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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. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  2. GRB 260511B: AstroSat CZTI detection
  3. GRB 260511B: NuSTAR detection of prompt emission
  4. GRB 260511A: NuSTAR detection of prompt emission
  5. GRB 260511B: SVOM/VT optical observation with VHF data
  6. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  7. GRB 260511A: SVOM/VT optical observation with VHF data
  8. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  9. Fermi GBM Sub-Threshold Detection of GRB 260510B
  10. GRB 260509A: LCO optical observations
  11. GRB 260509A: SVOM/VT optical candidate with VHF data
  12. GRB 260509A: LCO optical counterpart detection
  13. GRB 260509A: GOTO optical counterpart candidate
  14. GRB 260506B: AstroSat CZTI detection
  15. IceCube-260504A: Upper limits from a search for additional neutrino events in IceCube
  16. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  17. EP260507a: COLIBRÍ optical observations
  18. EP260507a: Kinder optical counterpart candidate
  19. GRB 260421B: radio observation with the VLA
  20. GRB 260430B: AstroSat CZTI detection of a long burst
  21. GRB 260504B: SVOM/MXT refined analysis and potential detection
  22. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  23. GRB 260429B / EP260429a: AstroSat CZTI detection
  24. GRB 260424B: AstroSat CZTI detection
  25. IceCube-260425A: Upper limits from a search for additional neutrino events in IceCube
  26. GRB 260428A: AstroSat CZTI detection
  27. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  28. GRB 260424A: AstroSat CZTI detection of a long burst
  29. IceCube-Cascade 260418A: Upper limits from a search for additional neutrino events in IceCube
  30. GRB 260421B: BOOTES-7 early optical afterglow detection
  31. GRB 260421B: LCO optical afterglow confirmation
  32. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  33. EP260416a: Optical follow-up observations with Kinder
  34. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  35. EP260416a: WFST optical observations and rebrightening
  36. EP260416a: SVOM/VT optical observation
  37. EP260416a: COLIBRÍ optical counterpart candidate
  38. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  39. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  40. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  41. GRB 260411B: Fermi-LAT detection
  42. GRB 260411B: GOTO optical counterpart candidate
  43. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  44. GRB 260330B: SVOM/VT further optical observation
  45. EP260403a: COLIBRÍ optical counterpart candidate
  46. GRB 260330B: SVOM/VT optical candidate
  47. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  48. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  49. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  50. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  51. EP260329b: GOTO detection of optical counterpart
  52. Fermi GBM Sub-Threshold Detection of GRB 260330B
  53. EP260329a: COLIBRÍ optical upper limit
  54. EP260329a: NOT optical counterpart candidate
  55. EP260329b: Optical follow-up with Kinder observations
  56. EP-WXT trigger 01709259209: TRT optical counterpart detection
  57. EP260327a: COLIBRÍ optical upper limits
  58. EP260321a: Upper limits from a neutrino search with IceCube
  59. GRB260310A: Palomar 60-inch photometry of an extremely bright late-time afterglow with a temporal break at 8 days
  60. EP260321a / AT2026gzf: VLT/X-shooter detection of supernova-like spectral features at z = 0.0344
  61. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  62. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  63. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  64. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  65. EP260321a: further Kinder optical observations
  66. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  67. Fermi GBM Sub-Threshold Detection of GRB 260321A
  68. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  69. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  70. GRB 260310A / AT 2026fgk: radio detection with the VLA
  71. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  72. EP260316a: COLIBRÍ faint optical counterpart candidate
  73. IceCube-260315A: Upper limits from a search for additional neutrino events in IceCube
  74. EP260316a: Xinglong optical upper limit
  75. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  76. IceCube-260315A: COLIBRÍ optical observations
  77. EP260314a: optical upper limit with Kinder observations
  78. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  79. EP260314a: COLIBRÍ optical upper limit
  80. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  81. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  82. EP260314a: SVOM/VT optical candidate
  83. GRB 260310A / AT2026fgk: SAO RAS optical observations
  84. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  85. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  86. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  87. GRB260310A / AT2026fgk: P200 Spectroscopy
  88. GRB 260131A/B: radio detection with the VLA
  89. GRB 260208A: radio detection with the VLA
  90. Fermi GBM Sub-Threshold Detection of GRB 260307B
  91. GRB 260307B: Mephisto optical upper limits
  92. GRB 260307B: possible NOT optical counterpart
  93. GRB 260307B: SVOM/VT upper limit with X band data analysis
  94. GRB 260307B: SVOM/VT optical candidate
  95. GRB 260307B: SVOM/C-GFT upper limit
  96. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  97. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  98. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  99. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  100. IceCube cascade alert 142200_1517143 retraction

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