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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"

21269 results found.

  1. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  2. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  3. GRB 250530C: Enhanced Swift-XRT position
  4. GRB 250530C: Swift detection of a burst
  5. GRB 250530A: SVOM/VT optical upper limit
  6. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  7. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  8. GRB 250530A: SVOM detection of a burst
  9. GRB 250527C: Swift/UVOT Upper Limits
  10. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  11. GRB 250527B: Swift-XRT observations
  12. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  13. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  14. EP250526a: COLIBRÍ optical upper limits
  15. EP250526a: Einstein Probe detection of a fast X-ray transient
  16. EP J1350.0-8622: Einstein Probe detection of an X-ray transient candidate
  17. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  18. GRB 250521A: GRBAlpha detection
  19. GRB 250520A: GRBAlpha detection
  20. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  21. GRB 250521D: DDOTI Optical Upper Limit
  22. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  23. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  24. GRB 250521D: LAST tentative optical counterpart candidate
  25. GRB 250521A: DDOTI Optical Upper Limit
  26. Konus-Wind detection of GRB 250520A (short/hard)
  27. GRB 250520A: VLT/FORS2 Optical Observation
  28. GRB 250502A: Tautenburg observations
  29. GRB 250520A: Swift/UVOT Upper Limits
  30. Konus-Wind detection of GRB 250516B
  31. IPN triangulation of GRB 250516B
  32. GRB 250520A: J-band observations with WINTER
  33. GRB 250520A: Gemini-South optical observations
  34. GRB 250520A: REM optical/NIR early observations
  35. GRB 250520A：SVOM/VT optical candidate
  36. GRB 250520A: COLIBRÍ optical upper limit
  37. GRB 250520A: DDOTI Optical Upper Limit
  38. GRB 250516B: GRBAlpha detection
  39. GRB 250520A: Enhanced Swift-XRT position
  40. GRB 250520A: Swift detection of a burst
  41. Swift GRB 250520A: Global MASTER-Net observations report
  42. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  43. GRB 250516A: COLIBRÍ optical upper limit
  44. GRB 250516B: NuSTAR Detection of the Prompt Emission
  45. EP-WXT trigger (ID: 01709176312): a new X-ray outburst of HMXB RX J0111.2-7317
  46. GRB 250515A: Swift-XRT observations
  47. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  48. GRB 250515A: 1.6m Mephisto optical detection
  49. GRB 250516A: Swift/UVOT Detection
  50. GRB 250516B: GECAM-B detection of a bright long burst
  51. GRB 250516A: Enhanced Swift-XRT position
  52. GRB 250516A: Swift detection of a burst
  53. GRB 250515A: GOTO candidate optical counterpart
  54. GRB 250424A: COLIBRÍ detection of the associated supernova
  55. GRB 250502A: TESS observations
  56. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  57. Konus-Wind detection of GRB 250506A
  58. EP250512a/GRB 250512B: REM optical/NIR observations
  59. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  60. GRB 250507B: AstroSat CZTI detection
  61. EP250511a: Gemini optical counterpart observation
  62. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  63. EP250511a: Mephisto optical upper limits
  64. GRB 250507B: GRBAlpha detection
  65. GRB 250506A: GRBAlpha detection
  66. GRB 250512B: SVOM detection of a burst
  67. EP250512a: Einstein Probe detection of an X-ray transient
  68. EP250511a: REM optical/NIR observations
  69. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  70. EP250511a: COLIBRÍ optical counterpart candidate
  71. EP250511a: BOOTES-5 optical upper limit
  72. EP250511a: Einstein Probe detection of an X-ray transient
  73. EP250508a: Gemini NIR upper limits
  74. GRB 250510A: Swift-XRT observations
  75. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  76. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  77. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  78. GRB 250507A: J-band observations with WINTER
  79. GRB 250509A: Enhanced Swift-XRT position
  80. GRB 250509A: Swift detection of a burst
  81. GRB 250506A: NOT optical upper limits
  82. EP250508a: Liverpool Telescope optical upper limits
  83. EP250508a: KAIT optical upper limit
  84. GRB 250507A: KAIT optical upper limit
  85. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  86. GRB 250505B: SVOM/GRM observation of a short burst
  87. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  88. EP250508a: REM optical/NIR observations
  89. GRB 250506A: Swift-XRT afterglow detection
  90. EP250508a: COLIBRÍ Optical Limit
  91. EP250508a: Einstein Probe detection of an X-ray transient
  92. GRB 250506A: Swift/UVOT Upper Limits
  93. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  94. GRB 250507A: REM optical/NIR observations
  95. GRB 250507A: SVOM/VT optical upper limit
  96. Fermi-LAT Gamma-ray Observations of IceCube-250506A
  97. GRB 250507A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. EP-WXT trigger 01709175213: a new X-ray outburst of LMXB MAXI J1957+032
  99. GRB 250507A: SVOM detection of a long burst
  100. GRB 250506A: Mephisto optical upper limits

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