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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"

19551 results found.

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

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