Skip to main content
New! Browse Circulars by Event, Advanced Search, Sample Codes, Schema Release. 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"

24959 results found.

  1. Fermi trigger No 771072240: Global MASTER-Net observations report
  2. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  3. GRB 250605A: Swift/UVOT Upper Limits
  4. GRB 250527C: CrAO Optical Upper Limit
  5. GRB 250607A: SVOM/GRM observation of a long burst
  6. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  7. GRB 250605A: Swift-XRT refined Analysis
  8. GRB 250605A: Enhanced Swift-XRT position
  9. GRB 250605A: Swift detection of a burst
  10. IPN triangulation of GRB 250404B
  11. IPN triangulation of GRB 250529A
  12. GRB 250601A: PRIME H band upper limit.
  13. GRB 250601A: PRIME J band upper limit.
  14. GRB 250601A: VLT/FORS2 Optical Observation
  15. GRB 250601A: Fermi GBM Observation
  16. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  17. GRB 250603A: Swift/UVOT Upper Limits
  18. GRB 250603A: Swift-XRT refined Analysis
  19. GRB 250603A: Enhanced Swift-XRT position
  20. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  21. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  22. GRB 250602A: Fermi GBM Observation
  23. GRB 250602A: DDOTI Optical Upper Limit
  24. GRB 250530C: Swift-BAT refined analysis
  25. GRB 250601A: Swift/XRT candidate afterglow
  26. GRB 250601A: Swift-XRT observations
  27. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  28. GRB 250601A: Fermi GBM Final Real-time Localization
  29. EP#01709177494: SVOM/VT optical observations
  30. EP#01709177494: Swift-XRT counterpart detection of known source
  31. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  32. GRB 250530C: Swift-XRT refined Analysis
  33. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  34. GRB 250530C: Enhanced Swift-XRT position
  35. GRB 250530C: Swift detection of a burst
  36. GRB 250530A: EP-FXT counterpart detection
  37. GRB 250530A: SVOM/VT optical upper limit
  38. GRB 250530A: Swift-XRT counterpart detection
  39. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  40. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  41. GRB 250530A: SVOM detection of a burst
  42. GRB 250527C: Swift/UVOT Upper Limits
  43. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  44. GRB 250527B: Swift-XRT observations
  45. GRB 250520A: Swift-BAT refined analysis
  46. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  47. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  48. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  49. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  50. GRB 250314A: CIDER NB1008 upper limit
  51. EP250526a: COLIBRÍ optical upper limits
  52. EP250526a: Einstein Probe detection of a fast X-ray transient
  53. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  54. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  55. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  56. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  57. EP#01709176612: Swift-XRT counterpart detection of flaring star
  58. GRB 250521D: DDOTI Optical Upper Limit
  59. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  60. GRB 250521D: LAST tentative optical counterpart candidate
  61. GRB 250521A: DDOTI Optical Upper Limit
  62. GRB 250520A: VLT/FORS2 Optical Observation
  63. GRB 250502A: Tautenburg observations
  64. GRB 250520A: Swift/UVOT Upper Limits
  65. IPN triangulation of GRB 250516B
  66. GRB 250520A: J-band observations with WINTER
  67. GRB 250520A: Gemini-South optical observations
  68. GRB 250520A: Swift-XRT refined Analysis
  69. GRB 250520A: REM optical/NIR early observations
  70. GRB 250520A:SVOM/VT optical candidate
  71. GRB 250520A: COLIBRÍ optical upper limit
  72. GRB 250520A: DDOTI Optical Upper Limit
  73. GRB 250520A: AstroSat CZTI detection of a short burst
  74. GRB 250520A: Enhanced Swift-XRT position
  75. GRB 250520A: Swift detection of a burst
  76. GRB 250516A: Swift-BAT refined analysis
  77. GRB 250516A: COLIBRÍ optical upper limit
  78. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  79. GRB 250515A: Swift-XRT observations
  80. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  81. GRB 250515A: 1.6m Mephisto optical detection
  82. GRB 250516A: Fermi GBM Observation
  83. GRB 250516A: Swift-XRT refined Analysis
  84. GRB 250516A: Swift/UVOT Detection
  85. GRB 250516B: GECAM-B detection of a bright long burst
  86. GRB 250516A: Enhanced Swift-XRT position
  87. GRB 250516A: Swift detection of a burst
  88. MAXI GRB250515.65: Global MASTER-Net observations report
  89. GRB 250424A: COLIBRÍ detection of the associated supernova
  90. GRB 250502A: TESS observations
  91. GRB 250509A: Swift-BAT refined analysis
  92. Fermi GRB 250512A: Global MASTER-Net observations report
  93. EP250512a/GRB 250512B: REM optical/NIR observations
  94. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  95. GRB 250507B: AstroSat CZTI detection
  96. EP250511a: Gemini optical counterpart observation
  97. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  98. EP250511a: Mephisto optical upper limits
  99. GRB 250512B: SVOM detection of a burst
  100. EP250512a: Einstein Probe detection of an X-ray transient

Advanced

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