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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"
  1. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  2. GRB 250314A: CIDER NB1008 upper limit
  3. EP250526a: COLIBRÍ optical upper limits
  4. EP250526a: Global MASTER-Net observations report
  5. EP250526a: Einstein Probe detection of a fast X-ray transient
  6. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  7. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  8. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  9. GRB 250520A: 3 GHz MeerKAT Detection
  10. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  11. Fermi GRB 250523A: Global MASTER-Net observations report
  12. Fermi trigger No 769611916: Global MASTER-Net observations report
  13. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  14. GRB 250521A: GRBAlpha detection
  15. GRB 250520A: GRBAlpha detection
  16. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  17. GRB 250523A: Fermi GBM Final Real-time Localization
  18. The EP-WXT trigger 01709176712 is likely a flaring star
  19. GRB 250521B: SVOM/VT optical upper limit
  20. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  21. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  22. Fermi GRB 250522B: Global MASTER-Net observations report
  23. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  24. GRB 250522B: Fermi GBM Final Localization
  25. GRB 250521D: SVOM/VT optical observations
  26. GRB 250522A: Fermi GBM Final Real-time Localization
  27. EP#01709176612: Swift-XRT counterpart detection of flaring star
  28. Fermi GRB 250521D: Global MASTER-Net observations report
  29. Fermi trigger No 769533898: Global MASTER-Net observations report
  30. Fermi trigger No 769499303: Global MASTER-Net observations report
  31. GRB 250521D: DDOTI Optical Upper Limit
  32. The EP-WXT trigger 01709176612 is likely a flaring star
  33. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  34. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  35. GRB 250521D: LAST tentative optical counterpart candidate
  36. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  37. GRB 250520A: 10 GHz VLA radio source
  38. GRB 250521B: Swift ToO observations
  39. GRB 250521D: Fermi GBM Final Real-time Localization
  40. GRB 250521C: Fermi GBM Final Localization
  41. GRB 250521A: DDOTI Optical Upper Limit
  42. GRB 250521B: SVOM detection of a burst through offline search
  43. Konus-Wind detection of GRB 250520A (short/hard)
  44. GRB 250520A: VLT/FORS2 Optical Observation
  45. GRB 250502A: Tautenburg observations
  46. GRB 250520A: Swift/UVOT Upper Limits
  47. GRB 250521A: Fermi GBM Final Real-time Localization
  48. Konus-Wind detection of GRB 250516B
  49. IPN triangulation of GRB 250516B
  50. GRB 250520A: J-band observations with WINTER
  51. GRB 250520A: Gemini-South optical observations
  52. GRB 250520A: Swift-XRT refined Analysis
  53. GRB 250520A: REM optical/NIR early observations
  54. GRB 250520B: Fermi GBM Final Real-time Localization
  55. GRB 250520A：SVOM/VT optical candidate
  56. GRB 250520A: COLIBRÍ optical upper limit
  57. GRB 250520A: DDOTI Optical Upper Limit
  58. GRB 250520A: AstroSat CZTI detection of a short burst
  59. GRB 250516B: GRBAlpha detection
  60. GRB 250520A: SVOM/GRM observation
  61. GRB 250520A: Enhanced Swift-XRT position
  62. GRB 250520A: GOTO optical upper limit
  63. GRB 250520A: Prompt enhanced Swift-XRT position
  64. GRB 250520A: Swift detection of a burst
  65. Swift GRB 250520A: Global MASTER-Net observations report
  66. GRB 250516B: Insight-HXMT detection
  67. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  68. GRB 250516A: Swift-BAT refined analysis
  69. GRB 250516A: COLIBRÍ optical upper limit
  70. Konus-Wind detection of GRB 250516A
  71. GRB 250516B: NuSTAR Detection of the Prompt Emission
  72. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  73. Fermi GRB 250516A: Global MASTER-Net observations report
  74. GRB 250515A: Swift-XRT observations
  75. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  76. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  77. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  78. Swift GRB 250516A: Global MASTER-Net observations report
  79. GRB 250515A: 1.6m Mephisto optical detection
  80. GRB 250516A: AstroSat CZTI detection
  81. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  82. GRB 250516A: Fermi GBM Observation
  83. GRB 250516A: Swift-XRT refined Analysis
  84. GRB 250516A: Swift/UVOT Detection
  85. GRB 250515A: Swift ToO observations
  86. GRB 250516B: GECAM-B detection of a bright long burst
  87. GRB 250516A: Enhanced Swift-XRT position
  88. GRB 250516A: Swift detection of a burst
  89. GRB 250516A: Fermi GBM Final Real-time Localization
  90. GRB 250512B / EP250512a: SVOM/GRM analysis
  91. GRB 250515A: GOTO candidate optical counterpart
  92. MAXI GRB250515.65: Global MASTER-Net observations report
  93. GRB 250515A: Fermi GBM Final Localization
  94. GRB 250424A: COLIBRÍ detection of the associated supernova
  95. Konus-Wind detection of GRB 250512B / EP250512a
  96. GRB 250502A: TESS observations
  97. Fermi trigger No 768922089: Global MASTER-Net observations report
  98. GRB 250511A: GECAM-A detection of a short burst
  99. GRB 250509A: Swift-BAT refined analysis
  100. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)

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