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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"

32502 results found.

  1. GRB 250521D: DDOTI Optical Upper Limit
  2. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  3. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  4. GRB 250521D: LAST tentative optical counterpart candidate
  5. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  6. GRB 250520A: 10 GHz VLA radio source
  7. GRB 250521B: Swift ToO observations
  8. GRB 250521A: DDOTI Optical Upper Limit
  9. Konus-Wind detection of GRB 250520A (short/hard)
  10. GRB 250520A: VLT/FORS2 Optical Observation
  11. GRB 250502A: Tautenburg observations
  12. GRB 250520A: Swift/UVOT Upper Limits
  13. Konus-Wind detection of GRB 250516B
  14. IPN triangulation of GRB 250516B
  15. GRB 250520A: J-band observations with WINTER
  16. GRB 250520A: Gemini-South optical observations
  17. GRB 250520A: REM optical/NIR early observations
  18. GRB 250520A:SVOM/VT optical candidate
  19. GRB 250520A: COLIBRÍ optical upper limit
  20. GRB 250520A: DDOTI Optical Upper Limit
  21. GRB 250520A: AstroSat CZTI detection of a short burst
  22. GRB 250516B: GRBAlpha detection
  23. GRB 250520A: SVOM/GRM observation
  24. GRB 250520A: GOTO optical upper limit
  25. GRB 250516B: Insight-HXMT detection
  26. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  27. GRB 250516A: Swift-BAT refined analysis
  28. GRB 250516A: COLIBRÍ optical upper limit
  29. Konus-Wind detection of GRB 250516A
  30. GRB 250516B: NuSTAR Detection of the Prompt Emission
  31. Fermi GRB 250516A: Global MASTER-Net observations report
  32. GRB 250515A: Swift-XRT observations
  33. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  34. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  35. Swift GRB 250516A: Global MASTER-Net observations report
  36. GRB 250515A: 1.6m Mephisto optical detection
  37. GRB 250516A: AstroSat CZTI detection
  38. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  39. GRB 250516A: Fermi GBM Observation
  40. GRB 250516A: Swift/UVOT Detection
  41. GRB 250515A: Swift ToO observations
  42. GRB 250512B / EP250512a: SVOM/GRM analysis
  43. GRB 250515A: GOTO candidate optical counterpart
  44. GRB 250424A: COLIBRÍ detection of the associated supernova
  45. Konus-Wind detection of GRB 250512B / EP250512a
  46. GRB 250502A: TESS observations
  47. GRB 250509A: Swift-BAT refined analysis
  48. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)
  49. Fermi GRB 250512A: Global MASTER-Net observations report
  50. Konus-Wind detection of GRB 250506A
  51. EP250512a/GRB 250512B: REM optical/NIR observations
  52. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  53. GRB 250507B: AstroSat CZTI detection
  54. EP250511a: Gemini optical counterpart observation
  55. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  56. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  57. EP250512a: Global MASTER-Net observations report
  58. EP250511a: FTW optical and NIR observations
  59. GRB 250512B/EP250512a: SVOM/VT optical fading
  60. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  61. EP250511a: Mephisto optical upper limits
  62. GRB 250506A: GRBAlpha detection
  63. GRB 250512B: SVOM detection of a burst
  64. EP250511a: REM optical/NIR observations
  65. EP250511a: Einstein Probe follow-up obsevation and refined analysis
  66. EP250511a: SVOM/VT optical candidate comfirmation
  67. EP250511a: Global MASTER-Net observations report
  68. EP250511a: COLIBRÍ optical counterpart candidate
  69. EP250511a: BOOTES-5 optical upper limit
  70. EP250508a: Gemini NIR upper limits
  71. GRB 250510B: Fermi GBM Observation
  72. Fermi GRB 250510C: Global MASTER-Net observations report
  73. Fermi GRB 250510B: Global MASTER-Net observations report
  74. GRB 250510A: Swift-XRT observations
  75. GRB 250509A: Fermi GBM Observation
  76. IceCube-250506A: No Transient Candidates from the Zwicky Transient Facility
  77. GRB 250510A: follow-up observation with EP-FXT
  78. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  79. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  80. GRB 250507A: J-band observations with WINTER (duplicate submission)
  81. GRB 250507A: J-band observations with WINTER
  82. EP250508a: SVOM/VT optical candidate fading
  83. Fermi GRB 250509A: Global MASTER-Net observations report
  84. Swift GRB 250509A: Global MASTER-Net observations report
  85. GRB 250506A: NOT optical upper limits
  86. EP250508a: Liverpool Telescope optical upper limits
  87. EP250508a: follow-up observation with EP-FXT
  88. EP250508a: SVOM/VT optical candidate
  89. EP250508a: KAIT optical upper limit
  90. GRB 250507A: KAIT optical upper limit
  91. EP250508a: refined analysis of the EP-WXT and EP-FXT observations
  92. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  93. GRB 250506A: GECAM detection
  94. EP250508a: REM optical/NIR observations
  95. EP250508a: Global MASTER-Net observations report
  96. GRB 250506A: SVOM/VT optical upper limit
  97. EP250508a: COLIBRÍ Optical Limit
  98. GRB 250507A: Swift-XRT refined Analysis
  99. IceCube-250506A: Upper limits from a search for additional neutrino events in IceCube
  100. GRB 250506A: Swift/UVOT Upper Limits

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