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"

28041 results found.

  1. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  2. Fermi GRB 260314A: Global MASTER-Net observations report
  3. Fermi GRB 260313A: Global MASTER-Net observations report
  4. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  5. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  6. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  7. GRB 260312B: AstroSat CZTI detection
  8. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  9. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  10. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  11. GRB 260312B: Glowbug gamma-ray detection
  12. GRB 260310A: Fermi GBM Observation
  13. GRB 260310A: potential optical counterpart
  14. Fermi GRB 260312B: Global MASTER-Net observations report
  15. Fermi GRB 260311B: Global MASTER-Net observations report
  16. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  17. GRB 260131A/B: radio detection with the VLA
  18. EP260302a: MeerKAT radio counterpart
  19. GRB 260308A: SVOM/GRM observation of a short GRB
  20. EP260306a: Mondy optical upper limit
  21. Fermi GRB 260310B: Global MASTER-Net observations report
  22. Fermi GRB 260310A: Global MASTER-Net observations report
  23. GRB 260208A: radio detection with the VLA
  24. GRB 260307A: Glowbug gamma-ray detection
  25. Fermi GBM Sub-Threshold Detection of GRB 260307B
  26. GRB 260307B: Mephisto optical upper limits
  27. GRB 260307B: possible NOT optical counterpart
  28. GRB 260307B: SVOM/VT upper limit with X band data analysis
  29. Fermi GRB 260307A: Global MASTER-Net observations report
  30. GRB260307B: GROWTH-India Telescope optical upper limit
  31. GRB 260307B: SVOM/VT optical candidate
  32. GRB 260307B: SVOM/C-GFT upper limit
  33. GRB 260307B: SVOM detection of a burst
  34. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  35. GRB 260207A: TESS Detection and Possible VLA Counterpart
  36. EP260302a: SVOM/VT optical observation
  37. EP260306a: Gemini-North redshift z = 4.773
  38. EP260306a: SVOM/VT optical observation
  39. EP260302a: Gemini-South redshift z = 1.535
  40. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  41. EP260306a: Einstein Probe detection of an X-ray transient
  42. EP260302a: Optical afterglow rebrightening
  43. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  44. GRB 260303A: 1.3m DFOT optical upper limit
  45. Fermi GRB 260305A: Global MASTER-Net observations report
  46. GRB 260303B: AstroSat CZTI detection
  47. GRB 260303A: SVOM/VT optical observations
  48. GRB 260303A: J-band observations with WINTER
  49. GRB 260303B: NuSTAR detection of prompt emission
  50. EP260302a: Global MASTER-Net observations report
  51. Fermi GRB 260303B: Global MASTER-Net observations report
  52. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  53. EP260302a: analysis of the follow-up EP-FXT observation
  54. EP260302a: LCO observations
  55. EP260302a: BOOTES-7 optical counterpart detection at early times
  56. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  57. GRB 260303A: SVOM detection of a burst
  58. GRB 260228A: EP-FXT follow-up observation
  59. EP260302a: Einstein Probe detection of an X-ray transient
  60. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  61. GRB 251130B: TERI Gamma-ray detection
  62. GRB 260208A: TERI Gamma-ray detection
  63. EP260227a: Mondy optical observations
  64. GRB 260228A: CAHA 2.2m telescope optical upper limit
  65. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  66. EP260227a: Mephisto optical detection
  67. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  68. EP260227a: SVOM/VT optical observation
  69. GRB 260228A: SVOM/VT optical upper limits
  70. GRB 260225D: SVOM/GRM observation
  71. EP260227A: 3.6m DOT optical afterglow detection
  72. GRB 260225B: SVOM/GRM observation
  73. EP260227a: Liverpool Telescope optical observations
  74. EP260227a: LCOGT Optical Observations
  75. GRB 260226A: Asiago r-band upper limit
  76. EP260227a: Liverpool Telescope observations
  77. EP260227a: COLIBRÍ optical observations
  78. EP260227a: NOT optical observations
  79. EP260227a: Global MASTER-Net observations report
  80. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  81. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  82. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  83. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  84. EP260214a: VLT/FORS2 optical observations
  85. GRB 260225A: WINTER J-band upper limit
  86. GRB 260226A: COLIBRÍ optical upper limits
  87. GRB 260226A: LCOGT Optical Upper Limit
  88. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  89. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  90. GRB 260226A: Glowbug gamma-ray detection
  91. GRB 260226A: NuSTAR detection of bright prompt emission
  92. GRB 260226A : GROWTH-India Telescope optical observations
  93. GRB 260226A: LAST optical upper limit
  94. GRB 260226A: Fermi GBM observation
  95. LAT GRB260226.44: Global MASTER-Net observations report
  96. Fermi GRB 260226A: Global MASTER-Net observations report
  97. GRB 260226A: AstroSat CZTI detection of bright long burst
  98. GRB 260226A???: BALROG localization (Fermi Trigger 793795080 / GRB 260226443)
  99. EP260224a: LCO optical upper limits
  100. GRB 260225A: EP-FXT follow-up observation

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