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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"

19603 results found.

  1. GRB 250615A: Swift-XRT refined Analysis
  2. GRB 250615A: Enhanced Swift-XRT position
  3. GRB 250615A: Prompt enhanced Swift-XRT position
  4. GRB 250615A: Swift detection of a burst
  5. Swift GRB 250615A: Global MASTER-Net observations report
  6. sb25061207: Mephisto optical upper limits
  7. sb25061218: Swift-XRT observations
  8. sb25061207: EP-FXT follow-up observation and afterglow candidate
  9. sb25061207: Swift-XRT observations
  10. GRB 250610B: Swift-XRT refined Analysis
  11. EP250610a: continuous follow-up observations with EP-FXT
  12. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  13. Swift GRB250612.04: Global MASTER-Net observations report
  14. GRB 250610B: Swift/UVOT Detection
  15. EP250610A: Swift/UVOT Upper limits
  16. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  17. GRB 250610B: Swift-XRT counterpart detection
  18. GRB 250610B: SVOM/VT optical counterpart
  19. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 250605A: Swift-BAT refined analysis
  21. EP250610a: SVOM/VT optical upper limit
  22. EP250610a: REM optical/NIR observations
  23. GRB 250609A: Fermi GBM Observation
  24. EP250610a: Swift-XRT counterpart detection
  25. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  26. GRB 250605A: Swift/UVOT Upper Limits
  27. GRB 250527C: CrAO Optical Upper Limit
  28. GRB 250605A: SVOM/VT optical upper limit
  29. GRB 250605A: Swift-XRT refined Analysis
  30. GRB 250605A: Enhanced Swift-XRT position
  31. GRB 250605A: LT optical observations
  32. GRB 250605A: Swift detection of a burst
  33. Swift GRB250605.79: Global MASTER-Net observations report
  34. Konus-Wind detection of GRB 250601A
  35. IPN triangulation of GRB 250404B
  36. IPN triangulation of GRB 250529A
  37. GRB 250601A: PRIME H band upper limit.
  38. GRB 250601A: PRIME J band upper limit.
  39. GRB 250601A: VLT/FORS2 Optical Observation
  40. GRB 250601A: Fermi GBM Observation
  41. GRB 250603A: Swift/UVOT Upper Limits
  42. GRB 250603A: Swift-XRT refined Analysis
  43. GRB 250603A: Enhanced Swift-XRT position
  44. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  45. Swift GRB250603.05: Global MASTER-Net observations report
  46. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  47. GRB 250530C: Swift-BAT refined analysis
  48. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  49. GRB 250601A: Swift/XRT candidate afterglow
  50. GRB 250601A: Swift-XRT observations
  51. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  52. GRB 250601A: Swift ToO observations
  53. EP#01709177494: SVOM/VT optical observations
  54. EP#01709177494: Swift-XRT counterpart detection of known source
  55. GRB 250530C: BOOTES-7 optical upper limit
  56. GRB 250530C: Swift-XRT refined Analysis
  57. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  58. Swift GRB 250530C: Global MASTER-Net observations report
  59. GRB 250530C: Enhanced Swift-XRT position
  60. GRB 250530C: Swift detection of a burst
  61. GRB 250530A: EP-FXT counterpart detection
  62. GRB 250530A: SVOM/VT optical upper limit
  63. GRB 250530A: Swift-XRT counterpart detection
  64. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  65. GRB 250527C: Swift/UVOT Upper Limits
  66. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  67. GRB 250527B: Swift-XRT observations
  68. GRB 250520A: Swift-BAT refined analysis
  69. GRB 250527C: Swift ToO observations
  70. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  71. GRB 250527B: Tiled Swift observations
  72. GRB 250520A: GRBAlpha detection
  73. GRB 250521B: SVOM/VT optical upper limit
  74. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  75. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  76. EP#01709176612: Swift-XRT counterpart detection of flaring star
  77. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  78. GRB 250521B: Swift ToO observations
  79. Konus-Wind detection of GRB 250520A (short/hard)
  80. GRB 250520A: Swift/UVOT Upper Limits
  81. IPN triangulation of GRB 250516B
  82. GRB 250520A: J-band observations with WINTER
  83. GRB 250520A: Swift-XRT refined Analysis
  84. GRB 250520A: REM optical/NIR early observations
  85. GRB 250520A:SVOM/VT optical candidate
  86. GRB 250520A: COLIBRÍ optical upper limit
  87. GRB 250520A: DDOTI Optical Upper Limit
  88. GRB 250520A: AstroSat CZTI detection of a short burst
  89. GRB 250520A: SVOM/GRM observation
  90. GRB 250520A: Enhanced Swift-XRT position
  91. GRB 250520A: GOTO optical upper limit
  92. GRB 250520A: Prompt enhanced Swift-XRT position
  93. GRB 250520A: Swift detection of a burst
  94. Swift GRB 250520A: Global MASTER-Net observations report
  95. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  96. GRB 250516A: Swift-BAT refined analysis
  97. Konus-Wind detection of GRB 250516A
  98. GRB 250515A: Swift-XRT observations
  99. Swift GRB 250516A: Global MASTER-Net observations report
  100. GRB 250516A: AstroSat CZTI detection

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