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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"

20960 results found.

  1. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  2. GRB 250527C: Swift ToO observations
  3. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  4. EP250526a: SVOM/VT optical upper limit
  5. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  6. GRB 250527B: Tiled Swift observations
  7. GRB 250520A: Gemini-South optical afterglow detection
  8. Fermi trigger No 770058372: Global MASTER-Net observations report
  9. Fermi trigger No 770047117: Global MASTER-Net observations report
  10. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  11. EP250526a: Global MASTER-Net observations report
  12. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  13. GRB 250520A: 3 GHz MeerKAT Detection
  14. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  15. Fermi GRB 250523A: Global MASTER-Net observations report
  16. Fermi trigger No 769611916: Global MASTER-Net observations report
  17. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  18. GRB 250521B: SVOM/VT optical upper limit
  19. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  20. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  21. Fermi GRB 250522B: Global MASTER-Net observations report
  22. GRB 250521D: SVOM/VT optical observations
  23. EP#01709176612: Swift-XRT counterpart detection of flaring star
  24. Fermi GRB 250521D: Global MASTER-Net observations report
  25. Fermi trigger No 769533898: Global MASTER-Net observations report
  26. Fermi trigger No 769499303: Global MASTER-Net observations report
  27. GRB 250521D: DDOTI Optical Upper Limit
  28. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  29. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. GRB 250521D: LAST tentative optical counterpart candidate
  31. GRB 250520A: 10 GHz VLA radio source
  32. GRB 250521B: Swift ToO observations
  33. GRB 250521A: DDOTI Optical Upper Limit
  34. GRB 250520A: VLT/FORS2 Optical Observation
  35. GRB 250502A: Tautenburg observations
  36. GRB 250520A: Swift/UVOT Upper Limits
  37. GRB 250520A: J-band observations with WINTER
  38. GRB 250520A: Gemini-South optical observations
  39. GRB 250520A: REM optical/NIR early observations
  40. GRB 250520A: COLIBRÍ optical upper limit
  41. GRB 250520A: DDOTI Optical Upper Limit
  42. GRB 250520A: GOTO optical upper limit
  43. Swift GRB 250520A: Global MASTER-Net observations report
  44. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  45. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  46. Fermi GRB 250516A: Global MASTER-Net observations report
  47. GRB 250515A: Swift-XRT observations
  48. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  49. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  50. Swift GRB 250516A: Global MASTER-Net observations report
  51. GRB 250515A: 1.6m Mephisto optical detection
  52. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  53. GRB 250516A: Swift/UVOT Detection
  54. GRB 250515A: Swift ToO observations
  55. GRB 250515A: GOTO candidate optical counterpart
  56. MAXI GRB250515.65: Global MASTER-Net observations report
  57. GRB 250424A: COLIBRÍ detection of the associated supernova
  58. GRB 250502A: TESS observations
  59. Fermi trigger No 768922089: Global MASTER-Net observations report
  60. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  61. Fermi GRB 250512A: Global MASTER-Net observations report
  62. EP250512a/GRB 250512B: REM optical/NIR observations
  63. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  64. EP250511a: Gemini optical counterpart observation
  65. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  66. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  67. EP250512a: Global MASTER-Net observations report
  68. EP250511a: FTW optical and NIR observations
  69. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  70. EP250511a: Mephisto optical upper limits
  71. EP250511a: REM optical/NIR observations
  72. EP250511a: SVOM/VT optical candidate comfirmation
  73. EP250511a: Global MASTER-Net observations report
  74. EP250508a: Gemini NIR upper limits
  75. Fermi GRB 250510C: Global MASTER-Net observations report
  76. Fermi GRB 250510B: Global MASTER-Net observations report
  77. GRB 250510A: Swift-XRT observations
  78. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  79. GRB 250510A: follow-up observation with EP-FXT
  80. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. GRB 250507A: J-band observations with WINTER (duplicate submission)
  82. GRB 250507A: J-band observations with WINTER
  83. Fermi GRB 250509A: Global MASTER-Net observations report
  84. Swift GRB 250509A: Global MASTER-Net observations report
  85. EP250508a: follow-up observation with EP-FXT
  86. GRB 250507A: KAIT optical upper limit
  87. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  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: Global MASTER-Net observations report
  92. GRB 250506A: SVOM/VT optical upper limit
  93. EP250508a: COLIBRÍ Optical Limit
  94. GRB 250506A: Swift/UVOT Upper Limits
  95. EP#01709175213/IGR J19566+0326: Swift-XRT detection
  96. GRB 250507A: refined SVOM/MXT data analysis
  97. GRB 250507A: REM optical/NIR observations
  98. GRB 250507A: SVOM/VT optical upper limit
  99. GRB 250506A: Swift-XRT observations
  100. Fermi-LAT Gamma-ray Observations of IceCube-250506A

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