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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"

17850 results found.

  1. The EP-WXT trigger 01709259045 is likely a flaring star
  2. EP260321a: GOTO detection of blue variable source
  3. EP260321a: VLT imaging and spectroscopy show the variable source to be at z = 0.0343
  4. EP260321a: further Kinder optical observations
  5. GRB 260321A: SVOM/VT optical upper limits
  6. EP260321a: Las Cumbres upper limit
  7. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  8. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  9. EP260321a: refined analysis of the EP-WXT and EP-FXT observations, implying a possible supernova shock breakout candidate
  10. EP260321a: SVOM/VT optical upper limit
  11. GRB 260310A: continued optical observation at Mondy
  12. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  13. EP260321a: Einstein Probe detection of an X-ray transient
  14. GRB 260310A / AT 2026fgk: KAIT optical observations
  15. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  16. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  17. GRB 260318A: SVOM/GRM observation
  18. The EP-WXT trigger 01709258989 is likely a flaring star
  19. GRB 260310A: classification as long GRB based on Eiso, Ep, and T_90
  20. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  21. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  22. GRB 260310A / AT 2026fgk: radio detection with the VLA
  23. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  24. GRB 260310A / AT2026fgk: LCO optical observations
  25. IceCube-260315A/AT2026fpm: EP-FXT follow-up observation
  26. GRB 260316B: SVOM/GRM observation
  27. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  28. EP260316a: COLIBRÍ faint optical counterpart candidate
  29. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  30. EP260316a: Xinglong optical upper limit
  31. EP260316a: optical upper limit with Kinder observations
  32. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  33. IceCube-260315A: COLIBRÍ optical observations
  34. EP260314a: Xinglong optical upper limit
  35. EP260314a: optical upper limit with Kinder observations
  36. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  37. GRB 260310A / AT 2026fgk: iTelescope optical observations
  38. EP260314a: COLIBRÍ optical upper limit
  39. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  40. EP260314a: SVOM/VT optical candidate
  41. EP260314a: Einstein Probe detection of an X-ray transient
  42. GRB 260310A / AT2026fgk: SAO RAS optical observations
  43. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  44. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  45. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  46. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  47. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  48. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  49. GRB 260310A: potential optical counterpart
  50. GRB 260131A/B: radio detection with the VLA
  51. EP260302a: MeerKAT radio counterpart
  52. GRB 260308A: SVOM/GRM observation of a short GRB
  53. EP260306a: Mondy optical upper limit
  54. GRB 260208A: radio detection with the VLA
  55. GRB 260307B: Mephisto optical upper limits
  56. GRB 260307B: possible NOT optical counterpart
  57. GRB 260307B: SVOM/VT upper limit with X band data analysis
  58. GRB260307B: GROWTH-India Telescope optical upper limit
  59. GRB 260307B: SVOM/VT optical candidate
  60. GRB 260307B: SVOM/C-GFT upper limit
  61. GRB 260307B: SVOM detection of a burst
  62. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  63. GRB 260207A: TESS Detection and Possible VLA Counterpart
  64. EP260302a: SVOM/VT optical observation
  65. EP260306a: SVOM/VT optical observation
  66. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  67. EP260306a: Einstein Probe detection of an X-ray transient
  68. GRB 260228A: further EP-FXT observations and X-ray afterglow confirmation
  69. GRB 260303A: 1.3m DFOT optical upper limit
  70. GRB 260304A: AstroSat CZTI detection of a long burst
  71. GRB 260303A: SVOM/VT optical observations
  72. GRB 260303A: J-band observations with WINTER
  73. EP260302a: analysis of the follow-up EP-FXT observation
  74. EP260302a: LCO observations
  75. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  76. GRB 260303A: SVOM detection of a burst
  77. GRB 260228A: EP-FXT follow-up observation
  78. EP260302a: Einstein Probe detection of an X-ray transient
  79. EP260227a: Mondy optical observations
  80. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  81. EP260227a: Mephisto optical detection
  82. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  83. EP260227a: SVOM/VT optical observation
  84. GRB 260228A: SVOM/VT optical upper limits
  85. GRB 260225D: SVOM/GRM observation
  86. EP260227A: 3.6m DOT optical afterglow detection
  87. GRB 260225B: SVOM/GRM observation
  88. EP260227a: Liverpool Telescope optical observations
  89. EP260227a: LCOGT Optical Observations
  90. GRB 260226A: Asiago r-band upper limit
  91. EP260227a: Liverpool Telescope observations
  92. EP260227a: COLIBRÍ optical observations
  93. EP260227a: NOT optical observations
  94. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  95. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  96. Konus-Wind detection of GRB 260226A
  97. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  98. EP260214a: VLT/FORS2 optical observations
  99. GRB 260225A: WINTER J-band upper limit
  100. GRB 260226A: COLIBRÍ optical upper limits

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