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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"

37989 results found.

  1. EP250610A: Swift/UVOT Upper limits
  2. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  3. GRB 250610B: REM optical/NIR observations
  4. GRB 250610B: SVOM/VT optical shallow decay
  5. GRB 250610B: additional Liverpool Telescope optical observations
  6. GRB 250610B: SVOM/GRM analysis
  7. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  8. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  9. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  10. GRB 250610B: Swift-XRT counterpart detection
  11. GRB 250610B: SVOM/VT optical counterpart
  12. GRB 250610B: LT detection of the optical counterpart
  13. GRB 250610B: OHP/T120 optical counterpart candidate
  14. GRB 250610C: Fermi GBM Final Real-time Localization
  15. GRB 250610B: GOTO optical upper limit
  16. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  17. GRB 250610B: SVOM detection of a long burst
  18. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  19. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  20. GRB 250610A: Fermi GBM Final Real-time Localization
  21. GRB 250605A: Swift-BAT refined analysis
  22. EP250610a: SVOM/VT optical upper limit
  23. EP250610a: REM optical/NIR observations
  24. GRB 250609A: Fermi GBM Observation
  25. GRBAlpha reentry on June 9, 2025
  26. EP250610a: Swift-XRT counterpart detection
  27. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  28. GRB 250605A: Swift/UVOT Upper Limits
  29. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  30. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  31. GRB 250527C: CrAO Optical Upper Limit
  32. GRB 250609A: Fermi GBM Final Real-time Localization
  33. GRB 250607A: SVOM/GRM observation of a long burst
  34. GRB 250607A: Fermi GBM Final Localization
  35. GRB 250605A: SVOM/VT optical upper limit
  36. GRB 250605A: Swift-XRT refined Analysis
  37. GRB 250605A: Enhanced Swift-XRT position
  38. Fermi GRB 250606A: Global MASTER-Net observations report
  39. GRB 250606A: Fermi GBM Final Real-time Localization
  40. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  41. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  42. GRB 250602A: GECAM detection
  43. GRB 250605A: LT optical observations
  44. GRB 250605A: Swift detection of a burst
  45. Swift GRB250605.79: Global MASTER-Net observations report
  46. Konus-Wind detection of GRB 250601A
  47. IPN triangulation of GRB 250404B
  48. IPN triangulation of GRB 250529A
  49. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  50. GRB 250601A: PRIME H band upper limit.
  51. GRB 250530A: SVOM/GRM analysis
  52. GRB 250601A: PRIME J band upper limit.
  53. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  54. GRB 250601A: VLT/FORS2 Optical Observation
  55. GRB 250601A: Fermi GBM Observation
  56. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  57. GRB 250603A: Swift/UVOT Upper Limits
  58. GRB 250603A: Swift-XRT refined Analysis
  59. GRB 250603A: Enhanced Swift-XRT position
  60. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  61. Swift GRB250603.05: Global MASTER-Net observations report
  62. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  63. GRB 250602A: Fermi GBM Observation
  64. GRB 250602A: Fermi-LAT detection
  65. GRB 250602A: DDOTI Optical Upper Limit
  66. GRB 250530C: Swift-BAT refined analysis
  67. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  68. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  69. GRB 250601A: Swift/XRT candidate afterglow
  70. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  71. GRB 250601A: Swift-XRT observations
  72. Fermi GRB 250601A: Global MASTER-Net observations report
  73. GRB 250602A: Fermi GBM Final Real-time Localization
  74. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  75. GRB 250601A: Swift ToO observations
  76. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  77. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  78. GRB 250601A: Fermi GBM Final Real-time Localization
  79. EP#01709177494: SVOM/VT optical observations
  80. Fermi GRB 250531A: Global MASTER-Net observations report
  81. GRB 250531A: Fermi GBM Final Real-time Localization
  82. EP#01709177494: Swift-XRT counterpart detection of known source
  83. GRB 250530C: BOOTES-7 optical upper limit
  84. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  85. GRB 250530C: Swift-XRT refined Analysis
  86. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  87. Swift GRB 250530C: Global MASTER-Net observations report
  88. GRB 250530C: Enhanced Swift-XRT position
  89. GRB 250530C: Swift detection of a burst
  90. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  91. GRB 250530A: EP-FXT counterpart detection
  92. GRB 250530A: SVOM/VT optical upper limit
  93. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  94. GRB 250530B: Fermi GBM Final Real-time Localization
  95. GRB 250530A: Swift-XRT counterpart detection
  96. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  97. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  98. GRB 250530A: SVOM detection of a burst
  99. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  100. GRB 250527C: Swift/UVOT Upper Limits

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