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. EP260314a: Xinglong optical upper limit
  2. EP260314a: optical upper limit with Kinder observations
  3. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  4. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  5. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  6. GRB 260310A / AT 2026fgk: iTelescope optical observations
  7. EP260314a: COLIBRÍ optical upper limit
  8. GRID detection of GRB 260312B
  9. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  10. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  11. EP260314a: BOOTES-6/DPR optical upper limits at early times
  12. EP260314a: Global MASTER-Net observations report
  13. EP260314a: SVOM/VT optical candidate
  14. Fermi trigger No 795185313: Global MASTER-Net observations report
  15. IceCube Alert 260315A: Global MASTER-Net observations report
  16. EP260314a: Einstein Probe detection of an X-ray transient
  17. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  18. GRB 260314A: GECAM-B observation of a burst
  19. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  20. GRB 260310A / AT2026fgk: SAO RAS optical observations
  21. GRB 260310A/AT2026fgk: radio detection at 15GHz
  22. GRB 260310A / AT2026fgk: TNG NIR detection
  23. GRB 260310A / AT2026fgk: OASDG optical observations
  24. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  25. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  26. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  27. Fermi GRB 260314A: Global MASTER-Net observations report
  28. Fermi GRB 260313A: Global MASTER-Net observations report
  29. GRB 260314A: Fermi GBM Final Real-time Localization
  30. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  31. GRB 260313A: A Correction to the Fermi GBM Final Localization
  32. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  33. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  34. GRB 260310B: Insight-HXMT/HE detection
  35. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  36. GRB 260310A: NOT optical polarimetry
  37. GRB 260312B: AstroSat CZTI detection
  38. Swift BAT trigger 1500295: A solar flare
  39. GRB 260313A: Fermi GBM Final Real-time Localization
  40. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  41. Swift BAT trigger 1500287: A solar flare
  42. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  43. GRB 260308A: Insight-HXMT/HE detection
  44. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  45. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  46. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  47. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  48. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  49. GRB260310A / AT2026fgk: P200 Spectroscopy
  50. GRB 260312B: Glowbug gamma-ray detection
  51. GRB 260310A: Fermi GBM Observation
  52. GRB 260310A: potential optical counterpart
  53. Fermi GRB 260312B: Global MASTER-Net observations report
  54. Fermi GRB 260311B: Global MASTER-Net observations report
  55. Swift BAT trigger 1500148: A solar flare
  56. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  57. GRB 260312B: Fermi GBM Final Real-time Localization
  58. The EP-WXT trigger 01709258843 is not a real source
  59. GRB 260310B: GECAM-B observation of a burst
  60. Retraction of GCN 43965: GRB is actually solar flare
  61. GRB 260312A: Swift detection of a burst
  62. GRB 260311B: Fermi GBM Final Real-time Localization
  63. GRB 260131A/B: radio detection with the VLA
  64. EP260302a: MeerKAT radio counterpart
  65. GRB260307A: GECAM-B observation of a burst
  66. GRB 260308A: SVOM/GRM observation of a short GRB
  67. EP260306a: Mondy optical upper limit
  68. GRB 260310A: AstroSat CZTI detection of a long burst
  69. GRB 260311A: Fermi GBM Final Real-time Localization
  70. Fermi GRB 260310B: Global MASTER-Net observations report
  71. GRB 260310B: Fermi GBM Final Real-time Localization
  72. Fermi GRB 260310A: Global MASTER-Net observations report
  73. GRB 260307B: SVOM/ECLAIRs refined analysis
  74. GRB 260208A: radio detection with the VLA
  75. GRB 260310A: Fermi GBM Final Real-time Localization
  76. GRB 260307A: Glowbug gamma-ray detection
  77. GRB 260308A: Fermi GBM Final Real-time Localization
  78. Fermi GBM Sub-Threshold Detection of GRB 260307B
  79. GRB 260307B: Mephisto optical upper limits
  80. GRB 260307B: possible NOT optical counterpart
  81. GRB 260307B: SVOM/VT upper limit with X band data analysis
  82. Fermi GRB 260307A: Global MASTER-Net observations report
  83. GRB260307B: GROWTH-India Telescope optical upper limit
  84. GRB 260307B: SVOM/VT optical candidate
  85. GRB 260307B: SVOM/C-GFT upper limit
  86. GRB 260307B: SVOM detection of a burst
  87. GRB 260307A: Fermi GBM Final Localization
  88. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  89. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  90. GRB 260207A: TESS Detection and Possible VLA Counterpart
  91. EP260302a: SVOM/VT optical observation
  92. EP260306a: Gemini-North redshift z = 4.773
  93. EP260306a: SVOM/VT optical observation
  94. EP260302a: Gemini-South redshift z = 1.535
  95. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  96. EP260306a: Einstein Probe detection of an X-ray transient
  97. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  98. EP260302a: Optical afterglow rebrightening
  99. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  100. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)

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