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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: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  2. GRB 250617A: Fermi GBM Final Real-time Localization
  3. IPN triangulation of GRB 250612C (short/hard)
  4. EP#01709178975: Swift-XRT counterpart detection
  5. EP-WXT trigger 01709178975: GOTO optical upper limit
  6. The EP-WXT trigger 01709178975 is likely a flaring star
  7. Konus-Wind detection of GRB 250615A / EP250615a
  8. GRB 250615A / EP250615a: AstroSat CZTI detection
  9. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  10. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  11. GRB 250615A: COLIBRÍ optical upper limit
  12. GRB 250615A: DDOTI Optical Upper Limit
  13. GRB 250615A: Swift/UVOT Upper Limits
  14. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  15. GRB 250615A: Swift-XRT refined Analysis
  16. sb25061207/SVOM: T120 OHP optical upper limit
  17. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  18. Fermi trigger No 771752663: Global MASTER-Net observations report
  19. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  20. The EP-WXT trigger 01709178875 is likely a flaring star
  21. GRB 250615A: Enhanced Swift-XRT position
  22. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  23. GRB 250615A: Prompt enhanced Swift-XRT position
  24. GRB 250615A: Swift detection of a burst
  25. Swift GRB 250615A: Global MASTER-Net observations report
  26. Fermi trigger No 771718064: Global MASTER-Net observations report
  27. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  28. GRID detection of GRB 250612C
  29. sb25061207: Mephisto optical upper limits
  30. IceCube alert 141029_8144692 retraction
  31. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  32. GRB 250614A: Fermi GBM Final Real-time Localization
  33. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  34. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  35. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  36. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  37. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. Fermi trigger No 771494087: Global MASTER-Net observations report
  39. sb25061218: Swift-XRT observations
  40. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  42. sb25061207: EP-FXT follow-up observation and afterglow candidate
  43. GRB 250612B: Fermi GBM Observation
  44. EP250612a: SVOM/VT optical candidate
  45. Fermi trigger No 771424081: Global MASTER-Net observations report
  46. EP250612a: Global MASTER-Net observations report
  47. GRB 250612C: Fermi GBM Observation
  48. sb25061218: SVOM detection of a X-ray transient
  49. sb25061207: Swift-XRT observations
  50. EP250612a/GRB 250612B: JinShan optical upper limit
  51. EP 250612a: AST3-3 Yaoan Optical Observation
  52. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  53. sb25061207: SVOM/VT optical counterpart
  54. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  55. GRB 250610B: Swift-XRT refined Analysis
  56. GRB 250612C: Fermi GBM Final Real-time Localization
  57. EP250610a: Upper limit from Fermi-GBM Observations
  58. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  59. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  60. EP250612a: Einstein Probe detection of an X-ray transient
  61. GRB 250610B: Liverpool Telescope continued monitoring
  62. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  63. sb25061207: SVOM detection of a X-ray transient
  64. EP250610a: continuous follow-up observations with EP-FXT
  65. GRB 250610B - SVOM/ECLAIRs refined analysis
  66. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  67. Swift GRB250612.04: Global MASTER-Net observations report
  68. Fermi GBM Sub-Threshold Detection of GRB 250610B
  69. GRB 250610B: Swift/UVOT Detection
  70. EP250610A: Swift/UVOT Upper limits
  71. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  72. EP250610a: TNG NIR upper limit
  73. GRB 250610B: REM optical/NIR observations
  74. EP250610a: Liverpool Telescope optical upper limits
  75. GRB 250610B: SVOM/VT optical shallow decay
  76. GRB 250610B: additional Liverpool Telescope optical observations
  77. GRB 250610B: SVOM/GRM analysis
  78. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  79. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  80. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  81. GRB 250610B: Swift-XRT counterpart detection
  82. GRB 250610B: SVOM/VT optical counterpart
  83. GRB 250610B: LT detection of the optical counterpart
  84. GRB 250610B: OHP/T120 optical counterpart candidate
  85. GRB 250610C: Fermi GBM Final Real-time Localization
  86. GRB 250610B: GOTO optical upper limit
  87. EP250610a: Global MASTER-Net observations report
  88. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  89. GRB 250610B: SVOM detection of a long burst
  90. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  91. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250610A: Fermi GBM Final Real-time Localization
  93. GRB 250605A: Swift-BAT refined analysis
  94. EP250610a: SVOM/VT optical upper limit
  95. EP250610a: REM optical/NIR observations
  96. GRB 250609A: Fermi GBM Observation
  97. GRBAlpha reentry on June 9, 2025
  98. EP250610a: Swift-XRT counterpart detection
  99. EP250610a: COLIBRÍ optical upper limit
  100. EP250610a: Einstein Probe detection of an X-ray transient

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