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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"
  1. Swift GRB 250617B: Global MASTER-Net observations report
  2. GRB 250617B: GOTO optical upper limit
  3. GRB 250617B: Enhanced Swift-XRT position
  4. GRB 250617B: Fermi GBM Observation
  5. GRB 250615A: Swift-BAT refined analysis
  6. The EP-WXT trigger 01709178990 is likely a flaring star
  7. GRB 250617B: Fermi GBM Final Localization
  8. GRB 250617B: Ondrejov D50 optical afterglow detection
  9. GRB 250617B: SAO RAS optical observations
  10. GRB 250617B: Swift detection of a burst with an optical counterpart
  11. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  12. GRB 250617A: Fermi GBM Final Real-time Localization
  13. IPN triangulation of GRB 250612C (short/hard)
  14. EP#01709178975: Swift-XRT counterpart detection
  15. EP-WXT trigger 01709178975: GOTO optical upper limit
  16. The EP-WXT trigger 01709178975 is likely a flaring star
  17. Konus-Wind detection of GRB 250615A / EP250615a
  18. GRB 250615A / EP250615a: AstroSat CZTI detection
  19. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  20. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  21. GRB 250615A: COLIBRÍ optical upper limit
  22. GRB 250615A: DDOTI Optical Upper Limit
  23. GRB 250615A: Swift/UVOT Upper Limits
  24. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  25. GRB 250615A: Swift-XRT refined Analysis
  26. sb25061207/SVOM: T120 OHP optical upper limit
  27. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  28. Fermi trigger No 771752663: Global MASTER-Net observations report
  29. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  30. The EP-WXT trigger 01709178875 is likely a flaring star
  31. GRB 250615A: Enhanced Swift-XRT position
  32. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  33. GRB 250615A: Prompt enhanced Swift-XRT position
  34. GRB 250615A: Swift detection of a burst
  35. Swift GRB 250615A: Global MASTER-Net observations report
  36. Fermi trigger No 771718064: Global MASTER-Net observations report
  37. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  38. GRID detection of GRB 250612C
  39. sb25061207: Mephisto optical upper limits
  40. IceCube alert 141029_8144692 retraction
  41. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  42. GRB 250614A: Fermi GBM Final Real-time Localization
  43. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  44. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  45. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  46. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  47. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  48. Fermi trigger No 771494087: Global MASTER-Net observations report
  49. sb25061218: Swift-XRT observations
  50. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  51. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  52. sb25061207: EP-FXT follow-up observation and afterglow candidate
  53. GRB 250612B: Fermi GBM Observation
  54. EP250612a: SVOM/VT optical candidate
  55. Fermi trigger No 771424081: Global MASTER-Net observations report
  56. EP250612a: Global MASTER-Net observations report
  57. GRB 250612C: Fermi GBM Observation
  58. sb25061218: SVOM detection of a X-ray transient
  59. sb25061207: Swift-XRT observations
  60. EP250612a/GRB 250612B: JinShan optical upper limit
  61. EP 250612a: AST3-3 Yaoan Optical Observation
  62. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  63. sb25061207: SVOM/VT optical counterpart
  64. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  65. GRB 250610B: Swift-XRT refined Analysis
  66. GRB 250612C: Fermi GBM Final Real-time Localization
  67. EP250610a: Upper limit from Fermi-GBM Observations
  68. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  69. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  70. EP250612a: Einstein Probe detection of an X-ray transient
  71. GRB 250610B: Liverpool Telescope continued monitoring
  72. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  73. sb25061207: SVOM detection of a X-ray transient
  74. EP250610a: continuous follow-up observations with EP-FXT
  75. GRB 250610B - SVOM/ECLAIRs refined analysis
  76. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  77. Swift GRB250612.04: Global MASTER-Net observations report
  78. Fermi GBM Sub-Threshold Detection of GRB 250610B
  79. GRB 250610B: Swift/UVOT Detection
  80. EP250610A: Swift/UVOT Upper limits
  81. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  82. EP250610a: TNG NIR upper limit
  83. GRB 250610B: REM optical/NIR observations
  84. EP250610a: Liverpool Telescope optical upper limits
  85. GRB 250610B: SVOM/VT optical shallow decay
  86. GRB 250610B: additional Liverpool Telescope optical observations
  87. GRB 250610B: SVOM/GRM analysis
  88. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  89. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  90. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  91. GRB 250610B: Swift-XRT counterpart detection
  92. GRB 250610B: SVOM/VT optical counterpart
  93. GRB 250610B: LT detection of the optical counterpart
  94. GRB 250610B: OHP/T120 optical counterpart candidate
  95. GRB 250610C: Fermi GBM Final Real-time Localization
  96. GRB 250610B: GOTO optical upper limit
  97. EP250610a: Global MASTER-Net observations report
  98. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  99. GRB 250610B: SVOM detection of a long burst
  100. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB

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