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

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