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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"

32542 results found.

  1. EP260610b: Gemini North optical counterpart candidate
  2. EP260610a: SVOM/VT optical upper limits
  3. Konus-Wind detection of GRB 260601A
  4. IPN triangulation of GRB 260601A (short/hard)
  5. GRB 260610A: Fermi GBM Final Real-time Localization (duplicate submission)
  6. EP260610a: COLIBRÍ optical upper limits
  7. Konus-Wind detection of GRB 260604C
  8. GRB 260608A: Fermi GRB Observation
  9. GRB 260604C: AstroSat CZTI detection
  10. IPN triangulation of GRB 260601B / EP260601a
  11. GRB 260604C: SVOM/ECLAIRs refined analysis
  12. GRB 260608A: SVOM/ECLAIRs refined analysis
  13. Konus-Wind detection of GRB 260607B
  14. GRB 260607B: GECAM-B observation
  15. GRB 260608C: Fermi GBM Final Real-time Localization (duplicate submission)
  16. GRB 260604C: further SAO RAS optical observations
  17. GRB 260607A: AT2026ong (GOTO26fqf) is a type-Ia SN
  18. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  19. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  20. GRB 260604C: SVOM/C-GFT upper limit
  21. GRB 260607B: AstroSat CZTI detection
  22. GRB 260608A: SVOM detection of a burst
  23. GRB 260608A: Fermi GBM Final Real-time Localization (duplicate submission)
  24. EP260605a: EP-FXT follow-up observation
  25. GRB 260607A: TRT optical observations
  26. GRB 260604C: GRANDMA further observations
  27. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  28. GRB 260604A: SVOM/GRM detection
  29. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  30. GRB 260607B: Fermi GBM Observation
  31. GRB 260607B: Fermi-LAT detection
  32. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  33. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  34. GRB 260607A: Fermi GBM Final Real-time Localization (duplicate submission)
  35. GRB 260604C: GECAM-B observation
  36. GRB 260604C: 6 GHz VLA observations
  37. GRB 260604C: SAO RAS optical observations
  38. GRB 260604C: GRANDMA observations
  39. GRB 260604B: SVOM/GRM detection
  40. GRB260603A: SVOM/ECLAIRs refined analysis
  41. EP260603a: COLIBRÍ optical upper limit
  42. GRB 260604A: Glowbug gamma-ray detection
  43. GRB 260604C: LCO optical upper limit
  44. GRB 260604C: Liverpool Telescope optical detection
  45. EP260602d: EP-FXT follow-up observation
  46. EP260602c: EP-FXT follow-up observation
  47. GRB 260601B / EP260601a: AstroSat CZTI detection
  48. GRB 260527A/EP260527a: 6 GHz VLA observations
  49. GRB 260604C: GOTO detections of the optical afterglow
  50. GRB 260604C: Correction to GCN 44828
  51. GRB 260604C: Kilonova-Catcher optical afterglow detection
  52. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  53. GRB 260604C: Jinshan optical observations
  54. GRB 260604C: Fermi GBM Observation
  55. EP260602d: J-band upper limit with WINTER
  56. EP260602b: J-band upper limit with WINTER
  57. GRB 260604C: LAST detection of optical counterpart candidate
  58. Fermi GRB 260604C: Global MASTER-Net observations report
  59. Fermi GRB 260604C: Global MASTER-Net observations report
  60. GRB 260604C: SVOM detection of a long burst
  61. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  62. GRB 260603A: NOT optical observations
  63. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  64. GRB 260601A: CALET Gamma-Ray Burst Monitor detection
  65. EP260602a: EP-FXT follow-up observation
  66. EP260603a: Global MASTER-Net observations report
  67. EP260602d: Optical Upper limits with kinder observations
  68. EP260602b: Liverpool Telescope observations
  69. EP260602a: Liverpool Telescope optical upper limits
  70. EP260602b: Liverpool Telescope and LCO observations
  71. EP260602a: GTC and Liverpool Telescope optical observations
  72. Konus-Wind detection of GRB 260601B/EP260601a
  73. GRB 260603A: EP-FXT follow-up observation
  74. EP260601a/GRB 260601B: EP-FXT follow-up observation
  75. GRB 260601B / EP260601a: Mondy optical upper limit
  76. EP260602b: EP-FXT follow-up observation
  77. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  78. GRB 260603A: Kilonova-Catcher optical upper limit
  79. GRB 260603A: SVOM/VT optical observations
  80. EP260602a: NOT NIR J-band observations
  81. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  82. EP260602d: Einstein Probe detection of a fast X-ray transient
  83. EP260602a: SVOM/VT optical magnitudes correction
  84. GRB 260601A: SVOM/GRM observation of a short burst
  85. EP260602c: Einstein Probe detection of a fast X-ray transient
  86. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  87. EP260602a: COLIBRÍ optical observations
  88. GRB260601B/EP260601a: NOT near-infrared observations
  89. EP260602b: Einstein Probe detection of a fast X-ray transient
  90. GRB 260601B/EP260601a: Insight-HXMT detection
  91. Fermi GRB 260602B: Global MASTER-Net observations report
  92. Fermi GRB 260602B: Global MASTER-Net observations report
  93. EP260602a: SVOM/VT optical candidate
  94. GRB 260601A: GECAM-B observation of a short burst
  95. GRB 260601B/EP260601a: J-band upper limit with WINTER
  96. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  97. EP260530a/AT 2026nwl: KAIT optical observations
  98. GRB 260601B: CALET Gamma-Ray Burst Monitor detection
  99. EP260602a: Optical upper limits with Kinder observations
  100. GRB 260601B / EP260601a: NuSTAR detection of prompt emission

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