermi GBM team reports the detection of a likely LONG GRB "At 02:25:33.80 UT on 15 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260415B (trigger 797912738/260415101). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 229.43, Dec = 24.94 (J2000 degrees, equivalent to J2000 15h 18m, +24d 56'), with a statistical uncertainty of 9.03 degrees. The angle from the Fermi LAT boresight is 41 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415101/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415101/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415101/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44300. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42421] GRB 260415A: Fermi GBM Final Real-time Localization
by GCN Circulars 15 Apr '26

15 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44299 SUBJECT: GRB 260415A: Fermi GBM Final Real-time Localization DATE: 26/04/15 04:54:40 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 04:43:59 UT on 15 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260415A (trigger 797921044.314306 / 260415197). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 58.5, Dec = -24.0 (J2000 degrees, equivalent to J2000 03h 53m, -24d 00'), with a statistical uncertainty of 5.5 degrees. The angle from the Fermi LAT boresight is 92.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415197/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415197/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260415197/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44299. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42420] Fermi trigger No 797912738: Global MASTER-Net observations report
by GCN Circulars 15 Apr '26

15 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44298 SUBJECT: Fermi trigger No 797912738: Global MASTER-Net observations report DATE: 26/04/15 04:31:12 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-OAGH robotic telescope [1] located in Mexico (OAGH National Institute for Astrophysics, Optics and Electronics) started inspect of the Fermi GRB260415.10 (trigger No 797912738,14h 44m 00.00s , +19d 21m 00.0s, R=6.21) errorbox 6140 sec after notice time and 6176 sec after trigger time at 2026-04-15 04:08:29 UT, with upper limit up to 19.8 mag. The observations began at zenith distance = 58 deg. The sun altitude is -29.0 deg. The galactic latitude b = 62 deg., longitude l = 22 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3252523 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 6206 | 2026-04-15 04:08:29 | MASTER-OAGH | (14h 36m 16.77s , +18d 18m 58.5s) | C | 60 | 19.6 | 6206 | 2026-04-15 04:08:29 | MASTER-OAGH | (14h 37m 29.78s , +17d 44m 59.9s) | C | 60 | 19.8 | 6277 | 2026-04-15 04:09:40 | MASTER-OAGH | (14h 44m 35.36s , +18d 17m 56.2s) | C | 60 | 19.6 | 6277 | 2026-04-15 04:09:40 | MASTER-OAGH | (14h 45m 47.91s , +17d 43m 56.2s) | C | 60 | 19.6 | 6414 | 2026-04-15 04:11:57 | MASTER-OAGH | (14h 30m 17.59s , +20d 12m 49.5s) | C | 60 | 19.6 | 6414 | 2026-04-15 04:11:57 | MASTER-OAGH | (14h 31m 31.50s , +19d 38m 52.0s) | C | 60 | 19.6 | 6486 | 2026-04-15 04:13:09 | MASTER-OAGH | (14h 38m 42.62s , +20d 11m 48.8s) | C | 60 | 19.7 | 6486 | 2026-04-15 04:13:09 | MASTER-OAGH | (14h 39m 56.27s , +19d 37m 50.5s) | C | 60 | 19.8 | 6827 | 2026-04-15 04:18:50 | MASTER-OAGH | (14h 36m 11.16s , +18d 19m 41.4s) | C | 60 | 19.7 | 6827 | 2026-04-15 04:18:50 | MASTER-OAGH | (14h 37m 24.26s , +17d 45m 44.5s) | C | 60 | 19.8 | 6900 | 2026-04-15 04:20:03 | MASTER-OAGH | (14h 44m 41.90s , +18d 18m 39.3s) | C | 60 | 19.6 | 6900 | 2026-04-15 04:20:03 | MASTER-OAGH | (14h 45m 54.73s , +17d 44m 41.1s) | C | 60 | 19.7 | 7036 | 2026-04-15 04:22:19 | MASTER-OAGH | (14h 30m 11.15s , +20d 13m 35.1s) | C | 60 | 19.6 | 7036 | 2026-04-15 04:22:19 | MASTER-OAGH | (14h 31m 25.61s , +19d 39m 38.3s) | C | 60 | 19.6 | 7108 | 2026-04-15 04:23:31 | MASTER-OAGH | (14h 38m 48.80s , +20d 12m 34.4s) | C | 60 | 19.8 | 7108 | 2026-04-15 04:23:31 | MASTER-OAGH | (14h 40m 03.05s , +19d 38m 36.8s) | C | 60 | 19.8 | 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/44298. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42419] GRB 260414A: Glowbug gamma-ray detection
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44297 SUBJECT: GRB 260414A: Glowbug gamma-ray detection DATE: 26/04/14 23:14:50 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260414A, which was detected by Fermi/GBM (GCN 44293). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-04-14 06:31:55.248 with a duration of 21.5 s and a total significance of about 21 sigma. The detection occurred during a time of high background as Glowbug was entering the northern radiation belt. The brightest peaks in the light curve are at ~T0+3.5s and ~T0+12.5s. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44297. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42418] EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44296 SUBJECT: EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope DATE: 26/04/14 17:44:51 GMT FROM: Viraj Karambelkar at Indian Inst of Tech,Bombay <karambelkarvraj21197(a)gmail.com> V. Karambelkar, K. De (Columbia University), G. Mo (Carnegie/Caltech), S. Ibrahim, D. Schiminovich (Columbia University) We observed the field of the fast X-ray transient EP260409a (Jiang et al. 2026, GCN 44240) using the MDM InfraRed Astronomy inGaas Explorer (MIRAGE) instrument on the MDM 1.3m telescope in the near-infrared J and Hs bands. Observations were carried out starting at UTC 2026-04-09T03:10:30 in the J-band and 2026-04-09T03:40:58 in the H-band, approximately three hours after the EP trigger. The exposures lasted for a total of 16 minutes in the J-band and 32 minutes in the H-band. We do not detect the counterpart reported by Quirola-Vasquez et al., GCN 44264 to 5-sigma limits of J >~ 19.5 mag (AB) Hs >~ 19.8 mag (AB) MIRAGE is a new YJHs-band near-infrared imager for the MDM 1.3m telescope. We thank the MDM Observatory staff for supporting the observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44296. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42417] EP260321a: CMO SAI J,K observations
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44295 SUBJECT: EP260321a: CMO SAI J,K observations DATE: 26/04/14 11:27:29 GMT FROM: Alina Volnova at IKI RAS <alinusss(a)gmail.com> A.A. Volnova (IKI), A.M. Tatarnikov (SAI MSU), S.G. Zheltoukhov (SAI MSU), A.S. Pozanenko (IKI), N.S. Pankov (IKI) report on behalf of IKI-GRB-FuN: We observed the field of the fast X-Ray transient EP260321a (Huang et al., GCNs 44068, 44075) at z = 0.0343 (Tanvir et al., GCN 44082) with SAI-2.5 (2.5m) telescope of the Caucasian Mountain Observatory of Sternberg Astronomical Institute (CMO SAI), equipped with the IR camera ASTRONIRCAM. The observations in the J and K filters were carried out on 2026-04-02, and in J filter on 2026-04-07. The Supernova reported previously (Lee et al., GCN 44070; Ma et al., GCN 44074; Aguilar-Ruiz et al., GCN 44076; Liang et al., GCN 44079; Aryan et al., GCN 44081; Tanvir et al., GCN 44082; Moran et al., GCN 44083, Ahumada et al., GCN 44084, Liu et al., GCN 44087; Sankar et al. GCN 44089; de Ugarte Postigo et al., GCN 44091; Xu et al., GCN 44092; Pankov et al. GCN 44103; Corcoran et al., GCN 44105; Rastinejad et al., GCN 44107; Gao et al., GCN 44110; He et al., GCN 44117; Zhang et al., GCN 44171; Li et al., GCN 44284) is clearly detected in stacked frames. Preliminary photometry and observational details are the following: Date UT_start t-T0 Exp. Filter Obj. Err. UL Site/Telescope (mid,days) (n*s) (3sigma) 2026-04-02 21:11:47 12.36569 6*96 J 16.76 0.04 20.5 CMO SAI/SAI-2.5 2026-04-02 20:58:27 12.35698 20*29 K 16.50 0.06 19.1 CMO SAI/SAI-2.5 2026-04-07 17:53:10 17.23089 11*96 J 16.45 0.04 21.1 CMO SAI/SAI-2.5 The photometry is based on several nearby stars from the 2MASS-PSC and is not corrected for the Galactic extinction. The supernova continues to rise in the J-band and is most likely near the maximum of the SN light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44295. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42416] GRB 260412A: Insight-HXMT/HE detection
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44294 SUBJECT: GRB 260412A: Insight-HXMT/HE detection DATE: 26/04/14 07:29:11 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Chao Zheng, Cheng-Kui Li and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-12T06:13:46.169 (T0), Insight-HXMT/HE detected the burst GRB 260412A, which is also detected by Fermi/GBM (Fermi GBM team, GCN #44275), SVOM/ECLAIRs(Ziqi Wang et.al., GCN#44276) and GECAM-B(Xing-Hao Luo.et.al., GCN#44281). The Insight-HXMT/HE light curve mainly consists of multiple pulses with a T90 of 40 +4/-6 s. The 1s peak rate, measured from T0+23 s, is 1028 cnts/sec. Insight-HXMT/HE detected a total of 9203 counts from this burst. The HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260412A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn/ View this GCN Circular online at https://gcn.nasa.gov/circulars/44294. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42415] GRB 260414A: Fermi GBM Final Real-time Localization
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44293 SUBJECT: GRB 260414A: Fermi GBM Final Real-time Localization DATE: 26/04/14 06:42:26 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 06:31:55 UT on 14 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260414A (trigger 797841120.53845 / 260414272). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 17.0, Dec = 39.8 (J2000 degrees, equivalent to J2000 01h 07m, 39d 47'), with a statistical uncertainty of 6.0 degrees. The angle from the Fermi LAT boresight is 48.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260414272/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260414272/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260414272/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44293. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42414] The EP-WXT trigger 01709260122 is likely a flaring star
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44292 SUBJECT: The EP-WXT trigger 01709260122 is likely a flaring star DATE: 26/04/14 06:10:11 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> K. R. Ni (CCNU), Q. C. Liu (THU), D. Y. Li and H. W. Pan (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709260122 at the time of 2026-04-14T05:13:09, is likely a stellar flare associated with RX J1553.0+4457. The estimated flux of the flare is around 1.26e-9 erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.05e32 erg/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/44292. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42413] Fermi GRB 260413A: Global MASTER-Net observations report
by GCN Circulars 14 Apr '26

14 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44291 SUBJECT: Fermi GRB 260413A: Global MASTER-Net observations report DATE: 26/04/14 00:15:57 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260413A ( Fermi GBM team, GCN 44289) errorbox 36329 sec after notice time and 36340 sec after trigger time at 2026-04-13 23:49:17 UT, with upper limit up to 20.7 mag. The observations began at zenith distance = 45 deg. The sun altitude is -20.6 deg. The galactic latitude b = -31 deg., longitude l = 273 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3250278 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 36400 | 2026-04-13 23:49:17 | MASTER-OAFA | (05h 00m 14.08s , -47d 04m 31.9s) | C | 120 | 20.6 | 36536 | 2026-04-13 23:51:33 | MASTER-OAFA | (05h 00m 10.91s , -47d 02m 46.4s) | C | 120 | 20.7 | 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/44291. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42412] GRB 260410A: Glowbug gamma-ray detection of a short burst
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44290 SUBJECT: GRB 260410A: Glowbug gamma-ray detection of a short burst DATE: 26/04/13 21:49:59 GMT FROM: C.C. Cheung at Naval Research Lab <Teddy.Cheung(a)nrl.navy.mil> C.C. Cheung, R. Woolf, M. Kerr, J.E. Grove (NRL), A. Goldstein (USRA), C.A. Wilson-Hodge, D. Kocevski (MSFC), and M.S. Briggs (UAH) report: The Glowbug gamma-ray telescope [1,2,3], operating on the International Space Station, reports the detection of GRB 260410A, which was detected by Fermi/GBM (GCN 44252, 44258), Fermi/LAT (GCN 44253), CALET (GCN 44283), Konus-Wind (GCN 44286), and Insight-HXMT/HE (GCN 44287). Using an adaptive window with a resolution of 32-ms, the burst onset is determined to be 2026-04-10 07:03:55.848 with a duration of 0.38 s and a total significance of about 46 sigma. The light curve comprises a single peak at ~T0+0.2s. The analysis results presented here are preliminary and use a response function that lacks a detailed characterization of the surrounding passive structure of the ISS. Glowbug is a NASA-funded technology demonstrator for sensitive, low-cost gamma-ray transient telescopes developed, built, and operated by the U.S. Naval Research Laboratory (NRL) with support from the University of Alabama in Huntsville, USRA, and NASA MSFC. It was launched on 2023 March 15 aboard the Department of Defense Space Test Program’s STP-H9 to the ISS and operated until 2024 April when it was put in safe storage on orbit. Glowbug was removed from storage and resumed operation on 2025 September 12. [1] Grove, J.E. et al. 2020, Proc. Yamada Conf. LXXI, arXiv:2009.11959 [2] Woolf, R.S. et al. 2022, Proc. SPIE, 12181, id. 121811O [3] Woolf, R.S. et al. 2024, Proc. SPIE, 13151, id. 1315108 Distribution Statement A: Approved for public release. Distribution is unlimited. View this GCN Circular online at https://gcn.nasa.gov/circulars/44290. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42411] GRB 260413A: Fermi GBM Final Real-time Localization
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44289 SUBJECT: GRB 260413A: Fermi GBM Final Real-time Localization DATE: 26/04/13 13:54:18 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 13:43:37 UT on 13 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260413A (trigger 797780622.310696 / 260413572). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 87.0, Dec = -64.0 (J2000 degrees, equivalent to J2000 05h 47m, -64d 00'), with a statistical uncertainty of 26.0 degrees. The angle from the Fermi LAT boresight is 15.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260413572/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260413572/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260413572/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44289. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42410] GRB 260410B: Insight-HXMT/HE detection
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44288 SUBJECT: GRB 260410B: Insight-HXMT/HE detection DATE: 26/04/13 13:29:15 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-10T12:22:26.900 (T0), Insight-HXMT/HE detected GRB 260410B, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44255) and SVOM/GRM (Chen-Wei Wang et al., GCN #44257). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.2 +/- 0.04 s. Insight-HXMT/HE detected a total of 1102 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260410B.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the regular mode with the energy range of about 60-900 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn View this GCN Circular online at https://gcn.nasa.gov/circulars/44288. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42409] GRB 260410A: Insight-HXMT/HE detection
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44287 SUBJECT: GRB 260410A: Insight-HXMT/HE detection DATE: 26/04/13 12:54:41 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-10T07:03:56.950 (T0), Insight-HXMT/HE detected GRB 260410A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44252; Hamburg et al., GCN #44258) and Fermi/LAT (Holzmann Airasca et al., GCN #44253). The Insight-HXMT/HE light curve mainly consists of a single pulse with a T90 of 0.6 +0.5/-0.3 s. Insight-HXMT/HE detected a total of 1462 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260410A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the low gain mode with the energy range of about 300-3000 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn View this GCN Circular online at https://gcn.nasa.gov/circulars/44287. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42408] Konus-Wind detection of GRB 260410A (short/hard)
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44286 SUBJECT: Konus-Wind detection of GRB 260410A (short/hard) DATE: 26/04/13 11:52:18 GMT FROM: Anna Ridnaia at Ioffe Institute <ridnaia(a)mail.ioffe.ru> A. Ridnaia, D. Frederiks, A. Lysenko, D. Svinkin, A. Tsvetkova, M. Ulanov, and T. Cline, on behalf of the Konus-Wind team, report: The short-duration GRB 260410A (Fermi-GBM detection: Fermi GBM team, GCN Circ. 44252, Hamburg et al., GCN Circ. 44258; Fermi-LAT detection: Holzmann Airasca et al., GCN Circ. 44253; CALET-GBM detection: Ricciarini et al., GCN Circ. 44283) triggered Konus-Wind at T0=25436.09 s UT (07:03:56.090). The burst light curve shows a multipeaked structure, which starts at ~T0-0.1 s and has a total duration of ~0.3 s. The emission is seen up to ~10 MeV. The Konus-Wind light curve of this GRB is available at http://www.ioffe.ru/LEA/GRBs/GRB260410_T25436/ As observed by Konus-Wind, the burst had a fluence of 3.36(-0.54,+0.53)x10^-6 erg/cm2, and a 16-ms peak flux, measured from T0+0.054 s, of 2.53(-0.69,+0.68)x10^-5 erg/cm2/s (both in the 20 keV - 10 MeV energy range). The time-averaged spectrum of the burst (measured from T0 to T0+0.192 s) is best fit in the 20 keV - 10 MeV range by the GRB (Band) model with the following parameters: the low-energy photon index alpha = -0.06(-0.34,+0.62), the high energy photon index beta = -2.06(-0.51,+0.28), the peak energy Ep = 784(-283,+341) keV (chi2 = 21/27 dof). All the quoted errors are at the 68% confidence level. All the quoted values are preliminary. View this GCN Circular online at https://gcn.nasa.gov/circulars/44286. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42407] GRB 260411B: GECAM-B observation of a long burst
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44285 SUBJECT: GRB 260411B: GECAM-B observation of a long burst DATE: 26/04/13 10:33:45 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> Xue-Yuan Zao, Chen-Wei Wang, Chao Zheng, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260411B, at 2026-04-11T08:04:42.550 UTC, which is also detected by Fermi/GBM (Fermi GBM team, GCN #44262 and #44266), SVOM/GRM (Chen-Wei Wang et al., GCN #44268) and Feimi/LAT (F. Longo et al., GCN#44277). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of two emission episodes with a total duration (T90) of 18.8 +3.8/-2.0 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260411B.png 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/44285. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42406] EP260321a: SVOM/VT optical observations and color changes around peak
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44284 SUBJECT: EP260321a: SVOM/VT optical observations and color changes around peak DATE: 26/04/13 10:24:49 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, Y. N. Ma, C. Wu, L. P. Xin, Y. L. Qiu, 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) report on behalf of the SVOM/VT team. SVOM/VT performed several ToO observations of EP260321a triggered by Einstein Probe (Huang et al., GCN 44068) in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously from 2026-03-21 (Ma et al., GCN 44074), 2026-03-23, 2026-03-26, 2026-03-28, 2026-04-01, 2026-04-04, 2026-04-07, 2026-04-10 and 2026-04-12. The optical counterpart (Lee et al., GCN 44070; Tanvir et al., GCN 44082; Moran et al., GCN 44083, Ahumada et al., GCN 44084, Liu et al., GCN 44087; Sankar et al. GCN 44089; de Ugarte Postigo et al., GCN 44091; Xu et al., GCN 44092; Pankov et al. GCN 44103; Corcoran et al., GCN 44105; Rastinejad et al., GCN 44107; Gao et al., GCN 44110; He et al., GCN 44117; Zhang et al., GCN 44171) showed a rise to a peak after trigger in both channels, followed by a decline. The peak in VT_B was at approximately 10.7 days post trigger. The preliminary measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 1.906 hr VT_B 53*50 sec 19.70+/-0.05 mag 1.906 hr VT_R 53*50 sec 19.98+/-0.06 mag 19.75 d VT_B 17*50 sec 17.48+/-0.03 mag 19.75 d VT_R 17*50 sec 17.21+/-0.02 mag One should be cautious that the brightness mentioned above may be contaminated by the host. 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/44284. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42405] GRB 260410A: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44283 SUBJECT: GRB 260410A: CALET Gamma-Ray Burst Monitor detection DATE: 26/04/13 08:51:45 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Ricciarini (U of Florence), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), S. Nakahira (JAXA), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260410A (Fermi GBM Final Real-time Localization: Fermi GBM team, GCN #44252; Fermi-LAT detection: Holzmann Airasca et al., GCN #44253; Fermi GBM Observation: Hamburg et al., GCN #44258) at 07:03:56.88 UTC on 10 April 2026 (https://cgbm.calet.jp/cgbm_trigger/flight/1459839839/index.html) The burst signal was seen by all CGBM detectors. The burst light curve shows a short pulse starting at T+0.06 s, peaking at T+0.18 s, and ending at T+0.29 s. The T90 and T50 durations measured with the SGM data are 0.21 +/- 0.04 s and 0.10 +/- 0.03 s (40-1000 keV), respectively. The ground-processed light curve is available at https://cgbm.calet.jp/cgbm_trigger/ground/1459839839/ The CALET data used in this analysis were provided by the Waseda CALET Operation Center located at Waseda University. View this GCN Circular online at https://gcn.nasa.gov/circulars/44283. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42404] The EP-WXT trigger 01709260010 is likely a flaring star
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44282 SUBJECT: The EP-WXT trigger 01709260010 is likely a flaring star DATE: 26/04/13 07:07:31 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. F. Hu (PMO, CAS), X. Tian (GXU), H. N. Yang, H. Sun (NAOC, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709260010 at the time of 2026-04-13T04:55:40, is likely a stellar flare associated with UPM J1133-1531. The estimated flux of the flare is around 2.8 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2.8 x 10^(31) erg/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/44282. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42403] GRB 260412A: GECAM-B observation of a long burst
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44281 SUBJECT: GRB 260412A: GECAM-B observation of a long burst DATE: 26/04/13 06:10:54 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chao Zheng, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260412A, at 2026-04-12T06:13:49.000 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44275) and SVOM/ECLAIRs (Ziqi Wang et.al., GCN#44276). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 32 +6/-4 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260412A.png 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/44281. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42402] Fermi GRB 260412A: Global MASTER-Net observations report
by GCN Circulars 13 Apr '26

13 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44280 SUBJECT: Fermi GRB 260412A: Global MASTER-Net observations report DATE: 26/04/13 00:02:11 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-OAFA robotic telescope [1] located in Argentina (OAFA observatory of San Juan National University) started inspect of the Fermi GRB 260412A ( Fermi GBM team, GCN 44275) errorbox 62093 sec after notice time and 62124 sec after trigger time at 2026-04-12 23:29:10 UT, with upper limit up to 20.6 mag. Observations started at twilight. The observations began at zenith distance = 47 deg. The sun altitude is -16.0 deg. The galactic latitude b = -41 deg., longitude l = 253 deg. Real time updated cover map and OT discovered available here: https://master.sai.msu.ru/site/master2/observ.php?id=3247887 We obtain a following upper limits. Tmid-T0 | Date Time | Site | Coord (J2000) |Filt.| Expt. | Limit| Comment _________|_____________________|_____________________|____________________________________|_____|_______|_______|________ 62184 | 2026-04-12 23:29:10 | MASTER-OAFA | (04h 21m 09.48s , -47d 04m 33.5s) | C | 120 | 20.6 | 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/44280. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42401] GRB 260412A: Fermi GBM Observation
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44279 SUBJECT: GRB 260412A: Fermi GBM Observation DATE: 26/04/12 21:58:16 GMT FROM: Eva MP at INAOE <eva.palafox(a)gmail.com> E. Palafox (INAOE) and U. Pathak (IIT Bombay) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 06:13:46.17 UT on 12 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260412A (trigger 797667231/260412260). which was also detected by SVOM/ECLAIRs (Wang et al. 2026, GCN 44276). The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position. The angle from the Fermi LAT boresight is 35 degrees. The GBM light curve consists of a bright emission episode with multiple peaks with a duration (T90) of about 80 s (50-300 keV). The time-averaged spectrum from T0-19 to T0+60 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.28 +/- 0.07 and the cutoff energy, parameterized as Epeak, is 210 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (7.9 +/- 0.5)E-06 erg/cm^2. The 1-sec peak photon flux measured starting from T0+22 s in the 10-1000 keV band is 3 +/- 0.2 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44279. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42400] GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44278 SUBJECT: GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening DATE: 26/04/12 20:47:14 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> Gaurav Waratkar (Caltech), Elias Kammoun (Caltech), Rahul Jayaraman (Cornell), K-Ryan Hinds (Caltech), Anna Y. Q. Ho (Cornell) report: In response to our NuSTAR DDT request (PI Waratkar), NuSTAR observed GRB 260310A (Fermi GBM team, GCN 43951; Salunkhe et al., GCN 43958), associated with the afterglow AT2026fgk (Hinds et al., TNS AstroNote 2026-65; Konno et al., GCN 43974) beginning at 2026-04-11T13:45:07 UTC, about 32 days after the GRB. A total of 12.7 ks of observations were obtained from both the FPMA and FPMB modules. We clearly detect the X-ray afterglow at the location of AT2026fgk. We performed a preliminary spectral analysis in the 3–79 keV energy range, fitting an absorbed power law. We find a photon index of 1.64 ± 0.25 with an unabsorbed flux of (4.49 ± 0.67) x 10^-13 ergs/cm2/s (2-10 keV). All uncertainties are reported at the 90% CL. Our detection agrees with the deviation from the post-break afterglow decay reported in EP/FXT observations (Jayaraman et al., GCN 44234). We thank the entire NuSTAR Science & Mission operations teams for the rapid approval and execution of this DDT observation. NuSTAR is a NASA Small Explorer mission led by Caltech and managed by JPL for NASA's Science Mission Directorate in Washington. View this GCN Circular online at https://gcn.nasa.gov/circulars/44278. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42399] GRB 260411B: Fermi-LAT detection
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44277 SUBJECT: GRB 260411B: Fermi-LAT detection DATE: 26/04/12 16:41:28 GMT FROM: Rahul Gupta at NASA GSFC <rahul.gupta(a)nasa.gov> F. Longo (Univ. and INFN Trieste), D. Depalo (Politecnico and INFN Bari), R. Gupta (NASA/GSFC), A. Holzmann Airasca (UniTrento and INFN Bari), N. Omodei (Stanford University), and N. Di Lalla (Stanford University) report on behalf of the Fermi-LAT team: At 08:04.35.31 UT on April 11th, 2026, Fermi-LAT detected high-energy emission from GRB 260411B, which was also detected by Fermi-GBM (trigger 797587480/260411337, GCN #44262 and #44266), and SVOM (Wang et al. 2026, GCN #44268). An optical counterpart candidate was detected by GOTO (O'Neill et al. 2026, GCN #44265), DOT (Gupta et al. 2026, GCN #44271), Ondrejov D50 (Jeiinek et al. 2026, GCN #44272), and COLIBRI' (Sánchez Álvarez et al. 2026, GCN #44274). The GBM location was initially inside the LAT field of view at an angle of 60 degrees to the LAT boresight, and remained in the LAT field of view until ~T0+500 s. No significant excess is seen using standard >100 MeV likelihood analysis procedures. Using the LAT Low Energy (LLE) data selection, over 190 counts above background were detected within a 20 s interval coinciding with the time of the GBM emission. This data selection has insufficient spatial resolution to provide a reliable LAT localization. Since an excess of events was not seen using the standard analysis selection, this detection is likely due to low-energy gamma-rays (below 100 MeV). The Fermi-LAT point of contact for this burst is Sara Cutini (sara.cutini(a)pg.infn.it) The Fermi-LAT is a pair conversion telescope designed to cover the energy band from 20 MeV to greater than 300 GeV. It is the product of an international collaboration between NASA and DOE in the U.S. and many scientific institutions across France, Italy, Japan and Sweden. View this GCN Circular online at https://gcn.nasa.gov/circulars/44277. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42398] GRB 260412A: SVOM detection of a long burst
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44276 SUBJECT: GRB 260412A: SVOM detection of a long burst DATE: 26/04/12 06:57:17 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Ziqi Wang (GXU), Zhiyong Liu(GZNU), Hatsune GOTO(RIKEN), Wenjin XIE(NAOC), Ulysse Jacob (LUPM) report on behalf of the SVOM mission team: At 2026-04-12T06:13:46 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260412A (SVOM burst-id sb26041206), which is also detected by Fermi/GBM (Fermi GBM Team, GCN 44275). The following trigger information was received on the ground with low latency by the SVOM VHF Alert Network. The burst was detected both by the Count-Rate Trigger (CRT) and the Image Trigger (IMT), which produced a sequence of 67 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 42.64 in the [8-120] keV energy band over a time window of 81.92 seconds starting at 2026-04-12T06:13:35. The localization of the best alert is R.A., Dec. 79.9074, -44.5851 degrees: R.A. (J2000) = 5h19m37.78s Dec. (J2000) = -44d35m06.31s with a 90% confidence level (C.L.) radius of 2.69 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs preview VHF light curve showed multiple broad peak structures with a T90 duration of about 321.20 (-2.00 +1.89) s in the 5-120 keV energy band. Due to SVOM performing another ToO-EX during the trigger, no immediate slew was performed on this burst. No X-ray observation could be performed by SVOM/MXT for the time being.No optical observation could be performed by SVOM/VT for the time being. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Ziqi Wang: ziqi.wang(a)st.gxu.edu.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44276. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42397] GRB 260412A: Fermi GBM Final Real-time Localization
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44275 SUBJECT: GRB 260412A: Fermi GBM Final Real-time Localization DATE: 26/04/12 06:24:26 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 06:13:46 UT on 12 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260412A (trigger 797667231.169604 / 260412260). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 70.0, Dec = -47.3 (J2000 degrees, equivalent to J2000 04h 40m, -47d 17'), with a statistical uncertainty of 5.7 degrees. The angle from the Fermi LAT boresight is 31.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260412260/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260412260/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260412260/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44275. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42396] GRB 260411B: COLIBRÍ optical observations
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44274 SUBJECT: GRB 260411B: COLIBRÍ optical observations DATE: 26/04/12 05:49:16 GMT FROM: freddalvarez(a)astro.unam.mx Fredd Sánchez Álvarez (UNAM), Antonio de Ugarte Postigo (LAM), Alan M. Watson (UNAM), Rosa L. Becerra (UNAM), Noémie Globus (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), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (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), Benjamin Schneider (LAM) report: We imaged the possible optical counterpart (O’Neill et al., GCN Circ. 44265) of the Fermi GRB 260411B (Fermi GBM Team, GCN Circ. 44262) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-04-12 02:56 to 2026-04-12 04:43 (from 18.86 to 20.68 hours after the trigger) and obtained 25/35/24/84 minutes of exposure in the g/r/i/z filters. The data were reduced, coadded, calibrated, and analyzed 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 image, we detect the optical counterpart reported by O’Neill et al. (GCN Circ. 44265), Gupta et al. (GCN Circ. 44271), and Jelinek et al. (GCN Circ.44272) and obtain the following preliminary magnitudes: g = 21.44 +/- 0.04 r = 20.69 +/- 0.02 i = 20.35 +/- 0.03 z = 20.10 +/- 0.03 After correcting for Galactic extinction (A_g ≈ 0.92 and A_z ≈ 0.41), the g-z colour is 0.85 +/- 0.05. This and the other colours are consistent with an afterglow with moderate reddening from its host galaxy. Furthermore, the detection in g-band suggests that the redshift of the transient is likely z < 3.5, assuming typical IGM absorption. Comparing our r magnitude to the one reported by DOT (Gupta et al. GCN Circ. 44271), we estimate that the temporal decay index between 12.4 and 19.6 hours is α ≈ -2.3. The transient appears to show an initially rapid decay in the early GOTO observations (O’Neill et al. GCN Circ. 44265) at about 0.9 hours, followed by a shallower phase (α ≈ −0.8) between 0.9 and 12.4 hours, and a subsequent steepening at later times. In the Pan-STARRS DR1 images, there is an extended source at about 2” from the position of the transient with preliminary magnitudes of: g = 24.12 +/- 0.23 r = 24.06 +/- 0.31 i = 24.64 +/- 0.53 z = 23.44 +/- 0.38 After correcting for Galactic extinction, we estimate a probability of chance coincidence of about 2%, which suggests that this source is the host galaxy of GRB 260411B. We encourage spectroscopic observations of the source. Further observations are planned. 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/44274. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42395] GRB 260410B: Fermi GBM Observation
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44273 SUBJECT: GRB 260410B: Fermi GBM Observation DATE: 26/04/12 05:02:47 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA) and U. Pathak (IIT Bombay) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 12:22:26.93 UT on 10 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260410B (trigger 797516551/260410516), which was also detected by SVOM/GRM (Wang et al. 2026, GCN 44257). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 4.22, Dec = 37.74 (J2000 degrees, equivalent to J2000 0h 16m, +37d 44'), with a statistical uncertainty of 5.61 degrees (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a mixture of two Gaussians, one with a radius of 1.8 degrees (52% contribution) and one with a radius of 4.1 degrees (47% contribution) [A. Goldstein et al. 2020, ApJ, 895, 1]). The angle from the Fermi LAT boresight is 90 degrees. The GBM light curve single bright emission episode with a duration (T90) of about 0.19 s (50-300 keV). The time-averaged spectrum from T0-0.04 to T0+0.16 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.01 +/- 0.09 and the cutoff energy, parameterized as Epeak, is 1220 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (1.09 +/- 0.03)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 11.3 +/- 0.9 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44273. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42394] GRB 260411B: Ondrejov D50 optical afterglow detection
by GCN Circulars 12 Apr '26

12 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44272 SUBJECT: GRB 260411B: Ondrejov D50 optical afterglow detection DATE: 26/04/12 01:09:43 GMT FROM: Martin Jelinek at Astro.Inst-AVCR,Ondrejov <martin.jelinek(a)asu.cas.cz> M. Jelinek, J. Strobl, F. Novotny, A. Malenakova, R. Hudec (ASU CAS Ondrejov) report: We observed the position of the optical afterglow of GRB 260411B (Fermi GBM team, GCN 44262; O'Neill et al., GCN 44265) with the D50 robotic telescope of the Astronomical Institute Ondrejov, near Prague, Czech Republic. We performed a series of 80x60s exposures in the SDSS r' filter. We faintly detect the optical afterglow (O'Neill et al., GCN 44265) in the 80x60s combined image with exposure mean time 11.45 h after the trigger. The AB magnitude of the object is: r' = 20.0 +/- 0.3 Photometric calibration was performed using the ATLAS REFCAT2 (Tonry et al.) catalog. The magnitude is not corrected for Galactic extinction in the direction of the burst. Comparing with the GOTO detection at t = 0.89 h (L = 17.55 +/- 0.02; O'Neill et al., GCN 44265), this would imply a temporal decay index of alpha ~ 0.9 (where F_nu ~ t^-alpha). View this GCN Circular online at https://gcn.nasa.gov/circulars/44272. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42393] GRB260411B: 3.6m DOT optical observation
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44271 SUBJECT: GRB260411B: 3.6m DOT optical observation DATE: 26/04/11 20:40:36 GMT FROM: ANSHIKA GUPTA at ARIES <anshika05180(a)gmail.com> Anshika Gupta, Aayushi Verma, Pankaj Pawar, Debalina Kar, Dhruv Jain, and Kuntal Misra (ARIES) report: We observed the field of GRB260411B detected by Fermi/GBM (Fermi GBM Team, GCN 44262) with the 3.6m Devasthal Optical Telescope (DOT), located at the Devasthal Observatory of the Aryabhatta Research Institute of Observational Sciences (ARIES), India. The observations began on 2026-04-11 at 20:29:45.480 UT, i.e., ~12.41 hours after the Fermi/GBM trigger. We have two frames with an exposure time of 200s in the r filter. We stacked the images after the alignment. We detect an optical counterpart in our stacked image at the position given by O'Neill et al. (GCN 44265). We obtain the following preliminary magnitude in the stacked image: Date Start_UT T_start-T0 (hours) Filter Exp time (s) Magnitude ================================================================== 2026-04-11 20:29:45.480 ~12.41 r 200s*2 19.74 +/-0.01 Our detection is consistent with O'Neill et al. (GCN 44265). The magnitude is not corrected for the Galactic extinction in the direction of the burst. Photometric calibration is performed using the standard stars from the Pan-STARRS catalog. View this GCN Circular online at https://gcn.nasa.gov/circulars/44271. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42392] GRB 260411A: SVOM/GRM observation
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44270 SUBJECT: GRB 260411A: SVOM/GRM observation DATE: 26/04/11 17:35:00 GMT FROM: xueyuan zao <zaoxueyuan(a)gmail.com> SVOM/GRM team: Xue-Yuan Zao, Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP) Report on behalf of the SVOM team: SVOM/GRM detected the burst GRB 260411A at 2026-04-11T06:36:28.200 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44261). With the event-by-event data downloaded through the X-band ground station, we conducted the standard analysis pipeline of GRB 260411A. The GRM light curve shows that this burst consists of multiple pulses with a T90 of 2.0 +3.2/-1.6 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here： https://www.bursthub.cn//admin/static/svgrb260411A.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 153.6, DEC=12.0, GCN#44261), is located at about 69.8 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. 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/GRM point of contact for this burst is: Xue-Yuan Zao (IHEP) (zaoxy(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44270. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42391] GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44269 SUBJECT: GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst DATE: 26/04/11 16:25:49 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Shi-Jie Zheng, Yue Huang, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Tais Maiolino (LUPM) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight by a bright short burst GRB 260407B (SVOM trigger reference: sb26040702) at 2026-04-07T10:58:55.900 UTC (T0). ECLAIRs was not collecting data at the time of this burst. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a narrow spike with a T90 of 0.11 +0.06/-0.03 s in the 15-5000 keV band. All the signal is detected lower than 100 keV. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260407B.png We note that both the soft spectrum and the short duration suggest a magnetar X-ray burst. 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: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44269. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42390] GRB 260411B: SVOM/GRM observation of a long burst
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44268 SUBJECT: GRB 260411B: SVOM/GRM observation of a long burst DATE: 26/04/11 16:24:34 GMT FROM: Chenwei Wang at IHEP <cwwang(a)ihep.ac.cn> SVOM/GRM team: Chen-Wei Wang, Chao Zheng, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Frédéric Daigne (IAP) Report on behalf of the SVOM team: SVOM/GRM was triggered in-flight GRB 260411B (SVOM trigger reference: sb26041103) at 2026-04-11T08:04:37.000 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN#44262). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of two emission episodes with a T90 of 16.2 +2.1/-1.4 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260411B.png In addition, the position of this burst, as determined by GOTO (RA= 85.567893 deg, DEC= 1.984983 deg, GCN#44265), is located at about 81 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-2.5 to T0+16.4 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.81 +0.09/-0.09 and the cutoff energy, parameterized as Epeak, is 385 +44/-37 keV. The event fluence (10-1000 keV) in this time interval is (2.37 +0.09/-0.09)E-05 erg/cm^2. The 1s peak spectrum, measured from T0+6.7 to T0+7.7 s, is also best fitted by a power law function with an exponential high-energy cutoff. The power law index is -0.41 +0.09/-0.09 and the cutoff energy, parameterized as Epeak, is 331 +20/-17 keV. The flux (10-1000 keV) in this time interval is (6.34 +0.20/-0.20)E-06 erg/cm^2/s. The localization of GRB 260411B in the 'Amati' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260411B_amati.png And the localization in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260411B_yonetoku.png With the brightness of the prompt emission, the predicted soft X-ray afterglow [1] is shown at: https://www.bursthub.cn//admin/static/svgrb260411B_xag_pre.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: Chen-Wei Wang (IHEP)(cwwang(a)ihep.ac.cn) [1] Chen-Wei Wang et al. ApJ 997 353 https://doi.org/10.3847/1538-4357/ae2eae View this GCN Circular online at https://gcn.nasa.gov/circulars/44268. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42389] GRB 260409A: Insight-HXMT/HE detection
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44267 SUBJECT: GRB 260409A: Insight-HXMT/HE detection DATE: 26/04/11 15:14:51 GMT FROM: zhangjinpeng(a)ihep.ac.cn Jin-Peng Zhang, Chen-Wei Wang, Chao Zheng, and Shao-Lin Xiong (IHEP) report on behalf of the Insight-HXMT team: At 2026-04-09T17:32:46.000 (T0), Insight-HXMT/HE detected GRB 260409A, which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44249). The Insight-HXMT/HE light curve mainly consists of several pulses with a T90 of 43 +6/-3 s. The 1 s peak rate, measured from T0+8.5 s, is 919 cnts/sec. Insight-HXMT/HE detected a total of 11547 counts from this burst. The Insight-HXMT/HE light curve can be found here: https://www.bursthub.cn//admin/static/hxmtgrb260409A.png All measurements above are made with the CsI detectors of Insight-HXMT/HE operating in the low gain mode with the energy range of about 300-3000 keV (deposited energy). Only gamma-rays with energy greater than about 200 keV can penetrate the spacecraft and leave signals in the CsI detectors installed inside of the telescope. Insight-HXMT is the first Chinese space X-ray telescope, which was funded jointly by the China National Space Administration (CNSA) and the Chinese Academy of Sciences (CAS). More information about it could be found at: http://hxmten.ihep.ac.cn View this GCN Circular online at https://gcn.nasa.gov/circulars/44267. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42388] GRB 260411B: Fermi GBM Detection
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44266 SUBJECT: GRB 260411B: Fermi GBM Detection DATE: 26/04/11 13:46:30 GMT FROM: Utkarsh Pathak at IIT Bombay <utkarshpathak.07(a)gmail.com> U. Pathak (IITB) and R. Sonawane (IISER TVM) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 08:04:35.31 UT on 11 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260411B (trigger 797587480/260411337). The Fermi GBM final real-time Localization is reported in GCN 44262. An optical counterpart is also detected by GOTO (O'Neill et al. 2026 GCN 44265). The angle from the Fermi LAT boresight is 60 degrees. The GBM light curve consists of two spikes in a single emission episode, with a duration (T90) of about 33 s (50-300 keV). The time-averaged spectrum from T0-2.9 to T0+29.2 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.62 +/- 0.02 and the cutoff energy, parameterized as Epeak, is 348 +/- 4 keV. The event fluence (10-1000 keV) in this time interval is (2.31 +/- 0.05)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+8.3 s in the 10-1000 keV band is 21.8 +/- 0.4 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 293 +/- 3 keV, alpha = -0.54 +/- 0.05 and beta = -2.3 +/- 0.1. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44266. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42387] GRB 260411B: GOTO optical counterpart candidate
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44265 SUBJECT: GRB 260411B: GOTO optical counterpart candidate DATE: 26/04/11 10:56:59 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, R. Starling, G. Ramsay, K. Ackley, M. Dyer, J. Lyman, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Gompertz, B. Godson, T. Killestein, A. Kumar, M. Pursiainen, on behalf of GOTO collaboration We report on optical observations with the Gravitational-wave Optical Transient Observer (GOTO; Steeghs et al. 2022, Dyer et al. 2024) in response to the Fermi/GBM alert GRB 260411B (Fermi GBM team, GCN #44262). Observations covering the localisation area began at 2026-04-11 08:57:53 UT (t0 +0.89h). 8 images consisting of 4 x 90s exposures were taken in the L band (400-700 nm), covering 38.5 sq deg within the 90% localisation contour. ~32.3% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.4 mag. Images were processed immediately after acquisition using the GOTO pipeline. Difference imaging was performed using deeper template observations. Source candidates were initially filtered using a classifier (Killestein et al. 2021) and cross-matched against a variety of contextual and minor planet catalogs. Human vetting was carried out in real time on any candidates that passed the above checks. A new optical source GOTO26dam is identified within the GBM 90% localisation region (22% contour) with co-ordinates: RA,DEC (J2000) = 85.567893, 1.984983, 05:42:16.29, +01:59:05.94 The source was detected with L = 17.55 ± 0.02 AB mag (+0.89h) and is rapidly fading with a decay index alpha ~ -2.1±0.4. We find no evidence of the source prior to the GRB trigger time in previous ATLAS observations at 2026-04-07 17:36:17.597 (t0 -86.47h) down to c > 19.37 mag using the forced photometry server (Shingles et al. 2021). GOTO (https://goto-observatory.org) is a network of telescopes that is principally funded by the STFC and operated at the Roque de los Muchachos Observatory on La Palma, Spain, and Siding Spring Observatory in NSW, Australia, on behalf of a consortium including the University of Warwick, Monash University, Armagh Observatory & Planetarium, the University of Leicester, the University of Sheffield, the National Astronomical Research Institute of Thailand (NARIT), the University of Turku, the University of Portsmouth, the University of Manchester, the University of Birmingham and the Instituto de Astrofisica de Canarias (IAC). View this GCN Circular online at https://gcn.nasa.gov/circulars/44265. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42386] EP260409a: Gemini/FLAMINGOS2 J-band counterpart
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44264 SUBJECT: EP260409a: Gemini/FLAMINGOS2 J-band counterpart DATE: 26/04/11 09:24:03 GMT FROM: P.G. Jonker at Radboud University <p.jonker(a)astro.ru.nl> J. Quirola-Vasquez (Radboud), J. Sanchez-Sierras (Radboud), A. J. Levan (Radboud & Warwick), P. G. Jonker (Radboud), A. Martin-Carrillo (UCD), D. B. Malesani (DAWN/NBI and Radboud), G. Corcoran (UCD), R. A. J. Eyles-Ferris (Leicester), F. E. Bauer (SSI and UTA), J. Chácon (PUC), B. Lemaux (Gemini) report on behalf of a larger collaboration: We observed the field of the fast X-ray transient EP260409a (Jiang et al. 2026, GCN 44242) using the FLAMINGOS2 instrument mounted on the Gemini-South telescope. Two J-band observations were obtained, one on 2026-04-09 06:52:40 (~0.27 d after the EP trigger, T0, 8x40 s exposures) and one on 2026-04-11 02:13:36 UT (i.e., ~2.08 d after T0, 16x40 s exposures). In our first epoch stacked images, we detect a candidate counterpart at coordinates (J2000): RA: 11:31:37.985 DEC: -9:20:43.00 Photometry yields J = 21.06 +/- 0.10 (Vega) calibrated against nearby stars from the 2MASS catalog (not corrected for Galactic extinction). During the second epoch, the target is no longer detected, with a 3sigma limit of J>22.65 (Vega), implying it faded significantly. No source is detected at this location in the Legacy Survey in any band, nor in archival J-, H-, and K-band images from the VISTA Hemisphere Survey. Given the lack of optical detection (Globus et al., GCN 44243; Li et al., GCN 44244) and from our Las Cumbres observations we report a 3 sigma limit of r>23.5 and z>21.5 AB mag (obtained at ~1.37 and 3.26 hours, respectively, after T0 with an exposure time of 6x300 s), this candidate counterpart is significantly red, implying EP260409a could be a high-redshift or high extinction Fast X-ray Transient. We thank the Gemini-South staff, for their rapid execution of these observations. View this GCN Circular online at https://gcn.nasa.gov/circulars/44264. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42385] GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44263 SUBJECT: GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337) DATE: 26/04/11 08:50:14 GMT FROM: Jochen Greiner at MPE <jcgrog(a)mpe.mpg.de> T. Preis (University of Innsbruck) & J. Greiner (MPE Garching) report: The public trigdat data of the Fermi Gamma-ray Burst Monitor (GBM) trigger 797587480 at 08:04:35 on 11 April 2026 were automatically fitted for spectrum and sky location with BALROG (Burgess et al. 2018, MNRAS 476, 1427; Berlato et al. 2019, ApJ 873, 60). The best-fit position is: RA(2000.0) = 85.7 deg Decl.(2000.0) = 3.1 deg The 1 sigma statistical error radius is 2.5 deg. We estimate an additional systematic error of 2 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260411337/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260411337/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260411337/json View this GCN Circular online at https://gcn.nasa.gov/circulars/44263. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42384] GRB 260411B: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44262 SUBJECT: GRB 260411B: Fermi GBM Final Real-time Localization DATE: 26/04/11 08:15:05 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 08:04:35 UT on 11 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260411B (trigger 797587480.306254 / 260411337). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 83.2, Dec = 2.8 (J2000 degrees, equivalent to J2000 05h 32m, 2d 47'), with a statistical uncertainty of 1.0 degrees. The angle from the Fermi LAT boresight is 60.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260411337/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260411337/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260411337/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44262. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42383] GRB 260411A: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44261 SUBJECT: GRB 260411A: Fermi GBM Final Real-time Localization DATE: 26/04/11 06:46:58 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 SHORT GRB At 06:36:28 UT on 11 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260411A (trigger 797582193.127706 / 260411275). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 153.6, Dec = 12.0 (J2000 degrees, equivalent to J2000 10h 14m, 12d 00'), with a statistical uncertainty of 9.6 degrees. The angle from the Fermi LAT boresight is 32.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260411275/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260411275/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260411275/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44261. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42382] GRB 260410A: COLIBRÍ optical upper limit
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44260 SUBJECT: GRB 260410A: COLIBRÍ optical upper limit DATE: 26/04/11 06:40:10 GMT FROM: a.kuwata(a)irya.unam.mx Asuka Kuwata (UNAM), Damien Dornic (CPPM), 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), Sarah Antier (IJCLAB), Rosa L. Becerra (UNAM), Nathaniel R. Butler (ASU), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), 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) and Antonio de Ugarte Postigo (LAM) report: We imaged the field of the Fermi GRB 260410A (A. Holzmann Airasca et al., GCN Circ. 44253) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-04-11 03:50:46 to 04:47:10 UTC (from 20.7805 to 21.7371 hours after the trigger) and obtained 2460 seconds of simultaneous exposure in the r/z filters. The data were reduced, coadded, calibrated, and analyzed 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 image, we do not detect any new source at the Fermi-LAT source position (A. Holzmann Airasca et al., GCN Circ. 44253) down to the following 5-sigma limit: r > 23.26 z > 21.83 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/44260. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42381] EP-WXT01709259790: Optical Upper limits with kinder observations
by GCN Circulars 11 Apr '26

11 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44259 SUBJECT: EP-WXT01709259790: Optical Upper limits with kinder observations DATE: 26/04/11 02:08:30 GMT FROM: Janet Chen at National Central University <janetstars(a)gmail.com> A. Aryan, T.-W. Chen, C.-S. Lin (all NCU), A. K. H. Kong (NTHU), S. Yang(HNAS), S. J. Smartt, J. Gillanders (both Oxford), A. Sankar.K, M.-H. Lee, A. Dutta, Y.-H. Lee, Y.-C. Pan, C.-C. Ngeow, C.-H. Lai, H.-C. Lin, W.-J. Hou, H.-Y. Hsiao, J.-K. Guo (all NCU), Z. N. Wang, D. C. Qiang, L. L. Fan (all HNAS), Y. J. Yang (NYUAD), H.-W. Lin (UMich), H. F. Stevance, S. Srivastav, L. Rhodes (all Oxford), M. Nicholl, M. Fulton, K. W. Smith, C. Angus, A. Aamer (all QUB), T. Moore (STScI), A. Schultz and M. Huber (both IfA, Hawaii) report: We observed the field of the WXT trigger 01709259790 using the 40cm SLT at the Lulin observatory, as part of the Kinder collaboration (Chen et al. 2025, ApJ, 983, 86, doi:10.3847/1538-4357/adb428). The first SLT epoch of observations in r-band started at 12:10 UTC on 10th of April 2026 (MJD 61140.5068), 42 min after the EP-WXT detection. The EP-WXT transient was later identified as the star Gaia DR3 782359908221356544 during its flaring stage (Huang et al. GCN 44256). The star has an archival SDSS magnitude of r = 16.20. In our observations, we captured the stellar flare and the star varies from r = 15.561 +/- 0.042 in our first frame to r = 15.838 +/- 0.028 in the final (12th) image. The detailed photometric measurements using AutoPhOT are as follows: Telescope | Filter | MJD (start) | t-t0 (hr) | Exposure (s) | Magnitude| SLT | r | 61140.5068 | 0.70 | 300 * 1 | 15.561 +/- 0.042 SLT | r | 61140.5104 | 0.78 | 300 * 1 | 15.582 +/- 0.048 SLT | r | 61140.5141 | 0.87 | 300 * 1 | 15.614 +/- 0.049 SLT | r | 61140.5177 | 0.96 | 300 * 1 | 15.718 +/- 0.043 SLT | r | 61140.5215 | 1.05 | 300 * 1 | 15.740 +/- 0.045 SLT | r | 61140.5251 | 1.14 | 300 * 1 | 15.750 +/- 0.038 SLT | r | 61140.5289 | 1.23 | 300 * 1 | 15.762 +/- 0.038 SLT | r | 61140.5326 | 1.31 | 300 * 1 | 15.786 +/- 0.041 SLT | r | 61140.5363 | 1.40 | 300 * 1 | 15.793 +/- 0.043 SLT | r | 61140.5400 | 1.49 | 300 * 1 | 15.805 +/- 0.035 SLT | r | 61140.5437 | 1.58 | 300 * 1 | 15.817 +/- 0.033 SLT | r | 61140.5473 | 1.67 | 300 * 1 | 15.838 +/- 0.028 We also utilized our Kinder Pipeline for the combined 300 sec*12 frames, we obtained an r-band limit of >20.6 mag at a median airmass of 1.13 and an average seeing of 1".5. Our limit is consistent with He et al. (GCN 44254). The presented magnitudes are calibrated using the field stars from the PanSTARRS catalog. The reported upper limit is not corrected for an expected galactic extinction of A_r = 0.02 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/44259. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42380] GRB 260410B: SVOM/GRM detection of a short faint burst
by GCN Circulars 10 Apr '26

10 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44257 SUBJECT: GRB 260410B: SVOM/GRM detection of a short faint burst DATE: 26/04/10 15:59:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chen-Wei Wang (IHEP), F. Piron (LUPM) and C. Lachaud (APC) report on behalf of the SVOM mission team: At 2026-04-10T12:22:27 UTC (T0), SVOM/GRM triggered on the gamma-ray burst GRB 260410B (SVOM burst-id sb26041001) on a timescale of 1 seconds and with a signal-to-noise ratio (SNR) of 5.90. This transient was also detected by Fermi/GBM (GCN Circulars #44255). At the time of this burst, SVOM/ECLAIRs was not taking data. With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that the short burst GRB 260410B consists a single pulse with T90 of 0.20 +0.12/-0.06 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260410B.png The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Chenwei Wang: cwwang AT ihep.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44257. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42379] GRB 260410A: Fermi GBM Observation
by GCN Circulars 10 Apr '26

10 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44258 SUBJECT: GRB 260410A: Fermi GBM Observation DATE: 26/04/10 17:00:13 GMT FROM: rhamburg(a)usra.edu R. Hamburg (USRA), U. Pathak (IIT Bombay) and R. Sonawane (IISER TVM) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:03:57.00 UT on 10 April 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260410A (trigger 797497441/260410294), which was also detected by Fermi-LAT (Holzmann Airasca et al. 2026, GCN 44253) and SVOM/GRM (Wang et al. 2026, GCN 44257). The Fermi GBM real-time localization (GCN 44252) is consistent with the Fermi-LAT position. The angle from the Fermi LAT boresight is 49 degrees. The GBM light curve consists of a single bright emission episode with a duration (T90) of about 1 s (50-300 keV). The time-averaged spectrum from T0-0.07 to T0+0.30 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.17 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 960 +/- 30 keV. The event fluence (10-1000 keV) in this time interval is (1.33 +/- 0.01)E-06 erg/cm^2. The 64-ms peak photon flux measured starting from T0+0.0 s in the 10-1000 keV band is 12.0 +/- 1.0 ph/s/cm^2. The spectral analysis results presented above are preliminary; final results will be published in the GBM GRB Catalog: https://heasarc.gsfc.nasa.gov/W3Browse/fermi/fermigbrst.html For Fermi GBM data and info, please visit the official Fermi GBM Support Page: https://fermi.gsfc.nasa.gov/ssc/data/access/gbm/" View this GCN Circular online at https://gcn.nasa.gov/circulars/44258. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42378] GRB 260410A: SVOM/GRM detection of a short faint burst
by GCN Circulars 10 Apr '26

10 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44257 SUBJECT: GRB 260410A: SVOM/GRM detection of a short faint burst DATE: 26/04/10 15:59:54 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> Chen-Wei Wang (IHEP), F. Piron (LUPM) and C. Lachaud (APC) report on behalf of the SVOM mission team: At 2026-04-10T12:22:27 UTC (T0), SVOM/GRM triggered on the gamma-ray burst GRB 260410A (SVOM burst-id sb26041001) on a timescale of 1 seconds and with a signal-to-noise ratio (SNR) of 5.90. This transient was also detected by Fermi/GBM and Fermi/LAT (GCN Circulars #44252 and #44253). At the time of this burst, SVOM/ECLAIRs was not taking data. The SVOM/GRM light curve shows a single narrow peak structure with a duration of about 0.5 s. SVOM did not slew to the burst. An exceptional ToO observation has been scheduled which started about 3 hours after the trigger time. The Space-based multi-band astronomical Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA), French Space Agency (CNES), and the Chinese Academy of Sciences (CAS), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. SVOM/ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. SVOM/GRM was developed by the Institute of High Energy Physics (IHEP) of CAS. SVOM/MXT was developed jointly by CNES, CEA-IRFU, CNRS-IJCLab, University of Leicester, MPE. The Burst Advocate (BA) on shift for this alert is Chenwei Wang: cwwang AT ihep.ac.cn. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44257. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42377] The EP-WXT trigger 01709259790 is likely a flaring star
by GCN Circulars 10 Apr '26

10 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44256 SUBJECT: The EP-WXT trigger 01709259790 is likely a flaring star DATE: 26/04/10 15:22:03 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. L. Huang, Z. X. Li, J. Y. Cao (IHEP, CAS), Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709259790 at the time of 2026-04-10T11:27:58 (UTC), is likely a stellar flare associated with Gaia DR3 782359908221356544. The estimated flux of the flare is around 6 x 10^(-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 6x 10^31 erg/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/44256. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42376] GRB 260410B: Fermi GBM Final Real-time Localization
by GCN Circulars 10 Apr '26

10 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44255 SUBJECT: GRB 260410B: Fermi GBM Final Real-time Localization DATE: 26/04/10 15:01:29 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 12:22:26 UT on 10 Apr 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260410B (trigger 797516551.925452 / 260410516). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 4.2, Dec = 37.7 (J2000 degrees, equivalent to J2000 00h 16m, 37d 42'), with a statistical uncertainty of 5.6 degrees. The angle from the Fermi LAT boresight is 90.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260410516/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260410516/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260410516/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44255. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 42375] EP-WXT01709259790: Xinglong optical upper limit
by GCN Circulars 10 Apr '26

10 Apr '26

TITLE: GCN CIRCULAR NUMBER: 44254 SUBJECT: EP-WXT01709259790: Xinglong optical upper limit DATE: 26/04/10 14:18:44 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-WXT01709259790, we observed the field of EP-WXT01709259790 using the 2.16-m telescope at Xinglong Observatory, NAOC. We obtained 3x300s clear-band frames with a median time of 2026-04-10T12:16:23, 52 minutes after the EP trigger. No uncatalogued optical transient is detected in the stacked images within the 3 arcmin EP/WXT error circle (WXT01709259790), down to 3-sigma limiting magnitudes of 22.18 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/44254. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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