Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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"
  1. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  2. GRB 260310A / AT2026fgk: X-ray rebrightening
  3. EP260402a / GRB 260402A: Mephisto optical upper limits
  4. EP-WXT01709259586: Xinglong optical upper limit
  5. EP260403a: Mephisto optical upper limits
  6. EP260402a/GRB 260402A: Xinglong optical upper limit
  7. EP260321a: Upper limits from VLA radio observations
  8. GRID detection of GRB 260401A
  9. EP260321a: uGMRT observations
  10. GRB 260407A: Fermi GBM Final Real-time Localization
  11. EP260405a: GMOS-N optical upper limits
  12. EP260405a: SVOM/VT optical upper limits
  13. EP260405a: Global MASTER-Net observations report
  14. EP260405a: Einstein Probe detection of a fast X-ray transient
  15. The EP-WXT trigger 01709259621 is likely a flaring star
  16. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  17. The EP-WXT trigger 01709259615 is likely a flaring star
  18. Fermi trigger No 797039833: Global MASTER-Net observations report
  19. GRB 260403A: GECAM-B observation of a long burst
  20. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  21. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  22. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  23. The EP-WXT trigger 01709259586 is likely a flaring star
  24. GRB 260330B: SVOM/VT further optical observation
  25. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  26. GRB 260330B: SVOM/ECLAIRs refined analysis
  27. EP260403a: LCO optical observations of the counterpart
  28. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  29. EP260403a: LCO optical counterpart detection
  30. EP260403a: COLIBRÍ optical counterpart candidate
  31. GRB 260330B: SVOM/VT optical candidate
  32. EP260403a: Einstein Probe detection of an X-ray transient
  33. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  34. GRB 260403A: AstroSat CZTI detection
  35. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  36. GRB 260402B: GECAM-B observation
  37. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  38. GRB 260402C: NuSTAR detection of prompt emission
  39. GRB 260402C: AstroSat CZTI detection of a long burst
  40. EP260324A / AT 2026hir: COLIBRÍ optical observations
  41. GRB 260403A: Fermi GBM Final Real-time Localization
  42. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  43. GRB 260402B: Fermi GBM Final Real-time Localization
  44. GRB 260402A: WINTER J-band upper limit
  45. GRB260402A: GROWTH-India Telescope optical upper limit
  46. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  47. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  48. GRB 260401A: SVOM/GRM observation
  49. GRB 260401A: GECAM-B observation
  50. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  51. GRB 260402A: Kilonova-Catcher optical upper limit
  52. GRB 260402A: MASTER optical observations
  53. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  54. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  55. GRB 260402A: SVOM detection of a burst
  56. Fermi GRB 260401A: Global MASTER-Net observations report
  57. GRB 260401A: Fermi GBM Observation
  58. GRB 260401A: NuSTAR detection of prompt emission
  59. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  60. GRB 260401A: MAXI/GSC detection
  61. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  62. GRB 260401A: Fermi GBM Final Real-time Localization
  63. EP260329b: Mondy and Assy-Turgen optical upper limits
  64. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  65. EP260321a :Xinglong optical observations
  66. EP260327a: Xinglong optical upper limit
  67. EP260329b: GOTO detection of optical counterpart
  68. GRB 260330B: SVOM/VT optical upper limits
  69. Konus-Wind detection of GRB 260320A
  70. Konus-Wind detection of GRB 260316B (duplicate submission)
  71. Konus-Wind detection of GRB 260316B
  72. GRB 260321A: SVOM/ECLAIRs refined analysis
  73. EP260329b: J-band upper limits with WINTER
  74. EP260329a: J-band upper limit with WINTER
  75. GRB 260330A: Glowbug gamma-ray detection
  76. GRB 260310A: VLA Multi-frequency Radio Observations
  77. Fermi GBM Sub-Threshold Detection of GRB 260330B
  78. GRB 260330B: LCO optical upper limits
  79. GRB 260330B: SVOM detection of a burst
  80. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  81. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  82. EP260329a: COLIBRÍ optical upper limit
  83. EP260329a: EP-FXT follow up observation
  84. EP260329a: NOT optical counterpart candidate
  85. GRB 260330A: Fermi GBM Final Real-time Localization
  86. EP260329b: Global MASTER-Net observations report
  87. Fermi trigger No 796485221: Global MASTER-Net observations report
  88. GRB 260327A: Insight-HXMT/HE detection
  89. EP260329b: Optical follow-up with Kinder observations
  90. EP 260329b: COLIBRÍ optical observations
  91. EP260329a: Optical upper limit with Kinder observations
  92. EP260329b: LCO optical observations of the counterpart
  93. GRB 260326A: Insight-HXMT/HE detection
  94. EP260329b: Einstein Probe detection of an X-ray transient
  95. EP260329a: Einstein Probe detection of an X-ray transient
  96. EP-WXT trigger 01709259209: TRT optical counterpart detection
  97. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  98. GRID detection of GRB 260326A
  99. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  100. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations

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