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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. See the documentation for help with subscribing to or submitting Circulars.

Search for Circulars by submitter, subject, or body text (e.g. 'Fermi GRB').
To navigate to a specific circular, enter the associated Circular ID (e.g. 'gcn123', 'Circular 123', or '123').
Advanced Search

To narrow the search results, use advanced search syntax. This allows for specifying which circular field to search (submitter, subject, and/or body). For additional information, refer to the advanced search documentation.

Advanced Search Examples (click to copy):

subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

39265 results found.

  1. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  2. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  3. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  4. IPN triangulation of GRB 260320A
  5. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  6. GRB 260326A: Fermi GBM Detection
  7. EP260321a: JinShan near-infrared observations
  8. GRB 260325A: Fermi GBM Final Localization
  9. GRB 260326A: Fermi GBM Final Real-time Localization
  10. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  11. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  12. IPN triangulation of GRB 260316B
  13. GRID detection of GRB 260320A
  14. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  15. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  16. GRB 260310A: LBT optical observations
  17. EP260321A: Mondy optical observations
  18. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  19. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  20. Fermi GRB 260323A: Global MASTER-Net observations report
  21. GRB 260323A: Fermi GBM Final Real-time Localization
  22. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  23. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  24. GRB 260322A: Fermi GBM Final Localization
  25. GRB 260320A: Glowbug gamma-ray detection
  26. EP260321a: COLIBRÍ further optical observations and brightening
  27. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  28. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  29. GRB 260321A: EP-FXT follow-up observation
  30. GRB 260321A: SVOM/VT optical upper limits
  31. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. GRB 260320A: Insight-HXMT/HE detection
  33. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  34. GRB 260310A: continued optical observation at Mondy
  35. Fermi GBM Sub-Threshold Detection of GRB 260321A
  36. GRB 260321A: SVOM detection of a burst
  37. EP260321a: Global MASTER-Net observations report
  38. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  39. GRB 260318A: Glowbug gamma-ray detection
  40. GRB 260310A / AT 2026fgk: KAIT optical observations
  41. GRB 260320A: NuSTAR detection of prompt emission
  42. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  43. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  44. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  45. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  46. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  47. GRB 260310A/AT2026fgk: LBT near-infrared observations
  48. NOEMA Detection of GRB 260310A / AT 2026fgk
  49. GRB 260318A: SVOM/GRM observation
  50. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  51. GRB 260318A: GECAM-B observation
  52. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  53. Fermi GRB 260318A: Global MASTER-Net observations report
  54. GRB 260318A: Fermi GBM Final Real-time Localization
  55. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  56. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  57. GRB 260310A / AT 2026fgk: radio detection with the VLA
  58. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  59. GRB 260310A / AT2026fgk: LCO optical observations
  60. GRB 260317A: Fermi GBM Final Localization
  61. GRB 260316B: GECAM-B observation
  62. GRB 260316B: SVOM/GRM observation
  63. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  64. EP260316a: COLIBRÍ faint optical counterpart candidate
  65. GRB 260316B: AstroSat CZTI detection
  66. GRB 260316B: Fermi GBM Final Real-time Localization
  67. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  68. GRB 260314A: Glowbug gamma-ray detection
  69. IceCube-260315A: COLIBRÍ optical observations
  70. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  71. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  72. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  73. GRB 260310A / AT 2026fgk: iTelescope optical observations
  74. EP260314a: COLIBRÍ optical upper limit
  75. GRID detection of GRB 260312B
  76. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  77. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260314a: Global MASTER-Net observations report
  79. Fermi trigger No 795185313: Global MASTER-Net observations report
  80. IceCube Alert 260315A: Global MASTER-Net observations report
  81. GRB 260314A: GECAM-B observation of a burst
  82. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  83. GRB 260310A / AT2026fgk: SAO RAS optical observations
  84. GRB 260310A/AT2026fgk: radio detection at 15GHz
  85. GRB 260310A / AT2026fgk: TNG NIR detection
  86. GRB 260310A / AT2026fgk: OASDG optical observations
  87. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  88. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  89. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  90. Fermi GRB 260314A: Global MASTER-Net observations report
  91. Fermi GRB 260313A: Global MASTER-Net observations report
  92. GRB 260314A: Fermi GBM Final Real-time Localization
  93. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  94. GRB 260313A: A Correction to the Fermi GBM Final Localization
  95. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  96. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  97. GRB 260310B: Insight-HXMT/HE detection
  98. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  99. GRB 260310A: NOT optical polarimetry
  100. GRB 260312B: AstroSat CZTI detection

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