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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"

3298 results found.

  1. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  2. GRB 260321A: EP-FXT follow-up observation
  3. The EP-WXT trigger 01709259045 is likely a flaring star
  4. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  5. EP260321a: GOTO detection of blue variable source
  6. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  7. EP260321a: further Kinder optical observations
  8. EP260321a: Las Cumbres upper limit
  9. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  10. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  11. EP260321a: SVOM/VT optical upper limit
  12. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  13. EP260321a: Global MASTER-Net observations report
  14. EP260321a: Einstein Probe detection of an X-ray transient
  15. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  16. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  17. The EP-WXT trigger 01709258989 is likely a flaring star
  18. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  19. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  20. EP260316a: COLIBRÍ faint optical counterpart candidate
  21. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  22. EP260316a: Xinglong optical upper limit
  23. EP260316a: optical upper limit with Kinder observations
  24. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  25. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  26. EP260314a: Xinglong optical upper limit
  27. EP260314a: optical upper limit with Kinder observations
  28. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  29. EP260314a: Global MASTER-Net observations report
  30. EP260314a: SVOM/VT optical candidate
  31. EP260314a: Einstein Probe detection of an X-ray transient
  32. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  33. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  34. GRB 260310A / AT 2026fgk: Location in the Epeak - Eiso diagram
  35. The EP-WXT trigger 01709258843 is not a real source
  36. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  37. EP260302a: SVOM/VT optical observation
  38. EP260306a: Gemini-North redshift z = 4.773
  39. EP260306a: SVOM/VT optical observation
  40. EP260302a: Gemini-South redshift z = 1.535
  41. EP260306a: Einstein Probe detection of an X-ray transient
  42. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  43. EP260302a: Optical afterglow rebrightening
  44. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  45. EP260214b: ATCA 6 GHz observations
  46. EP260302a: Global MASTER-Net observations report
  47. EP260302a: analysis of the follow-up EP-FXT observation
  48. EP260302a: LCO observations
  49. EP260302a: BOOTES-7 optical counterpart detection at early times
  50. GRB 260228A: EP-FXT follow-up observation
  51. EP260302a: Einstein Probe detection of an X-ray transient
  52. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  53. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  54. EP260227a: SVOM/VT optical observation
  55. EP260227A: 3.6m DOT optical afterglow detection
  56. EP260227a: FTW optical and NIR observations
  57. GRB 260225A: SVOM/VT optical continued observations and upper limit
  58. EP260227a: Global MASTER-Net observations report
  59. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  60. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  61. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  62. Konus-Wind detection of GRB 260226A
  63. EP260214a: VLT/FORS2 optical observations
  64. GRB 260225A: WINTER J-band upper limit
  65. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  66. The EP-WXT trigger 01709258652 is likely a flaring star
  67. EP260214a: VLA 6 GHz detection
  68. EP260224a: LCO optical upper limits
  69. GRB260225A: SVOM/ECLAIRs refined position
  70. GRB 260225A: EP-FXT follow-up observation
  71. EP260126a: VLA 6 GHz detection
  72. EP260223a: Liverpool Telescope upper limits
  73. EP260224a: Einstein Probe detection of an X-ray transient
  74. EP 260225.148: COLIBRÍ Confirmation of flaring star
  75. EP260223a: Xinglong optical upper limit
  76. The EP-WXT trigger 01709258631 is likely a flaring star
  77. EP260213a: Mephisto optical upper limits
  78. EP260223a: EP-FXT follow-up observation
  79. EP260223a: Einstein Probe detection of an X-ray transient
  80. EP260221a: Optical upper limit with Kinder observations
  81. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  82. EP260221a: COLIBRÍ optical counterpart candidate
  83. EP260221a: Gemini South z-band upper limit
  84. EP260221a: Global MASTER-Net observations report
  85. EP260221a: EP-FXT follow-up observation
  86. EP-WXT01709258519: Xinglong optical upper limit
  87. EP260221a: Xinglong optical upper limit
  88. EP260221a: GOTO optical upper limit
  89. EP260221a: COLIBRÍ optical upper limit
  90. EP260221a: Einstein Probe detection of an X-ray transient
  91. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  92. GRB 260214B/EP260214b: SVOM/ECLAIRs detection through targeted search
  93. The EP-WXT trigger 01709258455 is likely a flaring star
  94. EP-WXT 01709258455: NOT optical upper limits
  95. EP260214b: 1.3m DFOT optical upper limit
  96. EP260210a: Mondy optical upper limits
  97. Konus-Wind detection of GRB 260212A
  98. EP260214b: Liverpool Telescope optical observations
  99. EP260214b: Optical upper limit with Kinder observations
  100. EP260214a: Optical upper limits with Kinder observations

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