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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. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  2. GRB 250615A: COLIBRÍ optical upper limit
  3. GRB 250615A: DDOTI Optical Upper Limit
  4. GRB 250615A: Swift/UVOT Upper Limits
  5. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  6. GRB 250615A: Swift-XRT refined Analysis
  7. sb25061207/SVOM: T120 OHP optical upper limit
  8. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  9. Fermi trigger No 771752663: Global MASTER-Net observations report
  10. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  11. The EP-WXT trigger 01709178875 is likely a flaring star
  12. GRB 250615A: Enhanced Swift-XRT position
  13. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  14. GRB 250615A: Prompt enhanced Swift-XRT position
  15. GRB 250615A: Swift detection of a burst
  16. Swift GRB 250615A: Global MASTER-Net observations report
  17. Fermi trigger No 771718064: Global MASTER-Net observations report
  18. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  19. GRID detection of GRB 250612C
  20. sb25061207: Mephisto optical upper limits
  21. IceCube alert 141029_8144692 retraction
  22. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  23. GRB 250614A: Fermi GBM Final Real-time Localization
  24. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  25. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  26. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  27. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  28. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  29. Fermi trigger No 771494087: Global MASTER-Net observations report
  30. sb25061218: Swift-XRT observations
  31. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  32. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  33. sb25061207: EP-FXT follow-up observation and afterglow candidate
  34. GRB 250612B: Fermi GBM Observation
  35. EP250612a: SVOM/VT optical candidate
  36. Fermi trigger No 771424081: Global MASTER-Net observations report
  37. EP250612a: Global MASTER-Net observations report
  38. GRB 250612C: Fermi GBM Observation
  39. sb25061218: SVOM detection of a X-ray transient
  40. sb25061207: Swift-XRT observations
  41. EP250612a/GRB 250612B: JinShan optical upper limit
  42. EP 250612a: AST3-3 Yaoan Optical Observation
  43. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  44. sb25061207: SVOM/VT optical counterpart
  45. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  46. GRB 250610B: Swift-XRT refined Analysis
  47. GRB 250612C: Fermi GBM Final Real-time Localization
  48. EP250610a: Upper limit from Fermi-GBM Observations
  49. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  50. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  51. EP250612a: Einstein Probe detection of an X-ray transient
  52. GRB 250610B: Liverpool Telescope continued monitoring
  53. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  54. sb25061207: SVOM detection of a X-ray transient
  55. EP250610a: continuous follow-up observations with EP-FXT
  56. GRB 250610B - SVOM/ECLAIRs refined analysis
  57. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  58. Swift GRB250612.04: Global MASTER-Net observations report
  59. Fermi GBM Sub-Threshold Detection of GRB 250610B
  60. GRB 250610B: Swift/UVOT Detection
  61. EP250610A: Swift/UVOT Upper limits
  62. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  63. EP250610a: TNG NIR upper limit
  64. GRB 250610B: REM optical/NIR observations
  65. EP250610a: Liverpool Telescope optical upper limits
  66. GRB 250610B: SVOM/VT optical shallow decay
  67. GRB 250610B: additional Liverpool Telescope optical observations
  68. GRB 250610B: SVOM/GRM analysis
  69. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  70. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  71. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  72. GRB 250610B: Swift-XRT counterpart detection
  73. GRB 250610B: SVOM/VT optical counterpart
  74. GRB 250610B: LT detection of the optical counterpart
  75. GRB 250610B: OHP/T120 optical counterpart candidate
  76. GRB 250610C: Fermi GBM Final Real-time Localization
  77. GRB 250610B: GOTO optical upper limit
  78. EP250610a: Global MASTER-Net observations report
  79. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  80. GRB 250610B: SVOM detection of a long burst
  81. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  82. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  83. GRB 250610A: Fermi GBM Final Real-time Localization
  84. GRB 250605A: Swift-BAT refined analysis
  85. EP250610a: SVOM/VT optical upper limit
  86. EP250610a: REM optical/NIR observations
  87. GRB 250609A: Fermi GBM Observation
  88. GRBAlpha reentry on June 9, 2025
  89. EP250610a: Swift-XRT counterpart detection
  90. EP250610a: COLIBRÍ optical upper limit
  91. EP250610a: Einstein Probe detection of an X-ray transient
  92. Fermi trigger No 771072240: Global MASTER-Net observations report
  93. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  94. GRB 250605A: Swift/UVOT Upper Limits
  95. The EP-WXT trigger 01709178283 is likely a flaring star
  96. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  97. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  98. GRB 250527C: CrAO Optical Upper Limit
  99. GRB 250609A: Fermi GBM Final Real-time Localization
  100. GRB 250607A: SVOM/GRM observation of a long burst

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