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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"

12320 results found.

  1. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  2. Fermi trigger No 771424081: Global MASTER-Net observations report
  3. EP250612a: Global MASTER-Net observations report
  4. sb25061207: Swift-XRT observations
  5. EP250612a/GRB 250612B: JinShan optical upper limit
  6. EP250610a: Upper limit from Fermi-GBM Observations
  7. Swift GRB250612.04: Global MASTER-Net observations report
  8. GRB 250610B: Swift/UVOT Detection
  9. EP250610A: Swift/UVOT Upper limits
  10. EP250610a: TNG NIR upper limit
  11. EP250610a: Liverpool Telescope optical upper limits
  12. GRB 250610B: Swift-XRT counterpart detection
  13. GRB 250610B: GOTO optical upper limit
  14. EP250610a: Global MASTER-Net observations report
  15. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  16. EP250610a: SVOM/VT optical upper limit
  17. EP250610a: Swift-XRT counterpart detection
  18. EP250610a: COLIBRÍ optical upper limit
  19. Fermi trigger No 771072240: Global MASTER-Net observations report
  20. GRB 250605A: Swift/UVOT Upper Limits
  21. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  22. GRB 250527C: CrAO Optical Upper Limit
  23. GRB 250605A: SVOM/VT optical upper limit
  24. Fermi GRB 250606A: Global MASTER-Net observations report
  25. Fermi trigger No 770867684: Global MASTER-Net observations report
  26. GRB 250605A: LT optical observations
  27. GRB 250605A: Swift detection of a burst
  28. Swift GRB250605.79: Global MASTER-Net observations report
  29. GRB 250601A: PRIME H band upper limit.
  30. GRB 250601A: PRIME J band upper limit.
  31. GRB 250603A: Swift/UVOT Upper Limits
  32. Fermi trigger No 770638414: Global MASTER-Net observations report
  33. Swift GRB250603.05: Global MASTER-Net observations report
  34. GRB 250602A: DDOTI Optical Upper Limit
  35. GRB 250601A: Swift/XRT candidate afterglow
  36. GRB 250601A: Swift-XRT observations
  37. Fermi GRB 250601A: Global MASTER-Net observations report
  38. Fermi trigger No 770470765: Global MASTER-Net observations report
  39. Fermi GRB 250531A: Global MASTER-Net observations report
  40. EP#01709177494: Swift-XRT counterpart detection of known source
  41. GRB 250530C: BOOTES-7 optical upper limit
  42. Swift GRB 250530C: Global MASTER-Net observations report
  43. GRB 250530C: Swift detection of a burst
  44. GRB 250530A: SVOM/VT optical upper limit
  45. GRB 250530A: Swift-XRT counterpart detection
  46. GRB 250527C: Swift/UVOT Upper Limits
  47. GRB 250527B: Swift-XRT observations
  48. EP250526a: SVOM/VT optical upper limit
  49. Fermi trigger No 770058372: Global MASTER-Net observations report
  50. Fermi trigger No 770047117: Global MASTER-Net observations report
  51. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  52. GRB 250314A: CIDER NB1008 upper limit
  53. EP250526a: COLIBRÍ optical upper limits
  54. EP250526a: Global MASTER-Net observations report
  55. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  56. Fermi GRB 250523A: Global MASTER-Net observations report
  57. Fermi trigger No 769611916: Global MASTER-Net observations report
  58. GRB 250521B: SVOM/VT optical upper limit
  59. Fermi GRB 250522B: Global MASTER-Net observations report
  60. EP#01709176612: Swift-XRT counterpart detection of flaring star
  61. Fermi GRB 250521D: Global MASTER-Net observations report
  62. Fermi trigger No 769533898: Global MASTER-Net observations report
  63. Fermi trigger No 769499303: Global MASTER-Net observations report
  64. GRB 250521D: DDOTI Optical Upper Limit
  65. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  66. GRB 250521A: DDOTI Optical Upper Limit
  67. GRB 250520A: Swift/UVOT Upper Limits
  68. GRB 250520A: J-band observations with WINTER
  69. GRB 250520A: Gemini-South optical observations
  70. GRB 250520A: COLIBRÍ optical upper limit
  71. GRB 250520A: DDOTI Optical Upper Limit
  72. GRB 250520A: GOTO optical upper limit
  73. GRB 250520A: Swift detection of a burst
  74. Swift GRB 250520A: Global MASTER-Net observations report
  75. GRB 250516A: COLIBRÍ optical upper limit
  76. Fermi GRB 250516A: Global MASTER-Net observations report
  77. GRB 250515A: Swift-XRT observations
  78. Swift GRB 250516A: Global MASTER-Net observations report
  79. GRB 250516A: Swift/UVOT Detection
  80. GRB 250515A: GOTO candidate optical counterpart
  81. MAXI GRB250515.65: Global MASTER-Net observations report
  82. Fermi trigger No 768922089: Global MASTER-Net observations report
  83. Fermi GRB 250512A: Global MASTER-Net observations report
  84. Konus-Wind detection of GRB 250506A
  85. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  86. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  87. EP250512a: Global MASTER-Net observations report
  88. EP250511a: FTW optical and NIR observations
  89. EP250511a: Mephisto optical upper limits
  90. EP250511a: Global MASTER-Net observations report
  91. EP250511a: BOOTES-5 optical upper limit
  92. EP250508a: Gemini NIR upper limits
  93. Fermi GRB 250510C: Global MASTER-Net observations report
  94. Fermi GRB 250510B: Global MASTER-Net observations report
  95. GRB 250510A: Swift-XRT observations
  96. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. GRB 250507A: J-band observations with WINTER
  98. Fermi GRB 250509A: Global MASTER-Net observations report
  99. Swift GRB 250509A: Global MASTER-Net observations report
  100. GRB 250506A: NOT optical upper limits

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