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[vsnet-grb-info 43040] EP260610b: NOT optical observation
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44902 SUBJECT: EP260610b: NOT optical observation DATE: 26/06/11 02:42:23 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu, X. Liu, L.-B. He, J. An, S.-Q. Jiang, D. Xu (NAOC), S.-Y. Fu (HUST) reports on behalf of a large collaboration: We observed the field of EP260610b detected by EP (Wu et al., GCN 44895), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-06-10 22:20:33 UT, i.e., about 0.4 days post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900) is detected in our stacked images with a preliminary brightness of r ~ 22.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43039] EP260610b: NOT optical observation
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44902 SUBJECT: EP260610b: NOT optical observation DATE: 26/06/11 02:42:23 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu, X. Liu, L.-B. He, J. An, S.-Q. Jiang, D. Xu (NAOC), S.-Y. Fu (HUST) reports on behalf of a large collaboration: We observed the field of EP260610b detected by EP (Wu et al., GCN 44895), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-06-10 22:20:33 UT, i.e., about 0.4 days post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900) is detected in our stacked images with a preliminary brightness of r ~ 22.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43038] EP260610b: NOT optical observation
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44902 SUBJECT: EP260610b: NOT optical observation DATE: 26/06/11 02:42:23 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu, X. Liu, L.-B. He, J. An, S.-Q. Jiang, D. Xu (NAOC), S.-Y. Fu (HUST) reports on behalf of a large collaboration: We observed the field of EP260610b detected by EP (Wu et al., GCN 44895), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-06-10 22:20:33 UT, i.e., about 0.4 days post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900) is detected in our stacked images with a preliminary brightness of r ~ 22.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43037] EP260610b: NOT optical observation
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44902 SUBJECT: EP260610b: NOT optical observation DATE: 26/06/11 02:42:23 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu, X. Liu, L.-B. He, J. An, S.-Q. Jiang, D. Xu (NAOC), S.-Y. Fu (HUST) reports on behalf of a large collaboration: We observed the field of EP260610b detected by EP (Wu et al., GCN 44895), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-06-10 22:20:33 UT, i.e., about 0.4 days post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900) is detected in our stacked images with a preliminary brightness of r ~ 22.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43036] EP260610b: NOT optical observation
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44902 SUBJECT: EP260610b: NOT optical observation DATE: 26/06/11 02:42:23 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu, X. Liu, L.-B. He, J. An, S.-Q. Jiang, D. Xu (NAOC), S.-Y. Fu (HUST) reports on behalf of a large collaboration: We observed the field of EP260610b detected by EP (Wu et al., GCN 44895), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-06-10 22:20:33 UT, i.e., about 0.4 days post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900) is detected in our stacked images with a preliminary brightness of r ~ 22.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43035] EP260610b: NOT optical observation
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44902 SUBJECT: EP260610b: NOT optical observation DATE: 26/06/11 02:42:23 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu, X. Liu, L.-B. He, J. An, S.-Q. Jiang, D. Xu (NAOC), S.-Y. Fu (HUST) reports on behalf of a large collaboration: We observed the field of EP260610b detected by EP (Wu et al., GCN 44895), using the 2.56m Nordic Optical Telescope (NOT) equipped with the ALFOSC camera. Observation started at 2026-06-10 22:20:33 UT, i.e., about 0.4 days post-burst, and a series of r-band frames were obtained. The previously reported optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900) is detected in our stacked images with a preliminary brightness of r ~ 22.5, calibrated with Pan-STARRS DR2 stars in the field and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44902. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43034] GRB 260610B: Fermi GBM Final Localization
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44901 SUBJECT: GRB 260610B: Fermi GBM Final Localization DATE: 26/06/11 01:29:13 GMT FROM: Matt Godwin <msg0028(a)uah.edu> The Fermi GBM team reports the detection of a likely LONG GRB "At 23:46:14.25 UT on 10 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260610B (trigger 802827979/260610990). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 218.66, Dec = 23.94 (J2000 degrees, equivalent to J2000 14h 34m, +23d 56'), with a statistical uncertainty of 2.77 degrees. The angle from the Fermi LAT boresight is 84 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610990/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610990/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260610990/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44901. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43033] EP260610b: SVOM/VT optical confirmation with blue color
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44900 SUBJECT: EP260610b: SVOM/VT optical confirmation with blue color DATE: 26/06/11 01:25:37 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> L. P. Xin, H. L. Li, C. Wu, Y. L. Qiu, J. R. Xu,, Y. N. Ma, Z. H. Yao, X. H. Han, J. Wang, Y. Xu, P. P. Zhang, W. J. Xie, Y. J. Xiao, H. B. Cai, J. S. Deng, J. Y. Wei (NAOC), J. T. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed ToO observations to the field of EP260610b triggered by Einstein Probe (Wu et al., GCN 44895). The observation started at 2026-06-10T13:47:19 UTC, 59.5 minutes post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical counterpart (Levan et al., GCN 44897) was detected by VT in both channels. The following measurements are in the AB magnitude without correction for Galactic extinction: Mid time | Band | Exposure Time | Brightness 2.13 h VT_B 91*50 s 22.6 +/- 0.2 mag 2.13 h VT_R 80*50 s 23.0 +/- 0.3 mag We note the source has a blue color in VT observations. 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/44900. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43032] IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44899 SUBJECT: IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event DATE: 26/06/11 01:17:40 GMT FROM: janeth.phd(a)gmail.com The IceCube Collaboration (http://icecube.wisc.edu/) reports: On 26-06-10 at 20:02:41.03 UT IceCube detected a track-like event with a high probability of being of astrophysical origin. The event was selected by the ICECUBE_Astrotrack_GOLD alert stream. The average astrophysical neutrino purity for Gold alerts is 50%. Given the path through the IceCube detector (track traversing only a limited instrumented volume), the detector does not observe the full energy deposition as well as it would for a track crossing a larger portion of the array. This leads to some uncertainty in the p_astro value, circulated via GCN notice. Regardless, this track remains a strong candidate for an astrophysical neutrino event. This alert has an estimated false alarm rate of 0.1495 events per year due to atmospheric backgrounds. The IceCube detector was in a normal operating state at the time of detection. After the initial automated alert (https://gcn.gsfc.nasa.gov/notices_amon_g_b/142709_10606089.amon) more sophisticated reconstruction algorithms have been applied offline, with the direction refined to: Date: 26-06-10 Time: 20:02:41.03 UT RA: 309.20 (+2.04/-2.06 deg 90% PSF containment) J2000 Dec: 37.22 (+0.96/-0.93 deg 90% PSF containment) J2000 As announced in GCN Circular 43419 (https://gcn.nasa.gov/circulars/43419) IceCube alert notices for high-energy track alerts are now also streamed via Kafka. IceCube Gold/Bronze track alerts are available on the Kafka topic 'gcn.notices.icecube.gold_bronze_track_alerts'. The probability distribution of the true neutrino direction, allowing the extraction of precise 90% containment regions around the best-fit direction, is now available for revised reconstruction of high-energy track alerts. The corresponding sky map is distributed as a FITS file and follows the explicit naming convention IceCube-YYMMDDX, where YYMMDD indicates the date of the event and X is a letter distinguishing multiple alerts on the same day. The download link is provided through the GCN schema distributed via Kafka. Detailed documentation describing the alert distribution, schemas, and probability maps is available at: https://gcn.nasa.gov/missions/icecube. Two gamma-ray sources from the Fermi 4FGL-DR4 catalog are located within the 90% uncertainty region of this event. The closest source is 4FGL J2035.0+3632 (PSR J2034+3632), at RA = 308.7571° and Dec = 36.5371° (J2000), with an angular separation of 0.77° from the best-fit event position. The second-closest source is 4FGL J2030.0+3641 (PSR J2030+3641), at RA = 307.5086° and Dec = 36.6872° (J2000), with an angular separation of 1.45° from the best-fit event position. The IceCube Neutrino Observatory is a cubic-kilometer neutrino detector operating at the geographic South Pole, Antarctica. The IceCube realtime alert point of contact can be reached at roc(a)icecube.wisc.edu View this GCN Circular online at https://gcn.nasa.gov/circulars/44899. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43031] GRB 260515A: SOAR optical observations
by GCN Circulars 10 Jun '26

10 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44898 SUBJECT: GRB 260515A: SOAR optical observations DATE: 26/06/10 20:40:46 GMT FROM: James Freeburn at University of North Carolina at Chapel Hill <jamesfreeburn54(a)gmail.com> Kira Nolan, James Freeburn, Anirudh Salgundi, Igor Andreoni (UNC Chapel Hill): We observed the field of GRB 260515A (Brunet et al., GCN 44622) using the Goodman High Throughput Spectrograph instrument on the 4.1m Southern Astrophysical Research (SOAR) Telescope, in imaging mode. We obtained 3x300s exposures respectively in the SDSS r and i filters, starting at 2026-06-08T02:01:28 UTC, approximately 23 days after the GRB trigger. We confirm the late-time emission (Li et al., GCN 44821) of the optical counterpart previously reported by He et al., GCN 44623; Saccardi et al., GCN 44624; Sosnovskij et al., GCN 44625; He et al., GCN 44626; Lipunov et al., GCN 44627; Wu et al., GCN 44628; Malesani et al., GCN 44629, Dennefeld et al., GCN 44633; Li et al., GCN 44634; Wang et al., GCN 44642; Antier et al., GCN 44643; Pérez-Fournon et al., GCN 44645; Dimple et al. GCN 44646; Moskvitin et al., GCN 44652; Bochenek et al., GCN 44658. We measure the following measurements and the magnitude limit is quoted at the 5 sigma level: | MJD (mid) | T - T_0 | Filter | Mag. (AB) | | --------- | -------- | - | ----- | | 61199.088 | 23.271 d | r | >23.6 | | 61199.099 | 23.282 d | i | 23.1 +/- 0.2 | Photometry is calibrated against nearby PanSTARRS-1 DR2 catalog stars and not corrected for extinction. As this location does not have i-band coverage in Legacy Survey DR10 (Dey et al., 2019), the detected emission may include contributions from the host galaxy. View this GCN Circular online at https://gcn.nasa.gov/circulars/44898. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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