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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"

28720 results found.

  1. sb25061207: EP-FXT follow-up observation and afterglow candidate
  2. GRB 250612B: Fermi GBM Observation
  3. EP250612a: SVOM/VT optical candidate
  4. EP250612a: Global MASTER-Net observations report
  5. GRB 250612C: Fermi GBM Observation
  6. sb25061207: Swift-XRT observations
  7. EP250612a/GRB 250612B: JinShan optical upper limit
  8. EP 250612a: AST3-3 Yaoan Optical Observation
  9. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  10. sb25061207: SVOM/VT optical counterpart
  11. EP250610a: Upper limit from Fermi-GBM Observations
  12. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  13. GRB 250610B: Liverpool Telescope continued monitoring
  14. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  15. EP250610a: continuous follow-up observations with EP-FXT
  16. GRB 250610B - SVOM/ECLAIRs refined analysis
  17. Fermi GBM Sub-Threshold Detection of GRB 250610B
  18. GRB 250610B: Swift/UVOT Detection
  19. EP250610A: Swift/UVOT Upper limits
  20. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  21. EP250610a: TNG NIR upper limit
  22. GRB 250610B: REM optical/NIR observations
  23. EP250610a: Liverpool Telescope optical upper limits
  24. GRB 250610B: SVOM/VT optical shallow decay
  25. GRB 250610B: additional Liverpool Telescope optical observations
  26. GRB 250610B: SVOM/GRM analysis
  27. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  28. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  29. GRB 250610B: Swift-XRT counterpart detection
  30. GRB 250610B: SVOM/VT optical counterpart
  31. GRB 250610B: LT detection of the optical counterpart
  32. GRB 250610B: OHP/T120 optical counterpart candidate
  33. GRB 250610B: GOTO optical upper limit
  34. EP250610a: Global MASTER-Net observations report
  35. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  36. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  37. GRB 250605A: Swift-BAT refined analysis
  38. EP250610a: SVOM/VT optical upper limit
  39. EP250610a: REM optical/NIR observations
  40. GRB 250609A: Fermi GBM Observation
  41. EP250610a: COLIBRÍ optical upper limit
  42. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  43. GRB 250605A: Swift/UVOT Upper Limits
  44. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  45. GRB 250527C: CrAO Optical Upper Limit
  46. GRB 250607A: SVOM/GRM observation of a long burst
  47. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  48. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  49. GRB 250605A: SVOM/VT optical upper limit
  50. Fermi GRB 250606A: Global MASTER-Net observations report
  51. GRB 250602A: GECAM detection
  52. GRB 250605A: LT optical observations
  53. Konus-Wind detection of GRB 250601A
  54. IPN triangulation of GRB 250404B
  55. IPN triangulation of GRB 250529A
  56. GRB 250601A: PRIME H band upper limit.
  57. GRB 250530A: SVOM/GRM analysis
  58. GRB 250601A: PRIME J band upper limit.
  59. GRB 250601A: VLT/FORS2 Optical Observation
  60. GRB 250601A: Fermi GBM Observation
  61. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  62. GRB 250603A: Swift/UVOT Upper Limits
  63. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  64. GRB 250602A: Fermi GBM Observation
  65. GRB 250602A: Fermi-LAT detection
  66. GRB 250602A: DDOTI Optical Upper Limit
  67. GRB 250530C: Swift-BAT refined analysis
  68. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  69. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  70. GRB 250601A: Swift/XRT candidate afterglow
  71. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  72. Fermi GRB 250601A: Global MASTER-Net observations report
  73. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  74. GRB 250601A: Swift ToO observations
  75. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  76. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  77. EP#01709177494: SVOM/VT optical observations
  78. Fermi GRB 250531A: Global MASTER-Net observations report
  79. GRB 250530C: BOOTES-7 optical upper limit
  80. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  81. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  82. Swift GRB 250530C: Global MASTER-Net observations report
  83. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  84. GRB 250530A: EP-FXT counterpart detection
  85. GRB 250530A: SVOM/VT optical upper limit
  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 250527D: CALET Gamma-Ray Burst Monitor detection
  89. GRB 250527C: Swift/UVOT Upper Limits
  90. EP J1350.0-8622: EP-FXT follow-up observation
  91. EP-WXT trigger 01709177124: confirmation of a stellar flare by BOOTES-6
  92. GRB 250521C (short): Zwicky Transient Facility identification of a possible fast optical transient counterpart
  93. GRB 250520A: Swift-BAT refined analysis
  94. GRB 250527C: Swift ToO observations
  95. GRB 250527C: Swift/BAT-GUANO arcminute localization of a burst
  96. EP250526a: SVOM/VT optical upper limit
  97. GRB 250521D: SVOM/GRM analysis suggests a possible “long” duration type I burst
  98. GRB 250527B: Tiled Swift observations
  99. GRB 250520A: Gemini-South optical afterglow detection
  100. EP250526a: refined analysis of the EP-WXT and EP-FXT observations

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