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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"

11612 results found.

  1. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  2. GRB 250527C: CrAO Optical Upper Limit
  3. GRB 250609A: Fermi GBM Final Real-time Localization
  4. GRB 250607A: SVOM/GRM observation of a long burst
  5. GRB 250607A: Fermi GBM Final Localization
  6. Fermi GRB 250606A: Global MASTER-Net observations report
  7. GRB 250606A: Fermi GBM Final Real-time Localization
  8. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  9. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  10. GRB 250602A: GECAM detection
  11. Fermi trigger No 770867684: Global MASTER-Net observations report
  12. Konus-Wind detection of GRB 250601A
  13. IPN triangulation of GRB 250529A
  14. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  15. GRB 250601A: PRIME H band upper limit.
  16. GRB 250601A: PRIME J band upper limit.
  17. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  18. GRB 250601A: VLT/FORS2 Optical Observation
  19. GRB 250601A: Fermi GBM Observation
  20. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  21. Fermi trigger No 770638414: Global MASTER-Net observations report
  22. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  23. GRB 250602A: Fermi GBM Observation
  24. GRB 250602A: Fermi-LAT detection
  25. GRB 250602A: DDOTI Optical Upper Limit
  26. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  27. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  28. GRB 250601A: Swift/XRT candidate afterglow
  29. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  30. Fermi GRB 250601A: Global MASTER-Net observations report
  31. GRB 250602A: Fermi GBM Final Real-time Localization
  32. Fermi trigger No 770470765: Global MASTER-Net observations report
  33. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  34. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  35. GRB 250601A: Fermi GBM Final Real-time Localization
  36. Fermi GRB 250531A: Global MASTER-Net observations report
  37. GRB 250531A: Fermi GBM Final Real-time Localization
  38. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  39. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  40. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  41. GRB 250530B: Fermi GBM Final Real-time Localization
  42. GRB 250529B: Fermi GBM Final Real-time Localization
  43. GRB 250529A: Fermi GBM Final Real-time Localization
  44. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  45. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  46. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  47. Fermi trigger No 770058372: Global MASTER-Net observations report
  48. Fermi trigger No 770047117: Global MASTER-Net observations report
  49. GRB 250527A: Fermi GBM Final Localization
  50. Fermi GRB 250523A: Global MASTER-Net observations report
  51. Fermi trigger No 769611916: Global MASTER-Net observations report
  52. GRB 250521A: GRBAlpha detection
  53. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  54. GRB 250523A: Fermi GBM Final Real-time Localization
  55. Fermi GRB 250522B: Global MASTER-Net observations report
  56. GRB 250522B: Fermi GBM Final Localization
  57. GRB 250521D: SVOM/VT optical observations
  58. GRB 250522A: Fermi GBM Final Real-time Localization
  59. Fermi GRB 250521D: Global MASTER-Net observations report
  60. Fermi trigger No 769533898: Global MASTER-Net observations report
  61. Fermi trigger No 769499303: Global MASTER-Net observations report
  62. GRB 250521D: DDOTI Optical Upper Limit
  63. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  64. GRB 250521D: LAST tentative optical counterpart candidate
  65. GRB 250521D: Fermi GBM Final Real-time Localization
  66. GRB 250521C: Fermi GBM Final Localization
  67. GRB 250521A: DDOTI Optical Upper Limit
  68. GRB 250521A: Fermi GBM Final Real-time Localization
  69. GRB 250520B: Fermi GBM Final Real-time Localization
  70. GRB 250520A: DDOTI Optical Upper Limit
  71. GRB 250520A: AstroSat CZTI detection of a short burst
  72. GRB 250516A: COLIBRÍ optical upper limit
  73. Konus-Wind detection of GRB 250516A
  74. Fermi GRB 250516A: Global MASTER-Net observations report
  75. GRB 250515A: Swift-XRT observations
  76. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  77. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  78. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  79. GRB 250515A: 1.6m Mephisto optical detection
  80. GRB 250516A: AstroSat CZTI detection
  81. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  82. GRB 250516A: Fermi GBM Observation
  83. GRB 250515A: Swift ToO observations
  84. GRB 250516A: Fermi GBM Final Real-time Localization
  85. GRB 250515A: GOTO candidate optical counterpart
  86. GRB 250515A: Fermi GBM Final Localization
  87. Fermi trigger No 768922089: Global MASTER-Net observations report
  88. Fermi GRB 250512A: Global MASTER-Net observations report
  89. Konus-Wind detection of GRB 250506A
  90. GRB 250506A: GRBAlpha detection
  91. GRB 250512A: Fermi GBM Final Real-time Localization
  92. GRB 250510B: Fermi GBM Observation
  93. Fermi GRB 250510C: Global MASTER-Net observations report
  94. Fermi GRB 250510B: Global MASTER-Net observations report
  95. GRB 250510C: Fermi GBM Final Real-time Localization
  96. GRB 250509A: Fermi GBM Observation
  97. GRB 250510B: Swift/BAT-GUANO localization skymap of a burst
  98. GRB 250510B: Fermi GBM Final Localization
  99. Fermi GRB 250509A: Global MASTER-Net observations report
  100. GRB 250509A: Fermi GBM Final Real-time Localization

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