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. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  2. EP260416a: Global MASTER-Net observations report
  3. EP260416a: Einstein Probe detection of an X-ray transient
  4. GOTO26djh/AT2026jpw : MASTER OT observation
  5. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  6. GOTO26djh/AT2026jpw transient: SAO RAS optical observations
  7. NOT r-band observations of the transient GOTO26djh/AT2026jpw
  8. GRB 260415B: NuSTAR detection of long prompt emission
  9. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  10. GRB 260415B: Fermi GBM Final Localization
  11. GRB 260415A: Fermi GBM Final Real-time Localization
  12. Fermi trigger No 797912738: Global MASTER-Net observations report
  13. GRB 260414A: Glowbug gamma-ray detection
  14. EP260409a: Early NIR limits from MIRAGE on the MDM 1.3m telescope
  15. EP260321a: CMO SAI J,K observations
  16. GRB 260412A: Insight-HXMT/HE detection
  17. GRB 260414A: Fermi GBM Final Real-time Localization
  18. The EP-WXT trigger 01709260122 is likely a flaring star
  19. Fermi GRB 260413A: Global MASTER-Net observations report
  20. GRB 260410A: Glowbug gamma-ray detection of a short burst
  21. GRB 260413A: Fermi GBM Final Real-time Localization
  22. GRB 260410B: Insight-HXMT/HE detection
  23. GRB 260410A: Insight-HXMT/HE detection
  24. Konus-Wind detection of GRB 260410A (short/hard)
  25. GRB 260411B: GECAM-B observation of a long burst
  26. EP260321a: SVOM/VT optical observations and color changes around peak
  27. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  28. The EP-WXT trigger 01709260010 is likely a flaring star
  29. GRB 260412A: GECAM-B observation of a long burst
  30. Fermi GRB 260412A: Global MASTER-Net observations report
  31. GRB 260412A: Fermi GBM Observation
  32. GRB 260310A / AT2026fgk: NuSTAR detection of the rebrightening
  33. GRB 260411B: Fermi-LAT detection
  34. GRB 260412A: SVOM detection of a long burst
  35. GRB 260412A: Fermi GBM Final Real-time Localization
  36. GRB 260411B: COLIBRÍ optical observations
  37. GRB 260410B: Fermi GBM Observation
  38. GRB 260411B: Ondrejov D50 optical afterglow detection
  39. GRB260411B: 3.6m DOT optical observation
  40. GRB 260411A: SVOM/GRM observation
  41. GRB 260407B: SVOM/GRM detection of a possible magnetar X-ray burst
  42. GRB 260411B: SVOM/GRM observation of a long burst
  43. GRB 260409A: Insight-HXMT/HE detection
  44. GRB 260411B: Fermi GBM Detection
  45. GRB 260411B: GOTO optical counterpart candidate
  46. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  47. GRB 260411B: BALROG localization (Fermi Trigger 797587480 / GRB 260411337)
  48. GRB 260411B: Fermi GBM Final Real-time Localization
  49. GRB 260411A: Fermi GBM Final Real-time Localization
  50. GRB 260410A: COLIBRÍ optical upper limit
  51. EP-WXT01709259790: Optical Upper limits with kinder observations
  52. GRB 260410A: Fermi GBM Observation
  53. GRB 260410B: SVOM/GRM detection of a short faint burst
  54. The EP-WXT trigger 01709259790 is likely a flaring star
  55. GRB 260410B: Fermi GBM Final Real-time Localization
  56. EP-WXT01709259790: Xinglong optical upper limit
  57. GRB 260410A: Fermi-LAT detection
  58. GRB 260410A: Fermi GBM Final Real-time Localization
  59. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  60. EP260321a: Chandra X-ray Non-detection
  61. GRB 260409A: Fermi GBM Final Real-time Localization
  62. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  63. The EP-WXT trigger 01709259773 is likely a flaring star
  64. GRB 260407A: GECAM-A detection
  65. GRB 260407A: Insight-HXMT/HE detection
  66. EP260409a: SVOM/VT optical upper limits
  67. EP260409a: COLIBRÍ optical upper limits
  68. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  69. EP260409a: Global MASTER-Net observations report
  70. EP260409a: Einstein Probe detection of an X-ray transient
  71. EP260321a: VLA radio detection
  72. GRB 260404A: Fermi GBM Final Localization
  73. GRB 260407A: Glowbug gamma-ray detection
  74. GRB 260402A: SVOM/ECLAIRs refined analysis
  75. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  76. GRB 260310A / AT2026fgk: X-ray rebrightening
  77. EP260402a / GRB 260402A: Mephisto optical upper limits
  78. EP-WXT01709259586: Xinglong optical upper limit
  79. EP260403a: Mephisto optical upper limits
  80. EP260402a/GRB 260402A: Xinglong optical upper limit
  81. EP260321a: Upper limits from VLA radio observations
  82. GRID detection of GRB 260401A
  83. EP260321a: uGMRT observations
  84. GRB 260407A: Fermi GBM Final Real-time Localization
  85. EP260405a: GMOS-N optical upper limits
  86. EP260405a: SVOM/VT optical upper limits
  87. EP260405a: Global MASTER-Net observations report
  88. EP260405a: Einstein Probe detection of a fast X-ray transient
  89. The EP-WXT trigger 01709259621 is likely a flaring star
  90. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  91. The EP-WXT trigger 01709259615 is likely a flaring star
  92. Fermi trigger No 797039833: Global MASTER-Net observations report
  93. GRB 260403A: GECAM-B observation of a long burst
  94. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  95. Fermi Gamma-ray Burst Monitor trigger 796972356/260404217 is not a GRB
  96. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  97. The EP-WXT trigger 01709259586 is likely a flaring star
  98. GRB 260330B: SVOM/VT further optical observation
  99. Fermi Gamma-ray Burst Monitor trigger 796931884/260403749 is not a GRB
  100. GRB 260330B: SVOM/ECLAIRs refined analysis

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