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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. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  2. The EP-WXT trigger 01709249380 is likely a flaring star
  3. GRB 251205A: ZTF and ATLAS optical afterglow detections
  4. GRB 251205A: GROWTH-India Telescope optical observations
  5. GRB 251205A: Swift-BAT refined analysis
  6. GRB 251205A: Swift-XRT refined Analysis
  7. GRB 251205A: Swift/UVOT Detection
  8. GRB 251205A: Liverpool Telescope optical follow-up observations
  9. GRB 251203C: Swift/UVOT Upper Limit
  10. Konus-Wind detection of GRB 251118A
  11. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  12. GRB 251205A: COLIBRÍ optical observations
  13. GRB 251205A: GOTO optical afterglow detection
  14. GRB 251205A: NOT optical observations
  15. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  16. GRB 251205A: Enhanced Swift-XRT position
  17. Swift GRB 251205A : MASTER OT detection with host galaxy
  18. GRB 251205A: Swift detection of a burst with an optical afterglow
  19. Swift GRB251205A: Global MASTER-Net observations report
  20. GRB 251126B: Fermi GBM Final Localization
  21. GRB 251203A: Insight-HXMT/HE detection
  22. GRB 251203C: SVOM/ECLAIRs refined analysis
  23. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  24. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  25. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  26. GRB 251202A: SVOM/GRM observation
  27. GRB 251203A: GECAM-B observation of a burst
  28. GRB 251203A: SVOM/GRM observation
  29. GRB 251201B: SALT spectroscopic redshift z = 1.599
  30. GRB 251203C: J-band observations with WINTER
  31. GRB 251129B: Glowbug gamma-ray detection of a short burst
  32. GRB 251203A: AstroSat CZTI detection
  33. EP251130a: JinShan near-infrared observations
  34. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  35. GRB 251203C: LCO optical afterglow confirmation
  36. GRB 251203C: SVOM/VT optical counterpart
  37. GRB 251203C: EP-FXT follow-up observation
  38. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  39. GRB 251129B: GECAM-B observation of a burst
  40. GRB 251203B: Swift-XRT observations
  41. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  42. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  43. GRB 251203C: LCO optical upper limits
  44. GRB 251203B: LCO optical upper limits
  45. GRB 251203B: SVOM/VT optical observation
  46. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  47. GRB 251203C: SVOM detection of a burst
  48. SVOM GRB251203.77: Global MASTER-Net observations report
  49. SVOM GRB251203B: Global MASTER-Net observations report
  50. GRB 251203B: SVOM detection of a burst
  51. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  52. GRB 251201B: Insight-HXMT/HE detection
  53. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  54. EP251130a: MAO/AZT-22 optical observations
  55. GRB 251203A: Fermi GBM Final Real-time Localization
  56. EP251202a / GRB251202A: AstroSat CZTI detection
  57. GRB 251202A / EP251202a: SVOM/VT optical observation
  58. GRB 251201B: Fermi GBM Observation
  59. EP251202a/GRB 251202A: KAIT optical observations
  60. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  61. Fermi GRB 251202B: Global MASTER-Net observations report
  62. GRB 251202B: Fermi GBM Final Real-time Localization
  63. IPN triangulation of GRB 251129B (short/hard)
  64. GRB251129A/EP251129a: Swift UVOT detection
  65. GRB 251129B: AstroSat CZTI detection
  66. GRB 251202A: Fermi GBM Observation
  67. GRB 251202A: Swift/UVOT Detection
  68. GRB 251201B: Kilonova-Catcher optical afterglow detection
  69. GRB 251201B: Swift/UVOT Detection
  70. GRB 251130B: Glowbug gamma-ray detection
  71. GRB 251201B: GECAM-B observation of a long burst
  72. EP251130a: continued NOT optical observations indicate steep fading phase
  73. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  74. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  75. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  76. GRB 251202A: GOTO optical afterglow detection
  77. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  78. GRB 251201A: GECAM-B observation of a burst
  79. GRB 251126A: SAO RAS optical marginal detection
  80. GRB 251202A: Swift-XRT afterglow detection
  81. EP251129a/GRB 251129A: NOWT Detection
  82. GRB 251126A: SVOM/VT optical observation
  83. EP251130a: SVOM/VT optical observation
  84. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  85. Fermi GRB 251202A: Global MASTER-Net observations report
  86. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  87. GRB 251201B: Swift-XRT refined Analysis
  88. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  89. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  90. GRB 251202A: Fermi GBM Final Real-time Localization
  91. GRB 251201A: SVOM/GRM observation of a burst
  92. GRB 251201B: SVOM/VT optical fading
  93. Swift GRB 251201B : MASTER optical counterpart detection
  94. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  95. Swift GRB 251201B: Global MASTER-Net observations report
  96. GRB 251201B: Enhanced Swift-XRT position
  97. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  98. GRB 251130B: AstroSat CZTI detection
  99. GRB 251201B: Swift detection of a burst with an optical counterpart
  100. GRB 251201B: Fermi GBM Final Real-time Localization

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