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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"

35984 results found.

  1. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  2. GRB 250610B: REM optical/NIR observations
  3. GRB 250610B: SVOM/VT optical shallow decay
  4. GRB 250610B: additional Liverpool Telescope optical observations
  5. GRB 250610B: SVOM/GRM analysis
  6. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  7. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  8. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  9. GRB 250610B: Swift-XRT counterpart detection
  10. GRB 250610B: SVOM/VT optical counterpart
  11. GRB 250610B: LT detection of the optical counterpart
  12. GRB 250610B: OHP/T120 optical counterpart candidate
  13. GRB 250610C: Fermi GBM Final Real-time Localization
  14. GRB 250610B: GOTO optical upper limit
  15. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  16. GRB 250610B: SVOM detection of a long burst
  17. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  18. GRB 250610A: Fermi GBM Final Real-time Localization
  19. GRB 250605A: Swift-BAT refined analysis
  20. GRB 250609A: Fermi GBM Observation
  21. GRBAlpha reentry on June 9, 2025
  22. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  23. GRB 250605A: Swift/UVOT Upper Limits
  24. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  25. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  26. GRB 250527C: CrAO Optical Upper Limit
  27. GRB 250609A: Fermi GBM Final Real-time Localization
  28. GRB 250607A: SVOM/GRM observation of a long burst
  29. GRB 250607A: Fermi GBM Final Localization
  30. GRB 250605A: SVOM/VT optical upper limit
  31. GRB 250605A: Swift-XRT refined Analysis
  32. GRB 250605A: Enhanced Swift-XRT position
  33. Fermi GRB 250606A: Global MASTER-Net observations report
  34. GRB 250606A: Fermi GBM Final Real-time Localization
  35. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  36. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  37. GRB 250602A: GECAM detection
  38. GRB 250605A: LT optical observations
  39. GRB 250605A: Swift detection of a burst
  40. Konus-Wind detection of GRB 250601A
  41. IPN triangulation of GRB 250404B
  42. IPN triangulation of GRB 250529A
  43. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  44. GRB 250601A: PRIME H band upper limit.
  45. GRB 250530A: SVOM/GRM analysis
  46. GRB 250601A: PRIME J band upper limit.
  47. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  48. GRB 250601A: VLT/FORS2 Optical Observation
  49. GRB 250601A: Fermi GBM Observation
  50. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  51. GRB 250603A: Swift/UVOT Upper Limits
  52. GRB 250603A: Swift-XRT refined Analysis
  53. GRB 250603A: Enhanced Swift-XRT position
  54. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  55. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  56. GRB 250602A: Fermi GBM Observation
  57. GRB 250602A: Fermi-LAT detection
  58. GRB 250602A: DDOTI Optical Upper Limit
  59. GRB 250530C: Swift-BAT refined analysis
  60. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  61. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  62. GRB 250601A: Swift/XRT candidate afterglow
  63. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  64. GRB 250601A: Swift-XRT observations
  65. Fermi GRB 250601A: Global MASTER-Net observations report
  66. GRB 250602A: Fermi GBM Final Real-time Localization
  67. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  68. GRB 250601A: Swift ToO observations
  69. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  70. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  71. GRB 250601A: Fermi GBM Final Real-time Localization
  72. Fermi GRB 250531A: Global MASTER-Net observations report
  73. GRB 250531A: Fermi GBM Final Real-time Localization
  74. GRB 250530C: BOOTES-7 optical upper limit
  75. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  76. GRB 250530C: Swift-XRT refined Analysis
  77. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  78. Swift GRB 250530C: Global MASTER-Net observations report
  79. GRB 250530C: Enhanced Swift-XRT position
  80. GRB 250530C: Swift detection of a burst
  81. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  82. GRB 250530A: EP-FXT counterpart detection
  83. GRB 250530A: SVOM/VT optical upper limit
  84. Fermi Gamma-ray Burst Monitor trigger 770296643/250530470 is not a GRB
  85. GRB 250530B: Fermi GBM Final Real-time Localization
  86. GRB 250530A: Swift-XRT counterpart detection
  87. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  88. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  89. GRB 250530A: SVOM detection of a burst
  90. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  91. GRB 250527C: Swift/UVOT Upper Limits
  92. GRB 250527D: Swift/BAT-GUANO localization skymap of a burst
  93. GRB 250529B: Fermi GBM Final Real-time Localization
  94. GRB 250527B: Swift-XRT observations
  95. GRB 250529A: Fermi GBM Final Real-time Localization
  96. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  97. GRB 250520A: Swift-BAT refined analysis
  98. GRB 250527C: Swift ToO observations
  99. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  100. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst

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