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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"

45423 results found.

  1. EP250526a: SVOM/VT optical upper limit
  2. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  3. GRB 250527B: Tiled Swift observations
  4. GRB 250520A: Gemini-South optical afterglow detection
  5. Fermi trigger No 770058372: Global MASTER-Net observations report
  6. Fermi trigger No 770047117: Global MASTER-Net observations report
  7. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  8. GRB 250527A: Fermi GBM Final Localization
  9. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  10. GRB 250314A: CIDER NB1008 upper limit
  11. EP250526a: COLIBRÍ optical upper limits
  12. EP250526a: Global MASTER-Net observations report
  13. EP250526a: Einstein Probe detection of a fast X-ray transient
  14. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  15. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  16. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  17. GRB 250520A: 3 GHz MeerKAT Detection
  18. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  19. Fermi GRB 250523A: Global MASTER-Net observations report
  20. Fermi trigger No 769611916: Global MASTER-Net observations report
  21. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  22. GRB 250521A: GRBAlpha detection
  23. GRB 250520A: GRBAlpha detection
  24. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  25. GRB 250523A: Fermi GBM Final Real-time Localization
  26. The EP-WXT trigger 01709176712 is likely a flaring star
  27. GRB 250521B: SVOM/VT optical upper limit
  28. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  29. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  30. Fermi GRB 250522B: Global MASTER-Net observations report
  31. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  32. GRB 250522B: Fermi GBM Final Localization
  33. GRB 250521D: SVOM/VT optical observations
  34. GRB 250522A: Fermi GBM Final Real-time Localization
  35. EP#01709176612: Swift-XRT counterpart detection of flaring star
  36. Fermi GRB 250521D: Global MASTER-Net observations report
  37. Fermi trigger No 769533898: Global MASTER-Net observations report
  38. Fermi trigger No 769499303: Global MASTER-Net observations report
  39. GRB 250521D: DDOTI Optical Upper Limit
  40. The EP-WXT trigger 01709176612 is likely a flaring star
  41. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  42. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  43. GRB 250521D: LAST tentative optical counterpart candidate
  44. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  45. GRB 250520A: 10 GHz VLA radio source
  46. GRB 250521B: Swift ToO observations
  47. GRB 250521D: Fermi GBM Final Real-time Localization
  48. GRB 250521C: Fermi GBM Final Localization
  49. GRB 250521A: DDOTI Optical Upper Limit
  50. GRB 250521B: SVOM detection of a burst through offline search
  51. Konus-Wind detection of GRB 250520A (short/hard)
  52. GRB 250520A: VLT/FORS2 Optical Observation
  53. GRB 250502A: Tautenburg observations
  54. GRB 250520A: Swift/UVOT Upper Limits
  55. GRB 250521A: Fermi GBM Final Real-time Localization
  56. Konus-Wind detection of GRB 250516B
  57. IPN triangulation of GRB 250516B
  58. GRB 250520A: J-band observations with WINTER
  59. GRB 250520A: Gemini-South optical observations
  60. GRB 250520A: Swift-XRT refined Analysis
  61. GRB 250520A: REM optical/NIR early observations
  62. GRB 250520B: Fermi GBM Final Real-time Localization
  63. GRB 250520A：SVOM/VT optical candidate
  64. GRB 250520A: COLIBRÍ optical upper limit
  65. GRB 250520A: DDOTI Optical Upper Limit
  66. GRB 250520A: AstroSat CZTI detection of a short burst
  67. GRB 250516B: GRBAlpha detection
  68. GRB 250520A: SVOM/GRM observation
  69. GRB 250520A: Enhanced Swift-XRT position
  70. GRB 250520A: GOTO optical upper limit
  71. GRB 250520A: Prompt enhanced Swift-XRT position
  72. GRB 250520A: Swift detection of a burst
  73. Swift GRB 250520A: Global MASTER-Net observations report
  74. GRB 250516B: Insight-HXMT detection
  75. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  76. GRB 250516A: Swift-BAT refined analysis
  77. GRB 250516A: COLIBRÍ optical upper limit
  78. Konus-Wind detection of GRB 250516A
  79. GRB 250516B: NuSTAR Detection of the Prompt Emission
  80. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  81. Fermi GRB 250516A: Global MASTER-Net observations report
  82. GRB 250515A: Swift-XRT observations
  83. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  84. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  85. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  86. Swift GRB 250516A: Global MASTER-Net observations report
  87. GRB 250515A: 1.6m Mephisto optical detection
  88. GRB 250516A: AstroSat CZTI detection
  89. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  90. GRB 250516A: Fermi GBM Observation
  91. GRB 250516A: Swift-XRT refined Analysis
  92. GRB 250516A: Swift/UVOT Detection
  93. GRB 250515A: Swift ToO observations
  94. GRB 250516B: GECAM-B detection of a bright long burst
  95. GRB 250516A: Enhanced Swift-XRT position
  96. GRB 250516A: Swift detection of a burst
  97. GRB 250516A: Fermi GBM Final Real-time Localization
  98. GRB 250512B / EP250512a: SVOM/GRM analysis
  99. GRB 250515A: GOTO candidate optical counterpart
  100. MAXI GRB250515.65: Global MASTER-Net observations report

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