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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"

44330 results found.

  1. GRB 250617B: SAO RAS optical observations
  2. GRB 250617B: Swift detection of a burst with an optical counterpart
  3. GRB 250615A: Calapai Observatory, Massa S. Giorgio (Messina), upper limit
  4. GRB 250617A: Fermi GBM Final Real-time Localization
  5. IPN triangulation of GRB 250612C (short/hard)
  6. EP#01709178975: Swift-XRT counterpart detection
  7. EP-WXT trigger 01709178975: GOTO optical upper limit
  8. The EP-WXT trigger 01709178975 is likely a flaring star
  9. Konus-Wind detection of GRB 250615A / EP250615a
  10. GRB 250615A / EP250615a: AstroSat CZTI detection
  11. Fermi Gamma-ray Burst Monitor trigger 771803204/250616907 is not a GRB
  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. GRB 250615A: Swift-XRT refined Analysis
  18. sb25061207/SVOM: T120 OHP optical upper limit
  19. EP250615a/GRB 250615A: EP-WXT detection of a fast X-ray transient
  20. Fermi trigger No 771752663: Global MASTER-Net observations report
  21. EP-WXT trigger 01709178875: confirmation of a stellar flare by BOOTES-6
  22. The EP-WXT trigger 01709178875 is likely a flaring star
  23. GRB 250615A: Enhanced Swift-XRT position
  24. Fermi Gamma-ray Burst Monitor trigger 771718064/250615922 is not a GRB
  25. GRB 250615A: Prompt enhanced Swift-XRT position
  26. GRB 250615A: Swift detection of a burst
  27. Swift GRB 250615A: Global MASTER-Net observations report
  28. Fermi trigger No 771718064: Global MASTER-Net observations report
  29. Fermi Gamma-ray Burst Monitor trigger 771704505/250615765 is not a GRB
  30. GRID detection of GRB 250612C
  31. sb25061207: Mephisto optical upper limits
  32. IceCube alert 141029_8144692 retraction
  33. Fermi Gamma-ray Burst Monitor trigger 771596290/250614513 is not a GRB
  34. GRB 250614A: Fermi GBM Final Real-time Localization
  35. EP250612a / GRB 250612B: NOT optical observations of the afterglow candidate
  36. Fermi Gamma-ray Burst Monitor trigger 771547945/250613953 is not a GRB
  37. Fermi Gamma-ray Burst Monitor trigger 771541927/250613883 is not a GRB
  38. sb25061218: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  39. sb25061207: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  40. Fermi trigger No 771494087: Global MASTER-Net observations report
  41. sb25061218: Swift-XRT observations
  42. EP250612a: refined analysis of the EP-WXT and EP-FXT observations
  43. GRB 250610B: J band upper limit by SYSU 80cm infrared telescope
  44. sb25061207: EP-FXT follow-up observation and afterglow candidate
  45. GRB 250612B: Fermi GBM Observation
  46. EP250612a: SVOM/VT optical candidate
  47. Fermi trigger No 771424081: Global MASTER-Net observations report
  48. EP250612a: Global MASTER-Net observations report
  49. GRB 250612C: Fermi GBM Observation
  50. sb25061218: SVOM detection of a X-ray transient
  51. sb25061207: Swift-XRT observations
  52. EP250612a/GRB 250612B: JinShan optical upper limit
  53. EP 250612a: AST3-3 Yaoan Optical Observation
  54. GRB 250612C: SVOM/GRM observation an intermedium duration burst
  55. sb25061207: SVOM/VT optical counterpart
  56. GRB 250612C: BALROG localization (Fermi Trigger 771432801 / GRB 250612620)
  57. GRB 250610B: Swift-XRT refined Analysis
  58. GRB 250612C: Fermi GBM Final Real-time Localization
  59. EP250610a: Upper limit from Fermi-GBM Observations
  60. GRB 250612B (250612519/771424081): Fermi GBM Final Localization
  61. GRB 250612B: BALROG localization (Fermi Trigger 771424081 / GRB 250612519)
  62. EP250612a: Einstein Probe detection of an X-ray transient
  63. GRB 250610B: Liverpool Telescope continued monitoring
  64. GRB 250610B: MISTRAL/T193 and T120 OHP further observations
  65. sb25061207: SVOM detection of a X-ray transient
  66. EP250610a: continuous follow-up observations with EP-FXT
  67. GRB 250610B - SVOM/ECLAIRs refined analysis
  68. GRB 250612A: Swift detection of a burst or new Galactic transient Swift J1643.6-3854
  69. Swift GRB250612.04: Global MASTER-Net observations report
  70. Fermi GBM Sub-Threshold Detection of GRB 250610B
  71. GRB 250610B: Swift/UVOT Detection
  72. EP250610A: Swift/UVOT Upper limits
  73. GRB 250610B: SVOM/COLIBRÍ (FM-GFT) optical observations
  74. EP250610a: TNG NIR upper limit
  75. GRB 250610B: REM optical/NIR observations
  76. EP250610a: Liverpool Telescope optical upper limits
  77. GRB 250610B: SVOM/VT optical shallow decay
  78. GRB 250610B: additional Liverpool Telescope optical observations
  79. GRB 250610B: SVOM/GRM analysis
  80. GRB 250610B: Fermi/GBM sub-threshold detection of a possibly hard burst
  81. GRB 250610B: EP-FXT follow-up observation and afterglow counterpart
  82. Fermi Gamma-ray Burst Monitor trigger 771286888/250610932 is not a GRB
  83. GRB 250610B: Swift-XRT counterpart detection
  84. GRB 250610B: SVOM/VT optical counterpart
  85. GRB 250610B: LT detection of the optical counterpart
  86. GRB 250610B: OHP/T120 optical counterpart candidate
  87. GRB 250610C: Fermi GBM Final Real-time Localization
  88. GRB 250610B: GOTO optical upper limit
  89. EP250610a: Global MASTER-Net observations report
  90. GRB 250610B : SVOM/GWAC-F60A and F50 observations
  91. GRB 250610B: SVOM detection of a long burst
  92. Fermi Gamma-ray Burst Monitor trigger 771256110/250610575 is not a GRB
  93. EP250610a: refined analysis of the EP-WXT and EP-FXT observations
  94. GRB 250610A: Fermi GBM Final Real-time Localization
  95. GRB 250605A: Swift-BAT refined analysis
  96. EP250610a: SVOM/VT optical upper limit
  97. EP250610a: REM optical/NIR observations
  98. GRB 250609A: Fermi GBM Observation
  99. GRBAlpha reentry on June 9, 2025
  100. EP250610a: Swift-XRT counterpart detection

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