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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"

17572 results found.

  1. EP260327a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  2. EP260327a: SVOM/VT optical upper limits
  3. EP260327a: WINTER J-band upper limit
  4. EP260327a: COLIBRÍ optical upper limits
  5. EP260327a: Gemini-North optical upper limits
  6. EP260324a: GROWTH-India Telescope optical observation
  7. EP260327a: Einstein Probe detection of an X-ray transient
  8. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  9. The EP-WXT trigger 01709259173 is likely a flaring star
  10. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  11. EP260324a: ZTF discovery of the optical counterpart ZTF26aapviim/AT2026hir
  12. GRB 260310A / AT2026fgk: R- and I-band observations with the PKU 60 cm optical telescope
  13. EP260321a: JinShan near-infrared observations
  14. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  15. EP260321a: J-band observations by the SYSU 80 cm infrared telescope
  16. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  17. The EP-WXT trigger 01709259112 is likely a flaring star
  18. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  19. EP260321a: COLIBRÍ further optical observations and brightening
  20. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  21. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  22. GRB 260321A: EP-FXT follow-up observation
  23. The EP-WXT trigger 01709259045 is likely a flaring star
  24. EP260321a: GOTO detection of blue variable source
  25. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  26. EP260321a: further Kinder optical observations
  27. GRB 260321A: SVOM/VT optical upper limits
  28. EP260321a: Las Cumbres upper limit
  29. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  30. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  31. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  32. EP260321a: SVOM/VT optical upper limit
  33. GRB 260310A: continued optical observation at Mondy
  34. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  35. EP260321a: Einstein Probe detection of an X-ray transient
  36. GRB 260310A / AT 2026fgk: KAIT optical observations
  37. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  38. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  39. GRB 260318A: SVOM/GRM observation
  40. The EP-WXT trigger 01709258989 is likely a flaring star
  41. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  42. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  43. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  44. GRB 260310A / AT 2026fgk: radio detection with the VLA
  45. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  46. GRB 260310A / AT2026fgk: LCO optical observations
  47. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  48. GRB 260316B: SVOM/GRM observation
  49. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  50. EP260316a: COLIBRÍ faint optical counterpart candidate
  51. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  52. EP260316a: Xinglong optical upper limit
  53. EP260316a: optical upper limit with Kinder observations
  54. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  55. IceCube-260315A: COLIBRÍ optical observations
  56. EP260314a: Xinglong optical upper limit
  57. EP260314a: optical upper limit with Kinder observations
  58. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  59. GRB 260310A / AT 2026fgk: iTelescope optical observations
  60. EP260314a: COLIBRÍ optical upper limit
  61. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  62. EP260314a: SVOM/VT optical candidate
  63. EP260314a: Einstein Probe detection of an X-ray transient
  64. GRB 260310A / AT2026fgk: SAO RAS optical observations
  65. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  66. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  67. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  68. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  69. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  70. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  71. GRB 260310A: potential optical counterpart
  72. GRB 260131A/B: radio detection with the VLA
  73. EP260302a: MeerKAT radio counterpart
  74. GRB 260308A: SVOM/GRM observation of a short GRB
  75. EP260306a: Mondy optical upper limit
  76. GRB 260208A: radio detection with the VLA
  77. GRB 260307B: Mephisto optical upper limits
  78. GRB 260307B: possible NOT optical counterpart
  79. GRB 260307B: SVOM/VT upper limit with X band data analysis
  80. GRB260307B: GROWTH-India Telescope optical upper limit
  81. GRB 260307B: SVOM/VT optical candidate
  82. GRB 260307B: SVOM/C-GFT upper limit
  83. GRB 260307B: SVOM detection of a burst
  84. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  85. GRB 260207A: TESS Detection and Possible VLA Counterpart
  86. EP260302a: SVOM/VT optical observation
  87. EP260306a: SVOM/VT optical observation
  88. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  89. EP260306a: Einstein Probe detection of an X-ray transient
  90. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  91. GRB 260303A: 1.3m DFOT optical upper limit
  92. GRB 260304A: AstroSat CZTI detection of a long burst
  93. GRB 260303A: SVOM/VT optical observations
  94. GRB 260303A: J-band observations with WINTER
  95. EP260302a: analysis of the follow-up EP-FXT observation
  96. EP260302a: LCO observations
  97. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  98. GRB 260303A: SVOM detection of a burst
  99. GRB 260228A: EP-FXT follow-up observation
  100. EP260302a: Einstein Probe detection of an X-ray transient

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