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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"

22856 results found.

  1. GRB 260310A: no evidence of re-brightening up to 9.6 days in optical observation at Mondy
  2. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  3. GRB 260318A: SVOM/GRM observation
  4. GRB260310A/AT2026fgk: Further optical observation from 1.3m DFOT
  5. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  6. GRB 260310A / AT 2026fgk: radio detection with the VLA
  7. GRB 260310A / AT2026fgk: SVOM/VT optical observations
  8. GRB 260310A / AT2026fgk: LCO optical observations
  9. GRB 260316B: SVOM/GRM observation
  10. EP260316a / GRB 260316A: SVOM/VT optical upper limits
  11. EP260316a: COLIBRÍ faint optical counterpart candidate
  12. EP260316a: refined analysis of the EP-WXT and EP-FXT observations
  13. EP260316a: Xinglong optical upper limit
  14. EP260316a: optical upper limit with Kinder observations
  15. GRB 260314A: Glowbug gamma-ray detection
  16. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  17. IceCube-260315A: COLIBRÍ optical observations
  18. EP260314a: Xinglong optical upper limit
  19. EP260314a: optical upper limit with Kinder observations
  20. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  21. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  22. GRB 260310A / AT 2026fgk: iTelescope optical observations
  23. EP260314a: COLIBRÍ optical upper limit
  24. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  25. EP260314a: SVOM/VT optical candidate
  26. EP260314a: Einstein Probe detection of an X-ray transient
  27. GRB 260310A / AT2026fgk: SAO RAS optical observations
  28. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  29. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  30. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  31. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  32. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  33. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  34. GRB 260310A: NOT optical polarimetry
  35. GRB 260312B: AstroSat CZTI detection
  36. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  37. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  38. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  39. GRB 260312B: Glowbug gamma-ray detection
  40. GRB 260310A: potential optical counterpart
  41. GRB 260312A: Swift detection of a burst
  42. GRB 260131A/B: radio detection with the VLA
  43. EP260302a: MeerKAT radio counterpart
  44. GRB 260308A: SVOM/GRM observation of a short GRB
  45. EP260306a: Mondy optical upper limit
  46. GRB 260208A: radio detection with the VLA
  47. GRB 260307A: Glowbug gamma-ray detection
  48. GRB 260307B: Mephisto optical upper limits
  49. GRB 260307B: possible NOT optical counterpart
  50. GRB 260307B: SVOM/VT upper limit with X band data analysis
  51. GRB260307B: GROWTH-India Telescope optical upper limit
  52. GRB 260307B: SVOM/VT optical candidate
  53. GRB 260307B: SVOM/C-GFT upper limit
  54. GRB 260307B: SVOM detection of a burst
  55. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  56. GRB 260207A: TESS Detection and Possible VLA Counterpart
  57. EP260302a: SVOM/VT optical observation
  58. EP260306a: SVOM/VT optical observation
  59. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  60. EP260306a: Einstein Probe detection of an X-ray transient
  61. GRB 260303A: 1.3m DFOT optical upper limit
  62. EP260214b: ATCA 6 GHz observations
  63. GRB 260303B: AstroSat CZTI detection
  64. GRB 260304A: AstroSat CZTI detection of a long burst
  65. GRB 260303A: SVOM/VT optical observations
  66. GRB 260303A: J-band observations with WINTER
  67. GRB 260303B: Fermi GBM Final Real-time Localization
  68. EP260302a: analysis of the follow-up EP-FXT observation
  69. EP260302a: LCO observations
  70. EP260302a: BOOTES-7 optical counterpart detection at early times
  71. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  72. GRB 260303A: SVOM detection of a burst
  73. EP260302a: Einstein Probe detection of an X-ray transient
  74. GRB 251130B: TERI Gamma-ray detection
  75. GRB 260208A: TERI Gamma-ray detection
  76. EP260227a: Mondy optical observations
  77. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  78. EP260227a: Mephisto optical detection
  79. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  80. EP260227a: SVOM/VT optical observation
  81. GRB 260228A: SVOM/VT optical upper limits
  82. GRB 260225D: SVOM/GRM observation
  83. EP260227A: 3.6m DOT optical afterglow detection
  84. GRB 260225B: SVOM/GRM observation
  85. EP260227a: Liverpool Telescope optical observations
  86. EP260227a: LCOGT Optical Observations
  87. GRB 260226A: Asiago r-band upper limit
  88. EP260227a: Liverpool Telescope observations
  89. EP260227a: COLIBRÍ optical observations
  90. EP260227a: NOT optical observations
  91. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  92. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  93. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  94. EP260214a: VLT/FORS2 optical observations
  95. GRB 260225A: WINTER J-band upper limit
  96. GRB 260226A: COLIBRÍ optical upper limits
  97. GRB 260226A: LCOGT Optical Upper Limit
  98. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  99. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  100. GRB 260226A: Glowbug gamma-ray detection

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