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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"

32595 results found.

  1. GRB 250617B: SAO RAS optical observations
  2. GRB 250617B: Swift detection of a burst with an optical counterpart
  3. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  4. GRB 250617A: Fermi GBM Final Real-time Localization
  5. IPN triangulation of GRB 250612C (short/hard)
  6. Konus-Wind detection of GRB 250615A / EP250615a
  7. GRB 250615A / EP250615a: AstroSat CZTI detection
  8. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  9. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  10. GRB 250615A: COLIBRÍ optical upper limit
  11. GRB 250615A: DDOTI Optical Upper Limit
  12. GRB 250615A: Swift/UVOT Upper Limits
  13. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  14. GRB 250615A: Swift-XRT refined Analysis
  15. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  16. GRB 250615A: Enhanced Swift-XRT position
  17. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  18. GRB 250615A: Prompt enhanced Swift-XRT position
  19. GRB 250615A: Swift detection of a burst
  20. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  21. GRID detection of GRB 250612C
  22. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  23. GRB 250614A: Fermi GBM Final Real-time Localization
  24. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  25. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  26. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  27. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  28. GRB 250612B: Fermi GBM Observation
  29. GRB 250612C: Fermi GBM Observation
  30. EP250612a/GRB 250612B: JinShan optical upper limit
  31. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  32. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  33. GRB 250610B: Swift-XRT refined Analysis
  34. GRB 250612C: Fermi GBM Final Real-time Localization
  35. EP250610a: Upper limit from Fermi-GBM Observations
  36. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  37. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  38. GRB 250610B: Liverpool Telescope continued monitoring
  39. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  40. GRB 250610B - SVOM/ECLAIRs refined analysis
  41. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  42. Fermi GBM Sub-Threshold Detection of GRB 250610B
  43. GRB 250610B: Swift/UVOT Detection
  44. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  45. GRB 250610B: REM optical/NIR observations
  46. GRB 250610B: SVOM/VT optical shallow decay
  47. GRB 250610B: additional Liverpool Telescope optical observations
  48. GRB 250610B: SVOM/GRM analysis
  49. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  50. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  51. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  52. GRB 250610B: Swift-XRT counterpart detection
  53. GRB 250610B: SVOM/VT optical counterpart
  54. GRB 250610B: LT detection of the optical counterpart
  55. GRB 250610B: OHP/T120 optical counterpart candidate
  56. GRB 250610C: Fermi GBM Final Real-time Localization
  57. GRB 250610B: GOTO optical upper limit
  58. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  59. GRB 250610B: SVOM detection of a long burst
  60. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  61. GRB 250610A: Fermi GBM Final Real-time Localization
  62. GRB 250605A: Swift-BAT refined analysis
  63. GRB 250609A: Fermi GBM Observation
  64. GRBAlpha reentry on June 9, 2025
  65. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  66. GRB 250605A: Swift/UVOT Upper Limits
  67. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  68. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  69. GRB 250527C: CrAO Optical Upper Limit
  70. GRB 250609A: Fermi GBM Final Real-time Localization
  71. GRB 250607A: SVOM/GRM observation of a long burst
  72. GRB 250607A: Fermi GBM Final Localization
  73. GRB 250605A: SVOM/VT optical upper limit
  74. GRB 250605A: Swift-XRT refined Analysis
  75. GRB 250605A: Enhanced Swift-XRT position
  76. Fermi GRB 250606A: Global MASTER-Net observations report
  77. GRB 250606A: Fermi GBM Final Real-time Localization
  78. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  79. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  80. GRB 250602A: GECAM detection
  81. GRB 250605A: LT optical observations
  82. GRB 250605A: Swift detection of a burst
  83. Konus-Wind detection of GRB 250601A
  84. IPN triangulation of GRB 250404B
  85. IPN triangulation of GRB 250529A
  86. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  87. GRB 250601A: PRIME H band upper limit.
  88. GRB 250530A: SVOM/GRM analysis
  89. GRB 250601A: PRIME J band upper limit.
  90. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  91. GRB 250601A: VLT/FORS2 Optical Observation
  92. GRB 250601A: Fermi GBM Observation
  93. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  94. GRB 250603A: Swift/UVOT Upper Limits
  95. GRB 250603A: Swift-XRT refined Analysis
  96. GRB 250603A: Enhanced Swift-XRT position
  97. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  98. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  99. GRB 250602A: Fermi GBM Observation
  100. GRB 250602A: Fermi-LAT detection

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