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GCN Circulars

GCN Circulars are rapid astronomical bulletins submitted by and distributed to community members worldwide. They are used to share discoveries, observations, quantitative near-term predictions, requests for follow-up observations, or future observing plans related to high-energy, multi-messenger, and variable or transient astrophysical events. 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"

37956 results found.

  1. Konus-Wind detection of GRB 260316B (duplicate submission)
  2. Konus-Wind detection of GRB 260316B
  3. GRB 260321A: SVOM/ECLAIRs refined analysis
  4. EP260329b: J-band upper limits with WINTER
  5. EP260329a: J-band upper limit with WINTER
  6. GRB 260330A: Glowbug gamma-ray detection
  7. GRB 260310A: VLA Multi-frequency Radio Observations
  8. Fermi GBM Sub-Threshold Detection of GRB 260330B
  9. GRB 260330B: LCO optical upper limits
  10. GRB 260330B: SVOM detection of a burst
  11. GRB 260330A: Fermi GBM Final Real-time Localization
  12. EP260329b: Global MASTER-Net observations report
  13. Fermi trigger No 796485221: Global MASTER-Net observations report
  14. GRB 260327A: Insight-HXMT/HE detection
  15. GRB 260326A: Insight-HXMT/HE detection
  16. GRID detection of GRB 260326A
  17. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  18. SMA Detection of GRB 260310A / AT 2026fgk
  19. GRB 260307B: ATCA Radio Upper Limits
  20. GRB 260327A: AstroSat CZTI detection of a long burst
  21. EP260327a: Global MASTER-Net observations report
  22. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  23. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  24. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  25. IPN triangulation of GRB 260320A
  26. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  27. GRB 260326A: Fermi GBM Detection
  28. GRB 260325A: Fermi GBM Final Localization
  29. GRB 260326A: Fermi GBM Final Real-time Localization
  30. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  31. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  32. IPN triangulation of GRB 260316B
  33. GRID detection of GRB 260320A
  34. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  35. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  36. GRB 260310A: LBT optical observations
  37. EP260321A: Mondy optical observations
  38. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  39. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  40. Fermi GRB 260323A: Global MASTER-Net observations report
  41. GRB 260323A: Fermi GBM Final Real-time Localization
  42. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  43. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  44. GRB 260322A: Fermi GBM Final Localization
  45. GRB 260320A: Glowbug gamma-ray detection
  46. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  47. GRB 260321A: EP-FXT follow-up observation
  48. GRB 260321A: SVOM/VT optical upper limits
  49. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 260320A: Insight-HXMT/HE detection
  51. GRB 260310A: continued optical observation at Mondy
  52. Fermi GBM Sub-Threshold Detection of GRB 260321A
  53. GRB 260321A: SVOM detection of a burst
  54. EP260321a: Global MASTER-Net observations report
  55. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  56. GRB 260318A: Glowbug gamma-ray detection
  57. GRB 260310A / AT 2026fgk: KAIT optical observations
  58. GRB 260320A: NuSTAR detection of prompt emission
  59. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  60. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  61. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  62. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  63. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  64. GRB 260310A/AT2026fgk: LBT near-infrared observations
  65. NOEMA Detection of GRB 260310A / AT 2026fgk
  66. GRB 260318A: SVOM/GRM observation
  67. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  68. GRB 260318A: GECAM-B observation
  69. Fermi GRB 260318A: Global MASTER-Net observations report
  70. GRB 260318A: Fermi GBM Final Real-time Localization
  71. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  72. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  73. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  74. GRB 260310A / AT 2026fgk: radio detection with the VLA
  75. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  76. GRB 260310A / AT2026fgk: LCO optical observations
  77. GRB 260317A: Fermi GBM Final Localization
  78. GRB 260316B: GECAM-B observation
  79. GRB 260316B: SVOM/GRM observation
  80. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  81. GRB 260316B: AstroSat CZTI detection
  82. GRB 260316B: Fermi GBM Final Real-time Localization
  83. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  84. GRB 260314A: Glowbug gamma-ray detection
  85. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  86. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  87. GRB 260310A / AT 2026fgk: iTelescope optical observations
  88. GRID detection of GRB 260312B
  89. EP260314a: Global MASTER-Net observations report
  90. Fermi trigger No 795185313: Global MASTER-Net observations report
  91. IceCube Alert 260315A: Global MASTER-Net observations report
  92. GRB 260314A: GECAM-B observation of a burst
  93. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  94. GRB 260310A / AT2026fgk: SAO RAS optical observations
  95. GRB 260310A/AT2026fgk: radio detection at 15GHz
  96. GRB 260310A / AT2026fgk: TNG NIR detection
  97. GRB 260310A / AT2026fgk: OASDG optical observations
  98. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  99. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  100. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay

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