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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

37993 results found.

  1. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  2. GRB 250530A: SVOM detection of a burst
  3. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  4. GRB 250527C: Swift/UVOT Upper Limits
  5. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  6. GRB 250529B: Fermi GBM Final Real-time Localization
  7. GRB 250527B: Swift-XRT observations
  8. GRB 250529A: Fermi GBM Final Real-time Localization
  9. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  10. GRB 250520A: Swift-BAT refined analysis
  11. GRB 250527C: Swift ToO observations
  12. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  13. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  14. GRB 250527B: Tiled Swift observations
  15. GRB 250520A: Gemini-South optical afterglow detection
  16. GRB 250527B / MAXI J1450-527 : MAXI/GSC detection
  17. GRB 250527A: Fermi GBM Final Localization
  18. GRB 250314A: CIDER NB1008 upper limit
  19. GRB 250520A: 3 GHz MeerKAT Detection
  20. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  21. Fermi GRB 250523A: Global MASTER-Net observations report
  22. GRB 250521A: GRBAlpha detection
  23. GRB 250520A: GRBAlpha detection
  24. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  25. GRB 250523A: Fermi GBM Final Real-time Localization
  26. GRB 250521B: SVOM/VT optical upper limit
  27. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  28. Fermi GRB 250522B: Global MASTER-Net observations report
  29. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  30. GRB 250522B: Fermi GBM Final Localization
  31. GRB 250521D: SVOM/VT optical observations
  32. GRB 250522A: Fermi GBM Final Real-time Localization
  33. EP#01709176612: Swift-XRT counterpart detection of flaring star
  34. Fermi GRB 250521D: Global MASTER-Net observations report
  35. GRB 250521D: DDOTI Optical Upper Limit
  36. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  37. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  38. GRB 250521D: LAST tentative optical counterpart candidate
  39. GRB 250520A: CALET Gamma-Ray Burst Monitor detection
  40. GRB 250520A: 10 GHz VLA radio source
  41. GRB 250521B: Swift ToO observations
  42. GRB 250521D: Fermi GBM Final Real-time Localization
  43. GRB 250521C: Fermi GBM Final Localization
  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 250520A: VLT/FORS2 Optical Observation
  48. GRB 250502A: Tautenburg observations
  49. GRB 250520A: Swift/UVOT Upper Limits
  50. GRB 250521A: Fermi GBM Final Real-time Localization
  51. Konus-Wind detection of GRB 250516B
  52. IPN triangulation of GRB 250516B
  53. GRB 250520A: J-band observations with WINTER
  54. GRB 250520A: Gemini-South optical observations
  55. GRB 250520A: Swift-XRT refined Analysis
  56. GRB 250520A: REM optical/NIR early observations
  57. GRB 250520B: Fermi GBM Final Real-time Localization
  58. GRB 250520A：SVOM/VT optical candidate
  59. GRB 250520A: COLIBRÍ optical upper limit
  60. GRB 250520A: DDOTI Optical Upper Limit
  61. GRB 250520A: AstroSat CZTI detection of a short burst
  62. GRB 250516B: GRBAlpha detection
  63. GRB 250520A: SVOM/GRM observation
  64. GRB 250520A: Enhanced Swift-XRT position
  65. GRB 250520A: GOTO optical upper limit
  66. GRB 250520A: Prompt enhanced Swift-XRT position
  67. GRB 250520A: Swift detection of a burst
  68. Swift GRB 250520A: Global MASTER-Net observations report
  69. GRB 250516B: Insight-HXMT detection
  70. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  71. GRB 250516A: Swift-BAT refined analysis
  72. GRB 250516A: COLIBRÍ optical upper limit
  73. Konus-Wind detection of GRB 250516A
  74. GRB 250516B: NuSTAR Detection of the Prompt Emission
  75. Fermi GRB 250516A: Global MASTER-Net observations report
  76. GRB 250515A: Swift-XRT observations
  77. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  78. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  79. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  80. Swift GRB 250516A: Global MASTER-Net observations report
  81. GRB 250515A: 1.6m Mephisto optical detection
  82. GRB 250516A: AstroSat CZTI detection
  83. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  84. GRB 250516A: Fermi GBM Observation
  85. GRB 250516A: Swift-XRT refined Analysis
  86. GRB 250516A: Swift/UVOT Detection
  87. GRB 250515A: Swift ToO observations
  88. GRB 250516B: GECAM-B detection of a bright long burst
  89. GRB 250516A: Enhanced Swift-XRT position
  90. GRB 250516A: Swift detection of a burst
  91. GRB 250516A: Fermi GBM Final Real-time Localization
  92. GRB 250512B / EP250512a: SVOM/GRM analysis
  93. GRB 250515A: GOTO candidate optical counterpart
  94. GRB 250515A: Fermi GBM Final Localization
  95. GRB 250424A: COLIBRÍ detection of the associated supernova
  96. Konus-Wind detection of GRB 250512B / EP250512a
  97. GRB 250502A: TESS observations
  98. GRB 250511A: GECAM-A detection of a short burst
  99. GRB 250509A: Swift-BAT refined analysis
  100. LIGO/Virgo/KAGRA S250328ae: DECam DESGW Candidates (Final Epochs)

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