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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"

8473 results found.

  1. EP260214a: VLT/FORS2 optical observations
  2. EP260214a: VLA 6 GHz detection
  3. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  4. EP260213a: Mephisto optical upper limits
  5. sb26021801: SVOM/C-GFT upper limit
  6. EP260221a: Optical upper limit with Kinder observations
  7. GRB 260223A: DDOTI Optical Candidate
  8. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  9. EP260221a: COLIBRÍ optical counterpart candidate
  10. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  11. IceCube-260217A: Upper limits from a search for additional neutrino events in IceCube
  12. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  13. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  14. EP260214a / GRB 260214A: Fermi-GBM Sub-Threshold Detection
  15. EP260213a: Mondy R-band optical upper limit
  16. EP260213a: SVOM/C-GFT upper limit
  17. GRB 260211A: EP-FXT follow-up observation
  18. Fermi GBM Sub-Threshold Detection of GRB 260211A
  19. EP260210a: SVOM/C-GFT upper limit
  20. GRB 260208B: COLIBRÍ optical observations
  21. GRB 260208B: EP-FXT observation
  22. GRB 260208B: SVOM/VT optical candidate
  23. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  24. GRB 260208B: Swift ToO observations
  25. GRB 260208A: Swift ToO observations
  26. GRB 260206A: Tiled Swift observations
  27. GRB 260204A: Swift-XRT observations
  28. GRB 260204A: SVOM/VT optical candidate
  29. Fermi GBM Sub-Threshold Detection of GRB 260204A
  30. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  31. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  32. EP260131a: COLIBRÍ further observations
  33. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  34. GRB 260131A/B: GOTO candidate optical counterpart consistent with the MAXI localisation
  35. EP260131a: COLIBRÍ observations of slow optical fading
  36. EP260131a: COLIBRÍ optical observations of the counterpart
  37. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  38. GRB 260127B: Swift-XRT observations
  39. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  40. GRB 260128A / EP260128a: Fermi-GBM Sub-Threshold Detection
  41. EP260128a: NOT optical counterpart candidate
  42. IceCube-260125A: No Candidate Transients from the Zwicky Transient Facility
  43. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  44. GRB 260127A: COLIBRÍ optical observations
  45. GRB 260127B: Swift ToO observations
  46. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  47. GRB 260127B: GOTO candidate optical counterpart
  48. GRB 260127A: Swift detection of a burst
  49. GRB 260125A: NOT optical observations on GOTO26acv / AT 2026bjf
  50. GRB 260125A: Swift ToO observations
  51. GRB 260125A: GOTO candidate optical counterpart
  52. IceCube-260125A - IceCube observation of a high-energy neutrino candidate track-like event
  53. GRB 260114A: SVOM/VT optical upper limits
  54. IceCube-260115A: No Candidate Transients from the Zwicky Transient Facility
  55. GRB 260120B: COLIBRÍ optical upper limits
  56. GRB 251202A: further radio observations with the VLA
  57. GRB 260117A: Swift-XRT afterglow detection
  58. EP260119a: COLIBRÍ optical counterpart candidate
  59. GRB 260117A: SVOM/VT optical candidate
  60. GRB 260117A: SVOM/C-GFT upper limit
  61. GRB 260117A: Swift ToO observations
  62. IceCube-260115A: Upper limits from a search for additional neutrino events in IceCube
  63. GRB 260111A: COLIBRÍ fading of the optical counterpart candidate
  64. IceCube-260115A - IceCube observation of a high-energy neutrino candidate track-like event
  65. IceCube: GCN Notices for high-energy track alerts now streamed via Kafka
  66. GRB 251222A: radio detection with the VLA
  67. GRB 260114A: GMG Optical Observation
  68. GRB 260114A: Swift detection of a short burst
  69. IceCube-260111A: Upper limits from a search for additional neutrino events in IceCube
  70. Swift Trigger 1439093: is probably not GRB 260113A
  71. GRB 260111A: COLIBRÍ optical afterglow candidate
  72. GRB 260111A: Swift ToO observations
  73. IceCube-260111A - IceCube observation of a high-energy neutrino candidate track-like event
  74. Swift trigger 1436759 is not an astrophysical event
  75. EP260110a: SVOM/C-GFT upper limit
  76. EP260110a: BOOTES-5/JGU optical upper limit
  77. EP260105b / GRB 260105C : Fermi-GBM Sub-Threshold Detection
  78. Swift Trigger 1434591: possible GRB 260109C
  79. GRB 260104A: Swift detection of a burst
  80. Fermi GBM Sub-Threshold Detection of GRB 260102A
  81. GRB 260102A: Swift ToO observations
  82. GRB 260101A: Swift detection of a burst with an optical counterpart
  83. GRB 251230A: GRANDMA/TAROT Early Detection
  84. GRB 251230A/EP251230a: Optical upper limit with Kinder observations
  85. EP251229a: BOOTES-2 early optical upper limit
  86. LIGO/Virgo/KAGRA S251112cm: Candidates from the NSF-DOE Vera C. Rubin Observatory
  87. GRB 251230A: Swift detection of a burst with a bright optical counterpart
  88. GRB 251129A: redshift correction and SN detection at z = 0.505 with GTC
  89. GRB 251226A: GECAM-B detection
  90. IceCube-251225A: Upper limits from a search for additional neutrino events in IceCube
  91. IceCube-251225A - IceCube observation of a high-energy neutrino candidate track-like event
  92. GRB 251222A/EP251222b: Optical detection with Kinder observations
  93. EP251222a: Optical upper limit with Kinder observations
  94. GRB 251222A: SVOM/COLIBRÍ (FM-GFT) optical observations
  95. IceCube-251218A: No Candidate Transients from the Zwicky Transient Facility
  96. GRB 251222A: Swift ToO observations
  97. GRB 251222A: SVOM/VT optical candidate
  98. EP251220a: PRIME upper limit
  99. GRB 251221A: Swift detection of a burst
  100. IceCube-251218A: Upper limits from a search for additional neutrino events in IceCube

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