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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"

11105 results found.

  1. GRB 250625A: ABObservatory afterglow detection
  2. GRB 250625A: OHP/T193 optical detection
  3. GRB 250625A: COLIBRÍ optical observations
  4. GRB 250625A: Fermi-LAT detection
  5. GRB 250625A: JinShan optical observations
  6. GRB250625A: Fermi GBM Observation
  7. GRB 250625A: NOT z-band upper limit
  8. GRB 250625A: SVOM/VT optical confirmation
  9. GRB 250620B: Fermi GBM Observation
  10. GRB 250625A: SAO RAS possible optical afterglow
  11. Fermi GRB 250625A: Global MASTER-Net observations report
  12. GRB 250625A: Swift detection of a burst
  13. GRB 250625A: Fermi GBM Final Real-time Localization
  14. GRB 250617B: Mondy and SAO RAS optical observations on 2025-06-23, 2025-06-24
  15. GRB 250620A: AstroSat CZTI detection
  16. GRB 250620C: AstroSat CZTI detection
  17. Fermi GRB 250624A: Global MASTER-Net observations report
  18. GRB 250624A: Fermi GBM Final Real-time Localization
  19. Fermi GRB 250623A: Global MASTER-Net observations report
  20. GRB 250623A: Fermi GBM Final Real-time Localization
  21. GRB 250521A: VZLUSAT-2 detection
  22. Fermi trigger No 772190032: Global MASTER-Net observations report
  23. Konus-Wind detection of GRB 250620C
  24. IPN triangulation of GRB 250620C (long/bright)
  25. GRB 250621B: SVOM/GRM detection of a possible magnetar X-ray burst
  26. GRB 250620C: SVOM/GRM observation
  27. GRB 250620A: SVOM/GRM observation of a short burst
  28. GRB250620A: Fermi GBM Observation
  29. Fermi GRB 250621A: Global MASTER-Net observations report
  30. GRB 250619B: Fermi GBM Observation
  31. GRB 250621A: Fermi GBM Final Real-time Localization
  32. GRB 250620B: Swift/BAT-GUANO localization skymap of a burst
  33. GRB250620C: Fermi GBM Observation
  34. GRB 250506A - SVOM/ECLAIRs Refined analysis
  35. GRB 250620A: Swift/BAT-GUANO subthreshold detection of a possibly short burst
  36. GRB 250619B: Swift/BAT-GUANO localization skymap of a burst
  37. GRB 250620C: Fermi GBM Final Real-time Localization
  38. Fermi trigger No 772128434: Global MASTER-Net observations report
  39. GRB 250620B: Fermi GBM Final Real-time Localization
  40. GRB 250620A: Fermi GBM Final Real-time Localization
  41. GRB 250617B: Nickel telescope optical observations
  42. GRB 250619B: Fermi GBM Final Real-time Localization
  43. Fermi trigger No 772058337: Global MASTER-Net observations report
  44. Fermi Gamma-ray Burst Monitor trigger 772058337/250619860 is not a GRB
  45. GRB 250619A: Fermi GBM Final Real-time Localization
  46. GRB 250617B: Assy AZT-20 Optical Observations
  47. Fermi GRB 250617A: Global MASTER-Net observations report
  48. GRB 250617B: VLT/X-shooter spectroscopic redshift z = 1.396
  49. GRB 250617B: COLIBRÍ optical observations
  50. GRB 250617B: NOT NIR observations of the afterglow
  51. GRB 250617B: SVOM/VT optical observation
  52. Fermi trigger No 771886893: Global MASTER-Net observations report
  53. GRB 250617B: GOTO optical upper limit
  54. GRB 250617B: Fermi GBM Observation
  55. GRB 250617B: Fermi GBM Final Localization
  56. GRB 250617A: Fermi GBM Final Real-time Localization
  57. IPN triangulation of GRB 250612C (short/hard)
  58. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  59. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  60. Fermi trigger No 771752663: Global MASTER-Net observations report
  61. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  62. Fermi trigger No 771718064: Global MASTER-Net observations report
  63. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  64. GRID detection of GRB 250612C
  65. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  66. GRB 250614A: Fermi GBM Final Real-time Localization
  67. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  68. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  69. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  70. Fermi trigger No 771494087: Global MASTER-Net observations report
  71. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  72. GRB 250612B: Fermi GBM Observation
  73. Fermi trigger No 771424081: Global MASTER-Net observations report
  74. GRB 250612C: Fermi GBM Observation
  75. EP250612a/GRB 250612B: JinShan optical upper limit
  76. EP 250612a: AST3-3 Yaoan Optical Observation
  77. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  78. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  79. GRB 250612C: Fermi GBM Final Real-time Localization
  80. EP250610a: Upper limit from Fermi-GBM Observations
  81. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  82. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  83. Fermi GBM Sub-Threshold Detection of GRB 250610B
  84. GRB 250610B: SVOM/GRM analysis
  85. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  86. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  87. GRB 250610C: Fermi GBM Final Real-time Localization
  88. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  89. GRB 250610A: Fermi GBM Final Real-time Localization
  90. GRB 250609A: Fermi GBM Observation
  91. Fermi trigger No 771072240: Global MASTER-Net observations report
  92. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  93. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  94. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  95. GRB 250527C: CrAO Optical Upper Limit
  96. GRB 250609A: Fermi GBM Final Real-time Localization
  97. GRB 250607A: SVOM/GRM observation of a long burst
  98. GRB 250607A: Fermi GBM Final Localization
  99. Fermi GRB 250606A: Global MASTER-Net observations report
  100. GRB 250606A: Fermi GBM Final Real-time Localization

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