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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. GRB 250617B: SVOM/VT optical observation
  2. GRB 250617B: NUTTelA-TAO early time optical observations
  3. Fermi trigger No 771886893: Global MASTER-Net observations report
  4. Swift GRB 250617B: Global MASTER-Net observations report
  5. GRB 250617B: GOTO optical upper limit
  6. GRB 250617B: Enhanced Swift-XRT position
  7. GRB 250617B: Fermi GBM Observation
  8. GRB 250615A: Swift-BAT refined analysis
  9. The EP-WXT trigger 01709178990 is likely a flaring star
  10. GRB 250617B: Fermi GBM Final Localization
  11. GRB 250617B: Ondrejov D50 optical afterglow detection
  12. GRB 250617B: SAO RAS optical observations
  13. GRB 250617B: Swift detection of a burst with an optical counterpart
  14. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  15. GRB 250617A: Fermi GBM Final Real-time Localization
  16. IPN triangulation of GRB 250612C (short/hard)
  17. EP#01709178975: Swift-XRT counterpart detection
  18. EP-WXT trigger 01709178975: GOTO optical upper limit
  19. The EP-WXT trigger 01709178975 is likely a flaring star
  20. Konus-Wind detection of GRB 250615A / EP250615a
  21. GRB 250615A / EP250615a: AstroSat CZTI detection
  22. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  23. SVOM sb25061207: AbAO AS-32 Optical Upper Limit
  24. GRB 250615A: COLIBRÍ optical upper limit
  25. GRB 250615A: DDOTI Optical Upper Limit
  26. GRB 250615A: Swift/UVOT Upper Limits
  27. Konus-Wind detection of GRB 250612C (short/hard with extended emission)
  28. GRB 250615A: Swift-XRT refined Analysis
  29. sb25061207/SVOM: T120 OHP optical upper limit
  30. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  31. Fermi trigger No 771752663: Global MASTER-Net observations report
  32. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  33. The EP-WXT trigger 01709178875 is likely a flaring star
  34. GRB 250615A: Enhanced Swift-XRT position
  35. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  36. GRB 250615A: Prompt enhanced Swift-XRT position
  37. GRB 250615A: Swift detection of a burst
  38. Swift GRB 250615A: Global MASTER-Net observations report
  39. Fermi trigger No 771718064: Global MASTER-Net observations report
  40. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  41. GRID detection of GRB 250612C
  42. sb25061207: Mephisto optical upper limits
  43. IceCube alert 141029_8144692 retraction
  44. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  45. GRB 250614A: Fermi GBM Final Real-time Localization
  46. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  47. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  48. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  49. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  50. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. Fermi trigger No 771494087: Global MASTER-Net observations report
  52. sb25061218: Swift-XRT observations
  53. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  54. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  55. sb25061207: EP-FXT follow-up observation and afterglow candidate
  56. GRB 250612B: Fermi GBM Observation
  57. EP250612a: SVOM/VT optical candidate
  58. Fermi trigger No 771424081: Global MASTER-Net observations report
  59. EP250612a: Global MASTER-Net observations report
  60. GRB 250612C: Fermi GBM Observation
  61. sb25061218: SVOM detection of a X-ray transient
  62. sb25061207: Swift-XRT observations
  63. EP250612a/GRB 250612B: JinShan optical upper limit
  64. EP 250612a: AST3-3 Yaoan Optical Observation
  65. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  66. sb25061207: SVOM/VT optical counterpart
  67. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  68. GRB 250610B: Swift-XRT refined Analysis
  69. GRB 250612C: Fermi GBM Final Real-time Localization
  70. EP250610a: Upper limit from Fermi-GBM Observations
  71. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  72. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  73. EP250612a: Einstein Probe detection of an X-ray transient
  74. GRB 250610B: Liverpool Telescope continued monitoring
  75. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  76. sb25061207: SVOM detection of a X-ray transient
  77. EP250610a: continuous follow-up observations with EP-FXT
  78. GRB 250610B - SVOM/ECLAIRs refined analysis
  79. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  80. Swift GRB250612.04: Global MASTER-Net observations report
  81. Fermi GBM Sub-Threshold Detection of GRB 250610B
  82. GRB 250610B: Swift/UVOT Detection
  83. EP250610A: Swift/UVOT Upper limits
  84. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  85. EP250610a: TNG NIR upper limit
  86. GRB 250610B: REM optical/NIR observations
  87. EP250610a: Liverpool Telescope optical upper limits
  88. GRB 250610B: SVOM/VT optical shallow decay
  89. GRB 250610B: additional Liverpool Telescope optical observations
  90. GRB 250610B: SVOM/GRM analysis
  91. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  92. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  93. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  94. GRB 250610B: Swift-XRT counterpart detection
  95. GRB 250610B: SVOM/VT optical counterpart
  96. GRB 250610B: LT detection of the optical counterpart
  97. GRB 250610B: OHP/T120 optical counterpart candidate
  98. GRB 250610C: Fermi GBM Final Real-time Localization
  99. GRB 250610B: GOTO optical upper limit
  100. EP250610a: Global MASTER-Net observations report

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