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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"

11539 results found.

  1. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  2. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  3. GRB 250612C: Fermi GBM Final Real-time Localization
  4. EP250610a: Upper limit from Fermi-GBM Observations
  5. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  6. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  7. Fermi GBM Sub-Threshold Detection of GRB 250610B
  8. GRB 250610B: SVOM/GRM analysis
  9. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  10. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  11. GRB 250610C: Fermi GBM Final Real-time Localization
  12. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  13. GRB 250610A: Fermi GBM Final Real-time Localization
  14. GRB 250609A: Fermi GBM Observation
  15. Fermi trigger No 771072240: Global MASTER-Net observations report
  16. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  17. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  18. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  19. GRB 250527C: CrAO Optical Upper Limit
  20. GRB 250609A: Fermi GBM Final Real-time Localization
  21. GRB 250607A: SVOM/GRM observation of a long burst
  22. GRB 250607A: Fermi GBM Final Localization
  23. Fermi GRB 250606A: Global MASTER-Net observations report
  24. GRB 250606A: Fermi GBM Final Real-time Localization
  25. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  26. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  27. GRB 250602A: GECAM detection
  28. Fermi trigger No 770867684: Global MASTER-Net observations report
  29. Konus-Wind detection of GRB 250601A
  30. IPN triangulation of GRB 250529A
  31. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  32. GRB 250601A: PRIME H band upper limit.
  33. GRB 250601A: PRIME J band upper limit.
  34. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  35. GRB 250601A: VLT/FORS2 Optical Observation
  36. GRB 250601A: Fermi GBM Observation
  37. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  38. Fermi trigger No 770638414: Global MASTER-Net observations report
  39. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  40. GRB 250602A: Fermi GBM Observation
  41. GRB 250602A: Fermi-LAT detection
  42. GRB 250602A: DDOTI Optical Upper Limit
  43. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  44. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  45. GRB 250601A: Swift/XRT candidate afterglow
  46. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  47. Fermi GRB 250601A: Global MASTER-Net observations report
  48. GRB 250602A: Fermi GBM Final Real-time Localization
  49. Fermi trigger No 770470765: Global MASTER-Net observations report
  50. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  51. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  52. GRB 250601A: Fermi GBM Final Real-time Localization
  53. Fermi GRB 250531A: Global MASTER-Net observations report
  54. GRB 250531A: Fermi GBM Final Real-time Localization
  55. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  56. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  57. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  58. GRB 250530B: Fermi GBM Final Real-time Localization
  59. GRB 250529B: Fermi GBM Final Real-time Localization
  60. GRB 250529A: Fermi GBM Final Real-time Localization
  61. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  62. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  63. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  64. Fermi trigger No 770058372: Global MASTER-Net observations report
  65. Fermi trigger No 770047117: Global MASTER-Net observations report
  66. GRB 250527A: Fermi GBM Final Localization
  67. Fermi GRB 250523A: Global MASTER-Net observations report
  68. Fermi trigger No 769611916: Global MASTER-Net observations report
  69. GRB 250521A: GRBAlpha detection
  70. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  71. GRB 250523A: Fermi GBM Final Real-time Localization
  72. Fermi GRB 250522B: Global MASTER-Net observations report
  73. GRB 250522B: Fermi GBM Final Localization
  74. GRB 250521D: SVOM/VT optical observations
  75. GRB 250522A: Fermi GBM Final Real-time Localization
  76. Fermi GRB 250521D: Global MASTER-Net observations report
  77. Fermi trigger No 769533898: Global MASTER-Net observations report
  78. Fermi trigger No 769499303: Global MASTER-Net observations report
  79. GRB 250521D: DDOTI Optical Upper Limit
  80. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  81. GRB 250521D: LAST tentative optical counterpart candidate
  82. GRB 250521D: Fermi GBM Final Real-time Localization
  83. GRB 250521C: Fermi GBM Final Localization
  84. GRB 250521A: DDOTI Optical Upper Limit
  85. GRB 250521A: Fermi GBM Final Real-time Localization
  86. GRB 250520B: Fermi GBM Final Real-time Localization
  87. GRB 250520A: DDOTI Optical Upper Limit
  88. GRB 250520A: AstroSat CZTI detection of a short burst
  89. GRB 250516A: COLIBRÍ optical upper limit
  90. Konus-Wind detection of GRB 250516A
  91. Fermi GRB 250516A: Global MASTER-Net observations report
  92. GRB 250515A: Swift-XRT observations
  93. GRB 250515A: NOT classification of GOTO25cqo as a type-Ia SN
  94. Fermi Gamma-ray Burst Monitor trigger 769160489/250517320 is not a GRB
  95. GRB 250515A:COLIBRÍ optical observations of the GOTO candidate
  96. GRB 250515A: 1.6m Mephisto optical detection
  97. GRB 250516A: AstroSat CZTI detection
  98. GRB 250515A/GOTO25cqo: SVOM/VT optical blue color
  99. GRB 250516A: Fermi GBM Observation
  100. GRB 250515A: Swift ToO observations

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