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

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