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

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