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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"

7388 results found.

  1. GRB 260822A: SVOM/VT optical upper limits
  2. IceCube-260825A - IceCube observation of a high-energy neutrino candidate track-like event
  3. GRB 260822A: the candidate optical afterglow is an unrelated type-Ia SN
  4. GRB 260822A: GOTO optical counterpart detection
  5. GRB 260822A: SVOM/VT optical detection of COLIBRÍ candidate
  6. GRB 260822A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  7. GRB 260822A: LCO optical upper limits
  8. GRB 260818B: SVOM/C-GFT optical upper limit
  9. IceCube-260821A - IceCube observation of a high-energy neutrino candidate track-like event
  10. EP detected a brightening of LMXB 1ES 1735-26.9
  11. EP260806a: WFST optical observations
  12. EP260812a: SVOM/C-GFT optical upper limit
  13. Fermi GBM Sub-Threshold Detection of GRB 260809A
  14. The EP-WXT trigger 01709278015 is likely a flaring star
  15. GRB 260808B: SVOM/VT optical afterglow confirmation
  16. GRB 260808B: SVOM/VT optical candidate from VHF data ( localization correction for GCN 45317 )
  17. GRB 260808B: SVOM/VT optical candidate from VHF data
  18. IceCube-260805A: One candidate from the Zwicky Transient Facility
  19. IceCube-260807A - IceCube observation of a high-energy neutrino candidate track-like event
  20. EP260806a: OSIRIS+/GTC redshift z=0.089
  21. IceCube-260805A - IceCube observation of a high-energy neutrino candidate track-like event
  22. GRB 260708A / SN 2026stf: Spectroscopic host redshift z = 0.055 and confirmation of an associated type Ic-BL supernova
  23. GRB 260802A: SVOM/VT optical upper limits from VHF data
  24. GRB 260727A: EP-FXT further follow-up observations and candidate afterglow
  25. GRB 260618B: SVOM/VT continued optical observations indicated a steeper and redder decay
  26. EP260727a: SAO RAS optical observations
  27. GRB 260727A: AbAO and SAO RAS optical observations
  28. EP260727a: 1.5m OSN optical counterpart detection
  29. EP260727a: OHP/T193 optical observations
  30. GRB 260726A: Liverpool Telescope optical observations
  31. GRB 260726A: J-band upper limit with WINTER
  32. GRB 260726A: SVOM/VT optical candidate
  33. IceCube-260722A: One candidate from the Zwicky Transient Facility (ZTF)
  34. IceCube-260722A - IceCube observation of a high-energy neutrino candidate track-like event
  35. GRB 260618B: EP-FXT follow-up observation upper limit
  36. GRB 260714B: COLIBRÍ optical counterpart candidate
  37. IceCube-260712A: No candidates with the Zwicky Transient Facility (ZTF)
  38. IceCube-260712A: LAST optical follow-up observations of the IceCube neutrino candidate
  39. GRB 260705A: ATCA radio observations
  40. GRB 260619A: SVOM/VT continuous optical observations
  41. GRB 260618B: SVOM/VT optical observations indicate shallow decay and reddening
  42. GRB 260708A: GRANDMA Optical Observations
  43. Fermi-LAT Gamma-ray Observations of IceCube-260708A
  44. IceCube-260712A - IceCube observation of a high-energy neutrino candidate track-like event
  45. EP-WXT trigger 0170924151 : RAPAS optical counterpart candidate detection
  46. GRB 260708A: Kilonova-Catcher optical afterglow detection
  47. IceCube-260708A: One candidate from the Zwicky Transient Facility
  48. IceCube-260708A - IceCube observation of a high-energy neutrino candidate track-like event
  49. EP260707a is not a real source
  50. GRB 260705A: Candidate Optical Counterpart from SOAR and Gemini-South and Possible Association with GRB 260705B
  51. GRB 260704A: SVOM/COLIBRÍ (FM-GFT) possible optical counterpart candidate
  52. IceCube-260704A: No candidates from the Zwicky Transient Facility
  53. The EP-WXT trigger 01709274151 is likely a flaring star
  54. IceCube-260704A - IceCube observation of a high-energy neutrino candidate track-like event
  55. IceCube-260622A - IceCube observation of a high-energy neutrino candidate track-like event
  56. GRB 260619A: SVOM/VT optical counterpart confirmation
  57. GRB 260618B: SVOM/VT optical candidate
  58. GRB 260618B: SVOM/VT optical candidate (duplicate Submission of 45001)
  59. GRB 260619A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  60. EP260618a: COLIBRÍ optical counterpart candidate
  61. GRB 260614B: SVOM/VT optical candidate from VHF data
  62. The EP-WXT trigger 01709269488 is likely a flaring star
  63. GRB 260610B / AT2026owq: GRANDMA optical observations
  64. IceCube-260610A: No candidates from the Zwicky Transient Facility
  65. GRB 260610B: DDOTI optical observations
  66. GRB 260610B: GOTO optical counterpart candidate
  67. IceCube-260610A - IceCube observation of a high-energy neutrino candidate track-like event
  68. EP260610b: Gemini North optical counterpart candidate
  69. GRB 260607A / GOTO26fqf / AT2026ong: COLIBRÍ optical observations
  70. GRB 260607A: TRT optical observations
  71. GRB 260607A: GOTO tentative optical counterpart candidate GOTO26fqf / AT2026ong
  72. GRB 260604C: Correction to GCN 44828
  73. GRB 260604C: LAST detection of optical counterpart candidate
  74. EP260602a: NOT NIR J-band observations
  75. GRB 260603A: SVOM/COLIBRÍ (FM-GFT) photometric redshift z = 3.57
  76. GRB 260603A: SVOM/COLIBRÍ (GFT-FM) optical counterpart candidate
  77. EP260530a: Xinglong optical spectroscopy of EP260530a / AT 2026nwl
  78. EP260602a: SVOM/VT optical candidate
  79. EP260530a/AT 2026nwl: COLIBRÍ optical follow up
  80. EP260530a/AT 2026nwl: COLIBRÍ optical observations
  81. The EP-WXT trigger 01709266272 is likely a flaring star
  82. EP260527a/GRB 260527A: optical upper limit with Kinder observations
  83. GRB 260429B / EP260429a: COLIBRÍ optical counterpart candidate
  84. GRB 260529A: GOTO tentative optical afterglow candidate
  85. GRB 260527A/EP260527a: FTW optical and NIR observations
  86. The EP-WXT trigger 01709266147 is likely a flaring star
  87. EP260518a: Einstein Probe detection of an sub-threshold X-ray transient with counterpart AT 2026ndp
  88. GRB 260516D: GOTO optical counterpart detection
  89. GRB 260516D: SVOM/VT optical bright candidate
  90. EP260514a: NOT optical counterpart confirmation
  91. EP260514a: TRT optical counterpart candidate
  92. EP260514a: SVOM/VT optical candidate
  93. GRB 260515A: SVOM/VT optical candidate from VHF data
  94. GRB 260515A: JinShan optical counterpart candidate
  95. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  96. GRB 260511B: NuSTAR detection of prompt emission
  97. GRB 260511A: NuSTAR detection of prompt emission
  98. GRB 260511B: SVOM/VT optical observation with VHF data
  99. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  100. GRB 260511A: SVOM/VT optical observation with VHF data

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