Skip to main content
New! BOOM Notices and Schema v7.0.0. 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"

5523 results found.

  1. GRB 260509A: Liverpool Telescope optical observations
  2. GRB 260509A: SVOM/VT optical candidate with VHF data
  3. GRB 260509A: LCO optical counterpart detection
  4. GRB 260509A: GOTO optical counterpart candidate
  5. GRB 260509A: SVOM detection of a burst
  6. EP260507a: Liverpool Telescope optical upper limits
  7. GRB 260504B: AstroSat CZTI detection
  8. IceCube Alert 260505A: Global MASTER-Net observations report
  9. Konus-Wind detection of GRB 260504B (short/hard)
  10. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  11. GRB 260504B: REM optical/NIR observations
  12. IPN triangulation of GRB 260429A
  13. GRB 260504B: AST3-2 i-band upper limit
  14. GRB 260504B: LCO z-band upper limit
  15. SVOM GRB 260504B: MASTER-OAFA optical observations
  16. Fermi GRB 260504A: Global MASTER-Net observations report
  17. GRB 260504A: Fermi GBM Final Real-time Localization
  18. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  19. Fermi GRB 260429A: Global MASTER-Net observations report
  20. EP260430a: Global MASTER-Net observations report
  21. Fermi GRB 260428A: Global MASTER-Net observations report
  22. EP260416a: Mondy and Terskol optical upper limits
  23. Fermi trigger No 798737427: Global MASTER-Net observations report
  24. Fermi GRB 260421C: Global MASTER-Net observations report
  25. Fermi GRB 260421B: Global MASTER-Net observations report
  26. Fermi GRB 260421A: Global MASTER-Net observations report
  27. GRB 260419A: Fermi GBM Final Real-time Localization
  28. Fermi GRB 260417B: Global MASTER-Net observations report
  29. EP260416a: Ondrejov D50 optical detection
  30. EP260417a: Global MASTER-Net observations report
  31. Fermi GRB 260417A: Global MASTER-Net observations report
  32. EP260416a: LCO observations confirm end of flaring phase
  33. Fermi trigger No 797912738: Global MASTER-Net observations report
  34. The EP-WXT trigger 01709260122 is likely a flaring star
  35. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  36. EP260409a: SVOM/VT optical upper limits
  37. EP260409a: COLIBRÍ optical upper limits
  38. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  39. EP260409a: Global MASTER-Net observations report
  40. GRB 260407A: Glowbug gamma-ray detection
  41. GRB 260407A: Fermi GBM Final Real-time Localization
  42. EP260405a: Global MASTER-Net observations report
  43. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  44. Fermi trigger No 797039833: Global MASTER-Net observations report
  45. EP260324A / AT 2026hir: COLIBRÍ optical observations
  46. GRB 260401A: MAXI/GSC detection
  47. EP260329b: J-band upper limits with WINTER
  48. EP260327a: Global MASTER-Net observations report
  49. IPN triangulation of GRB 260320A
  50. EP260321a: Upper limits from a neutrino search with IceCube
  51. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  52. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  53. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  54. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  55. EP260321a: Global MASTER-Net observations report
  56. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  57. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  58. GRB 260310A / AT2026fgk: LCO optical observations
  59. IceCube-260315A: COLIBRÍ optical observations
  60. EP260314a: optical upper limit with Kinder observations
  61. GRB 260310A / AT 2026fgk: iTelescope optical observations
  62. EP260314a: COLIBRÍ optical upper limit
  63. GRID detection of GRB 260312B
  64. EP260314a: Global MASTER-Net observations report
  65. Fermi trigger No 795185313: Global MASTER-Net observations report
  66. GRB 260310A / AT2026fgk: SAO RAS optical observations
  67. Fermi GRB 260313A: Global MASTER-Net observations report
  68. GRB 260312B: AstroSat CZTI detection
  69. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  70. GRB 260312B: Glowbug gamma-ray detection
  71. Fermi GRB 260311B: Global MASTER-Net observations report
  72. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  73. GRB 260312B: Fermi GBM Final Real-time Localization
  74. EP260306a: Mondy optical upper limit
  75. Fermi GRB 260310B: Global MASTER-Net observations report
  76. GRB 260207A: TESS Detection and Possible VLA Counterpart
  77. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  78. GRID detection of GRB 260223A
  79. GRB 260225A: WINTER J-band upper limit
  80. LAT GRB260226.44: Global MASTER-Net observations report
  81. Fermi GRB 260226A: Global MASTER-Net observations report
  82. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  83. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  84. EP260223a: Xinglong optical upper limit
  85. GRB 260223A: BALROG localization (Fermi Trigger 793512674 / GRB 260223174)
  86. Fermi GRB 260223A: Global MASTER-Net observations report
  87. GRB 260223A: Fermi GBM Final Real-time Localization
  88. GRB 260222A: Fermi GBM Final Real-time Localization
  89. EP260221a: Xinglong optical upper limit
  90. IceCube Alert 260217A: Global MASTER-Net observations report
  91. Fermi-LAT Gamma-ray Observations of IceCube-260217A
  92. GRB 260217A: Fermi GBM Final Localization
  93. GRB 260208A: continued Mondy optical observations
  94. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  95. EP260214b: LCO optical counterpart detection
  96. EP260213a: COLIBRÍ optical upper limits
  97. GRB 260213B: BALROG localization (Fermi Trigger 792697214 / GRB 260213736)
  98. Fermi GRB 260212A: Global MASTER-Net observations report
  99. Fermi GRB 260210C: Global MASTER-Net observations report
  100. EP260210a: Global MASTER-Net observations report

Advanced

Download all Circulars as a .tar.gz archive:
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