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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"

23572 results found.

  1. GRB 250530A: SVOM/GRM analysis
  2. GRB 250601A: PRIME J band upper limit.
  3. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  4. GRB 250603A: Swift/UVOT Upper Limits
  5. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  6. GRB 250602A: DDOTI Optical Upper Limit
  7. GRB 250530C: Swift-BAT refined analysis
  8. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  9. EP#01709177494: Swift-XRT counterpart detection of known source
  10. GRB 250530C: BOOTES-7 optical upper limit
  11. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  12. GRB 250530C: Swift-XRT refined Analysis
  13. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  14. GRB 250530C: Swift detection of a burst
  15. GRB 250530A: Swift-XRT counterpart detection
  16. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  17. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  18. GRB 250530A: SVOM detection of a burst
  19. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  20. GRB 250527C: Swift/UVOT Upper Limits
  21. EP J1350.0-8622: EP-FXT follow-up observation
  22. GRB 250527B: Swift-XRT observations
  23. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  24. GRB 250520A: Swift-BAT refined analysis
  25. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  26. EP250526a: COLIBRÍ optical upper limits
  27. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  28. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  29. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  30. Fermi trigger No 769611916: Global MASTER-Net observations report
  31. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  32. GRB 250521A: GRBAlpha detection
  33. GRB 250520A: GRBAlpha detection
  34. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  35. EP#01709176612: Swift-XRT counterpart detection of flaring star
  36. GRB 250521D: DDOTI Optical Upper Limit
  37. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  38. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  39. GRB 250521D: LAST tentative optical counterpart candidate
  40. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  41. GRB 250521A: DDOTI Optical Upper Limit
  42. GRB 250521B: SVOM detection of a burst through offline search
  43. Konus-Wind detection of GRB 250520A (short/hard)
  44. GRB 250502A: Tautenburg observations
  45. Konus-Wind detection of GRB 250516B
  46. IPN triangulation of GRB 250516B
  47. GRB 250520A: J-band observations with WINTER
  48. GRB 250520A: Swift-XRT refined Analysis
  49. GRB 250520A: REM optical/NIR early observations
  50. GRB 250520A: COLIBRÍ optical upper limit
  51. GRB 250520A: DDOTI Optical Upper Limit
  52. GRB 250520A: AstroSat CZTI detection of a short burst
  53. GRB 250516B: GRBAlpha detection
  54. GRB 250520A: GOTO optical upper limit
  55. GRB 250520A: Swift detection of a burst
  56. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  57. GRB 250516A: Swift-BAT refined analysis
  58. GRB 250516A: COLIBRÍ optical upper limit
  59. Konus-Wind detection of GRB 250516A
  60. GRB 250515A: Swift-XRT observations
  61. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  62. GRB 250515A: 1.6m Mephisto optical detection
  63. GRB 250516A: AstroSat CZTI detection
  64. GRB 250516A: Swift-XRT refined Analysis
  65. GRB 250516A: Swift detection of a burst
  66. GRB 250512B / EP250512a: SVOM/GRM analysis
  67. GRB 250515A: GOTO candidate optical counterpart
  68. GRB 250424A: COLIBRÍ detection of the associated supernova
  69. Konus-Wind detection of GRB 250512B / EP250512a
  70. GRB 250509A: Swift-BAT refined analysis
  71. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  72. Konus-Wind detection of GRB 250506A
  73. EP250512a/GRB 250512B: REM optical/NIR observations
  74. GRB 250507B: AstroSat CZTI detection
  75. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  76. EP250511a: Mephisto optical upper limits
  77. GRB 250507B: GRBAlpha detection
  78. GRB 250506A: GRBAlpha detection
  79. EP250512a: Einstein Probe detection of an X-ray transient
  80. EP250511a: REM optical/NIR observations
  81. EP250511a: COLIBRÍ optical counterpart candidate
  82. EP250511a: BOOTES-5 optical upper limit
  83. GRB 250510A: Swift-XRT observations
  84. GRB 250509A: Fermi GBM Observation
  85. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  86. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  87. GRB 250509A: Swift-XRT refined Analysis
  88. GRB 250507A: J-band observations with WINTER
  89. Swift GRB 250509A: Global MASTER-Net observations report
  90. GRB 250509A: Swift detection of a burst
  91. GRB 250506A: NOT optical upper limits
  92. EP250508a: KAIT optical upper limit
  93. GRB 250507A: KAIT optical upper limit
  94. EP250508a: REM optical/NIR observations
  95. GRB 250506A: Swift-XRT afterglow detection
  96. EP250508a: COLIBRÍ Optical Limit
  97. GRB 250507A: Swift-XRT refined Analysis
  98. GRB 250427B : SVOM detection of a burst through offline search
  99. GRB 250507A: follow-up observation with EP-FXT
  100. GRB 250430A / EP250430a: AstroSat CZTI detection

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