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

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