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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

21937 results found.

  1. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  2. GRB 250527C: CrAO Optical Upper Limit
  3. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  4. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  5. GRB 250605A: SVOM/VT optical upper limit
  6. EP/WXT 01709177873: GOTO observations confirm stellar variability
  7. Fermi GRB 250606A: Global MASTER-Net observations report
  8. Fermi trigger No 770867684: Global MASTER-Net observations report
  9. GRB 250605A: LT optical observations
  10. Swift GRB250605.79: Global MASTER-Net observations report
  11. GRB 250601A: PRIME H band upper limit.
  12. GRB 250530A: SVOM/GRM analysis
  13. GRB 250601A: PRIME J band upper limit.
  14. GRB 250601A: VLT/FORS2 Optical Observation
  15. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  16. GRB 250603A: Swift/UVOT Upper Limits
  17. Fermi trigger No 770638414: Global MASTER-Net observations report
  18. Swift GRB250603.05: Global MASTER-Net observations report
  19. GRB 250602A: DDOTI Optical Upper Limit
  20. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  21. GRB 250601A: Swift/XRT candidate afterglow
  22. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  23. GRB 250601A: Swift-XRT observations
  24. Fermi GRB 250601A: Global MASTER-Net observations report
  25. Fermi trigger No 770470765: Global MASTER-Net observations report
  26. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  27. GRB 250601A: Swift ToO observations
  28. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  29. EP#01709177494: SVOM/VT optical observations
  30. Fermi GRB 250531A: Global MASTER-Net observations report
  31. EP#01709177494: Swift-XRT counterpart detection of known source
  32. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  33. Swift GRB 250530C: Global MASTER-Net observations report
  34. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  35. GRB 250530A: SVOM/VT optical upper limit
  36. GRB 250530A: Swift-XRT counterpart detection
  37. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  38. GRB 250527C: Swift/UVOT Upper Limits
  39. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  40. GRB 250527B: Swift-XRT observations
  41. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  42. GRB 250527C: Swift ToO observations
  43. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  44. EP250526a: SVOM/VT optical upper limit
  45. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  46. GRB 250527B: Tiled Swift observations
  47. GRB 250520A: Gemini-South optical afterglow detection
  48. Fermi trigger No 770058372: Global MASTER-Net observations report
  49. Fermi trigger No 770047117: Global MASTER-Net observations report
  50. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 250314A: CIDER NB1008 upper limit
  52. EP250526a: Global MASTER-Net observations report
  53. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  54. GRB 250520A: 3 GHz MeerKAT Detection
  55. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  56. Fermi GRB 250523A: Global MASTER-Net observations report
  57. Fermi trigger No 769611916: Global MASTER-Net observations report
  58. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  59. GRB 250521B: SVOM/VT optical upper limit
  60. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  61. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  62. Fermi GRB 250522B: Global MASTER-Net observations report
  63. GRB 250521D: SVOM/VT optical observations
  64. EP#01709176612: Swift-XRT counterpart detection of flaring star
  65. Fermi GRB 250521D: Global MASTER-Net observations report
  66. Fermi trigger No 769533898: Global MASTER-Net observations report
  67. Fermi trigger No 769499303: Global MASTER-Net observations report
  68. GRB 250521D: DDOTI Optical Upper Limit
  69. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  70. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 250521D: LAST tentative optical counterpart candidate
  72. GRB 250520A: 10 GHz VLA radio source
  73. GRB 250521B: Swift ToO observations
  74. GRB 250521A: DDOTI Optical Upper Limit
  75. GRB 250520A: VLT/FORS2 Optical Observation
  76. GRB 250502A: Tautenburg observations
  77. GRB 250520A: Swift/UVOT Upper Limits
  78. GRB 250520A: J-band observations with WINTER
  79. GRB 250520A: Gemini-South optical observations
  80. GRB 250520A: REM optical/NIR early observations
  81. GRB 250520A: COLIBRÍ optical upper limit
  82. GRB 250520A: DDOTI Optical Upper Limit
  83. GRB 250520A: GOTO optical upper limit
  84. Swift GRB 250520A: Global MASTER-Net observations report
  85. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  86. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  87. Fermi GRB 250516A: Global MASTER-Net observations report
  88. GRB 250515A: Swift-XRT observations
  89. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  90. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  91. Swift GRB 250516A: Global MASTER-Net observations report
  92. GRB 250515A: 1.6m Mephisto optical detection
  93. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  94. GRB 250516A: Swift/UVOT Detection
  95. GRB 250515A: Swift ToO observations
  96. GRB 250515A: GOTO candidate optical counterpart
  97. MAXI GRB250515.65: Global MASTER-Net observations report
  98. GRB 250424A: COLIBRÍ detection of the associated supernova
  99. GRB 250502A: TESS observations
  100. Fermi trigger No 768922089: Global MASTER-Net observations report

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