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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"

19589 results found.

  1. EP250610A: Swift/UVOT Upper limits
  2. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  3. GRB 250610B: Swift-XRT counterpart detection
  4. GRB 250610B: SVOM/VT optical counterpart
  5. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  6. GRB 250605A: Swift-BAT refined analysis
  7. EP250610a: SVOM/VT optical upper limit
  8. EP250610a: REM optical/NIR observations
  9. GRB 250609A: Fermi GBM Observation
  10. EP250610a: Swift-XRT counterpart detection
  11. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  12. GRB 250605A: Swift/UVOT Upper Limits
  13. GRB 250527C: CrAO Optical Upper Limit
  14. GRB 250605A: SVOM/VT optical upper limit
  15. GRB 250605A: Swift-XRT refined Analysis
  16. GRB 250605A: Enhanced Swift-XRT position
  17. GRB 250605A: LT optical observations
  18. GRB 250605A: Swift detection of a burst
  19. Swift GRB250605.79: Global MASTER-Net observations report
  20. Konus-Wind detection of GRB 250601A
  21. IPN triangulation of GRB 250404B
  22. IPN triangulation of GRB 250529A
  23. GRB 250601A: PRIME H band upper limit.
  24. GRB 250601A: PRIME J band upper limit.
  25. GRB 250601A: VLT/FORS2 Optical Observation
  26. GRB 250601A: Fermi GBM Observation
  27. GRB 250603A: Swift/UVOT Upper Limits
  28. GRB 250603A: Swift-XRT refined Analysis
  29. GRB 250603A: Enhanced Swift-XRT position
  30. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  31. Swift GRB250603.05: Global MASTER-Net observations report
  32. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  33. GRB 250530C: Swift-BAT refined analysis
  34. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  35. GRB 250601A: Swift/XRT candidate afterglow
  36. GRB 250601A: Swift-XRT observations
  37. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  38. GRB 250601A: Swift ToO observations
  39. EP#01709177494: SVOM/VT optical observations
  40. EP#01709177494: Swift-XRT counterpart detection of known source
  41. GRB 250530C: BOOTES-7 optical upper limit
  42. GRB 250530C: Swift-XRT refined Analysis
  43. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  44. Swift GRB 250530C: Global MASTER-Net observations report
  45. GRB 250530C: Enhanced Swift-XRT position
  46. GRB 250530C: Swift detection of a burst
  47. GRB 250530A: EP-FXT counterpart detection
  48. GRB 250530A: SVOM/VT optical upper limit
  49. GRB 250530A: Swift-XRT counterpart detection
  50. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  51. GRB 250527C: Swift/UVOT Upper Limits
  52. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  53. GRB 250527B: Swift-XRT observations
  54. GRB 250520A: Swift-BAT refined analysis
  55. GRB 250527C: Swift ToO observations
  56. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  57. GRB 250527B: Tiled Swift observations
  58. GRB 250520A: GRBAlpha detection
  59. GRB 250521B: SVOM/VT optical upper limit
  60. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  61. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  62. EP#01709176612: Swift-XRT counterpart detection of flaring star
  63. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  64. GRB 250521B: Swift ToO observations
  65. Konus-Wind detection of GRB 250520A (short/hard)
  66. GRB 250520A: Swift/UVOT Upper Limits
  67. IPN triangulation of GRB 250516B
  68. GRB 250520A: J-band observations with WINTER
  69. GRB 250520A: Swift-XRT refined Analysis
  70. GRB 250520A: REM optical/NIR early observations
  71. GRB 250520A:SVOM/VT optical candidate
  72. GRB 250520A: COLIBRÍ optical upper limit
  73. GRB 250520A: DDOTI Optical Upper Limit
  74. GRB 250520A: AstroSat CZTI detection of a short burst
  75. GRB 250520A: SVOM/GRM observation
  76. GRB 250520A: Enhanced Swift-XRT position
  77. GRB 250520A: GOTO optical upper limit
  78. GRB 250520A: Prompt enhanced Swift-XRT position
  79. GRB 250520A: Swift detection of a burst
  80. Swift GRB 250520A: Global MASTER-Net observations report
  81. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  82. GRB 250516A: Swift-BAT refined analysis
  83. Konus-Wind detection of GRB 250516A
  84. GRB 250515A: Swift-XRT observations
  85. Swift GRB 250516A: Global MASTER-Net observations report
  86. GRB 250516A: AstroSat CZTI detection
  87. GRB 250516A: Fermi GBM Observation
  88. GRB 250516A: Swift-XRT refined Analysis
  89. GRB 250516A: Swift/UVOT Detection
  90. GRB 250515A: Swift ToO observations
  91. GRB 250516A: Enhanced Swift-XRT position
  92. GRB 250516A: Swift detection of a burst
  93. GRB 250509A: Swift-BAT refined analysis
  94. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  95. GRB 250510B: Fermi GBM Observation
  96. GRB 250510A: Swift-XRT observations
  97. GRB 250509A: Fermi GBM Observation
  98. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  99. GRB 250509A: Swift-XRT refined Analysis
  100. GRB 250507A: J-band observations with WINTER

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Download all Circulars as a .tar.gz archive (updated once a day):
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