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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 251202B: Fermi GBM Final Real-time Localization
  2. IPN triangulation of GRB 251129B (short/hard)
  3. GRB251129A/EP251129a: Swift UVOT detection
  4. GRB 251129B: AstroSat CZTI detection
  5. GRB 251202A: Fermi GBM Observation
  6. GRB 251202A: Swift/UVOT Detection
  7. GRB 251201B: Kilonova-Catcher optical afterglow detection
  8. GRB 251201B: Swift/UVOT Detection
  9. GRB 251130B: Glowbug gamma-ray detection
  10. GRB 251201B: GECAM-B observation of a long burst
  11. EP251130a: continued NOT optical observations indicate steep fading phase
  12. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  13. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  14. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  15. GRB 251202A: GOTO optical afterglow detection
  16. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  17. GRB 251201A: GECAM-B observation of a burst
  18. GRB 251126A: SAO RAS optical marginal detection
  19. GRB 251202A: Swift-XRT afterglow detection
  20. EP251129a/GRB 251129A: NOWT Detection
  21. GRB 251126A: SVOM/VT optical observation
  22. EP251130a: SVOM/VT optical observation
  23. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  24. Fermi GRB 251202A: Global MASTER-Net observations report
  25. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  26. GRB 251201B: Swift-XRT refined Analysis
  27. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  28. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  29. GRB 251202A: Fermi GBM Final Real-time Localization
  30. GRB 251201A: SVOM/GRM observation of a burst
  31. GRB 251201B: SVOM/VT optical fading
  32. Swift GRB 251201B : MASTER optical counterpart detection
  33. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  34. Swift GRB 251201B: Global MASTER-Net observations report
  35. GRB 251201B: Enhanced Swift-XRT position
  36. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  37. GRB 251130B: AstroSat CZTI detection
  38. GRB 251201B: Swift detection of a burst with an optical counterpart
  39. GRB 251201B: Fermi GBM Final Real-time Localization
  40. EP251130a: Mondy optical observations
  41. EP251130a: Optical detections with Kinder observations
  42. SVOM GRB251201.19: Global MASTER-Net observations report
  43. EP251130a: SAO RAS optical observations
  44. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  45. EP251130a: KAIT optical observations
  46. EP251130A: Optical observation from 1.3m DFOT
  47. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  48. EP251130a: JinShan optical observations
  49. GRB 251201A: MAXI/GSC detection
  50. Fermi GRB 251130B: Global MASTER-Net observations report
  51. GRB 251127A: SVOM/GRM observation
  52. IceCube Alert 251130.75: Global MASTER-Net observations report
  53. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  54. EP251130a: Swift-XRT counterpart detection
  55. GRB 251130B: Fermi GBM Final Localization Correction
  56. EP251130a: Global MASTER-Net observations report
  57. GRB 251130B: Fermi GBM Final Real-time Localization
  58. EP251130a: COLIBRÍ optical counterpart candidate
  59. EP251130a: Einstein Probe detection of an X-ray transient
  60. EP251129a/GRB 251129A: EP-FXT follow-up observations
  61. GRB 251130A: Fermi GBM Final Real-time Localization
  62. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  63. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  64. GRB 251128A: AstroSat CZTI detection
  65. GRB 251129A / EP251129a: SAO RAS optical observations
  66. GRB 251126A: SAO RAS optical observations
  67. GRB 251128A: GECAM-B detection
  68. GRB 251128A: SVOM/GRM observation of a long burst
  69. GRB 251128A: Insight-HXMT/HE detection
  70. SVOM GRB 251129A : MASTER optical counterpart detection
  71. GRB 251129A: Swift-XRT afterglow detection
  72. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  73. Swift trigger 1418333 is not an astrophysical source
  74. GRB 251129A: Swift ToO observations
  75. GRB 251129A / EP251129a: SVOM/VT optical fading
  76. EP251129a: Global MASTER-Net observations report
  77. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  78. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  79. GRB 251129A: Correction to the position of the optical counterpar
  80. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  81. GRB 251128A: Fermi GBM Observation
  82. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  83. GRB 251129A: SVOM detection of a burst
  84. SVOM GRB251129A: Global MASTER-Net observations report
  85. GRB 251129A: SVOM detection of a burst
  86. GRB 251126A: Swift-BAT refined analysis
  87. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  88. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  89. Fermi GRB 251128A: Global MASTER-Net observations report
  90. GRB 251127A: Glowbug gamma-ray detection
  91. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  92. GRB 251126A: further SAO RAS optical observations
  93. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  94. GRB 251126A NUTTelA-TAO Early Measurements
  95. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  96. GRB251126A: MAO/AZT-22 optical observations
  97. GRB 251128A: Fermi GBM Final Real-time Localization
  98. GRB251126A: Continued optical observation from 1.3m DFOT
  99. GRB 251126A: Swift/UVOT Detection
  100. EP251124a: Pan-STARRS ri-band imaging and photometry

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