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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"

7301 results found.

  1. GRB 260516D: GOTO optical counterpart detection
  2. GRB 260516D: SVOM/VT optical bright candidate
  3. EP260514a: NOT optical counterpart confirmation
  4. EP260514a: TRT optical counterpart candidate
  5. EP260514a: SVOM/VT optical candidate
  6. GRB 260515A: SVOM/VT optical candidate from VHF data
  7. GRB 260515A: JinShan optical counterpart candidate
  8. IceCube-260504A: No Candidate Transients from the Zwicky Transient Facility
  9. GRB 260511B: NuSTAR detection of prompt emission
  10. GRB 260511A: NuSTAR detection of prompt emission
  11. GRB 260511B: SVOM/VT optical observation with VHF data
  12. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  13. GRB 260511A: SVOM/VT optical observation with VHF data
  14. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  15. Fermi GBM Sub-Threshold Detection of GRB 260510B
  16. GRB 260509A: LCO optical observations
  17. GRB 260509A: SVOM/VT optical candidate with VHF data
  18. GRB 260509A: LCO optical counterpart detection
  19. GRB 260509A: GOTO optical counterpart candidate
  20. EP260507a: COLIBRÍ optical observations
  21. EP260507a: Kinder optical counterpart candidate
  22. GRB 260504B: SVOM/MXT refined analysis and potential detection
  23. IceCube-260504A - IceCube observation of a high-energy neutrino candidate track-like event
  24. IceCube-260425A - IceCube observation of a high-energy neutrino candidate track-like event
  25. GRB 260421B: LCO optical afterglow confirmation
  26. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  27. EP260416a: Optical follow-up observations with Kinder
  28. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  29. EP260416a: WFST optical observations and rebrightening
  30. EP260416a: SVOM/VT optical observation
  31. EP260416a: COLIBRÍ optical counterpart candidate
  32. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  33. GOTO26djh/AT2026jpw: EP-FXT X-ray counterpart detection
  34. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  35. GRB 260411B: Fermi-LAT detection
  36. GRB 260411B: GOTO optical counterpart candidate
  37. EP260409a: Gemini/FLAMINGOS2 J-band counterpart
  38. GRB 260330B: SVOM/VT further optical observation
  39. EP260403a: COLIBRÍ optical counterpart candidate
  40. GRB 260330B: SVOM/VT optical candidate
  41. GRB 260330B: EP-FXT follow-up and identification of candidate afterglow
  42. EP260402a/GRB 260402A: SVOM/C-GFT upper limit
  43. GRB 260402A: SVOM/MXT candidate X-ray afterglow
  44. GRB 260310A / AT2026fgk: Luminance-band optical follow-up with a 28cm telescope in Daocheng
  45. EP260329b: GOTO detection of optical counterpart
  46. Fermi GBM Sub-Threshold Detection of GRB 260330B
  47. EP260329a: COLIBRÍ optical upper limit
  48. EP260329a: NOT optical counterpart candidate
  49. EP260329b: Optical follow-up with Kinder observations
  50. EP-WXT trigger 01709259209: TRT optical counterpart detection
  51. EP260327a: COLIBRÍ optical upper limits
  52. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  53. EP260321a: ZTF and Rubin detections of the candidate optical counterpart to EP260321a
  54. EP260321a: further Kinder optical observations
  55. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  56. Fermi GBM Sub-Threshold Detection of GRB 260321A
  57. IceCube-260315A: No Candidate Transients from the Zwicky Transient Facility
  58. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  59. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  60. EP260316a: COLIBRÍ faint optical counterpart candidate
  61. EP260316a: Xinglong optical upper limit
  62. IceCube-260315A: COLIBRÍ optical observations
  63. EP260314a: optical upper limit with Kinder observations
  64. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  65. EP260314a: COLIBRÍ optical upper limit
  66. IceCube-260315A - IceCube observation of a high-energy neutrino candidate track-like event
  67. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  68. EP260314a: SVOM/VT optical candidate
  69. GRB 260310A / AT2026fgk: SAO RAS optical observations
  70. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  71. GRB 260310A/AT 2026fgk: Bok spectroscopic observation
  72. GRB 260310A / AT2026fgk: OSIRIS+/GTC spectroscopy confirms redshift z = 0.153
  73. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  74. GRB260310A / AT2026fgk: P200 Spectroscopy
  75. Fermi GBM Sub-Threshold Detection of GRB 260307B
  76. GRB 260307B: Mephisto optical upper limits
  77. GRB 260307B: possible NOT optical counterpart
  78. GRB 260307B: SVOM/VT upper limit with X band data analysis
  79. GRB 260307B: SVOM/VT optical candidate
  80. GRB 260307B: SVOM/C-GFT upper limit
  81. GRB 260211A: SVOM/VT optical rebrightening at 20 days after the burst, SN candidate
  82. IceCube-260217A: No Candidate Transients from the Zwicky Transient Facility
  83. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  84. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  85. IceCube cascade alert 142200_1517143 retraction
  86. EP260214a: VLT/FORS2 optical observations
  87. EP260214a: VLA 6 GHz detection
  88. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  89. EP260213a: Mephisto optical upper limits
  90. sb26021801: SVOM/C-GFT upper limit
  91. EP260221a: Optical upper limit with Kinder observations
  92. GRB 260223A: DDOTI Optical Candidate
  93. EP260221a: Liverpool Telescope detection of COLIBRÍ counterpart candidate
  94. EP260221a: COLIBRÍ optical counterpart candidate
  95. ZTF26aaglqak/AT2026dbl: COLIBRÍ Optical Observations
  96. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  97. EP260213a: Mondy R-band optical upper limit
  98. EP260213a: SVOM/C-GFT upper limit
  99. GRB 260211A: EP-FXT follow-up observation
  100. EP260210a: SVOM/C-GFT upper limit

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