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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"

26234 results found.

  1. GRB 250610B: SVOM/VT optical counterpart
  2. GRB 250610B: LT detection of the optical counterpart
  3. GRB 250610B: OHP/T120 optical counterpart candidate
  4. GRB 250610C: Fermi GBM Final Real-time Localization
  5. GRB 250610B: GOTO optical upper limit
  6. EP250610a: Global MASTER-Net observations report
  7. GRB 250610B: SVOM detection of a long burst
  8. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  9. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  10. GRB 250610A: Fermi GBM Final Real-time Localization
  11. GRB 250605A: Swift-BAT refined analysis
  12. EP250610a: SVOM/VT optical upper limit
  13. EP250610a: REM optical/NIR observations
  14. GRB 250609A: Fermi GBM Observation
  15. EP250610a: Swift-XRT counterpart detection
  16. EP250610a: COLIBRÍ optical upper limit
  17. EP250610a: Einstein Probe detection of an X-ray transient
  18. Fermi trigger No 771072240: Global MASTER-Net observations report
  19. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  20. GRB 250605A: Swift/UVOT Upper Limits
  21. The EP-WXT trigger 01709178283 is likely a flaring star
  22. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  23. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  24. GRB 250527C: CrAO Optical Upper Limit
  25. GRB 250609A: Fermi GBM Final Real-time Localization
  26. GRB 250607A: SVOM/GRM observation of a long burst
  27. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  28. The EP-WXT trigger 01709178244 is likely a flaring star
  29. GRB 250607A: Fermi GBM Final Localization
  30. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  31. The EP-WXT trigger 01709178069 is likely a flaring star
  32. GRB 250605A: SVOM/VT optical upper limit
  33. GRB 250605A: Swift-XRT refined Analysis
  34. EP/WXT 01709177873: GOTO observations confirm stellar variability
  35. Fermi GRB 250606A: Global MASTER-Net observations report
  36. GRB 250606A: Fermi GBM Final Real-time Localization
  37. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  38. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  39. GRB 250602A: GECAM detection
  40. Fermi trigger No 770867684: Global MASTER-Net observations report
  41. The EP-WXT trigger 01709177873 is likely a flaring star
  42. GRB 250605A: LT optical observations
  43. GRB 250605A: Swift detection of a burst
  44. Swift GRB250605.79: Global MASTER-Net observations report
  45. Konus-Wind detection of GRB 250601A
  46. The EP-WXT trigger 01709177837 is likely a flaring star
  47. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  48. GRB 250601A: PRIME H band upper limit.
  49. GRB 250530A: SVOM/GRM analysis
  50. GRB 250601A: PRIME J band upper limit.
  51. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  52. GRB 250601A: VLT/FORS2 Optical Observation
  53. GRB 250601A: Fermi GBM Observation
  54. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  55. GRB 250603A: Swift/UVOT Upper Limits
  56. GRB 250603A: Swift-XRT refined Analysis
  57. Fermi trigger No 770638414: Global MASTER-Net observations report
  58. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  59. Swift GRB250603.05: Global MASTER-Net observations report
  60. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  61. GRB 250602A: Fermi GBM Observation
  62. GRB 250602A: Fermi-LAT detection
  63. GRB 250602A: DDOTI Optical Upper Limit
  64. GRB 250530C: Swift-BAT refined analysis
  65. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  66. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  67. Fermi GRB 250601A: Global MASTER-Net observations report
  68. GRB 250602A: Fermi GBM Final Real-time Localization
  69. Fermi trigger No 770470765: Global MASTER-Net observations report
  70. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  71. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  72. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  73. GRB 250601A: Fermi GBM Final Real-time Localization
  74. EP#01709177494: SVOM/VT optical observations
  75. Fermi GRB 250531A: Global MASTER-Net observations report
  76. GRB 250531A: Fermi GBM Final Real-time Localization
  77. EP#01709177494: Swift-XRT counterpart detection of known source
  78. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  79. GRB 250530C: Swift-XRT refined Analysis
  80. Swift GRB 250530C: Global MASTER-Net observations report
  81. GRB 250530C: Swift detection of a burst
  82. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  83. GRB 250530A: EP-FXT counterpart detection
  84. GRB 250530A: SVOM/VT optical upper limit
  85. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  86. GRB 250530B: Fermi GBM Final Real-time Localization
  87. GRB 250530A: Swift-XRT counterpart detection
  88. GRB 250530A: SVOM detection of a burst
  89. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  90. GRB 250527C: Swift/UVOT Upper Limits
  91. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  92. EP J1350.0-8622: EP-FXT follow-up observation
  93. GRB 250529B: Fermi GBM Final Real-time Localization
  94. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  95. The EP-WXT trigger 01709177124 is likely a flaring star
  96. GRB 250529A: Fermi GBM Final Real-time Localization
  97. GRB 250520A: Swift-BAT refined analysis
  98. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  99. EP250526a: SVOM/VT optical upper limit
  100. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst

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