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. Konus-Wind detection of GRB 260131A/B
  2. EP260131a: SVOM/VT optical observation
  3. EP260131a: Xinglong optical upper limit
  4. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  5. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  6. GRB 260131A/B: Fermi GBM Observation
  7. EP260131a: COLIBRÍ observations of slow optical fading
  8. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  9. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  10. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  11. GRB 260131B: MAXI/GSC detection
  12. GRB 260131A: Fermi GBM Final Real-time Localization
  13. EP260131a: COLIBRÍ optical observations of the counterpart
  14. EP260131a: Las Cumbres detection of an optical counterpart
  15. GRB 260127B: AstroSat CZTI detection
  16. GRB 260130A: Fermi GBM Detection
  17. EP260131a: Einstein Probe detection of an X-ray transient
  18. GRB 260127B: Fermi GBM Detection
  19. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  20. Fermi GRB 260130A: Global MASTER-Net observations report
  21. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  22. GRB 260130A: Fermi GBM Final Real-time Localization
  23. Fermi GRB 260129A: Global MASTER-Net observations report
  24. GRB 260128B: LCO optical upper limits
  25. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  26. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  27. IPN triangulation of GRB 260121A
  28. GRB 260127A: Swift-BAT refined analysis
  29. GRB 260129B: Fermi GBM Final Localization
  30. GRB 260128B: SVOM detection of a burst through offline search
  31. GRB 260129A: Fermi GBM Final Localization
  32. IPN triangulation of GRB 260127B (short)
  33. GRB 260127B: Swift-XRT observations
  34. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  35. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  36. EP260128a: NOT optical counterpart candidate
  37. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260128a: Liverpool Telescope optical observations and possible counterpart
  39. EP260128a: LCO optical upper limits
  40. EP260126a: SVOM/VT optical upperlimit
  41. EP260128a: Global MASTER-Net observations report
  42. EP260128a: Einstein Probe detection of an X-ray transient
  43. Fermi GRB 260127A: Global MASTER-Net observations report
  44. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  45. GRB 260127A: Fermi GBM Observation
  46. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  47. GRB 260127A: COLIBRÍ optical observations
  48. GRB 260127A: NOT optical observations
  49. GRB 260127B: Swift ToO observations
  50. EP260126a: Seimei/TriCCS optical upper limit
  51. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  52. GRB 260127A: Swift-XRT refined Analysis
  53. GRB 260127B: GOTO candidate optical counterpart
  54. GRB 260127A: SVOM/C-GFT optical observations
  55. The EP-WXT trigger 01709253145 is likely a flaring star
  56. GRB 260127A: Enhanced Swift-XRT position
  57. Fermi GRB 260127B: Global MASTER-Net observations report
  58. GRB 260127B: Fermi GBM Final Real-time Localization
  59. GRB 260127A: Prompt enhanced Swift-XRT position
  60. Swift GRB 260127A: Global MASTER-Net observations report
  61. GRB 260127A: LCO optical afterglow discovery
  62. GRB 260127A: Swift detection of a burst
  63. GRB 260127A: Fermi GBM Final Real-time Localization
  64. GRB 260125A: Swift-XRT observations
  65. EP260126a: EP-FXT follow-up observation
  66. EP260126a: Optical upper limit with Kinder observations
  67. EP260126a: Liverpool Telescope optical upper limits
  68. EP260126a: Further NOT optical upper limits
  69. EP260126a: COLIBRÍ optical upper limits
  70. EP260126a: NOT optical observations
  71. EP260126a: Einstein Probe detection of a fast X-ray transient
  72. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  73. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  74. Konus-Wind detection of GRB 260120B
  75. GRB 251222A: SVOM/ECLAIRs refined analysis
  76. GRB 260125A: Swift ToO observations
  77. GRB 260125A: GOTO candidate optical counterpart
  78. Fermi GRB 260125B: Global MASTER-Net observations report
  79. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  80. GRB 260125B: Fermi GBM Final Real-time Localization
  81. GRB 260125A: Fermi GBM Final Real-time Localization
  82. GRB 260114A: SVOM/VT optical upper limits
  83. GRB 260120A: AstroSat CZTI detection
  84. GRB 260122B: Swift-BAT refined analysis
  85. GRB 260120B: SVOM/GRM observation
  86. GRB 260120A: GECAM-B observation
  87. GRB 260120B: AstroSat CZTI detection
  88. GRB 260114A: Insight-HXMT/HE detection
  89. GRB 260122B: Swift detection of a burst
  90. Swift GRB260122.97: Global MASTER-Net observations report
  91. EP260119a: Assy AZT-20 optical observations
  92. EP260119a: Mondy and SAO RAS optical upper limits
  93. GRB 260122A: Fermi GBM Final Real-time Localization
  94. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  95. EP260119a: Xinglong optical upper limit
  96. The EP-WXT trigger 01709251871 is likely a flaring star
  97. Fermi GRB 260120C: Global MASTER-Net observations report
  98. GRB 260120B: Swift-BAT refined analysis
  99. GRB 260120B: Swift-XRT refined Analysis
  100. EP260116a: COLIBRÍ further 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