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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 260204A: SVOM detection of a burst
  2. GRB 260121A: 239Alferov CubeSat detection
  3. Konus-Wind detection of GRB 260121A
  4. GRB 260131A/B: OHP/T193 optical observations
  5. GRB 260131A: KAIT optical observations
  6. GRB 251230A: MeerLICHT afterglow detection
  7. GRB 260131A: FTW optical and NIR observations
  8. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  9. GRID detection of GRB 260131A/B
  10. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  11. GRB 260130A: Insight-HXMT/HE detection
  12. GRB 260130A: GECAM-B observation of a short burst
  13. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  14. GRB 260131A/B: EP/FXT X-ray afterglow detection
  15. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  16. GRB 260127B: Insight-HXMT/HE detection
  17. GRB 260127B: GECAM-B observation of a short burst
  18. GRB 260127A: GECAM-B observation
  19. GRB 260131A: NOT spectroscopic redshift z = 1.434
  20. EP260131a: Liverpool Telescope optical upper limits
  21. EP260131a: COLIBRÍ further observations
  22. Konus-Wind detection of GRB 260128A / EP260128a
  23. GRB 260131A: Insight-HXMT/HE detection
  24. Konus-Wind detection of GRB 260131A/B
  25. EP260131a: SVOM/VT optical observation
  26. EP260131a: Xinglong optical upper limit
  27. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  28. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  29. GRB 260131A/B: Fermi GBM Observation
  30. EP260131a: COLIBRÍ observations of slow optical fading
  31. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  32. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  33. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  34. GRB 260131B: MAXI/GSC detection
  35. GRB 260131A: Fermi GBM Final Real-time Localization
  36. EP260131a: COLIBRÍ optical observations of the counterpart
  37. EP260131a: Las Cumbres detection of an optical counterpart
  38. GRB 260127B: AstroSat CZTI detection
  39. GRB 260130A: Fermi GBM Detection
  40. EP260131a: Einstein Probe detection of an X-ray transient
  41. GRB 260127B: Fermi GBM Detection
  42. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  43. Fermi GRB 260130A: Global MASTER-Net observations report
  44. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  45. GRB 260130A: Fermi GBM Final Real-time Localization
  46. Fermi GRB 260129A: Global MASTER-Net observations report
  47. GRB 260128B: LCO optical upper limits
  48. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  49. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  50. IPN triangulation of GRB 260121A
  51. GRB 260127A: Swift-BAT refined analysis
  52. GRB 260129B: Fermi GBM Final Localization
  53. GRB 260128B: SVOM detection of a burst through offline search
  54. GRB 260129A: Fermi GBM Final Localization
  55. IPN triangulation of GRB 260127B (short)
  56. GRB 260127B: Swift-XRT observations
  57. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  58. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  59. EP260128a: NOT optical counterpart candidate
  60. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. EP260128a: Liverpool Telescope optical observations and possible counterpart
  62. EP260128a: LCO optical upper limits
  63. EP260126a: SVOM/VT optical upperlimit
  64. EP260128a: Global MASTER-Net observations report
  65. EP260128a: Einstein Probe detection of an X-ray transient
  66. Fermi GRB 260127A: Global MASTER-Net observations report
  67. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  68. GRB 260127A: Fermi GBM Observation
  69. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 260127A: COLIBRÍ optical observations
  71. GRB 260127A: NOT optical observations
  72. GRB 260127B: Swift ToO observations
  73. EP260126a: Seimei/TriCCS optical upper limit
  74. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  75. GRB 260127A: Swift-XRT refined Analysis
  76. GRB 260127B: GOTO candidate optical counterpart
  77. GRB 260127A: SVOM/C-GFT optical observations
  78. The EP-WXT trigger 01709253145 is likely a flaring star
  79. GRB 260127A: Enhanced Swift-XRT position
  80. Fermi GRB 260127B: Global MASTER-Net observations report
  81. GRB 260127B: Fermi GBM Final Real-time Localization
  82. GRB 260127A: Prompt enhanced Swift-XRT position
  83. Swift GRB 260127A: Global MASTER-Net observations report
  84. GRB 260127A: LCO optical afterglow discovery
  85. GRB 260127A: Swift detection of a burst
  86. GRB 260127A: Fermi GBM Final Real-time Localization
  87. GRB 260125A: Swift-XRT observations
  88. EP260126a: EP-FXT follow-up observation
  89. EP260126a: Optical upper limit with Kinder observations
  90. EP260126a: Liverpool Telescope optical upper limits
  91. EP260126a: Further NOT optical upper limits
  92. EP260126a: COLIBRÍ optical upper limits
  93. EP260126a: NOT optical observations
  94. EP260126a: Einstein Probe detection of a fast X-ray transient
  95. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  96. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  97. Konus-Wind detection of GRB 260120B
  98. GRB 251222A: SVOM/ECLAIRs refined analysis
  99. GRB 260125A: Swift ToO observations
  100. GRB 260125A: GOTO candidate optical counterpart

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