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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"

37674 results found.

  1. GRB 250617B: Enhanced Swift-XRT position
  2. GRB 250617B: Fermi GBM Observation
  3. GRB 250615A: Swift-BAT refined analysis
  4. GRB 250617B: Fermi GBM Final Localization
  5. GRB 250617B: Ondrejov D50 optical afterglow detection
  6. GRB 250617B: SAO RAS optical observations
  7. GRB 250617B: Swift detection of a burst with an optical counterpart
  8. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  9. GRB 250617A: Fermi GBM Final Real-time Localization
  10. IPN triangulation of GRB 250612C (short/hard)
  11. Konus-Wind detection of GRB 250615A / EP250615a
  12. GRB 250615A / EP250615a: AstroSat CZTI detection
  13. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  14. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  15. GRB 250615A: COLIBRÍ optical upper limit
  16. GRB 250615A: DDOTI Optical Upper Limit
  17. GRB 250615A: Swift/UVOT Upper Limits
  18. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  19. GRB 250615A: Swift-XRT refined Analysis
  20. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  21. Fermi trigger No 771752663: Global MASTER-Net observations report
  22. GRB 250615A: Enhanced Swift-XRT position
  23. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  24. GRB 250615A: Prompt enhanced Swift-XRT position
  25. GRB 250615A: Swift detection of a burst
  26. Swift GRB 250615A: Global MASTER-Net observations report
  27. Fermi trigger No 771718064: Global MASTER-Net observations report
  28. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  29. GRID detection of GRB 250612C
  30. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  31. GRB 250614A: Fermi GBM Final Real-time Localization
  32. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  33. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  34. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  35. Fermi trigger No 771494087: Global MASTER-Net observations report
  36. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  38. GRB 250612B: Fermi GBM Observation
  39. EP250612a / GRB 250612B: SVOM/VT optical candidate
  40. Fermi trigger No 771424081: Global MASTER-Net observations report
  41. GRB 250612C: Fermi GBM Observation
  42. EP250612a/GRB 250612B: JinShan optical upper limit
  43. EP 250612a: AST3-3 Yaoan Optical Observation
  44. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  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. GRB 250610B: Liverpool Telescope continued monitoring
  52. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  53. GRB 250610B - SVOM/ECLAIRs refined analysis
  54. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  55. Fermi GBM Sub-Threshold Detection of GRB 250610B
  56. GRB 250610B: Swift/UVOT Detection
  57. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  58. GRB 250610B: REM optical/NIR observations
  59. GRB 250610B: SVOM/VT optical shallow decay
  60. GRB 250610B: additional Liverpool Telescope optical observations
  61. GRB 250610B: SVOM/GRM analysis
  62. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  63. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  64. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  65. GRB 250610B: Swift-XRT counterpart detection
  66. GRB 250610B: SVOM/VT optical counterpart
  67. GRB 250610B: LT detection of the optical counterpart
  68. GRB 250610B: OHP/T120 optical counterpart candidate
  69. GRB 250610C: Fermi GBM Final Real-time Localization
  70. GRB 250610B: GOTO optical upper limit
  71. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  72. GRB 250610B: SVOM detection of a long burst
  73. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  74. GRB 250610A: Fermi GBM Final Real-time Localization
  75. GRB 250605A: Swift-BAT refined analysis
  76. GRB 250609A: Fermi GBM Observation
  77. GRBAlpha reentry on June 9, 2025
  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. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  82. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  83. GRB 250527C: CrAO Optical Upper Limit
  84. GRB 250609A: Fermi GBM Final Real-time Localization
  85. GRB 250607A: SVOM/GRM observation of a long burst
  86. GRB 250607A: Fermi GBM Final Localization
  87. GRB 250605A: SVOM/VT optical upper limit
  88. GRB 250605A: Swift-XRT refined Analysis
  89. GRB 250605A: Enhanced Swift-XRT position
  90. Fermi GRB 250606A: Global MASTER-Net observations report
  91. GRB 250606A: Fermi GBM Final Real-time Localization
  92. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  93. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  94. GRB 250602A: GECAM detection
  95. Fermi trigger No 770867684: Global MASTER-Net observations report
  96. GRB 250605A: LT optical observations
  97. GRB 250605A: Swift detection of a burst
  98. Konus-Wind detection of GRB 250601A
  99. IPN triangulation of GRB 250404B
  100. IPN triangulation of GRB 250529A

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