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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: NOT optical observations
  2. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  3. GRB 251205A: Enhanced Swift-XRT position
  4. Swift GRB 251205A : MASTER OT detection with host galaxy
  5. GRB 251205A: Swift detection of a burst with an optical afterglow
  6. Swift GRB251205A: Global MASTER-Net observations report
  7. GRB 251126B: Fermi GBM Final Localization
  8. GRB 251203A: Insight-HXMT/HE detection
  9. GRB 251203C: SVOM/ECLAIRs refined analysis
  10. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  11. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  12. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  13. GRB 251202A: SVOM/GRM observation
  14. GRB 251203A: GECAM-B observation of a burst
  15. GRB 251203A: SVOM/GRM observation
  16. GRB 251201B: SALT spectroscopic redshift z = 1.599
  17. GRB 251203C: J-band observations with WINTER
  18. GRB 251129B: Glowbug gamma-ray detection of a short burst
  19. GRB 251203A: AstroSat CZTI detection
  20. EP251130a: JinShan near-infrared observations
  21. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  22. GRB 251203C: LCO optical afterglow confirmation
  23. GRB 251203C: SVOM/VT optical counterpart
  24. GRB 251203C: EP-FXT follow-up observation
  25. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  26. GRB 251129B: GECAM-B observation of a burst
  27. GRB 251203B: Swift-XRT observations
  28. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  29. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  30. GRB 251203C: LCO optical upper limits
  31. GRB 251203B: LCO optical upper limits
  32. GRB 251203B: SVOM/VT optical observation
  33. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  34. GRB 251203C: SVOM detection of a burst
  35. SVOM GRB251203.77: Global MASTER-Net observations report
  36. SVOM GRB251203B: Global MASTER-Net observations report
  37. GRB 251203B: SVOM detection of a burst
  38. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  39. GRB 251201B: Insight-HXMT/HE detection
  40. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  41. EP251130a: MAO/AZT-22 optical observations
  42. GRB 251203A: Fermi GBM Final Real-time Localization
  43. EP251202a / GRB251202A: AstroSat CZTI detection
  44. GRB 251202A / EP251202a: SVOM/VT optical observation
  45. GRB 251201B: Fermi GBM Observation
  46. EP251202a/GRB 251202A: KAIT optical observations
  47. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  48. Fermi GRB 251202B: Global MASTER-Net observations report
  49. GRB 251202B: Fermi GBM Final Real-time Localization
  50. IPN triangulation of GRB 251129B (short/hard)
  51. GRB251129A/EP251129a: Swift UVOT detection
  52. GRB 251129B: AstroSat CZTI detection
  53. GRB 251202A: Fermi GBM Observation
  54. GRB 251202A: Swift/UVOT Detection
  55. GRB 251201B: Kilonova-Catcher optical afterglow detection
  56. GRB 251201B: Swift/UVOT Detection
  57. GRB 251130B: Glowbug gamma-ray detection
  58. GRB 251201B: GECAM-B observation of a long burst
  59. EP251130a: continued NOT optical observations indicate steep fading phase
  60. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  61. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  62. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  63. GRB 251202A: GOTO optical afterglow detection
  64. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  65. GRB 251201A: GECAM-B observation of a burst
  66. GRB 251126A: SAO RAS optical marginal detection
  67. GRB 251202A: Swift-XRT afterglow detection
  68. EP251129a/GRB 251129A: NOWT Detection
  69. GRB 251126A: SVOM/VT optical observation
  70. EP251130a: SVOM/VT optical observation
  71. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  72. Fermi GRB 251202A: Global MASTER-Net observations report
  73. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  74. GRB 251201B: Swift-XRT refined Analysis
  75. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  76. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  77. GRB 251202A: Fermi GBM Final Real-time Localization
  78. GRB 251201A: SVOM/GRM observation of a burst
  79. GRB 251201B: SVOM/VT optical fading
  80. Swift GRB 251201B : MASTER optical counterpart detection
  81. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  82. Swift GRB 251201B: Global MASTER-Net observations report
  83. GRB 251201B: Enhanced Swift-XRT position
  84. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  85. GRB 251130B: AstroSat CZTI detection
  86. GRB 251201B: Swift detection of a burst with an optical counterpart
  87. GRB 251201B: Fermi GBM Final Real-time Localization
  88. EP251130a: Mondy optical observations
  89. EP251130a: Optical detections with Kinder observations
  90. SVOM GRB251201.19: Global MASTER-Net observations report
  91. EP251130a: SAO RAS optical observations
  92. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  93. EP251130a: KAIT optical observations
  94. EP251130A: Optical observation from 1.3m DFOT
  95. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  96. EP251130a: JinShan optical observations
  97. GRB 251201A: MAXI/GSC detection
  98. Fermi GRB 251130B: Global MASTER-Net observations report
  99. GRB 251127A: SVOM/GRM observation
  100. IceCube Alert 251130.75: Global MASTER-Net observations report

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