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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"

24887 results found.

  1. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  2. EP250612a: Einstein Probe detection of an X-ray transient
  3. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  4. sb25061207: SVOM detection of a X-ray transient
  5. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  6. Fermi GBM Sub-Threshold Detection of GRB 250610B
  7. GRB 250610B: Swift/UVOT Detection
  8. EP250610A: Swift/UVOT Upper limits
  9. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  10. EP250610a: TNG NIR upper limit
  11. GRB 250610B: REM optical/NIR observations
  12. EP250610a: Liverpool Telescope optical upper limits
  13. GRB 250610B: additional Liverpool Telescope optical observations
  14. GRB 250610B: SVOM/GRM analysis
  15. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  16. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  17. GRB 250610B: Swift-XRT counterpart detection
  18. GRB 250610B: SVOM/VT optical counterpart
  19. GRB 250610B: OHP/T120 optical counterpart candidate
  20. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  21. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  22. GRB 250605A: Swift-BAT refined analysis
  23. EP250610a: SVOM/VT optical upper limit
  24. EP250610a: REM optical/NIR observations
  25. GRB 250609A: Fermi GBM Observation
  26. EP250610a: Swift-XRT counterpart detection
  27. EP250610a: COLIBRÍ optical upper limit
  28. EP250610a: Einstein Probe detection of an X-ray transient
  29. Fermi trigger No 771072240: Global MASTER-Net observations report
  30. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  31. GRB 250605A: Swift/UVOT Upper Limits
  32. GRB 250527C: CrAO Optical Upper Limit
  33. GRB 250607A: SVOM/GRM observation of a long burst
  34. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  35. GRB 250605A: Swift-XRT refined Analysis
  36. GRB 250605A: Enhanced Swift-XRT position
  37. GRB 250605A: Swift detection of a burst
  38. IPN triangulation of GRB 250404B
  39. IPN triangulation of GRB 250529A
  40. GRB 250601A: PRIME H band upper limit.
  41. GRB 250601A: PRIME J band upper limit.
  42. GRB 250601A: VLT/FORS2 Optical Observation
  43. GRB 250601A: Fermi GBM Observation
  44. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  45. GRB 250603A: Swift/UVOT Upper Limits
  46. GRB 250603A: Swift-XRT refined Analysis
  47. GRB 250603A: Enhanced Swift-XRT position
  48. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  49. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  50. GRB 250602A: Fermi GBM Observation
  51. GRB 250602A: DDOTI Optical Upper Limit
  52. GRB 250530C: Swift-BAT refined analysis
  53. GRB 250601A: Swift/XRT candidate afterglow
  54. GRB 250601A: Swift-XRT observations
  55. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  56. GRB 250601A: Fermi GBM Final Real-time Localization
  57. EP#01709177494: SVOM/VT optical observations
  58. EP#01709177494: Swift-XRT counterpart detection of known source
  59. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  60. GRB 250530C: Swift-XRT refined Analysis
  61. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  62. GRB 250530C: Enhanced Swift-XRT position
  63. GRB 250530C: Swift detection of a burst
  64. GRB 250530A: EP-FXT counterpart detection
  65. GRB 250530A: SVOM/VT optical upper limit
  66. GRB 250530A: Swift-XRT counterpart detection
  67. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  68. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  69. GRB 250530A: SVOM detection of a burst
  70. GRB 250527C: Swift/UVOT Upper Limits
  71. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  72. GRB 250527B: Swift-XRT observations
  73. GRB 250520A: Swift-BAT refined analysis
  74. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  75. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  76. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  77. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  78. GRB 250314A: CIDER NB1008 upper limit
  79. EP250526a: COLIBRÍ optical upper limits
  80. EP250526a: Einstein Probe detection of a fast X-ray transient
  81. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  82. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  83. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  84. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  85. EP#01709176612: Swift-XRT counterpart detection of flaring star
  86. GRB 250521D: DDOTI Optical Upper Limit
  87. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  88. GRB 250521D: LAST tentative optical counterpart candidate
  89. GRB 250521A: DDOTI Optical Upper Limit
  90. GRB 250520A: VLT/FORS2 Optical Observation
  91. GRB 250502A: Tautenburg observations
  92. GRB 250520A: Swift/UVOT Upper Limits
  93. IPN triangulation of GRB 250516B
  94. GRB 250520A: J-band observations with WINTER
  95. GRB 250520A: Gemini-South optical observations
  96. GRB 250520A: Swift-XRT refined Analysis
  97. GRB 250520A: REM optical/NIR early observations
  98. GRB 250520A:SVOM/VT optical candidate
  99. GRB 250520A: COLIBRÍ optical upper limit
  100. GRB 250520A: DDOTI Optical Upper Limit

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