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. EP-WXT01709259790: Xinglong optical upper limit
  2. GRB 260410A: Fermi-LAT detection
  3. GRB 260410A: Fermi GBM Final Real-time Localization
  4. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  5. EP260321a: Chandra X-ray Non-detection
  6. GRB 260409A: Fermi GBM Final Real-time Localization
  7. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  8. The EP-WXT trigger 01709259773 is likely a flaring star
  9. GRB 260407A: GECAM-A detection
  10. GRB 260407A: Insight-HXMT/HE detection
  11. EP260409a: SVOM/VT optical upper limits
  12. EP260409a: COLIBRÍ optical upper limits
  13. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  14. EP260409a: Global MASTER-Net observations report
  15. EP260409a: Einstein Probe detection of an X-ray transient
  16. EP260321a: VLA radio detection
  17. GRB 260404A: Fermi GBM Final Localization
  18. GRB 260407A: Glowbug gamma-ray detection
  19. GRB 260402A: SVOM/ECLAIRs refined analysis
  20. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  21. GRB 260310A / AT2026fgk: X-ray rebrightening
  22. EP260402a / GRB 260402A: Mephisto optical upper limits
  23. EP-WXT01709259586: Xinglong optical upper limit
  24. EP260403a: Mephisto optical upper limits
  25. EP260402a/GRB 260402A: Xinglong optical upper limit
  26. EP260321a: Upper limits from VLA radio observations
  27. GRID detection of GRB 260401A
  28. EP260321a: uGMRT observations
  29. GRB 260407A: Fermi GBM Final Real-time Localization
  30. EP260405a: GMOS-N optical upper limits
  31. EP260405a: SVOM/VT optical upper limits
  32. EP260405a: Global MASTER-Net observations report
  33. EP260405a: Einstein Probe detection of a fast X-ray transient
  34. The EP-WXT trigger 01709259621 is likely a flaring star
  35. EP260405.149 / EP-WXT 11900672904: COLIBRÍ optical upper limits
  36. The EP-WXT trigger 01709259615 is likely a flaring star
  37. Fermi trigger No 797039833: Global MASTER-Net observations report
  38. GRB 260403A: GECAM-B observation of a long burst
  39. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  40. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  41. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  42. The EP-WXT trigger 01709259586 is likely a flaring star
  43. GRB 260330B: SVOM/VT further optical observation
  44. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  45. GRB 260330B: SVOM/ECLAIRs refined analysis
  46. EP260403a: LCO optical observations of the counterpart
  47. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  48. EP260403a: LCO optical counterpart detection
  49. EP260403a: COLIBRÍ optical counterpart candidate
  50. GRB 260330B: SVOM/VT optical candidate
  51. EP260403a: Einstein Probe detection of an X-ray transient
  52. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  53. GRB 260403A: AstroSat CZTI detection
  54. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  55. GRB 260402B: GECAM-B observation
  56. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  57. GRB 260402C: NuSTAR detection of prompt emission
  58. GRB 260402C: AstroSat CZTI detection of a long burst
  59. EP260324A / AT 2026hir: COLIBRÍ optical observations
  60. GRB 260403A: Fermi GBM Final Real-time Localization
  61. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  62. GRB 260402B: Fermi GBM Final Real-time Localization
  63. GRB 260402A: WINTER J-band upper limit
  64. GRB260402A: GROWTH-India Telescope optical upper limit
  65. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  66. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  67. GRB 260401A: SVOM/GRM observation
  68. GRB 260401A: GECAM-B observation
  69. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  70. GRB 260402A: Kilonova-Catcher optical upper limit
  71. GRB 260402A: MASTER optical observations
  72. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  73. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  74. GRB 260402A: SVOM detection of a burst
  75. Fermi GRB 260401A: Global MASTER-Net observations report
  76. GRB 260401A: Fermi GBM Observation
  77. GRB 260401A: NuSTAR detection of prompt emission
  78. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  79. GRB 260401A: MAXI/GSC detection
  80. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  81. GRB 260401A: Fermi GBM Final Real-time Localization
  82. EP260329b: Mondy and Assy-Turgen optical upper limits
  83. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  84. EP260321a :Xinglong optical observations
  85. EP260327a: Xinglong optical upper limit
  86. EP260329b: GOTO detection of optical counterpart
  87. GRB 260330B: SVOM/VT optical upper limits
  88. Konus-Wind detection of GRB 260320A
  89. Konus-Wind detection of GRB 260316B (duplicate submission)
  90. Konus-Wind detection of GRB 260316B
  91. GRB 260321A: SVOM/ECLAIRs refined analysis
  92. EP260329b: J-band upper limits with WINTER
  93. EP260329a: J-band upper limit with WINTER
  94. GRB 260330A: Glowbug gamma-ray detection
  95. GRB 260310A: VLA Multi-frequency Radio Observations
  96. Fermi GBM Sub-Threshold Detection of GRB 260330B
  97. GRB 260330B: LCO optical upper limits
  98. GRB 260330B: SVOM detection of a burst
  99. EP260324a / AT2026hir: g- and r-band optical follow-up with the PKU 60cm Telescope
  100. EP260329b: refined analysis of the EP-WXT and 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