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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"

24378 results found.

  1. GRB 250606A: Fermi GBM Final Real-time Localization
  2. Fermi trigger No 770867684: Global MASTER-Net observations report
  3. The EP-WXT trigger 01709177873 is likely a flaring star
  4. Swift GRB250605.79: Global MASTER-Net observations report
  5. Konus-Wind detection of GRB 250601A
  6. IPN triangulation of GRB 250404B
  7. IPN triangulation of GRB 250529A
  8. The EP-WXT trigger 01709177837 is likely a flaring star
  9. GRB 250601A: PRIME H band upper limit.
  10. GRB 250530A: SVOM/GRM analysis
  11. GRB 250601A: PRIME J band upper limit.
  12. GRB 250601A: Fermi GBM Observation
  13. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  14. Fermi trigger No 770638414: Global MASTER-Net observations report
  15. Swift GRB250603.05: Global MASTER-Net observations report
  16. GRB 250602A: Fermi GBM Observation
  17. GRB 250602A: Fermi-LAT detection
  18. GRB 250530C: Swift-BAT refined analysis
  19. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  20. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  21. GRB 250601A: Swift-XRT observations
  22. Fermi GRB 250601A: Global MASTER-Net observations report
  23. GRB 250602A: Fermi GBM Final Real-time Localization
  24. Fermi trigger No 770470765: Global MASTER-Net observations report
  25. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  26. GRB 250601A: Fermi GBM Final Real-time Localization
  27. EP#01709177494: SVOM/VT optical observations
  28. Fermi GRB 250531A: Global MASTER-Net observations report
  29. GRB 250531A: Fermi GBM Final Real-time Localization
  30. GRB 250530C: BOOTES-7 optical upper limit
  31. Swift GRB 250530C: Global MASTER-Net observations report
  32. GRB 250530C: Swift detection of a burst
  33. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  34. GRB 250530A: EP-FXT counterpart detection
  35. GRB 250530A: SVOM/VT optical upper limit
  36. GRB 250530B: Fermi GBM Final Real-time Localization
  37. GRB 250530A: SVOM detection of a burst
  38. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  39. GRB 250527C: Swift/UVOT Upper Limits
  40. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  41. EP J1350.0-8622: EP-FXT follow-up observation
  42. GRB 250529B: Fermi GBM Final Real-time Localization
  43. GRB 250527B: Swift-XRT observations
  44. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  45. The EP-WXT trigger 01709177124 is likely a flaring star
  46. GRB 250529A: Fermi GBM Final Real-time Localization
  47. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  48. GRB 250520A: Swift-BAT refined analysis
  49. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  50. EP250526a: SVOM/VT optical upper limit
  51. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  52. GRB 250520A: Gemini-South optical afterglow detection
  53. Fermi trigger No 770058372: Global MASTER-Net observations report
  54. Fermi trigger No 770047117: Global MASTER-Net observations report
  55. GRB 250527A: Fermi GBM Final Localization
  56. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  57. GRB 250314A: CIDER NB1008 upper limit
  58. EP250526a: Global MASTER-Net observations report
  59. GRB 250520A: 3 GHz MeerKAT Detection
  60. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  61. Fermi GRB 250523A: Global MASTER-Net observations report
  62. Fermi trigger No 769611916: Global MASTER-Net observations report
  63. GRB 250521A: GRBAlpha detection
  64. GRB 250520A: GRBAlpha detection
  65. GRB 250523A: BALROG localization (Fermi Trigger 769703188 / GRB 250523602)
  66. GRB 250523A: Fermi GBM Final Real-time Localization
  67. The EP-WXT trigger 01709176712 is likely a flaring star
  68. GRB 250521B: SVOM/VT optical upper limit
  69. The EP-WXT trigger 01709176612: SVOM/VT optical observations
  70. The EP-WXT trigger 01709176612: refined analysis of the EP-FXT observation
  71. Fermi GRB 250522B: Global MASTER-Net observations report
  72. GRB 250521B: EP-FXT follow-up observation and afterglow candidates
  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. The EP-WXT trigger 01709176612 is likely a flaring star
  80. GRB 250521D: LAST tentative optical counterpart candidate
  81. GRB 250520A: 10 GHz VLA radio source
  82. GRB 250521D: Fermi GBM Final Real-time Localization
  83. GRB 250521C: Fermi GBM Final Localization
  84. GRB 250521B: SVOM detection of a burst through offline search
  85. Konus-Wind detection of GRB 250520A (short/hard)
  86. GRB 250521A: Fermi GBM Final Real-time Localization
  87. Konus-Wind detection of GRB 250516B
  88. IPN triangulation of GRB 250516B
  89. GRB 250520A: J-band observations with WINTER
  90. GRB 250520A: Gemini-South optical observations
  91. GRB 250520A: REM optical/NIR early observations
  92. GRB 250520B: Fermi GBM Final Real-time Localization
  93. GRB 250520A:SVOM/VT optical candidate
  94. GRB 250516B: GRBAlpha detection
  95. GRB 250520A: SVOM/GRM observation
  96. Swift GRB 250520A: Global MASTER-Net observations report
  97. EP250427a/GRB250427A: VLA Detection of Radio Counterpart
  98. GRB 250516A: Swift-BAT refined analysis
  99. Konus-Wind detection of GRB 250516A
  100. GRB 250516B: NuSTAR Detection of the Prompt Emission

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