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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"

28040 results found.

  1. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  2. GRB 250602A: Fermi GBM Observation
  3. GRB 250602A: DDOTI Optical Upper Limit
  4. GRB 250530C: Swift-BAT refined analysis
  5. GRB 250601A: Swift/XRT candidate afterglow
  6. GRB 250601A: Swift-XRT observations
  7. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  8. GRB 250601A: Fermi GBM Final Real-time Localization
  9. EP#01709177494: SVOM/VT optical observations
  10. EP#01709177494: Swift-XRT counterpart detection of known source
  11. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  12. GRB 250530C: Swift-XRT refined Analysis
  13. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  14. GRB 250530C: Enhanced Swift-XRT position
  15. GRB 250530C: Swift detection of a burst
  16. GRB 250530A: EP-FXT counterpart detection
  17. GRB 250530A: SVOM/VT optical upper limit
  18. GRB 250530A: Swift-XRT counterpart detection
  19. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  20. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  21. GRB 250530A: SVOM detection of a burst
  22. GRB 250527C: Swift/UVOT Upper Limits
  23. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  24. GRB 250527B: Swift-XRT observations
  25. GRB 250520A: Swift-BAT refined analysis
  26. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  27. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  28. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  29. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  30. GRB 250314A: CIDER NB1008 upper limit
  31. EP250526a: COLIBRÍ optical upper limits
  32. EP250526a: Einstein Probe detection of a fast X-ray transient
  33. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  34. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  35. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  36. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  37. EP#01709176612: Swift-XRT counterpart detection of flaring star
  38. GRB 250521D: DDOTI Optical Upper Limit
  39. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB 250521D: LAST tentative optical counterpart candidate
  41. GRB 250521A: DDOTI Optical Upper Limit
  42. GRB 250520A: VLT/FORS2 Optical Observation
  43. GRB 250502A: Tautenburg observations
  44. GRB 250520A: Swift/UVOT Upper Limits
  45. IPN triangulation of GRB 250516B
  46. GRB 250520A: J-band observations with WINTER
  47. GRB 250520A: Gemini-South optical observations
  48. GRB 250520A: Swift-XRT refined Analysis
  49. GRB 250520A: REM optical/NIR early observations
  50. GRB 250520A:SVOM/VT optical candidate
  51. GRB 250520A: COLIBRÍ optical upper limit
  52. GRB 250520A: DDOTI Optical Upper Limit
  53. GRB 250520A: AstroSat CZTI detection of a short burst
  54. GRB 250520A: Enhanced Swift-XRT position
  55. GRB 250520A: Swift detection of a burst
  56. GRB 250516A: Swift-BAT refined analysis
  57. GRB 250516A: COLIBRÍ optical upper limit
  58. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  59. GRB 250515A: Swift-XRT observations
  60. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  61. GRB 250515A: 1.6m Mephisto optical detection
  62. GRB 250516A: Fermi GBM Observation
  63. GRB 250516A: Swift-XRT refined Analysis
  64. GRB 250516A: Swift/UVOT Detection
  65. GRB 250516B: GECAM-B detection of a bright long burst
  66. GRB 250516A: Enhanced Swift-XRT position
  67. GRB 250516A: Swift detection of a burst
  68. MAXI GRB250515.65: Global MASTER-Net observations report
  69. GRB 250424A: COLIBRÍ detection of the associated supernova
  70. GRB 250502A: TESS observations
  71. GRB 250509A: Swift-BAT refined analysis
  72. Fermi GRB 250512A: Global MASTER-Net observations report
  73. EP250512a/GRB 250512B: REM optical/NIR observations
  74. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  75. GRB 250507B: AstroSat CZTI detection
  76. EP250511a: Gemini optical counterpart observation
  77. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  78. EP250511a: Mephisto optical upper limits
  79. GRB 250512B: SVOM detection of a burst
  80. EP250512a: Einstein Probe detection of an X-ray transient
  81. EP250511a: REM optical/NIR observations
  82. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  83. EP250511a: COLIBRÍ optical counterpart candidate
  84. EP250511a: BOOTES-5 optical upper limit
  85. EP250511a: Einstein Probe detection of an X-ray transient
  86. EP250508a: Gemini NIR upper limits
  87. GRB 250510B: Fermi GBM Observation
  88. GRB 250510A: Swift-XRT observations
  89. GRB 250509A: Fermi GBM Observation
  90. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  91. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  92. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  93. GRB 250509A: Swift-XRT refined Analysis
  94. GRB 250510A: SVOM possible detection of a burst
  95. GRB 250507A: J-band observations with WINTER
  96. GRB 250509A: Enhanced Swift-XRT position
  97. GRB 250509A: Swift detection of a burst
  98. GRB 250506A: NOT optical upper limits
  99. EP250508a: Liverpool Telescope optical upper limits
  100. EP250508a: KAIT optical upper limit

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