Skip to main content
Updates to LVK & CHIME Notices, Schema v7.2.3! See news and announcements

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"

26042 results found.

  1. GRB 250911A: Swift-XRT refined Analysis
  2. EP250911a: Swift-XRT observations
  3. GRB 250911A: Swift/UVOT Detection
  4. GRB 250910A / EP250910a: Swift-XRT afterglow detection
  5. GRB 250910A / EP250910a: SVOM/VT afterglow confirmation
  6. GRB 250910A / EP250910a : VLT/HAWK-I NIR counterpart discovery
  7. GRB 250911A: Enhanced Swift-XRT position
  8. GRB 250911A: Swift-XRT observations
  9. GRB 250911A: COLIBRÍ optical counterpart candidate
  10. GRB 250911A: Swift detection of a burst
  11. GRB 250910A / EP250910a: VLT/HAWK-I near-infrared observations
  12. GRB 250910A: SVOM/MXT possible afterglow detection
  13. GRB 250702B: Late time Chandra observations
  14. EP250908b/EP#01709240653: Swift/UVOT Detection
  15. EP#01709240653: Swift-XRT observations
  16. EP250908c: VLT/FORS2 optical counterpart identification
  17. GRB 250905A: Swift-BAT refined analysis
  18. GRB 250903A: Swift-XRT afterglow detection
  19. GRB 250905A: Swift-XRT refined Analysis
  20. GRB 250904A: Swift-BAT refined analysis
  21. GRB 250905A: Swift/UVOT Upper Limits
  22. GRB250904A: Liverpool Telescope upper limits
  23. GRB 250905A: Enhanced Swift-XRT position
  24. GRB 250904A: Swift/UVOT Detection
  25. GRB 250903A: Swift/UVOT detection
  26. GRB 250904A: Swift-XRT refined Analysis
  27. GRB 250905A: KAIT optical upper limit
  28. GRB 250905A: Swift detection of a burst
  29. Swift GRB250905.09: Global MASTER-Net observations report
  30. Swift GRB 250904A: Global MASTER-Net observations report
  31. GRB 250904A: Enhanced Swift-XRT position
  32. GRB 250904A: TRT optical counterpart detection
  33. GRB 250904A: Prompt enhanced Swift-XRT position
  34. GRB 250904A: Swift detection of a burst
  35. GRB 250903A: Swift-XRT observations
  36. EP250903a: Swift-XRT observations
  37. EP#01709201209: Swift-XRT observations
  38. EP250903a: retraction of the LCO candidate, and discovery of the likely counterpart
  39. GRB 250903A: VLT X-shooter spectroscopic redshift z = 1.590
  40. GRB 250903A: LCO optical observation
  41. GRB 250903A: LCO optical afterglow detection
  42. EP250901a: Mondy, Assy and SAO RAS optical limits
  43. Subject GRB 250903A: SVOM/MXT afterglow detection
  44. EP250903a: LCO candidate counterpart discovery
  45. GRB 250901A: Swift/UVOT Upper Limit
  46. GRB 250830B: Swift-XRT afterglow detection
  47. GRB 250831A (SVOM trigger sb25083102): confirmation of a stellar flare by SVOM/VT
  48. GRB 250901A: EP-FXT follow-up observation
  49. GRB 250901A: NOT optical observations
  50. GRB 250901A: SVOM/VT optical afterglow with VHF data
  51. GRB 250901A: Swift-XRT afterglow detection
  52. EP250901a: Swift-XRT observations
  53. GRB 250901A: LCO optical upper limit
  54. EP250827b: Swift observations of AT 2025wkm
  55. EP250831a: NOT optical observations and tentative afterglow candidate
  56. GRB 250901A: SVOM detection of a burst
  57. EP250831a: EP-FXT follow-up observation
  58. EP250831a: Swift-XRT observations
  59. GRB 250831A (SVOM trigger sb25083102) is likely an outburst from star G 272-61
  60. GRB 250831A: Swift-XRT counterpart detection
  61. GRB 250830B: Swift-XRT observations
  62. EP250830a/GRB 250830B: Einstein Probe detection of an X-ray transient and Swift/XRT follow-up
  63. GRB 250830B: Swift ToO observations
  64. GRB 250830B: MAXI/GSC detection
  65. GRB 250828B: Swift-BAT refined analysis
  66. EP250827a: very early ATLAS detections, starting 43 sec after the EP trigger
  67. Swift GRB 250828B: Global MASTER-Net observations report
  68. EP250828a: KAIT optical upper limit
  69. EP250827a: Swift/UVOT Detection
  70. GRB 250828B: Swift detection of a burst
  71. EP250827a: STEP/T80S Confirmation of fading optical counterpart
  72. EP250827a: confirmation of optical rebrightening with LCO
  73. EP250827a: GOTO observation of the optical afterglow
  74. EP250827a: Swift-XRT counterpart detection
  75. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  76. GRB 250823A: Swift-BAT refined analysis
  77. GRB 250823A: Swift-XRT refined Analysis
  78. LIGO/Virgo/KAGRA S250818k: Swift Observations of AT 2025ulz - Second Epoch
  79. GRB 250823A: COLIBRÍ optical observations
  80. GRB 250823A: SVOM/VT optical observation
  81. GRB 250823A: Swift/UVOT Detection
  82. GRB 250823A: NOT optical observations
  83. GRB 250823A: Fermi GBM Observation
  84. GRB 250818B: MeerKAT Detection
  85. GRB 250823A: Enhanced Swift-XRT position
  86. GRB 250823A: LCOGT Optical Detection
  87. GRB 250823A: BOOTES6/DPRT early optical detection
  88. GRB 250823A: Liverpool Telescope optical detection
  89. GRB 250823A: Swift detection of a burst
  90. Swift GRB250823.84: Global MASTER-Net observations report
  91. GRB 250821A: Kilonova-Catcher optical upper limits
  92. EP250821a: Swift/XRT counterpart fading
  93. GRB 250821A: Swift-BAT refined analysis
  94. EP250821a: Swift/UVOT further observations.
  95. GRB 250821A: VLT/FORS2 Optical Observation
  96. GRB 250821A: GECAM-B detection
  97. EP250821a: SVOM/VT optical observation
  98. GRB 250821A: NOT z-band upper limit
  99. GRB 250821A: KAIT optical upper limit
  100. GRB 250821A: Swift-XRT refined Analysis

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Looking for U.S. government information and services? Visit USA.gov