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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"

24171 results found.

  1. GRB 260208C: SVOM/GRM observation
  2. GRB260208A: Liverpool Telescope optical follow-up observations
  3. GRB 260208A: NuSTAR detection of prompt emission
  4. GRB 260208A: Fermi GBM Observation
  5. Fermi GRB 260209A: Global MASTER-Net observations report
  6. GRB 260208A: 1.3m DFOT optical detection
  7. Fermi GRB 260208C: Global MASTER-Net observations report
  8. GRB 260208B: SVOM/VT optical candidate
  9. GRB 260208A: GECAM-B observation of a bright burst
  10. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  11. GRB 260209A: Fermi GBM Final Real-time Localization
  12. GRB 260208A: SVOM/VT optical observation
  13. Fermi GRB 260208D: Global MASTER-Net observations report
  14. GRB 260208D: Fermi GBM Final Real-time Localization
  15. GRB 260208B: SVOM/GRM observation of a bright burst
  16. GRB 260208B: Fermi GBM Detection
  17. LAT GRB 260208B: Global MASTER-Net observations report
  18. GRB 260208B: Fermi-LAT detection
  19. GRB 260208C: Fermi GBM Final Real-time Localization
  20. GRB 260208A: Fermi-LAT detection
  21. GRB 260207B: GECAM-B observation
  22. GRB 260208A: Fermi GBM Classification Correction
  23. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  24. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  25. GRB 260208B: Fermi GBM Final Real-time Localization
  26. Fermi GRB 260208A: Global MASTER-Net observations report
  27. GRB 260208A: Fermi GBM Final Real-time Localization
  28. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  29. GRB 260207A : MASTER optical counterpart discovery
  30. Fermi GRB 260207B: Global MASTER-Net observations report
  31. GRB 260206A: Swift-XRT observations
  32. GRB 260207B: Fermi GBM Final Real-time Localization
  33. GRB 260207A: Fermi GBM Final Localization
  34. Fermi trigger No 792135758: Global MASTER-Net observations report
  35. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  36. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  37. GRB 260204A: LCO optical afterglow detection
  38. GRB 260204A: SVOM/VT optical candidate
  39. GRB 260204A : MASTER Global robotic net optical observations
  40. Fermi GBM Sub-Threshold Detection of GRB 260204A
  41. GRB 260204A: GOTO optical upper limit
  42. GRB 260204A: LCO optical upper limits
  43. EP260110a: Late GTC/EMIR near-infrared observations
  44. GRB 260204B: Fermi GBM Final Real-time Localization
  45. GRB 260204A: SVOM detection of a burst
  46. Konus-Wind detection of GRB 260121A
  47. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  48. GRB 260130A: GECAM-B observation of a short burst
  49. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  50. Konus-Wind detection of GRB 260128A / EP260128a
  51. Konus-Wind detection of GRB 260131A/B
  52. EP260131a: SVOM/VT optical observation
  53. EP260131a: Xinglong optical upper limit
  54. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  55. GRB 260131A/B: Fermi GBM Observation
  56. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  57. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  58. GRB 260131A: Fermi GBM Final Real-time Localization
  59. GRB 260130A: Fermi GBM Detection
  60. GRB 260127B: Fermi GBM Detection
  61. Fermi GRB 260130A: Global MASTER-Net observations report
  62. GRB 260130A: Fermi GBM Final Real-time Localization
  63. Fermi GRB 260129A: Global MASTER-Net observations report
  64. GRB 260128B: LCO optical upper limits
  65. IPN triangulation of GRB 260121A
  66. GRB 260127A: Swift-BAT refined analysis
  67. GRB 260129B: Fermi GBM Final Localization
  68. GRB 260128B: SVOM detection of a burst through offline search
  69. GRB 260129A: Fermi GBM Final Localization
  70. IPN triangulation of GRB 260127B (short)
  71. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  72. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  73. EP260126a: SVOM/VT optical upperlimit
  74. EP260128a: Global MASTER-Net observations report
  75. Fermi GRB 260127A: Global MASTER-Net observations report
  76. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  77. GRB 260127A: Fermi GBM Observation
  78. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  79. GRB 260127A: NOT optical observations
  80. EP260126a: Seimei/TriCCS optical upper limit
  81. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  82. GRB 260127A: Swift-XRT refined Analysis
  83. GRB 260127B: GOTO candidate optical counterpart
  84. GRB 260127A: SVOM/C-GFT optical observations
  85. The EP-WXT trigger 01709253145 is likely a flaring star
  86. Fermi GRB 260127B: Global MASTER-Net observations report
  87. GRB 260127B: Fermi GBM Final Real-time Localization
  88. Swift GRB 260127A: Global MASTER-Net observations report
  89. GRB 260127A: LCO optical afterglow discovery
  90. GRB 260127A: Fermi GBM Final Real-time Localization
  91. EP260126a: EP-FXT follow-up observation
  92. EP260126a: Optical upper limit with Kinder observations
  93. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  94. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  95. Konus-Wind detection of GRB 260120B
  96. GRB 251222A: SVOM/ECLAIRs refined analysis
  97. GRB 260125A: GOTO candidate optical counterpart
  98. Fermi GRB 260125B: Global MASTER-Net observations report
  99. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  100. GRB 260125B: Fermi GBM Final Real-time Localization

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