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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"

28058 results found.

  1. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  2. GRB 260314A: Glowbug gamma-ray detection
  3. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  4. IceCube-260315A: COLIBRÍ optical observations
  5. EP260314a: Xinglong optical upper limit
  6. EP260314a: optical upper limit with Kinder observations
  7. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  8. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  9. GRB 260310A / AT 2026fgk: iTelescope optical observations
  10. EP260314a: COLIBRÍ optical upper limit
  11. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  12. EP260314a: Global MASTER-Net observations report
  13. EP260314a: SVOM/VT optical candidate
  14. Fermi trigger No 795185313: Global MASTER-Net observations report
  15. IceCube Alert 260315A: Global MASTER-Net observations report
  16. EP260314a: Einstein Probe detection of an X-ray transient
  17. GRB 260310A / AT2026fgk: SAO RAS optical observations
  18. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  19. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  20. Fermi GRB 260314A: Global MASTER-Net observations report
  21. Fermi GRB 260313A: Global MASTER-Net observations report
  22. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  23. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  24. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  25. GRB 260312B: AstroSat CZTI detection
  26. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  27. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  28. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  29. GRB 260312B: Glowbug gamma-ray detection
  30. GRB 260310A: Fermi GBM Observation
  31. GRB 260310A: potential optical counterpart
  32. Fermi GRB 260312B: Global MASTER-Net observations report
  33. Fermi GRB 260311B: Global MASTER-Net observations report
  34. GRB 260312B: BALROG localization (Fermi Trigger 795001611 / GRB 260312407)
  35. GRB 260131A/B: radio detection with the VLA
  36. EP260302a: MeerKAT radio counterpart
  37. GRB 260308A: SVOM/GRM observation of a short GRB
  38. EP260306a: Mondy optical upper limit
  39. Fermi GRB 260310B: Global MASTER-Net observations report
  40. Fermi GRB 260310A: Global MASTER-Net observations report
  41. GRB 260208A: radio detection with the VLA
  42. GRB 260307A: Glowbug gamma-ray detection
  43. Fermi GBM Sub-Threshold Detection of GRB 260307B
  44. GRB 260307B: Mephisto optical upper limits
  45. GRB 260307B: possible NOT optical counterpart
  46. GRB 260307B: SVOM/VT upper limit with X band data analysis
  47. Fermi GRB 260307A: Global MASTER-Net observations report
  48. GRB260307B: GROWTH-India Telescope optical upper limit
  49. GRB 260307B: SVOM/VT optical candidate
  50. GRB 260307B: SVOM/C-GFT upper limit
  51. GRB 260307B: SVOM detection of a burst
  52. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  53. GRB 260207A: TESS Detection and Possible VLA Counterpart
  54. EP260302a: SVOM/VT optical observation
  55. EP260306a: Gemini-North redshift z = 4.773
  56. EP260306a: SVOM/VT optical observation
  57. EP260302a: Gemini-South redshift z = 1.535
  58. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  59. EP260306a: Einstein Probe detection of an X-ray transient
  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
  63. Fermi GRB 260305A: Global MASTER-Net observations report
  64. GRB 260303B: AstroSat CZTI detection
  65. GRB 260303A: SVOM/VT optical observations
  66. GRB 260303A: J-band observations with WINTER
  67. GRB 260303B: NuSTAR detection of prompt emission
  68. EP260302a: Global MASTER-Net observations report
  69. Fermi GRB 260303B: Global MASTER-Net observations report
  70. GRB 260303B: BALROG localization (Fermi Trigger 794237065 / GRB 260303559)
  71. EP260302a: analysis of the follow-up EP-FXT observation
  72. EP260302a: LCO observations
  73. EP260302a: BOOTES-7 optical counterpart detection at early times
  74. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  75. GRB 260303A: SVOM detection of a burst
  76. GRB 260228A: EP-FXT follow-up observation
  77. EP260302a: Einstein Probe detection of an X-ray transient
  78. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  79. GRB 251130B: TERI Gamma-ray detection
  80. GRB 260208A: TERI Gamma-ray detection
  81. EP260227a: Mondy optical observations
  82. GRB 260228A: CAHA 2.2m telescope optical upper limit
  83. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  84. EP260227a: Mephisto optical detection
  85. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  86. EP260227a: SVOM/VT optical observation
  87. GRB 260228A: SVOM/VT optical upper limits
  88. GRB 260225D: SVOM/GRM observation
  89. EP260227A: 3.6m DOT optical afterglow detection
  90. GRB 260225B: SVOM/GRM observation
  91. EP260227a: Liverpool Telescope optical observations
  92. EP260227a: LCOGT Optical Observations
  93. GRB 260226A: Asiago r-band upper limit
  94. EP260227a: Liverpool Telescope observations
  95. EP260227a: COLIBRÍ optical observations
  96. EP260227a: NOT optical observations
  97. EP260227a: Global MASTER-Net observations report
  98. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  99. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  100. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow

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