Skip to main content
New! CHIME and DSA-110 FRB Notices, IceCube Notices and Schema v6.1.1. 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: FTW optical and NIR observations
  2. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  3. GRID detection of GRB 260131A/B
  4. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  5. GRB 260130A: Insight-HXMT/HE detection
  6. GRB 260130A: GECAM-B observation of a short burst
  7. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  8. GRB 260131A/B: EP/FXT X-ray afterglow detection
  9. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  10. GRB 260127B: Insight-HXMT/HE detection
  11. GRB 260127B: GECAM-B observation of a short burst
  12. GRB 260127A: GECAM-B observation
  13. GRB 260131A: NOT spectroscopic redshift z = 1.434
  14. EP260131a: Liverpool Telescope optical upper limits
  15. EP260131a: COLIBRÍ further observations
  16. Konus-Wind detection of GRB 260128A / EP260128a
  17. GRB 260131A: Insight-HXMT/HE detection
  18. Konus-Wind detection of GRB 260131A/B
  19. EP260131a: SVOM/VT optical observation
  20. EP260131a: Xinglong optical upper limit
  21. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  22. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  23. GRB 260131A/B: Fermi GBM Observation
  24. EP260131a: COLIBRÍ observations of slow optical fading
  25. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  26. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  27. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  28. GRB 260131B: MAXI/GSC detection
  29. GRB 260131A: Fermi GBM Final Real-time Localization
  30. EP260131a: COLIBRÍ optical observations of the counterpart
  31. EP260131a: Las Cumbres detection of an optical counterpart
  32. GRB 260127B: AstroSat CZTI detection
  33. GRB 260130A: Fermi GBM Detection
  34. EP260131a: Einstein Probe detection of an X-ray transient
  35. GRB 260127B: Fermi GBM Detection
  36. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  37. Fermi GRB 260130A: Global MASTER-Net observations report
  38. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  39. GRB 260130A: Fermi GBM Final Real-time Localization
  40. Fermi GRB 260129A: Global MASTER-Net observations report
  41. GRB 260128B: LCO optical upper limits
  42. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  43. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  44. IPN triangulation of GRB 260121A
  45. GRB 260127A: Swift-BAT refined analysis
  46. GRB 260129B: Fermi GBM Final Localization
  47. GRB 260128B: SVOM detection of a burst through offline search
  48. GRB 260129A: Fermi GBM Final Localization
  49. IPN triangulation of GRB 260127B (short)
  50. GRB 260127B: Swift-XRT observations
  51. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  52. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  53. EP260128a: NOT optical counterpart candidate
  54. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  55. EP260128a: Liverpool Telescope optical observations and possible counterpart
  56. EP260128a: LCO optical upper limits
  57. EP260126a: SVOM/VT optical upperlimit
  58. EP260128a: Global MASTER-Net observations report
  59. EP260128a: Einstein Probe detection of an X-ray transient
  60. Fermi GRB 260127A: Global MASTER-Net observations report
  61. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  62. GRB 260127A: Fermi GBM Observation
  63. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  64. GRB 260127A: COLIBRÍ optical observations
  65. GRB 260127A: NOT optical observations
  66. GRB 260127B: Swift ToO observations
  67. EP260126a: Seimei/TriCCS optical upper limit
  68. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  69. GRB 260127A: Swift-XRT refined Analysis
  70. GRB 260127B: GOTO candidate optical counterpart
  71. GRB 260127A: SVOM/C-GFT optical observations
  72. The EP-WXT trigger 01709253145 is likely a flaring star
  73. GRB 260127A: Enhanced Swift-XRT position
  74. Fermi GRB 260127B: Global MASTER-Net observations report
  75. GRB 260127B: Fermi GBM Final Real-time Localization
  76. GRB 260127A: Prompt enhanced Swift-XRT position
  77. Swift GRB 260127A: Global MASTER-Net observations report
  78. GRB 260127A: LCO optical afterglow discovery
  79. GRB 260127A: Swift detection of a burst
  80. GRB 260127A: Fermi GBM Final Real-time Localization
  81. GRB 260125A: Swift-XRT observations
  82. EP260126a: EP-FXT follow-up observation
  83. EP260126a: Optical upper limit with Kinder observations
  84. EP260126a: Liverpool Telescope optical upper limits
  85. EP260126a: Further NOT optical upper limits
  86. EP260126a: COLIBRÍ optical upper limits
  87. EP260126a: NOT optical observations
  88. EP260126a: Einstein Probe detection of a fast X-ray transient
  89. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  90. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  91. Konus-Wind detection of GRB 260120B
  92. GRB 251222A: SVOM/ECLAIRs refined analysis
  93. GRB 260125A: Swift ToO observations
  94. GRB 260125A: GOTO candidate optical counterpart
  95. Fermi GRB 260125B: Global MASTER-Net observations report
  96. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  97. GRB 260125B: Fermi GBM Final Real-time Localization
  98. GRB 260125A: Fermi GBM Final Real-time Localization
  99. GRB 260114A: SVOM/VT optical upper limits
  100. GRB 260120A: AstroSat CZTI detection

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