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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45934 results found.

  1. EP#01709178975: Swift-XRT counterpart detection
  2. EP-WXT trigger 01709178975: GOTO optical upper limit
  3. The EP-WXT trigger 01709178975 is likely a flaring star
  4. Konus-Wind detection of GRB 250615A / EP250615a
  5. GRB 250615A / EP250615a: AstroSat CZTI detection
  6. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  7. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  8. GRB 250615A: COLIBRÍ optical upper limit
  9. GRB 250615A: DDOTI Optical Upper Limit
  10. GRB 250615A: Swift/UVOT Upper Limits
  11. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  12. GRB 250615A: Swift-XRT refined Analysis
  13. sb25061207/SVOM: T120 OHP optical upper limit
  14. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  15. Fermi trigger No 771752663: Global MASTER-Net observations report
  16. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  17. The EP-WXT trigger 01709178875 is likely a flaring star
  18. GRB 250615A: Enhanced Swift-XRT position
  19. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  20. GRB 250615A: Prompt enhanced Swift-XRT position
  21. GRB 250615A: Swift detection of a burst
  22. Swift GRB 250615A: Global MASTER-Net observations report
  23. Fermi trigger No 771718064: Global MASTER-Net observations report
  24. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  25. GRID detection of GRB 250612C
  26. sb25061207: Mephisto optical upper limits
  27. IceCube alert 141029_8144692 retraction
  28. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  29. GRB 250614A: Fermi GBM Final Real-time Localization
  30. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  31. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  32. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  33. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  34. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. Fermi trigger No 771494087: Global MASTER-Net observations report
  36. sb25061218: Swift-XRT observations
  37. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  38. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  39. sb25061207: EP-FXT follow-up observation and afterglow candidate
  40. GRB 250612B: Fermi GBM Observation
  41. EP250612a / GRB 250612B: SVOM/VT optical candidate
  42. Fermi trigger No 771424081: Global MASTER-Net observations report
  43. EP250612a: Global MASTER-Net observations report
  44. GRB 250612C: Fermi GBM Observation
  45. sb25061218: SVOM detection of a X-ray transient
  46. sb25061207: Swift-XRT observations
  47. EP250612a/GRB 250612B: JinShan optical upper limit
  48. EP 250612a: AST3-3 Yaoan Optical Observation
  49. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  50. sb25061207: SVOM/VT optical counterpart
  51. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  52. GRB 250610B: Swift-XRT refined Analysis
  53. GRB 250612C: Fermi GBM Final Real-time Localization
  54. EP250610a: Upper limit from Fermi-GBM Observations
  55. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  56. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  57. EP250612a: Einstein Probe detection of an X-ray transient
  58. GRB 250610B: Liverpool Telescope continued monitoring
  59. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  60. sb25061207: SVOM detection of a X-ray transient
  61. EP250610a: continuous follow-up observations with EP-FXT
  62. GRB 250610B - SVOM/ECLAIRs refined analysis
  63. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  64. Swift GRB250612.04: Global MASTER-Net observations report
  65. Fermi GBM Sub-Threshold Detection of GRB 250610B
  66. GRB 250610B: Swift/UVOT Detection
  67. EP250610A: Swift/UVOT Upper limits
  68. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  69. EP250610a: TNG NIR upper limit
  70. GRB 250610B: REM optical/NIR observations
  71. EP250610a: Liverpool Telescope optical upper limits
  72. GRB 250610B: SVOM/VT optical shallow decay
  73. GRB 250610B: additional Liverpool Telescope optical observations
  74. GRB 250610B: SVOM/GRM analysis
  75. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  76. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  77. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  78. GRB 250610B: Swift-XRT counterpart detection
  79. GRB 250610B: SVOM/VT optical counterpart
  80. GRB 250610B: LT detection of the optical counterpart
  81. GRB 250610B: OHP/T120 optical counterpart candidate
  82. GRB 250610C: Fermi GBM Final Real-time Localization
  83. GRB 250610B: GOTO optical upper limit
  84. EP250610a: Global MASTER-Net observations report
  85. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  86. GRB 250610B: SVOM detection of a long burst
  87. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  88. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 250610A: Fermi GBM Final Real-time Localization
  90. GRB 250605A: Swift-BAT refined analysis
  91. EP250610a: SVOM/VT optical upper limit
  92. EP250610a: REM optical/NIR observations
  93. GRB 250609A: Fermi GBM Observation
  94. GRBAlpha reentry on June 9, 2025
  95. EP250610a: Swift-XRT counterpart detection
  96. EP250610a: COLIBRÍ optical upper limit
  97. EP250610a: Einstein Probe detection of an X-ray transient
  98. Fermi trigger No 771072240: Global MASTER-Net observations report
  99. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  100. GRB 250605A: Swift/UVOT Upper Limits

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