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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"

23572 results found.

  1. GRB 260511A: REM near-infrared detection
  2. GRB 260511B: AstroSat CZTI detection
  3. GRB 260506B: Glowbug gamma-ray detection
  4. GRB 260506A: Glowbug gamma-ray detection of a short burst
  5. GRB 260511B: TRT optical observation
  6. GRB 260511B : MITSuME Akeno optical afterglow candidate detection
  7. GRB 260511B SVOM/C-GFT optical counterpart detection
  8. GRB 260510C: AstroSat CZTI detection
  9. GRB 260511B: SVOM detection of a burst
  10. GRB 260511A: SVOM/VT optical observation with VHF data
  11. GRB 260511A: KAIT optical afterglow observations
  12. GRB 260511A: SVOM/COLIBRÍ (FM-GFT) optical counterpart
  13. GRB 260511A: TRT optical counterpart detection
  14. GRB 260511A: SVOM detection of a bright burst
  15. GRB 260510C: SVOM/COLIBRÍ (FM-GFT) optical counterpart candidate
  16. GRB 260510C: MAXI/GSC detection
  17. GRB 260510B: GOTO early upper limit
  18. GRB 260510A: GECAM-B observation
  19. GRB 260509A: KAIT optical observations
  20. GRB 260509A: SVOM/COLIBRÍ (FM-GFT) observations
  21. GRB 260509A: GOTO optical counterpart candidate
  22. GRB 260509A: SVOM detection of a burst
  23. GRB 260506B: AstroSat CZTI detection
  24. EP260507a: REM optical/NIR observations
  25. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  26. EP260507a: COLIBRÍ optical observations
  27. EP260507a: NOT optical observations
  28. EP260507a: GOTO optical counterpart detection
  29. EP260507a: TRT optical counterpart detection
  30. EP260507a: Kinder optical counterpart candidate
  31. GRB 260504B: AstroSat CZTI detection
  32. GRB 260504B: SVOM/ECLAIRs refined analysis
  33. GRB 260506B: Fermi GBM Final Real-time Localization
  34. GRB 260506A: Fermi GBM Final Real-time Localization
  35. GRB 260430B: Glowbug gamma-ray detection
  36. GRB 260504B: SVOM/VT optical upper limits
  37. GRB 260421B: radio observation with the VLA
  38. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  39. Konus-Wind detection of GRB 260504B (short/hard)
  40. GRB 260430B: AstroSat CZTI detection of a long burst
  41. GRB 260504B: SVOM/MXT refined analysis and potential detection
  42. Konus-Wind detection of GRB 260415C
  43. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  44. Konus-Wind detection of GRB 260411C
  45. GRB 260504B: REM optical/NIR observations
  46. IPN triangulation of GRB 260429A
  47. IPN triangulation of GRB 260428A
  48. GRB 260504B: SVOM detection of a short burst
  49. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  50. GRB 260429B / EP260429a: AstroSat CZTI detection
  51. EP260502a: BOOTES-7: early optical upper limit
  52. GRB 260424B: AstroSat CZTI detection
  53. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  54. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  55. GRB 260429A: Fermi GBM Detection
  56. GRB 260428A: AstroSat CZTI detection
  57. Fermi GRB 260428A: Global MASTER-Net observations report
  58. GRB 260424B: Glowbug gamma-ray detection of a short burst
  59. GRB 260424B: COLIBRÍ optical upper limit
  60. Konus-Wind detection of GRB 260424B
  61. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  62. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  63. GRB 260401A: cubesat Avion detection
  64. GRB 260424A: AstroSat CZTI detection of a long burst
  65. GRB 260421B: Kilonova-Catcher optical afterglow detection
  66. The EP-WXT trigger 01709258652: Mondy optical observations
  67. GRB 260421B: SVOM/ECLAIRs refined analysis
  68. EP260416a: ZTSh R band observations
  69. GRB 260419A: AstroSat CZTI detection
  70. GRB 260421B: J-band upper limit with WINTER
  71. GRB 260421B: LCO optical counterpart detection
  72. GRB 260421A: AstroSat CZTI detection
  73. GRB 260412A: SVOM/ECLAIRs refined analysis
  74. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  75. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  76. GRB 260421B: BOOTES-7 early optical afterglow detection
  77. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  78. GRB 260421B: TRT optical counterpart detection
  79. EP260321a: VLA radio follow-up
  80. EP260416a: Optical follow-up observations with Kinder
  81. EP-WXT trigger 01709260303: KAIT optical observations
  82. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  83. EP260416a: Ondrejov D50 optical detection
  84. Konus-Wind detection of GRB 260411B
  85. GRB 260417A: AstroSat CZTI detection
  86. IPN triangulation of GRB 260411B
  87. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  88. EP260417a: TRT optical counterpart detection
  89. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  90. EP-WXT trigger 01709259586: KAIT optical observations
  91. EP260416a: KAIT optical upper limit
  92. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  93. GRB 260415B: Glowbug gamma-ray detection
  94. GRB 260411B: Glowbug gamma-ray detection
  95. EP260416a: COLIBRÍ optical counterpart candidate
  96. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  97. EP260416a: Einstein Probe detection of an X-ray transient
  98. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  99. GRB 260414A: Glowbug gamma-ray detection
  100. EP260321a: CMO SAI J,K observations

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