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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"

7396 results found.

  1. GRB 260818B: Further EP-FXT observation
  2. GRB 260818B: VLT optical and nIR observations
  3. GRB 260818B: TNG NIR observations
  4. IceCube-260827A - IceCube observation of a high-energy neutrino candidate track-like event
  5. GRB 260818B: 6 GHz VLA observations
  6. GRB 260818B: SVOM/VT optical upper limit and continuous observations
  7. GRB 260818B: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  8. IceCube-260825A: No transient candidates from the Zwicky Transient Facility
  9. GRB 260822A: SVOM/VT optical upper limits
  10. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  11. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  12. GRB 260822A: GOTO optical counterpart detection
  13. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  14. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  15. GRB 260822A: LCO optical upper limits
  16. GRB 260818B: SVOM/C-GFT optical upper limit
  17. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  18. EP detected a brightening of LMXB 1ES 1735-26.9
  19. EP260806a: WFST optical observations
  20. EP260812a: SVOM/C-GFT optical upper limit
  21. Fermi GBM Sub-Threshold Detection of GRB 260809A
  22. The EP-WXT trigger 01709278015 is likely a flaring star
  23. GRB 260808B: SVOM/VT optical afterglow confirmation
  24. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  25. GRB 260808B: SVOM/VT optical candidate from VHF data
  26. IceCube-260805A: One candidate from the Zwicky Transient Facility
  27. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  28. EP260806a: OSIRIS+/GTC redshift z=0.089
  29. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  30. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  31. GRB 260802A: SVOM/VT optical upper limits from VHF data
  32. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  33. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  34. EP260727a: SAO RAS optical observations
  35. GRB 260727A: AbAO and SAO RAS optical observations
  36. EP260727a: 1.5m OSN optical counterpart detection
  37. EP260727a: OHP/T193 optical observations
  38. GRB 260726A: Liverpool Telescope optical observations
  39. GRB 260726A: J-band upper limit with WINTER
  40. GRB 260726A: SVOM/VT optical candidate
  41. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  42. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  43. GRB 260618B: EP-FXT follow-up observation upper limit
  44. GRB 260714B: COLIBRÍ optical counterpart candidate
  45. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  46. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  47. GRB 260705A: ATCA radio observations
  48. GRB 260619A: SVOM/VT continuous optical observations
  49. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  50. GRB 260708A: GRANDMA Optical Observations
  51. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  52. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  53. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  54. GRB 260708A: Kilonova-Catcher optical afterglow detection
  55. IceCube-260708A: One candidate from the Zwicky Transient Facility
  56. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  57. EP260707a is not a real source
  58. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  59. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  60. IceCube-260704A: No candidates from the Zwicky Transient Facility
  61. The EP-WXT trigger 01709274151 is likely a flaring star
  62. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  63. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  64. GRB 260619A: SVOM/VT optical counterpart confirmation
  65. GRB 260618B: SVOM/VT optical candidate
  66. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  67. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  68. EP260618a: COLIBRÍ optical counterpart candidate
  69. GRB 260614B: SVOM/VT optical candidate from VHF data
  70. The EP-WXT trigger 01709269488 is likely a flaring star
  71. GRB 260610B / AT2026owq: GRANDMA optical observations
  72. IceCube-260610A: No candidates from the Zwicky Transient Facility
  73. GRB 260610B: DDOTI optical observations
  74. GRB 260610B: GOTO optical counterpart candidate
  75. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  76. EP260610b: Gemini North optical counterpart candidate
  77. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  78. GRB 260607A: TRT optical observations
  79. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  80. GRB 260604C: Correction to GCN 44828
  81. GRB 260604C: LAST detection of optical counterpart candidate
  82. EP260602a: NOT NIR J-band observations
  83. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  84. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  85. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  86. EP260602a: SVOM/VT optical candidate
  87. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  88. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  89. The EP-WXT trigger 01709266272 is likely a flaring star
  90. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  91. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  92. GRB 260529A: GOTO tentative optical afterglow candidate
  93. GRB 260527A/EP260527a: FTW optical and NIR observations
  94. The EP-WXT trigger 01709266147 is likely a flaring star
  95. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  96. GRB 260516D: GOTO optical counterpart detection
  97. GRB 260516D: SVOM/VT optical bright candidate
  98. EP260514a: NOT optical counterpart confirmation
  99. EP260514a: TRT optical counterpart candidate
  100. EP260514a: SVOM/VT optical candidate

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