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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"

28077 results found.

  1. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  2. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  3. GRB 250615A: Enhanced Swift-XRT position
  4. GRB 250615A: Prompt enhanced Swift-XRT position
  5. GRB 250615A: Swift detection of a burst
  6. GRID detection of GRB 250612C
  7. sb25061207: Mephisto optical upper limits
  8. IceCube alert 141029_8144692 retraction
  9. GRB 250614A: Fermi GBM Final Real-time Localization
  10. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  11. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  12. sb25061218: Swift-XRT observations
  13. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  14. sb25061207: EP-FXT follow-up observation and afterglow candidate
  15. sb25061218: SVOM detection of a X-ray transient
  16. sb25061207: Swift-XRT observations
  17. EP 250612a: AST3-3 Yaoan Optical Observation
  18. GRB 250610B: Swift-XRT refined Analysis
  19. GRB 250612C: Fermi GBM Final Real-time Localization
  20. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  21. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  22. EP250612a: Einstein Probe detection of an X-ray transient
  23. sb25061207: SVOM detection of a X-ray transient
  24. EP250610a: continuous follow-up observations with EP-FXT
  25. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  26. Fermi GBM Sub-Threshold Detection of GRB 250610B
  27. GRB 250610B: Swift/UVOT Detection
  28. EP250610A: Swift/UVOT Upper limits
  29. EP250610a: TNG NIR upper limit
  30. GRB 250610B: REM optical/NIR observations
  31. EP250610a: Liverpool Telescope optical upper limits
  32. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  33. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  34. GRB 250610B: Swift-XRT counterpart detection
  35. GRB 250610B: LT detection of the optical counterpart
  36. GRB 250610B: OHP/T120 optical counterpart candidate
  37. GRB 250610C: Fermi GBM Final Real-time Localization
  38. GRB 250610B: SVOM detection of a long burst
  39. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  40. GRB 250610A: Fermi GBM Final Real-time Localization
  41. EP250610a: SVOM/VT optical upper limit
  42. EP250610a: REM optical/NIR observations
  43. EP250610a: Swift-XRT counterpart detection
  44. EP250610a: Einstein Probe detection of an X-ray transient
  45. GRB 250605A: Swift/UVOT Upper Limits
  46. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  47. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  48. GRB 250527C: CrAO Optical Upper Limit
  49. GRB 250609A: Fermi GBM Final Real-time Localization
  50. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  51. GRB 250607A: Fermi GBM Final Localization
  52. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  53. GRB 250605A: SVOM/VT optical upper limit
  54. GRB 250605A: Swift-XRT refined Analysis
  55. GRB 250605A: Enhanced Swift-XRT position
  56. GRB 250606A: Fermi GBM Final Real-time Localization
  57. GRB 250602A: GECAM detection
  58. GRB 250605A: LT optical observations
  59. GRB 250605A: Swift detection of a burst
  60. Konus-Wind detection of GRB 250601A
  61. IPN triangulation of GRB 250404B
  62. IPN triangulation of GRB 250529A
  63. GRB 250601A: PRIME H band upper limit.
  64. GRB 250601A: PRIME J band upper limit.
  65. GRB 250601A: VLT/FORS2 Optical Observation
  66. GRB 250601A: Fermi GBM Observation
  67. GRB 250603A: Swift/UVOT Upper Limits
  68. GRB 250603A: Swift-XRT refined Analysis
  69. GRB 250603A: Enhanced Swift-XRT position
  70. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  71. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  72. GRB 250602A: Fermi-LAT detection
  73. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  74. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  75. GRB 250601A: Swift/XRT candidate afterglow
  76. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  77. GRB 250601A: Swift-XRT observations
  78. GRB 250602A: Fermi GBM Final Real-time Localization
  79. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  80. GRB 250601A: Swift ToO observations
  81. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  82. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  83. GRB 250601A: Fermi GBM Final Real-time Localization
  84. EP#01709177494: SVOM/VT optical observations
  85. GRB 250531A: Fermi GBM Final Real-time Localization
  86. EP#01709177494: Swift-XRT counterpart detection of known source
  87. GRB 250530C: BOOTES-7 optical upper limit
  88. GRB 250530C: Swift-XRT refined Analysis
  89. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  90. GRB 250530C: Enhanced Swift-XRT position
  91. GRB 250530C: Swift detection of a burst
  92. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  93. GRB 250530A: EP-FXT counterpart detection
  94. GRB 250530A: SVOM/VT optical upper limit
  95. GRB 250530B: Fermi GBM Final Real-time Localization
  96. GRB 250530A: Swift-XRT counterpart detection
  97. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  98. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  99. GRB 250530A: SVOM detection of a burst
  100. GRB 250527D: CALET Gamma-Ray Burst Monitor detection

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