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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. GRB 250615A: Swift detection of a burst
  2. Swift GRB 250615A: Global MASTER-Net observations report
  3. Fermi trigger No 771718064: Global MASTER-Net observations report
  4. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  5. GRID detection of GRB 250612C
  6. sb25061207: Mephisto optical upper limits
  7. IceCube alert 141029_8144692 retraction
  8. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  9. GRB 250614A: Fermi GBM Final Real-time Localization
  10. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  11. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  12. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  13. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  14. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  15. Fermi trigger No 771494087: Global MASTER-Net observations report
  16. sb25061218: Swift-XRT observations
  17. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  19. sb25061207: EP-FXT follow-up observation and afterglow candidate
  20. GRB 250612B: Fermi GBM Observation
  21. EP250612a: SVOM/VT optical candidate
  22. Fermi trigger No 771424081: Global MASTER-Net observations report
  23. EP250612a: Global MASTER-Net observations report
  24. GRB 250612C: Fermi GBM Observation
  25. sb25061218: SVOM detection of a X-ray transient
  26. sb25061207: Swift-XRT observations
  27. EP250612a/GRB 250612B: JinShan optical upper limit
  28. EP 250612a: AST3-3 Yaoan Optical Observation
  29. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  30. sb25061207: SVOM/VT optical counterpart
  31. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  32. GRB 250610B: Swift-XRT refined Analysis
  33. GRB 250612C: Fermi GBM Final Real-time Localization
  34. EP250610a: Upper limit from Fermi-GBM Observations
  35. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  36. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  37. EP250612a: Einstein Probe detection of an X-ray transient
  38. GRB 250610B: Liverpool Telescope continued monitoring
  39. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  40. sb25061207: SVOM detection of a X-ray transient
  41. EP250610a: continuous follow-up observations with EP-FXT
  42. GRB 250610B - SVOM/ECLAIRs refined analysis
  43. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  44. Swift GRB250612.04: Global MASTER-Net observations report
  45. Fermi GBM Sub-Threshold Detection of GRB 250610B
  46. GRB 250610B: Swift/UVOT Detection
  47. EP250610A: Swift/UVOT Upper limits
  48. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  49. EP250610a: TNG NIR upper limit
  50. GRB 250610B: REM optical/NIR observations
  51. EP250610a: Liverpool Telescope optical upper limits
  52. GRB 250610B: SVOM/VT optical shallow decay
  53. GRB 250610B: additional Liverpool Telescope optical observations
  54. GRB 250610B: SVOM/GRM analysis
  55. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  56. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  57. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  58. GRB 250610B: Swift-XRT counterpart detection
  59. GRB 250610B: SVOM/VT optical counterpart
  60. GRB 250610B: LT detection of the optical counterpart
  61. GRB 250610B: OHP/T120 optical counterpart candidate
  62. GRB 250610C: Fermi GBM Final Real-time Localization
  63. GRB 250610B: GOTO optical upper limit
  64. EP250610a: Global MASTER-Net observations report
  65. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  66. GRB 250610B: SVOM detection of a long burst
  67. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  68. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  69. GRB 250610A: Fermi GBM Final Real-time Localization
  70. GRB 250605A: Swift-BAT refined analysis
  71. EP250610a: SVOM/VT optical upper limit
  72. EP250610a: REM optical/NIR observations
  73. GRB 250609A: Fermi GBM Observation
  74. GRBAlpha reentry on June 9, 2025
  75. EP250610a: Swift-XRT counterpart detection
  76. EP250610a: COLIBRÍ optical upper limit
  77. EP250610a: Einstein Probe detection of an X-ray transient
  78. Fermi trigger No 771072240: Global MASTER-Net observations report
  79. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  80. GRB 250605A: Swift/UVOT Upper Limits
  81. The EP-WXT trigger 01709178283 is likely a flaring star
  82. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  83. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  84. GRB 250527C: CrAO Optical Upper Limit
  85. GRB 250609A: Fermi GBM Final Real-time Localization
  86. GRB 250607A: SVOM/GRM observation of a long burst
  87. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  88. The EP-WXT trigger 01709178244 is likely a flaring star
  89. GRB 250607A: Fermi GBM Final Localization
  90. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  91. The EP-WXT trigger 01709178069 is likely a flaring star
  92. GRB 250605A: SVOM/VT optical upper limit
  93. GRB 250605A: Swift-XRT refined Analysis
  94. EP/WXT 01709177873: GOTO observations confirm stellar variability
  95. GRB 250605A: Enhanced Swift-XRT position
  96. Fermi GRB 250606A: Global MASTER-Net observations report
  97. GRB 250606A: Fermi GBM Final Real-time Localization
  98. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  99. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  100. GRB 250602A: GECAM detection

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