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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"

3400 results found.

  1. GRB 251011B: Swift-XRT refined Analysis
  2. GRB 251011B : MASTER optical observations
  3. GRB 251006B/EP251006a: EP-FXT afterglow detection
  4. GRB 251007A: Swift-XRT refined Analysis
  5. GRB 251007B: Swift-XRT refined Analysis
  6. GRB 251006B/EP251006a: EP-FXT follow-up observation
  7. GRB 251005C: Swift-XRT refined Analysis
  8. GRB 251002A: Swift/UVOT detection
  9. GRB 251003A: Swift-XRT refined Analysis
  10. GRB 251002A: Swift-XRT afterglow detection
  11. GRB 251001B: Swift-XRT refined Analysis
  12. GRB 250925A: Swift-XRT refined Analysis
  13. GRB 250925A: Swift/UVOT Upper Limits
  14. GRB 250924A: Swift-XRT refined Analysis
  15. GRB 250920C: Swift-XRT refined Analysis
  16. GRB 250920B: Swift-XRT refined Analysis
  17. GRB 250919A: Swift-XRT afterglow detection
  18. GRB 250919A: Fermi-LAT detection
  19. GRB 250917B: VLT/HAWK-I near-infrared observations
  20. GRB 250916A: Swift-XRT observations
  21. EP250916a: EP-FXT follow-up observation
  22. GRB 250917B: Swift-XRT observations
  23. GRB 250912A: Swift-XRT observations
  24. GRB 250911A: Swift-XRT refined Analysis
  25. EP250911a: Swift-XRT observations
  26. GRB 250911A: Swift/UVOT Detection
  27. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  28. GRB 250702B: Late time Chandra observations
  29. EP#01709240653: Swift-XRT observations
  30. GRB 250903A: Swift-XRT afterglow detection
  31. EP250905b: EP-FXT follow-up observation
  32. GRB 250905A: Swift-XRT refined Analysis
  33. GRB 250903A: Swift/UVOT detection
  34. GRB 250904A: Swift-XRT refined Analysis
  35. GRB 250903A: Swift-XRT observations
  36. EP250903a: Swift-XRT observations
  37. EP#01709201209: Swift-XRT observations
  38. GRB 250901A: Swift/UVOT Upper Limit
  39. GRB 250830B: Swift-XRT afterglow detection
  40. GRB 250901A: EP-FXT follow-up observation
  41. GRB 250901A: Swift-XRT afterglow detection
  42. EP250901a: Swift-XRT observations
  43. EP250831a: EP-FXT follow-up observation
  44. EP250831a: Swift-XRT observations
  45. GRB 250831A: Swift-XRT counterpart detection
  46. GRB 250830B: Swift-XRT observations
  47. EP250827a: Swift/UVOT Detection
  48. EP250827a: Swift-XRT counterpart detection
  49. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  50. GRB 250823A: Swift-XRT refined Analysis
  51. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  52. EP250821a: Swift/XRT counterpart fading
  53. GRB 250821A: Swift-XRT refined Analysis
  54. LIGO/Virgo/KAGRA S250818k: ENGRAVE observations of AT 2025ulz
  55. EP250821a: Swift XRT and UVOT counterpart detection
  56. GRB 250821A: Prompt enhanced Swift-XRT position
  57. LIGO/Virgo/KAGRA S250818k: EP/FXT observation of AT 2025ulz
  58. GRB 250813B: Swift/UVOT Upper Limit
  59. GRB 250818B: Swift/UVOT Detection
  60. GRB 250818A: Swift-XRT refined Analysis
  61. GRB 250818B: EP-FXT counterpart detection
  62. GRB 250818B: Swift-XRT afterglow detection
  63. sb25081602: Swift-XRT observations
  64. LIGO/Virgo/KAGRA S250813k: Swift XRT observations, 2 X-ray sources
  65. GRB 250814A: P200/WIRC observations of the afterglow candidate
  66. GRB 250814A: Swift-XRT refined Analysis
  67. GRB 250814A: Possible afterglow candidate from P200/WIRC
  68. GRB 250813B: EP-FXT counterpart detection
  69. GRB 250813B: Swift-XRT afterglow detection
  70. GRB 250812A: Swift/UVOT Detection
  71. EP250812a: Swift-XRT counterpart detection
  72. GRB 250812A: Swift-XRT afterglow detection
  73. GRB 250809A: Swift-XRT refined Analysis
  74. GRB 250702B: Chandra X-ray Detection
  75. GRB 250808A: Swift-XRT candidate counterpart detection
  76. GRB 250807A: Swift-XRT refined Analysis
  77. GRB 250807B: Swift-XRT refined Analysis
  78. GRB 250806A: EP-FXT observation
  79. EP#01709198415/EP250806a: Swift-XRT observations
  80. EP250802a: EP-FXT follow-up observation
  81. GRB 250806A: Swift-XRT counterpart detection
  82. GRB 250805A: Swift-XRT refined Analysis
  83. GRB 250804B: Swift-XRT observations
  84. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  85. LIGO/Virgo/KAGRA S250727dc: Swift-XRT observations, 8 X-ray sources
  86. GRB 250728A: Swift-XRT observations
  87. GRB 250727A: Swift-XRT observations
  88. GRB 250725A: Swift-XRT refined Analysis
  89. SVOM J195836+32283 is not a real source
  90. SVOM J195836+32283/sb25072103: Swift XRT/UVOT upper limits
  91. GRB 250721A: Swift-XRT observations
  92. Fermi trigger No 774730635: Global MASTER-Net observations report
  93. GRB 250717B: Swift-XRT observations
  94. GRB 250716A: Swift-XRT afterglow detection
  95. GRB 250713A: Swift-XRT observations
  96. GRB250702 B,D,E / EP250702a: MOSFIRE imaging of the afterglow
  97. IceCube-250706A: EP-FXT follow-up observations
  98. GRB 250706B/C: Fermi-LAT detection
  99. GRB 250706B: Swift/UVOT Detection
  100. EP250702a/ GRB 250702B: NuSTAR X-ray Observations

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