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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"

27553 results found.

  1. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  2. Fermi GBM Sub-Threshold Detection of GRB 250610B
  3. GRB 250610B: Swift/UVOT Detection
  4. EP250610A: Swift/UVOT Upper limits
  5. EP250610a: TNG NIR upper limit
  6. GRB 250610B: REM optical/NIR observations
  7. EP250610a: Liverpool Telescope optical upper limits
  8. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  9. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  10. GRB 250610B: Swift-XRT counterpart detection
  11. GRB 250610B: LT detection of the optical counterpart
  12. GRB 250610B: OHP/T120 optical counterpart candidate
  13. GRB 250610C: Fermi GBM Final Real-time Localization
  14. GRB 250610B: SVOM detection of a long burst
  15. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  16. GRB 250610A: Fermi GBM Final Real-time Localization
  17. EP250610a: SVOM/VT optical upper limit
  18. EP250610a: REM optical/NIR observations
  19. EP250610a: Swift-XRT counterpart detection
  20. EP250610a: Einstein Probe detection of an X-ray transient
  21. GRB 250605A: Swift/UVOT Upper Limits
  22. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  23. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  24. GRB 250527C: CrAO Optical Upper Limit
  25. GRB 250609A: Fermi GBM Final Real-time Localization
  26. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  27. GRB 250607A: Fermi GBM Final Localization
  28. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  29. GRB 250605A: SVOM/VT optical upper limit
  30. GRB 250605A: Swift-XRT refined Analysis
  31. GRB 250605A: Enhanced Swift-XRT position
  32. GRB 250606A: Fermi GBM Final Real-time Localization
  33. GRB 250602A: GECAM detection
  34. GRB 250605A: LT optical observations
  35. GRB 250605A: Swift detection of a burst
  36. Konus-Wind detection of GRB 250601A
  37. IPN triangulation of GRB 250404B
  38. IPN triangulation of GRB 250529A
  39. GRB 250601A: PRIME H band upper limit.
  40. GRB 250601A: PRIME J band upper limit.
  41. GRB 250601A: VLT/FORS2 Optical Observation
  42. GRB 250601A: Fermi GBM Observation
  43. GRB 250603A: Swift/UVOT Upper Limits
  44. GRB 250603A: Swift-XRT refined Analysis
  45. GRB 250603A: Enhanced Swift-XRT position
  46. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  47. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  48. GRB 250602A: Fermi-LAT detection
  49. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  50. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  51. GRB 250601A: Swift/XRT candidate afterglow
  52. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  53. GRB 250601A: Swift-XRT observations
  54. GRB 250602A: Fermi GBM Final Real-time Localization
  55. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  56. GRB 250601A: Swift ToO observations
  57. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  58. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  59. GRB 250601A: Fermi GBM Final Real-time Localization
  60. EP#01709177494: SVOM/VT optical observations
  61. GRB 250531A: Fermi GBM Final Real-time Localization
  62. EP#01709177494: Swift-XRT counterpart detection of known source
  63. GRB 250530C: BOOTES-7 optical upper limit
  64. GRB 250530C: Swift-XRT refined Analysis
  65. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  66. GRB 250530C: Enhanced Swift-XRT position
  67. GRB 250530C: Swift detection of a burst
  68. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  69. GRB 250530A: EP-FXT counterpart detection
  70. GRB 250530A: SVOM/VT optical upper limit
  71. GRB 250530B: Fermi GBM Final Real-time Localization
  72. GRB 250530A: Swift-XRT counterpart detection
  73. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  74. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  75. GRB 250530A: SVOM detection of a burst
  76. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  77. GRB 250527C: Swift/UVOT Upper Limits
  78. EP J1350.0-8622: EP-FXT follow-up observation
  79. GRB 250529B: Fermi GBM Final Real-time Localization
  80. GRB 250527B: Swift-XRT observations
  81. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  82. GRB 250529A: Fermi GBM Final Real-time Localization
  83. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  84. GRB 250527C: Swift ToO observations
  85. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  86. GRB 250527B: Tiled Swift observations
  87. GRB 250520A: Gemini-South optical afterglow detection
  88. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  89. GRB 250527A: Fermi GBM Final Localization
  90. EP250526a: Einstein Probe detection of a fast X-ray transient
  91. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  92. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  93. GRB 250520A: 3 GHz MeerKAT Detection
  94. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  95. GRB 250521A: GRBAlpha detection
  96. GRB 250520A: GRBAlpha detection
  97. GRB 250523A: Fermi GBM Final Real-time Localization
  98. GRB 250521B: SVOM/VT optical upper limit
  99. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  100. GRB 250521B: EP-FXT follow-up observation and afterglow candidates

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