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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"

27018 results found.

  1. GRB 251205A: NOT optical observations
  2. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  3. GRB 251205A: Swift detection of a burst with an optical afterglow
  4. Swift GRB251205A: Global MASTER-Net observations report
  5. GRB 251126B: Fermi GBM Final Localization
  6. GRB 251203C: SVOM/ECLAIRs refined analysis
  7. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  8. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  9. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  10. GRB 251202A: SVOM/GRM observation
  11. GRB 251203A: GECAM-B observation of a burst
  12. GRB 251203A: SVOM/GRM observation
  13. GRB 251201B: SALT spectroscopic redshift z = 1.599
  14. GRB 251203C: J-band observations with WINTER
  15. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  16. GRB 251203C: LCO optical afterglow confirmation
  17. GRB 251203C: SVOM/VT optical counterpart
  18. GRB 251203C: EP-FXT follow-up observation
  19. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  20. GRB 251129B: GECAM-B observation of a burst
  21. GRB 251203B: Swift-XRT observations
  22. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  23. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  24. GRB 251203C: LCO optical upper limits
  25. GRB 251203B: LCO optical upper limits
  26. GRB 251203B: SVOM/VT optical observation
  27. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  28. GRB 251203C: SVOM detection of a burst
  29. SVOM GRB251203.77: Global MASTER-Net observations report
  30. SVOM GRB251203B: Global MASTER-Net observations report
  31. GRB 251203B: SVOM detection of a burst
  32. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  33. GRB 251203A: Fermi GBM Final Real-time Localization
  34. GRB 251202A / EP251202a: SVOM/VT optical observation
  35. GRB 251201B: Fermi GBM Observation
  36. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  37. Fermi GRB 251202B: Global MASTER-Net observations report
  38. GRB 251202B: Fermi GBM Final Real-time Localization
  39. GRB251129A/EP251129a: Swift UVOT detection
  40. GRB 251202A: Fermi GBM Observation
  41. GRB 251202A: Swift/UVOT Detection
  42. GRB 251201B: Kilonova-Catcher optical afterglow detection
  43. GRB 251201B: Swift/UVOT Detection
  44. GRB 251130B: Glowbug gamma-ray detection
  45. GRB 251201B: GECAM-B observation of a long burst
  46. EP251130a: continued NOT optical observations indicate steep fading phase
  47. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  48. GRB 251202A: GOTO optical afterglow detection
  49. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  50. GRB 251201A: GECAM-B observation of a burst
  51. GRB 251126A: SVOM/VT optical observation
  52. EP251130a: SVOM/VT optical observation
  53. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  54. Fermi GRB 251202A: Global MASTER-Net observations report
  55. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  56. GRB 251201B: Swift-XRT refined Analysis
  57. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  58. GRB 251202A: Fermi GBM Final Real-time Localization
  59. GRB 251201A: SVOM/GRM observation of a burst
  60. GRB 251201B: SVOM/VT optical fading
  61. Swift GRB 251201B : MASTER optical counterpart detection
  62. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  63. Swift GRB 251201B: Global MASTER-Net observations report
  64. GRB 251201B: Swift detection of a burst with an optical counterpart
  65. GRB 251201B: Fermi GBM Final Real-time Localization
  66. EP251130a: Optical detections with Kinder observations
  67. SVOM GRB251201.19: Global MASTER-Net observations report
  68. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  69. EP251130A: Optical observation from 1.3m DFOT
  70. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  71. Fermi GRB 251130B: Global MASTER-Net observations report
  72. GRB 251127A: SVOM/GRM observation
  73. IceCube Alert 251130.75: Global MASTER-Net observations report
  74. EP251130a: Swift-XRT counterpart detection
  75. GRB 251130B: Fermi GBM Final Localization Correction
  76. EP251130a: Global MASTER-Net observations report
  77. GRB 251130B: Fermi GBM Final Real-time Localization
  78. EP251130a: COLIBRÍ optical counterpart candidate
  79. EP251130a: Einstein Probe detection of an X-ray transient
  80. EP251129a/GRB 251129A: EP-FXT follow-up observations
  81. GRB 251130A: Fermi GBM Final Real-time Localization
  82. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  83. GRB 251128A: GECAM-B detection
  84. GRB 251128A: SVOM/GRM observation of a long burst
  85. SVOM GRB 251129A : MASTER optical counterpart detection
  86. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  87. Swift trigger 1418333 is not an astrophysical source
  88. GRB 251129A / EP251129a: SVOM/VT optical fading
  89. EP251129a: Global MASTER-Net observations report
  90. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  91. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  92. GRB 251128A: Fermi GBM Observation
  93. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  94. GRB 251129A: SVOM detection of a burst
  95. SVOM GRB251129A: Global MASTER-Net observations report
  96. GRB 251129A: SVOM detection of a burst
  97. GRB 251126A: Swift-BAT refined analysis
  98. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  99. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  100. Fermi GRB 251128A: Global MASTER-Net observations report

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