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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"

23575 results found.

  1. Konus-Wind detection of GRB 250601A
  2. IPN triangulation of GRB 250529A
  3. GRB 250601A: PRIME H band upper limit.
  4. GRB 250530A: SVOM/GRM analysis
  5. GRB 250601A: PRIME J band upper limit.
  6. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  7. GRB 250603A: Swift/UVOT Upper Limits
  8. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  9. GRB 250602A: DDOTI Optical Upper Limit
  10. GRB 250530C: Swift-BAT refined analysis
  11. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  12. EP#01709177494: Swift-XRT counterpart detection of known source
  13. GRB 250530C: BOOTES-7 optical upper limit
  14. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  15. GRB 250530C: Swift-XRT refined Analysis
  16. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  17. GRB 250530C: Swift detection of a burst
  18. GRB 250530A: Swift-XRT counterpart detection
  19. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  20. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  21. GRB 250530A: SVOM detection of a burst
  22. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  23. GRB 250527C: Swift/UVOT Upper Limits
  24. EP J1350.0-8622: EP-FXT follow-up observation
  25. GRB 250527B: Swift-XRT observations
  26. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  27. GRB 250520A: Swift-BAT refined analysis
  28. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  29. EP250526a: COLIBRÍ optical upper limits
  30. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  31. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  32. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  33. Fermi trigger No 769611916: Global MASTER-Net observations report
  34. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  35. GRB 250521A: GRBAlpha detection
  36. GRB 250520A: GRBAlpha detection
  37. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  38. EP#01709176612: Swift-XRT counterpart detection of flaring star
  39. GRB 250521D: DDOTI Optical Upper Limit
  40. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  41. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  42. GRB 250521D: LAST tentative optical counterpart candidate
  43. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  44. GRB 250521A: DDOTI Optical Upper Limit
  45. GRB 250521B: SVOM detection of a burst through offline search
  46. Konus-Wind detection of GRB 250520A (short/hard)
  47. GRB 250502A: Tautenburg observations
  48. Konus-Wind detection of GRB 250516B
  49. IPN triangulation of GRB 250516B
  50. GRB 250520A: J-band observations with WINTER
  51. GRB 250520A: Swift-XRT refined Analysis
  52. GRB 250520A: REM optical/NIR early observations
  53. GRB 250520A: COLIBRÍ optical upper limit
  54. GRB 250520A: DDOTI Optical Upper Limit
  55. GRB 250520A: AstroSat CZTI detection of a short burst
  56. GRB 250516B: GRBAlpha detection
  57. GRB 250520A: GOTO optical upper limit
  58. GRB 250520A: Swift detection of a burst
  59. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  60. GRB 250516A: Swift-BAT refined analysis
  61. GRB 250516A: COLIBRÍ optical upper limit
  62. Konus-Wind detection of GRB 250516A
  63. GRB 250515A: Swift-XRT observations
  64. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  65. GRB 250515A: 1.6m Mephisto optical detection
  66. GRB 250516A: AstroSat CZTI detection
  67. GRB 250516A: Swift-XRT refined Analysis
  68. GRB 250516A: Swift detection of a burst
  69. GRB 250512B / EP250512a: SVOM/GRM analysis
  70. GRB 250515A: GOTO candidate optical counterpart
  71. GRB 250424A: COLIBRÍ detection of the associated supernova
  72. Konus-Wind detection of GRB 250512B / EP250512a
  73. GRB 250509A: Swift-BAT refined analysis
  74. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  75. Konus-Wind detection of GRB 250506A
  76. EP250512a/GRB 250512B: REM optical/NIR observations
  77. GRB 250507B: AstroSat CZTI detection
  78. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  79. EP250511a: Mephisto optical upper limits
  80. GRB 250507B: GRBAlpha detection
  81. GRB 250506A: GRBAlpha detection
  82. EP250512a: Einstein Probe detection of an X-ray transient
  83. EP250511a: REM optical/NIR observations
  84. EP250511a: COLIBRÍ optical counterpart candidate
  85. EP250511a: BOOTES-5 optical upper limit
  86. GRB 250510A: Swift-XRT observations
  87. GRB 250509A: Fermi GBM Observation
  88. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  89. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 250509A: Swift-XRT refined Analysis
  91. GRB 250507A: J-band observations with WINTER
  92. Swift GRB 250509A: Global MASTER-Net observations report
  93. GRB 250509A: Swift detection of a burst
  94. GRB 250506A: NOT optical upper limits
  95. EP250508a: KAIT optical upper limit
  96. GRB 250507A: KAIT optical upper limit
  97. EP250508a: REM optical/NIR observations
  98. GRB 250506A: Swift-XRT afterglow detection
  99. EP250508a: COLIBRÍ Optical Limit
  100. GRB 250507A: Swift-XRT refined Analysis

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