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

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