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"

26940 results found.

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

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