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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. EP251214a: Global MASTER-Net observations report
  2. GRB 251214B: Enhanced Swift-XRT position
  3. GRB 251214B: Xinglong-2.16m optical observation
  4. GRB 251214C: Fermi GBM Final Localization
  5. GRB 251214B : MASTER optical afterglow detection
  6. Fermi trigger No 787396657: Global MASTER-Net observations report
  7. GRB 251214B: SVOM/C-GFT optical observations
  8. EP251214a: COLIBRÍ optical upper limit
  9. Swift GRB 251214B: Global MASTER-Net observations report
  10. EP251214.305: COLIBRÍ optical upper limit
  11. GRB 251214B: Swift detection of a burst with an optical counterpart
  12. GRB 251214B: Fermi GBM Final Real-time Localization
  13. EP251214a: EP-WXT detection of an X-ray transient possibly associated with GRB 251214A
  14. Fermi GRB 251214A: Global MASTER-Net observations report
  15. GRB 251214A: Fermi GBM Final Real-time Localization
  16. EP251212a: Global MASTER-Net observations report
  17. EP251212a: KAIT optical upper limit
  18. EP251212a / GRB 251212A: AstroSat CZTI detection
  19. EP251212a: EP-FXT follow-up observation
  20. GRB 251211B: AstroSat CZTI detection
  21. IceCube-251210A: No Candidate Transients from the Zwicky Transient Facility
  22. GRB 251209A: NuSTAR detection of prompt emission
  23. EP251212a : COLIBRÍ optical upper limit
  24. EP251212a: Einstein Probe detection of an X-ray transient
  25. Fermi-LAT Gamma-ray Observations of IceCube-251210A
  26. IceCube-251210A: Upper limits from a search for additional neutrino events in IceCube
  27. Fermi GRB 251211B: Global MASTER-Net observations report
  28. GRB 251211B: Fermi GBM Final Real-time Localization
  29. IceCube-251210A: DDOTI Optical Upper Limit
  30. SVOM GRB251211.12: Global MASTER-Net observations report
  31. GRB 251211A: Fermi GBM Final Real-time Localization
  32. GRB 251209A: Fermi GBM observation
  33. GRB 251205A: 1.3m DFOT optical upper limit
  34. GRB 251209A: AstroSat CZTI detection
  35. IceCube Alert 251210.46: Global MASTER-Net observations report
  36. IceCube-251210A - IceCube observation of a high-energy neutrino candidate track-like event
  37. EP251124a: Mondy optical upper limit
  38. GRB 251129A/EP251129a: AbAO and Mondy optical observations
  39. EP251130a: Mondy and AbAO optical observations
  40. GRB 251208A: AstroSat CZTI detection
  41. Fermi GBM Sub-Threshold Detection of GRB 251205A
  42. GRB 251208A: Glowbug gamma-ray detection
  43. GRB 251208B: COLIBRÍ optical upper limits
  44. EP251118a / GRB 251118C: VLT/MUSE redshift confirmation
  45. GRB 251208C: GECAM-B observation of a short burst
  46. GRB 251208A: GECAM-B observation of a short burst
  47. Fermi GRB 251209A: Global MASTER-Net observations report
  48. Fermi GRB 251208C: Global MASTER-Net observations report
  49. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  50. GRB 251208B: Swift-XRT afterglow detection
  51. GRB 251208D: LAST optical upper limit
  52. GRB 251209A: Fermi GBM Final Real-time Localization
  53. GRB 251208D: LCO analysis of the XRT sources
  54. GRB 251208B: Fermi GBM Observation
  55. GRB 251208B: GROWTH-India Telescope optical upper limits
  56. GRB 251205A: J-band detection with WINTER
  57. GRB 251208D: Swift-XRT observations
  58. GRB 251208A: SVOM/GRM observation of a short burst
  59. GRB 251208C: SVOM/GRM observation of a short burst
  60. GRB 251129A: e-MERLIN C-band observations
  61. LAT GRB251208.43: Global MASTER-Net observations report
  62. GRB 251205A: Liverpool Telescope further optical follow-up observations
  63. GRB 251208D: LCO optical upper limits
  64. SVOM GRB251208D: Global MASTER-Net observations report
  65. GRB 251208B: Swift ToO observations
  66. GRB 251208B: Fermi-LAT detection
  67. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  68. GRB 251208D: SVOM possible detection of a faint burst
  69. GRB 251206A: SVOM detection of a burst through offline search
  70. GRB 251208C: Fermi GBM Final Real-time Localization
  71. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  72. GRB 251208B: Fermi GBM Final Real-time Localization
  73. GRB 251208A: Fermi GBM Final Real-time Localization
  74. GRB 251205A: FTW optical and NIR observations
  75. EP-WXT trigger 01709249380: KAIT confirmation of a stellar flare
  76. GRB 251205A: Liverpool Telescope further optical follow-up observations
  77. SVOM GRB251206.86: Global MASTER-Net observations report
  78. EP-WXT trigger 01709249380: confirmation of a stellar flare by BOOTES-5
  79. The EP-WXT trigger 01709249380 is likely a flaring star
  80. GRB 251205A: ZTF and ATLAS optical afterglow detections
  81. GRB 251205A: GROWTH-India Telescope optical observations
  82. GRB 251205A: Swift-BAT refined analysis
  83. GRB 251205A: Swift-XRT refined Analysis
  84. GRB 251205A: Swift/UVOT Detection
  85. GRB 251205A: Liverpool Telescope optical follow-up observations
  86. GRB 251203C: Swift/UVOT Upper Limit
  87. Konus-Wind detection of GRB 251118A
  88. GRB 251205A: Zeiss-1000 Koshka observatory optical observations
  89. GRB 251205A: COLIBRÍ optical observations
  90. GRB 251205A: GOTO optical afterglow detection
  91. GRB 251205A: NOT optical observations
  92. GRB 251205A: GTC/OSIRIS+ redshift z = 1.100
  93. GRB 251205A: Enhanced Swift-XRT position
  94. Swift GRB 251205A : MASTER OT detection with host galaxy
  95. GRB 251205A: Swift detection of a burst with an optical afterglow
  96. Swift GRB251205A: Global MASTER-Net observations report
  97. GRB 251126B: Fermi GBM Final Localization
  98. GRB 251203A: Insight-HXMT/HE detection
  99. GRB 251203C: SVOM/ECLAIRs refined analysis
  100. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate

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