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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 251214B: 1.3m DFOT optical detection
  2. EP251214a: Global MASTER-Net observations report
  3. GRB 251214B: Enhanced Swift-XRT position
  4. GRB 251214B: Xinglong-2.16m optical observation
  5. GRB 251214C: Fermi GBM Final Localization
  6. GRB 251214B : MASTER optical afterglow detection
  7. Fermi trigger No 787396657: Global MASTER-Net observations report
  8. GRB 251214B: SVOM/C-GFT optical observations
  9. EP251214a: COLIBRÍ optical upper limit
  10. Swift GRB 251214B: Global MASTER-Net observations report
  11. EP251214.305: COLIBRÍ optical upper limit
  12. GRB 251214B: Swift detection of a burst with an optical counterpart
  13. GRB 251214B: Fermi GBM Final Real-time Localization
  14. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  15. Fermi GRB 251214A: Global MASTER-Net observations report
  16. GRB 251214A: Fermi GBM Final Real-time Localization
  17. EP251212a: Global MASTER-Net observations report
  18. EP251212a: KAIT optical upper limit
  19. EP251212a / GRB 251212A: AstroSat CZTI detection
  20. EP251212a: EP-FXT follow-up observation
  21. GRB 251211B: AstroSat CZTI detection
  22. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  23. GRB 251209A: NuSTAR detection of prompt emission
  24. EP251212a : COLIBRÍ optical upper limit
  25. EP251212a: Einstein Probe detection of an X-ray transient
  26. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  27. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  28. Fermi GRB 251211B: Global MASTER-Net observations report
  29. GRB 251211B: Fermi GBM Final Real-time Localization
  30. IceCube-251210A: DDOTI Optical Upper Limit
  31. SVOM GRB251211.12: Global MASTER-Net observations report
  32. GRB 251211A: Fermi GBM Final Real-time Localization
  33. GRB 251209A: Fermi GBM observation
  34. GRB 251205A: 1.3m DFOT optical upper limit
  35. GRB 251209A: AstroSat CZTI detection
  36. IceCube Alert 251210.46: Global MASTER-Net observations report
  37. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  38. EP251124a: Mondy optical upper limit
  39. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  40. EP251130a: Mondy and AbAO optical observations
  41. GRB 251208A: AstroSat CZTI detection
  42. Fermi GBM Sub-Threshold Detection of GRB 251205A
  43. GRB 251208A: Glowbug gamma-ray detection
  44. GRB 251208B: COLIBRÍ optical upper limits
  45. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  46. GRB 251208C: GECAM-B observation of a short burst
  47. GRB 251208A: GECAM-B observation of a short burst
  48. Fermi GRB 251209A: Global MASTER-Net observations report
  49. Fermi GRB 251208C: Global MASTER-Net observations report
  50. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  51. GRB 251208B: Swift-XRT afterglow detection
  52. GRB 251208D: LAST optical upper limit
  53. GRB 251209A: Fermi GBM Final Real-time Localization
  54. GRB 251208D: LCO analysis of the XRT sources
  55. GRB 251208B: Fermi GBM Observation
  56. GRB 251208B: GROWTH-India Telescope optical upper limits
  57. GRB 251205A: J-band detection with WINTER
  58. GRB 251208D: Swift-XRT observations
  59. GRB 251208A: SVOM/GRM observation of a short burst
  60. GRB 251208C: SVOM/GRM observation of a short burst
  61. GRB 251129A: e-MERLIN C-band observations
  62. LAT GRB251208.43: Global MASTER-Net observations report
  63. GRB 251205A: Liverpool Telescope further optical follow-up observations
  64. GRB 251208D: LCO optical upper limits
  65. SVOM GRB251208D: Global MASTER-Net observations report
  66. GRB 251208B: Swift ToO observations
  67. GRB 251208B: Fermi-LAT detection
  68. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  69. GRB 251208D: SVOM possible detection of a faint burst
  70. GRB 251206A: SVOM detection of a burst through offline search
  71. GRB 251208C: Fermi GBM Final Real-time Localization
  72. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  73. GRB 251208B: Fermi GBM Final Real-time Localization
  74. GRB 251208A: Fermi GBM Final Real-time Localization
  75. GRB 251205A: FTW optical and NIR observations
  76. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  77. GRB 251205A: Liverpool Telescope further optical follow-up observations
  78. SVOM GRB251206.86: Global MASTER-Net observations report
  79. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  80. The EP-WXT trigger 01709249380 is likely a flaring star
  81. GRB 251205A: ZTF and ATLAS optical afterglow detections
  82. GRB 251205A: GROWTH-India Telescope optical observations
  83. GRB 251205A: Swift-BAT refined analysis
  84. GRB 251205A: Swift-XRT refined Analysis
  85. GRB 251205A: Swift/UVOT Detection
  86. GRB 251205A: Liverpool Telescope optical follow-up observations
  87. GRB 251203C: Swift/UVOT Upper Limit
  88. Konus-Wind detection of GRB 251118A
  89. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  90. GRB 251205A: COLIBRÍ optical observations
  91. GRB 251205A: GOTO optical afterglow detection
  92. GRB 251205A: NOT optical observations
  93. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  94. GRB 251205A: Enhanced Swift-XRT position
  95. Swift GRB 251205A : MASTER OT detection with host galaxy
  96. GRB 251205A: Swift detection of a burst with an optical afterglow
  97. Swift GRB251205A: Global MASTER-Net observations report
  98. GRB 251126B: Fermi GBM Final Localization
  99. GRB 251203A: Insight-HXMT/HE detection
  100. GRB 251203C: SVOM/ECLAIRs refined analysis

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