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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"

3311 results found.

  1. EP260327a: Gemini-North optical upper limits
  2. EP260327a: Global MASTER-Net observations report
  3. EP260327a: Einstein Probe detection of an X-ray transient
  4. The EP-WXT trigger 01709259173 is likely a flaring star
  5. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  6. EP260321a: Gemini-South confirmation of a supernova
  7. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  8. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  9. The EP-WXT trigger 01709259112 is likely a flaring star
  10. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  11. EP260321a: COLIBRÍ further optical observations and brightening
  12. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  13. EP260214b: ATCA 6 GHz detection
  14. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  15. GRB 260321A: EP-FXT follow-up observation
  16. The EP-WXT trigger 01709259045 is likely a flaring star
  17. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  18. EP260321a: GOTO detection of blue variable source
  19. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  20. EP260321a: further Kinder optical observations
  21. EP260321a: Las Cumbres upper limit
  22. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  23. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  24. EP260321a: SVOM/VT optical upper limit
  25. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  26. EP260321a: Global MASTER-Net observations report
  27. EP260321a: Einstein Probe detection of an X-ray transient
  28. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  29. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  30. The EP-WXT trigger 01709258989 is likely a flaring star
  31. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  32. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  33. EP260316a: COLIBRÍ faint optical counterpart candidate
  34. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  35. EP260316a: Xinglong optical upper limit
  36. EP260316a: optical upper limit with Kinder observations
  37. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  38. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  39. EP260314a: Xinglong optical upper limit
  40. EP260314a: optical upper limit with Kinder observations
  41. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  42. EP260314a: Global MASTER-Net observations report
  43. EP260314a: SVOM/VT optical candidate
  44. EP260314a: Einstein Probe detection of an X-ray transient
  45. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  46. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  47. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  48. The EP-WXT trigger 01709258843 is not a real source
  49. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  50. EP260302a: SVOM/VT optical observation
  51. EP260306a: Gemini-North redshift z = 4.773
  52. EP260306a: SVOM/VT optical observation
  53. EP260302a: Gemini-South redshift z = 1.535
  54. EP260306a: Einstein Probe detection of an X-ray transient
  55. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  56. EP260302a: Optical afterglow rebrightening
  57. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  58. EP260214b: ATCA 6 GHz observations
  59. EP260302a: Global MASTER-Net observations report
  60. EP260302a: analysis of the follow-up EP-FXT observation
  61. EP260302a: LCO observations
  62. EP260302a: BOOTES-7 optical counterpart detection at early times
  63. GRB 260228A: EP-FXT follow-up observation
  64. EP260302a: Einstein Probe detection of an X-ray transient
  65. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  66. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  67. EP260227a: SVOM/VT optical observation
  68. EP260227A: 3.6m DOT optical afterglow detection
  69. EP260227a: FTW optical and NIR observations
  70. GRB 260225A: SVOM/VT optical continued observations and upper limit
  71. EP260227a: Global MASTER-Net observations report
  72. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  73. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  74. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  75. Konus-Wind detection of GRB 260226A
  76. EP260214a: VLT/FORS2 optical observations
  77. GRB 260225A: WINTER J-band upper limit
  78. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  79. The EP-WXT trigger 01709258652 is likely a flaring star
  80. EP260214a: VLA 6 GHz detection
  81. EP260224a: LCO optical upper limits
  82. GRB260225A: SVOM/ECLAIRs refined position
  83. GRB 260225A: EP-FXT follow-up observation
  84. EP260126a: VLA 6 GHz detection
  85. EP260223a: Liverpool Telescope upper limits
  86. EP260224a: Einstein Probe detection of an X-ray transient
  87. EP 260225.148: COLIBRÍ Confirmation of flaring star
  88. EP260223a: Xinglong optical upper limit
  89. The EP-WXT trigger 01709258631 is likely a flaring star
  90. EP260213a: Mephisto optical upper limits
  91. EP260223a: EP-FXT follow-up observation
  92. EP260223a: Einstein Probe detection of an X-ray transient
  93. EP260221a: Optical upper limit with Kinder observations
  94. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  95. EP260221a: COLIBRÍ optical counterpart candidate
  96. EP260221a: Gemini South z-band upper limit
  97. EP260221a: Global MASTER-Net observations report
  98. EP260221a: EP-FXT follow-up observation
  99. EP-WXT01709258519: Xinglong optical upper limit
  100. EP260221a: Xinglong optical upper limit

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