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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"

23441 results found.

  1. The EP-WXT trigger 00199258890 (EP260316a): a correction to the trigger time and FXT automatic follow-up
  2. IceCube-260315A: COLIBRÍ optical observations
  3. EP260314a: Xinglong optical upper limit
  4. EP260314a: optical upper limit with Kinder observations
  5. IceCube Alert-260315A/AT2026fpm Automatic MASTER optical blue counterpart candidate
  6. GRB 260310A / AT2026fgk: 1.3m DFOT optical observations
  7. GRB 260310A / AT 2026fgk: iTelescope optical observations
  8. EP260314a: COLIBRÍ optical upper limit
  9. EP260314a: refined analysis of the EP-WXT and EP-FXT observations
  10. EP260314a: SVOM/VT optical candidate
  11. EP260314a: Einstein Probe detection of an X-ray transient
  12. GRB 260310A / AT2026fgk: SAO RAS optical observations
  13. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  14. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations
  15. GRB 260310A / AT2026fgk: further CAHA 1.23m telescope optical observations suggest shallow decay
  16. GRB 260310A/AT 2026fgk: WINTER NIR Detections
  17. GRB 260310A/AT 2026fgk: J-band observations by the SYSU 80 cm infrared telescope
  18. GRB 260310A/AT 2026fgk: DDOTI Optical Detection
  19. GRB 260310A: NOT optical polarimetry
  20. GRB 260312B: AstroSat CZTI detection
  21. GRB 260310A / AT 2026fgk: COLIBRÍ optical observations
  22. GRB 260310A / AT2026fgk: CAHA 1.23m telescope optical observations
  23. GRB 260310A / AT2026fgk : MASTER OT rebrightening during 7h observations
  24. GRB 260312B: Glowbug gamma-ray detection
  25. GRB 260310A: potential optical counterpart
  26. GRB 260312A: Swift detection of a burst
  27. GRB 260131A/B: radio detection with the VLA
  28. EP260302a: MeerKAT radio counterpart
  29. GRB 260308A: SVOM/GRM observation of a short GRB
  30. EP260306a: Mondy optical upper limit
  31. GRB 260208A: radio detection with the VLA
  32. GRB 260307A: Glowbug gamma-ray detection
  33. GRB 260307B: Mephisto optical upper limits
  34. GRB 260307B: possible NOT optical counterpart
  35. GRB 260307B: SVOM/VT upper limit with X band data analysis
  36. GRB260307B: GROWTH-India Telescope optical upper limit
  37. GRB 260307B: SVOM/VT optical candidate
  38. GRB 260307B: SVOM/C-GFT upper limit
  39. GRB 260307B: SVOM detection of a burst
  40. EP260306a: refined analysis of the EP-WXT and EP-FXT observations
  41. GRB 260207A: TESS Detection and Possible VLA Counterpart
  42. EP260302a: SVOM/VT optical observation
  43. EP260306a: SVOM/VT optical observation
  44. EP260306a: COLIBRÍ optical observations of the fading and red counterpart
  45. EP260306a: Einstein Probe detection of an X-ray transient
  46. GRB 260303A: 1.3m DFOT optical upper limit
  47. EP260214b: ATCA 6 GHz observations
  48. GRB 260303B: AstroSat CZTI detection
  49. GRB 260304A: AstroSat CZTI detection of a long burst
  50. GRB 260303A: SVOM/VT optical observations
  51. GRB 260303A: J-band observations with WINTER
  52. GRB 260303B: Fermi GBM Final Real-time Localization
  53. EP260302a: analysis of the follow-up EP-FXT observation
  54. EP260302a: LCO observations
  55. EP260302a: BOOTES-7 optical counterpart detection at early times
  56. GRB 260303A: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  57. GRB 260303A: SVOM detection of a burst
  58. EP260302a: Einstein Probe detection of an X-ray transient
  59. GRB 251130B: TERI Gamma-ray detection
  60. GRB 260208A: TERI Gamma-ray detection
  61. EP260227a: Mondy optical observations
  62. GRB 260228A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  63. EP260227a: Mephisto optical detection
  64. EP-WXT trigger 01709258652: 50cm Telescope multi-band observations
  65. EP260227a: SVOM/VT optical observation
  66. GRB 260228A: SVOM/VT optical upper limits
  67. GRB 260225D: SVOM/GRM observation
  68. EP260227A: 3.6m DOT optical afterglow detection
  69. GRB 260225B: SVOM/GRM observation
  70. EP260227a: Liverpool Telescope optical observations
  71. EP260227a: LCOGT Optical Observations
  72. GRB 260226A: Asiago r-band upper limit
  73. EP260227a: Liverpool Telescope observations
  74. EP260227a: COLIBRÍ optical observations
  75. EP260227a: NOT optical observations
  76. EP260227a: Einstein Probe detection of an X-ray transient and refined analysis
  77. EP/WXT trigger 01709258681 (EP260227a?): LCO candidate afterglow
  78. GRB 260223A: 7DT detection and Medium-band SED of Afterglow
  79. EP260214a: VLT/FORS2 optical observations
  80. GRB 260225A: WINTER J-band upper limit
  81. GRB 260226A: COLIBRÍ optical upper limits
  82. GRB 260226A: LCOGT Optical Upper Limit
  83. EP-WXT trigger 01709258652: SVOM/C-GFT confirmation of a stellar flare
  84. GRB 260225D: Glowbug gamma-ray detection of a likely short burst
  85. GRB 260226A: Glowbug gamma-ray detection
  86. GRB 260226A : GROWTH-India Telescope optical observations
  87. GRB 260226A: LAST optical upper limit
  88. The EP-WXT trigger 01709258652 is likely a flaring star
  89. EP260224a: LCO optical upper limits
  90. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) Detection of an Optical Counterpart Candidate
  91. GRB 260225A: SVOM/VT optical upper limits
  92. EP260223a: Liverpool Telescope upper limits
  93. GRB 260225A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  94. EP260224a: Einstein Probe detection of an X-ray transient
  95. EP 260225.148: COLIBRÍ Confirmation of flaring star
  96. EP260223a: Xinglong optical upper limit
  97. GRB 260223A: Glowbug gamma-ray detection
  98. EP260213a: Mephisto optical upper limits
  99. sb26021801: SVOM/VT optical upper limits
  100. GRB 260223A: COLIBRÍ optical afterglow decay confirmation

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