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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"

26528 results found.

  1. GRB 260208A: Glowbug gamma-ray detection
  2. GRB 260208A: Fermi GBM Observation
  3. GRB 260208B: Swift-XRT observations
  4. GRB 260131A/B: continued Mondy optical observations
  5. GRB 260204A: Swift/UVOT Upper Limits
  6. GRB 260208B: COLIBRÍ optical observations
  7. GRB 260208A: Mondy optical observations
  8. GRB 260208A: 1.3m DFOT optical detection
  9. GRB 260208A: COLIBRÍ optical observations
  10. GRB 260208B: EP-FXT observation
  11. GRB 260208A: GECAM-B observation of a bright burst
  12. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  13. GRB 260208A: SVOM/VT optical observation
  14. GRB 260208A: Swift-XRT observations
  15. GRB 260208B: SVOM/GRM observation of a bright burst
  16. GRB 260208B: Fermi GBM Detection
  17. GRB 260208B: Fermi-LAT detection
  18. GRB 260207B: GECAM-B observation
  19. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  20. GRB 260131A/B: Mondy and Terskol optical observations
  21. GRB 260206A: Swift-XRT observations
  22. GRB 260204A: Swift-XRT observations
  23. GRB 260204A: SVOM/VT optical candidate
  24. GRB 260204A : MASTER Global robotic net optical observations
  25. GRB 260204A: LCO optical upper limits
  26. EP260110a: Late GTC/EMIR near-infrared observations
  27. GRB 260204A: SVOM detection of a burst
  28. GRB 260131A: KAIT optical observations
  29. GRB 251230A: MeerLICHT afterglow detection
  30. GRB 260130A: GECAM-B observation of a short burst
  31. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  32. GRB 260131A/B: EP/FXT X-ray afterglow detection
  33. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  34. EP260131a: Liverpool Telescope optical upper limits
  35. EP260131a: COLIBRÍ further observations
  36. Konus-Wind detection of GRB 260128A / EP260128a
  37. Konus-Wind detection of GRB 260131A/B
  38. EP260131a: SVOM/VT optical observation
  39. EP260131a: Xinglong optical upper limit
  40. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  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: NOT early detection of the counterpart in "rapid response mode"
  45. EP260131a: COLIBRÍ optical observations of the counterpart
  46. GRB 260130A: Fermi GBM Detection
  47. EP260131a: Einstein Probe detection of an X-ray transient
  48. GRB 260127B: Fermi GBM Detection
  49. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  50. GRB 260128B: LCO optical upper limits
  51. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  52. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  53. GRB 260127B: Swift-XRT observations
  54. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  55. EP260128a: NOT optical counterpart candidate
  56. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  57. EP260128a: Liverpool Telescope optical observations and possible counterpart
  58. EP260128a: LCO optical upper limits
  59. EP260128a: Einstein Probe detection of an X-ray transient
  60. GRB 260127A: Fermi GBM Observation
  61. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  62. GRB 260127A: COLIBRÍ optical observations
  63. EP260126a: Seimei/TriCCS optical upper limit
  64. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  65. GRB 260127A: Swift-XRT refined Analysis
  66. GRB 260127A: SVOM/C-GFT optical observations
  67. The EP-WXT trigger 01709253145 is likely a flaring star
  68. GRB 260127A: Enhanced Swift-XRT position
  69. GRB 260127A: LCO optical afterglow discovery
  70. GRB 260127A: Swift detection of a burst
  71. GRB 260125A: Swift-XRT observations
  72. EP260126a: EP-FXT follow-up observation
  73. EP260126a: Optical upper limit with Kinder observations
  74. EP260126a: Liverpool Telescope optical upper limits
  75. EP260126a: Further NOT optical upper limits
  76. EP260126a: COLIBRÍ optical upper limits
  77. EP260126a: NOT optical observations
  78. EP260126a: Einstein Probe detection of a fast X-ray transient
  79. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  80. Konus-Wind detection of GRB 260120B
  81. GRB 251222A: SVOM/ECLAIRs refined analysis
  82. GRB 260125A: GOTO candidate optical counterpart
  83. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  84. GRB 260114A: SVOM/VT optical upper limits
  85. GRB 260120B: SVOM/GRM observation
  86. EP260119a: Assy AZT-20 optical observations
  87. EP260119a: Mondy and SAO RAS optical upper limits
  88. EP260119a: Xinglong optical upper limit
  89. The EP-WXT trigger 01709251871 is likely a flaring star
  90. GRB 260120B: Swift-XRT refined Analysis
  91. EP260116a: COLIBRÍ further observations
  92. GRB 260120B: Fermi GBM Observation
  93. EP260105a: GTC/HiPERCAM optical observations
  94. GRB 260120B: Swift/UVOT Detection
  95. GRB 260120B: COLIBRÍ optical upper limits
  96. GRB 260120B: Enhanced Swift-XRT position
  97. GRB 260120B: SVOM/C-GFT optical counterpart detection
  98. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  99. GRB 260120B: Swift detection of a burst
  100. EP260119A: Mondy I-Band Observations

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