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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. EP 250612a: AST3-3 Yaoan Optical Observation
  2. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  3. sb25061207: SVOM/VT optical counterpart
  4. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  5. GRB 250610B: Swift-XRT refined Analysis
  6. GRB 250612C: Fermi GBM Final Real-time Localization
  7. EP250610a: Upper limit from Fermi-GBM Observations
  8. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  9. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  10. EP250612a: Einstein Probe detection of an X-ray transient
  11. GRB 250610B: Liverpool Telescope continued monitoring
  12. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  13. sb25061207: SVOM detection of a X-ray transient
  14. EP250610a: continuous follow-up observations with EP-FXT
  15. GRB 250610B - SVOM/ECLAIRs refined analysis
  16. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  17. Swift GRB250612.04: Global MASTER-Net observations report
  18. Fermi GBM Sub-Threshold Detection of GRB 250610B
  19. GRB 250610B: Swift/UVOT Detection
  20. EP250610A: Swift/UVOT Upper limits
  21. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  22. EP250610a: TNG NIR upper limit
  23. GRB 250610B: REM optical/NIR observations
  24. EP250610a: Liverpool Telescope optical upper limits
  25. GRB 250610B: SVOM/VT optical shallow decay
  26. GRB 250610B: additional Liverpool Telescope optical observations
  27. GRB 250610B: SVOM/GRM analysis
  28. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  29. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  30. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  31. GRB 250610B: Swift-XRT counterpart detection
  32. GRB 250610B: SVOM/VT optical counterpart
  33. GRB 250610B: LT detection of the optical counterpart
  34. GRB 250610B: OHP/T120 optical counterpart candidate
  35. GRB 250610C: Fermi GBM Final Real-time Localization
  36. GRB 250610B: GOTO optical upper limit
  37. EP250610a: Global MASTER-Net observations report
  38. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  39. GRB 250610B: SVOM detection of a long burst
  40. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  41. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 250610A: Fermi GBM Final Real-time Localization
  43. GRB 250605A: Swift-BAT refined analysis
  44. EP250610a: SVOM/VT optical upper limit
  45. EP250610a: REM optical/NIR observations
  46. GRB 250609A: Fermi GBM Observation
  47. GRBAlpha reentry on June 9, 2025
  48. EP250610a: Swift-XRT counterpart detection
  49. EP250610a: COLIBRÍ optical upper limit
  50. EP250610a: Einstein Probe detection of an X-ray transient
  51. Fermi trigger No 771072240: Global MASTER-Net observations report
  52. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  53. GRB 250605A: Swift/UVOT Upper Limits
  54. The EP-WXT trigger 01709178283 is likely a flaring star
  55. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  56. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  57. GRB 250527C: CrAO Optical Upper Limit
  58. GRB 250609A: Fermi GBM Final Real-time Localization
  59. GRB 250607A: SVOM/GRM observation of a long burst
  60. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  61. The EP-WXT trigger 01709178244 is likely a flaring star
  62. GRB 250607A: Fermi GBM Final Localization
  63. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  64. The EP-WXT trigger 01709178069 is likely a flaring star
  65. GRB 250605A: SVOM/VT optical upper limit
  66. GRB 250605A: Swift-XRT refined Analysis
  67. EP/WXT 01709177873: GOTO observations confirm stellar variability
  68. GRB 250605A: Enhanced Swift-XRT position
  69. Fermi GRB 250606A: Global MASTER-Net observations report
  70. GRB 250606A: Fermi GBM Final Real-time Localization
  71. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  72. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  73. GRB 250602A: GECAM detection
  74. Fermi trigger No 770867684: Global MASTER-Net observations report
  75. The EP-WXT trigger 01709177873 is likely a flaring star
  76. GRB 250605A: LT optical observations
  77. GRB 250605A: Swift detection of a burst
  78. Swift GRB250605.79: Global MASTER-Net observations report
  79. Konus-Wind detection of GRB 250601A
  80. IPN triangulation of GRB 250404B
  81. IPN triangulation of GRB 250529A
  82. The EP-WXT trigger 01709177837 is likely a flaring star
  83. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  84. GRB 250601A: PRIME H band upper limit.
  85. GRB 250530A: SVOM/GRM analysis
  86. GRB 250601A: PRIME J band upper limit.
  87. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  88. GRB 250601A: VLT/FORS2 Optical Observation
  89. GRB 250601A: Fermi GBM Observation
  90. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  91. GRB 250603A: Swift/UVOT Upper Limits
  92. GRB 250603A: Swift-XRT refined Analysis
  93. Fermi trigger No 770638414: Global MASTER-Net observations report
  94. GRB 250603A: Enhanced Swift-XRT position
  95. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  96. Swift GRB250603.05: Global MASTER-Net observations report
  97. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  98. GRB 250602A: Fermi GBM Observation
  99. GRB 250602A: Fermi-LAT detection
  100. GRB 250602A: DDOTI Optical Upper Limit

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