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

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