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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 : MITSuME Akeno optical afterglow candidate detection
  2. GRB 251208B: Fermi GBM Final Real-time Localization
  3. GRB 251208A: Fermi GBM Final Real-time Localization
  4. GRB 251205A: FTW optical and NIR observations
  5. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  6. GRB 251205A: Liverpool Telescope further optical follow-up observations
  7. SVOM GRB251206.86: Global MASTER-Net observations report
  8. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  9. The EP-WXT trigger 01709249380 is likely a flaring star
  10. GRB 251205A: ZTF and ATLAS optical afterglow detections
  11. GRB 251205A: GROWTH-India Telescope optical observations
  12. GRB 251205A: Swift-BAT refined analysis
  13. GRB 251205A: Swift-XRT refined Analysis
  14. GRB 251205A: Swift/UVOT Detection
  15. GRB 251205A: Liverpool Telescope optical follow-up observations
  16. GRB 251203C: Swift/UVOT Upper Limit
  17. Konus-Wind detection of GRB 251118A
  18. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  19. GRB 251205A: COLIBRÍ optical observations
  20. GRB 251205A: GOTO optical afterglow detection
  21. GRB 251205A: NOT optical observations
  22. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  23. GRB 251205A: Enhanced Swift-XRT position
  24. Swift GRB 251205A : MASTER OT detection with host galaxy
  25. GRB 251205A: Swift detection of a burst with an optical afterglow
  26. Swift GRB251205A: Global MASTER-Net observations report
  27. GRB 251126B: Fermi GBM Final Localization
  28. GRB 251203A: Insight-HXMT/HE detection
  29. GRB 251203C: SVOM/ECLAIRs refined analysis
  30. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  31. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  32. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  33. GRB 251202A: SVOM/GRM observation
  34. GRB 251203A: GECAM-B observation of a burst
  35. GRB 251203A: SVOM/GRM observation
  36. GRB 251201B: SALT spectroscopic redshift z = 1.599
  37. GRB 251203C: J-band observations with WINTER
  38. GRB 251129B: Glowbug gamma-ray detection of a short burst
  39. GRB 251203A: AstroSat CZTI detection
  40. EP251130a: JinShan near-infrared observations
  41. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  42. GRB 251203C: LCO optical afterglow confirmation
  43. GRB 251203C: SVOM/VT optical counterpart
  44. GRB 251203C: EP-FXT follow-up observation
  45. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  46. GRB 251129B: GECAM-B observation of a burst
  47. GRB 251203B: Swift-XRT observations
  48. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  49. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  50. GRB 251203C: LCO optical upper limits
  51. GRB 251203B: LCO optical upper limits
  52. GRB 251203B: SVOM/VT optical observation
  53. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  54. GRB 251203C: SVOM detection of a burst
  55. SVOM GRB251203.77: Global MASTER-Net observations report
  56. SVOM GRB251203B: Global MASTER-Net observations report
  57. GRB 251203B: SVOM detection of a burst
  58. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  59. GRB 251201B: Insight-HXMT/HE detection
  60. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  61. EP251130a: MAO/AZT-22 optical observations
  62. GRB 251203A: Fermi GBM Final Real-time Localization
  63. EP251202a / GRB251202A: AstroSat CZTI detection
  64. GRB 251202A / EP251202a: SVOM/VT optical observation
  65. GRB 251201B: Fermi GBM Observation
  66. EP251202a/GRB 251202A: KAIT optical observations
  67. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  68. Fermi GRB 251202B: Global MASTER-Net observations report
  69. GRB 251202B: Fermi GBM Final Real-time Localization
  70. IPN triangulation of GRB 251129B (short/hard)
  71. GRB251129A/EP251129a: Swift UVOT detection
  72. GRB 251129B: AstroSat CZTI detection
  73. GRB 251202A: Fermi GBM Observation
  74. GRB 251202A: Swift/UVOT Detection
  75. GRB 251201B: Kilonova-Catcher optical afterglow detection
  76. GRB 251201B: Swift/UVOT Detection
  77. GRB 251130B: Glowbug gamma-ray detection
  78. GRB 251201B: GECAM-B observation of a long burst
  79. EP251130a: continued NOT optical observations indicate steep fading phase
  80. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  81. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  82. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  83. GRB 251202A: GOTO optical afterglow detection
  84. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  85. GRB 251201A: GECAM-B observation of a burst
  86. GRB 251126A: SAO RAS optical marginal detection
  87. GRB 251202A: Swift-XRT afterglow detection
  88. EP251129a/GRB 251129A: NOWT Detection
  89. GRB 251126A: SVOM/VT optical observation
  90. EP251130a: SVOM/VT optical observation
  91. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  92. Fermi GRB 251202A: Global MASTER-Net observations report
  93. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  94. GRB 251201B: Swift-XRT refined Analysis
  95. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  96. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  97. GRB 251202A: Fermi GBM Final Real-time Localization
  98. GRB 251201A: SVOM/GRM observation of a burst
  99. GRB 251201B: SVOM/VT optical fading
  100. Swift GRB 251201B : MASTER optical counterpart detection

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