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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: Swift/UVOT Detection
  2. GRB 251130B: Glowbug gamma-ray detection
  3. GRB 251201B: GECAM-B observation of a long burst
  4. EP251130a: continued NOT optical observations indicate steep fading phase
  5. GRB 251122A/EP251122a: CrAO ZTSh optical observations
  6. Fermi-LAT Gamma-ray Observations of IceCube-251130A
  7. EP251202a / GRB 251202A: LCO r- and i-band optical detection
  8. GRB 251202A: GOTO optical afterglow detection
  9. EP251202a/GRB 251202A: refined analysis of the EP-WXT observations
  10. GRB 251201A: GECAM-B observation of a burst
  11. GRB 251126A: SAO RAS optical marginal detection
  12. GRB 251202A: Swift-XRT afterglow detection
  13. EP251129a/GRB 251129A: NOWT Detection
  14. GRB 251126A: SVOM/VT optical observation
  15. EP251130a: SVOM/VT optical observation
  16. EP251202a / GRB 251202A: NOT spectroscopic redshift z = 2.785
  17. Fermi GRB 251202A: Global MASTER-Net observations report
  18. EP251202a/GRB 251202A: Einstein Probe detection of an X-ray transient
  19. GRB 251201B: Swift-XRT refined Analysis
  20. IceCube-251130A: Upper limits from a search for additional neutrino events in IceCube
  21. EP251202a/trigger 01709249064: Las Cumbres discovery of the optical counterpart
  22. GRB 251202A: Fermi GBM Final Real-time Localization
  23. GRB 251201A: SVOM/GRM observation of a burst
  24. GRB 251201B: SVOM/VT optical fading
  25. Swift GRB 251201B : MASTER optical counterpart detection
  26. GRB 251201B: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at Sutherland Observatory
  27. Swift GRB 251201B: Global MASTER-Net observations report
  28. GRB 251201B: Enhanced Swift-XRT position
  29. EP251118a: Mondy, CrAO, Assy and SAO RAS/Zeiss-1000 optical observations
  30. GRB 251130B: AstroSat CZTI detection
  31. GRB 251201B: Swift detection of a burst with an optical counterpart
  32. GRB 251201B: Fermi GBM Final Real-time Localization
  33. EP251130a: Mondy optical observations
  34. EP251130a: Optical detections with Kinder observations
  35. SVOM GRB251201.19: Global MASTER-Net observations report
  36. EP251130a: SAO RAS optical observations
  37. EP251130a: GTC OSIRIS+ redshift z = 4.035 and rebrightening
  38. EP251130a: KAIT optical observations
  39. EP251130A: Optical observation from 1.3m DFOT
  40. EP251130a: refined analysis of the EP-WXT and EP-FXT observations
  41. EP251130a: JinShan optical observations
  42. GRB 251201A: MAXI/GSC detection
  43. Fermi GRB 251130B: Global MASTER-Net observations report
  44. GRB 251127A: SVOM/GRM observation
  45. IceCube Alert 251130.75: Global MASTER-Net observations report
  46. IceCube-251130A - IceCube observation of a high-energy neutrino candidate track-like event
  47. EP251130a: Swift-XRT counterpart detection
  48. GRB 251130B: Fermi GBM Final Localization Correction
  49. EP251130a: Global MASTER-Net observations report
  50. GRB 251130B: Fermi GBM Final Real-time Localization
  51. EP251130a: COLIBRÍ optical counterpart candidate
  52. EP251130a: Einstein Probe detection of an X-ray transient
  53. EP251129a/GRB 251129A: EP-FXT follow-up observations
  54. GRB 251130A: Fermi GBM Final Real-time Localization
  55. GRB 251129A / EP251129a: GTC/OSIRIS+ spectroscopic redshift z = 1.460
  56. GRB 251129A / EP251129a: OSN and CAHA optical follow-up
  57. GRB 251128A: AstroSat CZTI detection
  58. GRB 251129A / EP251129a: SAO RAS optical observations
  59. GRB 251126A: SAO RAS optical observations
  60. GRB 251128A: GECAM-B detection
  61. GRB 251128A: SVOM/GRM observation of a long burst
  62. GRB 251128A: Insight-HXMT/HE detection
  63. SVOM GRB 251129A : MASTER optical counterpart detection
  64. GRB 251129A: Swift-XRT afterglow detection
  65. The EP-WXT trigger 01709248941 is triggered by the known source Perseus Cluster
  66. Swift trigger 1418333 is not an astrophysical source
  67. GRB 251129A: Swift ToO observations
  68. GRB 251129A / EP251129a: SVOM/VT optical fading
  69. EP251129a: Global MASTER-Net observations report
  70. GRB 251129A: Optical Observations via Virtual Telescope Project, Italy
  71. EP251129a/GRB 251129A : Einstein Probe detection of an X-ray transient
  72. GRB 251129A: Correction to the position of the optical counterpar
  73. GRB 251129A: SVOM/VT optical counterpart confirmation with VHF data
  74. GRB 251128A: Fermi GBM Observation
  75. GRB 251129A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  76. GRB 251129A: SVOM detection of a burst
  77. SVOM GRB251129A: Global MASTER-Net observations report
  78. GRB 251129A: SVOM detection of a burst
  79. GRB 251126A: Swift-BAT refined analysis
  80. GRB 251126A: TShAO, Mondy, and AbAO optical observations
  81. GRB 251128A: Swift/BAT-GUANO localization skymap of a burst
  82. Fermi GRB 251128A: Global MASTER-Net observations report
  83. GRB 251127A: Glowbug gamma-ray detection
  84. GRB 251126A: OHP/T193 optical observations and tentative spectroscopic redshift
  85. GRB 251126A: further SAO RAS optical observations
  86. GRB 250702B: detection of the compact radio counterpart 139 days after the burst
  87. GRB 251126A NUTTelA-TAO Early Measurements
  88. LIGO/Virgo/KAGRA S251112cm: GECKO/KMTNet tiling observations and transient candidates
  89. GRB251126A: MAO/AZT-22 optical observations
  90. GRB 251128A: Fermi GBM Final Real-time Localization
  91. GRB251126A: Continued optical observation from 1.3m DFOT
  92. GRB 251126A: Swift/UVOT Detection
  93. EP251124a: Pan-STARRS ri-band imaging and photometry
  94. GRB 251126A: Mondy and SAO RAS optical observations
  95. GRB 251126A: Swift-XRT refined Analysis
  96. GRB 251126A : MITSuME Akeno optical afterglow candidate detection
  97. GRB 251126A: NOT optical observations
  98. GRB 251126A: 1.3m DFOT optical afterglow detection
  99. GRB 251126A: ULL-ASTRO-MASTER detection of the optical afterglow with LCO 1-m telescope at McDonald Observatory
  100. GRB 251126A: COLIBRÍ photometric redshift z = 3.5

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