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"
  1. EP-WXT01709259790: Optical Upper limits with kinder observations
  2. GRB 260410A: Fermi GBM Observation
  3. GRB 260410B: SVOM/GRM detection of a short faint burst
  4. The EP-WXT trigger 01709259790 is likely a flaring star
  5. GRB 260410B: Fermi GBM Final Real-time Localization
  6. EP-WXT01709259790: Xinglong optical upper limit
  7. GRB 260410A: Fermi-LAT detection
  8. GRB 260410A: Fermi GBM Final Real-time Localization
  9. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  10. EP260321a: Chandra X-ray Non-detection
  11. GRB 260409A: Fermi GBM Final Real-time Localization
  12. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  13. The EP-WXT trigger 01709259773 is likely a flaring star
  14. GRB 260407A: GECAM-A detection
  15. GRB 260407A: Insight-HXMT/HE detection
  16. EP260409a: SVOM/VT optical upper limits
  17. EP260409a: COLIBRÍ optical upper limits
  18. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  19. EP260409a: Global MASTER-Net observations report
  20. EP260409a: Einstein Probe detection of an X-ray transient
  21. EP260321a: VLA radio detection
  22. GRB 260404A: Fermi GBM Final Localization
  23. GRB 260407A: Glowbug gamma-ray detection
  24. GRB 260402A: SVOM/ECLAIRs refined analysis
  25. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  26. GRB 260310A / AT2026fgk: X-ray rebrightening
  27. EP260402a / GRB 260402A: Mephisto optical upper limits
  28. EP-WXT01709259586: Xinglong optical upper limit
  29. EP260403a: Mephisto optical upper limits
  30. EP260402a/GRB 260402A: Xinglong optical upper limit
  31. EP260321a: Upper limits from VLA radio observations
  32. GRID detection of GRB 260401A
  33. EP260321a: uGMRT observations
  34. GRB 260407A: Fermi GBM Final Real-time Localization
  35. EP260405a: GMOS-N optical upper limits
  36. EP260405a: SVOM/VT optical upper limits
  37. EP260405a: Global MASTER-Net observations report
  38. EP260405a: Einstein Probe detection of a fast X-ray transient
  39. The EP-WXT trigger 01709259621 is likely a flaring star
  40. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  41. The EP-WXT trigger 01709259615 is likely a flaring star
  42. Fermi trigger No 797039833: Global MASTER-Net observations report
  43. GRB 260403A: GECAM-B observation of a long burst
  44. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  45. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  46. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  47. The EP-WXT trigger 01709259586 is likely a flaring star
  48. GRB 260330B: SVOM/VT further optical observation
  49. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  50. GRB 260330B: SVOM/ECLAIRs refined analysis
  51. EP260403a: LCO optical observations of the counterpart
  52. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  53. EP260403a: LCO optical counterpart detection
  54. EP260403a: COLIBRÍ optical counterpart candidate
  55. GRB 260330B: SVOM/VT optical candidate
  56. EP260403a: Einstein Probe detection of an X-ray transient
  57. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  58. GRB 260403A: AstroSat CZTI detection
  59. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  60. GRB 260402B: GECAM-B observation
  61. EP260402a/GRB 260402A: Jinshan near-infrared upper limit
  62. GRB 260402C: NuSTAR detection of prompt emission
  63. GRB 260402C: AstroSat CZTI detection of a long burst
  64. EP260324A / AT 2026hir: COLIBRÍ optical observations
  65. GRB 260403A: Fermi GBM Final Real-time Localization
  66. EP260324A / AT 2026hir: Spectroscopic Observations with the Next Generation Palomar Spectrograph
  67. GRB 260402B: Fermi GBM Final Real-time Localization
  68. GRB 260402A: WINTER J-band upper limit
  69. GRB260402A: GROWTH-India Telescope optical upper limit
  70. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  71. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  72. GRB 260401A: SVOM/GRM observation
  73. GRB 260401A: GECAM-B observation
  74. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  75. GRB 260402A: Kilonova-Catcher optical upper limit
  76. GRB 260402A: MASTER optical observations
  77. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  78. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  79. GRB 260402A: SVOM detection of a burst
  80. Fermi GRB 260401A: Global MASTER-Net observations report
  81. GRB 260401A: Fermi GBM Observation
  82. GRB 260401A: NuSTAR detection of prompt emission
  83. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  84. GRB 260401A: MAXI/GSC detection
  85. GRB 260401A: BALROG localization (Fermi Trigger 796733611 / GRB 260401454)
  86. GRB 260401A: Fermi GBM Final Real-time Localization
  87. EP260329b: Mondy and Assy-Turgen optical upper limits
  88. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  89. EP260321a :Xinglong optical observations
  90. EP260327a: Xinglong optical upper limit
  91. EP260329b: GOTO detection of optical counterpart
  92. GRB 260330B: SVOM/VT optical upper limits
  93. Konus-Wind detection of GRB 260320A
  94. Konus-Wind detection of GRB 260316B (duplicate submission)
  95. Konus-Wind detection of GRB 260316B
  96. GRB 260321A: SVOM/ECLAIRs refined analysis
  97. EP260329b: J-band upper limits with WINTER
  98. EP260329a: J-band upper limit with WINTER
  99. GRB 260330A: Glowbug gamma-ray detection
  100. GRB 260310A: VLA Multi-frequency Radio Observations

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