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"

27148 results found.

  1. GRB 260310A / AT 2026fgk: iTelescope optical observations
  2. EP260314a: COLIBRÍ optical upper limit
  3. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  4. EP260314a: Global MASTER-Net observations report
  5. EP260314a: SVOM/VT optical candidate
  6. Fermi trigger No 795185313: Global MASTER-Net observations report
  7. IceCube Alert 260315A: Global MASTER-Net observations report
  8. EP260314a: Einstein Probe detection of an X-ray transient
  9. GRB 260310A / AT2026fgk: SAO RAS optical observations
  10. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  11. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  12. Fermi GRB 260314A: Global MASTER-Net observations report
  13. Fermi GRB 260313A: Global MASTER-Net observations report
  14. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  15. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  16. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  17. GRB 260312B: AstroSat CZTI detection
  18. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  19. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  20. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  21. GRB 260312B: Glowbug gamma-ray detection
  22. GRB 260310A: Fermi GBM Observation
  23. GRB 260310A: potential optical counterpart
  24. Fermi GRB 260312B: Global MASTER-Net observations report
  25. Fermi GRB 260311B: Global MASTER-Net observations report
  26. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  27. GRB 260131A/B: radio detection with the VLA
  28. EP260302a: MeerKAT radio counterpart
  29. GRB 260308A: SVOM/GRM observation of a short GRB
  30. EP260306a: Mondy optical upper limit
  31. Fermi GRB 260310B: Global MASTER-Net observations report
  32. Fermi GRB 260310A: Global MASTER-Net observations report
  33. GRB 260208A: radio detection with the VLA
  34. GRB 260307A: Glowbug gamma-ray detection
  35. Fermi GBM Sub-Threshold Detection of GRB 260307B
  36. GRB 260307B: Mephisto optical upper limits
  37. GRB 260307B: possible NOT optical counterpart
  38. GRB 260307B: SVOM/VT upper limit with X band data analysis
  39. Fermi GRB 260307A: Global MASTER-Net observations report
  40. GRB260307B: GROWTH-India Telescope optical upper limit
  41. GRB 260307B: SVOM/VT optical candidate
  42. GRB 260307B: SVOM/C-GFT upper limit
  43. GRB 260307B: SVOM detection of a burst
  44. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  45. GRB 260207A: TESS Detection and Possible VLA Counterpart
  46. EP260302a: SVOM/VT optical observation
  47. EP260306a: Gemini-North redshift z = 4.773
  48. EP260306a: SVOM/VT optical observation
  49. EP260302a: Gemini-South redshift z = 1.535
  50. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  51. EP260306a: Einstein Probe detection of an X-ray transient
  52. EP260302a: Optical afterglow rebrightening
  53. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  54. GRB 260303A: 1.3m DFOT optical upper limit
  55. Fermi GRB 260305A: Global MASTER-Net observations report
  56. GRB 260303B: AstroSat CZTI detection
  57. GRB 260303A: SVOM/VT optical observations
  58. GRB 260303A: J-band observations with WINTER
  59. GRB 260303B: NuSTAR detection of prompt emission
  60. EP260302a: Global MASTER-Net observations report
  61. Fermi GRB 260303B: Global MASTER-Net observations report
  62. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  63. EP260302a: analysis of the follow-up EP-FXT observation
  64. EP260302a: LCO observations
  65. EP260302a: BOOTES-7 optical counterpart detection at early times
  66. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  67. GRB 260303A: SVOM detection of a burst
  68. GRB 260228A: EP-FXT follow-up observation
  69. EP260302a: Einstein Probe detection of an X-ray transient
  70. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  71. GRB 251130B: TERI Gamma-ray detection
  72. GRB 260208A: TERI Gamma-ray detection
  73. EP260227a: Mondy optical observations
  74. GRB 260228A: CAHA 2.2m telescope optical upper limit
  75. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. EP260227a: Mephisto optical detection
  77. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  78. EP260227a: SVOM/VT optical observation
  79. GRB 260228A: SVOM/VT optical upper limits
  80. GRB 260225D: SVOM/GRM observation
  81. EP260227A: 3.6m DOT optical afterglow detection
  82. GRB 260225B: SVOM/GRM observation
  83. EP260227a: Liverpool Telescope optical observations
  84. EP260227a: LCOGT Optical Observations
  85. GRB 260226A: Asiago r-band upper limit
  86. EP260227a: Liverpool Telescope observations
  87. EP260227a: COLIBRÍ optical observations
  88. EP260227a: NOT optical observations
  89. EP260227a: Global MASTER-Net observations report
  90. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  91. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  92. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  93. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  94. EP260214a: VLT/FORS2 optical observations
  95. GRB 260225A: WINTER J-band upper limit
  96. GRB 260226A: COLIBRÍ optical upper limits
  97. GRB 260226A: LCOGT Optical Upper Limit
  98. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  99. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  100. GRB 260226A: Glowbug gamma-ray 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