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

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