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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"

28090 results found.

  1. GRB 251206A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  2. GRB 251208B: Swift-XRT afterglow detection
  3. GRB 251208D: LAST optical upper limit
  4. GRB 251208D: LCO analysis of the XRT sources
  5. GRB 251208B: Fermi GBM Observation
  6. GRB 251208B: GROWTH-India Telescope optical upper limits
  7. GRB 251205A: J-band detection with WINTER
  8. GRB 251208D: Swift-XRT observations
  9. GRB 251208A: SVOM/GRM observation of a short burst
  10. GRB 251208C: SVOM/GRM observation of a short burst
  11. GRB 251129A: e-MERLIN C-band observations
  12. LAT GRB251208.43: Global MASTER-Net observations report
  13. GRB 251205A: Liverpool Telescope further optical follow-up observations
  14. GRB 251208D: LCO optical upper limits
  15. SVOM GRB251208D: Global MASTER-Net observations report
  16. GRB 251208B: Fermi-LAT detection
  17. GRB 251208B: Swift/BAT-GUANO arcminute localization of a burst
  18. GRB 251208D: SVOM possible detection of a faint burst
  19. GRB 251205A : MITSuME Akeno optical afterglow candidate detection
  20. GRB 251205A: Liverpool Telescope further optical follow-up observations
  21. SVOM GRB251206.86: Global MASTER-Net observations report
  22. GRB 251205A: GROWTH-India Telescope optical observations
  23. GRB 251205A: Swift-BAT refined analysis
  24. GRB 251205A: Swift-XRT refined Analysis
  25. GRB 251205A: Swift/UVOT Detection
  26. GRB 251205A: Liverpool Telescope optical follow-up observations
  27. GRB 251203C: Swift/UVOT Upper Limit
  28. GRB 251205A: COLIBRÍ optical observations
  29. GRB 251205A: NOT optical observations
  30. GRB 251205A: Enhanced Swift-XRT position
  31. Swift GRB 251205A : MASTER OT detection with host galaxy
  32. GRB 251205A: Swift detection of a burst with an optical afterglow
  33. Swift GRB251205A: Global MASTER-Net observations report
  34. SVOM/sb25120502: SVOM detection of a faint X-ray transient candidate
  35. GRB 251202A / EP251202a: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 40-cm and 1-m telescopes at McDonald Observatory
  36. GRB 251203C: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  37. GRB 251202A: SVOM/GRM observation
  38. GRB 251203A: GECAM-B observation of a burst
  39. GRB 251203A: SVOM/GRM observation
  40. GRB 251203C: J-band observations with WINTER
  41. GRB 251129B: Glowbug gamma-ray detection of a short burst
  42. GRB 251203A: AstroSat CZTI detection
  43. GRB 251203C: SVOM/VT optical counterpart
  44. GRB 251203C: EP-FXT follow-up observation
  45. GRB 251203B: Swift-XRT observations
  46. GRB 251203C: LCO optical upper limits
  47. GRB 251203B: LCO optical upper limits
  48. GRB 251203B: SVOM/VT optical observation
  49. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  50. SVOM GRB251203.77: Global MASTER-Net observations report
  51. SVOM GRB251203B: Global MASTER-Net observations report
  52. GRB 251203B: SVOM detection of a burst
  53. EP251130a: MAO/AZT-22 optical observations
  54. GRB 251201B: Fermi GBM Observation
  55. EP251202a/GRB 251202A: KAIT optical observations
  56. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  57. Fermi GRB 251202B: Global MASTER-Net observations report
  58. IPN triangulation of GRB 251129B (short/hard)
  59. GRB251129A/EP251129a: Swift UVOT detection
  60. GRB 251202A: Fermi GBM Observation
  61. GRB 251202A: Swift/UVOT Detection
  62. GRB 251201B: Kilonova-Catcher optical afterglow detection
  63. GRB 251201B: Swift/UVOT Detection
  64. GRB 251130B: Glowbug gamma-ray detection
  65. EP251130a: continued NOT optical observations indicate steep fading phase
  66. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  67. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  68. GRB 251126A: SAO RAS optical marginal detection
  69. GRB 251202A: Swift-XRT afterglow detection
  70. EP251129a/GRB 251129A: NOWT Detection
  71. GRB 251126A: SVOM/VT optical observation
  72. EP251130a: SVOM/VT optical observation
  73. Fermi GRB 251202A: Global MASTER-Net observations report
  74. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  75. GRB 251201B: Swift-XRT refined Analysis
  76. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  77. GRB 251201A: SVOM/GRM observation of a burst
  78. GRB 251201B: SVOM/VT optical fading
  79. Swift GRB 251201B : MASTER optical counterpart detection
  80. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  81. Swift GRB 251201B: Global MASTER-Net observations report
  82. GRB 251201B: Enhanced Swift-XRT position
  83. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  84. GRB 251201B: Swift detection of a burst with an optical counterpart
  85. GRB 251201B: Fermi GBM Final Real-time Localization
  86. EP251130a: Mondy optical observations
  87. EP251130a: Optical detections with Kinder observations
  88. SVOM GRB251201.19: Global MASTER-Net observations report
  89. EP251130a: SAO RAS optical observations
  90. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  91. EP251130A: Optical observation from 1.3m DFOT
  92. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  93. EP251130a: JinShan optical observations
  94. GRB 251201A: MAXI/GSC detection
  95. Fermi GRB 251130B: Global MASTER-Net observations report
  96. GRB 251127A: SVOM/GRM observation
  97. IceCube Alert 251130.75: Global MASTER-Net observations report
  98. EP251130a: Swift-XRT counterpart detection
  99. EP251130a: Global MASTER-Net observations report
  100. EP251130a: COLIBRÍ optical counterpart candidate

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