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GCN Circulars

GCN Circulars are rapid bulletins submitted by and distributed to the community. 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"

45941 results found.

  1. GRBAlpha reentry on June 9, 2025
  2. EP250610a: Swift-XRT counterpart detection
  3. EP250610a: COLIBRÍ optical upper limit
  4. EP250610a: Einstein Probe detection of an X-ray transient
  5. Fermi trigger No 771072240: Global MASTER-Net observations report
  6. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  7. GRB 250605A: Swift/UVOT Upper Limits
  8. The EP-WXT trigger 01709178283 is likely a flaring star
  9. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  10. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  11. GRB 250527C: CrAO Optical Upper Limit
  12. GRB 250609A: Fermi GBM Final Real-time Localization
  13. GRB 250607A: SVOM/GRM observation of a long burst
  14. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  15. The EP-WXT trigger 01709178244 is likely a flaring star
  16. GRB 250607A: Fermi GBM Final Localization
  17. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  18. The EP-WXT trigger 01709178069 is likely a flaring star
  19. GRB 250605A: SVOM/VT optical upper limit
  20. GRB 250605A: Swift-XRT refined Analysis
  21. EP/WXT 01709177873: GOTO observations confirm stellar variability
  22. GRB 250605A: Enhanced Swift-XRT position
  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. The EP-WXT trigger 01709177873 is likely a flaring star
  30. GRB 250605A: LT optical observations
  31. GRB 250605A: Swift detection of a burst
  32. Swift GRB250605.79: Global MASTER-Net observations report
  33. Konus-Wind detection of GRB 250601A
  34. IPN triangulation of GRB 250404B
  35. IPN triangulation of GRB 250529A
  36. The EP-WXT trigger 01709177837 is likely a flaring star
  37. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  38. GRB 250601A: PRIME H band upper limit.
  39. GRB 250530A: SVOM/GRM analysis
  40. GRB 250601A: PRIME J band upper limit.
  41. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  42. GRB 250601A: VLT/FORS2 Optical Observation
  43. GRB 250601A: Fermi GBM Observation
  44. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  45. GRB 250603A: Swift/UVOT Upper Limits
  46. GRB 250603A: Swift-XRT refined Analysis
  47. Fermi trigger No 770638414: Global MASTER-Net observations report
  48. GRB 250603A: Enhanced Swift-XRT position
  49. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  50. Swift GRB250603.05: Global MASTER-Net observations report
  51. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  52. GRB 250602A: Fermi GBM Observation
  53. GRB 250602A: Fermi-LAT detection
  54. GRB 250602A: DDOTI Optical Upper Limit
  55. GRB 250530C: Swift-BAT refined analysis
  56. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  57. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  58. GRB 250601A: Swift/XRT candidate afterglow
  59. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  60. GRB 250601A: Swift-XRT observations
  61. Fermi GRB 250601A: Global MASTER-Net observations report
  62. GRB 250602A: Fermi GBM Final Real-time Localization
  63. Fermi trigger No 770470765: Global MASTER-Net observations report
  64. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  65. GRB 250601A: Swift ToO observations
  66. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  67. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  68. GRB 250601A: Fermi GBM Final Real-time Localization
  69. EP#01709177494: SVOM/VT optical observations
  70. Fermi GRB 250531A: Global MASTER-Net observations report
  71. GRB 250531A: Fermi GBM Final Real-time Localization
  72. EP#01709177494: Swift-XRT counterpart detection of known source
  73. GRB 250530C: BOOTES-7 optical upper limit
  74. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  75. GRB 250530C: Swift-XRT refined Analysis
  76. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  77. Swift GRB 250530C: Global MASTER-Net observations report
  78. GRB 250530C: Enhanced Swift-XRT position
  79. GRB 250530C: Swift detection of a burst
  80. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  81. GRB 250530A: EP-FXT counterpart detection
  82. GRB 250530A: SVOM/VT optical upper limit
  83. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  84. GRB 250530B: Fermi GBM Final Real-time Localization
  85. GRB 250530A: Swift-XRT counterpart detection
  86. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  87. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  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. GRB 250527B: Swift-XRT observations
  95. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  96. The EP-WXT trigger 01709177124 is likely a flaring star
  97. GRB 250529A: Fermi GBM Final Real-time Localization
  98. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  99. GRB 250520A: Swift-BAT refined analysis
  100. GRB 250527C: Swift ToO observations

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