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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"

18333 results found.

  1. The EP-WXT trigger 01709258989 is likely a flaring star
  2. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  3. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  4. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  5. GRB 260310A / AT 2026fgk: radio detection with the VLA
  6. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  7. GRB 260310A / AT2026fgk: LCO optical observations
  8. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  9. GRB 260316B: SVOM/GRM observation
  10. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  11. EP260316a: COLIBRÍ faint optical counterpart candidate
  12. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  13. EP260316a: Xinglong optical upper limit
  14. EP260316a: optical upper limit with Kinder observations
  15. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  16. IceCube-260315A: COLIBRÍ optical observations
  17. EP260314a: Xinglong optical upper limit
  18. EP260314a: optical upper limit with Kinder observations
  19. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  20. GRB 260310A / AT 2026fgk: iTelescope optical observations
  21. EP260314a: COLIBRÍ optical upper limit
  22. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  23. EP260314a: SVOM/VT optical candidate
  24. EP260314a: Einstein Probe detection of an X-ray transient
  25. GRB 260310A / AT2026fgk: SAO RAS optical observations
  26. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  27. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  28. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  29. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  30. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  31. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  32. GRB 260310A: potential optical counterpart
  33. GRB 260131A/B: radio detection with the VLA
  34. EP260302a: MeerKAT radio counterpart
  35. GRB 260308A: SVOM/GRM observation of a short GRB
  36. EP260306a: Mondy optical upper limit
  37. GRB 260208A: radio detection with the VLA
  38. GRB 260307B: Mephisto optical upper limits
  39. GRB 260307B: possible NOT optical counterpart
  40. GRB 260307B: SVOM/VT upper limit with X band data analysis
  41. GRB260307B: GROWTH-India Telescope optical upper limit
  42. GRB 260307B: SVOM/VT optical candidate
  43. GRB 260307B: SVOM/C-GFT upper limit
  44. GRB 260307B: SVOM detection of a burst
  45. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  46. GRB 260207A: TESS Detection and Possible VLA Counterpart
  47. EP260302a: SVOM/VT optical observation
  48. EP260306a: SVOM/VT optical observation
  49. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  50. EP260306a: Einstein Probe detection of an X-ray transient
  51. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  52. GRB 260303A: 1.3m DFOT optical upper limit
  53. GRB 260304A: AstroSat CZTI detection of a long burst
  54. GRB 260303A: SVOM/VT optical observations
  55. GRB 260303A: J-band observations with WINTER
  56. EP260302a: analysis of the follow-up EP-FXT observation
  57. EP260302a: LCO observations
  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. EP260227a: Mondy optical observations
  63. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. EP260227a: Mephisto optical detection
  65. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  66. EP260227a: SVOM/VT optical observation
  67. GRB 260228A: SVOM/VT optical upper limits
  68. GRB 260225D: SVOM/GRM observation
  69. EP260227A: 3.6m DOT optical afterglow detection
  70. GRB 260225B: SVOM/GRM observation
  71. EP260227a: Liverpool Telescope optical observations
  72. EP260227a: LCOGT Optical Observations
  73. GRB 260226A: Asiago r-band upper limit
  74. EP260227a: Liverpool Telescope observations
  75. EP260227a: COLIBRÍ optical observations
  76. EP260227a: NOT optical observations
  77. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  78. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  79. Konus-Wind detection of GRB 260226A
  80. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  81. EP260214a: VLT/FORS2 optical observations
  82. GRB 260225A: WINTER J-band upper limit
  83. GRB 260226A: COLIBRÍ optical upper limits
  84. GRB 260226A: LCOGT Optical Upper Limit
  85. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  86. GRB 260226A : GROWTH-India Telescope optical observations
  87. GRB 260226A: LAST optical upper limit
  88. The EP-WXT trigger 01709258652 is likely a flaring star
  89. EP260224a: LCO optical upper limits
  90. GRB 260225A: EP-FXT follow-up observation
  91. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  92. GRB 260225A: SVOM/VT optical upper limits
  93. EP260223a: Liverpool Telescope upper limits
  94. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  95. EP260224a: Einstein Probe detection of an X-ray transient
  96. EP 260225.148: COLIBRÍ Confirmation of flaring star
  97. EP260223a: Xinglong optical upper limit
  98. The EP-WXT trigger 01709258631 is likely a flaring star
  99. EP260213a: Mephisto optical upper limits
  100. EP260223a: EP-FXT follow-up observation

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