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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"
  1. Konus-Wind detection of GRB 250615A / EP250615a
  2. GRB 250615A / EP250615a: AstroSat CZTI detection
  3. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  4. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  5. GRB 250615A: COLIBRÍ optical upper limit
  6. GRB 250615A: DDOTI Optical Upper Limit
  7. GRB 250615A: Swift/UVOT Upper Limits
  8. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  9. GRB 250615A: Swift-XRT refined Analysis
  10. sb25061207/SVOM: T120 OHP optical upper limit
  11. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  12. Fermi trigger No 771752663: Global MASTER-Net observations report
  13. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  14. The EP-WXT trigger 01709178875 is likely a flaring star
  15. GRB 250615A: Enhanced Swift-XRT position
  16. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  17. GRB 250615A: Prompt enhanced Swift-XRT position
  18. GRB 250615A: Swift detection of a burst
  19. Swift GRB 250615A: Global MASTER-Net observations report
  20. Fermi trigger No 771718064: Global MASTER-Net observations report
  21. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  22. GRID detection of GRB 250612C
  23. sb25061207: Mephisto optical upper limits
  24. IceCube alert 141029_8144692 retraction
  25. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  26. GRB 250614A: Fermi GBM Final Real-time Localization
  27. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  28. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  29. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  30. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  31. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  32. Fermi trigger No 771494087: Global MASTER-Net observations report
  33. sb25061218: Swift-XRT observations
  34. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  36. sb25061207: EP-FXT follow-up observation and afterglow candidate
  37. GRB 250612B: Fermi GBM Observation
  38. EP250612a: SVOM/VT optical candidate
  39. Fermi trigger No 771424081: Global MASTER-Net observations report
  40. EP250612a: Global MASTER-Net observations report
  41. GRB 250612C: Fermi GBM Observation
  42. sb25061218: SVOM detection of a X-ray transient
  43. sb25061207: Swift-XRT observations
  44. EP250612a/GRB 250612B: JinShan optical upper limit
  45. EP 250612a: AST3-3 Yaoan Optical Observation
  46. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  47. sb25061207: SVOM/VT optical counterpart
  48. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  49. GRB 250610B: Swift-XRT refined Analysis
  50. GRB 250612C: Fermi GBM Final Real-time Localization
  51. EP250610a: Upper limit from Fermi-GBM Observations
  52. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  53. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  54. EP250612a: Einstein Probe detection of an X-ray transient
  55. GRB 250610B: Liverpool Telescope continued monitoring
  56. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  57. sb25061207: SVOM detection of a X-ray transient
  58. EP250610a: continuous follow-up observations with EP-FXT
  59. GRB 250610B - SVOM/ECLAIRs refined analysis
  60. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  61. Swift GRB250612.04: Global MASTER-Net observations report
  62. Fermi GBM Sub-Threshold Detection of GRB 250610B
  63. GRB 250610B: Swift/UVOT Detection
  64. EP250610A: Swift/UVOT Upper limits
  65. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  66. EP250610a: TNG NIR upper limit
  67. GRB 250610B: REM optical/NIR observations
  68. EP250610a: Liverpool Telescope optical upper limits
  69. GRB 250610B: SVOM/VT optical shallow decay
  70. GRB 250610B: additional Liverpool Telescope optical observations
  71. GRB 250610B: SVOM/GRM analysis
  72. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  73. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  74. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  75. GRB 250610B: Swift-XRT counterpart detection
  76. GRB 250610B: SVOM/VT optical counterpart
  77. GRB 250610B: LT detection of the optical counterpart
  78. GRB 250610B: OHP/T120 optical counterpart candidate
  79. GRB 250610C: Fermi GBM Final Real-time Localization
  80. GRB 250610B: GOTO optical upper limit
  81. EP250610a: Global MASTER-Net observations report
  82. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  83. GRB 250610B: SVOM detection of a long burst
  84. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  85. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 250610A: Fermi GBM Final Real-time Localization
  87. GRB 250605A: Swift-BAT refined analysis
  88. EP250610a: SVOM/VT optical upper limit
  89. EP250610a: REM optical/NIR observations
  90. GRB 250609A: Fermi GBM Observation
  91. GRBAlpha reentry on June 9, 2025
  92. EP250610a: Swift-XRT counterpart detection
  93. EP250610a: COLIBRÍ optical upper limit
  94. EP250610a: Einstein Probe detection of an X-ray transient
  95. Fermi trigger No 771072240: Global MASTER-Net observations report
  96. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  97. GRB 250605A: Swift/UVOT Upper Limits
  98. The EP-WXT trigger 01709178283 is likely a flaring star
  99. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  100. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)

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