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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.

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

31738 results found.

  1. GRB 250530A: EP-FXT counterpart detection
  2. GRB 250530A: SVOM/VT optical upper limit
  3. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  4. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  5. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  6. GRB 250527C: Swift/UVOT Upper Limits
  7. EP J1350.0-8622: EP-FXT follow-up observation
  8. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  9. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  10. GRB 250520A: Swift-BAT refined analysis
  11. GRB 250527C: Swift ToO observations
  12. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  13. EP250526a: SVOM/VT optical upper limit
  14. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  15. GRB 250527B: Tiled Swift observations
  16. GRB 250520A: Gemini-South optical afterglow detection
  17. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  18. GRB 250314A: CIDER NB1008 upper limit
  19. EP250526a: COLIBRÍ optical upper limits
  20. EP250526a: Global MASTER-Net observations report
  21. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  22. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  23. GRB 250520A: 3 GHz MeerKAT Detection
  24. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  25. Fermi GRB 250523A: Global MASTER-Net observations report
  26. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  27. GRB 250521A: GRBAlpha detection
  28. GRB 250520A: GRBAlpha detection
  29. GRB 250521B: SVOM/VT optical upper limit
  30. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  31. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  32. Fermi GRB 250522B: Global MASTER-Net observations report
  33. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  34. GRB 250521D: SVOM/VT optical observations
  35. EP#01709176612: Swift-XRT counterpart detection of flaring star
  36. Fermi GRB 250521D: Global MASTER-Net observations report
  37. GRB 250521D: DDOTI Optical Upper Limit
  38. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  39. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. GRB 250521D: LAST tentative optical counterpart candidate
  41. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  42. GRB 250520A: 10 GHz VLA radio source
  43. GRB 250521B: Swift ToO observations
  44. GRB 250521A: DDOTI Optical Upper Limit
  45. Konus-Wind detection of GRB 250520A (short/hard)
  46. GRB 250520A: VLT/FORS2 Optical Observation
  47. GRB 250502A: Tautenburg observations
  48. GRB 250520A: Swift/UVOT Upper Limits
  49. Konus-Wind detection of GRB 250516B
  50. IPN triangulation of GRB 250516B
  51. GRB 250520A: J-band observations with WINTER
  52. GRB 250520A: Gemini-South optical observations
  53. GRB 250520A: REM optical/NIR early observations
  54. GRB 250520A：SVOM/VT optical candidate
  55. GRB 250520A: COLIBRÍ optical upper limit
  56. GRB 250520A: DDOTI Optical Upper Limit
  57. GRB 250520A: AstroSat CZTI detection of a short burst
  58. GRB 250516B: GRBAlpha detection
  59. GRB 250520A: SVOM/GRM observation
  60. GRB 250520A: GOTO optical upper limit
  61. GRB 250516B: Insight-HXMT detection
  62. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  63. GRB 250516A: Swift-BAT refined analysis
  64. GRB 250516A: COLIBRÍ optical upper limit
  65. Konus-Wind detection of GRB 250516A
  66. GRB 250516B: NuSTAR Detection of the Prompt Emission
  67. Fermi GRB 250516A: Global MASTER-Net observations report
  68. GRB 250515A: Swift-XRT observations
  69. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  70. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  71. Swift GRB 250516A: Global MASTER-Net observations report
  72. GRB 250515A: 1.6m Mephisto optical detection
  73. GRB 250516A: AstroSat CZTI detection
  74. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  75. GRB 250516A: Fermi GBM Observation
  76. GRB 250516A: Swift/UVOT Detection
  77. GRB 250515A: Swift ToO observations
  78. GRB 250512B / EP250512a: SVOM/GRM analysis
  79. GRB 250515A: GOTO candidate optical counterpart
  80. GRB 250424A: COLIBRÍ detection of the associated supernova
  81. Konus-Wind detection of GRB 250512B / EP250512a
  82. GRB 250502A: TESS observations
  83. GRB 250509A: Swift-BAT refined analysis
  84. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  85. Fermi GRB 250512A: Global MASTER-Net observations report
  86. Konus-Wind detection of GRB 250506A
  87. EP250512a/GRB 250512B: REM optical/NIR observations
  88. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  89. GRB 250507B: AstroSat CZTI detection
  90. EP250511a: Gemini optical counterpart observation
  91. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  92. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  93. EP250512a: Global MASTER-Net observations report
  94. EP250511a: FTW optical and NIR observations
  95. GRB 250512B/EP250512a: SVOM/VT optical fading
  96. GRB 250512B/EP250512a：SVOM/VT bright optical counterpart
  97. EP250511a: Mephisto optical upper limits
  98. GRB 250506A: GRBAlpha detection
  99. GRB 250512B: SVOM detection of a burst
  100. EP250511a: REM optical/NIR observations

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