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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. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  2. GRB 251203C: LCO optical afterglow confirmation
  3. GRB 251203C: SVOM/VT optical counterpart
  4. GRB 251203C: EP-FXT follow-up observation
  5. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  6. GRB 251129B: GECAM-B observation of a burst
  7. GRB 251203B: Swift-XRT observations
  8. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  9. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  10. GRB 251203C: LCO optical upper limits
  11. GRB 251203B: LCO optical upper limits
  12. GRB 251203B: SVOM/VT optical observation
  13. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  14. GRB 251203C: SVOM detection of a burst
  15. SVOM GRB251203.77: Global MASTER-Net observations report
  16. SVOM GRB251203B: Global MASTER-Net observations report
  17. GRB 251203B: SVOM detection of a burst
  18. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  19. GRB 251201B: Insight-HXMT/HE detection
  20. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  21. EP251130a: MAO/AZT-22 optical observations
  22. GRB 251203A: Fermi GBM Final Real-time Localization
  23. EP251202a / GRB251202A: AstroSat CZTI detection
  24. GRB 251202A / EP251202a: SVOM/VT optical observation
  25. GRB 251201B: Fermi GBM Observation
  26. EP251202a/GRB 251202A: KAIT optical observations
  27. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  28. Fermi GRB 251202B: Global MASTER-Net observations report
  29. GRB 251202B: Fermi GBM Final Real-time Localization
  30. IPN triangulation of GRB 251129B (short/hard)
  31. GRB251129A/EP251129a: Swift UVOT detection
  32. GRB 251129B: AstroSat CZTI detection
  33. GRB 251202A: Fermi GBM Observation
  34. GRB 251202A: Swift/UVOT Detection
  35. GRB 251201B: Kilonova-Catcher optical afterglow detection
  36. GRB 251201B: Swift/UVOT Detection
  37. GRB 251130B: Glowbug gamma-ray detection
  38. GRB 251201B: GECAM-B observation of a long burst
  39. EP251130a: continued NOT optical observations indicate steep fading phase
  40. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  41. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  42. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  43. GRB 251202A: GOTO optical afterglow detection
  44. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  45. GRB 251201A: GECAM-B observation of a burst
  46. GRB 251126A: SAO RAS optical marginal detection
  47. GRB 251202A: Swift-XRT afterglow detection
  48. EP251129a/GRB 251129A: NOWT Detection
  49. GRB 251126A: SVOM/VT optical observation
  50. EP251130a: SVOM/VT optical observation
  51. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  52. Fermi GRB 251202A: Global MASTER-Net observations report
  53. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  54. GRB 251201B: Swift-XRT refined Analysis
  55. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  56. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  57. GRB 251202A: Fermi GBM Final Real-time Localization
  58. GRB 251201A: SVOM/GRM observation of a burst
  59. GRB 251201B: SVOM/VT optical fading
  60. Swift GRB 251201B : MASTER optical counterpart detection
  61. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  62. Swift GRB 251201B: Global MASTER-Net observations report
  63. GRB 251201B: Enhanced Swift-XRT position
  64. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  65. GRB 251130B: AstroSat CZTI detection
  66. GRB 251201B: Swift detection of a burst with an optical counterpart
  67. GRB 251201B: Fermi GBM Final Real-time Localization
  68. EP251130a: Mondy optical observations
  69. EP251130a: Optical detections with Kinder observations
  70. SVOM GRB251201.19: Global MASTER-Net observations report
  71. EP251130a: SAO RAS optical observations
  72. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  73. EP251130a: KAIT optical observations
  74. EP251130A: Optical observation from 1.3m DFOT
  75. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  76. EP251130a: JinShan optical observations
  77. GRB 251201A: MAXI/GSC detection
  78. Fermi GRB 251130B: Global MASTER-Net observations report
  79. GRB 251127A: SVOM/GRM observation
  80. IceCube Alert 251130.75: Global MASTER-Net observations report
  81. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  82. EP251130a: Swift-XRT counterpart detection
  83. GRB 251130B: Fermi GBM Final Localization Correction
  84. EP251130a: Global MASTER-Net observations report
  85. GRB 251130B: Fermi GBM Final Real-time Localization
  86. EP251130a: COLIBRÍ optical counterpart candidate
  87. EP251130a: Einstein Probe detection of an X-ray transient
  88. EP251129a/GRB 251129A: EP-FXT follow-up observations
  89. GRB 251130A: Fermi GBM Final Real-time Localization
  90. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  91. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  92. GRB 251128A: AstroSat CZTI detection
  93. GRB 251129A / EP251129a: SAO RAS optical observations
  94. GRB 251126A: SAO RAS optical observations
  95. GRB 251128A: GECAM-B detection
  96. GRB 251128A: SVOM/GRM observation of a long burst
  97. GRB 251128A: Insight-HXMT/HE detection
  98. SVOM GRB 251129A : MASTER optical counterpart detection
  99. GRB 251129A: Swift-XRT afterglow detection
  100. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster

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