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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.

Advanced Search Examples (click to copy):

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

32548 results found.

  1. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  2. GRB 250601A: Swift ToO observations
  3. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  4. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  5. EP#01709177494: SVOM/VT optical observations
  6. Fermi GRB 250531A: Global MASTER-Net observations report
  7. GRB 250530C: BOOTES-7 optical upper limit
  8. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  9. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  10. Swift GRB 250530C: Global MASTER-Net observations report
  11. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  12. GRB 250530A: EP-FXT counterpart detection
  13. GRB 250530A: SVOM/VT optical upper limit
  14. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  15. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  16. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  17. GRB 250527C: Swift/UVOT Upper Limits
  18. EP J1350.0-8622: EP-FXT follow-up observation
  19. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  20. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  21. GRB 250520A: Swift-BAT refined analysis
  22. GRB 250527C: Swift ToO observations
  23. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  24. EP250526a: SVOM/VT optical upper limit
  25. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  26. GRB 250527B: Tiled Swift observations
  27. GRB 250520A: Gemini-South optical afterglow detection
  28. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  29. GRB 250314A: CIDER NB1008 upper limit
  30. EP250526a: COLIBRÍ optical upper limits
  31. EP250526a: Global MASTER-Net observations report
  32. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  33. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  34. GRB 250520A: 3 GHz MeerKAT Detection
  35. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  36. Fermi GRB 250523A: Global MASTER-Net observations report
  37. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  38. GRB 250521A: GRBAlpha detection
  39. GRB 250520A: GRBAlpha detection
  40. GRB 250521B: SVOM/VT optical upper limit
  41. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  42. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  43. Fermi GRB 250522B: Global MASTER-Net observations report
  44. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  45. GRB 250521D: SVOM/VT optical observations
  46. EP#01709176612: Swift-XRT counterpart detection of flaring star
  47. Fermi GRB 250521D: Global MASTER-Net observations report
  48. GRB 250521D: DDOTI Optical Upper Limit
  49. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  50. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 250521D: LAST tentative optical counterpart candidate
  52. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  53. GRB 250520A: 10 GHz VLA radio source
  54. GRB 250521B: Swift ToO observations
  55. GRB 250521A: DDOTI Optical Upper Limit
  56. Konus-Wind detection of GRB 250520A (short/hard)
  57. GRB 250520A: VLT/FORS2 Optical Observation
  58. GRB 250502A: Tautenburg observations
  59. GRB 250520A: Swift/UVOT Upper Limits
  60. Konus-Wind detection of GRB 250516B
  61. IPN triangulation of GRB 250516B
  62. GRB 250520A: J-band observations with WINTER
  63. GRB 250520A: Gemini-South optical observations
  64. GRB 250520A: REM optical/NIR early observations
  65. GRB 250520A:SVOM/VT optical candidate
  66. GRB 250520A: COLIBRÍ optical upper limit
  67. GRB 250520A: DDOTI Optical Upper Limit
  68. GRB 250520A: AstroSat CZTI detection of a short burst
  69. GRB 250516B: GRBAlpha detection
  70. GRB 250520A: SVOM/GRM observation
  71. GRB 250520A: GOTO optical upper limit
  72. GRB 250516B: Insight-HXMT detection
  73. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  74. GRB 250516A: Swift-BAT refined analysis
  75. GRB 250516A: COLIBRÍ optical upper limit
  76. Konus-Wind detection of GRB 250516A
  77. GRB 250516B: NuSTAR Detection of the Prompt Emission
  78. Fermi GRB 250516A: Global MASTER-Net observations report
  79. GRB 250515A: Swift-XRT observations
  80. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  81. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  82. Swift GRB 250516A: Global MASTER-Net observations report
  83. GRB 250515A: 1.6m Mephisto optical detection
  84. GRB 250516A: AstroSat CZTI detection
  85. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  86. GRB 250516A: Fermi GBM Observation
  87. GRB 250516A: Swift/UVOT Detection
  88. GRB 250515A: Swift ToO observations
  89. GRB 250512B / EP250512a: SVOM/GRM analysis
  90. GRB 250515A: GOTO candidate optical counterpart
  91. GRB 250424A: COLIBRÍ detection of the associated supernova
  92. Konus-Wind detection of GRB 250512B / EP250512a
  93. GRB 250502A: TESS observations
  94. GRB 250509A: Swift-BAT refined analysis
  95. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  96. Fermi GRB 250512A: Global MASTER-Net observations report
  97. Konus-Wind detection of GRB 250506A
  98. EP250512a/GRB 250512B: REM optical/NIR observations
  99. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  100. GRB 250507B: AstroSat CZTI detection

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