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

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