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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"

39057 results found.

  1. Swift GRB 250615A: Global MASTER-Net observations report
  2. Fermi trigger No 771718064: Global MASTER-Net observations report
  3. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  4. GRID detection of GRB 250612C
  5. sb25061207: Mephisto optical upper limits
  6. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  7. GRB 250614A: Fermi GBM Final Real-time Localization
  8. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  9. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  10. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  11. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  12. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. Fermi trigger No 771494087: Global MASTER-Net observations report
  14. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  15. GRB 250612B: Fermi GBM Observation
  16. Fermi trigger No 771424081: Global MASTER-Net observations report
  17. EP250612a: Global MASTER-Net observations report
  18. GRB 250612C: Fermi GBM Observation
  19. sb25061218: SVOM detection of a X-ray transient
  20. EP250612a/GRB 250612B: JinShan optical upper limit
  21. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  22. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  23. GRB 250610B: Swift-XRT refined Analysis
  24. GRB 250612C: Fermi GBM Final Real-time Localization
  25. EP250610a: Upper limit from Fermi-GBM Observations
  26. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  27. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  28. GRB 250610B: Liverpool Telescope continued monitoring
  29. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  30. sb25061207: SVOM detection of a X-ray transient
  31. GRB 250610B - SVOM/ECLAIRs refined analysis
  32. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  33. Swift GRB250612.04: Global MASTER-Net observations report
  34. Fermi GBM Sub-Threshold Detection of GRB 250610B
  35. GRB 250610B: Swift/UVOT Detection
  36. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  37. EP250610a: TNG NIR upper limit
  38. GRB 250610B: REM optical/NIR observations
  39. GRB 250610B: SVOM/VT optical shallow decay
  40. GRB 250610B: additional Liverpool Telescope optical observations
  41. GRB 250610B: SVOM/GRM analysis
  42. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  43. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  44. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  45. GRB 250610B: Swift-XRT counterpart detection
  46. GRB 250610B: SVOM/VT optical counterpart
  47. GRB 250610B: LT detection of the optical counterpart
  48. GRB 250610B: OHP/T120 optical counterpart candidate
  49. GRB 250610C: Fermi GBM Final Real-time Localization
  50. GRB 250610B: GOTO optical upper limit
  51. EP250610a: Global MASTER-Net observations report
  52. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  53. GRB 250610B: SVOM detection of a long burst
  54. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  55. GRB 250610A: Fermi GBM Final Real-time Localization
  56. GRB 250605A: Swift-BAT refined analysis
  57. EP250610a: REM optical/NIR observations
  58. GRB 250609A: Fermi GBM Observation
  59. GRBAlpha reentry on June 9, 2025
  60. EP250610a: COLIBRÍ optical upper limit
  61. Fermi trigger No 771072240: Global MASTER-Net observations report
  62. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  63. GRB 250605A: Swift/UVOT Upper Limits
  64. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  65. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  66. GRB 250527C: CrAO Optical Upper Limit
  67. GRB 250609A: Fermi GBM Final Real-time Localization
  68. GRB 250607A: SVOM/GRM observation of a long burst
  69. GRB 250607A: Fermi GBM Final Localization
  70. GRB 250605A: SVOM/VT optical upper limit
  71. GRB 250605A: Swift-XRT refined Analysis
  72. GRB 250605A: Enhanced Swift-XRT position
  73. Fermi GRB 250606A: Global MASTER-Net observations report
  74. GRB 250606A: Fermi GBM Final Real-time Localization
  75. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  76. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  77. GRB 250602A: GECAM detection
  78. Fermi trigger No 770867684: Global MASTER-Net observations report
  79. GRB 250605A: LT optical observations
  80. GRB 250605A: Swift detection of a burst
  81. Swift GRB250605.79: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 250601A
  83. IPN triangulation of GRB 250404B
  84. IPN triangulation of GRB 250529A
  85. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  86. GRB 250601A: PRIME H band upper limit.
  87. GRB 250530A: SVOM/GRM analysis
  88. GRB 250601A: PRIME J band upper limit.
  89. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  90. GRB 250601A: VLT/FORS2 Optical Observation
  91. GRB 250601A: Fermi GBM Observation
  92. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  93. GRB 250603A: Swift/UVOT Upper Limits
  94. GRB 250603A: Swift-XRT refined Analysis
  95. Fermi trigger No 770638414: Global MASTER-Net observations report
  96. GRB 250603A: Enhanced Swift-XRT position
  97. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  98. Swift GRB250603.05: Global MASTER-Net observations report
  99. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  100. GRB 250602A: Fermi GBM Observation

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