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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"

2962 results found.

  1. GRB 270713A: Kitab and AbAO Optical Observations
  2. Konus-Wind detection of GRB 250716A
  3. GRB 250702B,D,E / EP250702a: H.E.S.S. very-high-energy gamma-ray observations
  4. GRB 250713A: Mephisto optical upper limits
  5. GRB 250713A: SVOM/VT optical upper limit
  6. GRB 250713A: NOT optical upper limits
  7. GRB 250713A: SVOM/C-GFT upper limit
  8. GRB 250713A: Swift-XRT observations
  9. GRB 250713A: EP-FXT counterpart detection
  10. EP250711a: Global MASTER-Net observations report
  11. EP250711a: NOT optical counterpart candidate
  12. EP250711a: EP-WXT detection and FXT follow-up observation of a fast X-ray transient
  13. EP candidate (ID=08500000365): COLIBRÍ optical Upper limit
  14. GRB 250704B / EP250704a: 1.3 GHz MeerKAT Detection
  15. GRB 250702B,D,E / EP250702a: 10 GHz detection with the VLA
  16. IPN triangulation of GRB 250704B (short/hard, consistent with EP 250704a)
  17. EP/WXT 01709181970: GOTO observations confirm stellar variability
  18. EP-WXT trigger 01709181970. confirmation of a stellar flare by BOOTES-6
  19. The EP-WXT trigger 01709181970 is likely a flaring star
  20. GRB 250704B / EP250704a: VLA radio detection
  21. GRB 250706B/C: Konus-Wind analysis of the prompt emission
  22. GRB 250704B: CALET Gamma-Ray Burst Monitor detection
  23. IceCube-250706A: EP-FXT follow-up observations
  24. EP250702a/ GRB 250702B: NuSTAR X-ray Observations
  25. EP250706a/GRB 250706A: EP-WXT detection of a fast X-ray transient
  26. The EP-WXT trigger 01709181580 is likely a flaring star
  27. EP250704a / GRB 250704B: end of optical plateau phase and rapid fading of the counterpart
  28. EP250702a/GRB 250702B,C,D,E: Archival radio observations from ASKAP VAST
  29. Radio observation of GRBs 250702B,C,E / EP250702a with the Allen Telescope Array
  30. GRB 250704B: Insight-HXMT detection
  31. Konus-Wind detection of GRB 250703A
  32. EP250704a/GRB 250704B: GSP observations of the optical counterpart
  33. Konus-Wind detection of short/hard GRB 250704B/ EP250704a
  34. EP250704a / GRB 250704B: NOT observations of the optical afterglow
  35. GRB250702F: afterglow detected by joint EP-ZTF shadowing program
  36. EP250704a / GRB 250704B: VLT/X-shooter spectroscopic redshift z = 0.661
  37. EP250704a / GRB 250704B: JinShan optical observations
  38. EP250704a / GRB 250704B : GROWTH-India Telescope optical observations
  39. EP250704a / GRB 250704B: SVOM/VT optical blue counterpart
  40. EP 250704a: BOOTES-5 optical detection
  41. EP250704a: refined analysis of the EP-WXT and FXT follow-up observations
  42. GRBs 250702B/C/D/E / EP250702a: Swift/UVOT Upper Limits
  43. EP250704a / GRB250704B: Swift-XRT counterpart detection
  44. Konus-Wind detection of GRB 250702F
  45. EP250704a / GRB 250704B: VLT/FORS2 optical afterglow detection
  46. EP250704a: COLIBRÍ optical counterpart candidate
  47. EP250704a: Einstein Probe detection of an X-ray transient
  48. GRBs 250702B,C,D,E / EP250702a: SVOM/GRM observation
  49. GRB 250702B,C,D,E/EP250702a: COLIBRÍ optical upper limit
  50. EP250702a/GRB 250702B, C, D, E: EP-FXT follow-up observation
  51. EP250702a: Global MASTER-Net observations report
  52. GRB 250702B,C,D,E / EP 250702a: MAXI/GSC detection
  53. EP250702a/GRB 250702B,C,D,E: GOTO optical upper limits
  54. EP250702a : an X-ray transient detected by Einstein Probe likely associated with GRB 250702B,C,D,E
  55. Konus-Wind detection of GRB 250627A
  56. GRB 250628B: Swift-XRT observations
  57. GRB 250628B: SVOM/VT optical upper limit
  58. GRB 250628B: EP-FXT counterpart detection
  59. The EP-WXT trigger 01709179435 is likely a new outburst of the CV SS Cyg
  60. The EP-WXT trigger 01709179396 is likely a flaring star CSTAR 38580
  61. Konus-Wind detection of GRB 250620C
  62. The EP-WXT trigger 01709179071 is likely a flaring star
  63. EP-WXT trigger 01709179036: a new outburst of GRS 1739-278
  64. The EP-WXT trigger 01709178990 is likely a flaring star
  65. EP#01709178975: Swift-XRT counterpart detection
  66. EP-WXT trigger 01709178975: GOTO optical upper limit
  67. The EP-WXT trigger 01709178975 is likely a flaring star
  68. Konus-Wind detection of GRB 250615A / EP250615a
  69. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  70. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  71. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  72. The EP-WXT trigger 01709178875 is likely a flaring star
  73. sb25061207: Mephisto optical upper limits
  74. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  75. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  76. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  77. sb25061207: EP-FXT follow-up observation and afterglow candidate
  78. GRB 250612B: Fermi GBM Observation
  79. EP250612a: SVOM/VT optical candidate
  80. EP250612a: Global MASTER-Net observations report
  81. EP250612a/GRB 250612B: JinShan optical upper limit
  82. EP 250612a: AST3-3 Yaoan Optical Observation
  83. EP250610a: Upper limit from Fermi-GBM Observations
  84. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  85. EP250612a: Einstein Probe detection of an X-ray transient
  86. EP250610a: continuous follow-up observations with EP-FXT
  87. EP250610A: Swift/UVOT Upper limits
  88. EP250610a: TNG NIR upper limit
  89. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  90. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  91. EP250610a: Global MASTER-Net observations report
  92. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP250610a: SVOM/VT optical upper limit
  94. EP250610a: REM optical/NIR observations
  95. EP250610a: Swift-XRT counterpart detection
  96. EP250610a: COLIBRÍ optical upper limit
  97. EP250610a: Einstein Probe detection of an X-ray transient
  98. The EP-WXT trigger 01709178283 is likely a flaring star
  99. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  100. The EP-WXT trigger 01709178244 is likely a flaring star

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