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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"

8280 results found.

  1. GRB 260307B: SVOM/VT optical candidate
  2. GRB 260307B: SVOM/C-GFT upper limit
  3. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  4. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  5. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  6. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  7. IceCube cascade alert 142200_1517143 retraction
  8. EP260214a: VLT/FORS2 optical observations
  9. EP260214a: VLA 6 GHz detection
  10. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  11. EP260213a: Mephisto optical upper limits
  12. sb26021801: SVOM/C-GFT upper limit
  13. EP260221a: Optical upper limit with Kinder observations
  14. GRB 260223A: DDOTI Optical Candidate
  15. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  16. EP260221a: COLIBRÍ optical counterpart candidate
  17. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  18. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  19. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  20. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  21. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  22. EP260213a: Mondy R-band optical upper limit
  23. EP260213a: SVOM/C-GFT upper limit
  24. GRB 260211A: EP-FXT follow-up observation
  25. Fermi GBM Sub-Threshold Detection of GRB 260211A
  26. EP260210a: SVOM/C-GFT upper limit
  27. GRB 260208B: COLIBRÍ optical observations
  28. GRB 260208B: EP-FXT observation
  29. GRB 260208B: SVOM/VT optical candidate
  30. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  31. GRB 260208B: Swift ToO observations
  32. GRB 260208A: Swift ToO observations
  33. GRB 260206A: Tiled Swift observations
  34. GRB 260204A: Swift-XRT observations
  35. GRB 260204A: SVOM/VT optical candidate
  36. Fermi GBM Sub-Threshold Detection of GRB 260204A
  37. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  38. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  39. EP260131a: COLIBRÍ further observations
  40. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  41. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  42. EP260131a: COLIBRÍ observations of slow optical fading
  43. EP260131a: COLIBRÍ optical observations of the counterpart
  44. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  45. GRB 260127B: Swift-XRT observations
  46. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  47. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  48. EP260128a: NOT optical counterpart candidate
  49. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  50. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  51. GRB 260127A: COLIBRÍ optical observations
  52. GRB 260127B: Swift ToO observations
  53. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  54. GRB 260127B: GOTO candidate optical counterpart
  55. GRB 260127A: Swift detection of a burst
  56. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  57. GRB 260125A: Swift ToO observations
  58. GRB 260125A: GOTO candidate optical counterpart
  59. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  60. GRB 260114A: SVOM/VT optical upper limits
  61. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  62. GRB 260120B: COLIBRÍ optical upper limits
  63. GRB 251202A: further radio observations with the VLA
  64. GRB 260117A: Swift-XRT afterglow detection
  65. EP260119a: COLIBRÍ optical counterpart candidate
  66. GRB 260117A: SVOM/VT optical candidate
  67. GRB 260117A: SVOM/C-GFT upper limit
  68. GRB 260117A: Swift ToO observations
  69. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  70. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  71. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  72. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  73. GRB 251222A: radio detection with the VLA
  74. GRB 260114A: GMG Optical Observation
  75. GRB 260114A: Swift detection of a short burst
  76. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  77. Swift Trigger 1439093: is probably not GRB 260113A
  78. GRB 260111A: COLIBRÍ optical afterglow candidate
  79. GRB 260111A: Swift ToO observations
  80. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  81. Swift trigger 1436759 is not an astrophysical event
  82. EP260110a: SVOM/C-GFT upper limit
  83. EP260110a: BOOTES-5/JGU optical upper limit
  84. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  85. Swift Trigger 1434591: possible GRB 260109C
  86. GRB 260104A: Swift detection of a burst
  87. Fermi GBM Sub-Threshold Detection of GRB 260102A
  88. GRB 260102A: Swift ToO observations
  89. GRB 260101A: Swift detection of a burst with an optical counterpart
  90. GRB 251230A: GRANDMA/TAROT Early Detection
  91. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  92. EP251229a: BOOTES-2 early optical upper limit
  93. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  94. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  95. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  96. GRB 251226A: GECAM-B detection
  97. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  98. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  99. GRB 251222A/EP251222b: Optical detection with Kinder observations
  100. EP251222a: Optical upper limit with Kinder observations

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