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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"

25586 results found.

  1. GRB 251205A: Liverpool Telescope further optical follow-up observations
  2. SVOM GRB251206.86: Global MASTER-Net observations report
  3. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  4. The EP-WXT trigger 01709249380 is likely a flaring star
  5. GRB 251205A: GROWTH-India Telescope optical observations
  6. GRB 251205A: Swift-BAT refined analysis
  7. GRB 251205A: Swift-XRT refined Analysis
  8. GRB 251205A: Swift/UVOT Detection
  9. GRB 251205A: Liverpool Telescope optical follow-up observations
  10. GRB 251203C: Swift/UVOT Upper Limit
  11. GRB 251205A: COLIBRÍ optical observations
  12. GRB 251205A: GOTO optical afterglow detection
  13. GRB 251205A: NOT optical observations
  14. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  15. GRB 251205A: Swift detection of a burst with an optical afterglow
  16. Swift GRB251205A: Global MASTER-Net observations report
  17. GRB 251126B: Fermi GBM Final Localization
  18. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  19. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  20. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  21. GRB 251201B: SALT spectroscopic redshift z = 1.599
  22. GRB 251203C: J-band observations with WINTER
  23. GRB 251129B: Glowbug gamma-ray detection of a short burst
  24. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  25. GRB 251203C: LCO optical afterglow confirmation
  26. GRB 251203C: SVOM/VT optical counterpart
  27. GRB 251203C: EP-FXT follow-up observation
  28. GRB 251203B: Swift-XRT observations
  29. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  30. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  31. GRB 251203C: LCO optical upper limits
  32. GRB 251203B: LCO optical upper limits
  33. GRB 251203B: SVOM/VT optical observation
  34. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  35. GRB 251203C: SVOM detection of a burst
  36. SVOM GRB251203.77: Global MASTER-Net observations report
  37. SVOM GRB251203B: Global MASTER-Net observations report
  38. GRB 251203B: SVOM detection of a burst
  39. GRB 251203A: Fermi GBM Final Real-time Localization
  40. GRB 251202A / EP251202a: SVOM/VT optical observation
  41. GRB 251201B: Fermi GBM Observation
  42. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  43. Fermi GRB 251202B: Global MASTER-Net observations report
  44. GRB 251202B: Fermi GBM Final Real-time Localization
  45. IPN triangulation of GRB 251129B (short/hard)
  46. GRB251129A/EP251129a: Swift UVOT detection
  47. GRB 251202A: Fermi GBM Observation
  48. GRB 251202A: Swift/UVOT Detection
  49. GRB 251201B: Kilonova-Catcher optical afterglow detection
  50. GRB 251201B: Swift/UVOT Detection
  51. GRB 251130B: Glowbug gamma-ray detection
  52. EP251130a: continued NOT optical observations indicate steep fading phase
  53. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  54. GRB 251202A: GOTO optical afterglow detection
  55. GRB 251126A: SVOM/VT optical observation
  56. EP251130a: SVOM/VT optical observation
  57. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  58. Fermi GRB 251202A: Global MASTER-Net observations report
  59. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  60. GRB 251201B: Swift-XRT refined Analysis
  61. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  62. GRB 251202A: Fermi GBM Final Real-time Localization
  63. GRB 251201A: SVOM/GRM observation of a burst
  64. GRB 251201B: SVOM/VT optical fading
  65. Swift GRB 251201B : MASTER optical counterpart detection
  66. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  67. Swift GRB 251201B: Global MASTER-Net observations report
  68. GRB 251201B: Swift detection of a burst with an optical counterpart
  69. GRB 251201B: Fermi GBM Final Real-time Localization
  70. EP251130a: Optical detections with Kinder observations
  71. SVOM GRB251201.19: Global MASTER-Net observations report
  72. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  73. EP251130A: Optical observation from 1.3m DFOT
  74. Fermi GRB 251130B: Global MASTER-Net observations report
  75. IceCube Alert 251130.75: Global MASTER-Net observations report
  76. EP251130a: Swift-XRT counterpart detection
  77. GRB 251130B: Fermi GBM Final Localization Correction
  78. EP251130a: Global MASTER-Net observations report
  79. GRB 251130B: Fermi GBM Final Real-time Localization
  80. EP251130a: COLIBRÍ optical counterpart candidate
  81. GRB 251130A: Fermi GBM Final Real-time Localization
  82. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  83. GRB 251128A: AstroSat CZTI detection
  84. SVOM GRB 251129A : MASTER optical counterpart detection
  85. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  86. Swift trigger 1418333 is not an astrophysical source
  87. GRB 251129A / EP251129a: SVOM/VT optical fading
  88. EP251129a: Global MASTER-Net observations report
  89. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  90. GRB 251128A: Fermi GBM Observation
  91. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  92. GRB 251129A: SVOM detection of a burst
  93. SVOM GRB251129A: Global MASTER-Net observations report
  94. GRB 251129A: SVOM detection of a burst
  95. GRB 251126A: Swift-BAT refined analysis
  96. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  97. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  98. Fermi GRB 251128A: Global MASTER-Net observations report
  99. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  100. GRB 251126A NUTTelA-TAO Early Measurements

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