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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"

887 results found.

  1. GRB 260429B / EP260429a: EP-FXT follow-up observation
  2. GRB EP260502a: BOOTES-7: early optical upper limit
  3. EP260502a: Las Cumbres upper limit
  4. EP260502a: Einstein Probe detection of an X-ray transient
  5. EP260430a: refined analysis of the EP-WXT and follow-up EP-FXT observations
  6. EP260430a: Einstein Probe detection of an X-ray transient
  7. EP260429a: EP-WXT detection of a fast X-ray transient
  8. GRB260421B: J band upper limit by SYSU 80cm infrared telescope
  9. GRB 260421B: EP-FXT follow-up observation
  10. The EP-WXT trigger 01709260362 is likely a flaring star
  11. The EP-WXT trigger 01709260314 is likely a flaring star
  12. EP260416a: Optical follow-up observations with Kinder
  13. The EP-WXT trigger 01709260303 is likely a flaring star
  14. EP260417a: GROWTH-India Telescope optical upper limit
  15. EP260417b: GROWTH-India Telescope optical upper limit
  16. EP260417a/GRB 260417A: refined analysis of the EP-WXT and follow-up EP-FXT observations
  17. EP260417a: Einstein Probe detection of an X-ray transient
  18. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  19. EP260417b: Einstein Probe detection of a fast X-ray transient
  20. EP260416a: WFST optical observations and rebrightening
  21. EP260416a: SVOM/VT optical observation
  22. EP260416a: Einstein Probe detection of an X-ray transient
  23. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  24. The EP-WXT trigger 01709260122 is likely a flaring star
  25. EP260321a: SVOM/VT optical observations and color changes around peak
  26. The EP-WXT trigger 01709260010 is likely a flaring star
  27. EP-WXT01709259790: Optical Upper limits with kinder observations
  28. The EP-WXT trigger 01709259790 is likely a flaring star
  29. EP260409a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  30. The EP-WXT trigger 01709259773 is likely a flaring star
  31. EP260409a: SVOM/VT optical upper limits
  32. EP260409a: Einstein Probe detection of an X-ray transient
  33. GRB 260310A / AT2026fgk: X-ray rebrightening
  34. EP260402a / GRB 260402A: Mephisto optical upper limits
  35. EP260403a: Mephisto optical upper limits
  36. EP260405a: GMOS-N optical upper limits
  37. EP260405a: SVOM/VT optical upper limits
  38. EP260405a: Einstein Probe detection of a fast X-ray transient
  39. The EP-WXT trigger 01709259621 is likely a flaring star
  40. The EP-WXT trigger 01709259615 is likely a flaring star
  41. EP260403a: refined analysis of the EP-WXT and EP-FXT observations
  42. The EP-WXT trigger 01709259586 is likely a flaring star
  43. EP260403a: LCO optical counterpart detection
  44. EP260403a: Einstein Probe detection of an X-ray transient
  45. EP260402a/GRB 260402A: refined analysis of the EP-WXT and EP-FXT observations
  46. GRB 260402A / EP260402a: SVOM/VT optical upper limits
  47. EP260402a/GRB 260402A: Einstein Probe detection of an X-ray transient
  48. EP260329b: refined analysis of the EP-WXT and EP-FXT observations
  49. EP260329a: EP-FXT follow up observation
  50. EP260329a: NOT optical counterpart candidate
  51. EP260329b: Optical follow-up with Kinder observations
  52. EP260329a: Optical upper limit with Kinder observations
  53. EP260329b: Einstein Probe detection of an X-ray transient
  54. EP260329a: Einstein Probe detection of an X-ray transient
  55. EP-WXT trigger 01709259209: TRT optical counterpart detection
  56. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  57. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  58. EP260327a: SVOM/VT optical upper limits
  59. EP260327a: Einstein Probe detection of an X-ray transient
  60. The EP-WXT trigger 01709259173 is likely a flaring star
  61. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  62. EP260321a: Upper limits from a neutrino search with IceCube
  63. The EP-WXT trigger 01709259112 is likely a flaring star
  64. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  65. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  66. GRB 260321A: EP-FXT follow-up observation
  67. The EP-WXT trigger 01709259045 is likely a flaring star
  68. EP260321a: further Kinder optical observations
  69. EP260321a: Las Cumbres upper limit
  70. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  71. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  72. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  73. EP260321a: Einstein Probe detection of an X-ray transient
  74. The EP-WXT trigger 01709258989 is likely a flaring star
  75. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  76. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  77. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  78. EP260316a: optical upper limit with Kinder observations
  79. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  80. EP260314a: optical upper limit with Kinder observations
  81. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  82. EP260314a: BOOTES-6/DPR optical upper limits at early times
  83. EP260314a: SVOM/VT optical candidate
  84. EP260314a: Einstein Probe detection of an X-ray transient
  85. The EP-WXT trigger 01709258851: Las Cumbres upper limit
  86. GRB 260310A: Einstein Probe Follow-up X-ray Telescope (FXT) Detection
  87. The EP-WXT trigger 01709258843 is not a real source
  88. EP260302a: MeerKAT radio counterpart
  89. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  90. EP260306a: Einstein Probe detection of an X-ray transient
  91. The EP-WXT trigger 01709258759: Las Cumbres discovery of the optical counterpart
  92. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  93. EP260302a: analysis of the follow-up EP-FXT observation
  94. EP260302a: BOOTES-7 optical counterpart detection at early times
  95. GRB 260228A: EP-FXT follow-up observation
  96. EP260302a: Einstein Probe detection of an X-ray transient
  97. The EP-WXT trigger 01709258736: Las Cumbres discovery of the optical counterpart
  98. EP260227A: 3.6m DOT optical afterglow detection
  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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