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"

40744 results found.

  1. GRB 260509A: Liverpool Telescope optical observations
  2. GRB 260510B: SVOM detection of a burst
  3. GRB 260509A: NOT spectroscopic redshift upper limit z < 1.95
  4. GRB 260509A: LCO optical observations
  5. SVOM GRB 260509A: MASTER-OAFA optical observation
  6. Fermi GRB 260510A: Global MASTER-Net observations report
  7. GRB 260509A: KAIT optical observations
  8. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  9. GRB 260509A: SVOM/VT optical candidate with VHF data
  10. GRB 260509A: LCO optical counterpart detection
  11. GRB 260509A: GOTO optical counterpart candidate
  12. GRB 260509A: SVOM detection of a burst
  13. GRB 260506B: AstroSat CZTI detection
  14. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  15. EP260507a: REM optical/NIR observations
  16. EP260507a: refined analysis of the EP-WXT and EP-FXT observations
  17. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  18. EP260507a: COLIBRÍ optical observations
  19. EP260507a: SVOM/VT optical observations
  20. EP260507a: NOT optical observations
  21. EP260507a: further Liverpool Telescope observations
  22. EP260507a: Liverpool Telescope optical upper limits
  23. EP260507a: GOTO optical counterpart detection
  24. EP260507a: TRT optical counterpart detection
  25. EP260507a: Kinder optical counterpart candidate
  26. EP260507a: LCO optical counterpart
  27. EP260507a: Einstein Probe detection of an X-ray transient
  28. GRB 260504B: AstroSat CZTI detection
  29. GRB 260504B: SVOM/ECLAIRs refined analysis
  30. EP260502a is likely a flaring star
  31. Fermi GRB 260506A: Global MASTER-Net observations report
  32. GRB 260503A: GECAM-B observation of a burst
  33. IceCube Alert 260505A: Global MASTER-Net observations report
  34. GRB 260430B: Glowbug gamma-ray detection
  35. GRB 260504B: SVOM/VT optical upper limits
  36. GRB 260421B: radio observation with the VLA
  37. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  38. Konus-Wind detection of GRB 260504B (short/hard)
  39. GRB 260504B: GECAM-B detection
  40. Fermi-LAT Gamma-ray Observations of IceCube-260504A
  41. GRB 260504C: SVOM/GRM observation of short GRB
  42. GRB 260504B: SVOM/GRM spectral analysis
  43. GRB 260430B: AstroSat CZTI detection of a long burst
  44. GRB 260504B: SVOM/MXT refined analysis and potential detection
  45. GRB 260504B: EP-FXT upper limit
  46. GRB 260502A: SVOM/GRM observation of a short GRB
  47. GRB 260503A: SVOM/GRM observation of a GRB
  48. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  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. SVOM/GRM observation of a bright burst from SGR 1E1841-045
  61. GRB 260502A: GECAM-B observation of a short burst
  62. IPN triangulation of a bright burst from SGR 1E1841-045
  63. The EP-WXT trigger 01709261576 is likely a flaring star
  64. GRB 260429B / EP260429a: EP-FXT follow-up observation
  65. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  66. GRB 260429B / EP260429a: AstroSat CZTI detection
  67. EP260502a: BOOTES-7: early optical upper limit
  68. EP260502a: Las Cumbres upper limit
  69. EP260502a: Einstein Probe detection of an X-ray transient
  70. GRB 260429A: SVOM/GRM observation of a short burst
  71. SN 2026kid: Optical follow-up with small-aperture telescopes in Spain and China
  72. EP260429a: Global MASTER-Net observations report
  73. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  74. GRB 260424B: AstroSat CZTI detection
  75. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  76. EP260429a: LCO optical upper limits
  77. EP260430a: LCO optical upper limits
  78. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  79. GRB 260429A: Fermi GBM Detection
  80. Fermi GRB 260429A: Global MASTER-Net observations report
  81. EP260430a: Global MASTER-Net observations report
  82. EP260430a: Einstein Probe detection of an X-ray transient
  83. EP260429a: EP-WXT detection of a fast X-ray transient
  84. GRB 260428A: SVOM/GRM observation of a possible short burst with extended emission
  85. GRB 260428A: GECAM-B detection of a possible long duration Type I burst
  86. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  87. GRB 260428A: AstroSat CZTI detection
  88. Fermi GRB 260428A: Global MASTER-Net observations report
  89. EP260416a: Mondy and Terskol optical upper limits
  90. GRB 260424B: Glowbug gamma-ray detection of a short burst
  91. GRB 260424B: COLIBRÍ optical upper limit
  92. Konus-Wind detection of GRB 260424B
  93. Fermi-LAT Gamma-ray Observations of IceCube-260425A
  94. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  95. IPN triangulation of GRB 260424B (short)
  96. GRB 260424B: SVOM/GRM detection of a short burst
  97. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  98. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  99. IceCube Alert 260425A: Global MASTER-Net observations report
  100. Fermi trigger No 798737427: 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