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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"

1094 results found.

  1. EP260302a: BOOTES-7 optical counterpart detection at early times
  2. GRB 260228A: EP-FXT follow-up observation
  3. EP260302a: Einstein Probe detection of an X-ray transient
  4. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  5. EP260227A: 3.6m DOT optical afterglow detection
  6. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  7. The EP-WXT trigger 01709258681 (EP260227a?): Las Cumbres follow-up observation of the optical counterpart
  8. The EP-WXT trigger 01709258652 is likely a flaring star
  9. EP260214a: VLA 6 GHz detection
  10. GRB 260225A: EP-FXT follow-up observation
  11. EP260126a: VLA 6 GHz detection
  12. EP260224a: Einstein Probe detection of an X-ray transient
  13. The EP-WXT trigger 01709258631 is likely a flaring star
  14. EP260223a: EP-FXT follow-up observation
  15. EP260223a: Einstein Probe detection of an X-ray transient
  16. EP260221a: Optical upper limit with Kinder observations
  17. EP260221a: EP-FXT follow-up observation
  18. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  19. EP260221a: Einstein Probe detection of an X-ray transient
  20. The EP-WXT trigger 01709258519 is likely caused by Mrk 421
  21. The EP-WXT trigger 01709258455 is likely a flaring star
  22. EP-WXT 01709258455: NOT optical upper limits
  23. EP260214b: Optical upper limit with Kinder observations
  24. EP260214a: Optical upper limits with Kinder observations
  25. EP260214b: EP-FXT follow-up observation
  26. EP260214b: GROWTH-India Telescope optical upper limit
  27. EP260214b: SVOM/VT optical observation
  28. EP260214a: refined analysis of the EP-FXT observation
  29. EP260214a: SVOM/VT optical upper limits
  30. EP260214b: Einstein Probe detection of a fast X-ray transient
  31. EP260214a: Einstein Probe detection of an X-ray transient
  32. EP260213a: Optical upper limits with Kinder observations
  33. EP260213a: SVOM/VT optical upper limit
  34. EP260213a: refined analysis of the EP-FXT observation
  35. EP260213a: Einstein Probe detection of a fast X-ray transient
  36. GRB 260211A: EP-FXT follow-up observation
  37. EP260210a: refined analysis of the EP-FXT observation
  38. EP260209a: Einstein Probe detection of a fast X-ray transient
  39. EP260210a: Optical upper limits with Kinder observations
  40. EP260210a: SVOM/VT optical upper limit
  41. GRB 260208B: refined analysis of the EP-FXT observation
  42. EP260210a: Einstein Probe detection of an X-ray transient
  43. GRB 260208B: EP-FXT observation
  44. Konus-Wind detection of GRB 260128A / EP260128a
  45. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  46. EP260131a: Las Cumbres detection of an optical counterpart
  47. EP260131a: Einstein Probe detection of an X-ray transient
  48. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  49. EP260128a: Einstein Probe detection of an X-ray transient
  50. EP260126a: Seimei/TriCCS optical upper limit
  51. The EP-WXT trigger 01709253145 is likely a flaring star
  52. EP260126a: EP-FXT follow-up observation
  53. EP260126a: Optical upper limit with Kinder observations
  54. EP260126a: Einstein Probe detection of a fast X-ray transient
  55. The EP-WXT trigger 01709251871 is likely a flaring star
  56. GRB 251202A: further radio observations with the VLA
  57. EP260119A: GTC/OSIRIS+ spectroscopic redshift z = 5.47
  58. EP260119a: update of EP-FXT follow-up observation
  59. EP260119a: preliminary result from the EP-FXT observation
  60. EP260119a: EP-WXT detection of a fast X-ray transient
  61. EP260116a: Einstein Probe detection of an X-ray transient
  62. GRB 251222A: radio detection with the VLA
  63. Konus-Wind detection of GRB 251230A / EP251230a
  64. EP260110a: TRT optical upper limits
  65. The EP-WXT trigger 01709251266 is likely a flaring star
  66. EP260110a: refined analysis of the EP-WXT and EP-FXT observations
  67. EP260110a: Einstein Probe detection of an X-ray transient
  68. EP260105b/EP-WXT trigger 01709251028: Einstein Probe detection of an X-ray transient
  69. The EP-WXT trigger 01709251112 is likely a flaring star
  70. The EP-WXT trigger 01709251028 is likely a flaring star
  71. EP260105a: refined analysis of the EP-WXT and EP-FXT observations
  72. EP260104a: Einstein Probe detection of a fast X-ray transient
  73. EP260105a: Einstein Probe detection of an X-ray transient
  74. GRB 260102A: EP-FXT follow-up observation
  75. EP260101a: refined analysis of the EP-WXT and EP-FXT observations
  76. EP260101a: Einstein Probe detection of an X-ray transient
  77. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  78. EP251229a: Optical upper limit with Kinder observations
  79. EP251230a / GRB 251230A: refined analysis of the EP-WXT and EP-FXT observations
  80. EP251229a: BOOTES-2 early optical upper limit
  81. GRB 251230A: GOTO optical upper limit
  82. EP251229a: refined analysis of the EP-WXT and EP-FXT observations
  83. EP251230a / GRB 251230A: Einstein Probe detection of an X-ray transient
  84. The EP-WXT trigger 01709250693/GRB 251230A: Las Cumbres detection of the optical counterpart
  85. EP251229a: Einstein Probe detection of an X-ray transient
  86. The EP-WXT trigger 01709250662 is likely a flaring star
  87. The EP-WXT trigger 01709250617 is likely a flaring star
  88. GRB 251222A/EP251222b: Optical detection with Kinder observations
  89. EP251222a: Optical upper limit with Kinder observations
  90. GRB 251222A / EP251222b: Kilonova-Catcher optical afterglow detection
  91. GRB 251129A / EP251129a: VLA detection of a radio counterpart
  92. EP251221a: PRIME upper limit
  93. GRB 251222A / EP251222b: GECAM-B observation
  94. EP251222a: refined analysis of the EP-WXT and EP-FXT observations
  95. EP251222b/GRB 251222A: refined analysis of the EP-WXT and EP-FXT observations
  96. Konus-Wind detection of GRB 251222A / EP251222b
  97. EP251222b/GRB 251222A: Einstein Probe detection of an X-ray transient
  98. EP251222a: Einstein Probe detection of an X-ray transient
  99. The EP-WXT trigger 01709250397 is likely a flaring star
  100. EP251220a: VLT/FORS2 spectroscopic redshift z = 2.375

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