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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"

19565 results found.

  1. GRB 250601A: Swift ToO observations
  2. EP#01709177494: SVOM/VT optical observations
  3. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  4. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  5. GRB 250530C: Enhanced Swift-XRT position
  6. GRB 250530C: Swift detection of a burst
  7. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  8. GRB 250530A: SVOM/VT optical upper limit
  9. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  10. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  11. GRB 250530A: SVOM detection of a burst
  12. GRB 250527C: Swift/UVOT Upper Limits
  13. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  14. GRB 250527B: Swift-XRT observations
  15. GRB 250527C: Swift ToO observations
  16. GRB 250527B: Tiled Swift observations
  17. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  18. EP250526a: COLIBRÍ optical upper limits
  19. EP250526a: Einstein Probe detection of a fast X-ray transient
  20. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  21. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  22. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  23. GRB 250521D: DDOTI Optical Upper Limit
  24. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. GRB 250521D: LAST tentative optical counterpart candidate
  26. GRB 250521B: Swift ToO observations
  27. GRB 250521A: DDOTI Optical Upper Limit
  28. GRB 250521B: SVOM detection of a burst through offline search
  29. GRB 250520A: VLT/FORS2 Optical Observation
  30. GRB 250502A: Tautenburg observations
  31. GRB 250520A: Swift/UVOT Upper Limits
  32. IPN triangulation of GRB 250516B
  33. GRB 250520A: J-band observations with WINTER
  34. GRB 250520A: Gemini-South optical observations
  35. GRB 250520A: REM optical/NIR early observations
  36. GRB 250520A:SVOM/VT optical candidate
  37. GRB 250520A: COLIBRÍ optical upper limit
  38. GRB 250520A: DDOTI Optical Upper Limit
  39. GRB 250520A: Enhanced Swift-XRT position
  40. GRB 250520A: Swift detection of a burst
  41. GRB 250516A: COLIBRÍ optical upper limit
  42. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  43. GRB 250515A: Swift-XRT observations
  44. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  45. GRB 250515A: 1.6m Mephisto optical detection
  46. GRB 250516A: AstroSat CZTI detection
  47. GRB 250516A: Swift/UVOT Detection
  48. GRB 250515A: Swift ToO observations
  49. GRB 250516A: Enhanced Swift-XRT position
  50. GRB 250516A: Swift detection of a burst
  51. GRB 250424A: COLIBRÍ detection of the associated supernova
  52. Konus-Wind detection of GRB 250512B / EP250512a
  53. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  54. EP250512a/GRB 250512B: REM optical/NIR observations
  55. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  56. GRB 250507B: AstroSat CZTI detection
  57. EP250511a: Gemini optical counterpart observation
  58. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  59. EP250511a: Mephisto optical upper limits
  60. GRB 250512B: SVOM detection of a burst
  61. EP250512a: Einstein Probe detection of an X-ray transient
  62. EP250511a: REM optical/NIR observations
  63. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  64. EP250511a: COLIBRÍ optical counterpart candidate
  65. EP250511a: Einstein Probe detection of an X-ray transient
  66. EP250508a: Gemini NIR upper limits
  67. GRB 250510A: Swift-XRT observations
  68. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  69. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  70. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 250507A: J-band observations with WINTER
  72. GRB 250509A: Enhanced Swift-XRT position
  73. GRB 250509A: Swift detection of a burst
  74. GRB 250506A: NOT optical upper limits
  75. EP250508a: Liverpool Telescope optical upper limits
  76. EP250508a: KAIT optical upper limit
  77. GRB 250507A: KAIT optical upper limit
  78. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  79. GRB 250505B: SVOM/GRM observation of a short burst
  80. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  81. EP250508a: REM optical/NIR observations
  82. GRB 250506A: Swift-XRT afterglow detection
  83. EP250508a: COLIBRÍ Optical Limit
  84. EP250508a: Einstein Probe detection of an X-ray transient
  85. GRB 250506A: Swift/UVOT Upper Limits
  86. GRB 250427B : SVOM detection of a burst through offline search
  87. GRB 250430A / EP250430a: AstroSat CZTI detection
  88. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  89. GRB 250507A: REM optical/NIR observations
  90. GRB 250507A: SVOM/VT optical upper limit
  91. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  92. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  93. GRB 250507A: SVOM detection of a long burst
  94. GRB 250506A: Mephisto optical upper limits
  95. GRB 250506A: Swift ToO observations
  96. GRB 250502A: Bassano Bresciano Observatory upper limit
  97. GRB 250506A: Xinglong 2.16m optical upper limit
  98. GRB 250506A: SVOM improved position and MXT detection of a fading X-ray afterglow
  99. GRB 250506A: REM optical/NIR upper limits
  100. GRB 250506A: TRT optical observations

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