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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 250612C: Fermi GBM Final Real-time Localization
  2. EP250610a: Upper limit from Fermi-GBM Observations
  3. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  4. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  5. EP250612a: Einstein Probe detection of an X-ray transient
  6. GRB 250610B: Liverpool Telescope continued monitoring
  7. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  8. sb25061207: SVOM detection of a X-ray transient
  9. EP250610a: continuous follow-up observations with EP-FXT
  10. GRB 250610B - SVOM/ECLAIRs refined analysis
  11. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  12. Swift GRB250612.04: Global MASTER-Net observations report
  13. Fermi GBM Sub-Threshold Detection of GRB 250610B
  14. GRB 250610B: Swift/UVOT Detection
  15. EP250610A: Swift/UVOT Upper limits
  16. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  17. EP250610a: TNG NIR upper limit
  18. GRB 250610B: REM optical/NIR observations
  19. EP250610a: Liverpool Telescope optical upper limits
  20. GRB 250610B: SVOM/VT optical shallow decay
  21. GRB 250610B: additional Liverpool Telescope optical observations
  22. GRB 250610B: SVOM/GRM analysis
  23. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  24. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  25. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  26. GRB 250610B: Swift-XRT counterpart detection
  27. GRB 250610B: SVOM/VT optical counterpart
  28. GRB 250610B: LT detection of the optical counterpart
  29. GRB 250610B: OHP/T120 optical counterpart candidate
  30. GRB 250610C: Fermi GBM Final Real-time Localization
  31. GRB 250610B: GOTO optical upper limit
  32. EP250610a: Global MASTER-Net observations report
  33. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  34. GRB 250610B: SVOM detection of a long burst
  35. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  36. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 250610A: Fermi GBM Final Real-time Localization
  38. GRB 250605A: Swift-BAT refined analysis
  39. EP250610a: SVOM/VT optical upper limit
  40. EP250610a: REM optical/NIR observations
  41. GRB 250609A: Fermi GBM Observation
  42. GRBAlpha reentry on June 9, 2025
  43. EP250610a: Swift-XRT counterpart detection
  44. EP250610a: COLIBRÍ optical upper limit
  45. EP250610a: Einstein Probe detection of an X-ray transient
  46. Fermi trigger No 771072240: Global MASTER-Net observations report
  47. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  48. GRB 250605A: Swift/UVOT Upper Limits
  49. The EP-WXT trigger 01709178283 is likely a flaring star
  50. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  51. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  52. GRB 250527C: CrAO Optical Upper Limit
  53. GRB 250609A: Fermi GBM Final Real-time Localization
  54. GRB 250607A: SVOM/GRM observation of a long burst
  55. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  56. The EP-WXT trigger 01709178244 is likely a flaring star
  57. GRB 250607A: Fermi GBM Final Localization
  58. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  59. The EP-WXT trigger 01709178069 is likely a flaring star
  60. GRB 250605A: SVOM/VT optical upper limit
  61. GRB 250605A: Swift-XRT refined Analysis
  62. EP/WXT 01709177873: GOTO observations confirm stellar variability
  63. GRB 250605A: Enhanced Swift-XRT position
  64. Fermi GRB 250606A: Global MASTER-Net observations report
  65. GRB 250606A: Fermi GBM Final Real-time Localization
  66. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  67. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  68. GRB 250602A: GECAM detection
  69. Fermi trigger No 770867684: Global MASTER-Net observations report
  70. The EP-WXT trigger 01709177873 is likely a flaring star
  71. GRB 250605A: LT optical observations
  72. GRB 250605A: Swift detection of a burst
  73. Swift GRB250605.79: Global MASTER-Net observations report
  74. Konus-Wind detection of GRB 250601A
  75. IPN triangulation of GRB 250404B
  76. IPN triangulation of GRB 250529A
  77. The EP-WXT trigger 01709177837 is likely a flaring star
  78. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  79. GRB 250601A: PRIME H band upper limit.
  80. GRB 250530A: SVOM/GRM analysis
  81. GRB 250601A: PRIME J band upper limit.
  82. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  83. GRB 250601A: VLT/FORS2 Optical Observation
  84. GRB 250601A: Fermi GBM Observation
  85. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  86. GRB 250603A: Swift/UVOT Upper Limits
  87. GRB 250603A: Swift-XRT refined Analysis
  88. Fermi trigger No 770638414: Global MASTER-Net observations report
  89. GRB 250603A: Enhanced Swift-XRT position
  90. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  91. Swift GRB250603.05: Global MASTER-Net observations report
  92. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  93. GRB 250602A: Fermi GBM Observation
  94. GRB 250602A: Fermi-LAT detection
  95. GRB 250602A: DDOTI Optical Upper Limit
  96. GRB 250530C: Swift-BAT refined analysis
  97. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  98. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  99. GRB 250601A: Swift/XRT candidate afterglow
  100. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry

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