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"

38920 results found.

  1. GRB 250529B: Fermi GBM Final Real-time Localization
  2. GRB 250527B: Swift-XRT observations
  3. GRB 250529A: Fermi GBM Final Real-time Localization
  4. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  5. GRB 250520A: Swift-BAT refined analysis
  6. GRB 250527C: Swift ToO observations
  7. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  8. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  9. GRB 250527B: Tiled Swift observations
  10. GRB 250520A: Gemini-South optical afterglow detection
  11. Fermi trigger No 770058372: Global MASTER-Net observations report
  12. Fermi trigger No 770047117: Global MASTER-Net observations report
  13. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  14. GRB 250527A: Fermi GBM Final Localization
  15. GRB 250314A: CIDER NB1008 upper limit
  16. EP250526a: COLIBRÍ optical upper limits
  17. EP250526a: Global MASTER-Net observations report
  18. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  19. GRB 250520A: 3 GHz MeerKAT Detection
  20. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  21. Fermi GRB 250523A: Global MASTER-Net observations report
  22. Fermi trigger No 769611916: Global MASTER-Net observations report
  23. GRB 250521A: GRBAlpha detection
  24. GRB 250520A: GRBAlpha detection
  25. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  26. GRB 250523A: Fermi GBM Final Real-time Localization
  27. GRB 250521B: SVOM/VT optical upper limit
  28. Fermi GRB 250522B: Global MASTER-Net observations report
  29. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  30. GRB 250522B: Fermi GBM Final Localization
  31. GRB 250521D: SVOM/VT optical observations
  32. GRB 250522A: Fermi GBM Final Real-time Localization
  33. Fermi GRB 250521D: Global MASTER-Net observations report
  34. Fermi trigger No 769533898: Global MASTER-Net observations report
  35. Fermi trigger No 769499303: Global MASTER-Net observations report
  36. GRB 250521D: DDOTI Optical Upper Limit
  37. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  38. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. GRB 250521D: LAST tentative optical counterpart candidate
  40. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  41. GRB 250520A: 10 GHz VLA radio source
  42. GRB 250521B: Swift ToO observations
  43. GRB 250521D: Fermi GBM Final Real-time Localization
  44. GRB 250521C: Fermi GBM Final Localization
  45. GRB 250521A: DDOTI Optical Upper Limit
  46. GRB 250521B: SVOM detection of a burst through offline search
  47. Konus-Wind detection of GRB 250520A (short/hard)
  48. GRB 250520A: VLT/FORS2 Optical Observation
  49. GRB 250502A: Tautenburg observations
  50. GRB 250520A: Swift/UVOT Upper Limits
  51. GRB 250521A: Fermi GBM Final Real-time Localization
  52. Konus-Wind detection of GRB 250516B
  53. IPN triangulation of GRB 250516B
  54. GRB 250520A: J-band observations with WINTER
  55. GRB 250520A: Gemini-South optical observations
  56. GRB 250520A: Swift-XRT refined Analysis
  57. GRB 250520A: REM optical/NIR early observations
  58. GRB 250520B: Fermi GBM Final Real-time Localization
  59. GRB 250520A：SVOM/VT optical candidate
  60. GRB 250520A: COLIBRÍ optical upper limit
  61. GRB 250520A: DDOTI Optical Upper Limit
  62. GRB 250520A: AstroSat CZTI detection of a short burst
  63. GRB 250516B: GRBAlpha detection
  64. GRB 250520A: SVOM/GRM observation
  65. GRB 250520A: Enhanced Swift-XRT position
  66. GRB 250520A: GOTO optical upper limit
  67. GRB 250520A: Prompt enhanced Swift-XRT position
  68. GRB 250520A: Swift detection of a burst
  69. Swift GRB 250520A: Global MASTER-Net observations report
  70. GRB 250516B: Insight-HXMT detection
  71. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  72. GRB 250516A: Swift-BAT refined analysis
  73. GRB 250516A: COLIBRÍ optical upper limit
  74. Konus-Wind detection of GRB 250516A
  75. GRB 250516B: NuSTAR Detection of the Prompt Emission
  76. Fermi GRB 250516A: Global MASTER-Net observations report
  77. GRB 250515A: Swift-XRT observations
  78. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  79. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  80. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  81. Swift GRB 250516A: Global MASTER-Net observations report
  82. GRB 250515A: 1.6m Mephisto optical detection
  83. GRB 250516A: AstroSat CZTI detection
  84. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  85. GRB 250516A: Fermi GBM Observation
  86. GRB 250516A: Swift-XRT refined Analysis
  87. GRB 250516A: Swift/UVOT Detection
  88. GRB 250515A: Swift ToO observations
  89. GRB 250516B: GECAM-B detection of a bright long burst
  90. GRB 250516A: Enhanced Swift-XRT position
  91. GRB 250516A: Swift detection of a burst
  92. GRB 250516A: Fermi GBM Final Real-time Localization
  93. GRB 250512B / EP250512a: SVOM/GRM analysis
  94. GRB 250515A: GOTO candidate optical counterpart
  95. MAXI GRB250515.65: Global MASTER-Net observations report
  96. GRB 250515A: Fermi GBM Final Localization
  97. GRB 250424A: COLIBRÍ detection of the associated supernova
  98. Konus-Wind detection of GRB 250512B / EP250512a
  99. GRB 250502A: TESS observations
  100. Fermi trigger No 768922089: Global MASTER-Net observations report

Advanced

Download all Circulars as a .tar.gz archive (updated once a day):
Questions or comments?
Contact GCN directly.
Have you found a bug in GCN?
Open an issue.
Want to contribute code to GCN?
Get involved on GitHub.

gcn.nasa.gov

A service of the Astrophysics Science Division at NASA Goddard Space Flight Center

Looking for U.S. government information and services? Visit USA.gov