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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 251129B: GECAM-B observation of a burst
  2. GRB 251203B: Swift-XRT observations
  3. GRB 251203B: confirmation of a stellar flare by BOOTES-2
  4. GRB 251203B : SVOM trigger sb25120304 is not a GRB
  5. GRB 251203C: LCO optical upper limits
  6. GRB 251203B: LCO optical upper limits
  7. GRB 251203B: SVOM/VT optical observation
  8. GRB 251202A / EP251202a: Liverpool Telescope optical follow-up observations
  9. GRB 251203C: SVOM detection of a burst
  10. SVOM GRB251203.77: Global MASTER-Net observations report
  11. SVOM GRB251203B: Global MASTER-Net observations report
  12. GRB 251203B: SVOM detection of a burst
  13. GRB 251129A / EP251129a: SVOM/VT optical color bluer
  14. GRB 251201B: Insight-HXMT/HE detection
  15. EP251202a / GRB 251202A: Insight-HXMT/HE detection
  16. EP251130a: MAO/AZT-22 optical observations
  17. GRB 251203A: Fermi GBM Final Real-time Localization
  18. EP251202a / GRB251202A: AstroSat CZTI detection
  19. GRB 251202A / EP251202a: SVOM/VT optical observation
  20. GRB 251201B: Fermi GBM Observation
  21. EP251202a/GRB 251202A: KAIT optical observations
  22. EP251130a: ULL-ASTRO-MASTER late detection of the optical afterglow with LCO 1-m telescope at Teide Observatory
  23. Fermi GRB 251202B: Global MASTER-Net observations report
  24. GRB 251202B: Fermi GBM Final Real-time Localization
  25. IPN triangulation of GRB 251129B (short/hard)
  26. GRB251129A/EP251129a: Swift UVOT detection
  27. GRB 251129B: AstroSat CZTI detection
  28. GRB 251202A: Fermi GBM Observation
  29. GRB 251202A: Swift/UVOT Detection
  30. GRB 251201B: Kilonova-Catcher optical afterglow detection
  31. GRB 251201B: Swift/UVOT Detection
  32. GRB 251130B: Glowbug gamma-ray detection
  33. GRB 251201B: GECAM-B observation of a long burst
  34. EP251130a: continued NOT optical observations indicate steep fading phase
  35. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  36. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  37. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  38. GRB 251202A: GOTO optical afterglow detection
  39. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  40. GRB 251201A: GECAM-B observation of a burst
  41. GRB 251126A: SAO RAS optical marginal detection
  42. GRB 251202A: Swift-XRT afterglow detection
  43. EP251129a/GRB 251129A: NOWT Detection
  44. GRB 251126A: SVOM/VT optical observation
  45. EP251130a: SVOM/VT optical observation
  46. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  47. Fermi GRB 251202A: Global MASTER-Net observations report
  48. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  49. GRB 251201B: Swift-XRT refined Analysis
  50. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  51. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  52. GRB 251202A: Fermi GBM Final Real-time Localization
  53. GRB 251201A: SVOM/GRM observation of a burst
  54. GRB 251201B: SVOM/VT optical fading
  55. Swift GRB 251201B : MASTER optical counterpart detection
  56. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  57. Swift GRB 251201B: Global MASTER-Net observations report
  58. GRB 251201B: Enhanced Swift-XRT position
  59. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  60. GRB 251130B: AstroSat CZTI detection
  61. GRB 251201B: Swift detection of a burst with an optical counterpart
  62. GRB 251201B: Fermi GBM Final Real-time Localization
  63. EP251130a: Mondy optical observations
  64. EP251130a: Optical detections with Kinder observations
  65. SVOM GRB251201.19: Global MASTER-Net observations report
  66. EP251130a: SAO RAS optical observations
  67. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  68. EP251130a: KAIT optical observations
  69. EP251130A: Optical observation from 1.3m DFOT
  70. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  71. EP251130a: JinShan optical observations
  72. GRB 251201A: MAXI/GSC detection
  73. Fermi GRB 251130B: Global MASTER-Net observations report
  74. GRB 251127A: SVOM/GRM observation
  75. IceCube Alert 251130.75: Global MASTER-Net observations report
  76. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  77. EP251130a: Swift-XRT counterpart detection
  78. GRB 251130B: Fermi GBM Final Localization Correction
  79. EP251130a: Global MASTER-Net observations report
  80. GRB 251130B: Fermi GBM Final Real-time Localization
  81. EP251130a: COLIBRÍ optical counterpart candidate
  82. EP251130a: Einstein Probe detection of an X-ray transient
  83. EP251129a/GRB 251129A: EP-FXT follow-up observations
  84. GRB 251130A: Fermi GBM Final Real-time Localization
  85. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  86. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  87. GRB 251128A: AstroSat CZTI detection
  88. GRB 251129A / EP251129a: SAO RAS optical observations
  89. GRB 251126A: SAO RAS optical observations
  90. GRB 251128A: GECAM-B detection
  91. GRB 251128A: SVOM/GRM observation of a long burst
  92. GRB 251128A: Insight-HXMT/HE detection
  93. SVOM GRB 251129A : MASTER optical counterpart detection
  94. GRB 251129A: Swift-XRT afterglow detection
  95. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  96. Swift trigger 1418333 is not an astrophysical source
  97. GRB 251129A: Swift ToO observations
  98. GRB 251129A / EP251129a: SVOM/VT optical fading
  99. EP251129a: Global MASTER-Net observations report
  100. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy

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