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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"

28057 results found.

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

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