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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 251208B: Fermi GBM Observation
  2. GRB 251208B: GROWTH-India Telescope optical upper limits
  3. GRB 251205A: J-band detection with WINTER
  4. GRB 251208D: Swift-XRT observations
  5. GRB 251208A: SVOM/GRM observation of a short burst
  6. GRB 251208C: SVOM/GRM observation of a short burst
  7. GRB 251129A: e-MERLIN C-band observations
  8. LAT GRB251208.43: Global MASTER-Net observations report
  9. GRB 251205A: Liverpool Telescope further optical follow-up observations
  10. GRB 251208D: LCO optical upper limits
  11. SVOM GRB251208D: Global MASTER-Net observations report
  12. GRB 251208B: Swift ToO observations
  13. GRB 251208B: Fermi-LAT detection
  14. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  15. GRB 251208D: SVOM possible detection of a faint burst
  16. GRB 251206A: SVOM detection of a burst through offline search
  17. GRB 251208C: Fermi GBM Final Real-time Localization
  18. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  19. GRB 251208B: Fermi GBM Final Real-time Localization
  20. GRB 251208A: Fermi GBM Final Real-time Localization
  21. GRB 251205A: FTW optical and NIR observations
  22. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  23. GRB 251205A: Liverpool Telescope further optical follow-up observations
  24. SVOM GRB251206.86: Global MASTER-Net observations report
  25. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  26. The EP-WXT trigger 01709249380 is likely a flaring star
  27. GRB 251205A: ZTF and ATLAS optical afterglow detections
  28. GRB 251205A: GROWTH-India Telescope optical observations
  29. GRB 251205A: Swift-BAT refined analysis
  30. GRB 251205A: Swift-XRT refined Analysis
  31. GRB 251205A: Swift/UVOT Detection
  32. GRB 251205A: Liverpool Telescope optical follow-up observations
  33. GRB 251203C: Swift/UVOT Upper Limit
  34. Konus-Wind detection of GRB 251118A
  35. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  36. GRB 251205A: COLIBRÍ optical observations
  37. GRB 251205A: GOTO optical afterglow detection
  38. GRB 251205A: NOT optical observations
  39. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  40. GRB 251205A: Enhanced Swift-XRT position
  41. Swift GRB 251205A : MASTER OT detection with host galaxy
  42. GRB 251205A: Swift detection of a burst with an optical afterglow
  43. Swift GRB251205A: Global MASTER-Net observations report
  44. GRB 251126B: Fermi GBM Final Localization
  45. GRB 251203A: Insight-HXMT/HE detection
  46. GRB 251203C: SVOM/ECLAIRs refined analysis
  47. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  48. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  49. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 251202A: SVOM/GRM observation
  51. GRB 251203A: GECAM-B observation of a burst
  52. GRB 251203A: SVOM/GRM observation
  53. GRB 251201B: SALT spectroscopic redshift z = 1.599
  54. GRB 251203C: J-band observations with WINTER
  55. GRB 251129B: Glowbug gamma-ray detection of a short burst
  56. GRB 251203A: AstroSat CZTI detection
  57. EP251130a: JinShan near-infrared observations
  58. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  59. GRB 251203C: LCO optical afterglow confirmation
  60. GRB 251203C: SVOM/VT optical counterpart
  61. GRB 251203C: EP-FXT follow-up observation
  62. GRB 251129A/EP251129a : SVOM/ECLAIRs refined analysis
  63. GRB 251129B: GECAM-B observation of a burst
  64. GRB 251203B: Swift-XRT observations
  65. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  66. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  67. GRB 251203C: LCO optical upper limits
  68. GRB 251203B: LCO optical upper limits
  69. GRB 251203B: SVOM/VT optical observation
  70. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  71. GRB 251203C: SVOM detection of a burst
  72. SVOM GRB251203.77: Global MASTER-Net observations report
  73. SVOM GRB251203B: Global MASTER-Net observations report
  74. GRB 251203B: SVOM detection of a burst
  75. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  76. GRB 251201B: Insight-HXMT/HE detection
  77. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  78. EP251130a: MAO/AZT-22 optical observations
  79. GRB 251203A: Fermi GBM Final Real-time Localization
  80. EP251202a / GRB251202A: AstroSat CZTI detection
  81. GRB 251202A / EP251202a: SVOM/VT optical observation
  82. GRB 251201B: Fermi GBM Observation
  83. EP251202a/GRB 251202A: KAIT optical observations
  84. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  85. Fermi GRB 251202B: Global MASTER-Net observations report
  86. GRB 251202B: Fermi GBM Final Real-time Localization
  87. IPN triangulation of GRB 251129B (short/hard)
  88. GRB251129A/EP251129a: Swift UVOT detection
  89. GRB 251129B: AstroSat CZTI detection
  90. GRB 251202A: Fermi GBM Observation
  91. GRB 251202A: Swift/UVOT Detection
  92. GRB 251201B: Kilonova-Catcher optical afterglow detection
  93. GRB 251201B: Swift/UVOT Detection
  94. GRB 251130B: Glowbug gamma-ray detection
  95. GRB 251201B: GECAM-B observation of a long burst
  96. EP251130a: continued NOT optical observations indicate steep fading phase
  97. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  98. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  99. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  100. GRB 251202A: GOTO optical afterglow detection

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