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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"

19066 results found.

  1. GRB 260208A: continued Mondy optical observations
  2. IPN triangulation of GRB 260212A
  3. IceCube-260217A - IceCube observation of a high-energy neutrino candidate track-like event
  4. EP260214b: Liverpool Telescope optical observations
  5. GRB 260206A: probable hard X-ray burst from 4U 0513-40
  6. EP260214b: Optical upper limit with Kinder observations
  7. EP260214a: Optical upper limits with Kinder observations
  8. EP260214b: EP-FXT follow-up observation
  9. EP260214b: DDOTI Optical Detection
  10. EP260214b: GROWTH-India Telescope optical upper limit
  11. EP260214a: VLT near-infrared observation
  12. EP260214a: NOT optical upper limits
  13. EP260214a: COLIBRÍ optical upper limits
  14. EP260214b: OHP/T120 optical observations
  15. EP260214a: refined analysis of the EP-FXT observation
  16. EP260214b: LCO optical counterpart detection
  17. EP260214b: COLIBRÍ optical observations
  18. EP260214b: NOT optical counterpart detection
  19. EP260214b: Einstein Probe detection of a fast X-ray transient
  20. EP260214a: Einstein Probe detection of an X-ray transient
  21. EP260213a: Liverpool Telescope optical upper limits
  22. EP260213a: COLIBRÍ optical upper limits
  23. EP260213a: Optical upper limits with Kinder observations
  24. EP260213a: Mondy R-band optical upper limit
  25. EP260213a: SVOM/C-GFT upper limit
  26. EP260213a: refined analysis of the EP-FXT observation
  27. EP260213a: Einstein Probe detection of a fast X-ray transient
  28. EP/WXT 01709258378: NOT optical upper limits
  29. GRB 260212A: SVOM/GRM observation of a long burst
  30. GRB 260211A: LAST optical upper limit
  31. GRB 260210A: SVOM/GRM observation
  32. GRB 260211A: LCO optical upper limits
  33. GRB260131A/B: 3.6m DOT Optical Observations
  34. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  35. EP260209a: COLIBRÍ optical upper limit
  36. EP260209a: LCO optical upper limits
  37. EP260210a: refined analysis of the EP-FXT observation
  38. GRB 260208A: LCO detection of the optical counterpart
  39. EP260209a: Einstein Probe detection of a fast X-ray transient
  40. EP260210a: Optical upper limits with Kinder observations
  41. GRB 260208C: AstroSat CZTI detection
  42. EP260210a: COLIBRÍ optical upper limit
  43. EP260210a: SVOM/C-GFT upper limit
  44. EP260210a: Einstein Probe detection of an X-ray transient
  45. GRB 260207B: AstroSat CZTI detection
  46. GRB 260208C: SVOM/GRM observation
  47. GRB 260204A: Swift-XRT afterglow detection
  48. GRB260208A: Liverpool Telescope optical follow-up observations
  49. GRB 260131A/B: continued Mondy optical observations
  50. GRB 260204A: Swift/UVOT Upper Limits
  51. GRB 260208B: COLIBRÍ optical observations
  52. GRB 260208A: Mondy optical observations
  53. GRB 260208A: 1.3m DFOT optical detection
  54. GRB 260208A: COLIBRÍ optical observations
  55. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  56. GRB 260208A: SVOM/VT optical observation
  57. GRB 260208D: Fermi GBM Final Real-time Localization
  58. GRB 260208B: Swift ToO observations
  59. GRB 260208B: SVOM/GRM observation of a bright burst
  60. GRB 260208C: Fermi GBM Final Real-time Localization
  61. GRB 260208A: Swift ToO observations
  62. GRB 260208B: Fermi GBM Final Real-time Localization
  63. GRB 260208A: Fermi GBM Final Real-time Localization
  64. GRB 260131A/B: Mondy and Terskol optical observations
  65. GRB 260206A: Tiled Swift observations
  66. GRB 260204A: Swift-XRT observations
  67. GRB 260204A: SVOM/VT optical candidate
  68. GRB 260204A : MASTER Global robotic net optical observations
  69. GRB 260204A: LCO optical upper limits
  70. EP260110a: Late GTC/EMIR near-infrared observations
  71. GRB 260131A: KAIT optical observations
  72. GRB 251230A: MeerLICHT afterglow detection
  73. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  74. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  75. EP260131a: Liverpool Telescope optical upper limits
  76. EP260131a: COLIBRÍ further observations
  77. EP260131a: SVOM/VT optical observation
  78. EP260131a: Xinglong optical upper limit
  79. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  80. EP260131a: COLIBRÍ observations of slow optical fading
  81. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  82. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  83. EP260131a: COLIBRÍ optical observations of the counterpart
  84. GRB 260127B: AstroSat CZTI detection
  85. EP260131a: Einstein Probe detection of an X-ray transient
  86. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  87. GRB 260128B: LCO optical upper limits
  88. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  89. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  90. GRB 260127B: Swift-XRT observations
  91. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  92. EP260128a: NOT optical counterpart candidate
  93. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  94. EP260128a: Liverpool Telescope optical observations and possible counterpart
  95. EP260128a: LCO optical upper limits
  96. EP260128a: Einstein Probe detection of an X-ray transient
  97. GRB 260127A: COLIBRÍ optical observations
  98. GRB 260127B: Swift ToO observations
  99. EP260126a: Seimei/TriCCS optical upper limit
  100. GRB 260127A : MITSuME Akeno optical afterglow candidate detection

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