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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 251201B: Insight-HXMT/HE detection
  2. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  3. EP251130a: MAO/AZT-22 optical observations
  4. GRB 251203A: Fermi GBM Final Real-time Localization
  5. EP251202a / GRB251202A: AstroSat CZTI detection
  6. GRB 251202A / EP251202a: SVOM/VT optical observation
  7. GRB 251201B: Fermi GBM Observation
  8. EP251202a/GRB 251202A: KAIT optical observations
  9. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  10. Fermi GRB 251202B: Global MASTER-Net observations report
  11. GRB 251202B: Fermi GBM Final Real-time Localization
  12. IPN triangulation of GRB 251129B (short/hard)
  13. GRB251129A/EP251129a: Swift UVOT detection
  14. GRB 251129B: AstroSat CZTI detection
  15. GRB 251202A: Fermi GBM Observation
  16. GRB 251202A: Swift/UVOT Detection
  17. GRB 251201B: Kilonova-Catcher optical afterglow detection
  18. GRB 251201B: Swift/UVOT Detection
  19. GRB 251130B: Glowbug gamma-ray detection
  20. GRB 251201B: GECAM-B observation of a long burst
  21. EP251130a: continued NOT optical observations indicate steep fading phase
  22. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  23. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  24. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  25. GRB 251202A: GOTO optical afterglow detection
  26. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  27. GRB 251201A: GECAM-B observation of a burst
  28. GRB 251126A: SAO RAS optical marginal detection
  29. GRB 251202A: Swift-XRT afterglow detection
  30. EP251129a/GRB 251129A: NOWT Detection
  31. GRB 251126A: SVOM/VT optical observation
  32. EP251130a: SVOM/VT optical observation
  33. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  34. Fermi GRB 251202A: Global MASTER-Net observations report
  35. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  36. GRB 251201B: Swift-XRT refined Analysis
  37. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  38. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  39. GRB 251202A: Fermi GBM Final Real-time Localization
  40. GRB 251201A: SVOM/GRM observation of a burst
  41. GRB 251201B: SVOM/VT optical fading
  42. Swift GRB 251201B : MASTER optical counterpart detection
  43. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  44. Swift GRB 251201B: Global MASTER-Net observations report
  45. GRB 251201B: Enhanced Swift-XRT position
  46. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  47. GRB 251130B: AstroSat CZTI detection
  48. GRB 251201B: Swift detection of a burst with an optical counterpart
  49. GRB 251201B: Fermi GBM Final Real-time Localization
  50. EP251130a: Mondy optical observations
  51. EP251130a: Optical detections with Kinder observations
  52. SVOM GRB251201.19: Global MASTER-Net observations report
  53. EP251130a: SAO RAS optical observations
  54. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  55. EP251130a: KAIT optical observations
  56. EP251130A: Optical observation from 1.3m DFOT
  57. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  58. EP251130a: JinShan optical observations
  59. GRB 251201A: MAXI/GSC detection
  60. Fermi GRB 251130B: Global MASTER-Net observations report
  61. GRB 251127A: SVOM/GRM observation
  62. IceCube Alert 251130.75: Global MASTER-Net observations report
  63. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  64. EP251130a: Swift-XRT counterpart detection
  65. GRB 251130B: Fermi GBM Final Localization Correction
  66. EP251130a: Global MASTER-Net observations report
  67. GRB 251130B: Fermi GBM Final Real-time Localization
  68. EP251130a: COLIBRÍ optical counterpart candidate
  69. EP251130a: Einstein Probe detection of an X-ray transient
  70. EP251129a/GRB 251129A: EP-FXT follow-up observations
  71. GRB 251130A: Fermi GBM Final Real-time Localization
  72. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  73. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  74. GRB 251128A: AstroSat CZTI detection
  75. GRB 251129A / EP251129a: SAO RAS optical observations
  76. GRB 251126A: SAO RAS optical observations
  77. GRB 251128A: GECAM-B detection
  78. GRB 251128A: SVOM/GRM observation of a long burst
  79. GRB 251128A: Insight-HXMT/HE detection
  80. SVOM GRB 251129A : MASTER optical counterpart detection
  81. GRB 251129A: Swift-XRT afterglow detection
  82. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  83. Swift trigger 1418333 is not an astrophysical source
  84. GRB 251129A: Swift ToO observations
  85. GRB 251129A / EP251129a: SVOM/VT optical fading
  86. EP251129a: Global MASTER-Net observations report
  87. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  88. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  89. GRB 251129A: Correction to the position of the optical counterpar
  90. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  91. GRB 251128A: Fermi GBM Observation
  92. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  93. GRB 251129A: SVOM detection of a burst
  94. SVOM GRB251129A: Global MASTER-Net observations report
  95. GRB 251129A: SVOM detection of a burst
  96. GRB 251126A: Swift-BAT refined analysis
  97. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  98. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  99. Fermi GRB 251128A: Global MASTER-Net observations report
  100. GRB 251127A: Glowbug gamma-ray detection

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