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 260313A: Fermi GBM Final Real-time Localization
  2. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  3. Swift BAT trigger 1500287: A solar flare
  4. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  5. GRB 260308A: Insight-HXMT/HE detection
  6. GRB 260307A: CALET Gamma-Ray Burst Monitor detection
  7. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  8. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  9. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  10. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  11. GRB260310A / AT2026fgk: P200 Spectroscopy
  12. GRB 260312B: Glowbug gamma-ray detection
  13. GRB 260310A: Fermi GBM Observation
  14. GRB 260310A: potential optical counterpart
  15. Fermi GRB 260312B: Global MASTER-Net observations report
  16. Fermi GRB 260311B: Global MASTER-Net observations report
  17. Swift BAT trigger 1500148: A solar flare
  18. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  19. GRB 260312B: Fermi GBM Final Real-time Localization
  20. The EP-WXT trigger 01709258843 is not a real source
  21. GRB 260310B: GECAM-B observation of a burst
  22. Retraction of GCN 43965: GRB is actually solar flare
  23. GRB 260312A: Swift detection of a burst
  24. GRB 260311B: Fermi GBM Final Real-time Localization
  25. GRB 260131A/B: radio detection with the VLA
  26. EP260302a: MeerKAT radio counterpart
  27. GRB260307A: GECAM-B observation of a burst
  28. GRB 260308A: SVOM/GRM observation of a short GRB
  29. EP260306a: Mondy optical upper limit
  30. GRB 260310A: AstroSat CZTI detection of a long burst
  31. GRB 260311A: Fermi GBM Final Real-time Localization
  32. Fermi GRB 260310B: Global MASTER-Net observations report
  33. GRB 260310B: Fermi GBM Final Real-time Localization
  34. Fermi GRB 260310A: Global MASTER-Net observations report
  35. GRB 260307B: SVOM/ECLAIRs refined analysis
  36. GRB 260208A: radio detection with the VLA
  37. GRB 260310A: Fermi GBM Final Real-time Localization
  38. GRB 260307A: Glowbug gamma-ray detection
  39. GRB 260308A: Fermi GBM Final Real-time Localization
  40. Fermi GBM Sub-Threshold Detection of GRB 260307B
  41. GRB 260307B: Mephisto optical upper limits
  42. GRB 260307B: possible NOT optical counterpart
  43. GRB 260307B: SVOM/VT upper limit with X band data analysis
  44. Fermi GRB 260307A: Global MASTER-Net observations report
  45. GRB260307B: GROWTH-India Telescope optical upper limit
  46. GRB 260307B: SVOM/VT optical candidate
  47. GRB 260307B: SVOM/C-GFT upper limit
  48. GRB 260307B: SVOM detection of a burst
  49. GRB 260307A: Fermi GBM Final Localization
  50. GRB 260211A: late-time NOT i-band observations consistent with archival flux
  51. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  52. GRB 260207A: TESS Detection and Possible VLA Counterpart
  53. EP260302a: SVOM/VT optical observation
  54. EP260306a: Gemini-North redshift z = 4.773
  55. EP260306a: SVOM/VT optical observation
  56. EP260302a: Gemini-South redshift z = 1.535
  57. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  58. EP260306a: Einstein Probe detection of an X-ray transient
  59. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  60. EP260302a: Optical afterglow rebrightening
  61. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  62. GRB 260303A: 1.3m DFOT optical upper limit (duplicate submission)
  63. GRB 260303A: 1.3m DFOT optical upper limit
  64. EP260214b: ATCA 6 GHz observations
  65. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  66. GRB 260303A: SVOM/ECLAIRs refined analysis
  67. Fermi GRB 260305A: Global MASTER-Net observations report
  68. GRB 260305A: Fermi GBM Final Real-time Localization
  69. GRB 260303B: AstroSat CZTI detection
  70. GRB 260304A: AstroSat CZTI detection of a long burst
  71. SVOM/sb26030408: SVOM detection of an X-ray transient likely associated with Beta Persei
  72. GRB 260303A: SVOM/VT optical observations
  73. GRB 260303A: J-band observations with WINTER
  74. GRB 260303B: NuSTAR detection of prompt emission
  75. EP260302a: Global MASTER-Net observations report
  76. Fermi GRB 260303B: Global MASTER-Net observations report
  77. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  78. GRB 260228A: SVOM/ECLAIRs refined analysis
  79. GRB 260225A: SVOM/ECLAIRs refined analysis
  80. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  81. GRB 260303B: Fermi GBM Final Real-time Localization
  82. EP260302a: analysis of the follow-up EP-FXT observation
  83. EP260227a: Gemini-South optical observations
  84. EP260302a: LCO observations
  85. EP260302a: BOOTES-7 optical counterpart detection at early times
  86. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  87. GRB 260303A: SVOM detection of a burst
  88. GRB 260228A: EP-FXT follow-up observation
  89. EP260302a: Einstein Probe detection of an X-ray transient
  90. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  91. GRB 251130B: TERI Gamma-ray detection
  92. GRB 260208A: TERI Gamma-ray detection
  93. GRB 260302A: Fermi GBM Final Real-time Localization
  94. EP260227a: Mondy optical observations
  95. GRB 260228A: CAHA 2.2m telescope optical upper limit
  96. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. EP260227a: Mephisto optical detection
  98. GRID detection of GRB 260225D
  99. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  100. EP260227a: further LCO 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