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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"

23685 results found.

  1. The EP-WXT trigger 01709178244 is likely a flaring star
  2. GRB 250607A: Fermi GBM Final Localization
  3. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  4. The EP-WXT trigger 01709178069 is likely a flaring star
  5. GRB 250605A: SVOM/VT optical upper limit
  6. EP/WXT 01709177873: GOTO observations confirm stellar variability
  7. Fermi GRB 250606A: Global MASTER-Net observations report
  8. GRB 250606A: Fermi GBM Final Real-time Localization
  9. Fermi trigger No 770867684: Global MASTER-Net observations report
  10. The EP-WXT trigger 01709177873 is likely a flaring star
  11. Swift GRB250605.79: Global MASTER-Net observations report
  12. Konus-Wind detection of GRB 250601A
  13. IPN triangulation of GRB 250404B
  14. IPN triangulation of GRB 250529A
  15. The EP-WXT trigger 01709177837 is likely a flaring star
  16. GRB 250601A: PRIME H band upper limit.
  17. GRB 250530A: SVOM/GRM analysis
  18. GRB 250601A: PRIME J band upper limit.
  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. Swift GRB250603.05: Global MASTER-Net observations report
  23. GRB 250602A: Fermi GBM Observation
  24. GRB 250602A: Fermi-LAT detection
  25. GRB 250530C: Swift-BAT refined analysis
  26. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  27. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  28. GRB 250601A: Swift-XRT observations
  29. Fermi GRB 250601A: Global MASTER-Net observations report
  30. GRB 250602A: Fermi GBM Final Real-time Localization
  31. Fermi trigger No 770470765: Global MASTER-Net observations report
  32. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  33. GRB 250601A: Fermi GBM Final Real-time Localization
  34. EP#01709177494: SVOM/VT optical observations
  35. Fermi GRB 250531A: Global MASTER-Net observations report
  36. GRB 250531A: Fermi GBM Final Real-time Localization
  37. GRB 250530C: BOOTES-7 optical upper limit
  38. Swift GRB 250530C: Global MASTER-Net observations report
  39. GRB 250530C: Swift detection of a burst
  40. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  41. GRB 250530A: EP-FXT counterpart detection
  42. GRB 250530A: SVOM/VT optical upper limit
  43. GRB 250530B: Fermi GBM Final Real-time Localization
  44. GRB 250530A: SVOM detection of a burst
  45. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  46. GRB 250527C: Swift/UVOT Upper Limits
  47. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  48. EP J1350.0-8622: EP-FXT follow-up observation
  49. GRB 250529B: Fermi GBM Final Real-time Localization
  50. GRB 250527B: Swift-XRT observations
  51. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  52. The EP-WXT trigger 01709177124 is likely a flaring star
  53. GRB 250529A: Fermi GBM Final Real-time Localization
  54. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  55. GRB 250520A: Swift-BAT refined analysis
  56. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  57. EP250526a: SVOM/VT optical upper limit
  58. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  59. GRB 250520A: Gemini-South optical afterglow detection
  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: refined analysis of the EP-WXT and EP-FXT observations
  64. GRB 250314A: CIDER NB1008 upper limit
  65. EP250526a: Global MASTER-Net observations report
  66. GRB 250520A: 3 GHz MeerKAT Detection
  67. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  68. Fermi GRB 250523A: Global MASTER-Net observations report
  69. Fermi trigger No 769611916: Global MASTER-Net observations report
  70. GRB 250521A: GRBAlpha detection
  71. GRB 250520A: GRBAlpha detection
  72. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  73. GRB 250523A: Fermi GBM Final Real-time Localization
  74. The EP-WXT trigger 01709176712 is likely a flaring star
  75. GRB 250521B: SVOM/VT optical upper limit
  76. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  77. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  78. Fermi GRB 250522B: Global MASTER-Net observations report
  79. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  80. GRB 250522B: Fermi GBM Final Localization
  81. GRB 250521D: SVOM/VT optical observations
  82. GRB 250522A: Fermi GBM Final Real-time Localization
  83. Fermi GRB 250521D: Global MASTER-Net observations report
  84. Fermi trigger No 769533898: Global MASTER-Net observations report
  85. Fermi trigger No 769499303: Global MASTER-Net observations report
  86. The EP-WXT trigger 01709176612 is likely a flaring star
  87. GRB 250521D: LAST tentative optical counterpart candidate
  88. GRB 250520A: 10 GHz VLA radio source
  89. GRB 250521D: Fermi GBM Final Real-time Localization
  90. GRB 250521C: Fermi GBM Final Localization
  91. GRB 250521B: SVOM detection of a burst through offline search
  92. Konus-Wind detection of GRB 250520A (short/hard)
  93. GRB 250521A: Fermi GBM Final Real-time Localization
  94. Konus-Wind detection of GRB 250516B
  95. IPN triangulation of GRB 250516B
  96. GRB 250520A: J-band observations with WINTER
  97. GRB 250520A: Gemini-South optical observations
  98. GRB 250520A: REM optical/NIR early observations
  99. GRB 250520B: Fermi GBM Final Real-time Localization
  100. GRB 250520A：SVOM/VT optical candidate

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