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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').
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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.

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subject:"Swift"
body:"GRB"
submitter:"Judith Racusin"

21772 results found.

  1. GRB 250602A: DDOTI Optical Upper Limit
  2. EP#01709177494: SVOM/VT optical observations
  3. GRB 250530C: BOOTES-7 optical upper limit
  4. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  5. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  6. GRB 250530C: Enhanced Swift-XRT position
  7. GRB 250530C: Swift detection of a burst
  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/BAT-GUANO arcminute localization of a burst
  16. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  17. EP250526a: COLIBRÍ optical upper limits
  18. EP250526a: Einstein Probe detection of a fast X-ray transient
  19. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  20. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  21. GRB 250521A: GRBAlpha detection
  22. GRB 250520A: GRBAlpha detection
  23. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  24. GRB 250521D: DDOTI Optical Upper Limit
  25. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  26. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  27. GRB 250521D: LAST tentative optical counterpart candidate
  28. GRB 250521A: DDOTI Optical Upper Limit
  29. Konus-Wind detection of GRB 250520A (short/hard)
  30. GRB 250520A: VLT/FORS2 Optical Observation
  31. GRB 250502A: Tautenburg observations
  32. GRB 250520A: Swift/UVOT Upper Limits
  33. Konus-Wind detection of GRB 250516B
  34. IPN triangulation of GRB 250516B
  35. GRB 250520A: J-band observations with WINTER
  36. GRB 250520A: Gemini-South optical observations
  37. GRB 250520A: REM optical/NIR early observations
  38. GRB 250520A:SVOM/VT optical candidate
  39. GRB 250520A: COLIBRÍ optical upper limit
  40. GRB 250520A: DDOTI Optical Upper Limit
  41. GRB 250516B: GRBAlpha detection
  42. GRB 250520A: Enhanced Swift-XRT position
  43. GRB 250520A: Swift detection of a burst
  44. Swift GRB 250520A: Global MASTER-Net observations report
  45. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  46. GRB 250516A: COLIBRÍ optical upper limit
  47. GRB 250516B: NuSTAR Detection of the Prompt Emission
  48. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  49. GRB 250515A: Swift-XRT observations
  50. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  51. GRB 250515A: 1.6m Mephisto optical detection
  52. GRB 250516A: Swift/UVOT Detection
  53. GRB 250516B: GECAM-B detection of a bright long burst
  54. GRB 250516A: Enhanced Swift-XRT position
  55. GRB 250516A: Swift detection of a burst
  56. GRB 250515A: GOTO candidate optical counterpart
  57. GRB 250424A: COLIBRÍ detection of the associated supernova
  58. GRB 250502A: TESS observations
  59. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  60. Konus-Wind detection of GRB 250506A
  61. EP250512a/GRB 250512B: REM optical/NIR observations
  62. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  63. GRB 250507B: AstroSat CZTI detection
  64. EP250511a: Gemini optical counterpart observation
  65. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  66. EP250511a: Mephisto optical upper limits
  67. GRB 250507B: GRBAlpha detection
  68. GRB 250506A: GRBAlpha detection
  69. GRB 250512B: SVOM detection of a burst
  70. EP250512a: Einstein Probe detection of an X-ray transient
  71. EP250511a: REM optical/NIR observations
  72. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  73. EP250511a: COLIBRÍ optical counterpart candidate
  74. EP250511a: BOOTES-5 optical upper limit
  75. EP250511a: Einstein Probe detection of an X-ray transient
  76. EP250508a: Gemini NIR upper limits
  77. GRB 250510A: Swift-XRT observations
  78. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  79. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  80. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. GRB 250507A: J-band observations with WINTER
  82. GRB 250509A: Enhanced Swift-XRT position
  83. GRB 250509A: Swift detection of a burst
  84. GRB 250506A: NOT optical upper limits
  85. EP250508a: Liverpool Telescope optical upper limits
  86. EP250508a: KAIT optical upper limit
  87. GRB 250507A: KAIT optical upper limit
  88. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  89. GRB 250505B: SVOM/GRM observation of a short burst
  90. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  91. EP250508a: REM optical/NIR observations
  92. GRB 250506A: Swift-XRT afterglow detection
  93. EP250508a: COLIBRÍ Optical Limit
  94. EP250508a: Einstein Probe detection of an X-ray transient
  95. GRB 250506A: Swift/UVOT Upper Limits
  96. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  97. GRB 250507A: REM optical/NIR observations
  98. GRB 250507A: SVOM/VT optical upper limit
  99. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  100. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit

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