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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"

32532 results found.

  1. GRB 250615A: Swift/UVOT Upper Limits
  2. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  3. sb25061207/SVOM: T120 OHP optical upper limit
  4. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  5. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  6. GRID detection of GRB 250612C
  7. sb25061207: Mephisto optical upper limits
  8. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  9. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  10. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  11. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  12. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  13. sb25061207: EP-FXT follow-up observation and afterglow candidate
  14. GRB 250612B: Fermi GBM Observation
  15. EP250612a: SVOM/VT optical candidate
  16. EP250612a: Global MASTER-Net observations report
  17. GRB 250612C: Fermi GBM Observation
  18. sb25061207: Swift-XRT observations
  19. EP250612a/GRB 250612B: JinShan optical upper limit
  20. EP 250612a: AST3-3 Yaoan Optical Observation
  21. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  22. sb25061207: SVOM/VT optical counterpart
  23. EP250610a: Upper limit from Fermi-GBM Observations
  24. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  25. GRB 250610B: Liverpool Telescope continued monitoring
  26. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  27. EP250610a: continuous follow-up observations with EP-FXT
  28. GRB 250610B - SVOM/ECLAIRs refined analysis
  29. Fermi GBM Sub-Threshold Detection of GRB 250610B
  30. GRB 250610B: Swift/UVOT Detection
  31. EP250610A: Swift/UVOT Upper limits
  32. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  33. EP250610a: TNG NIR upper limit
  34. GRB 250610B: REM optical/NIR observations
  35. EP250610a: Liverpool Telescope optical upper limits
  36. GRB 250610B: SVOM/VT optical shallow decay
  37. GRB 250610B: additional Liverpool Telescope optical observations
  38. GRB 250610B: SVOM/GRM analysis
  39. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  40. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  41. GRB 250610B: Swift-XRT counterpart detection
  42. GRB 250610B: SVOM/VT optical counterpart
  43. GRB 250610B: LT detection of the optical counterpart
  44. GRB 250610B: OHP/T120 optical counterpart candidate
  45. GRB 250610B: GOTO optical upper limit
  46. EP250610a: Global MASTER-Net observations report
  47. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  48. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  49. GRB 250605A: Swift-BAT refined analysis
  50. EP250610a: SVOM/VT optical upper limit
  51. EP250610a: REM optical/NIR observations
  52. GRB 250609A: Fermi GBM Observation
  53. EP250610a: COLIBRÍ optical upper limit
  54. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  55. GRB 250605A: Swift/UVOT Upper Limits
  56. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  57. GRB 250527C: CrAO Optical Upper Limit
  58. GRB 250607A: SVOM/GRM observation of a long burst
  59. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  60. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  61. GRB 250605A: SVOM/VT optical upper limit
  62. Fermi GRB 250606A: Global MASTER-Net observations report
  63. GRB 250602A: GECAM detection
  64. GRB 250605A: LT optical observations
  65. Konus-Wind detection of GRB 250601A
  66. IPN triangulation of GRB 250404B
  67. IPN triangulation of GRB 250529A
  68. GRB 250601A: PRIME H band upper limit.
  69. GRB 250530A: SVOM/GRM analysis
  70. GRB 250601A: PRIME J band upper limit.
  71. GRB 250601A: VLT/FORS2 Optical Observation
  72. GRB 250601A: Fermi GBM Observation
  73. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  74. GRB 250603A: Swift/UVOT Upper Limits
  75. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  76. GRB 250602A: Fermi GBM Observation
  77. GRB 250602A: Fermi-LAT detection
  78. GRB 250602A: DDOTI Optical Upper Limit
  79. GRB 250530C: Swift-BAT refined analysis
  80. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  81. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  82. GRB 250601A: Swift/XRT candidate afterglow
  83. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  84. Fermi GRB 250601A: Global MASTER-Net observations report
  85. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  86. GRB 250601A: Swift ToO observations
  87. GRB 250530A: VLT/HAWK-I NIR counterpart fading
  88. GRB 250521C/AT2025mgj: FTW optical and NIR observations
  89. EP#01709177494: SVOM/VT optical observations
  90. Fermi GRB 250531A: Global MASTER-Net observations report
  91. GRB 250530C: BOOTES-7 optical upper limit
  92. GRB 250521C/ZTF25aarhkyn/AT2025mgj: COLIBRÍ optical observations
  93. GRB 250530A: TNG detection of a NIR source inside the Swift/XRT error circle
  94. Swift GRB 250530C: Global MASTER-Net observations report
  95. GRB 250521C/AT2025mgj: NOT optical observations of the afterglow candidate
  96. GRB 250530A: EP-FXT counterpart detection
  97. GRB 250530A: SVOM/VT optical upper limit
  98. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate retraction and detection limit
  99. GRB 250530A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  100. GRB 250527D: CALET Gamma-Ray Burst Monitor detection

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