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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"

32411 results found.

  1. GRB 250615A: Enhanced Swift-XRT position
  2. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  3. GRB 250615A: Prompt enhanced Swift-XRT position
  4. GRB 250615A: Swift detection of a burst
  5. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  6. GRID detection of GRB 250612C
  7. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  8. GRB 250614A: Fermi GBM Final Real-time Localization
  9. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  10. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  11. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  12. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  13. GRB 250612B: Fermi GBM Observation
  14. GRB 250612C: Fermi GBM Observation
  15. EP250612a/GRB 250612B: JinShan optical upper limit
  16. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  17. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  18. GRB 250610B: Swift-XRT refined Analysis
  19. GRB 250612C: Fermi GBM Final Real-time Localization
  20. EP250610a: Upper limit from Fermi-GBM Observations
  21. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  22. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  23. GRB 250610B: Liverpool Telescope continued monitoring
  24. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  25. GRB 250610B - SVOM/ECLAIRs refined analysis
  26. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  27. Fermi GBM Sub-Threshold Detection of GRB 250610B
  28. GRB 250610B: Swift/UVOT Detection
  29. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  30. GRB 250610B: REM optical/NIR observations
  31. GRB 250610B: SVOM/VT optical shallow decay
  32. GRB 250610B: additional Liverpool Telescope optical observations
  33. GRB 250610B: SVOM/GRM analysis
  34. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  35. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  36. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  37. GRB 250610B: Swift-XRT counterpart detection
  38. GRB 250610B: SVOM/VT optical counterpart
  39. GRB 250610B: LT detection of the optical counterpart
  40. GRB 250610B: OHP/T120 optical counterpart candidate
  41. GRB 250610C: Fermi GBM Final Real-time Localization
  42. GRB 250610B: GOTO optical upper limit
  43. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  44. GRB 250610B: SVOM detection of a long burst
  45. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  46. GRB 250610A: Fermi GBM Final Real-time Localization
  47. GRB 250605A: Swift-BAT refined analysis
  48. GRB 250609A: Fermi GBM Observation
  49. GRBAlpha reentry on June 9, 2025
  50. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  51. GRB 250605A: Swift/UVOT Upper Limits
  52. GRB 250608A: SVOM/GRM detection of a possible magnetar X-ray burst
  53. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  54. GRB 250527C: CrAO Optical Upper Limit
  55. GRB 250609A: Fermi GBM Final Real-time Localization
  56. GRB 250607A: SVOM/GRM observation of a long burst
  57. GRB 250607A: Fermi GBM Final Localization
  58. GRB 250605A: SVOM/VT optical upper limit
  59. GRB 250605A: Swift-XRT refined Analysis
  60. GRB 250605A: Enhanced Swift-XRT position
  61. Fermi GRB 250606A: Global MASTER-Net observations report
  62. GRB 250606A: Fermi GBM Final Real-time Localization
  63. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  64. Fermi Gamma-ray Burst Monitor trigger 770867684/250606080 is not a GRB
  65. GRB 250602A: GECAM detection
  66. GRB 250605A: LT optical observations
  67. GRB 250605A: Swift detection of a burst
  68. Konus-Wind detection of GRB 250601A
  69. IPN triangulation of GRB 250404B
  70. IPN triangulation of GRB 250529A
  71. Fermi Gamma-ray Burst Monitor trigger 770470765/250601486 is not a GRB
  72. GRB 250601A: PRIME H band upper limit.
  73. GRB 250530A: SVOM/GRM analysis
  74. GRB 250601A: PRIME J band upper limit.
  75. Fermi Gamma-ray Burst Monitor trigger 770675211/250603852 is not a GRB
  76. GRB 250601A: VLT/FORS2 Optical Observation
  77. GRB 250601A: Fermi GBM Observation
  78. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  79. GRB 250603A: Swift/UVOT Upper Limits
  80. GRB 250603A: Swift-XRT refined Analysis
  81. GRB 250603A: Enhanced Swift-XRT position
  82. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  83. GRB 250603A: Swift detection of a burst or new Galactic transient Swift J0839.7-3916
  84. GRB 250602A: Fermi GBM Observation
  85. GRB 250602A: Fermi-LAT detection
  86. GRB 250602A: DDOTI Optical Upper Limit
  87. GRB 250530C: Swift-BAT refined analysis
  88. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  89. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  90. GRB 250601A: Swift/XRT candidate afterglow
  91. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  92. GRB 250601A: Swift-XRT observations
  93. Fermi GRB 250601A: Global MASTER-Net observations report
  94. GRB 250602A: Fermi GBM Final Real-time Localization
  95. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  96. GRB 250601A: Swift ToO observations
  97. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  98. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  99. GRB 250601A: Fermi GBM Final Real-time Localization
  100. Fermi GRB 250531A: Global MASTER-Net observations report

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