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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"

32544 results found.

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

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