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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 251205A: ZTF and ATLAS optical afterglow detections
  2. GRB 251205A: GROWTH-India Telescope optical observations
  3. GRB 251205A: Swift-BAT refined analysis
  4. GRB 251205A: Swift-XRT refined Analysis
  5. GRB 251205A: Swift/UVOT Detection
  6. GRB 251205A: Liverpool Telescope optical follow-up observations
  7. GRB 251203C: Swift/UVOT Upper Limit
  8. Konus-Wind detection of GRB 251118A
  9. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  10. GRB 251205A: COLIBRÍ optical observations
  11. GRB 251205A: GOTO optical afterglow detection
  12. GRB 251205A: NOT optical observations
  13. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  14. GRB 251205A: Enhanced Swift-XRT position
  15. Swift GRB 251205A : MASTER OT detection with host galaxy
  16. GRB 251205A: Swift detection of a burst with an optical afterglow
  17. Swift GRB251205A: Global MASTER-Net observations report
  18. GRB 251126B: Fermi GBM Final Localization
  19. GRB 251203A: Insight-HXMT/HE detection
  20. GRB 251203C: SVOM/ECLAIRs refined analysis
  21. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  22. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  23. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  24. GRB 251202A: SVOM/GRM observation
  25. GRB 251203A: GECAM-B observation of a burst
  26. GRB 251203A: SVOM/GRM observation
  27. GRB 251201B: SALT spectroscopic redshift z = 1.599
  28. GRB 251203C: J-band observations with WINTER
  29. GRB 251129B: Glowbug gamma-ray detection of a short burst
  30. GRB 251203A: AstroSat CZTI detection
  31. EP251130a: JinShan near-infrared observations
  32. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  33. GRB 251203C: LCO optical afterglow confirmation
  34. GRB 251203C: SVOM/VT optical counterpart
  35. GRB 251203C: EP-FXT follow-up observation
  36. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  37. GRB 251129B: GECAM-B observation of a burst
  38. GRB 251203B: Swift-XRT observations
  39. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  40. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  41. GRB 251203C: LCO optical upper limits
  42. GRB 251203B: LCO optical upper limits
  43. GRB 251203B: SVOM/VT optical observation
  44. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  45. GRB 251203C: SVOM detection of a burst
  46. SVOM GRB251203.77: Global MASTER-Net observations report
  47. SVOM GRB251203B: Global MASTER-Net observations report
  48. GRB 251203B: SVOM detection of a burst
  49. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  50. GRB 251201B: Insight-HXMT/HE detection
  51. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  52. EP251130a: MAO/AZT-22 optical observations
  53. GRB 251203A: Fermi GBM Final Real-time Localization
  54. EP251202a / GRB251202A: AstroSat CZTI detection
  55. GRB 251202A / EP251202a: SVOM/VT optical observation
  56. GRB 251201B: Fermi GBM Observation
  57. EP251202a/GRB 251202A: KAIT optical observations
  58. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  59. Fermi GRB 251202B: Global MASTER-Net observations report
  60. GRB 251202B: Fermi GBM Final Real-time Localization
  61. IPN triangulation of GRB 251129B (short/hard)
  62. GRB251129A/EP251129a: Swift UVOT detection
  63. GRB 251129B: AstroSat CZTI detection
  64. GRB 251202A: Fermi GBM Observation
  65. GRB 251202A: Swift/UVOT Detection
  66. GRB 251201B: Kilonova-Catcher optical afterglow detection
  67. GRB 251201B: Swift/UVOT Detection
  68. GRB 251130B: Glowbug gamma-ray detection
  69. GRB 251201B: GECAM-B observation of a long burst
  70. EP251130a: continued NOT optical observations indicate steep fading phase
  71. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  72. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  73. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  74. GRB 251202A: GOTO optical afterglow detection
  75. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  76. GRB 251201A: GECAM-B observation of a burst
  77. GRB 251126A: SAO RAS optical marginal detection
  78. GRB 251202A: Swift-XRT afterglow detection
  79. EP251129a/GRB 251129A: NOWT Detection
  80. GRB 251126A: SVOM/VT optical observation
  81. EP251130a: SVOM/VT optical observation
  82. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  83. Fermi GRB 251202A: Global MASTER-Net observations report
  84. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  85. GRB 251201B: Swift-XRT refined Analysis
  86. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  87. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  88. GRB 251202A: Fermi GBM Final Real-time Localization
  89. GRB 251201A: SVOM/GRM observation of a burst
  90. GRB 251201B: SVOM/VT optical fading
  91. Swift GRB 251201B : MASTER optical counterpart detection
  92. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  93. Swift GRB 251201B: Global MASTER-Net observations report
  94. GRB 251201B: Enhanced Swift-XRT position
  95. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  96. GRB 251130B: AstroSat CZTI detection
  97. GRB 251201B: Swift detection of a burst with an optical counterpart
  98. GRB 251201B: Fermi GBM Final Real-time Localization
  99. EP251130a: Mondy optical observations
  100. EP251130a: Optical detections with Kinder observations

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