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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"

20366 results found.

  1. EP260213a: NUTTelA-TAO Early Optical Limits
  2. EP260213a: SVOM/C-GFT upper limit
  3. EP260213a: refined analysis of the EP-FXT observation
  4. EP260213a: Einstein Probe detection of a fast X-ray transient
  5. EP/WXT 01709258378: NOT optical upper limits
  6. GRB 260212A: SVOM/GRM observation of a long burst
  7. GRB 260211A - SVOM/ECLAIRs refined analysis
  8. GRB 260204A: SVOM/ECLAIRs refined analysis
  9. GRB 260211A: LAST optical upper limit
  10. GRB 260210A: SVOM/GRM observation
  11. GRB 260128B: SVOM/ECLAIRs refined analysis
  12. GRID detection of GRB 260207B
  13. GRB 260211A: LCO optical upper limits
  14. GRB260131A/B: 3.6m DOT Optical Observations
  15. GRB 260211A: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  16. GRB 260211A: SVOM detection of a burst
  17. EP260209a: COLIBRÍ optical upper limit
  18. EP260209a: LCO optical upper limits
  19. EP260210a: refined analysis of the EP-FXT observation
  20. GRB 260208A: LCO detection of the optical counterpart
  21. EP260209a: Einstein Probe detection of a fast X-ray transient
  22. EP260210a: Optical upper limits with Kinder observations
  23. GRB 260208C: AstroSat CZTI detection
  24. EP260210a: COLIBRÍ optical upper limit
  25. EP260210a: SVOM/C-GFT upper limit
  26. EP260210a: Einstein Probe detection of an X-ray transient
  27. GRB 260208C: SVOM/GRM observation
  28. GRB 260204A: Swift-XRT afterglow detection
  29. GRB 260208B: AstroSat CZTI detection of a bright long burst
  30. GRB260208A: Liverpool Telescope optical follow-up observations
  31. GRB 260131A/B: continued Mondy optical observations
  32. GRB 260204A: Swift/UVOT Upper Limits
  33. GRB 260208B: COLIBRÍ optical observations
  34. GRB 260208A: Mondy optical observations
  35. GRB 260208A: 1.3m DFOT optical detection
  36. GRB 260208A: COLIBRÍ optical observations
  37. GRB 260208A: NOT spectroscopic redshift z = 2.36
  38. GRB 260208A: Zwicky Transient Facility Follow-Up of a Fermi GRB (Trigger 792220053)
  39. GRB 260208A: SVOM/VT optical observation
  40. Fermi GRB 260208D: Global MASTER-Net observations report
  41. GRB 260208B: SVOM/GRM observation of a bright burst
  42. GRB 260207B: Fermi GBM Detection of a Short Burst with Extended Emission
  43. GRB 260131A/B: Mondy and Terskol optical observations
  44. GRB 260204A: Swift-XRT observations
  45. GRB 260204A: SVOM/VT optical candidate
  46. GRB 260204A: LCO optical upper limits
  47. EP260110a: Late GTC/EMIR near-infrared observations
  48. GRB 260204B: Fermi GBM Final Real-time Localization
  49. Konus-Wind detection of GRB 260121A
  50. GRB 260131A: KAIT optical observations
  51. GRB 251230A: MeerLICHT afterglow detection
  52. GRID detection of GRB 260131A/B
  53. GRB 260131A/B (AT2026bwg): J-band observations by SYSU 80cm infrared telescope
  54. GRB 260131A/B (AT2026bwg): COLIBRÍ further optical observations
  55. GRB 260131A: NOT spectroscopic redshift z = 1.434
  56. EP260131a: Liverpool Telescope optical upper limits
  57. EP260131a: COLIBRÍ further observations
  58. Konus-Wind detection of GRB 260128A / EP260128a
  59. EP260131a: SVOM/VT optical observation
  60. EP260131a: Xinglong optical upper limit
  61. GRB 260131A/B (AT2026bwg): COLIBRÍ optical observations and confirmation of fading
  62. EP260131a: COLIBRÍ observations of slow optical fading
  63. EP260131a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  64. EP260131a: VLT/X-shooter spectroscopic redshift z = 0.937
  65. EP260131a: NOT early detection of the counterpart in "rapid response mode"
  66. EP260131a: COLIBRÍ optical observations of the counterpart
  67. EP260131a: Einstein Probe detection of an X-ray transient
  68. EP260128a / GRB 260128A: COLIBRÍ optical upper limit
  69. GRB 260128B: LCO optical upper limits
  70. GRB 260128B: SVOM/COLIBRÍ (FM-GFT) optical upper limits
  71. EP260128a: J band upper limit by SYSU 80cm infrared telescope
  72. GRB 260128B: SVOM detection of a burst through offline search
  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. IceCube-260125A: Upper limits from a search for additional neutrino events in IceCube
  81. GRB 260127A: COLIBRÍ optical 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. Fermi-LAT Gamma-ray Observations of IceCube-260125A
  96. GRB 251222A: SVOM/ECLAIRs refined analysis
  97. GRB 260125A: GOTO candidate optical counterpart
  98. GRB 260114A: SVOM/VT optical upper limits
  99. GRB 260120B: SVOM/GRM observation
  100. GRB 260120B: AstroSat CZTI detection

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