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. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  2. GRB 260131A/B: Fermi GBM Observation
  3. EP260131a: COLIBRÍ observations of slow optical fading
  4. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  5. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  6. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  7. GRB 260131B: MAXI/GSC detection
  8. GRB 260131A: Fermi GBM Final Real-time Localization
  9. EP260131a: COLIBRÍ optical observations of the counterpart
  10. EP260131a: Las Cumbres detection of an optical counterpart
  11. GRB 260127B: AstroSat CZTI detection
  12. GRB 260130A: Fermi GBM Detection
  13. EP260131a: Einstein Probe detection of an X-ray transient
  14. GRB 260127B: Fermi GBM Detection
  15. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  16. Fermi GRB 260130A: Global MASTER-Net observations report
  17. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  18. GRB 260130A: Fermi GBM Final Real-time Localization
  19. Fermi GRB 260129A: Global MASTER-Net observations report
  20. GRB 260128B: LCO optical upper limits
  21. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  22. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  23. IPN triangulation of GRB 260121A
  24. GRB 260127A: Swift-BAT refined analysis
  25. GRB 260129B: Fermi GBM Final Localization
  26. GRB 260128B: SVOM detection of a burst through offline search
  27. GRB 260129A: Fermi GBM Final Localization
  28. IPN triangulation of GRB 260127B (short)
  29. GRB 260127B: Swift-XRT observations
  30. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  31. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  32. EP260128a: NOT optical counterpart candidate
  33. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  34. EP260128a: Liverpool Telescope optical observations and possible counterpart
  35. EP260128a: LCO optical upper limits
  36. EP260126a: SVOM/VT optical upperlimit
  37. EP260128a: Global MASTER-Net observations report
  38. EP260128a: Einstein Probe detection of an X-ray transient
  39. Fermi GRB 260127A: Global MASTER-Net observations report
  40. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  41. GRB 260127A: Fermi GBM Observation
  42. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  43. GRB 260127A: COLIBRÍ optical observations
  44. GRB 260127A: NOT optical observations
  45. GRB 260127B: Swift ToO observations
  46. EP260126a: Seimei/TriCCS optical upper limit
  47. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  48. GRB 260127A: Swift-XRT refined Analysis
  49. GRB 260127B: GOTO candidate optical counterpart
  50. GRB 260127A: SVOM/C-GFT optical observations
  51. The EP-WXT trigger 01709253145 is likely a flaring star
  52. GRB 260127A: Enhanced Swift-XRT position
  53. Fermi GRB 260127B: Global MASTER-Net observations report
  54. GRB 260127B: Fermi GBM Final Real-time Localization
  55. GRB 260127A: Prompt enhanced Swift-XRT position
  56. Swift GRB 260127A: Global MASTER-Net observations report
  57. GRB 260127A: LCO optical afterglow discovery
  58. GRB 260127A: Swift detection of a burst
  59. GRB 260127A: Fermi GBM Final Real-time Localization
  60. GRB 260125A: Swift-XRT observations
  61. EP260126a: EP-FXT follow-up observation
  62. EP260126a: Optical upper limit with Kinder observations
  63. EP260126a: Liverpool Telescope optical upper limits
  64. EP260126a: Further NOT optical upper limits
  65. EP260126a: COLIBRÍ optical upper limits
  66. EP260126a: NOT optical observations
  67. EP260126a: Einstein Probe detection of a fast X-ray transient
  68. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  69. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  70. Konus-Wind detection of GRB 260120B
  71. GRB 251222A: SVOM/ECLAIRs refined analysis
  72. GRB 260125A: Swift ToO observations
  73. GRB 260125A: GOTO candidate optical counterpart
  74. Fermi GRB 260125B: Global MASTER-Net observations report
  75. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  76. GRB 260125B: Fermi GBM Final Real-time Localization
  77. GRB 260125A: Fermi GBM Final Real-time Localization
  78. GRB 260114A: SVOM/VT optical upper limits
  79. GRB 260120A: AstroSat CZTI detection
  80. GRB 260122B: Swift-BAT refined analysis
  81. GRB 260120B: SVOM/GRM observation
  82. GRB 260120A: GECAM-B observation
  83. GRB 260120B: AstroSat CZTI detection
  84. GRB 260114A: Insight-HXMT/HE detection
  85. GRB 260122B: Swift detection of a burst
  86. Swift GRB260122.97: Global MASTER-Net observations report
  87. EP260119a: Assy AZT-20 optical observations
  88. EP260119a: Mondy and SAO RAS optical upper limits
  89. GRB 260122A: Fermi GBM Final Real-time Localization
  90. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  91. EP260119a: Xinglong optical upper limit
  92. The EP-WXT trigger 01709251871 is likely a flaring star
  93. Fermi GRB 260120C: Global MASTER-Net observations report
  94. GRB 260120B: Swift-BAT refined analysis
  95. GRB 260120B: Swift-XRT refined Analysis
  96. EP260116a: COLIBRÍ further observations
  97. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  98. GRB 260120B: Fermi GBM Observation
  99. EP260105a: GTC/HiPERCAM optical observations
  100. GRB 260120B: Swift/UVOT Detection

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