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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"

2993 results found.

  1. EP250807a: COLIBRÍ optical upper limit
  2. EP250806a: Upper limit from Fermi-GBM Observations
  3. EP250806a:SVOM/VT refined analysis
  4. EP250806a: Liverpool telescope optical upper limit
  5. GRB 250806A: EP-FXT observation
  6. EP#01709198415/EP250806a: Swift-XRT observations
  7. EP250806a: Global MASTER-Net observations report
  8. EP250802a: EP-FXT follow-up observation
  9. EP250806a: refined analysis of the EP-WXT and EP-FXT observations
  10. EP250806a: Earlier Detection of the VT Candidate by COLIBRÍ and LS
  11. EP250806a: SVOM /VT optical candidate
  12. EP250806a: COLIBRÍ optical upper limit
  13. EP250806a: Einstein Probe detection of an X-ray transient
  14. EP250730a: SVOM/VT optical upper limit
  15. EP250802a: Liverpool Telescope optical upper limits
  16. EP250802a: Global MASTER-Net observations report
  17. EP250802a: GROWTH-India Telescope optical upper limit
  18. EP250802a: Einstein Probe detection of an X-ray transient
  19. The EP-WXT trigger 01709198251 is likely a flaring star
  20. The EP-WXT trigger 01709198202 is likely a flaring star
  21. EP250711a: CrAO and Assy optical observations
  22. EP250730a: Global MASTER-Net observations report
  23. EP250730a: COLIBRÍ optical upper limit
  24. GRB 250727A: Swift-XRT afterglow confirmation and refined analysis
  25. EP250730a: Einstein Probe detection of an X-ray transient
  26. GRB 250727A: EP-FXT follow-up observation
  27. EP-WXT trigger 01709195487: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  28. GRB 250727A: EP-FXT counterpart detection
  29. The EP-WXT trigger 01709195487 is likely a flaring star
  30. Konus-Wind detection of GRB 250725A
  31. EP250702a/GRB250702B,D,E: SVOM/VT optical upper limit
  32. GRB 270713A: Kitab and AbAO Optical Observations
  33. Konus-Wind detection of GRB 250716A
  34. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  35. GRB 250713A: Mephisto optical upper limits
  36. GRB 250713A: SVOM/VT optical upper limit
  37. GRB 250713A: NOT optical upper limits
  38. GRB 250713A: SVOM/C-GFT upper limit
  39. GRB 250713A: Swift-XRT observations
  40. GRB 250713A: EP-FXT counterpart detection
  41. EP250711a: Global MASTER-Net observations report
  42. EP250711a: NOT optical counterpart candidate
  43. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  44. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  45. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  46. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  47. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  48. EP/WXT 01709181970: GOTO observations confirm stellar variability
  49. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  50. The EP-WXT trigger 01709181970 is likely a flaring star
  51. GRB 250704B / EP250704a: VLA radio detection
  52. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  53. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  54. IceCube-250706A: EP-FXT follow-up observations
  55. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  56. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  57. The EP-WXT trigger 01709181580 is likely a flaring star
  58. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  59. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  60. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  61. GRB 250704B: Insight-HXMT detection
  62. Konus-Wind detection of GRB 250703A
  63. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  64. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  65. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  66. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  67. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  68. EP250704a / GRB 250704B: JinShan optical observations
  69. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  70. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  71. EP 250704a: BOOTES-5 optical detection
  72. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  73. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  74. EP250704a / GRB250704B: Swift-XRT counterpart detection
  75. Konus-Wind detection of GRB 250702F
  76. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  77. EP250704a: COLIBRÍ optical counterpart candidate
  78. EP250704a: Einstein Probe detection of an X-ray transient
  79. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  80. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  81. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  82. EP250702a: Global MASTER-Net observations report
  83. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  84. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  85. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  86. Konus-Wind detection of GRB 250627A
  87. GRB 250628B: Swift-XRT observations
  88. GRB 250628B: SVOM/VT optical upper limit
  89. GRB 250628B: EP-FXT counterpart detection
  90. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  91. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  92. Konus-Wind detection of GRB 250620C
  93. The EP-WXT trigger 01709179071 is likely a flaring star
  94. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  95. The EP-WXT trigger 01709178990 is likely a flaring star
  96. EP#01709178975: Swift-XRT counterpart detection
  97. EP-WXT trigger 01709178975: GOTO optical upper limit
  98. The EP-WXT trigger 01709178975 is likely a flaring star
  99. Konus-Wind detection of GRB 250615A / EP250615a
  100. Konus-Wind detection of GRB 250612C (short/hard with extended emission)

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