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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"

12054 results found.

  1. GRB 250625A: NOT z-band upper limit
  2. Fermi GRB 250625A: Global MASTER-Net observations report
  3. GRB 250625A: Swift detection of a burst
  4. Fermi GRB 250624A: Global MASTER-Net observations report
  5. Fermi GRB 250623A: Global MASTER-Net observations report
  6. Fermi trigger No 772190032: Global MASTER-Net observations report
  7. Fermi GRB 250621A: Global MASTER-Net observations report
  8. Fermi trigger No 772128434: Global MASTER-Net observations report
  9. Fermi trigger No 772058337: Global MASTER-Net observations report
  10. GRB 250615A: Kilonova-Catcher optical upper limits
  11. Fermi GRB 250617A: Global MASTER-Net observations report
  12. GRB 250615A/EP250615a: FTW optical and NIR observations
  13. GRB 250617B: Swift/UVOT Detection
  14. GRB 250617B: NUTTelA-TAO early time optical observations
  15. Fermi trigger No 771886893: Global MASTER-Net observations report
  16. Swift GRB 250617B: Global MASTER-Net observations report
  17. GRB 250617B: GOTO optical upper limit
  18. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  19. EP#01709178975: Swift-XRT counterpart detection
  20. EP-WXT trigger 01709178975: GOTO optical upper limit
  21. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  22. GRB 250615A: COLIBRÍ optical upper limit
  23. GRB 250615A: DDOTI Optical Upper Limit
  24. GRB 250615A: Swift/UVOT Upper Limits
  25. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  26. sb25061207/SVOM: T120 OHP optical upper limit
  27. Fermi trigger No 771752663: Global MASTER-Net observations report
  28. Swift GRB 250615A: Global MASTER-Net observations report
  29. Fermi trigger No 771718064: Global MASTER-Net observations report
  30. sb25061207: Mephisto optical upper limits
  31. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  32. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  33. Fermi trigger No 771494087: Global MASTER-Net observations report
  34. sb25061218: Swift-XRT observations
  35. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  36. Fermi trigger No 771424081: Global MASTER-Net observations report
  37. EP250612a: Global MASTER-Net observations report
  38. sb25061207: Swift-XRT observations
  39. EP250612a/GRB 250612B: JinShan optical upper limit
  40. EP250610a: Upper limit from Fermi-GBM Observations
  41. Swift GRB250612.04: Global MASTER-Net observations report
  42. GRB 250610B: Swift/UVOT Detection
  43. EP250610A: Swift/UVOT Upper limits
  44. EP250610a: TNG NIR upper limit
  45. EP250610a: Liverpool Telescope optical upper limits
  46. GRB 250610B: Swift-XRT counterpart detection
  47. GRB 250610B: GOTO optical upper limit
  48. EP250610a: Global MASTER-Net observations report
  49. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  50. EP250610a: SVOM/VT optical upper limit
  51. EP250610a: Swift-XRT counterpart detection
  52. EP250610a: COLIBRÍ optical upper limit
  53. Fermi trigger No 771072240: Global MASTER-Net observations report
  54. GRB 250605A: Swift/UVOT Upper Limits
  55. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  56. GRB 250527C: CrAO Optical Upper Limit
  57. GRB 250605A: SVOM/VT optical upper limit
  58. Fermi GRB 250606A: Global MASTER-Net observations report
  59. Fermi trigger No 770867684: Global MASTER-Net observations report
  60. GRB 250605A: LT optical observations
  61. GRB 250605A: Swift detection of a burst
  62. Swift GRB250605.79: Global MASTER-Net observations report
  63. GRB 250601A: PRIME H band upper limit.
  64. GRB 250601A: PRIME J band upper limit.
  65. GRB 250603A: Swift/UVOT Upper Limits
  66. Fermi trigger No 770638414: Global MASTER-Net observations report
  67. Swift GRB250603.05: Global MASTER-Net observations report
  68. GRB 250602A: DDOTI Optical Upper Limit
  69. GRB 250601A: Swift/XRT candidate afterglow
  70. GRB 250601A: Swift-XRT observations
  71. Fermi GRB 250601A: Global MASTER-Net observations report
  72. Fermi trigger No 770470765: Global MASTER-Net observations report
  73. Fermi GRB 250531A: Global MASTER-Net observations report
  74. EP#01709177494: Swift-XRT counterpart detection of known source
  75. GRB 250530C: BOOTES-7 optical upper limit
  76. Swift GRB 250530C: Global MASTER-Net observations report
  77. GRB 250530C: Swift detection of a burst
  78. GRB 250530A: SVOM/VT optical upper limit
  79. GRB 250530A: Swift-XRT counterpart detection
  80. GRB 250527C: Swift/UVOT Upper Limits
  81. GRB 250527B: Swift-XRT observations
  82. EP250526a: SVOM/VT optical upper limit
  83. Fermi trigger No 770058372: Global MASTER-Net observations report
  84. Fermi trigger No 770047117: Global MASTER-Net observations report
  85. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  86. GRB 250314A: CIDER NB1008 upper limit
  87. EP250526a: COLIBRÍ optical upper limits
  88. EP250526a: Global MASTER-Net observations report
  89. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  90. Fermi GRB 250523A: Global MASTER-Net observations report
  91. Fermi trigger No 769611916: Global MASTER-Net observations report
  92. GRB 250521B: SVOM/VT optical upper limit
  93. Fermi GRB 250522B: Global MASTER-Net observations report
  94. EP#01709176612: Swift-XRT counterpart detection of flaring star
  95. Fermi GRB 250521D: Global MASTER-Net observations report
  96. Fermi trigger No 769533898: Global MASTER-Net observations report
  97. Fermi trigger No 769499303: Global MASTER-Net observations report
  98. GRB 250521D: DDOTI Optical Upper Limit
  99. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. GRB 250521A: DDOTI Optical Upper Limit

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