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"

5817 results found.

  1. GRB 260504B: AstroSat CZTI detection
  2. IceCube Alert 260505A: Global MASTER-Net observations report
  3. Konus-Wind detection of GRB 260504B (short/hard)
  4. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  5. GRB 260504B: REM optical/NIR observations
  6. IPN triangulation of GRB 260429A
  7. GRB 260504B: AST3-2 i-band upper limit
  8. GRB 260504B: LCO z-band upper limit
  9. SVOM GRB 260504B: MASTER-OAFA optical observations
  10. Fermi GRB 260504A: Global MASTER-Net observations report
  11. GRB 260504A: Fermi GBM Final Real-time Localization
  12. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  13. Fermi GRB 260429A: Global MASTER-Net observations report
  14. EP260430a: Global MASTER-Net observations report
  15. Fermi GRB 260428A: Global MASTER-Net observations report
  16. EP260416a: Mondy and Terskol optical upper limits
  17. Fermi trigger No 798737427: Global MASTER-Net observations report
  18. Fermi GRB 260421C: Global MASTER-Net observations report
  19. Fermi GRB 260421B: Global MASTER-Net observations report
  20. Fermi GRB 260421A: Global MASTER-Net observations report
  21. GRB 260419A: Fermi GBM Final Real-time Localization
  22. Fermi GRB 260417B: Global MASTER-Net observations report
  23. EP260416a: Ondrejov D50 optical detection
  24. EP260417a: Global MASTER-Net observations report
  25. Fermi GRB 260417A: Global MASTER-Net observations report
  26. EP260416a: LCO observations confirm end of flaring phase
  27. Fermi trigger No 797912738: Global MASTER-Net observations report
  28. The EP-WXT trigger 01709260122 is likely a flaring star
  29. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  30. EP260409a: SVOM/VT optical upper limits
  31. EP260409a: COLIBRÍ optical upper limits
  32. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  33. EP260409a: Global MASTER-Net observations report
  34. GRB 260407A: Glowbug gamma-ray detection
  35. GRB 260407A: Fermi GBM Final Real-time Localization
  36. EP260405a: Global MASTER-Net observations report
  37. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  38. Fermi trigger No 797039833: Global MASTER-Net observations report
  39. EP260324A / AT 2026hir: COLIBRÍ optical observations
  40. GRB 260401A: MAXI/GSC detection
  41. EP260329b: J-band upper limits with WINTER
  42. EP260327a: Global MASTER-Net observations report
  43. IPN triangulation of GRB 260320A
  44. EP260321a: Upper limits from a neutrino search with IceCube
  45. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  46. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  47. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  48. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  49. EP260321a: Global MASTER-Net observations report
  50. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  51. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  52. GRB 260310A / AT2026fgk: LCO optical observations
  53. IceCube-260315A: COLIBRÍ optical observations
  54. EP260314a: optical upper limit with Kinder observations
  55. GRB 260310A / AT 2026fgk: iTelescope optical observations
  56. EP260314a: COLIBRÍ optical upper limit
  57. GRID detection of GRB 260312B
  58. EP260314a: Global MASTER-Net observations report
  59. Fermi trigger No 795185313: Global MASTER-Net observations report
  60. GRB 260310A / AT2026fgk: SAO RAS optical observations
  61. Fermi GRB 260313A: Global MASTER-Net observations report
  62. GRB 260312B: AstroSat CZTI detection
  63. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  64. GRB 260312B: Glowbug gamma-ray detection
  65. Fermi GRB 260311B: Global MASTER-Net observations report
  66. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  67. GRB 260312B: Fermi GBM Final Real-time Localization
  68. EP260306a: Mondy optical upper limit
  69. Fermi GRB 260310B: Global MASTER-Net observations report
  70. GRB 260207A: TESS Detection and Possible VLA Counterpart
  71. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  72. GRID detection of GRB 260223A
  73. GRB 260225A: WINTER J-band upper limit
  74. LAT GRB260226.44: Global MASTER-Net observations report
  75. Fermi GRB 260226A: Global MASTER-Net observations report
  76. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  77. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  78. EP260223a: Xinglong optical upper limit
  79. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  80. Fermi GRB 260223A: Global MASTER-Net observations report
  81. GRB 260223A: Fermi GBM Final Real-time Localization
  82. GRB 260222A: Fermi GBM Final Real-time Localization
  83. EP260221a: Xinglong optical upper limit
  84. IceCube Alert 260217A: Global MASTER-Net observations report
  85. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  86. GRB 260217A: Fermi GBM Final Localization
  87. GRB 260208A: continued Mondy optical observations
  88. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  89. EP260214b: LCO optical counterpart detection
  90. EP260213a: COLIBRÍ optical upper limits
  91. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  92. Fermi GRB 260212A: Global MASTER-Net observations report
  93. Fermi GRB 260210C: Global MASTER-Net observations report
  94. EP260210a: Global MASTER-Net observations report
  95. GRB 260208A: LCO detection of the optical counterpart
  96. GRB 260208B: AstroSat CZTI detection of a bright long burst
  97. GRB260208A: Liverpool Telescope optical follow-up observations
  98. Fermi GRB 260209A: Global MASTER-Net observations report
  99. GRB 260208A: Liverpool Telescope optical detection
  100. Fermi GRB 260208C: 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