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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"

21770 results found.

  1. GRB 250530C: BOOTES-7 optical upper limit
  2. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  3. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  4. GRB 250530C: Enhanced Swift-XRT position
  5. GRB 250530C: Swift detection of a burst
  6. GRB 250530A: SVOM/VT optical upper limit
  7. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  8. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  9. GRB 250530A: SVOM detection of a burst
  10. GRB 250527C: Swift/UVOT Upper Limits
  11. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  12. GRB 250527B: Swift-XRT observations
  13. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  14. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  15. EP250526a: COLIBRÍ optical upper limits
  16. EP250526a: Einstein Probe detection of a fast X-ray transient
  17. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  18. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  19. GRB 250521A: GRBAlpha detection
  20. GRB 250520A: GRBAlpha detection
  21. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  22. GRB 250521D: DDOTI Optical Upper Limit
  23. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  24. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. GRB 250521D: LAST tentative optical counterpart candidate
  26. GRB 250521A: DDOTI Optical Upper Limit
  27. Konus-Wind detection of GRB 250520A (short/hard)
  28. GRB 250520A: VLT/FORS2 Optical Observation
  29. GRB 250502A: Tautenburg observations
  30. GRB 250520A: Swift/UVOT Upper Limits
  31. Konus-Wind detection of GRB 250516B
  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 250516B: GRBAlpha detection
  40. GRB 250520A: Enhanced Swift-XRT position
  41. GRB 250520A: Swift detection of a burst
  42. Swift GRB 250520A: Global MASTER-Net observations report
  43. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  44. GRB 250516A: COLIBRÍ optical upper limit
  45. GRB 250516B: NuSTAR Detection of the Prompt Emission
  46. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  47. GRB 250515A: Swift-XRT observations
  48. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  49. GRB 250515A: 1.6m Mephisto optical detection
  50. GRB 250516A: Swift/UVOT Detection
  51. GRB 250516B: GECAM-B detection of a bright long burst
  52. GRB 250516A: Enhanced Swift-XRT position
  53. GRB 250516A: Swift detection of a burst
  54. GRB 250515A: GOTO candidate optical counterpart
  55. GRB 250424A: COLIBRÍ detection of the associated supernova
  56. GRB 250502A: TESS observations
  57. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  58. Konus-Wind detection of GRB 250506A
  59. EP250512a/GRB 250512B: REM optical/NIR observations
  60. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  61. GRB 250507B: AstroSat CZTI detection
  62. EP250511a: Gemini optical counterpart observation
  63. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  64. EP250511a: Mephisto optical upper limits
  65. GRB 250507B: GRBAlpha detection
  66. GRB 250506A: GRBAlpha detection
  67. GRB 250512B: SVOM detection of a burst
  68. EP250512a: Einstein Probe detection of an X-ray transient
  69. EP250511a: REM optical/NIR observations
  70. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  71. EP250511a: COLIBRÍ optical counterpart candidate
  72. EP250511a: BOOTES-5 optical upper limit
  73. EP250511a: Einstein Probe detection of an X-ray transient
  74. EP250508a: Gemini NIR upper limits
  75. GRB 250510A: Swift-XRT observations
  76. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  77. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  78. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  79. GRB 250507A: J-band observations with WINTER
  80. GRB 250509A: Enhanced Swift-XRT position
  81. GRB 250509A: Swift detection of a burst
  82. GRB 250506A: NOT optical upper limits
  83. EP250508a: Liverpool Telescope optical upper limits
  84. EP250508a: KAIT optical upper limit
  85. GRB 250507A: KAIT optical upper limit
  86. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  87. GRB 250505B: SVOM/GRM observation of a short burst
  88. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  89. EP250508a: REM optical/NIR observations
  90. GRB 250506A: Swift-XRT afterglow detection
  91. EP250508a: COLIBRÍ Optical Limit
  92. EP250508a: Einstein Probe detection of an X-ray transient
  93. GRB 250506A: Swift/UVOT Upper Limits
  94. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  95. GRB 250507A: REM optical/NIR observations
  96. GRB 250507A: SVOM/VT optical upper limit
  97. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  98. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  99. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  100. GRB 250507A: SVOM detection of a long burst

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