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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"

23407 results found.

  1. GRB 260610B / AT2026owq: further SAO RAS optical observations
  2. EP260605a: COLIBRÍ optical upper limits
  3. GRB 260610b: Liverpool Telescope optical observations
  4. EP260610b: Liverpool Telescope optical upper limits
  5. The EP-WXT trigger 01709269176: SVOM/C-GFT confirmation of a stellar flare
  6. GRB 260610B: IAC-80 Optical observations
  7. GRB 260610B / AT2026owq: SAO RAS optical observations
  8. EP260610b: refined analysis of the EP-WXT and follow-up EP-FXT observations
  9. GRB 260610B / AT 2026owq: COLIBRÍ optical observations
  10. GRB 260610B: TRT optical observation
  11. EP260610a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  12. EP260610b: COLIBRÍ optical observations
  13. GRB 260610B: DDOTI optical observations
  14. EP260610b: MAO/AZT-22 optical observations
  15. EP260610b: NOT optical observation
  16. EP260610b: SVOM/VT optical confirmation with blue color
  17. GRB 260515A: SOAR optical observations
  18. EP260610b: Gemini North optical counterpart candidate
  19. EP260610a: SVOM/VT optical upper limits
  20. EP260610b: Einstein Probe detection of an X-ray transient
  21. IPN triangulation of GRB 260601A (short/hard)
  22. EP260610a: COLIBRÍ optical upper limits
  23. EP260610a: Einstein Probe detection of a fast X-ray transient
  24. GRB 260608A: Fermi GRB Observation
  25. IPN triangulation of GRB 260601B / EP260601a
  26. GRB 260604C: further SAO RAS optical observations
  27. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  28. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) colour evolution and confirmation of the late rebrightening
  29. GRB 260604C: SVOM/C-GFT upper limit
  30. EP260605a: EP-FXT follow-up observation
  31. GRB 260607A: TRT optical observations
  32. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  33. GRB 260604A: SVOM/GRM detection
  34. GRB 260604C: Mondy optical observations: evidence of a possible brightening
  35. GRB 260604C: Simeiz Zeiss-1000 optical observations of the afterglow
  36. GRB 260604C: OPD1.6m - GRANDMA observations - detection
  37. GRB 260604C: 6 GHz VLA observations
  38. GRB 260604C: SAO RAS optical observations
  39. GRB 260604B: SVOM/GRM detection
  40. EP260605a: Einstein Probe detection of a fast X-ray transient
  41. EP260603a: COLIBRÍ optical upper limit
  42. GRB 260604A: Glowbug gamma-ray detection
  43. GRB 260604C: LCO optical upper limit
  44. EP260602d: EP-FXT follow-up observation
  45. EP260602c: EP-FXT follow-up observation
  46. GRB 260527A/EP260527a: 6 GHz VLA observations
  47. GRB 260604C: Kilonova-Catcher optical afterglow detection
  48. GRB 260604C: SVOM/COLIBRÍ (FM-GFT) optical observations
  49. GRB 260604C: Jinshan optical observations
  50. GRB 260604C: Fermi GBM Observation
  51. EP260602d: J-band upper limit with WINTER
  52. EP260602b: J-band upper limit with WINTER
  53. GRB 260604C: LAST detection of optical counterpart candidate
  54. GRB 260515A: SVOM/VT optical detection at about 18 days post trigger
  55. GRB 260603A: Simeiz Zeiss-1000 optical upper limit
  56. EP260602a: EP-FXT follow-up observation
  57. EP260603a: Einstein Probe detection of a fast X-ray transient
  58. EP260602d: Optical Upper limits with kinder observations
  59. EP260602b: Liverpool Telescope observations
  60. EP260602a: Liverpool Telescope optical upper limits
  61. EP260602b: Liverpool Telescope and LCO observations
  62. EP260602a: GTC and Liverpool Telescope optical observations
  63. GRB 260601B / EP260601a: Mondy optical upper limit
  64. EP260602b: EP-FXT follow-up observation
  65. GRB 260601B/EP260601a: Glowbug gamma-ray detection
  66. GRB 260603A: Kilonova-Catcher optical upper limit
  67. GRB 260603A: SVOM/VT optical observations
  68. EP260602a: NOT NIR J-band observations
  69. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  70. EP260602d: Einstein Probe detection of a fast X-ray transient
  71. GRB 260601A: SVOM/GRM observation of a short burst
  72. EP260602c: Einstein Probe detection of a fast X-ray transient
  73. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  74. EP260602a: COLIBRÍ optical observations
  75. GRB260601B/EP260601a: NOT near-infrared observations
  76. EP260602b: Einstein Probe detection of a fast X-ray transient
  77. EP260602a: SVOM/VT optical candidate
  78. EP-WXT trigger 01709266414 (EP260602b): JinShan optical counterpart detection
  79. GRB 260601B/EP260601a: J-band upper limit with WINTER
  80. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  81. EP260530a/AT 2026nwl: KAIT optical observations
  82. EP260602a: Optical upper limits with Kinder observations
  83. EP260602a: Einstein Probe detection of a fast X-ray transient
  84. GRB 260601B/EP260601a: SVOM/VT optical observations
  85. EP260601a: Einstein Probe detection of an X-ray transient
  86. EP-WXT trigger 01709266307 (EP260601a): COLIBRÍ optical observations
  87. EP-WXT trigger 01709266307 (EP260601a): JinShan optical counterpart detection
  88. GRB 260601A: Glowbug gamma-ray detection of a short burst
  89. GRB 260531B: Glowbug gamma-ray detection
  90. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  91. GRB 260527A/EP260527a: Glowbug gamma-ray detection
  92. GRB 260531B: GECAM-B observation
  93. AT2026nik: EP-FXT X-ray counterpart
  94. AT 2026nuz: COLIBRÍ optical observations
  95. IPN triangulation of GRB 260527A / EP260527a
  96. GRB 260527A / EP260527a: VLA radio detection
  97. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  98. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  99. GRB 260527A/EP260527a: VLT/X-shooter tentative redshift
  100. EP260526a: SVOM/VT optical upper limits

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