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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"

32510 results found.

  1. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  2. GRB 250610B: Liverpool Telescope continued monitoring
  3. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  4. EP250610a: continuous follow-up observations with EP-FXT
  5. GRB 250610B - SVOM/ECLAIRs refined analysis
  6. Fermi GBM Sub-Threshold Detection of GRB 250610B
  7. GRB 250610B: Swift/UVOT Detection
  8. EP250610A: Swift/UVOT Upper limits
  9. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  10. EP250610a: TNG NIR upper limit
  11. GRB 250610B: REM optical/NIR observations
  12. EP250610a: Liverpool Telescope optical upper limits
  13. GRB 250610B: SVOM/VT optical shallow decay
  14. GRB 250610B: additional Liverpool Telescope optical observations
  15. GRB 250610B: SVOM/GRM analysis
  16. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  17. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  18. GRB 250610B: Swift-XRT counterpart detection
  19. GRB 250610B: SVOM/VT optical counterpart
  20. GRB 250610B: LT detection of the optical counterpart
  21. GRB 250610B: OHP/T120 optical counterpart candidate
  22. GRB 250610B: GOTO optical upper limit
  23. EP250610a: Global MASTER-Net observations report
  24. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  25. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 250605A: Swift-BAT refined analysis
  27. EP250610a: SVOM/VT optical upper limit
  28. EP250610a: REM optical/NIR observations
  29. GRB 250609A: Fermi GBM Observation
  30. EP250610a: COLIBRÍ optical upper limit
  31. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  32. GRB 250605A: Swift/UVOT Upper Limits
  33. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  34. GRB 250527C: CrAO Optical Upper Limit
  35. GRB 250607A: SVOM/GRM observation of a long burst
  36. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  37. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  38. GRB 250605A: SVOM/VT optical upper limit
  39. Fermi GRB 250606A: Global MASTER-Net observations report
  40. GRB 250602A: GECAM detection
  41. GRB 250605A: LT optical observations
  42. Konus-Wind detection of GRB 250601A
  43. IPN triangulation of GRB 250404B
  44. IPN triangulation of GRB 250529A
  45. GRB 250601A: PRIME H band upper limit.
  46. GRB 250530A: SVOM/GRM analysis
  47. GRB 250601A: PRIME J band upper limit.
  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 position and confirmation of GRB nature
  53. GRB 250602A: Fermi GBM Observation
  54. GRB 250602A: Fermi-LAT detection
  55. GRB 250602A: DDOTI Optical Upper Limit
  56. GRB 250530C: Swift-BAT refined analysis
  57. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  58. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  59. GRB 250601A: Swift/XRT candidate afterglow
  60. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  61. Fermi GRB 250601A: Global MASTER-Net observations report
  62. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  63. GRB 250601A: Swift ToO observations
  64. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  65. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  66. EP#01709177494: SVOM/VT optical observations
  67. Fermi GRB 250531A: Global MASTER-Net observations report
  68. GRB 250530C: BOOTES-7 optical upper limit
  69. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  70. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  71. Swift GRB 250530C: Global MASTER-Net observations report
  72. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  73. GRB 250530A: EP-FXT counterpart detection
  74. GRB 250530A: SVOM/VT optical upper limit
  75. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  76. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  77. GRB 250527D: CALET Gamma-Ray Burst Monitor detection
  78. GRB 250527C: Swift/UVOT Upper Limits
  79. EP J1350.0-8622: EP-FXT follow-up observation
  80. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  81. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  82. GRB 250520A: Swift-BAT refined analysis
  83. GRB 250527C: Swift ToO observations
  84. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  85. EP250526a: SVOM/VT optical upper limit
  86. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  87. GRB 250527B: Tiled Swift observations
  88. GRB 250520A: Gemini-South optical afterglow detection
  89. EP250526a: refined analysis of the EP-WXT and EP-FXT observations
  90. GRB 250314A: CIDER NB1008 upper limit
  91. EP250526a: COLIBRÍ optical upper limits
  92. EP250526a: Global MASTER-Net observations report
  93. EP J1350.0-8622: BOOTES-6/DPRT optical upper limit
  94. EP-WXT trigger 01709176712: SVOM/C-GFT observations of blue-to-red color variation
  95. GRB 250520A: 3 GHz MeerKAT Detection
  96. GRB 250520A: 10 GHz VLA Afterglow Confirmation
  97. Fermi GRB 250523A: Global MASTER-Net observations report
  98. EP-WXT trigger 01709176712: GOTO observations confirm stellar counterpart variability
  99. GRB 250521A: GRBAlpha detection
  100. GRB 250520A: GRBAlpha detection

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