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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"

36195 results found.

  1. EP260329b: J-band upper limits with WINTER
  2. EP260329a: J-band upper limit with WINTER
  3. GRB 260330A: Glowbug gamma-ray detection
  4. GRB 260310A: VLA Multi-frequency Radio Observations
  5. Fermi GBM Sub-Threshold Detection of GRB 260330B
  6. GRB 260330B: LCO optical upper limits
  7. GRB 260330B: SVOM detection of a burst
  8. GRB 260330A: Fermi GBM Final Real-time Localization
  9. GRB 260327A: Insight-HXMT/HE detection
  10. GRB 260326A: Insight-HXMT/HE detection
  11. GRID detection of GRB 260326A
  12. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  13. SMA Detection of GRB 260310A / AT 2026fgk
  14. GRB 260307B: ATCA Radio Upper Limits
  15. GRB 260327A: AstroSat CZTI detection of a long burst
  16. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  17. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  18. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  19. IPN triangulation of GRB 260320A
  20. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  21. GRB 260326A: Fermi GBM Detection
  22. GRB 260325A: Fermi GBM Final Localization
  23. GRB 260326A: Fermi GBM Final Real-time Localization
  24. EP260321a: Upper limits from a neutrino search with IceCube
  25. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  26. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  27. IPN triangulation of GRB 260316B
  28. GRID detection of GRB 260320A
  29. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  30. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  31. GRB 260310A: LBT optical observations
  32. EP260321A: Mondy optical observations
  33. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  34. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  35. Fermi GRB 260323A: Global MASTER-Net observations report
  36. GRB 260323A: Fermi GBM Final Real-time Localization
  37. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  38. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  39. GRB 260322A: Fermi GBM Final Localization
  40. GRB 260320A: Glowbug gamma-ray detection
  41. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  42. GRB 260321A: EP-FXT follow-up observation
  43. GRB 260321A: SVOM/VT optical upper limits
  44. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  45. GRB 260320A: Insight-HXMT/HE detection
  46. GRB 260310A: continued optical observation at Mondy
  47. Fermi GBM Sub-Threshold Detection of GRB 260321A
  48. GRB 260321A: SVOM detection of a burst
  49. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  50. GRB 260318A: Glowbug gamma-ray detection
  51. GRB 260310A / AT 2026fgk: KAIT optical observations
  52. GRB 260320A: NuSTAR detection of prompt emission
  53. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  54. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  55. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  56. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  57. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  58. GRB 260310A/AT2026fgk: LBT near-infrared observations
  59. NOEMA Detection of GRB 260310A / AT 2026fgk
  60. GRB 260318A: SVOM/GRM observation
  61. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  62. GRB 260318A: GECAM-B observation
  63. Fermi GRB 260318A: Global MASTER-Net observations report
  64. GRB 260318A: Fermi GBM Final Real-time Localization
  65. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  66. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  67. GRB 260310A / AT 2026fgk: radio detection with the VLA
  68. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  69. GRB 260310A / AT2026fgk: LCO optical observations
  70. GRB 260317A: Fermi GBM Final Localization
  71. GRB 260316B: GECAM-B observation
  72. GRB 260316B: SVOM/GRM observation
  73. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  74. GRB 260316B: AstroSat CZTI detection
  75. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  76. GRB 260316B: Fermi GBM Final Real-time Localization
  77. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  78. GRB 260314A: Glowbug gamma-ray detection
  79. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  80. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  81. GRB 260310A / AT 2026fgk: iTelescope optical observations
  82. GRID detection of GRB 260312B
  83. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  84. GRB 260314A: GECAM-B observation of a burst
  85. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  86. GRB 260310A / AT2026fgk: SAO RAS optical observations
  87. GRB 260310A/AT2026fgk: radio detection at 15GHz
  88. GRB 260310A / AT2026fgk: TNG NIR detection
  89. GRB 260310A / AT2026fgk: OASDG optical observations
  90. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  91. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  92. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  93. Fermi GRB 260314A: Global MASTER-Net observations report
  94. Fermi GRB 260313A: Global MASTER-Net observations report
  95. GRB 260314A: Fermi GBM Final Real-time Localization
  96. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  97. GRB 260313A: A Correction to the Fermi GBM Final Localization
  98. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  99. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  100. GRB 260310B: Insight-HXMT/HE detection

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