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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"

39059 results found.

  1. GRB 250520A: AstroSat CZTI detection of a short burst
  2. GRB 250516B: GRBAlpha detection
  3. GRB 250520A: SVOM/GRM observation
  4. GRB 250520A: Enhanced Swift-XRT position
  5. GRB 250520A: GOTO optical upper limit
  6. GRB 250520A: Prompt enhanced Swift-XRT position
  7. GRB 250520A: Swift detection of a burst
  8. Swift GRB 250520A: Global MASTER-Net observations report
  9. GRB 250516B: Insight-HXMT detection
  10. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  11. GRB 250516A: Swift-BAT refined analysis
  12. GRB 250516A: COLIBRÍ optical upper limit
  13. Konus-Wind detection of GRB 250516A
  14. GRB 250516B: NuSTAR Detection of the Prompt Emission
  15. Fermi GRB 250516A: Global MASTER-Net observations report
  16. GRB 250515A: Swift-XRT observations
  17. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  18. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  19. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  20. Swift GRB 250516A: Global MASTER-Net observations report
  21. GRB 250515A: 1.6m Mephisto optical detection
  22. GRB 250516A: AstroSat CZTI detection
  23. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  24. GRB 250516A: Fermi GBM Observation
  25. GRB 250516A: Swift-XRT refined Analysis
  26. GRB 250516A: Swift/UVOT Detection
  27. GRB 250515A: Swift ToO observations
  28. GRB 250516B: GECAM-B detection of a bright long burst
  29. GRB 250516A: Enhanced Swift-XRT position
  30. GRB 250516A: Swift detection of a burst
  31. GRB 250516A: Fermi GBM Final Real-time Localization
  32. GRB 250512B / EP250512a: SVOM/GRM analysis
  33. GRB 250515A: GOTO candidate optical counterpart
  34. MAXI GRB250515.65: Global MASTER-Net observations report
  35. GRB 250515A: Fermi GBM Final Localization
  36. GRB 250424A: COLIBRÍ detection of the associated supernova
  37. Konus-Wind detection of GRB 250512B / EP250512a
  38. GRB 250502A: TESS observations
  39. Fermi trigger No 768922089: Global MASTER-Net observations report
  40. GRB 250511A: GECAM-A detection of a short burst
  41. GRB 250509A: Swift-BAT refined analysis
  42. Fermi GRB 250512A: Global MASTER-Net observations report
  43. Konus-Wind detection of GRB 250506A
  44. EP250512a/GRB 250512B: REM optical/NIR observations
  45. EP250511a: Koshka Zeiss-1000 Optical Upper Limit
  46. GRB 250507B: AstroSat CZTI detection
  47. EP250512a/GRB 250512B refined analysis of the EP-WXT and EP-FXT observations
  48. EP250512a/GRB 250512B: FTW optical and NIR observations of the counterpart
  49. EP250512a: Global MASTER-Net observations report
  50. GRB 250512B/EP250512a: SVOM/VT optical fading
  51. GRB 250512B/EP250512a:SVOM/VT bright optical counterpart
  52. EP250511a: Mephisto optical upper limits
  53. GRB 250507B: GRBAlpha detection
  54. GRB 250506A: GRBAlpha detection
  55. GRB 250512B: SVOM detection of a burst
  56. GRB 250507B: SVOM/GRM observation of a burst
  57. GRB 250512A: Fermi GBM Final Real-time Localization
  58. EP250511a: REM optical/NIR observations
  59. EP250511a: Global MASTER-Net observations report
  60. EP250511a: COLIBRÍ optical counterpart candidate
  61. GRB 250510B: Fermi GBM Observation
  62. Fermi GRB 250510C: Global MASTER-Net observations report
  63. Fermi GRB 250510B: Global MASTER-Net observations report
  64. GRB 250510C: Fermi GBM Final Real-time Localization
  65. GRB 250510A: Swift-XRT observations
  66. GRB 250509A: Fermi GBM Observation
  67. GRB 250510A: follow-up observation with EP-FXT
  68. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  69. GRB 250510B: Fermi GBM Final Localization
  70. GRB 250510A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. GRB 250509A: Swift-XRT refined Analysis
  72. GRB 250510A: SVOM possible detection of a burst
  73. GRB 250507A: J-band observations with WINTER (duplicate submission)
  74. GRB 250507A: J-band observations with WINTER
  75. GRB 250509A: Enhanced Swift-XRT position
  76. GRB 250509A: Prompt enhanced Swift-XRT position
  77. Fermi GRB 250509A: Global MASTER-Net observations report
  78. Swift GRB 250509A: Global MASTER-Net observations report
  79. GRB 250509A: Swift detection of a burst
  80. GRB 250509A: Fermi GBM Final Real-time Localization
  81. GRB 250506A: NOT optical upper limits
  82. EP250508a: KAIT optical upper limit
  83. GRB 250507A: KAIT optical upper limit
  84. GRB 250505B: SVOM/GRM observation of a short burst
  85. GRB 250502A: Calapai Observatory, Massa S. Giorgio (Messina), optical observation.
  86. GRB 250506A: GECAM detection
  87. EP250508a: REM optical/NIR observations
  88. GRB 250506A: Swift-XRT afterglow detection
  89. EP250508a: Global MASTER-Net observations report
  90. GRB 250506A: SVOM/VT optical upper limit
  91. EP250508a: COLIBRÍ Optical Limit
  92. GRB 250507A: Swift-XRT refined Analysis
  93. GRB 250506A: Swift/UVOT Upper Limits
  94. GRB 250427B : SVOM detection of a burst through offline search
  95. GRB 250507A: follow-up observation with EP-FXT
  96. GRB 250430A / EP250430a: AstroSat CZTI detection
  97. GRB 250506A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  98. GRB 250507A: refined SVOM/MXT data analysis
  99. GRB 250507A: REM optical/NIR observations
  100. GRB 250507A: SVOM/VT optical upper limit

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