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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"

3401 results found.

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

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