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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"

23153 results found.

  1. GRB 250527C: Swift/UVOT Upper Limits
  2. EP J1350.0-8622: EP-FXT follow-up observation
  3. GRB 250527B: Swift-XRT observations
  4. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  5. GRB 250520A: Swift-BAT refined analysis
  6. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  7. EP250526a: COLIBRÍ optical upper limits
  8. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  9. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  10. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  11. Fermi trigger No 769611916: Global MASTER-Net observations report
  12. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  13. GRB 250521A: GRBAlpha detection
  14. GRB 250520A: GRBAlpha detection
  15. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  16. EP#01709176612: Swift-XRT counterpart detection of flaring star
  17. GRB 250521D: DDOTI Optical Upper Limit
  18. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  19. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  20. GRB 250521D: LAST tentative optical counterpart candidate
  21. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  22. GRB 250521A: DDOTI Optical Upper Limit
  23. GRB 250521B: SVOM detection of a burst through offline search
  24. Konus-Wind detection of GRB 250520A (short/hard)
  25. GRB 250502A: Tautenburg observations
  26. Konus-Wind detection of GRB 250516B
  27. IPN triangulation of GRB 250516B
  28. GRB 250520A: J-band observations with WINTER
  29. GRB 250520A: Swift-XRT refined Analysis
  30. GRB 250520A: REM optical/NIR early observations
  31. GRB 250520A: COLIBRÍ optical upper limit
  32. GRB 250520A: DDOTI Optical Upper Limit
  33. GRB 250520A: AstroSat CZTI detection of a short burst
  34. GRB 250516B: GRBAlpha detection
  35. GRB 250520A: GOTO optical upper limit
  36. GRB 250520A: Swift detection of a burst
  37. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  38. GRB 250516A: Swift-BAT refined analysis
  39. GRB 250516A: COLIBRÍ optical upper limit
  40. Konus-Wind detection of GRB 250516A
  41. GRB 250515A: Swift-XRT observations
  42. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  43. GRB 250515A: 1.6m Mephisto optical detection
  44. GRB 250516A: AstroSat CZTI detection
  45. GRB 250516A: Swift-XRT refined Analysis
  46. GRB 250516A: Swift detection of a burst
  47. GRB 250512B / EP250512a: SVOM/GRM analysis
  48. GRB 250515A: GOTO candidate optical counterpart
  49. GRB 250424A: COLIBRÍ detection of the associated supernova
  50. Konus-Wind detection of GRB 250512B / EP250512a
  51. GRB 250509A: Swift-BAT refined analysis
  52. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  53. Konus-Wind detection of GRB 250506A
  54. EP250512a/GRB 250512B: REM optical/NIR observations
  55. GRB 250507B: AstroSat CZTI detection
  56. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  57. EP250511a: Mephisto optical upper limits
  58. GRB 250507B: GRBAlpha detection
  59. GRB 250506A: GRBAlpha detection
  60. EP250512a: Einstein Probe detection of an X-ray transient
  61. EP250511a: REM optical/NIR observations
  62. EP250511a: COLIBRÍ optical counterpart candidate
  63. EP250511a: BOOTES-5 optical upper limit
  64. GRB 250510A: Swift-XRT observations
  65. GRB 250509A: Fermi GBM Observation
  66. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  67. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  68. GRB 250509A: Swift-XRT refined Analysis
  69. GRB 250507A: J-band observations with WINTER
  70. Swift GRB 250509A: Global MASTER-Net observations report
  71. GRB 250509A: Swift detection of a burst
  72. GRB 250506A: NOT optical upper limits
  73. EP250508a: KAIT optical upper limit
  74. GRB 250507A: KAIT optical upper limit
  75. EP250508a: REM optical/NIR observations
  76. GRB 250506A: Swift-XRT afterglow detection
  77. EP250508a: COLIBRÍ Optical Limit
  78. GRB 250507A: Swift-XRT refined Analysis
  79. GRB 250427B : SVOM detection of a burst through offline search
  80. GRB 250507A: follow-up observation with EP-FXT
  81. GRB 250430A / EP250430a: AstroSat CZTI detection
  82. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  83. GRB 250507A: refined SVOM/MXT data analysis
  84. GRB 250507A: REM optical/NIR observations
  85. GRB 250506A: Swift-XRT observations
  86. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  88. GRB 250506A: Mephisto optical upper limits
  89. GRB 250430A: Konus-Wind detection and joint Konus-Wind+Swift-BAT spectral analysis
  90. GRB 250506A: Xinglong 2.16m optical upper limit
  91. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  92. GRB 250506A: REM optical/NIR upper limits
  93. GRB 250506A: TRT optical observations
  94. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) Upper Limits on the Optical Counterpart
  95. GRB 250504A: Swift-BAT refined analysis
  96. GRB 250430A: Swift-BAT refined analysis
  97. GRB 250506A: Fermi GBM Final Real-time Localization
  98. GRB 250504A: Swift-XRT refined Analysis
  99. GRB 250504A: VLT/X-shooter upper limits
  100. GRB 250504A: REM optical/NIR observations

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