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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"

32546 results found.

  1. Swift GRB 250617B: Global MASTER-Net observations report
  2. GRB 250617B: GOTO optical upper limit
  3. GRB 250617B: Fermi GBM Observation
  4. GRB 250615A: Swift-BAT refined analysis
  5. GRB 250617B: Fermi GBM Final Localization
  6. GRB 250617B: Ondrejov D50 optical afterglow detection
  7. GRB 250617B: SAO RAS optical observations
  8. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  9. IPN triangulation of GRB 250612C (short/hard)
  10. Konus-Wind detection of GRB 250615A / EP250615a
  11. GRB 250615A / EP250615a: AstroSat CZTI detection
  12. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  13. GRB 250615A: COLIBRÍ optical upper limit
  14. GRB 250615A: DDOTI Optical Upper Limit
  15. GRB 250615A: Swift/UVOT Upper Limits
  16. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  17. sb25061207/SVOM: T120 OHP optical upper limit
  18. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  19. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  20. GRID detection of GRB 250612C
  21. sb25061207: Mephisto optical upper limits
  22. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  23. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  24. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  25. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  26. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  27. sb25061207: EP-FXT follow-up observation and afterglow candidate
  28. GRB 250612B: Fermi GBM Observation
  29. EP250612a: SVOM/VT optical candidate
  30. EP250612a: Global MASTER-Net observations report
  31. GRB 250612C: Fermi GBM Observation
  32. sb25061207: Swift-XRT observations
  33. EP250612a/GRB 250612B: JinShan optical upper limit
  34. EP 250612a: AST3-3 Yaoan Optical Observation
  35. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  36. sb25061207: SVOM/VT optical counterpart
  37. EP250610a: Upper limit from Fermi-GBM Observations
  38. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  39. GRB 250610B: Liverpool Telescope continued monitoring
  40. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  41. EP250610a: continuous follow-up observations with EP-FXT
  42. GRB 250610B - SVOM/ECLAIRs refined analysis
  43. Fermi GBM Sub-Threshold Detection of GRB 250610B
  44. GRB 250610B: Swift/UVOT Detection
  45. EP250610A: Swift/UVOT Upper limits
  46. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  47. EP250610a: TNG NIR upper limit
  48. GRB 250610B: REM optical/NIR observations
  49. EP250610a: Liverpool Telescope optical upper limits
  50. GRB 250610B: SVOM/VT optical shallow decay
  51. GRB 250610B: additional Liverpool Telescope optical observations
  52. GRB 250610B: SVOM/GRM analysis
  53. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  54. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  55. GRB 250610B: Swift-XRT counterpart detection
  56. GRB 250610B: SVOM/VT optical counterpart
  57. GRB 250610B: LT detection of the optical counterpart
  58. GRB 250610B: OHP/T120 optical counterpart candidate
  59. GRB 250610B: GOTO optical upper limit
  60. EP250610a: Global MASTER-Net observations report
  61. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  62. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  63. GRB 250605A: Swift-BAT refined analysis
  64. EP250610a: SVOM/VT optical upper limit
  65. EP250610a: REM optical/NIR observations
  66. GRB 250609A: Fermi GBM Observation
  67. EP250610a: COLIBRÍ optical upper limit
  68. GRB 250609A: Swift/BAT-GUANO localization skymap of a likely short burst
  69. GRB 250605A: Swift/UVOT Upper Limits
  70. GRB 250529A: GOTO optical counterpart candidate (GOTO25dea/AT 2025ndt)
  71. GRB 250527C: CrAO Optical Upper Limit
  72. GRB 250607A: SVOM/GRM observation of a long burst
  73. EP-WXT trigger 01709178244: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  74. EP-WXT trigger 01709178069: confirmation of a stellar flare by BOOTES-6 & BOOTES-7
  75. GRB 250605A: SVOM/VT optical upper limit
  76. Fermi GRB 250606A: Global MASTER-Net observations report
  77. GRB 250602A: GECAM detection
  78. GRB 250605A: LT optical observations
  79. Konus-Wind detection of GRB 250601A
  80. IPN triangulation of GRB 250404B
  81. IPN triangulation of GRB 250529A
  82. GRB 250601A: PRIME H band upper limit.
  83. GRB 250530A: SVOM/GRM analysis
  84. GRB 250601A: PRIME J band upper limit.
  85. GRB 250601A: VLT/FORS2 Optical Observation
  86. GRB 250601A: Fermi GBM Observation
  87. GRB 250602A: DDOTI Optical Follow-Up of the Fermi/LAT Localization
  88. GRB 250603A: Swift/UVOT Upper Limits
  89. GRB 250603A: Swift-XRT position and confirmation of GRB nature
  90. GRB 250602A: Fermi GBM Observation
  91. GRB 250602A: Fermi-LAT detection
  92. GRB 250602A: DDOTI Optical Upper Limit
  93. GRB 250530C: Swift-BAT refined analysis
  94. GRB 250521C: NOT spectroscopic observations exclude the afterglow candidate AT2025mgj
  95. GRB 250601A: EP-FXT follow-up observation and afterglow candidates
  96. GRB 250601A: Swift/XRT candidate afterglow
  97. GRB 250521C / AT2025mgj: Pan-STARRS multi-band and multi-epoch imaging and photometry
  98. Fermi GRB 250601A: Global MASTER-Net observations report
  99. GRB 250601A: Swift/BAT-GUANO arcminute localization of a likely short burst
  100. GRB 250601A: Swift ToO observations

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