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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 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  2. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  3. GRB 251202A: SVOM/GRM observation
  4. GRB 251203A: GECAM-B observation of a burst
  5. GRB 251203A: SVOM/GRM observation
  6. GRB 251201B: SALT spectroscopic redshift z = 1.599
  7. GRB 251203C: J-band observations with WINTER
  8. GRB 251129B: Glowbug gamma-ray detection of a short burst
  9. GRB 251203A: AstroSat CZTI detection
  10. EP251130a: JinShan near-infrared observations
  11. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  12. GRB 251203C: LCO optical afterglow confirmation
  13. GRB 251203C: SVOM/VT optical counterpart
  14. GRB 251203C: EP-FXT follow-up observation
  15. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  16. GRB 251129B: GECAM-B observation of a burst
  17. GRB 251203B: Swift-XRT observations
  18. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  19. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  20. GRB 251203C: LCO optical upper limits
  21. GRB 251203B: LCO optical upper limits
  22. GRB 251203B: SVOM/VT optical observation
  23. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  24. GRB 251203C: SVOM detection of a burst
  25. SVOM GRB251203.77: Global MASTER-Net observations report
  26. SVOM GRB251203B: Global MASTER-Net observations report
  27. GRB 251203B: SVOM detection of a burst
  28. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  29. GRB 251201B: Insight-HXMT/HE detection
  30. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  31. EP251130a: MAO/AZT-22 optical observations
  32. GRB 251203A: Fermi GBM Final Real-time Localization
  33. EP251202a / GRB251202A: AstroSat CZTI detection
  34. GRB 251202A / EP251202a: SVOM/VT optical observation
  35. GRB 251201B: Fermi GBM Observation
  36. EP251202a/GRB 251202A: KAIT optical observations
  37. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  38. Fermi GRB 251202B: Global MASTER-Net observations report
  39. GRB 251202B: Fermi GBM Final Real-time Localization
  40. IPN triangulation of GRB 251129B (short/hard)
  41. GRB251129A/EP251129a: Swift UVOT detection
  42. GRB 251129B: AstroSat CZTI detection
  43. GRB 251202A: Fermi GBM Observation
  44. GRB 251202A: Swift/UVOT Detection
  45. GRB 251201B: Kilonova-Catcher optical afterglow detection
  46. GRB 251201B: Swift/UVOT Detection
  47. GRB 251130B: Glowbug gamma-ray detection
  48. GRB 251201B: GECAM-B observation of a long burst
  49. EP251130a: continued NOT optical observations indicate steep fading phase
  50. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  51. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  52. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  53. GRB 251202A: GOTO optical afterglow detection
  54. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  55. GRB 251201A: GECAM-B observation of a burst
  56. GRB 251126A: SAO RAS optical marginal detection
  57. GRB 251202A: Swift-XRT afterglow detection
  58. EP251129a/GRB 251129A: NOWT Detection
  59. GRB 251126A: SVOM/VT optical observation
  60. EP251130a: SVOM/VT optical observation
  61. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  62. Fermi GRB 251202A: Global MASTER-Net observations report
  63. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  64. GRB 251201B: Swift-XRT refined Analysis
  65. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  66. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  67. GRB 251202A: Fermi GBM Final Real-time Localization
  68. GRB 251201A: SVOM/GRM observation of a burst
  69. GRB 251201B: SVOM/VT optical fading
  70. Swift GRB 251201B : MASTER optical counterpart detection
  71. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  72. Swift GRB 251201B: Global MASTER-Net observations report
  73. GRB 251201B: Enhanced Swift-XRT position
  74. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  75. GRB 251130B: AstroSat CZTI detection
  76. GRB 251201B: Swift detection of a burst with an optical counterpart
  77. GRB 251201B: Fermi GBM Final Real-time Localization
  78. EP251130a: Mondy optical observations
  79. EP251130a: Optical detections with Kinder observations
  80. SVOM GRB251201.19: Global MASTER-Net observations report
  81. EP251130a: SAO RAS optical observations
  82. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  83. EP251130a: KAIT optical observations
  84. EP251130A: Optical observation from 1.3m DFOT
  85. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  86. EP251130a: JinShan optical observations
  87. GRB 251201A: MAXI/GSC detection
  88. Fermi GRB 251130B: Global MASTER-Net observations report
  89. GRB 251127A: SVOM/GRM observation
  90. IceCube Alert 251130.75: Global MASTER-Net observations report
  91. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  92. EP251130a: Swift-XRT counterpart detection
  93. GRB 251130B: Fermi GBM Final Localization Correction
  94. EP251130a: Global MASTER-Net observations report
  95. GRB 251130B: Fermi GBM Final Real-time Localization
  96. EP251130a: COLIBRÍ optical counterpart candidate
  97. EP251130a: Einstein Probe detection of an X-ray transient
  98. EP251129a/GRB 251129A: EP-FXT follow-up observations
  99. GRB 251130A: Fermi GBM Final Real-time Localization
  100. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460

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