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[vsnet-grb-info 43152] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43151] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43150] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43149] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43148] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43147] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43146] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43145] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43144] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43143] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43142] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43141] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43140] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43139] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43138] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43137] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43136] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43135] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43134] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43133] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43132] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43131] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43130] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43129] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43128] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43127] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43126] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43125] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43124] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43123] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

1 0

[vsnet-grb-info 43122] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43121] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43120] GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44963 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations of possible re-brightening DATE: 26/06/17 09:33:10 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Maslennikova (SAO RAS), V. Goranskij (SAI MSU, SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901; Godwin and Meegan; GCN 44931), and also detected by SVOM (Yu et al., GCN 44944), with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in Rc band on June 14, 15 and 16. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek and Perley, GCN 44932; Pankov et al., GCN 44946; Gillanders et al., GCN 44955; Angulo et al., GCN 44958; Dimple et al., GCN 44959) is detected in our stacked images with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-14 23:15:23 4.56847 15*180 Rc 21.14 0.12 22.3 2026-06-15 23:42:44 5.57617 8*180 Rc 20.98 0.17 21.8 2026-06-16 20:30:40 6.44388 3*600 Rc 21.06 0.18 21.9 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. Although we cannot directly confirm that the afterglow brightness has increased, we can observe a plateau in the afterglow light curve. View this GCN Circular online at https://gcn.nasa.gov/circulars/44963. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43119] GRB 260429A: cubesat Avion detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44962 SUBJECT: GRB 260429A: cubesat Avion detection DATE: 26/06/17 08:30:39 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> From Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2026-04-29 ~23:24:02 UT the short GRB 260429A (Fermi GBM detection: GCN #44425, GCN #44430, SVOM detection: GCN #44439, IPN triangulation: GCN #44459) was detected by the DeCoR-3 instrument on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1]. Total amount of photons detected by Avion is 69 (energy band >30 keV), it corresponds to a fluence of ~6.2*10^(-7) erg/cm^2 in the range 30-500 keV. LC in the energy range of 30-500 keV is a single episode of ~0.5 sec duration with a maximum flux of ~16 phot/(cm^2*s). А total duration (T90) of the burst is less than ~0.5 s. The light curve obtained by Avion is available here: https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260429A_LC_Avion.png Parameters of GRB 260429A as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/44962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43118] GRB 260429A: cubesat Avion detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44962 SUBJECT: GRB 260429A: cubesat Avion detection DATE: 26/06/17 08:30:39 GMT FROM: Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> From Andrey Bogomolov at Moscow State University <aabboogg(a)srd.sinp.msu.ru> A. Bogomolov, V. Bogomolov, A. Iyudin, S. Svertilov, N. Vasiliev on behalf of the MSU “Sozvezdie-270” team, report: At 2026-04-29 ~23:24:02 UT the short GRB 260429A (Fermi GBM detection: GCN #44425, GCN #44430, SVOM detection: GCN #44439, IPN triangulation: GCN #44459) was detected by the DeCoR-3 instrument on the cubesat Avion of the Moscow University project “Sozvezdie-270” [1]. Total amount of photons detected by Avion is 69 (energy band >30 keV), it corresponds to a fluence of ~6.2*10^(-7) erg/cm^2 in the range 30-500 keV. LC in the energy range of 30-500 keV is a single episode of ~0.5 sec duration with a maximum flux of ~16 phot/(cm^2*s). А total duration (T90) of the burst is less than ~0.5 s. The light curve obtained by Avion is available here: https://swx.sinp.msu.ru/models/grb_cat/data/pictures/GRB260429A_LC_Avion.png Parameters of GRB 260429A as well as other GRBs detected by Moscow University cubesats are listed at: https://swx.sinp.msu.ru/models/grb_cat/grb.php?lang=en Avion is one of 5 cubesats of the Moscow University project “Sozvezdie-270” [1] launched on 2023 June 27. The payload of Avion is a set of scintillation gamma-ray detectors DeCoR [2], the energy range is >30 keV, the time resolution is 0.5s. [1] Svertilov et al. 2023 https://link.springer.com/chapter/10.1007/978-3-031-50248-4_21 [2] Bogomolov et al. 2022 Universe 8, 282 https://www.mdpi.com/2218-1997/8/5/282 View this GCN Circular online at https://gcn.nasa.gov/circulars/44962. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43117] GRB260616C: MAXI/GSC detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44961 SUBJECT: GRB260616C: MAXI/GSC detection DATE: 26/06/17 03:18:02 GMT FROM: Wataru Iwakiri at Chiba University <iwakiri.wataru.buz(a)gmail.com> W. Iwakiri (Chiba U.),M. Serino(AGU), H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.), M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), S. Ogawa (TUS) report on behalf of the MAXI team: The MAXI/GSC detected a bright uncatalogued X-ray transient source at 14:47 UT on June 16 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (67.745 deg, 9.294 deg) = (04 30 58, +09 17 38) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.39 deg and 0.3 deg, respectively. The roll angle of long axis from the north direction is 22.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 148 +- 33 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (66.883, 10.254) deg = (04 27 31, +10 15 14) (J2000) (66.471, 9.596) deg = (04 25 53, +09 35 45) (J2000) (68.604, 8.290) deg = (04 34 24, +08 17 23) (J2000) (69.019, 8.945) deg = (04 36 04, +08 56 42) (J2000) A marginal excess of about 50 mCrab may be present in the previous and next MAXI scans at 13:14 UT and 16:20 UT, respectively. However, these scans were obtained during a period of large background variations, and the significance of the excesses is currently unclear. The possible presence of X-ray activity over multiple scans raises the possibility that this event is a new X-ray transient source rather than a GRB. We therefore tentatively name the source MAXI J0430+092. Multi-wavelength follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43116] GRB260616C: MAXI/GSC detection
by GCN Circulars 17 Jun '26

17 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44961 SUBJECT: GRB260616C: MAXI/GSC detection DATE: 26/06/17 03:18:02 GMT FROM: Wataru Iwakiri at Chiba University <iwakiri.wataru.buz(a)gmail.com> W. Iwakiri (Chiba U.),M. Serino(AGU), H. Negoro, M. Nakajima, K. Saito, T. Yokoyama, M. Wada (Nihon U.), T. Mihara, T. Tamagawa, N. Kawai, M. Matsuoka (RIKEN), T. Sakamoto, S. Sugita, Y. Kawakubo, H. Hiramatsu, A. Yoshida (AGU), Y. Tsuboi, Y. Ishihara, H. Ogaki (Chuo U.), M. Shidatsu, C. Kang, M. Uenishi, T. Usuki, S. Yatsuzuka, H. Aoe (Ehime U.), I. Takahashi, Y. Yatsu (Science Tokyo), S. Nakahira, S. Ueno, H. Tomida, M. Kurihara (JAXA), Y. Ueda, K. Fujiwara, S. Kobayashi (Kyoto U.), M. Yamauchi, M. Nishio, C. Hiraizumi (Miyazaki U.), K. Yamaoka (Nagoya U.), M. Sugizaki (Kanazawa U.), T. Kawamuro (Osaka U.), S. Yamada (Tohoku U), S. Ogawa (TUS) report on behalf of the MAXI team: The MAXI/GSC detected a bright uncatalogued X-ray transient source at 14:47 UT on June 16 2026. Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (67.745 deg, 9.294 deg) = (04 30 58, +09 17 38) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.39 deg and 0.3 deg, respectively. The roll angle of long axis from the north direction is 22.0 deg counterclockwise. There is an additional systematic uncertainty of 0.1 deg (90% containment radius). The X-ray flux averaged over the scan was 148 +- 33 mCrab (4.0-10.0keV, 1 sigma error). Without assumptions on the source constancy, we obtain a rectangular error box for the transient source with the following corners: (66.883, 10.254) deg = (04 27 31, +10 15 14) (J2000) (66.471, 9.596) deg = (04 25 53, +09 35 45) (J2000) (68.604, 8.290) deg = (04 34 24, +08 17 23) (J2000) (69.019, 8.945) deg = (04 36 04, +08 56 42) (J2000) A marginal excess of about 50 mCrab may be present in the previous and next MAXI scans at 13:14 UT and 16:20 UT, respectively. However, these scans were obtained during a period of large background variations, and the significance of the excesses is currently unclear. The possible presence of X-ray activity over multiple scans raises the possibility that this event is a new X-ray transient source rather than a GRB. We therefore tentatively name the source MAXI J0430+092. Multi-wavelength follow-up observations are encouraged. View this GCN Circular online at https://gcn.nasa.gov/circulars/44961. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43115] GRB 260616A: Fermi-LAT detection
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44960 SUBJECT: GRB 260616A: Fermi-LAT detection DATE: 26/06/16 23:28:45 GMT FROM: N. Di Lalla at Stanford University <niccolo.dilalla(a)stanford.edu> S. Lopez (CNRS / IN2P3), N. Di Lalla (Stanford University), R. Gupta (NASA/GSFC), F. Longo (University and INFN, Trieste), D. Depalo (Politecnico & INFN Bari), N. Omodei (Stanford University), and J. Valverde (Marquette University) report on behalf of the Fermi-LAT collaboration: At 03:21:54 UT on 16 June 2026, Fermi-LAT detected high-energy emission from GRB 260616A, which was also detected by Fermi-GBM (trigger 803272919/ 260616140, GCN #44948). The best LAT on-ground location is found to be RA, Dec = 93.53, -32.07 (J2000) with an error radius of 0.54 deg (90 % containment, statistical error only). This was 111 deg from the LAT boresight at the time of the trigger. The data from the Fermi-LAT show a significant increase in the event rate that is spatially and temporally correlated with the trigger with high significance. The photon flux above 100 MeV in the time interval 500 - 3000 s after the GBM trigger is (1.8 ± 0.6)E-6 ph/cm2/s. The estimated photon index above 100 MeV is -2.4 ± 0.4. The highest energy photon has an energy of 724 MeV and occurs at 1690 s after trigger time. The Fermi-LAT point of contact for this burst is Samantha López (lpsamy18(a)gmail.com) 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/44960. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43114] GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44959 SUBJECT: GRB 260610B / AT 2026owq: Liverpool Telescope confirmation of continuing optical rebrightening DATE: 26/06/16 20:04:25 GMT FROM: Dimple at University of Birmingham <dimplepanchal96(a)gmail.com> Dimple (U. Birmingham), B. P. Gompertz (U. Birmingham), A. Bochenek (LJMU), D. A. Perley (LJMU), D. O’Neill (U. Birmingham), D. B. Malesani (DAWN/NBI and Radboud) and A. Martin-Carrillo (UCD) report on behalf of a larger collaboration: We have conducted nightly griz observations of the optical afterglow (O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCNs 44910, 44955; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN 44919; Izzo et al., GCN 44920; Li et al., GCN 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN 44946; Angulo et al., GCN 44958) of GRB 260610B (Fermi GBM Team, GCN 44901; Yu et al., GCN 44944) with the IO:O optical camera on the 2m robotic Liverpool Telescope. In our two most recent epochs we detect the optical rebrightening first suggested by Gillanders et al. between their t-t0 = 3.3 and 4.3 day epochs (GCN 44955) in all filters. The measured g- and r-band AB magnitudes are: | t-t0(d) | filter | mag | | 3.99 | g | 21.71 ± 0.07 | | 3.97 | r | 21.34 ± 0.07 | | 5.08 | g | 21.49 ± 0.08 | | 5.09 | r | 21.02 ± 0.07 | These observations indicate that GRB 260610B continues experiencing a rebrightening episode beyond 5 days after trigger. We detect no change in g-r colour when comparing our observations to the earliest Liverpool Telescope epoch (Bochenek & Perley, GCN 44927), suggesting an achromatic rebrightening, inconsistent with expectations for an emerging supernova. The above magnitudes are calibrated against nearby Pan-STARRS objects and are not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44959. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43113] GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44958 SUBJECT: GRB 260610B / AT 2026owq: COLIBRÍ further observations and confirmation of the rebrigthening DATE: 26/06/16 19:58:21 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Camila Angulo (UNAM), Marion Guelfand (CPPM), Rosa L. Becerra (UNAM), Nikos Mandarakas (LAM), Antonio de Ugarte Postigo (LAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Dalya Akl (NYUAD), Jean-Luc Atteia (IRAP),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), Asuka Kuwata (UNAM), Massimiliano Lincetto (CPPM), 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 Alan M. Watson (UNAM) report: We reimaged the field of AT 2026owq (O'Neill et al., GCN Circ. 44903, 44914; Watson et al., GCN Circ. 44905; Zhu et al., GCN Circ. 44909; Gillanders et al., GCN Circ. 44910; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN Circ. 44919; Izzo et al., GCN Circ. 44920; Li et al., GCN Circ. 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN Circ. 44946; Gillanders et al., GCN Circ. 44995), which is the optical counterpart of GRB 260610B (Fermi GBM team, GCN Circ. 44901), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. In our latest epoch, we observed from 2026-06-16 07:26 to 08:41 UTC (from 5.32 to 5.37 days after the GRB trigger) and obtained 6, 4, 5, and 14 minutes of exposure in the g, r, i, and z filters, respectively. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the source AT2026owq with preliminary magnitudes of: g = 21.52 +/- 0.13, r = 21.02 +/- 0.10, i = 20.69 +/- 0.09, z = 20.43 +/- 0.10. Compared with previous observations reported for this event, we also observe the rebrightening/flattening first reported by the Pan-STARRS team (Gillanders et al., GCN Circ. 44995), beginning approximately 80 hours after the trigger and visible in all of our filters. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and México (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, México. View this GCN Circular online at https://gcn.nasa.gov/circulars/44958. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43112] GRB GRB260614A: AstroSat CZTI detection
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44957 SUBJECT: GRB GRB260614A: AstroSat CZTI detection DATE: 26/06/16 19:06:22 GMT FROM: Anuraag Arya at IIT Bombay <aryaanuraag910(a)gmail.com> A. Goyal (IITB), A. Arya (IITB), Harsha K. H. (IUCAA), S. Salunke (IUCAA), M. Tembhurnikar (IUCAA), 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 260614A which was also detected by Fermi (GBM team, GCN Circ. 44935), GECAM (Xing-Hao Luo et. al., GCN Circ. 44940). The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve peaks at 2026-06-14 10:06:15.64. The measured peak count rate associated with the burst is 57 (+28, -14) counts/s above the background in the combined data of three quadrants (out of four), with a total of 391 (+196, -206) counts. The local mean background count rate was 221 (+3, -3) counts/s. We measure a T90 of 20 (+3, -12) s from the cumulative CZT light curve. CZTI data products like interactive and downloadable light curves for this GRB can be found at:https://astrosat.iucaa.in/cift/cift_products/ET20260614T100614/ET20260614T100614_details.html 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/44957. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43111] EP260616a: EP-WXT detection of a fast X-ray transient
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44956 SUBJECT: EP260616a: EP-WXT detection of a fast X-ray transient DATE: 26/06/16 16:27:09 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li (NAO, CAS), J. H. Wu (GZHU), T. Y. Liu, Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe team: We report on the detection of a fast X-ray transient, designated EP260616a, by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission. The transient event started at 2026-06-16T07:05:16 (UTC). The position of the source is R.A. = 256.059 deg, DEC = -32.305 deg (J2000) with an uncertainty of 2.2 arcmin in radius (90% C.L. statistical and systematic). No onboard alert or automated X-ray follow-up observation was triggered at this position due to the low Galactic latitude. The start time and the position of the transient is consistent with that of GRB 260616B detected by Fermi/GBM (GCN 44953). The average 0.5-4 keV spectrum can be fitted by an absorbed power law with a photon index of 1.8 (+0.3/-0.3). The column density is fixed at the Galactic value of 3.4 x 10^21 cm^-2. The derived average unabsorbed 0.5-4 keV flux is 4.1 (+/-0.5) x 10^-10 erg/s/cm^2. The peak flux is around 3.4 x 10^-9 erg/s/cm^2. The uncertainties are at the 90% confidence level for the above parameters. Follow-up observations by EP-FXT will be 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/44956. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43110] GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44955 SUBJECT: GRB 260610B / AT 2026owq: Possible re-brightening identified from Pan-STARRS observations DATE: 26/06/16 15:30:51 GMT FROM: James Gillanders at University of Oxford <jhgillanders.astro(a)gmail.com> J. H. Gillanders (Oxford), M. Huber, K. C. Chambers (IfA, Univ. Hawaii), S. J. Smartt, K. W. Smith (Oxford/QUB), S. Srivastav (Oxford), M. Nicholl, D. Young (QUB), T.-W. Chen (NCU, Taiwan), A. S. B. Schultz, T. de Boer, J. Fairlamb, G. Paek, C. C. Lin, T. Lowe, E. Magnier, P. Minguez, I. A. Smith, R. J. Wainscoat (IfA, Univ. Hawaii). We have been observing AT 2026owq (O’Neill et al., GCNs 44903, 44914; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCNs 44911, 44930; Moskvitin et al., GCNs 44918, 44929; Jackson-Horne et al., GCN 44919; Izzo et al., GCN 44920; Li et al., GCN 44921; Bochenek et al., GCNs 44927, 44932; Pankov et al., GCN 44946), the optical counterpart to GRB 260610B (detected by Fermi/GBM; GCN 44901) with a nightly cadence in grizy using the Pan-STARRS telescope system (Chambers et al., 2016) since MJD 61202.4. The Pan-STARRS system consists of two 1.8m telescope units located at the summit of Haleakala on the Hawaiian island of Maui, employing an SDSS-like filter system denoted as grizy. Our observations consist of 200 second exposures, and have been processed with the standard Pan-STARRS pipeline. After astrometric and photometric calibration, reference images were subtracted from the target images (Magnier et al., 2020a; Magnier et al., 2020b; Waters et al., 2020). Our most recent photometry indicates that the lightcurve evolution of AT 2026owq is no longer fading; instead, the transient appears to be flattening, or re-brightening, across all of griz. Full photometry is presented below. Note that these photometric measurements have not been corrected for Galactic extinction. MJD | Filter | Mag (AB) 61205.271 | g | 21.7+/-0.2 61205.273 | r | 21.2+/-0.1 61205.276 | i | 20.9+/-0.1 61205.278 | z | 20.7+/-0.2 61206.276 | g | 21.8+/-0.3 61206.270 | r | 21.3+/-0.2 61206.268 | i | 20.7+/-0.2 61206.265 | z | 20.6+/-0.2 At the redshift of AT 2026owq (z=0.473; O’Neill et al., GCN 44914), observer-frame i approximately corresponds to rest-frame g. Thus, the absolute magnitude of AT 2026owq on MJD 61206.3, in rest-frame g, is approximately -21.4. Given that, at MJD 61206.3, the transient is only ~2.9 rest-frame days post-explosion, this excess is too bright to be powered by the emergence of a typical GRB-supernova signal. Further follow-up is scheduled with Pan-STARRS to determine its nature. View this GCN Circular online at https://gcn.nasa.gov/circulars/44955. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43109] The EP-WXT trigger 01709270148 is likely a flaring star
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44954 SUBJECT: The EP-WXT trigger 01709270148 is likely a flaring star DATE: 26/06/16 14:44:19 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> T. Y. Liu, D. Y. Li (NAO, CAS), J. H. Wu (GZHU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709270148 at the time of 2026-06-16T14:22:03, is likely a stellar flare associated with LP 820-19. The estimated flux of the flare is around 1.2 x 10 ^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 8.6 x 10^(30) 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/44954. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43108] GRB 260616B: Fermi GBM Detection
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44953 SUBJECT: GRB 260616B: Fermi GBM Detection DATE: 26/06/16 14:20:47 GMT FROM: Christian Malacaria at INAF-OAR <cmalacaria.astro(a)gmail.com> C. Malacaria (INAF-OAR) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 07:05:16.39 UT on 16 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260616B (trigger 803286321/260616295). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 257.49, Dec = -32.62 (J2000 degrees, equivalent to J2000 17h 9m, -32d 37'), with a statistical uncertainty of 1.70 degrees. (radius, 1-sigma containment, statistical only; there is additionally a systematic error which we have characterized as a core-plus-tail model, with 90% of GRBs having a 3.7 deg error and a small tail suffering a larger than 10 deg systematic error [Connaughton et al. 2015, ApJS, 216, 32]). The angle from the Fermi LAT boresight is 76 degrees. The GBM light curve consists of two main pulses with a duration (T90) of about 13.8 s (50-300 keV). The time-averaged spectrum from T0+0.002 to T0+14.464 s is best fit by a Band function with Epeak = 240 +/- 10 keV, alpha = -0.63 +/- 0.04, and beta = -2.09 +/- 0.06. The event fluence (10-1000 keV) in this time interval is (2.03 +/- 0.03)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+10 s in the 10-1000 keV band is 21.3 +/- 0.4 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/44953. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43107] GRB 260604C: GRANDMA late observations with CFHT/MegaCam
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44952 SUBJECT: GRB 260604C: GRANDMA late observations with CFHT/MegaCam DATE: 26/06/16 13:14:53 GMT FROM: antier(a)ijclab.in2p3.fr Q. Bais (KNC), A. Bruna (KNC), L. Laumain (KNC), A. Delaplace (KNC), S. Antier (IJCLAB), M. Pillas (IAP), P. Hello (IJCLAB), M. Coughlin (UMN), L. Desrivieres (KNC) on behalf of GRANDMA and CM2 classroom of St Remy Lès Chevreuse: We conducted further follow-up observations of GRB 260604C (Fermi Team, GCN Circ. 44822, Gotz et al., GCN Circ. 44823) with the Canada-France-Hawaii Telescope/MegaPrime/MegaCam on 2026-06-10. We further detected the source and confirmed that the rebrightening episode ended on 2026-06-10. We posted some of our data in the public site group of the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/GCN-260604_202037. To access, one simply needs to create an account using your ORCID id. These measurements are aligned with all our previous GRANDMA measurements. We thanks the CFHT team for observations obtained with MegaPrime/MegaCam, a joint project of CFHT and CEA/DAPNIA, at the Canada-France-Hawaii Telescope (CFHT) which is operated by the National Research Council (NRC) of Canada, the Institut National des Sciences de l’Univers of the Centre National de la Recherche Scientifique (CNRS) of France, and the University of Hawaii. We also acknowledge funding from the European Union’s Horizon Europe Research and Innovation Programme under Grant Agreement No 101131928 (ACME project). The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK. GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (kilonovacatcher.in2p3.fr). Astrophysics Center for Multimessenger studies in Europe is supported Skyportal/ICARE (contact camille.douzet(a)ijclab.in2p3.fr, skyportal.io). View this GCN Circular online at https://gcn.nasa.gov/circulars/44952. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43106] GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295)
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44951 SUBJECT: GRB 260616B: BALROG localization (Fermi Trigger 803286321 / GRB 260616295) DATE: 26/06/16 09:17:04 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 803286321 at 07:05:16 on 16 June 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) = 255.8 deg Decl.(2000.0) = -32.1 deg The 1 sigma statistical error radius is 1.5 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260616295/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260616295/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260616295/json View this GCN Circular online at https://gcn.nasa.gov/circulars/44951. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43105] The EP-WXT trigger 01709269893 is likely a flaring star
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44950 SUBJECT: The EP-WXT trigger 01709269893 is likely a flaring star DATE: 26/06/16 04:16:36 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> D. Y. Li, T. Y. Liu (NAO, CAS), J. H. Wu (GZHU), Z. X. Ling (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709269893 at the time of 2026-06-16T03:28:01, is likely a stellar flare associated with UCAC3 45-262017. The estimated flux of the flare is around 8.0 x 10^(-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.2 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/44950. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43104] GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140)
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44949 SUBJECT: GRB 260616A: BALROG localization (Fermi Trigger 803272919 / GRB 260616140) DATE: 26/06/16 03:56:27 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 803272919 at 03:21:54 on 16 June 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) = 94.4 deg Decl.(2000.0) = -32.1 deg The 1 sigma statistical error radius is 1.7 deg. We estimate an additional systematic error of 1 deg. Further details are available at: https://grb.mpe.mpg.de/grb/GRB260616140/ The Healpix map can be downloaded from: https://grb.mpe.mpg.de/grb/GRB260616140/healpix The location parameters are available as JSON at: https://grb.mpe.mpg.de/grb/GRB260616140/json View this GCN Circular online at https://gcn.nasa.gov/circulars/44949. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43103] GRB 260616A: Fermi GBM Final Real-time Localization
by GCN Circulars 16 Jun '26

16 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44948 SUBJECT: GRB 260616A: Fermi GBM Final Real-time Localization DATE: 26/06/16 03:34:02 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 03:21:54 UT on 16 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260616A (trigger 803272919.330008 / 260616140). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 95.0, Dec = -31.9 (J2000 degrees, equivalent to J2000 06h 19m, -31d 53'), with a statistical uncertainty of 1.4 degrees. The angle from the Fermi LAT boresight is 111.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260616140/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260616140/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260616140/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44948. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43102] GRB 260614B: SVOM/ECLAIRs refined analysis
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44947 SUBJECT: GRB 260614B: SVOM/ECLAIRs refined analysis DATE: 26/06/15 21:03:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> M. Brunet, O. Godet, S. Guillot (IRAP), M. Pillas (IAP) report on behalf of the SVOM/ECLAIRs team Using the event-by-event data downloaded through the X-band ground station, we report further analysis of SVOM/ECLAIRs observations of GRB 260614B (SVOM burst-id sb26061401 – GCN 44938, trigger time T0 = 2026-06-14T13:49:55 UTC), which was also detected by Fermi/GBM (GCN 44937, 44942) and GECAM-B (GCN 44945). The burst that triggered ECLAIRs onboard shows a multiple peak lightcurve. The burst duration is T90 = 88 +18/-9 s in the 4-120 keV energy band. The time-averaged spectrum before the slew from T0-4 s to T0+37 s in the 5-120 keV energy range is best fitted by a powerlaw model with a photon index of -1.04 +/- 0.03. With this model, the 4-120 keV fluence is (5.4 +/- 0.1)e-6 erg/cm^2 and the 4-120 keV photon flux is 2.50 +0.04/-0.06 ph/cm^2/s. All the quoted errors are at the 68% confidence level. 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. ECLAIRs was developed jointly by CNES, CEA-IRFU, CNRS-IRAP, CNRS-APC. The SVOM/ECLAIRs point of contact for this burst is: Marius Brunet (IRAP) (marius.brunet at utoulouse.fr). View this GCN Circular online at https://gcn.nasa.gov/circulars/44947. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43101] GRB 260610B: Terskol optical observations
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44946 SUBJECT: GRB 260610B: Terskol optical observations DATE: 26/06/15 08:46:27 GMT FROM: Nicolai Pankov at IKI <colinsergesen(a)gmail.com> N. Pankov (IKI), A. Salakhotdinova (INASAN), A. Shein (INASAN), E. Postnikova (INASAN), A. Pozanenko (IKI), A. Moskvitin (SAO RAS), A. Volnova (IKI) report on behalf of IKI-GRB-FuN: We observed the field of GRB 260610B (The Fermi GBM team, GCN 44891; GCN 44901) with the Zeiss-2000 2-meter telescope of the Terskol Observatory on epochs 2026-06-11 and 2026-06-12. The R-band observations were carried out using the CCD-photometer. In the first epoch we acquired a series of 3x120+12x120 sec images, while in the latter epoch 9x120 sec images were obtained. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929; Akl et al., GCN 44930; Bochenek & Perley, GCN 44932) is clearly detected in our co-add images. The observational properties and preliminary photometry are provided further: Date UTstart t-T0 Exp. Filter Mag Err UL (mid,d) (n*s) (3-sigma) 2026-06-11 21:33:51 1.48481 3x120+12x90 R 19.81 0.06 22.4 2026-06-12 19:46:19 2.40802 9x120 R 20.70 0.13 22.3 The photometry is based on nearby SDSS stars (R-magnitudes obtained via Lupton 2005 transformation equations; Moskvitin et al., GCN 44918) and not corrected for the Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44946. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43100] GRB 260614B: GECAM-B observation
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44945 SUBJECT: GRB 260614B: GECAM-B observation DATE: 26/06/15 08:39:27 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered in-flight by GRB 260614B, at 2026-06-14T13:49:54.950 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44937), and SVOM/ECLAIRs (O. Godet et.al., GCN#44938). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 43 +/-7 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260614B.png In addition, the position of this burst is determined by SVOM/VT (RA=353.90883 , DEC=-54.11628, with an uncertainty of 0.50 arcsec, J.T. Palmerio et.al., GCN #44939). With this localization, the time-averaged spectrum from T0-19.5 to T0+22.5 s is best fitted by a power law function. The power law index is -1.58 +0.08/-0.09. The event fluence (10-1000keV) in this time interval is (2.43 +0.17/-0.16)E-05 erg/cm^2. Gravitational wave high-energy Electromagnetic Counterpart All-sky Monitor (GECAM) mission originally consists of two micro-satellites (GECAM-A and GECAM-B) launched in Dec. 2020. As the third member of GECAM constellation, GECAM-C was launched onboard SATech-01 experimental satellite in July 2022. GECAM mission is funded by the Chinese Academy of Sciences (CAS). View this GCN Circular online at https://gcn.nasa.gov/circulars/44945. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43099] GRB 260610B: SVOM/GRM observation
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44944 SUBJECT: GRB 260610B: SVOM/GRM observation DATE: 26/06/15 08:36:29 GMT FROM: yzh807926(a)163.com SVOM/GRM team: Zheng-Hang Yu, Chen-Wei Wang, Yue Huang, Shi-Jie Zheng, Shao-Lin Xiong, Shuang-Nan Zhang (IHEP) SVOM/ECLAIRs team: Marius Brunet (IRAP) Report on behalf of the SVOM team: SVOM/GRM was triggered on-ground by a burst GRB 260610B at 2026-06-10T23:46:14.100 UTC (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44901). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst consists of a main episode with two peaks a T90 of 65.0 +/-8.0 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260610B.png In addition, the position of this burst, as determined by Fermi/GBM (RA= 218.66 deg, DEC= 23.94 deg, ERR=2.77 deg, GCN#44901), is located at about 74 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-10 to T0+60 s is best fitted by a power law function with an exponential high-energy cutoff. The power law index is -1.59 +0.18/-0.22 and the cutoff energy, parameterized as Epeak, is 34 +6/-8 keV. The event fluence (10-1000 keV) in this time interval is (9.48 +0.50/-0.47)E-06 erg/cm^2. The 1s peak spectrum, measured from T0+1.9 to T0+2.9 s, if fitted by a power law function with an exponential high-energy cutoff, the power law index is -1.62 +0.16/-0.32 and the cutoff energy, parameterized as Epeak, is 25 +8/-7 keV. The flux (10-1000 keV) in this time interval is (3.98 +0.41/-0.37)E-07 erg/cm^2/s. With the measured redshift z=0.473 (D. O'Neill et al., GCN#44914), we calculate the isotropic energy Eiso is about 8.8E51 erg. Thus GRB 260610B is well consistent with Type II GRBs in the 'Amati' relation diagram, as shown at: https://www.bursthub.cn//admin/static/svgrb260610B_amati.png The localization of GRB 260421B in the 'Yonetoku' relation diagram is shown at: https://www.bursthub.cn//admin/static/svgrb260610B_yonetoku.png The Space Variable Objects Monitor (SVOM) is a China-France joint mission led by the Chinese National Space Administration (CNSA, China), National Center for Space Studies (CNES, France) and the Chinese Academy of Sciences (CAS, China), which is dedicated to observing gamma-ray bursts and other transient phenomena in the energetic universe. GRM is developed by the Institute of High Energy Physics (IHEP) of CAS. The SVOM point of contact for this burst is: Zheng-Hang Yu(IHEP)(zhyu(a)ihep.ac.cn) View this GCN Circular online at https://gcn.nasa.gov/circulars/44944. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43098] GRB 260614B: SVOM/VT optical observations
by GCN Circulars 15 Jun '26

15 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44943 SUBJECT: GRB 260614B: SVOM/VT optical observations DATE: 26/06/15 01:08:34 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, 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), O. Godet (IRAP) and M. Pillas (IAP) report on behalf of the SVOM/VT team. SVOM/VT performed observations with an automatic slew of GRB 260614B triggered by SVOM/ECLAIRs (sb26061401, Godet et al., GCN 44938), which was also detected by SVOM/GRM (Godet et al., GCN 44938) and Fermi GBM (the Fermi GBM team, GCN 44937; Palafox, GCN 44942). The observation started at 2026-06-14T13:52:36 UTC, i.e., 186 seconds post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The optical counterpart identified via VT VHF data (Palmerio et al., GCN 44939) within the error box of SVOM/ECLAIRs and SVOM/MXT (Godet et al., GCN 44938) is clearly detected in both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 186 s VT_B 50 s 18.28 +/-0.05 mag 186 s VT_R 50 s 15.56 +/-0.04 mag 3.16 h VT_B 20*100 s 23.0 +/-0.2 mag 3.10 h VT_R 16*100 s 20.3 +/-0.1 mag The source showed a fading slope of about -1.2 during the observations above. 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/44943. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43097] GRB 260614B: Fermi GBM Observation
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44942 SUBJECT: GRB 260614B: Fermi GBM Observation DATE: 26/06/14 21:57:48 GMT FROM: Eva M. Palafox at INAOE <eva.palafox(a)gmail.com> E. Palafox (INAOE-Mexico) reports on behalf of the Fermi Gamma-ray Burst Monitor Team: "At 13:49:53.52 UT on 14 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260614B (trigger 803137798/260614576). which was also detected by SVOM/ECLAIRs (Godet et al. 2026, GCN 44938). The Fermi GBM on-ground location is consistent with the SVOM/ECLAIRs position. The angle from the Fermi LAT boresight is 31 degrees. The GBM light curve consists of a single emission episode with a duration (T90) of about 30 s (50-300 keV). The time-averaged spectrum from T0-13 to T0+34 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -0.78 +/- 0.03 and the cutoff energy, parameterized as Epeak, is 510 +/- 10 keV. The event fluence (10-1000 keV) in this time interval is (2.20 +/- 0.04)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+13 s in the 10-1000 keV band is 5.7 +/- 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/44942. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43096] GRB 260610B: ALMA detection
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44941 SUBJECT: GRB 260610B: ALMA detection DATE: 26/06/14 21:57:00 GMT FROM: Tanmoy Laskar at U of Utah <tanmoylaskar(a)gmail.com> T. Laskar (Utah), B. P. Gompertz (Birmingham), G. E. Anderson (Curtin), A. Levan (Radboud and Warwick), Daniele Malesani (DAWN/NBI and Radboud), Steve Schulze (Weizmann), Nial Tanvir (Leicester), A. J. van der Horst (GWU) report on behalf of a larger collaboration: “We observed GRB 260610B (Fermi GBM team, GCN 44891; O'Neill et al., GCN 44903) with the Atacama Large Millimeter/Submillimeter Array (ALMA) at 43 GHz beginning on 2026 June 13 at 01:06 UT (2.62 days after the burst). Preliminary analysis reveals a mm source with flux density of ~ 0.3 mJy at position: RA (J2000) = 14:32:38.2 Dec (J2000) = +27:00:17.6 with an uncertainty of 0.2" in each coordinate. This is consistent with the optical position (O'Neill et al., GCN 44903). Further observations are planned. We thank the P2G, AoD, JAO staff, and the entire ALMA team for their help with these observations." View this GCN Circular online at https://gcn.nasa.gov/circulars/44941. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43095] GRB 260614A: GECAM-B observation
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44940 SUBJECT: GRB 260614A: GECAM-B observation DATE: 26/06/14 16:14:12 GMT FROM: Xinghao Luo at IHEP <2952704891(a)qq.com> Xing-Hao Luo, Chen-Wei Wang, Shao-Lin Xiong (IHEP) report on behalf of GECAM team: GECAM-B was triggered on-ground by GRB 260614A, at 2026-06-14T10:06:15.950 UTC (denoted as T0), which is also detected by Fermi/GBM (Fermi GBM team, GCN #44935). According to the GECAM-B light curves in about 70-6000 keV, this burst mainly consists of multiple pulses with a duration (T90) of 20 +/-6 s. The GECAM-B light curve can be found here: https://www.bursthub.cn//admin/static/gecambgrb260614A.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/44940. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43094] GRB 260614B: SVOM/VT optical candidate from VHF data
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44939 SUBJECT: GRB 260614B: SVOM/VT optical candidate from VHF data DATE: 26/06/14 15:06:45 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> J. T. Palmerio, A. Saccardi (CEA/Irfu), Y. L. Qiu, C. Wu, L. P. Xin (NAOC), M. Pillas (IAP) on behalf of the SVOM/VT team. After the trigger by SVOM/ECLAIRs at 2026-06-14T13:49:55 UTC (T0), SVOM performed an automatic slew on the burst location (Godet et al., GCN 44938). SVOM/VT began observing the field in the VT_B (400nm-650nm) and VT_R (650nm-1000nm) channels simultaneously. From a preliminary analysis of the 1-bit subimage and source list downloaded via VHF network, at least one credible candidate is identified, the details of which are presented below. VT_ID 52: The position of this candidate is R.A., Dec. 353.90883, -54.11628 degrees, corresponding to: R.A. (J2000) = 23h35m38.1s Dec. (J2000) = -54d06m58.6s with an uncertainty of 0.50 arcsec. This candidate was detected in both VT_R and VT_Band was flagged as an uncatalogued source. The candidate's magnitudes are: | date-obs (UTC) | mid-time | exposure | VT_B mag(AB) | VT_R mag(AB) | | -------------------- | ----------- | --------- | ------------- | ------------- | | 2026-06-14T13:54:16 | 2026-06-14T13:56:46 | 6x50s | 19.25 ± 0.01 | 16.35 ± 0.01 | | 2026-06-14T13:59:16 | 2026-06-14T14:01:21 | 5x50s | – | 16.71 ± 0.01 | Magnitudes were not corrected for Galactic reddening. 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/VT was jointly developed by Xi'an Institute of Optics and Precision Mechanics (XIOPM), CAS and National astronomical observatories (NAOC), CAS. The Burst Advocate (BA) on shift for this alert is Marion Pillas: marion.pillas(a)iap.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44939. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43093] GRB 260614B: SVOM detection of a burst
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44938 SUBJECT: GRB 260614B: SVOM detection of a burst DATE: 26/06/14 14:17:03 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> O. Godet (IRAP), M. Pillas (IAP), D. Götz (CEA), F. Robinet (IJCLAB) report on behalf of the SVOM mission team: At 2026-06-14T13:49:55 UTC (T0), SVOM/ECLAIRs triggered and located the gamma-ray burst GRB 260614B (SVOM burst-id sb26061401), also detected by Fermi/GBM (GCN #44937). 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 15 alerts. IMT provided the alert with the best signal-to-noise-ratio in the image (SNR) of 40.78 in the [8-120] keV energy band over a time window of 20.48 seconds starting at 2026-06-14T13:49:52. The localization of the best alert is R.A., Dec. 353.940, -54.154 degrees: R.A. (J2000) = 23h35m45.60s Dec. (J2000) = -54d09m13.40s with a 90% confidence level (C.L.) radius of 2.75 arcmin (including systematic error of 2 arcmin added in quadrature). The SVOM/ECLAIRs light curve showed a multiple broad peak structure with a T90 duration of about 19.62 -2.19 / +5.93 s. This burst also triggered SVOM/GRM at 2026-06-14T13:49:47 on a timescale of 4 seconds with an SNR of 5.10. SVOM slewed to the burst. SVOM/MXT began observing the field at 2026-06-14T13:52:24.0 UTC. Using onboard processed data we found an uncatalogued X-ray source located at R.A., Dec. 353.907, -54.1192 degrees with a 90% C.L. radius of 69 arcseconds. This location is arcminutes from the ECLAIRs onboard position. This position may be improved as more data is received. VT began observing the field after the slew. The analysis of the data will be published in a future circular. 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 Marion Pillas: marion.pillas(a)iap.fr. Please contact the BA by email if you require additional information. View this GCN Circular online at https://gcn.nasa.gov/circulars/44938. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43092] GRB 260614B: Fermi GBM Final Real-time Localization
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44937 SUBJECT: GRB 260614B: Fermi GBM Final Real-time Localization DATE: 26/06/14 13:57:42 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 13:49:53 UT on 14 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260614B (trigger 803137798.515116 / 260614576). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 2.5, Dec = -50.9 (J2000 degrees, equivalent to J2000 00h 10m, -50d 53'), with a statistical uncertainty of 2.7 degrees. The angle from the Fermi LAT boresight is 25.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260614576/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260614576/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260614576/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44937. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43091] GRB 260611B: SVOM/GRM detection
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44936 SUBJECT: GRB 260611B: SVOM/GRM detection DATE: 26/06/14 13:54:22 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: Marius Brunet (IRAP) Report on behalf of the SVOM team: SVOM/GRM detected GRB 260611B during the routine ground search at 2026-06-11T21:32:37.000 (T0), which is also detected by Fermi/GBM (Fermi GBM Team, GCN #44917) and CALET (Nakahira et al, GCN #44923). With the event-by-event data downloaded through the X-band ground station, the GRM light curve shows that this burst mainly consists of multiple pulses with a T90 of 26 +4/-2 s in the 15-5000 keV band. The SVOM/GRM light curve can be found here: https://www.bursthub.cn//admin/static/svgrb260611B.png In addition, the position of this burst, according to Fermi/GBM localization (RA = 13.3, Dec = 22.6, Fermi GBM Team, GCN #44917), is located at about 121 degrees from the SVOM optical axis, which is outside the ECLAIRs field of view. With this localization, the time-averaged spectrum from T0-6 to T0+26 s is fitted by a power law function. The power law index is -2.14 +0.12/-0.12. The event fluence (10-1000 keV) in this time interval is (1.41 +0.13/-0.13)E-05 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/44936. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43090] GRB 260614A: Fermi GBM Final Localization
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44935 SUBJECT: GRB 260614A: Fermi GBM Final Localization DATE: 26/06/14 11:49:11 GMT FROM: Rushikesh Sonawane at IISER TVM <rushikesh23(a)iisertvm.ac.in> The Fermi GBM team reports the detection of a likely LONG GRB "At 10:06:14.62 UT on 14 June 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260614A (trigger 803124379/260614421). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 192.76, Dec = -38.51 (J2000 degrees, equivalent to J2000 12h 51m, -38d 30'), with a statistical uncertainty of 6.04 degrees. The angle from the Fermi LAT boresight is 106 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260614421/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260614421/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260614421/…" View this GCN Circular online at https://gcn.nasa.gov/circulars/44935. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43089] The EP-WXT trigger 01709269488 is likely a flaring star
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44934 SUBJECT: The EP-WXT trigger 01709269488 is likely a flaring star DATE: 26/06/14 06:18:14 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> Y.-H. I. Yin (HKU), G. Y. Zhao (SYSU), Z. M. Wang (BNU) and W. D. Zhang (NAO,CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709269488 at the time of 2026-06-14T05:58:28, is likely a stellar flare associated with Wolf 1473 (Spectroscopic Binary). The estimated flux of the flare is around 1 x 10^(-10) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 2 x 10^30 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/44934. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43088] GRB 260603C: AstroSat CZTI detection
by GCN Circulars 14 Jun '26

14 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44933 SUBJECT: GRB 260603C: AstroSat CZTI detection DATE: 26/06/14 00:21:34 GMT FROM: Gaurav Waratkar at Caltech <gauravwaratkar(a)iitb.ac.in> S.Salunke (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-duration GRB 260603C. The source was clearly detected in the CZT detectors in the 20-200 keV energy range. The light curve showed multiple peaks of emission with the strongest peak at 2026-06-03 20:22:40.3. The measured peak count rate associated with the burst is 83 (+25, -18) counts/s above the background in the combined data of two quadrants (out of four), with a total of 1141 (+467, -343) counts. The local mean background count rate was 150 (+0.7, -2) counts/s. We measure a T90 of 71 (+25, -13) s from the cumulative CZT light curve. The source was faintly detected in the CsI anticoincidence (Veto) detector in the 100-500 keV energy range. The light curve, with a single burst of emission, peaks at 2026-06-03 20:22:40.2. The measured peak count rate associated with the burst is 250 (+71, -36) counts/s above the background in the combined data of all quadrants, with a total of 822 (+283, -302) counts. The local mean background count rate was 1204 (+8, -8) counts/s. We measure a T90 of 5 (+4, -2) s from the cumulative Veto light curve, much lower than the T90 estimated in CZT detectors. We attribute this to a likely unfavorable angle from the boresight for Veto detectors. CZTI data products like interactive and downloadable light curves for this GRB can be found at: http://astrosat.iucaa.in/cift/cift_products/518214162.17/S518214162.17_deta… 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/44933. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43087] GRB 260610B: further Liverpool Telescope optical observations
by GCN Circulars 13 Jun '26

13 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44932 SUBJECT: GRB 260610B: further Liverpool Telescope optical observations DATE: 26/06/13 19:36:46 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of the optical counterpart (O'Neil et al., GCN 44903) of GRB 260610b (Fu et al., GCN 44901) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x120s exposures in SDSS griz filters, starting at 2026-06-13 01:22:29 UT, approximately 2.07 days after Fermi trigger. Some exposures had to be discarded prior to stacking. We detect a source in the images in all filters at the position reported by O'Neil et al. (GCN 44903), observed also by Watson et al. (GCN 44905); Zhu et al. (GCN 44909); Gillanders et al. (GCN 44910); Akl et al. (GCN 44911); O'Neill et al. (GCN 44914); Moskvitin et al. (GCN 44918); Jackson-Horne et al. (GCN 44919); Izzo, (GCN 44920), Li et al. (GCN 44921), Bochenek et al. (GCN 44927), Moskvitin et al. (GCN 44929); and Akl et al. (GCN 44930) . The photometry is: | MJD (mid) | T_mid-T_0 | Filter | Mag. (AB) | |---------------|-------------|-----------|---------------| | 61204.05962 | 49.66 h | r | 21.05 ± 0.07 | | 61204.07237 | 49.97 h | i | 20.61 ± 0.09 | | 61204.07751 | 50.08 h | z | 20.28 ± 0.12 | | 61204.08753 | 50.33 h | g | 21.40 ± 0.14 | The photometry was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44932. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43086] GRB 260610B: Fermi GBM Observation
by GCN Circulars 13 Jun '26

13 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44931 SUBJECT: GRB 260610B: Fermi GBM Observation DATE: 26/06/13 18:21:44 GMT FROM: Matt Godwin <msg0028(a)uah.edu> Matt Godwin (UAH) and C. Meegan (UAH) report on behalf of the Fermi Gamma-ray Burst Monitor Team: "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). An optical counterpart is identified by GOTO (O'Neill, et al. 2026, GCN 44903). The redshift of the source is measured to be z = 0.473, ALFOSC/NOT (ONeill et al. 2026, GCN 44914). The Fermi GBM on-ground location is consistent with the GOTO position. The angle from the Fermi LAT boresight is 97 degrees. The GBM light curve consists of three peaks with a duration (T90) of about 62 s (50-300 keV). The time-averaged spectrum from T0-2.4 to T0+55.4 s is best fit by a power law function with an exponential high-energy cutoff. The power law index is -1.50 +/- 0.01 and the cutoff energy, parameterized as Epeak, is 46.8 +/- 0.4 keV. The event fluence (10-1000 keV) in this time interval is (1.30 +/- 0.02)E-05 erg/cm^2. The 1-sec peak photon flux measured starting from T0+3.8 s in the 10-1000 keV band is 7.7 +/- 0.3 ph/s/cm^2. A Band function fits the spectrum equally well with Epeak= 45.9 +/- 0.5 keV, alpha = -1.4800 +/- 0.0009 and beta = -3.17 +/- 0.01. 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/44931. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43085] GRB 260610B / AT2026owq: GRANDMA optical observations
by GCN Circulars 13 Jun '26

13 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44930 SUBJECT: GRB 260610B / AT2026owq: GRANDMA optical observations DATE: 26/06/13 13:50:34 GMT FROM: Dalya Akl at New York University Abu Dhabi <dka2010(a)nyu.edu> D. Akl (NYUAD), M. Mašek (FZU), R. Hanna (IJCLAB), P. Putsathan (KKU), Y. Rajabov (UBAI), S. Antier (IJCLAB), P. Hello (IJCLAB), M. Coughlin (UNM), S. Karpov (FZU), M. Pillas (IAP), C. Douzet (IJCLAB), A. Simon (TShNU of Kyiv), D. Rusanova (TShNU of Kyiv), V. Vasylenko (NC JASU), O. Burkhonov (UBAI), S. Ehgamberdiev (UBAI), Y. Tillayev (UBAI), P. Put (NARIT), K. Noysena (NARIT), M. Tanasan (CMU/NARIT), D. Turpin (CEA-Saclay/Irfu), M. Freeberg (KNC), A. Klotz (IRAP), C. Limonta (OCA), A. Dupin (OCA), Q. André (OCA), M. Molham (NRIAG), E. Elhosseiny (NRIAG), A. Takey (NRIAG), N. Kochiashvili (AbAO), R. Inasaridze (AbAO), V. Zhuzhunadze (AbAO) on behalf of the GRANDMA collaboration: We observed the field of the Fermi Long GRB 260610B (Fermi GBM team, GCN 44901). The observations started at 16:29:50 UTC on the 11 of June 2026, 0.7 days post the Fermi Trigger. We detected the optical afterglow candidate, reported by GOTO (O'Neill et al, GCN 44903), in several epochs, using TRT-SRO in California state, UBAI-NT60, UBAI-AZT-22 at Madainak Observatory, AZT-8 at Lisnyky Observatory, KAO-1.88m at Kottamia Astronomical Observatory, TAROT-TCA/TCH at Calern and La Silla, and Kilonova Catcher. A subset of the photometry corrected for Galactic extinction is reported in the public ACME service Skyportal/ICARE https://skyportal-icare.ijclab.in2p3.fr/source/2026owq. To access, one simply needs to create an account using your ORCID ID. The data were reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022). Images obtained with the Sloan filters were calibrated using the PanSTARRS DR1 catalog. Images obtained with the Johnson-Cousins filters were calibrated using the Gaia DR3 Synphot catalog. The observations are performed under the P7 campaign of GRANDMA to monitor SVOM alerts and LSST alerts from explosive fast transients filtered by BOOM/Babamul and FINK. The results are consistent with other measurements reported (Zhu et al., GCN 44909; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Li et al., GCN 44921; Bochenek and Perley, GCN 44927; Moskvitin et al., GCN 44929) GRANDMA is a worldwide telescope network (grandma.ijclab.in2p3.fr) devoted to the observation of transients in the context of multi-messenger astrophysics (Antier et al. 2020 MNRAS 497, 5518). Kilonova-Catcher (KNC) is the citizen science program of GRANDMA (http://kilonovacatcher.in2p3.fr/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44930. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43084] GRB 260610B / AT2026owq: further SAO RAS optical observations
by GCN Circulars 13 Jun '26

13 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44929 SUBJECT: GRB 260610B / AT2026owq: further SAO RAS optical observations DATE: 26/06/13 06:35:11 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901) with the Zeiss-1000 1-m telescope of SAO RAS + CCD photometer in BVRcIc filters on June 12. The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920; Li et al., GCN 44921; Bochenek and Perley, GCN 44927) is clearly detected in our frames with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-12 19:21:03 2.41821 5*300 Rc 20.61 0.03 23.5 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44929. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43083] EP260605a: COLIBRÍ optical upper limits
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44928 SUBJECT: EP260605a: COLIBRÍ optical upper limits DATE: 26/06/12 19:15:05 GMT FROM: Rosa Leticia Becerra Godínez at Instituto de Astronomía, UNAM <rbecerra(a)astro.unam.mx> Rosa L. Becerra (UNAM), Massimiliano Lincetto (CPPM), Asuka Kuwata (UNAM), Sarah Antier (IJCLAB), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), Dalya Akl (NYUAD), Nathaniel R. Butler (ASU), Damien Dornic (CPPM), Jean-Grégoire Ducoin (CPPM), Francis Fortin (IRAP), Leonardo García García (UNAM), Ramandeep Gill (UNAM), Noémie Globus (UNAM), Marion Guelfand (CPPM), Nikos Mandarakas (LAM), Diego López-Cámara (UNAM), Francesco Magnani (CPPM), Enrique Moreno Méndez (UNAM), Margarita Pereyra (UNAM), Ny Avo Rakotondrainibe (LAM), Fredd Sánchez Álvarez (UNAM), Benjamin Schneider (LAM), Antonio de Ugarte Postigo (LAM), and Alan M. Watson (UNAM) report: We imaged the field of the EP260605a (Li et al., GCN Circ. 44847) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-06 07:27 to 08:05 UTC (from 21.93 to 22.59 hours after the trigger) and obtained 29 minutes of simultaneous exposure in the r and z filters. Given the proximity of the localization region to the Galactic bulge, we obtained additional observations to serve as templates. The field was reimaged on 2026-06-12 from 07:06 to 08:06 UTC (from 6.90 to 6.94 days after the trigger), yielding 42 minutes of simultaneous exposure in the r and z filters. The data were reduced and coadded with the COLIBRÍ pipeline and analysed with STDWeb/STDPipe (Karpov 2025). The photometry was calibrated using nearby stars from the SkyMapper catalog, is in the AB system, and is not corrected for Galactic extinction. In the image subtraction, we do not detect any new source within the FXT error region (Li et al., GCN Circ. 44867) down to the following 5-sigma limit: r > 21.4 z > 20.6 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/44928. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43082] GRB 260610b: Liverpool Telescope optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44927 SUBJECT: GRB 260610b: Liverpool Telescope optical observations DATE: 26/06/12 18:02:21 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of the optical counterpart (O'Neil et al., GCN 44903) of GRB 260610b (Fu et al., GCN 44901) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 5x120s exposures in SDSS griz filters, starting at 2026-06-10 23:39:02 UT, approximately 23.9 hours after trigger. We detect a source in the stacked images in all filters at the position reported by O'Neil et al. (GCN 44903), observed also by Watson et al. (GCN 44905); Zhu et al. (GCN 44909); Gillanders et al. (GCN 44910); Akl et al. (GCN 44911); O'Neill et al. (GCN 44914); Moskvitin et al. (GCN 44918); Jackson-Horne et al. (GCN 44919); Izzo, (GCN 44920), and Li et al. (GCN 44921). The photometry is: | MJD (mid) | T_mid-T_0 | Filter | Mag. (AB) | | ------------ | ------------ | ------------ | ------------ | | 61202.98947 | 23.98 h | r | 20.22 ± 0.02 | | 61202.99795 | 24.18 h | i | 19.89 ± 0.02 | | 61203.00646 | 24.38 h | z | 19.78 ± 0.05 | | 61203.01493 | 24.59 h | g | 20.66 ± 0.03 | The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44927. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43081] EP260610b: Liverpool Telescope optical upper limits
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44926 SUBJECT: EP260610b: Liverpool Telescope optical upper limits DATE: 26/06/12 17:56:45 GMT FROM: A. Bochenek at Liverpool John Moores University <a.m.bochenek(a)2023.ljmu.ac.uk> A. Bochenek, D. A. Perley (LJMU), report: We observed the field of EP260610b (Wu et al., GCN 44895, Guo et al., GCN 44912) using the IO:O optical camera on the 2m robotic Liverpool Telescope. We obtained 8x200s exposures in SDSS gri filters, starting at 2026-06-11 00:29:50.385 UT, approximately 1.46 days after trigger. We do not detect any sources at the position of the counterpart in the stacked images (Levan et al., GCN 44897; Xin et al., GCN 44900; Zhu et al., GCN 44902; Burkhonov et al., GCN 44904; Moreno Mendez et al., GCN 44906, van Hoof et al., GCN 44915) down to the three-sigma limiting magnitude of g > 23.2, r > 23.5, i > 22.9. We note that forced PSF photometry on r-band exposures gives a two-sigma detection at 23.7 ± 0.5 mag, at a mid-observation time of 1.52 days post-trigger. The photometry is in the AB magnitude system, was calibrated using nearby PanSTARRS secondary standards, and was not corrected for extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44926. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43080] IceCube-260610A: No candidates from the Zwicky Transient Facility
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44925 SUBJECT: IceCube-260610A: No candidates from the Zwicky Transient Facility DATE: 26/06/12 17:49:32 GMT FROM: Jannis Necker at DESY <jannis.necker(a)desy.de> Jannis Necker (Leiden University), Akshay Eranhalodi (DESY), Robert Stein (JSI), Cristobal Zilleruelo Cañas (DESY), and Anna Franckowiak (Ruhr University Bochum) report, On behalf of the Zwicky Transient Facility (ZTF) and Global Relay of Observatories Watching Transients Happen (GROWTH) collaborations: As part of the ZTF neutrino follow up program (Stein et al. 2023), we observed the localization region of the neutrino event IceCube-260610A (IceCube Collaboration 2026, GCN 44899) with the Palomar 48-inch telescope, equipped with the 47 square degree ZTF camera (Bellm et al. 2019, Graham et al. 2019). We started observations in the g- and r-band beginning at 2026-06-11 06:12 UTC, approximately 10.2 hours after event time. We covered 95.9% (4.6 sq deg) of the reported localization region. This estimate accounts for chip gaps. Each exposure was 300s with a typical depth of 21.0 mag. The images were processed in real-time through the ZTF reduction and image subtraction pipelines at IPAC to search for potential counterparts (Masci et al. 2019). AMPEL (Nordin et al. 2019, Stein et al. 2021) was used to search the alerts database for candidates. We reject stellar sources (Tachibana and Miller 2018) and moving objects, and apply machine learning algorithms (Mahabal et al. 2019) . No candidate counterparts were detected. ZTF and GROWTH are worldwide collaborations comprising Caltech/IPAC, USA; University of Maryland, USA; University of California, Berkeley, USA; Cornell University, USA; Drexel University, USA; University of North Carolina at Chapel Hill, USA; Institute of Science and Technology, Austria; National Central University, Taiwan; OKC, Sweden; DZA, Germany. GROWTH acknowledges generous support of the NSF under PIRE Grant No 1545949. Alert distribution service provided by DIRAC@UW (Patterson et al. 2019). Alert database searches are done by AMPEL (Nordin et al. 2019). Alert filtering is performed with the nuztf (Stein et al. 2021, https://github.com/desy-multimessenger/nuztf ). View this GCN Circular online at https://gcn.nasa.gov/circulars/44925. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43079] IceCube-260610A: EP-FXT follow-up observation
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44924 SUBJECT: IceCube-260610A: EP-FXT follow-up observation DATE: 26/06/12 12:01:23 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> G. J. Yang, Q. Y. Wu and Y. Liu (NAO, CAS) on behalf of the Einstein Probe (EP) team: EP-FXT conducted a follow-up observation of IceCube-260610A (GCN 44899), a Gold-track neutrino event. The observation began at 2026-06-10T21:56:33, approximately 1.9 hours after the neutrino trigger, with a total exposure of 7.9 ks. Within the neutrino localization uncertainty region, none of the detected X-ray sources exhibited significant variability compared with their historical fluxes or upper limits. The properties of the detected sources, excluding those clearly associated with stars, are summarized below. Name | RA | Dec | Flux (erg /cm^2 /s) | Flux error (erg /cm^2 /s) | SNR EPF_J203646.2+370943 | 309.1926 | 37.1612 | 6.52e-14 | 1.71e-14 | 5.14 EPF_J203731.0+370929 | 309.3791 | 37.1577 | 5.66e-14 | 1.99e-14 | 4.72 EPF_J203711.7+370245 | 309.2994 | 37.0434 | 1.05e-13 | 2.00e-14 | 8.60 EPF_J203710.6+370109 | 309.2940 | 37.0191 | 5.46e-14 | 1.38e-14 | 6.10 EPF_J203748.1+370629 | 309.4505 | 37.1080 | 5.80e-14 | 1.54e-14 | 5.06 EPF_J203709.1+365818 | 309.2880 | 36.9716 | 6.02e-14 | 1.65e-14 | 4.40 EPF_J203803.5+371737 | 309.5105 | 37.2954 | 9.50e-14 | 2.40e-14 | 5.00 EPF_J203717.9+365622 | 309.3246 | 36.9393 | 5.75e-14 | 1.67e-14 | 4.24 EPF_J203730.0+373440 | 309.3750 | 37.5779 | 1.36e-13 | 5.01e-14 | 4.84 EPF_J203737.9+365019 | 309.4045 | 36.8384 | 7.51e-14 | 2.50e-14 | 4.75 EPF_J203835.0+364342 | 309.6481 | 36.7285 | 2.01e-13 | 4.98e-14 | 6.20 EPF_J203601.0+363247 | 309.0040 | 36.5464 | 2.38e-13 | 8.65e-14 | 3.60 We note that EPF_J203835.0+364342 is associated with a CV named ASASSN -16ix. Additional follow-up observations are planned. View this GCN Circular online at https://gcn.nasa.gov/circulars/44924. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43078] GRB 260611B: CALET Gamma-Ray Burst Monitor detection
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44923 SUBJECT: GRB 260611B: CALET Gamma-Ray Burst Monitor detection DATE: 26/06/12 10:12:20 GMT FROM: Yuta Kawakubo at Aoyama Gakuin University <kawakubo(a)phys.aoyama.ac.jp> S. Nakahira (JAXA), A. Yoshida, T. Sakamoto, S. Sugita, Y. Kawakubo (AGU), K. Yamaoka (Nagoya U), Y. Asaoka (ICRR), S. Torii, Y. Akaike, K. Kobayashi (Waseda U), Y. Shimizu, T. Tamura (Kanagawa U), N. Cannady (GSFC), M. L. Cherry (LSU), S. Ricciarini (U of Florence), P. S. Marrocchesi (U of Siena), and the CALET collaboration: The CALET Gamma-ray Burst Monitor (CGBM) detected GRB 260611B at 21:32:32.02 UTC on 11 June 2026 (trigger #1465248636; https://cgbm.calet.jp/cgbm_trigger/flight/1465248636/index.html) A CGBM Notice was distributed in near real time. This event was also reported by Fermi GBM (Fermi GBM Team., GCN #44917). The burst signal was seen by all CGBM detectors. The burst light curve shows a multi-peaked structure starting at T+0.2 s, peaking at T+14.7 s, and ending at T+28.4 s. The T90 and T50 durations measured with the SGM data are 24.7 +/- 0.9 s and 13.5 +/- 1.2 s in the 40-1000 keV band, respectively. The ground-processed light curve is available at: https://cgbm.calet.jp/cgbm_trigger/ground/1465248636/ 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/44923. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43077] The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44922 SUBJECT: The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare DATE: 26/06/12 09:14:55 GMT FROM: SVOM_group <svomgroup(a)bao.ac.cn> S.J. Yin (GXU), Z. Kang (CHO), C. Wu (NAOC), L.P. Xin, X.H. Han, P.P. Zhang, X.M. Lu (NAOC), Z.W. Li, Y. Lv (CHO), R.S. Zhang, Y.J. Xiao, Y.L. Qiu, J. Wang, J.S. Deng, L. Huang, J.Y. Wei (NAOC) report on behalf of the SVOM/C-GFT team: We observed the field of EP-WXT trigger 01709269176 (Zhou et al., GCN 44913) with LATIOS on SVOM/C-GFT. Observations started at 2026-06-11T13:13:04.862 UTC, ~47.5 min after the trigger. Our observations in g,r and i bands confirmed that the reported associated star (GAIA DR3 1249275629854893952,GCN 44913 ) exhibits stellar flares. A flare is detected at ~5000 s post trigger, with an amplitude of ~1.3 mag in g-band and ~0.4 mag in i-band. The flare epoch is consistent with an X-ray flare detected by EP-FXT (EP team, private communication). The photometry was calibrated against nearby Pan-STARRS1 DR1 stars. We thank the observation assistants Chulei Guo and Yinhuai Hao at Jilin observatory for their excellent support. The Chinese Ground Follow-up Telescope (C-GFT) for the SVOM mission is located at Jilin Station, Changchun Observatory, National Astronomical Observatories, CAS. It features two instruments: (1) CATCH at the Cassegrain focus with a 21 arcmin x 21 arcmin FOV for simultaneous g/r/i-band imaging, and (2) LATIOS, a 4k x 4k CMOS camera at the prime focus with a 1.28 deg x 1.28 deg FOV that images in g, r, and i bands via filter switching. View this GCN Circular online at https://gcn.nasa.gov/circulars/44922. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43076] GRB 260610B / AT2026owq: SVOM/VT optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44921 SUBJECT: GRB 260610B / AT2026owq: SVOM/VT optical observations DATE: 26/06/12 08:27:15 GMT FROM: Huali Li at at NAOC, SVOM <lhl(a)nao.cas.cn> H. L. Li, L. P. Xin, Y. L. Qiu, C. Wu, 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) and J. Palmerio (CEA/Irfu) report on behalf of the SVOM/VT team. SVOM/VT performed a ToO observation of GOTO26fua/AT2026owq (O'Neil et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914; Moskvitin et al., GCN 44918; Jackson-Horne et al., GCN 44919; Izzo, GCN 44920), a possible counterpart of GRB 260610B (Fermi GBM Team, GCN 44901). The observation started at 2026-06-11T13:05:40 UTC, i.e., 13.32 hours post trigger in the VT_B (400-650 nm) and VT_R (650-1000 nm) channels simultaneously. The OT was clearly detected in both channels. The following measurements are in the AB magnitude and are not corrected for Galactic extinction: Mid time | Band | Exposure Time | Brightness 14.50 h VT_B 30*70 s 20.10 +/-0.06 mag 16.12 h VT_B 29*70 s 20.16 +/-0.06 mag 14.52 h VT_R 28*70 s 19.38 +/-0.06 mag 16.15 h VT_R 26*70 s 19.49 +/-0.06 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/44921. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43075] GRB 260610B / AT2026owq: OASDG optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44920 SUBJECT: GRB 260610B / AT2026owq: OASDG optical observations DATE: 26/06/12 07:54:38 GMT FROM: luca.izzo(a)inaf.it L. Izzo (INAF-OACn, DARK/NBI, OASDG) reports: We observed the counterpart of GRB 260610B (Fermi GBM team, GCN #44901) using the 0.5-m T1 telescope of the Osservatorio Astronomico S. Di Giacomo (OASDG), located in Agerola, Italy. Our observations started on 2026 June 11 at 21:44 UT, 0.917 days after the GRB trigger. We acquired a series of 8 × 300 s images in the Rc and Ic filters. The optical counterpart, also reported as AT2026owq (O'Neill et al., GCN #44903; Watson et al., GCN #44905; Zhu et al., GCN #44909; Gillanders et al., GCN #44910; Akl et al., GCN #44911; O'Neill et al., GCN #44914; Moskvitin et al., GCN #44918; Perley et al., GCN #44919), is clearly detected in both stacked images. We measure the following preliminary magnitudes (AB), which have been calibrated against nearby stars from the Pan-STARRS catalog and appropriately transformed to Rc and Ic magnitudes. Rc = 19.14 +/- 0.16 mag Ic = 18.88 +/- 0.16 mag View this GCN Circular online at https://gcn.nasa.gov/circulars/44920. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43074] GRB 260610B: IAC-80 Optical observations
by GCN Circulars 12 Jun '26

12 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44919 SUBJECT: GRB 260610B: IAC-80 Optical observations DATE: 26/06/12 07:06:28 GMT FROM: Daniel Perley at Liverpool JMU <d.a.perley(a)ljmu.ac.uk> Dominic Jackson-Horne (UOL/LJMU), Danny McDonnell (UOL/LJMU), Esme Williams (UOL/LJMU), Daffyd Thomas (UOL/LJMU), Ruby Keeling-Roberston (UOL/LMJU), Farhan Qamar Salmo (UOL/LJMU), Oliver King (UOL/LJMU), Daniel Perley (LJMU), H.-M. S. Grabham (LJMU), and Daniel Harman (LJMU) report: We observed the optical afterglow (D. O'Neill, et al., GCN 44903) of GRB 260610B (The Fermi GBM team, GCN 44901) using the 0.82m IAC80 telescope of Teide Observatory, equipped with the CAMELOT2 optical imager. Our first set of observations commenced at 21:41 UT and concluded at 22:20 UT on June 11; a second set of observations was then taken between 01:20 UT and 02:05 UT on June 12. We report the following photometry: | Date | UTstart | t-T0 (d) | Exp (n*s) | Filter | Mag | Err | |------------|----------|----------|-----------|--------|-------|------| | 2026-06-11 | 21:41:52 | 0.931 | 3*180 | SDSS-r | 20.04 | 0.06 | | 2026-06-11 | 22:03:58 | 0.928 | 3*180 | Rc | 19.85 | 0.06 | | 2026-06-11 | 22:17:05 | 0.938 | 3*180 | Ic | 19.23 | 0.05 | | 2026-06-11 | 22:25:33 | 0.943 | 3*180 | B | 20.94 | 0.13 | | 2026-06-12 | 01:20:48 | 1.065 | 3*120 | B | 21.47 | 0.26 | | 2026-06-12 | 01:27:40 | 1.070 | 3*120 | V | 20.35 | 0.09 | | 2026-06-12 | 01:34:33 | 1.075 | 3*120 | Ic | 19.40 | 0.08 | | 2026-06-12 | 01:41:26 | 1.080 | 3*120 | SDSS-r | 20.26 | 0.09 | This preliminary photometry is calibrated relative to the SDSS star J143237.88+270028.3 (using the Lupton 2005 transformation equations) and not corrected for Galactic extinction. View this GCN Circular online at https://gcn.nasa.gov/circulars/44919. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43073] GRB 260610B / AT2026owq: SAO RAS optical observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44918 SUBJECT: GRB 260610B / AT2026owq: SAO RAS optical observations DATE: 26/06/11 22:05:25 GMT FROM: Alexander Moskvitin at SAO RAS <mosk(a)sao.ru> A. Moskvitin (SAO RAS), O. Spiridonova (SAO RAS), A. Pozanenko (IKI), A. Volnova (IKI), N. Pankov (IKI) report on behalf of GRB follow-up team We observed the field of GRB 260610B discovered by Fermi (The Fermi GBM team, GCN 44891; GCN 44901) with the Zeiss-1000 1-m telescope of SAO RAS equipped with the CCD photometer. The observations carried out in BVRcIc filters starting June 11, 19:43:01 UT (since ~ 1.4 days since trigger). The OT (O'Neill et al., GCN 44903; Watson et al., GCN 44905; Zhu et al., GCN 44909; Gillanders et al., GCN 44910; Akl et al., GCN 44911; O'Neill et al., GCN 44914) is clearly detected in our frames with the following brightness: Date, UTstart, t-T0, Exp., Filter, Mag, Err., UL (mid,d) (n*s) (3-sigma) 2026-06-11 19:43:01 1.40315 2*300 Rc 19.73 0.03 22.6 This preliminary photometry is based on nearby SDSS stars (using Lupton 2005 transformation equations) and not corrected for Galactic extinction. The observations are ongoing. View this GCN Circular online at https://gcn.nasa.gov/circulars/44918. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43072] GRB 260611B: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44917 SUBJECT: GRB 260611B: Fermi GBM Final Real-time Localization DATE: 26/06/11 21:44:58 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 21:32:33 UT on 11 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260611B (trigger 802906358.618188 / 260611898). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 13.3, Dec = 22.6 (J2000 degrees, equivalent to J2000 00h 53m, 22d 36'), with a statistical uncertainty of 2.2 degrees. The angle from the Fermi LAT boresight is 88.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611898/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611898/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611898/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44917. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43071] EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44916 SUBJECT: EP260601a: VLT/X-shooter spectroscopic host galaxy redshift z = 1.068 DATE: 26/06/11 15:26:01 GMT FROM: Agnes van Hoof at Radboud University <agnes.vanhoof(a)ru.nl> A. P. C. van Hoof (Radboud), J. Sanchez-Sierras (Radboud), P. G. Jonker (Radboud), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), D. B. Malesani (DAWN/NBI and Radboud), A. Martin-Carrillo (UCD), report on behalf of a larger collaboration: We observed the likely host galaxy of EP260601a/GRB 260601B (Yang et al., GCN 44766; Yu et al., GCN 44767; Wang et al., GCN 44768; Waratkar et al., GCN 44771; Sugita et al., GCN 44773) that is at the position of the optical counterpart (Liu et al., GCN 44764; Guelfand et al., GCN 44765; Li et al. GCN 44769) using the ESO Very Large Telescope (VLT) equipped with the X-shooter spectrograph. The spectrum covers the wavelength range of 3000 - 24000 AA with total exposure times of 2910, 2980 and 3000 s in the UVB, VIS and NIR arms, respectively. The observation started on 2026-06-11 at 07:39:12 UT, i.e. ~10 days after the event. We detect clear emission lines in the spectrum, which we identify as the [O II] 3726, 3729 doublet (resolved), H-gamma, and [O III] 5008 at a redshift of z = 1.068. We suggest that this is the redshift of the host galaxy of EP260601a. We thank the ESO staff at Paranal for their excellent support, in particular Celia Desgrange, Claudia Paladini, Francisco Caceres, and John Pritchard. View this GCN Circular online at https://gcn.nasa.gov/circulars/44916. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43070] EP260610b: GTC likely spectroscopic redshift z = 1.10
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44915 SUBJECT: EP260610b: GTC likely spectroscopic redshift z = 1.10 DATE: 26/06/11 14:52:44 GMT FROM: Daniele Bjørn Malesani at Cosmic Dawn Center, Niels Bohr Institute <daniele.malesani(a)nbi.ku.dk> A. P. C. van Hoof (Radboud), D. Mata Sanchez (IAC and ULL), G. Corcoran (UCD), A. J. Levan (Radboud and Warwick), P. G. Jonker (Radboud), D. B. Malesani (DAWN/NBI and Radboud), David Garcia Alvarez (GTC), report on behalf of a larger collaboration: We observed the optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900; Zhu et al., GCN 44902; Burkhonov et al., GCN 44904; Moreno Mendez et al., GCN 44906) of the fast X-ray transient EP260610b (Wu et al., GCN 44895; Guo et al., GCN 44912) using the Gran Telescopio Canarias (GTC) located in the island of La Palma (Canary Islands, Spain), equipped with the OSIRIS+ spectrograph. A sequence of 3x1200 s observations was secured using grism R1000B, which covers the wavelength range 3600-7790 AA. The observation mid time was 2026 Jun 11.183 UT (15.58 hr after the EP/WXT trigger). In the acquisition image (taken 14.96 hr after trigger), we measure an AB magnitude r = 23.38 +- 0.11, calibrated against the Pan-STARRS catalog, and not corrected for Galactic extinction. The delivered seeing was 0.8". Weak continuum is detected across the entire wavelength range. From the lack of hydrogen absorption, we can set a firm upper limit to the redshift z < 2.1. Weak absorption features can also be identified matching Mg II and Fe II at z = 1.10. Line-stacking analysis confirms a significant absorption system at this redshift, which we suggest to be the likely redshift of EP260610b. View this GCN Circular online at https://gcn.nasa.gov/circulars/44915. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43069] GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44914 SUBJECT: GRB 260610B: optical counterpart shows spectroscopic redshift of z=0.473 DATE: 26/06/11 13:44:50 GMT FROM: Ben Gompertz at U of Birmingham <b.gompertz(a)bham.ac.uk> D. O'Neill, J. Mills, M. Pursiainen, T. Killestein, D. B. Malesani, B. P. Gompertz, J. Lyman, R. Starling, K. Ackley, M. Dyer, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, B. Godson and A. Kumar report on behalf of the GOTO collaboration. We observed GOTO26fua/AT2026owq (O'Neill et al., GCN Circ. 44903, Watson et al., GCN Circ. 44905, Zhu et al. GCN Circ 44909, Gillanders et al. GCN Circ 44910, Akl et al. GCN Circ 44911), the optical counterpart of GRB 260610B (Fermi GBM team, GCN Circ. 44891), with the Alhambra Faint Object Spectrograph (ALFOSC) mounted on the Nordic Optical Telescope (NOT) as part of the GOTO Fast Analysis and Spectroscopy of Transients program (GOTO-FAST; Godson et al., AstroNote 2023-224). We obtained spectroscopy with ALFOSC, 2x900s total with grism #4, starting at 2026-06-10 02:10:00 (+2.5h post-trigger). We identify Mg II and Ca II absorption features at a common redshift of z=0.473, which we suggest to be the redshift of GRB 260610B. We also obtained multi-colour photometry starting at 2026-06-11 02:35 (+2.8h post-trigger) | MJD | T - T0 (hours) | Filter | AB mag | |------------ |---------------- |---------- |-------- | | 61202.1079 | 2.81 | g | 18.85 | | 61202.1090 | 2.84 | r | 18.40 | | 61202.1100 | 2.87 | i | 18.14 | | 61202.1111 | 2.90 | z | 17.92 | | 61202.1264 | 3.27 | g | 19.00 | | 61202.1275 | 3.29 | r | 18.49 | | 61202.1285 | 3.31 | i | 18.25 | | 61202.1296 | 3.34 | z | 18.04 | Magnitudes are reported in the AB system, calibrated against SDSS DR16 photometry, and are not corrected for foreground 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/44914. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43068] The EP-WXT trigger 01709269176 is likely a flaring star
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44913 SUBJECT: The EP-WXT trigger 01709269176 is likely a flaring star DATE: 26/06/11 12:55:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), Y.-H. I. Yin (HKU), H. Y. Ren, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709269176 at the time of 2026-06-11T12:25:32, is likely a stellar flare associated with Gaia DR3 1249275629854893952. The estimated flux of the flare is around 8 x 10^(-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.5 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/44913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43067] The EP-WXT trigger 01709269176 is likely a flaring star
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44913 SUBJECT: The EP-WXT trigger 01709269176 is likely a flaring star DATE: 26/06/11 12:55:49 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Zhou (PMO, CAS), Y.-H. I. Yin (HKU), H. Y. Ren, C. C. Jin (NAO, CAS) on behalf of the Einstein Probe (EP) team: The EP-WXT trigger 01709269176 at the time of 2026-06-11T12:25:32, is likely a stellar flare associated with Gaia DR3 1249275629854893952. The estimated flux of the flare is around 8 x 10^(-11) erg/s/cm^2 in 0.5-4.0 keV, corresponding to an X-ray luminosity of around 1.5 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/44913. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43066] EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44912 SUBJECT: EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations DATE: 26/06/11 12:50:17 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> C. L. Guo, H. Y. Ren, Z. X. Ling (NAO, CAS), H.Z. Wu (HUST, CAS) on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260610b was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission (Wu et al., GCN 44895), and followed by several telescopes (Levan et al. GCN 44897, Xin et al. GCN 44900, Zhu et al. GCN 44902, Burkhonov et al. GCN 44904, Méndez et al. GCN 44906). The WXT observation started at T0=2026-06-10 12:44:25 (UTC), and lasted for around 230 s before being interrupted by autonomous follow-up. The WXT light curve shows an increase in flux during the last 30 s. The average WXT 0.5–4 keV spectrum can be fitted with an absorbed power-law model with a fixed Galactic hydrogen column density of 2.43 × 10^20 cm^−2 and a photon index of 1.48 (+0.81/−0.70). The derived average unabsorbed 0.5–4 keV flux is 2.39 (+1.35/−0.90) × 10^−10 erg s^−1 cm^−2. The autonomous follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP started at 2026-06-10 12:50:34 (UTC), about 370s after T0. The exposure time was approximately 3726s. The on-ground analysis of the FXT data detected an uncatalogued X-ray source at R.A. = 267.6268 deg, DEC = 46.5388 deg (J2000), with an uncertainty of 10 arcsec in radius (90% C.L., including statistical and systematic uncertainties). The average FXT 0.5–10 keV spectrum can be fitted with an absorbed power-law model with a fixed Galactic hydrogen column density of 2.43 × 10^20 cm^−2 and a photon index of 2.19 (+0.1/−0.1). The derived average unabsorbed 0.5–10 keV flux is 7.36 (+0.4/−0.4) × 10^−12 erg s^−1 cm^−2. The uncertainties quoted above are at the 90% confidence level. Launched on January 9, 2024, EP is a space X-ray observatory designed 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/44912. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43065] GRB 260610B / AT 2026owq: COLIBRÍ optical observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44911 SUBJECT: GRB 260610B / AT 2026owq: COLIBRÍ optical observations DATE: 26/06/11 11:14:07 GMT FROM: Dalya Akl at New York University Abu Dhabi <dka2010(a)nyu.edu> GRB 260610B / AT 2026owq: COLIBRÍ optical observations Dalya Akl (NYUAD), Enrique Moreno Méndez (UNAM), Jean-Grégoire Ducoin (CPPM), 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), Sarah Antier (IJCLAB), Nathaniel R. Butler (ASU), Damien Dornic (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), 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 GOTO26fua/AT2026owq (O'Neill et al., GCN Circ. 44904), a possible counterpart of the Fermi GBM GRB 260610B (Fermi GBM team, GCN Circ. 44901), using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-11 06:51 to 08:13 UTC (from 7.08 to 8.45 hours after the GRB trigger) and obtained 15, 16, 15, 16, and 30 minutes, respectively, of exposure in the g, r, i, z, and y filters. The data were reduced, coadded, calibrated, and analysed with the COLIBRÍ pipeline. The photometry was calibrated using nearby stars from the PanSTARRS DR2 catalog, is in the AB system, and is not corrected for Galactic extinction. We detect the source AT2026owq with preliminary magnitudes of: g = 19.48 +/- 0.10 r = 19.02 +/- 0.03 i = 18.61 +/- 0.11 z = 18.54 +/- 0.08 y = 18.25 +/- 0.28 The absence of a strong break within our five filter measurements suggests a low-redshift event. Given the brightness, we encourage spectroscopic observations. Our values are consistent with those reported by GOTO (O'Neill et al., GCN Circ. 44903) and DDOTI (Watson et al., GCN Circ. 44905), given that the source continues to exhibit the same temporal decay reported by Watson et al. (GCN Circ. 44905), with a decay index of alpha ≈ -0.6. We thank the staff of the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir and the COLIBRÍ and DDRAGO engineering teams. COLIBRÍ is an astronomical observatory developed and operated jointly by France (AMU, CNES and CNRS) and México (UNAM and SECIHTI). It is located at the Observatorio Astronómico Nacional on the Sierra de San Pedro Mártir, Baja California, México. View this GCN Circular online at https://gcn.nasa.gov/circulars/44911. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43064] GRB 260610B / AT2026owq: Early ATLAS observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44910 SUBJECT: GRB 260610B / AT2026owq: Early ATLAS observations DATE: 26/06/11 11:00:56 GMT FROM: S. Srivastav at Oxford <shubhamsrivastav(a)gmail.com> J. H. Gillanders (Oxford), S. J. Smartt, K. W. Smith (Oxford, QUB), S. Srivastav, (Oxford), M. Nicholl, D. Young (QUB), T.-W. Chen (NCU, Taiwan), J. Tonry, L. Denneau, H. Weiland (IfA, University of Hawaii), N. Erasmus, W. Koorts (South African Astronomical Observatory), A. Jordan, V. Suc (UAI, Obstech), M. R. Alarcón, J. Licandro, P. Nichita (IAC), D. R. Young, M. Nicholl, T. Moore, J. Weston, X. Sheng, C. R. Angus, A. Wilson, A. Aamer, D. Magill, P. J. Broda, A. J. Smith (QUB), P. Ramsden (Birmingham/QUB), L. Shingles (GSI/QUB), H. Stevance, A. J. Cooper, F. Stoppa, J. Tweddle, L. Eastman (Oxford), L. Rhodes (TSI/McGill), A. Rest (STScI), C. Stubbs (Harvard), J. S. Sommer (LMU), B. P. Schmidt (ANU) The ATLAS survey comprises 5 optical telescopes situated around the globe (Hawaii x2, Chile, South Africa, Tenerife) that are continuously observing the night sky with a cadence of ~12-36 hours (Tonry et al., 2018; Licandro et al., 2023, 2025). Each point of the sky is imaged 4 times across a ~1 hour period so as to identify nearby moving objects. This high-cadence set of observations can also provide tight explosion constraints on extragalactic phenomena, provided an ATLAS unit is serendipitously pointing at the explosion site. Here we report ATLAS-Teide (the Tenerife unit) observations of the optical counterpart (AT2026owq; discovered by GOTO; O’Neill et al., GCN 44903; see also Watson et al., GCN 44905 and Zhu et al., GCN 44909) to GRB 260610B (detected by Fermi/GBM; GCN 44901). ATLAS-Teide observed the sky location of AT2026owq four times on MJDs 61201.96762, 61201.98177, 61201.99593 and 61202.01008 as part of regular survey operations. Each exposure lasted 30s and was acquired with the wide w-band filter (described by Tonry et al., 2025). The first and second exposures returned 5-sigma upper limits of >20.20 and >20.35 AB mag, respectively. The third and fourth exposures detected the transient, with magnitudes of w = 16.26+/-0.02 and w = 16.29+/-0.02 AB mag, respectively. Fermi/GBM reported the detection time of GRB 260610B (GCN 44901) to be MJD 61201.99044. This means that our third exposure, in which we first detected AT2026owq, was obtained just 7.9 minutes post-explosion. Similarly, our second exposure provides an upper limit corresponding to 12.5 minutes pre-explosion. We further note that although a host association is not obvious, the location of GRB 260610B / AT2026owq is in the vicinity of a number of nearby (z ~ 0.1, or D ~ 400-500 Mpc) galaxies; as such, further follow-up is scheduled to quantify the evolution of this (possibly low-z) GRB. The Asteroid Terrestrial-impact Last Alert System (ATLAS) project is primarily funded to search for Near-Earth asteroids through NASA grants NN12AR55G, 80NSSC18K0284, and 80NSSC18K1575; byproducts of the NEO search include images and catalogs from the survey area. This work was partially funded by Kepler/K2 grant J1944/80NSSC19K0112 and HST GO-15889, and STFC grants ST/T000198/1 and ST/S006109/1. The ATLAS science products have been made possible through the contributions of the University of Hawaii Institute for Astronomy, University of Oxford, the Queen's University Belfast, the Space Telescope Science Institute, the South African Astronomical Observatory, and The Millennium Institute of Astrophysics (MAS), Chile. View this GCN Circular online at https://gcn.nasa.gov/circulars/44910. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43063] GRB 260610B: TRT optical observation
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44909 SUBJECT: GRB 260610B: TRT optical observation DATE: 26/06/11 09:13:48 GMT FROM: Zipei Zhu at NAOC <zpzhu(a)nao.cas.cn> Z.-P. Zhu (NAOC), K. Noysena, K. Chanchaiworawit, S. Tinyanont (NARIT), J. An (NAOC), X. Liu, S.-Q. Jiang, L.-B. He, D. Xu (NAOC), S.-Y. Fu (HUST) report: We observed the field of GRB260610B detected by Fermi (Fermi GBM team, GCN 44901) , using the 0.7-m telescope of the Thai Robotic Telescope network (TRT), located at Fresno, California, U.S.A (SRO). Observation started at 2026-06-11 08:22:08 UT, i.e., ~ 0.36 days post-burst, and a series of R-band frames were obtained. The previously reported optical counterpart (O'Neill et al., GCN 44903; Watson et al., GCN 44905) is clearly detected in our stacked images with a brightness of R = 18.92 +/- 0.05, 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/44909. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43062] EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44908 SUBJECT: EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations DATE: 26/06/11 08:52:18 GMT FROM: EP Team at NAOC/CAS <ep_ta(a)bao.ac.cn> H. Y. Ren, C. L. Guo, Z. X. Ling (NAO, CAS), H.Z. Wu (HUST, CAS), on behalf of the Einstein Probe (EP) team: The fast X-ray transient EP260610a was detected by the Wide-field X-ray Telescope (WXT) on board the Einstein Probe (EP) mission at 2026-06-10T04:41:46 (UTC). We note that the trigger time reported in Wu et al., GCN 44889 was incorrect. The correct trigger time is 2026-06-10T04:49:21 (UTC). The WXT light curve lasted for around 450 seconds before the interruption of the autonomous follow-up. The average WXT 0.5–4 keV spectrum can be fitted with an absorbed power-law model with a fixed Galactic hydrogen column density of 0.46 × 10^21 cm^−2 and a photon index of 0.89 (+0.60/−0.57). The derived average unabsorbed 0.5–4 keV flux is 2.71 (+1.21/−0.70) × 10^−10 erg s^−1 cm^−2. The autonomous follow-up observation with the Follow-up X-ray Telescope (FXT) on board EP was performed at 2026-06-10T04:52:19 (UTC). The exposure time was approximately 3.5 ks. The on-ground analysis of the FXT data detected an uncatalogued X-ray source at R.A. = 306.1022 deg, DEC = −25.9045 deg (J2000), with an uncertainty of 10 arcsec in radius (90% C.L., including statistical and systematic uncertainties). The average FXT 0.5–10 keV spectrum can be fitted with an absorbed power-law model with a fixed Galactic hydrogen column density of 0.46 × 10^21 cm^−2 and a photon index of 1.95 (+0.07/−0.07). The derived average unabsorbed 0.5–10 keV flux is 0.82 (+0.06/−0.05) × 10^−11 erg s^−1 cm^−2. The uncertainties quoted above are at the 90% confidence level. We note that follow-up observations were carried out with COLIBRÍ (de Ugarte Postigo et al., GCN 44890) and SVOM/VT (Li et al., GCN 44896), but no optical counterpart was detected in these observations. Launched on January 9, 2024, EP is a space X-ray observatory designed 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/44908. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43061] GRB 260611A: Fermi GBM Final Real-time Localization
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44907 SUBJECT: GRB 260611A: Fermi GBM Final Real-time Localization DATE: 26/06/11 08:12:44 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 08:00:16 UT on 11 Jun 2026, the Fermi Gamma-ray Burst Monitor (GBM) triggered and located GRB 260611A (trigger 802857621.474604 / 260611334). The on-ground calculated location, using the Fermi GBM trigger data, is RA = 126.4, Dec = -41.2 (J2000 degrees, equivalent to J2000 08h 25m, -41d 12'), with a statistical uncertainty of 18.7 degrees. The angle from the Fermi LAT boresight is 111.0 degrees. The skymap can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611334/… The HEALPix FITS file, including the estimated localization systematic, can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611334/… The GBM light curve can be found here: https://heasarc.gsfc.nasa.gov/FTP/fermi/data/gbm/triggers/2026/bn260611334/… View this GCN Circular online at https://gcn.nasa.gov/circulars/44907. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43060] EP260610b: COLIBRÍ optical observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44906 SUBJECT: EP260610b: COLIBRÍ optical observations DATE: 26/06/11 06:56:12 GMT FROM: enriquemm(a)astro.unam.mx Enrique Moreno Méndez (UNAM), Dalya Akl (NYUAD), Rosa L. Becerra (UNAM), Stéphane Basa (UAR Pytheas), William H. Lee (UNAM), Edilberto Aguilar-Ruiz (UNAM), Jean-Luc Atteia (IRAP), Camila Angulo (UNAM), 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), 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 EP260610b (Wu et al., GCN Circ. 44895) using the DDRAGO two-channel wide-field imager on the COLIBRÍ telescope. We observed from 2026-06-11 05:16 to 06:32 UTC (from 16.48 to 17.73 hours after the trigger) and obtained 54 minutes of simultaneous exposure in the r/z filters. The data were reduced and coadded with the ASU COLIBRÍ 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 marginally detect the optical counterpart reported by Levan et al., GCN Circ. 44897, in the r band, at a preliminary magnitude of: r ≈ 23.7, In z, we do not detect the source down to the following 3-sigma limit: z > 22.0. These values are consistent with those reported by Gemini (Levan et al., GCN Circ. 44897), SVOM/VT (Xin et al., GCN Circ. 44900), NOT (Zhu et al., GCN Circ. 44902) and MAO/AZT-22 (Burkhonov et al., GCN Circ. 44904). 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/44906. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43059] GRB 260610B: DDOTI optical observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44905 SUBJECT: GRB 260610B: DDOTI optical observations DATE: 26/06/11 06:31:15 GMT FROM: Alan Watson at UNAM <alan(a)astro.unam.mx> Alan M. Watson (UNAM), Camila Angulo Valdez (UNAM), Rosa L. Becerra (UNAM), Nat Butler (ASU), Tsvetelina Dimitrova (ASU), William H. Lee (UNAM), and Margarita Pereyra (UNAM) report: We observed the field of GRB 260610B (Fermi Team, GCN Circ. 44901) with the DDOTI wide-field imager at the Observatorio Astronómico Nacional on Sierra San Pedro Mártir from 2026-06-11 04:53 to 05:44 UTC (5.1 to 5.9 hours after the trigger) obtaining total exposure of 27 minutes. We detect the candidate afterglow GOTO26fua/AT2026owq reported by O'Neill et al. (GCN Circ. 44903) with a preliminary AB magnitude of: w = 18.82 +/- 0.04 Compared to the observations reported by O'Neill et al. at 0.21 hours, the candidate continues to fade and has an estimated temporal decay index of approximately −0.6, in agreement with that measured by O'Neill et al. between 0.21 and 1.4 hours. We thank the staff of the Observatorio Astronómico Nacional on the Sierra of San Pedro Mártir. View this GCN Circular online at https://gcn.nasa.gov/circulars/44905. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43058] EP260610b: MAO/AZT-22 optical observations
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44904 SUBJECT: EP260610b: MAO/AZT-22 optical observations DATE: 26/06/11 04:37:49 GMT FROM: Yodgor Rajabov at UBAI <rajabov(a)astrin.uz> O. Burkhonov, Y. Rajabov, B.Abidkhanov, S. Ehgamberdiev, Y. Tillayev, T. Boyqobilov, A. Shaymanov report on behalf of UBAI team. We observed the field of EP transient EP260610b (Wu et al., GCN 44895), with the AZT-22 1.5m telescope of the Maidanak Observatory (MAO) starting on 2026-06-10 at 20:09:52 UT. In total we obtained 6x300 s exposures in the R-band using 4kx4k CCD SNUCAM camera (Im et al., 2010). The optical counterpart (Levan et al., GCN 44897; Xin et al., GCN 44900; Zhu et al., GCN 44902) is detected in the stacked frame. Preliminary photometry is the following: Date MidTime Exptime t-T0 Filter OT Err. UL SNR Site/Telescope (nxs) (mid, days) 2026-06-10T20:24:52 6x300 0,317072 R 22.85 0.15 23.26 6.4 MAO/AZT-22 All the data have been reduced by a single data processing pipeline, STDPipe (Karpov et al., 2022) web interface called STDweb (Karpov et al., 2025). Images obtained in Johnson Cousins filters were calibrated using the Gaia DR3 Synphot catalog. The data has not corrected for the Galactic extinction. Maidanak astronomical observatory (MAO) is an observational facility of the Ulugh Beg Astronomical Institute (UBAI), Uzbekistan Academy of Sciences (http://maidanak.uz/) View this GCN Circular online at https://gcn.nasa.gov/circulars/44904. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43057] EP260610b: NOT optical observation
by GCN Circulars 11 Jun '26

11 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 43056] GRB 260610B: GOTO optical counterpart candidate
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44903 SUBJECT: GRB 260610B: GOTO optical counterpart candidate DATE: 26/06/11 02:49:52 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, J. Mills, M. Pursiainen, J. Lyman, K. Ackley, M. Dyer, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, R. Starling, B. Gompertz, B. Godson, T. Killestein, A. Kumar, 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 260610B (GCN #44901). Observations covering the localisation area began at 2026-06-10 23:58:04 UT, (+0.2h post trigger) and continued through to 2026-06-11 00:31:39 UT (+0.76h post trigger). 63 images were taken, across 10 unique pointings, covering 241.5 sq. deg within the 90% localisation contour. ~89.6% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.6 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 (Lyman et al. 2026). A new optical source GOTO26fua/AT2026owq is identified within the GBM 90% localisation region (25% contour) with co-ordinates: RA,DEC (J2000) = 218.159414, 27.004935, 14:32:38.26, +27:00:17.76 The source was detected with L = 16.66 ± 0.01 AB mag (+0.21h) before fading to L = 17.83 ± 0.03 AB mag (+1.4h) with the light curve consistent with a decay index t^-0.56. We find no evidence of the source prior to the GRB trigger time in previous GOTO observations, the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021) at m_o > 19.45 mag (-38.99h). The temporal and spatial coincidence along with the power-law like decay strongly suggests this is the optical counterpart of GRB 260610B. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and 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/44903. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43055] EP260610b: NOT optical observation
by GCN Circulars 11 Jun '26

11 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 43054] GRB 260610B: GOTO optical counterpart candidate
by GCN Circulars 11 Jun '26

11 Jun '26

TITLE: GCN CIRCULAR NUMBER: 44903 SUBJECT: GRB 260610B: GOTO optical counterpart candidate DATE: 26/06/11 02:49:52 GMT FROM: d.s.oneill(a)bham.ac.uk D. O'Neill, J. Mills, M. Pursiainen, J. Lyman, K. Ackley, M. Dyer, K. Ulaczyk, D. Steeghs, D. Galloway, V. Dhillon, P. O'Brien, G. Ramsay, K. Noysena, R. Kotak, R. Breton, J. Casares, L. Nuttall, R. Starling, B. Gompertz, B. Godson, T. Killestein, A. Kumar, 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 260610B (GCN #44901). Observations covering the localisation area began at 2026-06-10 23:58:04 UT, (+0.2h post trigger) and continued through to 2026-06-11 00:31:39 UT (+0.76h post trigger). 63 images were taken, across 10 unique pointings, covering 241.5 sq. deg within the 90% localisation contour. ~89.6% of the total 2D localisation probability was covered, with an average 5-sigma depth of 20.6 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 (Lyman et al. 2026). A new optical source GOTO26fua/AT2026owq is identified within the GBM 90% localisation region (25% contour) with co-ordinates: RA,DEC (J2000) = 218.159414, 27.004935, 14:32:38.26, +27:00:17.76 The source was detected with L = 16.66 ± 0.01 AB mag (+0.21h) before fading to L = 17.83 ± 0.03 AB mag (+1.4h) with the light curve consistent with a decay index t^-0.56. We find no evidence of the source prior to the GRB trigger time in previous GOTO observations, the ZTF observations provided by the Lasair broker (Smith et al. 2019), or the ATLAS forced photometry server (Shingles et al. 2021) at m_o > 19.45 mag (-38.99h). The temporal and spatial coincidence along with the power-law like decay strongly suggests this is the optical counterpart of GRB 260610B. Magnitudes were calibrated using ATLAS-REFCAT2 (Tonry et al. 2018) and 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/44903. --- To unsubscribe, open this link in a web browser: https://gcn.nasa.gov/unsubscribe/eyJhbGciOiJIUzI1NiJ9.eyJlbWFpbCI6InZzbmV0L…

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[vsnet-grb-info 43053] EP260610b: NOT optical observation
by GCN Circulars 11 Jun '26

11 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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