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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"

12318 results found.

  1. EP250612a: Global MASTER-Net observations report
  2. sb25061207: Swift-XRT observations
  3. EP250612a/GRB 250612B: JinShan optical upper limit
  4. EP250610a: Upper limit from Fermi-GBM Observations
  5. Swift GRB250612.04: Global MASTER-Net observations report
  6. GRB 250610B: Swift/UVOT Detection
  7. EP250610A: Swift/UVOT Upper limits
  8. EP250610a: TNG NIR upper limit
  9. EP250610a: Liverpool Telescope optical upper limits
  10. GRB 250610B: Swift-XRT counterpart detection
  11. GRB 250610B: GOTO optical upper limit
  12. EP250610a: Global MASTER-Net observations report
  13. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  14. EP250610a: SVOM/VT optical upper limit
  15. EP250610a: Swift-XRT counterpart detection
  16. EP250610a: COLIBRÍ optical upper limit
  17. Fermi trigger No 771072240: Global MASTER-Net observations report
  18. GRB 250605A: Swift/UVOT Upper Limits
  19. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  20. GRB 250527C: CrAO Optical Upper Limit
  21. GRB 250605A: SVOM/VT optical upper limit
  22. Fermi GRB 250606A: Global MASTER-Net observations report
  23. Fermi trigger No 770867684: Global MASTER-Net observations report
  24. GRB 250605A: LT optical observations
  25. GRB 250605A: Swift detection of a burst
  26. Swift GRB250605.79: Global MASTER-Net observations report
  27. GRB 250601A: PRIME H band upper limit.
  28. GRB 250601A: PRIME J band upper limit.
  29. GRB 250603A: Swift/UVOT Upper Limits
  30. Fermi trigger No 770638414: Global MASTER-Net observations report
  31. Swift GRB250603.05: Global MASTER-Net observations report
  32. GRB 250602A: DDOTI Optical Upper Limit
  33. GRB 250601A: Swift/XRT candidate afterglow
  34. GRB 250601A: Swift-XRT observations
  35. Fermi GRB 250601A: Global MASTER-Net observations report
  36. Fermi trigger No 770470765: Global MASTER-Net observations report
  37. Fermi GRB 250531A: Global MASTER-Net observations report
  38. EP#01709177494: Swift-XRT counterpart detection of known source
  39. GRB 250530C: BOOTES-7 optical upper limit
  40. Swift GRB 250530C: Global MASTER-Net observations report
  41. GRB 250530C: Swift detection of a burst
  42. GRB 250530A: SVOM/VT optical upper limit
  43. GRB 250530A: Swift-XRT counterpart detection
  44. GRB 250527C: Swift/UVOT Upper Limits
  45. GRB 250527B: Swift-XRT observations
  46. EP250526a: SVOM/VT optical upper limit
  47. Fermi trigger No 770058372: Global MASTER-Net observations report
  48. Fermi trigger No 770047117: Global MASTER-Net observations report
  49. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  50. GRB 250314A: CIDER NB1008 upper limit
  51. EP250526a: COLIBRÍ optical upper limits
  52. EP250526a: Global MASTER-Net observations report
  53. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  54. Fermi GRB 250523A: Global MASTER-Net observations report
  55. Fermi trigger No 769611916: Global MASTER-Net observations report
  56. GRB 250521B: SVOM/VT optical upper limit
  57. Fermi GRB 250522B: Global MASTER-Net observations report
  58. EP#01709176612: Swift-XRT counterpart detection of flaring star
  59. Fermi GRB 250521D: Global MASTER-Net observations report
  60. Fermi trigger No 769533898: Global MASTER-Net observations report
  61. Fermi trigger No 769499303: Global MASTER-Net observations report
  62. GRB 250521D: DDOTI Optical Upper Limit
  63. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 250521A: DDOTI Optical Upper Limit
  65. GRB 250520A: Swift/UVOT Upper Limits
  66. GRB 250520A: J-band observations with WINTER
  67. GRB 250520A: Gemini-South optical observations
  68. GRB 250520A: COLIBRÍ optical upper limit
  69. GRB 250520A: DDOTI Optical Upper Limit
  70. GRB 250520A: GOTO optical upper limit
  71. GRB 250520A: Swift detection of a burst
  72. Swift GRB 250520A: Global MASTER-Net observations report
  73. GRB 250516A: COLIBRÍ optical upper limit
  74. Fermi GRB 250516A: Global MASTER-Net observations report
  75. GRB 250515A: Swift-XRT observations
  76. Swift GRB 250516A: Global MASTER-Net observations report
  77. GRB 250516A: Swift/UVOT Detection
  78. GRB 250515A: GOTO candidate optical counterpart
  79. MAXI GRB250515.65: Global MASTER-Net observations report
  80. Fermi trigger No 768922089: Global MASTER-Net observations report
  81. Fermi GRB 250512A: Global MASTER-Net observations report
  82. Konus-Wind detection of GRB 250506A
  83. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  84. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  85. EP250512a: Global MASTER-Net observations report
  86. EP250511a: FTW optical and NIR observations
  87. EP250511a: Mephisto optical upper limits
  88. EP250511a: Global MASTER-Net observations report
  89. EP250511a: BOOTES-5 optical upper limit
  90. EP250508a: Gemini NIR upper limits
  91. Fermi GRB 250510C: Global MASTER-Net observations report
  92. Fermi GRB 250510B: Global MASTER-Net observations report
  93. GRB 250510A: Swift-XRT observations
  94. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 250507A: J-band observations with WINTER
  96. Fermi GRB 250509A: Global MASTER-Net observations report
  97. Swift GRB 250509A: Global MASTER-Net observations report
  98. GRB 250506A: NOT optical upper limits
  99. EP250508a: Liverpool Telescope optical upper limits
  100. EP250508a: KAIT optical upper limit

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Download all Circulars as a .tar.gz archive (updated once a day):
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