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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: Zeiss-1000 Koshka observatory optical observations
  2. GRB 251205A: COLIBRÍ optical observations
  3. GRB 251205A: GOTO optical afterglow detection
  4. GRB 251205A: NOT optical observations
  5. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  6. GRB 251205A: Enhanced Swift-XRT position
  7. Swift GRB 251205A : MASTER OT detection with host galaxy
  8. GRB 251205A: Swift detection of a burst with an optical afterglow
  9. Swift GRB251205A: Global MASTER-Net observations report
  10. GRB 251126B: Fermi GBM Final Localization
  11. GRB 251203A: Insight-HXMT/HE detection
  12. GRB 251203C: SVOM/ECLAIRs refined analysis
  13. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  14. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  15. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  16. GRB 251202A: SVOM/GRM observation
  17. GRB 251203A: GECAM-B observation of a burst
  18. GRB 251203A: SVOM/GRM observation
  19. GRB 251201B: SALT spectroscopic redshift z = 1.599
  20. GRB 251203C: J-band observations with WINTER
  21. GRB 251129B: Glowbug gamma-ray detection of a short burst
  22. GRB 251203A: AstroSat CZTI detection
  23. EP251130a: JinShan near-infrared observations
  24. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  25. GRB 251203C: LCO optical afterglow confirmation
  26. GRB 251203C: SVOM/VT optical counterpart
  27. GRB 251203C: EP-FXT follow-up observation
  28. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  29. GRB 251129B: GECAM-B observation of a burst
  30. GRB 251203B: Swift-XRT observations
  31. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  32. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  33. GRB 251203C: LCO optical upper limits
  34. GRB 251203B: LCO optical upper limits
  35. GRB 251203B: SVOM/VT optical observation
  36. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  37. GRB 251203C: SVOM detection of a burst
  38. SVOM GRB251203.77: Global MASTER-Net observations report
  39. SVOM GRB251203B: Global MASTER-Net observations report
  40. GRB 251203B: SVOM detection of a burst
  41. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  42. GRB 251201B: Insight-HXMT/HE detection
  43. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  44. EP251130a: MAO/AZT-22 optical observations
  45. GRB 251203A: Fermi GBM Final Real-time Localization
  46. EP251202a / GRB251202A: AstroSat CZTI detection
  47. GRB 251202A / EP251202a: SVOM/VT optical observation
  48. GRB 251201B: Fermi GBM Observation
  49. EP251202a/GRB 251202A: KAIT optical observations
  50. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  51. Fermi GRB 251202B: Global MASTER-Net observations report
  52. GRB 251202B: Fermi GBM Final Real-time Localization
  53. IPN triangulation of GRB 251129B (short/hard)
  54. GRB251129A/EP251129a: Swift UVOT detection
  55. GRB 251129B: AstroSat CZTI detection
  56. GRB 251202A: Fermi GBM Observation
  57. GRB 251202A: Swift/UVOT Detection
  58. GRB 251201B: Kilonova-Catcher optical afterglow detection
  59. GRB 251201B: Swift/UVOT Detection
  60. GRB 251130B: Glowbug gamma-ray detection
  61. GRB 251201B: GECAM-B observation of a long burst
  62. EP251130a: continued NOT optical observations indicate steep fading phase
  63. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  64. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  65. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  66. GRB 251202A: GOTO optical afterglow detection
  67. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  68. GRB 251201A: GECAM-B observation of a burst
  69. GRB 251126A: SAO RAS optical marginal detection
  70. GRB 251202A: Swift-XRT afterglow detection
  71. EP251129a/GRB 251129A: NOWT Detection
  72. GRB 251126A: SVOM/VT optical observation
  73. EP251130a: SVOM/VT optical observation
  74. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  75. Fermi GRB 251202A: Global MASTER-Net observations report
  76. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  77. GRB 251201B: Swift-XRT refined Analysis
  78. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  79. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  80. GRB 251202A: Fermi GBM Final Real-time Localization
  81. GRB 251201A: SVOM/GRM observation of a burst
  82. GRB 251201B: SVOM/VT optical fading
  83. Swift GRB 251201B : MASTER optical counterpart detection
  84. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  85. Swift GRB 251201B: Global MASTER-Net observations report
  86. GRB 251201B: Enhanced Swift-XRT position
  87. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  88. GRB 251130B: AstroSat CZTI detection
  89. GRB 251201B: Swift detection of a burst with an optical counterpart
  90. GRB 251201B: Fermi GBM Final Real-time Localization
  91. EP251130a: Mondy optical observations
  92. EP251130a: Optical detections with Kinder observations
  93. SVOM GRB251201.19: Global MASTER-Net observations report
  94. EP251130a: SAO RAS optical observations
  95. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  96. EP251130a: KAIT optical observations
  97. EP251130A: Optical observation from 1.3m DFOT
  98. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  99. EP251130a: JinShan optical observations
  100. GRB 251201A: MAXI/GSC detection

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