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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 GRB 251214A: Global MASTER-Net observations report
  2. GRB 251214A: Fermi GBM Final Real-time Localization
  3. EP251212a: Global MASTER-Net observations report
  4. EP251212a: KAIT optical upper limit
  5. EP251212a / GRB 251212A: AstroSat CZTI detection
  6. EP251212a: EP-FXT follow-up observation
  7. GRB 251211B: AstroSat CZTI detection
  8. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  9. GRB 251209A: NuSTAR detection of prompt emission
  10. EP251212a : COLIBRÍ optical upper limit
  11. EP251212a: Einstein Probe detection of an X-ray transient
  12. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  13. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  14. Fermi GRB 251211B: Global MASTER-Net observations report
  15. GRB 251211B: Fermi GBM Final Real-time Localization
  16. IceCube-251210A: DDOTI Optical Upper Limit
  17. SVOM GRB251211.12: Global MASTER-Net observations report
  18. GRB 251211A: Fermi GBM Final Real-time Localization
  19. GRB 251209A: Fermi GBM observation
  20. GRB 251205A: 1.3m DFOT optical upper limit
  21. GRB 251209A: AstroSat CZTI detection
  22. IceCube Alert 251210.46: Global MASTER-Net observations report
  23. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  24. EP251124a: Mondy optical upper limit
  25. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  26. EP251130a: Mondy and AbAO optical observations
  27. GRB 251208A: AstroSat CZTI detection
  28. Fermi GBM Sub-Threshold Detection of GRB 251205A
  29. GRB 251208A: Glowbug gamma-ray detection
  30. GRB 251208B: COLIBRÍ optical upper limits
  31. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  32. GRB 251208C: GECAM-B observation of a short burst
  33. GRB 251208A: GECAM-B observation of a short burst
  34. Fermi GRB 251209A: Global MASTER-Net observations report
  35. Fermi GRB 251208C: Global MASTER-Net observations report
  36. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. GRB 251208B: Swift-XRT afterglow detection
  38. GRB 251208D: LAST optical upper limit
  39. GRB 251209A: Fermi GBM Final Real-time Localization
  40. GRB 251208D: LCO analysis of the XRT sources
  41. GRB 251208B: Fermi GBM Observation
  42. GRB 251208B: GROWTH-India Telescope optical upper limits
  43. GRB 251205A: J-band detection with WINTER
  44. GRB 251208D: Swift-XRT observations
  45. GRB 251208A: SVOM/GRM observation of a short burst
  46. GRB 251208C: SVOM/GRM observation of a short burst
  47. GRB 251129A: e-MERLIN C-band observations
  48. LAT GRB251208.43: Global MASTER-Net observations report
  49. GRB 251205A: Liverpool Telescope further optical follow-up observations
  50. GRB 251208D: LCO optical upper limits
  51. SVOM GRB251208D: Global MASTER-Net observations report
  52. GRB 251208B: Swift ToO observations
  53. GRB 251208B: Fermi-LAT detection
  54. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  55. GRB 251208D: SVOM possible detection of a faint burst
  56. GRB 251206A: SVOM detection of a burst through offline search
  57. GRB 251208C: Fermi GBM Final Real-time Localization
  58. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  59. GRB 251208B: Fermi GBM Final Real-time Localization
  60. GRB 251208A: Fermi GBM Final Real-time Localization
  61. GRB 251205A: FTW optical and NIR observations
  62. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  63. GRB 251205A: Liverpool Telescope further optical follow-up observations
  64. SVOM GRB251206.86: Global MASTER-Net observations report
  65. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  66. The EP-WXT trigger 01709249380 is likely a flaring star
  67. GRB 251205A: ZTF and ATLAS optical afterglow detections
  68. GRB 251205A: GROWTH-India Telescope optical observations
  69. GRB 251205A: Swift-BAT refined analysis
  70. GRB 251205A: Swift-XRT refined Analysis
  71. GRB 251205A: Swift/UVOT Detection
  72. GRB 251205A: Liverpool Telescope optical follow-up observations
  73. GRB 251203C: Swift/UVOT Upper Limit
  74. Konus-Wind detection of GRB 251118A
  75. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  76. GRB 251205A: COLIBRÍ optical observations
  77. GRB 251205A: GOTO optical afterglow detection
  78. GRB 251205A: NOT optical observations
  79. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  80. GRB 251205A: Enhanced Swift-XRT position
  81. Swift GRB 251205A : MASTER OT detection with host galaxy
  82. GRB 251205A: Swift detection of a burst with an optical afterglow
  83. Swift GRB251205A: Global MASTER-Net observations report
  84. GRB 251126B: Fermi GBM Final Localization
  85. GRB 251203A: Insight-HXMT/HE detection
  86. GRB 251203C: SVOM/ECLAIRs refined analysis
  87. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  88. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  89. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  90. GRB 251202A: SVOM/GRM observation
  91. GRB 251203A: GECAM-B observation of a burst
  92. GRB 251203A: SVOM/GRM observation
  93. GRB 251201B: SALT spectroscopic redshift z = 1.599
  94. GRB 251203C: J-band observations with WINTER
  95. GRB 251129B: Glowbug gamma-ray detection of a short burst
  96. GRB 251203A: AstroSat CZTI detection
  97. EP251130a: JinShan near-infrared observations
  98. Fermi Gamma-ray Burst Monitor trigger 786496343/251203967 is not a GRB
  99. GRB 251203C: LCO optical afterglow confirmation
  100. GRB 251203C: SVOM/VT optical counterpart

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