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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"

26238 results found.

  1. GRB 250520A: Swift-BAT refined analysis
  2. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  3. EP250526a: SVOM/VT optical upper limit
  4. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  5. Fermi trigger No 770058372: Global MASTER-Net observations report
  6. Fermi trigger No 770047117: Global MASTER-Net observations report
  7. GRB 250527A: Fermi GBM Final Localization
  8. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  9. EP250526a: COLIBRÍ optical upper limits
  10. EP250526a: Global MASTER-Net observations report
  11. EP250526a: Einstein Probe detection of a fast X-ray transient
  12. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  13. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  14. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  15. Fermi GRB 250523A: Global MASTER-Net observations report
  16. Fermi trigger No 769611916: Global MASTER-Net observations report
  17. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  18. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  19. GRB 250523A: Fermi GBM Final Real-time Localization
  20. The EP-WXT trigger 01709176712 is likely a flaring star
  21. GRB 250521B: SVOM/VT optical upper limit
  22. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  23. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  24. Fermi GRB 250522B: Global MASTER-Net observations report
  25. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  26. GRB 250522B: Fermi GBM Final Localization
  27. GRB 250521D: SVOM/VT optical observations
  28. GRB 250522A: Fermi GBM Final Real-time Localization
  29. EP#01709176612: Swift-XRT counterpart detection of flaring star
  30. Fermi GRB 250521D: Global MASTER-Net observations report
  31. Fermi trigger No 769533898: Global MASTER-Net observations report
  32. Fermi trigger No 769499303: Global MASTER-Net observations report
  33. GRB 250521D: DDOTI Optical Upper Limit
  34. The EP-WXT trigger 01709176612 is likely a flaring star
  35. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  36. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. GRB 250521D: LAST tentative optical counterpart candidate
  38. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  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. GRB 250520A: VLT/FORS2 Optical Observation
  44. GRB 250502A: Tautenburg observations
  45. GRB 250520A: Swift/UVOT Upper Limits
  46. GRB 250521A: Fermi GBM Final Real-time Localization
  47. GRB 250520A: Swift-XRT refined Analysis
  48. GRB 250520A: REM optical/NIR early observations
  49. GRB 250520B: Fermi GBM Final Real-time Localization
  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 250516B: GRBAlpha detection
  55. GRB 250520A: SVOM/GRM observation
  56. GRB 250520A: GOTO optical upper limit
  57. GRB 250520A: Swift detection of a burst
  58. Swift GRB 250520A: Global MASTER-Net observations report
  59. GRB 250516A: Swift-BAT refined analysis
  60. GRB 250516A: COLIBRÍ optical upper limit
  61. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  62. Fermi GRB 250516A: Global MASTER-Net observations report
  63. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  64. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  65. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  66. Swift GRB 250516A: Global MASTER-Net observations report
  67. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  68. GRB 250516A: Fermi GBM Observation
  69. GRB 250516A: Swift-XRT refined Analysis
  70. GRB 250516A: Swift/UVOT Detection
  71. GRB 250516B: GECAM-B detection of a bright long burst
  72. GRB 250516A: Swift detection of a burst
  73. GRB 250516A: Fermi GBM Final Real-time Localization
  74. GRB 250512B / EP250512a: SVOM/GRM analysis
  75. GRB 250515A: GOTO candidate optical counterpart
  76. MAXI GRB250515.65: Global MASTER-Net observations report
  77. GRB 250515A: Fermi GBM Final Localization
  78. GRB 250424A: COLIBRÍ detection of the associated supernova
  79. GRB 250502A: TESS observations
  80. Fermi trigger No 768922089: Global MASTER-Net observations report
  81. GRB 250511A: GECAM-A detection of a short burst
  82. GRB 250509A: Swift-BAT refined analysis
  83. Fermi GRB 250512A: Global MASTER-Net observations report
  84. EP250512a/GRB 250512B: REM optical/NIR observations
  85. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  86. EP250511a: Gemini optical counterpart observation
  87. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  88. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  89. EP250512a: Global MASTER-Net observations report
  90. EP250511a: FTW optical and NIR observations
  91. GRB 250512B/EP250512a: SVOM/VT optical fading
  92. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  93. EP250511a: Mephisto optical upper limits
  94. GRB 250507B: GRBAlpha detection
  95. GRB 250512B: SVOM detection of a burst
  96. GRB 250507B: SVOM/GRM observation of a burst
  97. EP250512a: Einstein Probe detection of an X-ray transient
  98. GRB 250512A: Fermi GBM Final Real-time Localization
  99. EP250511a: REM optical/NIR observations
  100. EP250511a: Einstein Probe follow-up obsevation and refined analysis

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