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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"

19549 results found.

  1. EP260214b: NOT optical counterpart detection
  2. EP260214b: Einstein Probe detection of a fast X-ray transient
  3. EP260214a: Einstein Probe detection of an X-ray transient
  4. EP260213a: Liverpool Telescope optical upper limits
  5. EP260213a: COLIBRÍ optical upper limits
  6. EP260213a: Optical upper limits with Kinder observations
  7. EP260213a: Mondy R-band optical upper limit
  8. EP260213a: SVOM/C-GFT upper limit
  9. EP260213a: refined analysis of the EP-FXT observation
  10. EP260213a: Einstein Probe detection of a fast X-ray transient
  11. EP/WXT 01709258378: NOT optical upper limits
  12. GRB 260212A: SVOM/GRM observation of a long burst
  13. GRB 260211A: LAST optical upper limit
  14. GRB 260210A: SVOM/GRM observation
  15. GRB 260211A: LCO optical upper limits
  16. GRB260131A/B: 3.6m DOT Optical Observations
  17. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  18. EP260209a: COLIBRÍ optical upper limit
  19. EP260209a: LCO optical upper limits
  20. EP260210a: refined analysis of the EP-FXT observation
  21. GRB 260208A: LCO detection of the optical counterpart
  22. EP260209a: Einstein Probe detection of a fast X-ray transient
  23. EP260210a: Optical upper limits with Kinder observations
  24. GRB 260208C: AstroSat CZTI detection
  25. EP260210a: COLIBRÍ optical upper limit
  26. EP260210a: SVOM/C-GFT upper limit
  27. EP260210a: Einstein Probe detection of an X-ray transient
  28. GRB 260207B: AstroSat CZTI detection
  29. GRB 260208C: SVOM/GRM observation
  30. GRB 260204A: Swift-XRT afterglow detection
  31. GRB260208A: Liverpool Telescope optical follow-up observations
  32. GRB 260131A/B: continued Mondy optical observations
  33. GRB 260204A: Swift/UVOT Upper Limits
  34. GRB 260208B: COLIBRÍ optical observations
  35. GRB 260208A: Mondy optical observations
  36. GRB 260208A: 1.3m DFOT optical detection
  37. GRB 260208A: COLIBRÍ optical observations
  38. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  39. GRB 260208A: SVOM/VT optical observation
  40. GRB 260208D: Fermi GBM Final Real-time Localization
  41. GRB 260208B: Swift ToO observations
  42. GRB 260208B: SVOM/GRM observation of a bright burst
  43. GRB 260208C: Fermi GBM Final Real-time Localization
  44. GRB 260208A: Swift ToO observations
  45. GRB 260208B: Fermi GBM Final Real-time Localization
  46. GRB 260208A: Fermi GBM Final Real-time Localization
  47. GRB 260131A/B: Mondy and Terskol optical observations
  48. GRB 260206A: Tiled Swift observations
  49. GRB 260204A: Swift-XRT observations
  50. GRB 260204A: SVOM/VT optical candidate
  51. GRB 260204A : MASTER Global robotic net optical observations
  52. GRB 260204A: LCO optical upper limits
  53. EP260110a: Late GTC/EMIR near-infrared observations
  54. GRB 260131A: KAIT optical observations
  55. GRB 251230A: MeerLICHT afterglow detection
  56. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  57. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  58. EP260131a: Liverpool Telescope optical upper limits
  59. EP260131a: COLIBRÍ further observations
  60. EP260131a: SVOM/VT optical observation
  61. EP260131a: Xinglong optical upper limit
  62. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  63. EP260131a: COLIBRÍ observations of slow optical fading
  64. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  65. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  66. EP260131a: COLIBRÍ optical observations of the counterpart
  67. GRB 260127B: AstroSat CZTI detection
  68. EP260131a: Einstein Probe detection of an X-ray transient
  69. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  70. GRB 260128B: LCO optical upper limits
  71. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  72. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  73. GRB 260127B: Swift-XRT observations
  74. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  75. EP260128a: NOT optical counterpart candidate
  76. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  77. EP260128a: Liverpool Telescope optical observations and possible counterpart
  78. EP260128a: LCO optical upper limits
  79. EP260128a: Einstein Probe detection of an X-ray transient
  80. GRB 260127A: COLIBRÍ optical observations
  81. GRB 260127B: Swift ToO observations
  82. EP260126a: Seimei/TriCCS optical upper limit
  83. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  84. GRB 260127A: SVOM/C-GFT optical observations
  85. GRB 260127A: Enhanced Swift-XRT position
  86. GRB 260127A: LCO optical afterglow discovery
  87. GRB 260127A: Swift detection of a burst
  88. GRB 260125A: Swift-XRT observations
  89. EP260126a: Optical upper limit with Kinder observations
  90. EP260126a: Liverpool Telescope optical upper limits
  91. EP260126a: Further NOT optical upper limits
  92. EP260126a: COLIBRÍ optical upper limits
  93. EP260126a: NOT optical observations
  94. EP260126a: Einstein Probe detection of a fast X-ray transient
  95. GRB 251222A: SVOM/ECLAIRs refined analysis
  96. GRB 260125A: Swift ToO observations
  97. GRB 260125A: GOTO candidate optical counterpart
  98. GRB 260114A: SVOM/VT optical upper limits
  99. GRB 260120B: SVOM/GRM observation
  100. EP260119a: Assy AZT-20 optical observations

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