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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"

24167 results found.

  1. Swift GRB250605.79: Global MASTER-Net observations report
  2. Konus-Wind detection of GRB 250601A
  3. IPN triangulation of GRB 250404B
  4. IPN triangulation of GRB 250529A
  5. The EP-WXT trigger 01709177837 is likely a flaring star
  6. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  7. GRB 250601A: PRIME H band upper limit.
  8. GRB 250601A: PRIME J band upper limit.
  9. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  10. GRB 250601A: VLT/FORS2 Optical Observation
  11. GRB 250601A: Fermi GBM Observation
  12. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  13. GRB 250603A: Swift/UVOT Upper Limits
  14. GRB 250603A: Swift-XRT refined Analysis
  15. Fermi trigger No 770638414: Global MASTER-Net observations report
  16. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  17. Swift GRB250603.05: Global MASTER-Net observations report
  18. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  19. GRB 250602A: Fermi GBM Observation
  20. GRB 250602A: Fermi-LAT detection
  21. GRB 250602A: DDOTI Optical Upper Limit
  22. GRB 250530C: Swift-BAT refined analysis
  23. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  24. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  25. GRB 250601A: Swift/XRT candidate afterglow
  26. GRB 250601A: Swift-XRT observations
  27. Fermi GRB 250601A: Global MASTER-Net observations report
  28. GRB 250602A: Fermi GBM Final Real-time Localization
  29. Fermi trigger No 770470765: Global MASTER-Net observations report
  30. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  31. GRB 250601A: Swift ToO observations
  32. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  33. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  34. GRB 250601A: Fermi GBM Final Real-time Localization
  35. EP#01709177494: SVOM/VT optical observations
  36. Fermi GRB 250531A: Global MASTER-Net observations report
  37. GRB 250531A: Fermi GBM Final Real-time Localization
  38. EP#01709177494: Swift-XRT counterpart detection of known source
  39. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  40. GRB 250530C: Swift-XRT refined Analysis
  41. Swift GRB 250530C: Global MASTER-Net observations report
  42. GRB 250530C: Swift detection of a burst
  43. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  44. GRB 250530A: EP-FXT counterpart detection
  45. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  46. GRB 250530B: Fermi GBM Final Real-time Localization
  47. GRB 250530A: Swift-XRT counterpart detection
  48. GRB 250530A: SVOM detection of a burst
  49. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  50. GRB 250527C: Swift/UVOT Upper Limits
  51. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  52. GRB 250529B: Fermi GBM Final Real-time Localization
  53. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  54. The EP-WXT trigger 01709177124 is likely a flaring star
  55. GRB 250529A: Fermi GBM Final Real-time Localization
  56. GRB 250520A: Swift-BAT refined analysis
  57. GRB 250527C: Swift ToO observations
  58. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  59. EP250526a: SVOM/VT optical upper limit
  60. Fermi trigger No 770058372: Global MASTER-Net observations report
  61. Fermi trigger No 770047117: Global MASTER-Net observations report
  62. GRB 250527A: Fermi GBM Final Localization
  63. EP250526a: COLIBRÍ optical upper limits
  64. EP250526a: Global MASTER-Net observations report
  65. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  66. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  67. Fermi GRB 250523A: Global MASTER-Net observations report
  68. Fermi trigger No 769611916: Global MASTER-Net observations report
  69. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  70. GRB 250520A: GRBAlpha detection
  71. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  72. GRB 250523A: Fermi GBM Final Real-time Localization
  73. The EP-WXT trigger 01709176712 is likely a flaring star
  74. GRB 250521B: SVOM/VT optical upper limit
  75. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  76. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  77. Fermi GRB 250522B: Global MASTER-Net observations report
  78. GRB 250522B: Fermi GBM Final Localization
  79. GRB 250521D: SVOM/VT optical observations
  80. GRB 250522A: Fermi GBM Final Real-time Localization
  81. EP#01709176612: Swift-XRT counterpart detection of flaring star
  82. Fermi GRB 250521D: Global MASTER-Net observations report
  83. Fermi trigger No 769533898: Global MASTER-Net observations report
  84. Fermi trigger No 769499303: Global MASTER-Net observations report
  85. GRB 250521D: DDOTI Optical Upper Limit
  86. The EP-WXT trigger 01709176612 is likely a flaring star
  87. GRB 250521D: GOTO detects LAST counterpart candidate prior to the GRB
  88. GRB 250521B: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  89. GRB 250521D: LAST tentative optical counterpart candidate
  90. GRB 250521D: Fermi GBM Final Real-time Localization
  91. GRB 250521C: Fermi GBM Final Localization
  92. GRB 250521A: DDOTI Optical Upper Limit
  93. GRB 250521B: SVOM detection of a burst through offline search
  94. GRB 250520A: VLT/FORS2 Optical Observation
  95. GRB 250502A: Tautenburg observations
  96. GRB 250520A: Swift/UVOT Upper Limits
  97. GRB 250521A: Fermi GBM Final Real-time Localization
  98. IPN triangulation of GRB 250516B
  99. GRB 250520A: Swift-XRT refined Analysis
  100. GRB 250520A: REM optical/NIR early observations

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