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"

37959 results found.

  1. EP260329b: GOTO detection of optical counterpart
  2. GRB 260330B: SVOM/VT optical upper limits
  3. Konus-Wind detection of GRB 260320A
  4. Konus-Wind detection of GRB 260316B (duplicate submission)
  5. Konus-Wind detection of GRB 260316B
  6. GRB 260321A: SVOM/ECLAIRs refined analysis
  7. EP260329b: J-band upper limits with WINTER
  8. EP260329a: J-band upper limit with WINTER
  9. GRB 260330A: Glowbug gamma-ray detection
  10. GRB 260310A: VLA Multi-frequency Radio Observations
  11. Fermi GBM Sub-Threshold Detection of GRB 260330B
  12. GRB 260330B: LCO optical upper limits
  13. GRB 260330B: SVOM detection of a burst
  14. GRB 260330A: Fermi GBM Final Real-time Localization
  15. EP260329b: Global MASTER-Net observations report
  16. Fermi trigger No 796485221: Global MASTER-Net observations report
  17. GRB 260327A: Insight-HXMT/HE detection
  18. GRB 260326A: Insight-HXMT/HE detection
  19. GRID detection of GRB 260326A
  20. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  21. SMA Detection of GRB 260310A / AT 2026fgk
  22. GRB 260307B: ATCA Radio Upper Limits
  23. GRB 260327A: AstroSat CZTI detection of a long burst
  24. EP260327a: Global MASTER-Net observations report
  25. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  26. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  27. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  28. IPN triangulation of GRB 260320A
  29. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  30. GRB 260326A: Fermi GBM Detection
  31. GRB 260325A: Fermi GBM Final Localization
  32. GRB 260326A: Fermi GBM Final Real-time Localization
  33. Fermi Gamma-ray Burst Monitor trigger 796145512/260325647 is not a GRB
  34. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  35. IPN triangulation of GRB 260316B
  36. GRID detection of GRB 260320A
  37. Fermi Gamma-ray Burst Monitor trigger 796060650/260324665 is not a GRB
  38. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  39. GRB 260310A: LBT optical observations
  40. EP260321A: Mondy optical observations
  41. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  42. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  43. Fermi GRB 260323A: Global MASTER-Net observations report
  44. GRB 260323A: Fermi GBM Final Real-time Localization
  45. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  46. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  47. GRB 260322A: Fermi GBM Final Localization
  48. GRB 260320A: Glowbug gamma-ray detection
  49. Fermi Gamma-ray Burst Monitor trigger 795918973/260323025 is not a GRB
  50. GRB 260321A: EP-FXT follow-up observation
  51. GRB 260321A: SVOM/VT optical upper limits
  52. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  53. GRB 260320A: Insight-HXMT/HE detection
  54. GRB 260310A: continued optical observation at Mondy
  55. Fermi GBM Sub-Threshold Detection of GRB 260321A
  56. GRB 260321A: SVOM detection of a burst
  57. EP260321a: Global MASTER-Net observations report
  58. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  59. GRB 260318A: Glowbug gamma-ray detection
  60. GRB 260310A / AT 2026fgk: KAIT optical observations
  61. GRB 260320A: NuSTAR detection of prompt emission
  62. GRB 260310A / AT2026fgk: NuSTAR follow-up detection
  63. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  64. GRB 260310A / AT 2026fgk: FTW optical and NIR observations show no rebrightening
  65. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  66. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  67. GRB 260310A/AT2026fgk: LBT near-infrared observations
  68. NOEMA Detection of GRB 260310A / AT 2026fgk
  69. GRB 260318A: SVOM/GRM observation
  70. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  71. GRB 260318A: GECAM-B observation
  72. Fermi GRB 260318A: Global MASTER-Net observations report
  73. GRB 260318A: Fermi GBM Final Real-time Localization
  74. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  75. Fermi Gamma-ray Burst Monitor trigger 795096033/260312500 (GRB 260313A) is unlikely to be a GRB
  76. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  77. GRB 260310A / AT 2026fgk: radio detection with the VLA
  78. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  79. GRB 260310A / AT2026fgk: LCO optical observations
  80. GRB 260317A: Fermi GBM Final Localization
  81. GRB 260316B: GECAM-B observation
  82. GRB 260316B: SVOM/GRM observation
  83. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  84. GRB 260316B: AstroSat CZTI detection
  85. GRB 260316B: Fermi GBM Final Real-time Localization
  86. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  87. GRB 260314A: Glowbug gamma-ray detection
  88. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  89. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  90. GRB 260310A / AT 2026fgk: iTelescope optical observations
  91. GRID detection of GRB 260312B
  92. EP260314a: Global MASTER-Net observations report
  93. Fermi trigger No 795185313: Global MASTER-Net observations report
  94. IceCube Alert 260315A: Global MASTER-Net observations report
  95. GRB 260314A: GECAM-B observation of a burst
  96. Fermi Gamma-ray Burst Monitor trigger 795185313/260314534 is not a GRB
  97. GRB 260310A / AT2026fgk: SAO RAS optical observations
  98. GRB 260310A/AT2026fgk: radio detection at 15GHz
  99. GRB 260310A / AT2026fgk: TNG NIR detection
  100. GRB 260310A / AT2026fgk: OASDG optical 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