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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"

17371 results found.

  1. GRB 260211A: LCO optical upper limits
  2. GRB260131A/B: 3.6m DOT Optical Observations
  3. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  4. EP260209a: COLIBRÍ optical upper limit
  5. EP260209a: LCO optical upper limits
  6. EP260210a: refined analysis of the EP-FXT observation
  7. GRB 260208A: LCO detection of the optical counterpart
  8. EP260209a: Einstein Probe detection of a fast X-ray transient
  9. EP260210a: Optical upper limits with Kinder observations
  10. GRB 260210A: AstroSat CZTI detection
  11. EP260210a: COLIBRÍ optical upper limit
  12. EP260210a: SVOM/C-GFT upper limit
  13. GRB 260208B: refined analysis of the EP-FXT observation
  14. EP260210a: Einstein Probe detection of an X-ray transient
  15. GRB 260208C: SVOM/GRM observation
  16. GRB 260204A: Swift-XRT afterglow detection
  17. GRB260208A: Liverpool Telescope optical follow-up observations
  18. GRB 260131A/B: continued Mondy optical observations
  19. GRB 260204A: Swift/UVOT Upper Limits
  20. GRB 260208B: COLIBRÍ optical observations
  21. GRB 260208A: Mondy optical observations
  22. GRB 260208A: 1.3m DFOT optical detection
  23. GRB 260208A: COLIBRÍ optical observations
  24. GRB 260208B: EP-FXT observation
  25. GRB 260208A: NOT spectroscopic redshift z = 2.36
  26. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  27. GRB 260209A: Fermi GBM Final Real-time Localization
  28. GRB 260208A: SVOM/VT optical observation
  29. GRB 260208B: SVOM/GRM observation of a bright burst
  30. LAT GRB 260208B: Global MASTER-Net observations report
  31. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  32. GRB 260131A/B: Mondy and Terskol optical observations
  33. GRB 260204A: SVOM/VT optical candidate
  34. GRB 260204A: LCO optical upper limits
  35. EP260110a: Late GTC/EMIR near-infrared observations
  36. GRB 260131A: KAIT optical observations
  37. GRB 251230A: MeerLICHT afterglow detection
  38. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  39. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  40. EP260131a: Liverpool Telescope optical upper limits
  41. EP260131a: COLIBRÍ further observations
  42. EP260131a: SVOM/VT optical observation
  43. EP260131a: Xinglong optical upper limit
  44. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  45. EP260131a: COLIBRÍ observations of slow optical fading
  46. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  47. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  48. EP260131a: COLIBRÍ optical observations of the counterpart
  49. GRB 260127B: AstroSat CZTI detection
  50. EP260131a: Einstein Probe detection of an X-ray transient
  51. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  52. GRB 260128B: LCO optical upper limits
  53. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  54. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  55. GRB 260127B: Swift-XRT observations
  56. GRB 260127A: INASAN-Kislovodsk, SAO RAS, and Terskol K-800 optical observations
  57. EP260128a: NOT optical counterpart candidate
  58. EP260128a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  59. EP260128a: Liverpool Telescope optical observations and possible counterpart
  60. EP260128a: LCO optical upper limits
  61. EP260128a: Einstein Probe detection of an X-ray transient
  62. GRB 260127A: COLIBRÍ optical observations
  63. EP260126a: Seimei/TriCCS optical upper limit
  64. GRB 260127A : MITSuME Akeno optical afterglow candidate detection
  65. GRB 260127A: Swift-XRT refined Analysis
  66. GRB 260127B: GOTO candidate optical counterpart
  67. GRB 260127A: SVOM/C-GFT optical observations
  68. The EP-WXT trigger 01709253145 is likely a flaring star
  69. GRB 260127A: Enhanced Swift-XRT position
  70. GRB 260127A: LCO optical afterglow discovery
  71. GRB 260127A: Swift detection of a burst
  72. GRB 260125A: Swift-XRT observations
  73. EP260126a: EP-FXT follow-up observation
  74. EP260126a: Optical upper limit with Kinder observations
  75. EP260126a: Liverpool Telescope optical upper limits
  76. EP260126a: Further NOT optical upper limits
  77. EP260126a: COLIBRÍ optical upper limits
  78. EP260126a: NOT optical observations
  79. EP260126a: Einstein Probe detection of a fast X-ray transient
  80. GRB 251222A: SVOM/ECLAIRs refined analysis
  81. GRB 260125A: GOTO candidate optical counterpart
  82. GRB 260114A: SVOM/VT optical upper limits
  83. GRB 260122B: Swift-BAT refined analysis
  84. GRB 260120B: SVOM/GRM observation
  85. GRB 260120B: AstroSat CZTI detection
  86. EP260119a: Assy AZT-20 optical observations
  87. EP260119a: Mondy and SAO RAS optical upper limits
  88. EP260119a: Xinglong optical upper limit
  89. The EP-WXT trigger 01709251871 is likely a flaring star
  90. GRB 260120B: Swift-BAT refined analysis
  91. GRB 260120B: Swift-XRT refined Analysis
  92. EP260116a: COLIBRÍ further observations
  93. EP260105a: GTC/HiPERCAM optical observations
  94. GRB 260120B: Swift/UVOT Detection
  95. GRB 260120B: COLIBRÍ optical upper limits
  96. GRB 260120B: Enhanced Swift-XRT position
  97. GRB 260120B: SVOM/C-GFT optical counterpart detection
  98. EP260116a: COLIBRÍ observations of a tentative optical rebrightening
  99. GRB 260120B: Swift detection of a burst
  100. EP260119A: Mondy I-Band Observations

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