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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 251208D: LCO optical upper limits
  2. SVOM GRB251208D: Global MASTER-Net observations report
  3. GRB 251208B: Swift ToO observations
  4. GRB 251208B: Fermi-LAT detection
  5. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  6. GRB 251208D: SVOM possible detection of a faint burst
  7. GRB 251206A: SVOM detection of a burst through offline search
  8. GRB 251208C: Fermi GBM Final Real-time Localization
  9. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  10. GRB 251208B: Fermi GBM Final Real-time Localization
  11. GRB 251208A: Fermi GBM Final Real-time Localization
  12. GRB 251205A: FTW optical and NIR observations
  13. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  14. GRB 251205A: Liverpool Telescope further optical follow-up observations
  15. SVOM GRB251206.86: Global MASTER-Net observations report
  16. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  17. The EP-WXT trigger 01709249380 is likely a flaring star
  18. GRB 251205A: ZTF and ATLAS optical afterglow detections
  19. GRB 251205A: GROWTH-India Telescope optical observations
  20. GRB 251205A: Swift-BAT refined analysis
  21. GRB 251205A: Swift-XRT refined Analysis
  22. GRB 251205A: Swift/UVOT Detection
  23. GRB 251205A: Liverpool Telescope optical follow-up observations
  24. GRB 251203C: Swift/UVOT Upper Limit
  25. Konus-Wind detection of GRB 251118A
  26. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  27. GRB 251205A: COLIBRÍ optical observations
  28. GRB 251205A: GOTO optical afterglow detection
  29. GRB 251205A: NOT optical observations
  30. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  31. GRB 251205A: Enhanced Swift-XRT position
  32. Swift GRB 251205A : MASTER OT detection with host galaxy
  33. GRB 251205A: Swift detection of a burst with an optical afterglow
  34. Swift GRB251205A: Global MASTER-Net observations report
  35. GRB 251126B: Fermi GBM Final Localization
  36. GRB 251203A: Insight-HXMT/HE detection
  37. GRB 251203C: SVOM/ECLAIRs refined analysis
  38. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  39. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  40. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  41. GRB 251202A: SVOM/GRM observation
  42. GRB 251203A: GECAM-B observation of a burst
  43. GRB 251203A: SVOM/GRM observation
  44. GRB 251201B: SALT spectroscopic redshift z = 1.599
  45. GRB 251203C: J-band observations with WINTER
  46. GRB 251129B: Glowbug gamma-ray detection of a short burst
  47. GRB 251203A: AstroSat CZTI detection
  48. EP251130a: JinShan near-infrared observations
  49. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  50. GRB 251203C: LCO optical afterglow confirmation
  51. GRB 251203C: SVOM/VT optical counterpart
  52. GRB 251203C: EP-FXT follow-up observation
  53. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  54. GRB 251129B: GECAM-B observation of a burst
  55. GRB 251203B: Swift-XRT observations
  56. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  57. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  58. GRB 251203C: LCO optical upper limits
  59. GRB 251203B: LCO optical upper limits
  60. GRB 251203B: SVOM/VT optical observation
  61. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  62. GRB 251203C: SVOM detection of a burst
  63. SVOM GRB251203.77: Global MASTER-Net observations report
  64. SVOM GRB251203B: Global MASTER-Net observations report
  65. GRB 251203B: SVOM detection of a burst
  66. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  67. GRB 251201B: Insight-HXMT/HE detection
  68. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  69. EP251130a: MAO/AZT-22 optical observations
  70. GRB 251203A: Fermi GBM Final Real-time Localization
  71. EP251202a / GRB251202A: AstroSat CZTI detection
  72. GRB 251202A / EP251202a: SVOM/VT optical observation
  73. GRB 251201B: Fermi GBM Observation
  74. EP251202a/GRB 251202A: KAIT optical observations
  75. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  76. Fermi GRB 251202B: Global MASTER-Net observations report
  77. GRB 251202B: Fermi GBM Final Real-time Localization
  78. IPN triangulation of GRB 251129B (short/hard)
  79. GRB251129A/EP251129a: Swift UVOT detection
  80. GRB 251129B: AstroSat CZTI detection
  81. GRB 251202A: Fermi GBM Observation
  82. GRB 251202A: Swift/UVOT Detection
  83. GRB 251201B: Kilonova-Catcher optical afterglow detection
  84. GRB 251201B: Swift/UVOT Detection
  85. GRB 251130B: Glowbug gamma-ray detection
  86. GRB 251201B: GECAM-B observation of a long burst
  87. EP251130a: continued NOT optical observations indicate steep fading phase
  88. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  89. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  90. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  91. GRB 251202A: GOTO optical afterglow detection
  92. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  93. GRB 251201A: GECAM-B observation of a burst
  94. GRB 251126A: SAO RAS optical marginal detection
  95. GRB 251202A: Swift-XRT afterglow detection
  96. EP251129a/GRB 251129A: NOWT Detection
  97. GRB 251126A: SVOM/VT optical observation
  98. EP251130a: SVOM/VT optical observation
  99. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  100. Fermi GRB 251202A: Global MASTER-Net observations report

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