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"

5512 results found.

  1. GRB 260131A/B: continued Mondy optical observations
  2. GRB 260208A: Mondy optical observations
  3. GRB 260208A: Liverpool Telescope optical detection
  4. Fermi GRB 260208C: Global MASTER-Net observations report
  5. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  6. GRB 260206A: Swift-XRT observations
  7. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  8. GRB 260204A: Swift-XRT observations
  9. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  10. EP260131a: SVOM/VT optical observation
  11. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  12. GRB 260131B: MAXI/GSC detection
  13. Fermi GRB 260129A: Global MASTER-Net observations report
  14. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  15. GRB 260129B: Fermi GBM Final Localization
  16. Fermi GRB 260127A: Global MASTER-Net observations report
  17. GRB 260127B: GOTO candidate optical counterpart
  18. EP260119a: Mondy and SAO RAS optical upper limits
  19. Fermi GRB 260120C: Global MASTER-Net observations report
  20. EP260116a: COLIBRÍ further observations
  21. SVOM GRB260121.06: Global MASTER-Net observations report
  22. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  23. EP260119a: Global MASTER-Net observations report
  24. Fermi GRB 260115A: Global MASTER-Net observations report
  25. GRB260114A: STEP/T80S optical limits
  26. GRB 251222A: radio detection with the VLA
  27. GRB 260114A: COLIBRÍ optical upper limits
  28. EP260110a: NOT and GTC Optical and Near-Infrared Observations
  29. GRB 260111A: GOTO optical upper limits
  30. Swift trigger 1436759 is not an astrophysical event
  31. GRB 260109A: Fermi GBM Final Real-time Localization
  32. Fermi GRB 260107A: Global MASTER-Net observations report
  33. GRB 260102A: AbAO optical observations
  34. Fermi GRB 260105A: Global MASTER-Net observations report
  35. Fermi GRB 260105B: Global MASTER-Net observations report
  36. FRB 20251229A: A potentially hyperactive repeating fast radio burst source
  37. GRB 260101A: COLIBRÍ optical upper limits
  38. EP260105a: Global MASTER-Net observations report
  39. Fermi GRB 260104B: Global MASTER-Net observations report
  40. GRB 260101A: COLIBRÍ optical observations
  41. SVOM GRB260103.08: Global MASTER-Net observations report
  42. GRB 260102B: Fermi GBM Final Real-time Localization
  43. Fermi GBM Sub-Threshold Detection of GRB 260102A
  44. EP260101a: Global MASTER-Net observations report
  45. GRB 260102A: SVOM detection of a burst
  46. Fermi GRB 251228A: Global MASTER-Net observations report
  47. SVOM GRB251227.07: Global MASTER-Net observations report
  48. IceCube Alert 251225.84: Global MASTER-Net observations report
  49. EP251222a: NTT/ULTRACAM optical observations
  50. GRB 251222A / EP251222b: VLT/X-shooter spectroscopic redshift z = 3.171
  51. EP251221a: NOT optical upper limit
  52. IceCube-251218A: COLIBRÍ optical upper limits
  53. Fermi GRB 251215A: Global MASTER-Net observations report
  54. GRB 251203B: AbAO optical observations
  55. GRB 251214B: COLIBRÍ observations of the afterglow
  56. GRB 251214B: SVOM/C-GFT optical observations
  57. GRB 251214B: Swift detection of a burst with an optical counterpart
  58. EP251212a: Global MASTER-Net observations report
  59. GRB 251209A: NuSTAR detection of prompt emission
  60. EP251130a: Mondy and AbAO optical observations
  61. GRB 251209A: Fermi GBM Final Real-time Localization
  62. GRB 251208D: Swift-XRT observations
  63. GRB 251129A: e-MERLIN C-band observations
  64. LAT GRB251208.43: Global MASTER-Net observations report
  65. GRB 251205A: Liverpool Telescope further optical follow-up observations
  66. SVOM GRB251208D: Global MASTER-Net observations report
  67. GRB 251203A: AstroSat CZTI detection
  68. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  69. GRB 251203C: SVOM/VT optical counterpart
  70. GRB 251203C: EP-FXT follow-up observation
  71. GRB 251203B: Swift-XRT observations
  72. GRB 251203C: LCO optical upper limits
  73. GRB 251203B: LCO optical upper limits
  74. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  75. SVOM GRB251203.77: Global MASTER-Net observations report
  76. SVOM GRB251203B: Global MASTER-Net observations report
  77. GRB 251203A: Fermi GBM Final Real-time Localization
  78. GRB 251202B: Fermi GBM Final Real-time Localization
  79. GRB 251202A: GOTO optical afterglow detection
  80. EP251130a: SAO RAS optical observations
  81. GRB 251201A: MAXI/GSC detection
  82. GRB 251129A / EP251129a: SVOM/VT optical fading
  83. EP251129a: Global MASTER-Net observations report
  84. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  85. SVOM GRB251129A: Global MASTER-Net observations report
  86. GRB 251127A: Glowbug gamma-ray detection
  87. Fermi GRB 251127A: Global MASTER-Net observations report
  88. GRB 251127A: Fermi GBM Final Real-time Localization
  89. Fermi GRB 251125A: Global MASTER-Net observations report
  90. GRB 251124A: Fermi GBM Localization by automated pipeline
  91. GRB 251122A/EP251122A: 1.3m DFOT optical detection
  92. GRB 251115A: Fermi GBM Observation
  93. Fermi Gamma-ray Burst Monitor trigger 785388351 / 251121143 is not a GRB
  94. GRB 251018A: FRAM-Auger optical detection
  95. EP251118a: GOTO optical afterglow detection
  96. EP251118a: Global MASTER-Net observations report
  97. LAT GRB251118.86: Global MASTER-Net observations report
  98. EP251118a: NOT candidate optical counterpart
  99. SVOM GRB251116C: Global MASTER-Net observations report
  100. GRB 251115A: Fermi-LAT 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