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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"

24359 results found.

  1. Fermi GRB 260208D: Global MASTER-Net observations report
  2. GRB 260208D: Fermi GBM Final Real-time Localization
  3. GRB 260208B: SVOM/GRM observation of a bright burst
  4. GRB 260208B: Fermi GBM Detection
  5. LAT GRB 260208B: Global MASTER-Net observations report
  6. GRB 260208B: Fermi-LAT detection
  7. GRB 260208C: Fermi GBM Final Real-time Localization
  8. GRB 260208A: Fermi-LAT detection
  9. GRB 260207B: GECAM-B observation
  10. GRB 260208A: Fermi GBM Classification Correction
  11. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  12. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  13. GRB 260208B: Fermi GBM Final Real-time Localization
  14. Fermi GRB 260208A: Global MASTER-Net observations report
  15. GRB 260208A: Fermi GBM Final Real-time Localization
  16. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  17. GRB 260207A : MASTER optical counterpart discovery
  18. Fermi GRB 260207B: Global MASTER-Net observations report
  19. GRB 260206A: Swift-XRT observations
  20. GRB 260207B: Fermi GBM Final Real-time Localization
  21. GRB 260207A: Fermi GBM Final Localization
  22. Fermi trigger No 792135758: Global MASTER-Net observations report
  23. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  24. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  25. GRB 260204A: LCO optical afterglow detection
  26. GRB 260204A: SVOM/VT optical candidate
  27. GRB 260204A : MASTER Global robotic net optical observations
  28. Fermi GBM Sub-Threshold Detection of GRB 260204A
  29. GRB 260204A: GOTO optical upper limit
  30. GRB 260204A: LCO optical upper limits
  31. EP260110a: Late GTC/EMIR near-infrared observations
  32. GRB 260204B: Fermi GBM Final Real-time Localization
  33. GRB 260204A: SVOM detection of a burst
  34. Konus-Wind detection of GRB 260121A
  35. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  36. GRB 260130A: GECAM-B observation of a short burst
  37. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  38. Konus-Wind detection of GRB 260128A / EP260128a
  39. Konus-Wind detection of GRB 260131A/B
  40. EP260131a: SVOM/VT optical observation
  41. EP260131a: Xinglong optical upper limit
  42. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  43. GRB 260131A/B: Fermi GBM Observation
  44. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  45. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  46. GRB 260131A: Fermi GBM Final Real-time Localization
  47. GRB 260130A: Fermi GBM Detection
  48. GRB 260127B: Fermi GBM Detection
  49. Fermi GRB 260130A: Global MASTER-Net observations report
  50. GRB 260130A: Fermi GBM Final Real-time Localization
  51. Fermi GRB 260129A: Global MASTER-Net observations report
  52. GRB 260128B: LCO optical upper limits
  53. IPN triangulation of GRB 260121A
  54. GRB 260127A: Swift-BAT refined analysis
  55. GRB 260129B: Fermi GBM Final Localization
  56. GRB 260128B: SVOM detection of a burst through offline search
  57. GRB 260129A: Fermi GBM Final Localization
  58. IPN triangulation of GRB 260127B (short)
  59. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  60. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  61. EP260126a: SVOM/VT optical upperlimit
  62. EP260128a: Global MASTER-Net observations report
  63. Fermi GRB 260127A: Global MASTER-Net observations report
  64. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  65. GRB 260127A: Fermi GBM Observation
  66. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  67. GRB 260127A: NOT optical observations
  68. EP260126a: Seimei/TriCCS optical upper limit
  69. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  70. GRB 260127A: Swift-XRT refined Analysis
  71. GRB 260127B: GOTO candidate optical counterpart
  72. GRB 260127A: SVOM/C-GFT optical observations
  73. The EP-WXT trigger 01709253145 is likely a flaring star
  74. Fermi GRB 260127B: Global MASTER-Net observations report
  75. GRB 260127B: Fermi GBM Final Real-time Localization
  76. Swift GRB 260127A: Global MASTER-Net observations report
  77. GRB 260127A: LCO optical afterglow discovery
  78. GRB 260127A: Fermi GBM Final Real-time Localization
  79. EP260126a: EP-FXT follow-up observation
  80. EP260126a: Optical upper limit with Kinder observations
  81. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  82. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  83. Konus-Wind detection of GRB 260120B
  84. GRB 251222A: SVOM/ECLAIRs refined analysis
  85. GRB 260125A: GOTO candidate optical counterpart
  86. Fermi GRB 260125B: Global MASTER-Net observations report
  87. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  88. GRB 260125B: Fermi GBM Final Real-time Localization
  89. GRB 260125A: Fermi GBM Final Real-time Localization
  90. GRB 260114A: SVOM/VT optical upper limits
  91. GRB 260122B: Swift-BAT refined analysis
  92. GRB 260120B: SVOM/GRM observation
  93. GRB 260122B: Swift detection of a burst
  94. Swift GRB260122.97: Global MASTER-Net observations report
  95. GRB 260122A: Fermi GBM Final Real-time Localization
  96. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  97. EP260119a: Xinglong optical upper limit
  98. The EP-WXT trigger 01709251871 is likely a flaring star
  99. Fermi GRB 260120C: Global MASTER-Net observations report
  100. GRB 260120B: Swift-BAT refined analysis

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