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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"

23652 results found.

  1. GRB 260208A: Fermi-LAT detection
  2. GRB 260207B: GECAM-B observation
  3. GRB 260208A: Fermi GBM Classification Correction
  4. GRB 260208A: GOTO detection of a potential optical counterpart (GOTO26aob)
  5. GRB 260208B: BALROG localization (Fermi Trigger 792237169 / GRB 260208412)
  6. GRB 260208B: Fermi GBM Final Real-time Localization
  7. Fermi GRB 260208A: Global MASTER-Net observations report
  8. GRB 260208A: Fermi GBM Final Real-time Localization
  9. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  10. GRB 260207A : MASTER optical counterpart discovery
  11. Fermi GRB 260207B: Global MASTER-Net observations report
  12. GRB 260206A: Swift-XRT observations
  13. GRB 260207B: Fermi GBM Final Real-time Localization
  14. GRB 260207A: Fermi GBM Final Localization
  15. Fermi trigger No 792135758: Global MASTER-Net observations report
  16. GRB 260206A (or XRB from 4U 0513-40): MAXI/GSC detection
  17. GRB 260204A: SVOM/VT confirms fading of the optical afterglow
  18. GRB 260204A: LCO optical afterglow detection
  19. GRB 260204A: SVOM/VT optical candidate
  20. GRB 260204A : MASTER Global robotic net optical observations
  21. Fermi GBM Sub-Threshold Detection of GRB 260204A
  22. GRB 260204A: GOTO optical upper limit
  23. GRB 260204A: LCO optical upper limits
  24. EP260110a: Late GTC/EMIR near-infrared observations
  25. GRB 260204B: Fermi GBM Final Real-time Localization
  26. GRB 260204A: SVOM detection of a burst
  27. Konus-Wind detection of GRB 260121A
  28. GRB 260131A/AT2026bwg: Observations by the Zwicky Transient Facility
  29. GRB 260130A: GECAM-B observation of a short burst
  30. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  31. Konus-Wind detection of GRB 260128A / EP260128a
  32. Konus-Wind detection of GRB 260131A/B
  33. EP260131a: SVOM/VT optical observation
  34. EP260131a: Xinglong optical upper limit
  35. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  36. GRB 260131A/B: Fermi GBM Observation
  37. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  38. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  39. GRB 260131A: Fermi GBM Final Real-time Localization
  40. GRB 260130A: Fermi GBM Detection
  41. GRB 260127B: Fermi GBM Detection
  42. Fermi GRB 260130A: Global MASTER-Net observations report
  43. GRB 260130A: Fermi GBM Final Real-time Localization
  44. Fermi GRB 260129A: Global MASTER-Net observations report
  45. GRB 260128B: LCO optical upper limits
  46. IPN triangulation of GRB 260121A
  47. GRB 260127A: Swift-BAT refined analysis
  48. GRB 260129B: Fermi GBM Final Localization
  49. GRB 260128B: SVOM detection of a burst through offline search
  50. GRB 260129A: Fermi GBM Final Localization
  51. IPN triangulation of GRB 260127B (short)
  52. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  53. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  54. EP260126a: SVOM/VT optical upperlimit
  55. EP260128a: Global MASTER-Net observations report
  56. Fermi GRB 260127A: Global MASTER-Net observations report
  57. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  58. GRB 260127A: Fermi GBM Observation
  59. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  60. GRB 260127A: NOT optical observations
  61. EP260126a: Seimei/TriCCS optical upper limit
  62. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  63. GRB 260127A: Swift-XRT refined Analysis
  64. GRB 260127B: GOTO candidate optical counterpart
  65. GRB 260127A: SVOM/C-GFT optical observations
  66. The EP-WXT trigger 01709253145 is likely a flaring star
  67. Fermi GRB 260127B: Global MASTER-Net observations report
  68. GRB 260127B: Fermi GBM Final Real-time Localization
  69. Swift GRB 260127A: Global MASTER-Net observations report
  70. GRB 260127A: LCO optical afterglow discovery
  71. GRB 260127A: Fermi GBM Final Real-time Localization
  72. EP260126a: EP-FXT follow-up observation
  73. EP260126a: Optical upper limit with Kinder observations
  74. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  75. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  76. Konus-Wind detection of GRB 260120B
  77. GRB 251222A: SVOM/ECLAIRs refined analysis
  78. GRB 260125A: GOTO candidate optical counterpart
  79. Fermi GRB 260125B: Global MASTER-Net observations report
  80. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  81. GRB 260125B: Fermi GBM Final Real-time Localization
  82. GRB 260125A: Fermi GBM Final Real-time Localization
  83. GRB 260114A: SVOM/VT optical upper limits
  84. GRB 260122B: Swift-BAT refined analysis
  85. GRB 260120B: SVOM/GRM observation
  86. GRB 260122B: Swift detection of a burst
  87. Swift GRB260122.97: Global MASTER-Net observations report
  88. GRB 260122A: Fermi GBM Final Real-time Localization
  89. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  90. EP260119a: Xinglong optical upper limit
  91. The EP-WXT trigger 01709251871 is likely a flaring star
  92. Fermi GRB 260120C: Global MASTER-Net observations report
  93. GRB 260120B: Swift-BAT refined analysis
  94. GRB 251122A / EP251122a: VLT/X-shooter host redshift z = 1.765
  95. GRB 260120B: Fermi GBM Observation
  96. EP260105a: GTC/HiPERCAM optical observations
  97. GRB 260120B: COLIBRÍ optical upper limits
  98. SVOM GRB260121.06: Global MASTER-Net observations report
  99. GRB 260120B: SVOM/C-GFT optical counterpart detection
  100. GRB 260120C: Fermi GBM Final Real-time Localization

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