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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"

19595 results found.

  1. sb25061207: Swift-XRT observations
  2. GRB 250610B: Swift-XRT refined Analysis
  3. EP250610a: continuous follow-up observations with EP-FXT
  4. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  5. Swift GRB250612.04: Global MASTER-Net observations report
  6. GRB 250610B: Swift/UVOT Detection
  7. EP250610A: Swift/UVOT Upper limits
  8. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  9. GRB 250610B: Swift-XRT counterpart detection
  10. GRB 250610B: SVOM/VT optical counterpart
  11. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  12. GRB 250605A: Swift-BAT refined analysis
  13. EP250610a: SVOM/VT optical upper limit
  14. EP250610a: REM optical/NIR observations
  15. GRB 250609A: Fermi GBM Observation
  16. EP250610a: Swift-XRT counterpart detection
  17. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  18. GRB 250605A: Swift/UVOT Upper Limits
  19. GRB 250527C: CrAO Optical Upper Limit
  20. GRB 250605A: SVOM/VT optical upper limit
  21. GRB 250605A: Swift-XRT refined Analysis
  22. GRB 250605A: Enhanced Swift-XRT position
  23. GRB 250605A: LT optical observations
  24. GRB 250605A: Swift detection of a burst
  25. Swift GRB250605.79: Global MASTER-Net observations report
  26. Konus-Wind detection of GRB 250601A
  27. IPN triangulation of GRB 250404B
  28. IPN triangulation of GRB 250529A
  29. GRB 250601A: PRIME H band upper limit.
  30. GRB 250601A: PRIME J band upper limit.
  31. GRB 250601A: VLT/FORS2 Optical Observation
  32. GRB 250601A: Fermi GBM Observation
  33. GRB 250603A: Swift/UVOT Upper Limits
  34. GRB 250603A: Swift-XRT refined Analysis
  35. GRB 250603A: Enhanced Swift-XRT position
  36. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  37. Swift GRB250603.05: Global MASTER-Net observations report
  38. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  39. GRB 250530C: Swift-BAT refined analysis
  40. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  41. GRB 250601A: Swift/XRT candidate afterglow
  42. GRB 250601A: Swift-XRT observations
  43. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  44. GRB 250601A: Swift ToO observations
  45. EP#01709177494: SVOM/VT optical observations
  46. EP#01709177494: Swift-XRT counterpart detection of known source
  47. GRB 250530C: BOOTES-7 optical upper limit
  48. GRB 250530C: Swift-XRT refined Analysis
  49. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  50. Swift GRB 250530C: Global MASTER-Net observations report
  51. GRB 250530C: Enhanced Swift-XRT position
  52. GRB 250530C: Swift detection of a burst
  53. GRB 250530A: EP-FXT counterpart detection
  54. GRB 250530A: SVOM/VT optical upper limit
  55. GRB 250530A: Swift-XRT counterpart detection
  56. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  57. GRB 250527C: Swift/UVOT Upper Limits
  58. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  59. GRB 250527B: Swift-XRT observations
  60. GRB 250520A: Swift-BAT refined analysis
  61. GRB 250527C: Swift ToO observations
  62. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  63. GRB 250527B: Tiled Swift observations
  64. GRB 250520A: GRBAlpha detection
  65. GRB 250521B: SVOM/VT optical upper limit
  66. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  67. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  68. EP#01709176612: Swift-XRT counterpart detection of flaring star
  69. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  70. GRB 250521B: Swift ToO observations
  71. Konus-Wind detection of GRB 250520A (short/hard)
  72. GRB 250520A: Swift/UVOT Upper Limits
  73. IPN triangulation of GRB 250516B
  74. GRB 250520A: J-band observations with WINTER
  75. GRB 250520A: Swift-XRT refined Analysis
  76. GRB 250520A: REM optical/NIR early observations
  77. GRB 250520A:SVOM/VT optical candidate
  78. GRB 250520A: COLIBRÍ optical upper limit
  79. GRB 250520A: DDOTI Optical Upper Limit
  80. GRB 250520A: AstroSat CZTI detection of a short burst
  81. GRB 250520A: SVOM/GRM observation
  82. GRB 250520A: Enhanced Swift-XRT position
  83. GRB 250520A: GOTO optical upper limit
  84. GRB 250520A: Prompt enhanced Swift-XRT position
  85. GRB 250520A: Swift detection of a burst
  86. Swift GRB 250520A: Global MASTER-Net observations report
  87. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  88. GRB 250516A: Swift-BAT refined analysis
  89. Konus-Wind detection of GRB 250516A
  90. GRB 250515A: Swift-XRT observations
  91. Swift GRB 250516A: Global MASTER-Net observations report
  92. GRB 250516A: AstroSat CZTI detection
  93. GRB 250516A: Fermi GBM Observation
  94. GRB 250516A: Swift-XRT refined Analysis
  95. GRB 250516A: Swift/UVOT Detection
  96. GRB 250515A: Swift ToO observations
  97. GRB 250516A: Enhanced Swift-XRT position
  98. GRB 250516A: Swift detection of a burst
  99. GRB 250509A: Swift-BAT refined analysis
  100. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)

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