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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"

32796 results found.

  1. GRB 250621A: Fermi GBM Final Real-time Localization
  2. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  3. GRB250620C: Fermi GBM Observation
  4. GRB 250506A - SVOM/ECLAIRs Refined analysis
  5. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  6. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  7. GRB 250620C: Fermi GBM Final Real-time Localization
  8. GRB 250620B: Fermi GBM Final Real-time Localization
  9. GRB 250620A: Fermi GBM Final Real-time Localization
  10. GRB 250617B: Nickel telescope optical observations
  11. GRB 250619B: Fermi GBM Final Real-time Localization
  12. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  13. GRB 250615A: Kilonova-Catcher optical upper limits
  14. GRB 250619A: Fermi GBM Final Real-time Localization
  15. GRB 250617B: Assy AZT-20 Optical Observations
  16. GRB 250612A / Swift J1643.6−3854: Swift-BAT refined analysis
  17. Fermi GRB 250617A: Global MASTER-Net observations report
  18. GRB 250615A/EP250615a: FTW optical and NIR observations
  19. sb25061218/SVOM: OHP/T120 and OHP/T193 optical imaging and spectroscopic observations
  20. GRB 250617B: Swift/UVOT Detection
  21. GRB 250617B: Kilonova-Catcher optical afterglow detection
  22. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  23. GRB 250617B: COLIBRÍ optical observations
  24. GRB 250617B: NOT NIR observations of the afterglow
  25. GRB 250617B: Swift-XRT refined Analysis
  26. GRB 250617B: SVOM/VT optical observation
  27. GRB 250617B: NUTTelA-TAO early time optical observations
  28. Swift GRB 250617B: Global MASTER-Net observations report
  29. GRB 250617B: GOTO optical upper limit
  30. GRB 250617B: Enhanced Swift-XRT position
  31. GRB 250617B: Fermi GBM Observation
  32. GRB 250615A: Swift-BAT refined analysis
  33. GRB 250617B: Fermi GBM Final Localization
  34. GRB 250617B: Ondrejov D50 optical afterglow detection
  35. GRB 250617B: SAO RAS optical observations
  36. GRB 250617B: Swift detection of a burst with an optical counterpart
  37. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  38. GRB 250617A: Fermi GBM Final Real-time Localization
  39. IPN triangulation of GRB 250612C (short/hard)
  40. Konus-Wind detection of GRB 250615A / EP250615a
  41. GRB 250615A / EP250615a: AstroSat CZTI detection
  42. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  43. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  44. GRB 250615A: COLIBRÍ optical upper limit
  45. GRB 250615A: DDOTI Optical Upper Limit
  46. GRB 250615A: Swift/UVOT Upper Limits
  47. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  48. GRB 250615A: Swift-XRT refined Analysis
  49. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  50. GRB 250615A: Enhanced Swift-XRT position
  51. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  52. GRB 250615A: Prompt enhanced Swift-XRT position
  53. GRB 250615A: Swift detection of a burst
  54. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  55. GRID detection of GRB 250612C
  56. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  57. GRB 250614A: Fermi GBM Final Real-time Localization
  58. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  59. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  60. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  61. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  62. GRB 250612B: Fermi GBM Observation
  63. GRB 250612C: Fermi GBM Observation
  64. EP250612a/GRB 250612B: JinShan optical upper limit
  65. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  66. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  67. GRB 250610B: Swift-XRT refined Analysis
  68. GRB 250612C: Fermi GBM Final Real-time Localization
  69. EP250610a: Upper limit from Fermi-GBM Observations
  70. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  71. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  72. GRB 250610B: Liverpool Telescope continued monitoring
  73. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  74. GRB 250610B - SVOM/ECLAIRs refined analysis
  75. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  76. Fermi GBM Sub-Threshold Detection of GRB 250610B
  77. GRB 250610B: Swift/UVOT Detection
  78. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  79. GRB 250610B: REM optical/NIR observations
  80. GRB 250610B: SVOM/VT optical shallow decay
  81. GRB 250610B: additional Liverpool Telescope optical observations
  82. GRB 250610B: SVOM/GRM analysis
  83. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  84. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  85. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  86. GRB 250610B: Swift-XRT counterpart detection
  87. GRB 250610B: SVOM/VT optical counterpart
  88. GRB 250610B: LT detection of the optical counterpart
  89. GRB 250610B: OHP/T120 optical counterpart candidate
  90. GRB 250610C: Fermi GBM Final Real-time Localization
  91. GRB 250610B: GOTO optical upper limit
  92. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  93. GRB 250610B: SVOM detection of a long burst
  94. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  95. GRB 250610A: Fermi GBM Final Real-time Localization
  96. GRB 250605A: Swift-BAT refined analysis
  97. GRB 250609A: Fermi GBM Observation
  98. GRBAlpha reentry on June 9, 2025
  99. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  100. GRB 250605A: Swift/UVOT Upper Limits

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