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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"

26912 results found.

  1. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  2. GRB 260208B: Fermi GBM Final Real-time Localization
  3. Fermi GRB 260208A: Global MASTER-Net observations report
  4. Fermi Gamma-ray Burst Monitor trigger 792220053/260208214 is not a GRB
  5. GRB 260208A: Fermi GBM Final Real-time Localization
  6. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  7. GRB 260207A : MASTER optical counterpart discovery
  8. Fermi GRB 260207B: Global MASTER-Net observations report
  9. GRB 260207B: Fermi GBM Final Real-time Localization
  10. GRB 260207A: Fermi GBM Final Localization
  11. Fermi trigger No 792135758: Global MASTER-Net observations report
  12. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  13. GRB 260204A: Swift-XRT observations
  14. GRB 260204A: LCO optical afterglow detection
  15. GRB 260204A: SVOM/VT optical candidate
  16. GRB 260204A : MASTER Global robotic net optical observations
  17. Fermi GBM Sub-Threshold Detection of GRB 260204A
  18. GRB 260204A: GOTO optical upper limit
  19. GRB 260204A: LCO optical upper limits
  20. EP260110a: Late GTC/EMIR near-infrared observations
  21. GRB 260204B: Fermi GBM Final Real-time Localization
  22. GRB 260204A: SVOM detection of a burst
  23. GRB 251230A: MeerLICHT afterglow detection
  24. GRB 260131A: FTW optical and NIR observations
  25. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  26. GRID detection of GRB 260131A/B
  27. GRB 260131A/B: GTC/OSIRIS+ redshift confimation
  28. GRB 260130A: GECAM-B observation of a short burst
  29. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  30. GRB 260131A/B: EP/FXT X-ray afterglow detection
  31. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  32. GRB 260127B: GECAM-B observation of a short burst
  33. GRB 260127A: GECAM-B observation
  34. GRB 260131A: NOT spectroscopic redshift z = 1.434
  35. EP260131a: Liverpool Telescope optical upper limits
  36. EP260131a: COLIBRÍ further observations
  37. EP260131a: SVOM/VT optical observation
  38. EP260131a: Xinglong optical upper limit
  39. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  40. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  41. GRB 260131A/B: Fermi GBM Observation
  42. EP260131a: COLIBRÍ observations of slow optical fading
  43. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  44. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  45. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  46. GRB 260131A: Fermi GBM Final Real-time Localization
  47. EP260131a: COLIBRÍ optical observations of the counterpart
  48. EP260131a: Las Cumbres detection of an optical counterpart
  49. GRB 260130A: Fermi GBM Detection
  50. EP260131a: Einstein Probe detection of an X-ray transient
  51. GRB 260127B: Fermi GBM Detection
  52. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  53. Fermi GRB 260130A: Global MASTER-Net observations report
  54. EP260128a / GRB 260128A: NOT and TNG optical and NIR upper limits
  55. GRB 260130A: Fermi GBM Final Real-time Localization
  56. Fermi GRB 260129A: Global MASTER-Net observations report
  57. GRB 260128B: LCO optical upper limits
  58. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  59. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  60. GRB 260127A: Swift-BAT refined analysis
  61. GRB 260129B: Fermi GBM Final Localization
  62. GRB 260128B: SVOM detection of a burst through offline search
  63. GRB 260129A: Fermi GBM Final Localization
  64. IPN triangulation of GRB 260127B (short)
  65. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  66. EP260128a: NOT optical counterpart candidate
  67. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  68. EP260128a: LCO optical upper limits
  69. EP260126a: SVOM/VT optical upperlimit
  70. EP260128a: Global MASTER-Net observations report
  71. EP260128a: Einstein Probe detection of an X-ray transient
  72. Fermi GRB 260127A: Global MASTER-Net observations report
  73. GRB 260127A: Fermi GBM Observation
  74. GRB 260127A: COLIBRÍ optical observations
  75. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  76. GRB 260127A: Swift-XRT refined Analysis
  77. GRB 260127B: GOTO candidate optical counterpart
  78. GRB 260127A: SVOM/C-GFT optical observations
  79. The EP-WXT trigger 01709253145 is likely a flaring star
  80. Fermi GRB 260127B: Global MASTER-Net observations report
  81. GRB 260127B: Fermi GBM Final Real-time Localization
  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. EP260126a: EP-FXT follow-up observation
  87. EP260126a: Optical upper limit with Kinder observations
  88. EP260126a: Further NOT optical upper limits
  89. EP260126a: COLIBRÍ optical upper limits
  90. EP260126a: NOT optical observations
  91. EP260126a: Einstein Probe detection of a fast X-ray transient
  92. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  93. Konus-Wind detection of GRB 260120B
  94. GRB 251222A: SVOM/ECLAIRs refined analysis
  95. GRB 260125A: GOTO candidate optical counterpart
  96. Fermi GRB 260125B: Global MASTER-Net observations report
  97. GRB 260125B: Fermi GBM Final Real-time Localization
  98. GRB 260125A: Fermi GBM Final Real-time Localization
  99. GRB 260114A: SVOM/VT optical upper limits
  100. GRB 260122B: Swift-BAT refined analysis

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