Skip to main content
End of Swift Science Operations, CHIME Notices Unavailable During Upgrade. See news and announcements

GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

36191 results found.

  1. GRB 250827A: Fermi GBM Final Real-time Localization
  2. EP250827A: An optical rebrightening was detected by LCO.
  3. EP250827a / GRB 250827A: MASTER-OAFA OT observation
  4. Fermi GRB 250826A: Global MASTER-Net observations report
  5. GRB 250806A: HiPERCAM/GTC limits on a possible supernova
  6. LIGO/Virgo/KAGRA S250818k: SAO RAS BTA z-band observations of AT2025ulz
  7. Fermi Gamma-ray Burst Monitor trigger 777883624/250826283 is not a GRB
  8. GRB 250826A: Fermi GBM Final Real-time Localization
  9. Fermi GRB 250824B: Global MASTER-Net observations report
  10. GRB 250823A: Swift-BAT refined analysis
  11. GRB 250821B: AstroSat CZTI detection
  12. GRB 250819A: AstroSat CZTI detection
  13. GRB 250821B: Insight-HXMT detection
  14. GRB 250823A: Swift-XRT refined Analysis
  15. GRB 250824B: Fermi GBM Final Real-time Localization
  16. GRB 250823A: COLIBRÍ optical observations
  17. GRB 250823A: SVOM/VT optical observation
  18. GRB 250824A: Fermi GBM Final Real-time Localization
  19. GRB 250823A: Swift/UVOT Detection
  20. GRB 250823A: NOT optical observations
  21. GRB 250823A: Fermi GBM Observation
  22. GRB 250818B: MeerKAT Detection
  23. GRB 250823A: Enhanced Swift-XRT position
  24. GRB 250823A: LCOGT Optical Detection
  25. GRB 250823A: BOOTES6/DPRT early optical detection
  26. GRB 250823A: Liverpool Telescope optical detection
  27. GRB 250823A: Swift detection of a burst
  28. GRB 250823A: Fermi GBM Final Real-time Localization
  29. Konus-Wind detection of GRB 250821B
  30. GRB 250806A: Gemini observations of host galaxy candidate
  31. IPN triangulation of GRB 250821B (long/bright)
  32. GRB 250821A: Kilonova-Catcher optical upper limits
  33. GRB 250812A: SVOM/ECLAIRs refined analysis
  34. GRB 250821A: Swift-BAT refined analysis
  35. GRB 250821A: VLT/FORS2 Optical Observation
  36. GRB 250821A: GECAM-B detection
  37. GRB 250821B: SVOM/GRM observation
  38. Fermi GRB 250821B: Global MASTER-Net observations report
  39. GRB 250821A: NOT z-band upper limit
  40. GRB 250821C: Fermi GBM Final Real-time Localization
  41. GRB 250821A: KAIT optical upper limit
  42. GRB 250821A: Swift-XRT refined Analysis
  43. Swift GRB 250821A: Global MASTER-Net observations report
  44. GRB 250821B: Fermi GBM Detection
  45. GRB 250821B: BALROG localization (Fermi Trigger / GRB 250821672)
  46. GRB 250821B: Fermi GBM Final Localization of a Bright Burst
  47. GRB 250821A: Enhanced Swift-XRT position
  48. GRB 250821A: Swift/UVOT Upper Limits
  49. GRB 250821A: LCOGT Optical Upper Limits
  50. GRB 250814A: CMO SAI and SAO RAS izJ observations.
  51. GRB 250821A: Prompt enhanced Swift-XRT position
  52. GRB 250821A: Swift detection of a burst
  53. GRB 250819A: SVOM/GRM observation of a possible “long” duration type I burst
  54. GRB 250819A: Insight-HXMT detection
  55. GRB 250818B: 10 GHz VLA detection
  56. GRB 250814A: Swift/UVOT Upper Limits
  57. GRB 250813B: Swift/UVOT Upper Limit
  58. IPN triangulation of GRB 250816A (short)
  59. IPN triangulation of GRB 250814C (short)
  60. IPN triangulation of GRB 250804B (short)
  61. GRB 250818B: FTW optical and NIR observations show reddening of the counterpart
  62. GRB 250818B: Kilonova-Catcher optical afterglow detection
  63. GRB 250818B: Liverpool Telescope optical detections
  64. LIGO/Virgo/KAGRA S250818k: Upper limits from Fermi-GBM Observations
  65. GRB 250818A: AstroSat CZTI detection
  66. GRB 250818B: Swift/UVOT Detection
  67. Fermi Gamma-ray Burst Monitor trigger 777342746/250820022 is not a GRB
  68. GRB 250820A: Fermi GBM Final Real-time Localization
  69. GRB 250818B: optical afterglow detection with Lesedi (GOTO25fzq)
  70. GRB 250818B: TRT Optical Observation
  71. Fermi GRB 250816A: Global MASTER-Net observations report
  72. GRB 250818B: SAO RAS optical observations
  73. Swift GRB 250818A: Global MASTER-Net observations report
  74. GRB 250818B: NOT optical observations
  75. GRB 250818A: Swift-XRT refined Analysis
  76. GRB 250818B: EP-FXT counterpart detection
  77. GRB 250818A: Swift-BAT refined analysis
  78. Fermi Gamma-ray Burst Monitor trigger 777251788/250818970 is not a GRB
  79. GRB 250818C: Fermi GBM Final Real-time Localization
  80. GRB 250818B: Keck redshift of the optical afterglow
  81. GRB 250818B: KAIT optical observations
  82. GRB 250818A: Swift/UVOT Upper Limits
  83. GRB 250818A: Enhanced Swift-XRT position
  84. GRB 250813B: SVOM/ECLAIRs refined analysis
  85. GRB 250818A: Fermi GBM Observation
  86. GRB 250818B: SVOM/VT optical observation
  87. GRB 250814A: Further GRAWITA TNG NIR observations
  88. GRB 250818B: Swift-XRT afterglow detection
  89. GRB 250818B: GOTO optical counterpart candidate
  90. GRB 250818B: SVOM detection of a short burst
  91. GRB 250818A: Swift detection of a burst
  92. GRB 250818A: Fermi GBM Final Real-time Localization
  93. GRB 250816A: SVOM/GRM observation of a short burst
  94. Fermi GRB 250814B: Global MASTER-Net observations report
  95. GRB 250816A: Fermi GBM Final Real-time Localization
  96. GRB 250814A: Swift-BAT refined analysis
  97. GRB 250815A: Fermi GBM Final Localization
  98. GRB 250813B: Liverpool Telescope optical upper limits
  99. GRB 250814A: Further COLIBRÍ optical upper limit
  100. GRB 250814A: detection of the afterglow candidate with Liverpool Telescope

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