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

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