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"

35983 results found.

  1. GRB 260511A: BALROG localization (Fermi Trigger 800172815 / GRB 260511259)
  2. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  3. GRB 260511A: Fermi GBM Final Real-time Localization
  4. GRB 260510B: SVOM/VT optical upper limits
  5. GRB 260510C: SVOM/VT optical upper limits
  6. GRB 260510C: MAXI/GSC detection
  7. Fermi GBM Sub-Threshold Detection of GRB 260510B
  8. GRB 260510D: Fermi GBM Final Real-time Localization
  9. GRB 260510B: GOTO early upper limit
  10. GRB 260510C: SVOM detection of a burst
  11. GRB 260510C: Fermi GBM Final Real-time Localization
  12. GRB 260510A: GECAM-B observation
  13. GRB 260510B: LCO optical upper limits
  14. GRB 260509A: Liverpool Telescope optical observations
  15. GRB 260510B: SVOM detection of a burst
  16. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  17. GRB 260509A: LCO optical observations
  18. SVOM GRB 260509A: MASTER-OAFA optical observation
  19. Fermi GRB 260510A: Global MASTER-Net observations report
  20. GRB 260509A: KAIT optical observations
  21. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  22. GRB 260510A: Fermi GBM Final Real-time Localization
  23. GRB 260509A: SVOM/VT optical candidate with VHF data
  24. GRB 260509A: LCO optical counterpart detection
  25. GRB 260509A: GOTO optical counterpart candidate
  26. GRB 260509A: SVOM detection of a burst
  27. GRB 260506B: AstroSat CZTI detection
  28. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  29. GRB 260507A: Fermi GBM Final Real-time Localization
  30. GRB 260504B: AstroSat CZTI detection
  31. GRB 260504B: SVOM/ECLAIRs refined analysis
  32. GRB 260506B: BALROG localization (Fermi Trigger 799765648 / GRB 260506547)
  33. GRB 260506B: Fermi GBM Final Real-time Localization
  34. Fermi GRB 260506A: Global MASTER-Net observations report
  35. GRB 260506A: Fermi GBM Final Real-time Localization
  36. GRB 260503A: GECAM-B observation of a burst
  37. GRB 260430B: Glowbug gamma-ray detection
  38. GRB 260504B: SVOM/VT optical upper limits
  39. GRB 260421B: radio observation with the VLA
  40. Konus-Wind detection of GRB 260504B (short/hard)
  41. GRB 260504B: GECAM-B detection
  42. GRB 260504C: SVOM/GRM observation of short GRB
  43. GRB 260504B: SVOM/GRM spectral analysis
  44. GRB 260430B: AstroSat CZTI detection of a long burst
  45. GRB 260504B: SVOM/MXT refined analysis and potential detection
  46. GRB 260504B: EP-FXT upper limit
  47. GRB 260502A: SVOM/GRM observation of a short GRB
  48. GRB 260503A: SVOM/GRM observation of a GRB
  49. Konus-Wind detection of GRB 260415C
  50. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  51. Konus-Wind detection of GRB 260411C
  52. GRB 260504B: REM optical/NIR observations
  53. IPN triangulation of GRB 260429A
  54. IPN triangulation of GRB 260428A
  55. GRB 260504B: AST3-2 i-band upper limit
  56. GRB 260504B: LCO z-band upper limit
  57. SVOM GRB 260504B: MASTER-OAFA optical observations
  58. GRB 260504B: SVOM detection of a short burst
  59. Fermi GRB 260504A: Global MASTER-Net observations report
  60. GRB 260504A: Fermi GBM Final Real-time Localization
  61. GRB 260503A: Fermi GBM Final Real-time Localization
  62. GRB 260502A: GECAM-B observation of a short burst
  63. GRB 260502A: Fermi GBM Final Localization
  64. GRB 260429B / EP260429a: EP-FXT follow-up observation
  65. GRB 260429B / EP260429a: AstroSat CZTI detection
  66. GRB 260429A: SVOM/GRM observation of a short burst
  67. GRB 260424B: AstroSat CZTI detection
  68. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  69. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  70. GRB 260429A: Fermi GBM Detection
  71. Fermi GRB 260429A: Global MASTER-Net observations report
  72. GRB 260429A: Fermi GBM Final Real-time Localization
  73. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  74. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  75. GRB 260428A: AstroSat CZTI detection
  76. Fermi GRB 260428A: Global MASTER-Net observations report
  77. EP260416a: Mondy and Terskol optical upper limits
  78. GRB 260424B: Glowbug gamma-ray detection of a short burst
  79. GRB 260424B: COLIBRÍ optical upper limit
  80. Konus-Wind detection of GRB 260424B
  81. GRB 260428A: Fermi GBM Final Real-time Localization
  82. GRB 260424C: Fermi GBM Final Localization
  83. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  84. IPN triangulation of GRB 260424B (short)
  85. GRB 260424B: SVOM/GRM detection of a short burst
  86. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  87. GRB 260401A: cubesat Avion detection
  88. GRB 260424A: AstroSat CZTI detection of a long burst
  89. GRB 260421B: Kilonova-Catcher optical afterglow detection
  90. GRB 260421B: Insight-HXMT/HE detection
  91. The EP-WXT trigger 01709258652: Mondy optical observations
  92. GRB 250328A: VLT host galaxy discovery and redshift z = 1.250
  93. EP260416a: Mondy optical observations
  94. GRB 260421B: SVOM/ECLAIRs refined analysis
  95. GRB 260421B: 3.6m DOT optical observation
  96. EP260416a: ZTSh R band observations
  97. EP250512a / GRB 250512B: VLT/X-shooter host galaxy identification and redshift z = 1.773
  98. GRB 250530A: VLT/X-shooter host galaxy redshift z = 1.486
  99. GRB 260419A: AstroSat CZTI detection
  100. GRB 260421B: SVOM/GRM observation

Advanced

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