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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"

20494 results found.

  1. EP/WXT 01709177873: GOTO observations confirm stellar variability
  2. Fermi GRB 250606A: Global MASTER-Net observations report
  3. Fermi trigger No 770867684: Global MASTER-Net observations report
  4. GRB 250605A: LT optical observations
  5. Swift GRB250605.79: Global MASTER-Net observations report
  6. GRB 250601A: PRIME H band upper limit.
  7. GRB 250530A: SVOM/GRM analysis
  8. GRB 250601A: PRIME J band upper limit.
  9. GRB 250601A: VLT/FORS2 Optical Observation
  10. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  11. GRB 250603A: Swift/UVOT Upper Limits
  12. Fermi trigger No 770638414: Global MASTER-Net observations report
  13. Swift GRB250603.05: Global MASTER-Net observations report
  14. GRB 250602A: DDOTI Optical Upper Limit
  15. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  16. GRB 250601A: Swift/XRT candidate afterglow
  17. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  18. GRB 250601A: Swift-XRT observations
  19. Fermi GRB 250601A: Global MASTER-Net observations report
  20. Fermi trigger No 770470765: Global MASTER-Net observations report
  21. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  22. GRB 250601A: Swift ToO observations
  23. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  24. EP#01709177494: SVOM/VT optical observations
  25. Fermi GRB 250531A: Global MASTER-Net observations report
  26. EP#01709177494: Swift-XRT counterpart detection of known source
  27. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  28. Swift GRB 250530C: Global MASTER-Net observations report
  29. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  30. GRB 250530A: SVOM/VT optical upper limit
  31. GRB 250530A: Swift-XRT counterpart detection
  32. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  33. GRB 250527C: Swift/UVOT Upper Limits
  34. GRB 250527B: Swift-XRT observations
  35. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  36. GRB 250527C: Swift ToO observations
  37. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  38. EP250526a: SVOM/VT optical upper limit
  39. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  40. GRB 250527B: Tiled Swift observations
  41. GRB 250520A: Gemini-South optical afterglow detection
  42. Fermi trigger No 770058372: Global MASTER-Net observations report
  43. Fermi trigger No 770047117: Global MASTER-Net observations report
  44. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  45. EP250526a: Global MASTER-Net observations report
  46. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  47. GRB 250520A: 3 GHz MeerKAT Detection
  48. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  49. Fermi GRB 250523A: Global MASTER-Net observations report
  50. Fermi trigger No 769611916: Global MASTER-Net observations report
  51. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  52. GRB 250521B: SVOM/VT optical upper limit
  53. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  54. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  55. Fermi GRB 250522B: Global MASTER-Net observations report
  56. GRB 250521D: SVOM/VT optical observations
  57. EP#01709176612: Swift-XRT counterpart detection of flaring star
  58. Fermi GRB 250521D: Global MASTER-Net observations report
  59. Fermi trigger No 769533898: Global MASTER-Net observations report
  60. Fermi trigger No 769499303: Global MASTER-Net observations report
  61. GRB 250521D: DDOTI Optical Upper Limit
  62. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  63. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  64. GRB 250521D: LAST tentative optical counterpart candidate
  65. GRB 250520A: 10 GHz VLA radio source
  66. GRB 250521B: Swift ToO observations
  67. GRB 250521A: DDOTI Optical Upper Limit
  68. GRB 250520A: VLT/FORS2 Optical Observation
  69. GRB 250502A: Tautenburg observations
  70. GRB 250520A: Swift/UVOT Upper Limits
  71. GRB 250520A: J-band observations with WINTER
  72. GRB 250520A: Gemini-South optical observations
  73. GRB 250520A: REM optical/NIR early observations
  74. GRB 250520A: COLIBRÍ optical upper limit
  75. GRB 250520A: DDOTI Optical Upper Limit
  76. GRB 250520A: GOTO optical upper limit
  77. Swift GRB 250520A: Global MASTER-Net observations report
  78. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  79. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  80. Fermi GRB 250516A: Global MASTER-Net observations report
  81. GRB 250515A: Swift-XRT observations
  82. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  83. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  84. Swift GRB 250516A: Global MASTER-Net observations report
  85. GRB 250515A: 1.6m Mephisto optical detection
  86. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  87. GRB 250516A: Swift/UVOT Detection
  88. GRB 250515A: Swift ToO observations
  89. GRB 250515A: GOTO candidate optical counterpart
  90. MAXI GRB250515.65: Global MASTER-Net observations report
  91. GRB 250424A: COLIBRÍ detection of the associated supernova
  92. GRB 250502A: TESS observations
  93. Fermi trigger No 768922089: Global MASTER-Net observations report
  94. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  95. Fermi GRB 250512A: Global MASTER-Net observations report
  96. EP250512a/GRB 250512B: REM optical/NIR observations
  97. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  98. EP250511a: Gemini optical counterpart observation
  99. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  100. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart

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