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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"

14825 results found.

  1. GRB 250615A: COLIBRÍ optical upper limit
  2. GRB 250615A: DDOTI Optical Upper Limit
  3. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  4. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  5. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  6. GRB 250615A: Swift detection of a burst
  7. GRID detection of GRB 250612C
  8. sb25061207: Mephisto optical upper limits
  9. IceCube alert 141029_8144692 retraction
  10. GRB 250614A: Fermi GBM Final Real-time Localization
  11. sb25061207: EP-FXT follow-up observation and afterglow candidate
  12. sb25061218: SVOM detection of a X-ray transient
  13. EP 250612a: AST3-3 Yaoan Optical Observation
  14. GRB 250612C: Fermi GBM Final Real-time Localization
  15. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  16. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  17. EP250612a: Einstein Probe detection of an X-ray transient
  18. sb25061207: SVOM detection of a X-ray transient
  19. EP250610a: continuous follow-up observations with EP-FXT
  20. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  21. Fermi GBM Sub-Threshold Detection of GRB 250610B
  22. GRB 250610B: Swift/UVOT Detection
  23. EP250610a: Liverpool Telescope optical upper limits
  24. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  25. GRB 250610B: Swift-XRT counterpart detection
  26. GRB 250610B: LT detection of the optical counterpart
  27. GRB 250610C: Fermi GBM Final Real-time Localization
  28. GRB 250610B: SVOM detection of a long burst
  29. GRB 250610A: Fermi GBM Final Real-time Localization
  30. EP250610a: Swift-XRT counterpart detection
  31. EP250610a: Einstein Probe detection of an X-ray transient
  32. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  33. GRB 250609A: Fermi GBM Final Real-time Localization
  34. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  35. GRB 250607A: Fermi GBM Final Localization
  36. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  37. GRB 250606A: Fermi GBM Final Real-time Localization
  38. GRB 250602A: GECAM detection
  39. GRB 250605A: LT optical observations
  40. GRB 250605A: Swift detection of a burst
  41. Konus-Wind detection of GRB 250601A
  42. IPN triangulation of GRB 250404B
  43. IPN triangulation of GRB 250529A
  44. GRB 250601A: PRIME H band upper limit.
  45. GRB 250601A: PRIME J band upper limit.
  46. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  47. GRB 250602A: Fermi-LAT detection
  48. GRB 250601A: Swift/XRT candidate afterglow
  49. GRB 250602A: Fermi GBM Final Real-time Localization
  50. GRB 250601A: Fermi GBM Final Real-time Localization
  51. EP#01709177494: SVOM/VT optical observations
  52. GRB 250531A: Fermi GBM Final Real-time Localization
  53. EP#01709177494: Swift-XRT counterpart detection of known source
  54. GRB 250530C: BOOTES-7 optical upper limit
  55. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  56. GRB 250530C: Swift detection of a burst
  57. GRB 250530A: EP-FXT counterpart detection
  58. GRB 250530A: SVOM/VT optical upper limit
  59. GRB 250530B: Fermi GBM Final Real-time Localization
  60. GRB 250530A: Swift-XRT counterpart detection
  61. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  62. GRB 250530A: SVOM detection of a burst
  63. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  64. EP J1350.0-8622: EP-FXT follow-up observation
  65. GRB 250529B: Fermi GBM Final Real-time Localization
  66. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  67. GRB 250529A: Fermi GBM Final Real-time Localization
  68. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  69. GRB 250520A: Gemini-South optical afterglow detection
  70. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  71. GRB 250527A: Fermi GBM Final Localization
  72. EP250526a: Einstein Probe detection of a fast X-ray transient
  73. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  74. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  75. GRB 250520A: 3 GHz MeerKAT Detection
  76. GRB 250521A: GRBAlpha detection
  77. GRB 250520A: GRBAlpha detection
  78. GRB 250523A: Fermi GBM Final Real-time Localization
  79. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  80. GRB 250522B: Fermi GBM Final Localization
  81. GRB 250522A: Fermi GBM Final Real-time Localization
  82. EP#01709176612: Swift-XRT counterpart detection of flaring star
  83. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  84. GRB 250521D: LAST tentative optical counterpart candidate
  85. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  86. GRB 250521D: Fermi GBM Final Real-time Localization
  87. GRB 250521C: Fermi GBM Final Localization
  88. GRB 250521B: SVOM detection of a burst through offline search
  89. Konus-Wind detection of GRB 250520A (short/hard)
  90. GRB 250521A: Fermi GBM Final Real-time Localization
  91. Konus-Wind detection of GRB 250516B
  92. IPN triangulation of GRB 250516B
  93. GRB 250520B: Fermi GBM Final Real-time Localization
  94. GRB 250520A: COLIBRÍ optical upper limit
  95. GRB 250520A: AstroSat CZTI detection of a short burst
  96. GRB 250516B: GRBAlpha detection
  97. GRB 250520A: Swift detection of a burst
  98. GRB 250516B: Insight-HXMT detection
  99. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  100. Konus-Wind detection of GRB 250516A

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