Skip to main content
Retirement of GCN Classic VOEvent Brokers. 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. GRB260310A / AT2026fgk: P200 Spectroscopy
  2. GRB 260312B: Glowbug gamma-ray detection
  3. GRB 260310A: Fermi GBM Observation
  4. GRB 260310A: potential optical counterpart
  5. Fermi GRB 260312B: Global MASTER-Net observations report
  6. Fermi GRB 260311B: Global MASTER-Net observations report
  7. Swift BAT trigger 1500148: A solar flare
  8. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  9. GRB 260312B: Fermi GBM Final Real-time Localization
  10. The EP-WXT trigger 01709258843 is not a real source
  11. GRB 260310B: GECAM-B observation of a burst
  12. Retraction of GCN 43965: GRB is actually solar flare
  13. GRB 260312A: Swift detection of a burst
  14. GRB 260311B: Fermi GBM Final Real-time Localization
  15. GRB 260131A/B: radio detection with the VLA
  16. EP260302a: MeerKAT radio counterpart
  17. GRB260307A: GECAM-B observation of a burst
  18. GRB 260308A: SVOM/GRM observation of a short GRB
  19. EP260306a: Mondy optical upper limit
  20. GRB 260310A: AstroSat CZTI detection of a long burst
  21. GRB 260311A: Fermi GBM Final Real-time Localization
  22. Fermi GRB 260310B: Global MASTER-Net observations report
  23. GRB 260310B: Fermi GBM Final Real-time Localization
  24. Fermi GRB 260310A: Global MASTER-Net observations report
  25. GRB 260307B: SVOM/ECLAIRs refined analysis
  26. GRB 260208A: radio detection with the VLA
  27. GRB 260310A: Fermi GBM Final Real-time Localization
  28. GRB 260307A: Glowbug gamma-ray detection
  29. GRB 260308A: Fermi GBM Final Real-time Localization
  30. Fermi GBM Sub-Threshold Detection of GRB 260307B
  31. GRB 260307B: Mephisto optical upper limits
  32. GRB 260307B: possible NOT optical counterpart
  33. GRB 260307B: SVOM/VT upper limit with X band data analysis
  34. Fermi GRB 260307A: Global MASTER-Net observations report
  35. GRB260307B: GROWTH-India Telescope optical upper limit
  36. GRB 260307B: SVOM/VT optical candidate
  37. GRB 260307B: SVOM/C-GFT upper limit
  38. GRB 260307B: SVOM detection of a burst
  39. GRB 260307A: Fermi GBM Final Localization
  40. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  41. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  42. GRB 260207A: TESS Detection and Possible VLA Counterpart
  43. EP260302a: SVOM/VT optical observation
  44. EP260306a: Gemini-North redshift z = 4.773
  45. EP260306a: SVOM/VT optical observation
  46. EP260302a: Gemini-South redshift z = 1.535
  47. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  48. EP260306a: Einstein Probe detection of an X-ray transient
  49. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  50. EP260302a: Optical afterglow rebrightening
  51. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  52. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  53. GRB 260303A: 1.3m DFOT optical upper limit
  54. EP260214b: ATCA 6 GHz observations
  55. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  56. GRB 260303A: SVOM/ECLAIRs refined analysis
  57. Fermi GRB 260305A: Global MASTER-Net observations report
  58. GRB 260305A: Fermi GBM Final Real-time Localization
  59. GRB 260303B: AstroSat CZTI detection
  60. GRB 260304A: AstroSat CZTI detection of a long burst
  61. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  62. GRB 260303A: SVOM/VT optical observations
  63. GRB 260303A: J-band observations with WINTER
  64. GRB 260303B: NuSTAR detection of prompt emission
  65. EP260302a: Global MASTER-Net observations report
  66. Fermi GRB 260303B: Global MASTER-Net observations report
  67. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  68. GRB 260228A: SVOM/ECLAIRs refined analysis
  69. GRB 260225A: SVOM/ECLAIRs refined analysis
  70. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  71. GRB 260303B: Fermi GBM Final Real-time Localization
  72. EP260302a: analysis of the follow-up EP-FXT observation
  73. EP260227a: Gemini-South optical observations
  74. EP260302a: LCO observations
  75. EP260302a: BOOTES-7 optical counterpart detection at early times
  76. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  77. GRB 260303A: SVOM detection of a burst
  78. GRB 260228A: EP-FXT follow-up observation
  79. EP260302a: Einstein Probe detection of an X-ray transient
  80. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  81. GRB 251130B: TERI Gamma-ray detection
  82. GRB 260208A: TERI Gamma-ray detection
  83. GRB 260302A: Fermi GBM Final Real-time Localization
  84. EP260227a: Mondy optical observations
  85. GRB 260228A: CAHA 2.2m telescope optical upper limit
  86. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. EP260227a: Mephisto optical detection
  88. GRID detection of GRB 260225D
  89. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  90. EP260227a: further LCO observations
  91. EP260227a: SVOM/VT optical observation
  92. GRB 260228A: SVOM/VT optical upper limits
  93. GRB 260225D: SVOM/GRM observation
  94. EP260227A: 3.6m DOT optical afterglow detection
  95. GRB 260225B: SVOM/GRM observation
  96. GRB 260228A: SVOM detection of a burst
  97. EP260227a: FTW optical and NIR observations
  98. EP260227a: Liverpool Telescope optical observations
  99. EP260227a: LCOGT Optical Observations
  100. GRB 260226A: Asiago r-band upper limit

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