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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"

23152 results found.

  1. GRB 260509A: GOTO optical counterpart candidate
  2. GRB 260509A: SVOM detection of a burst
  3. GRB 260506B: AstroSat CZTI detection
  4. EP260507a: REM optical/NIR observations
  5. GRB 260507B / EP260507a: Fermi-GBM Sub-Threshold Detection
  6. EP260507a: COLIBRÍ optical observations
  7. EP260507a: NOT optical observations
  8. EP260507a: GOTO optical counterpart detection
  9. EP260507a: TRT optical counterpart detection
  10. EP260507a: Kinder optical counterpart candidate
  11. GRB 260504B: AstroSat CZTI detection
  12. GRB 260504B: SVOM/ECLAIRs refined analysis
  13. GRB 260506B: Fermi GBM Final Real-time Localization
  14. GRB 260506A: Fermi GBM Final Real-time Localization
  15. GRB 260430B: Glowbug gamma-ray detection
  16. GRB 260504B: SVOM/VT optical upper limits
  17. GRB 260421B: radio observation with the VLA
  18. Konus-Wind detection of a burst from SGR 1E1841-045 on 2026 May 2
  19. Konus-Wind detection of GRB 260504B (short/hard)
  20. GRB 260430B: AstroSat CZTI detection of a long burst
  21. GRB 260504B: SVOM/MXT refined analysis and potential detection
  22. Konus-Wind detection of GRB 260415C
  23. GRB 260310A / AT2026fgk: photometric monitoring and tentative maximum of a possible SN
  24. Konus-Wind detection of GRB 260411C
  25. GRB 260504B: REM optical/NIR observations
  26. IPN triangulation of GRB 260429A
  27. IPN triangulation of GRB 260428A
  28. GRB 260504B: SVOM detection of a short burst
  29. EP260502a: BOOTES-7 observations of a fading catalogued source close to the X-ray position
  30. GRB 260429B / EP260429a: AstroSat CZTI detection
  31. EP260502a: BOOTES-7: early optical upper limit
  32. GRB 260424B: AstroSat CZTI detection
  33. GRB 260429B / EP260429a: COLIBRÍ optical upper limit
  34. GRB 260430A / EP260430a: COLIBRÍ optical upper limit
  35. GRB 260429A: Fermi GBM Detection
  36. GRB 260428A: AstroSat CZTI detection
  37. Fermi GRB 260428A: Global MASTER-Net observations report
  38. GRB 260424B: Glowbug gamma-ray detection of a short burst
  39. GRB 260424B: COLIBRÍ optical upper limit
  40. Konus-Wind detection of GRB 260424B
  41. EP260321a/SN 2026gzf: spectroscopy at Mondy observatory
  42. GRB 260305A: likely detection by Fermi-LAT and the LAT gamma-ray position
  43. GRB 260401A: cubesat Avion detection
  44. GRB 260424A: AstroSat CZTI detection of a long burst
  45. GRB 260421B: Kilonova-Catcher optical afterglow detection
  46. The EP-WXT trigger 01709258652: Mondy optical observations
  47. GRB 260421B: SVOM/ECLAIRs refined analysis
  48. EP260416a: ZTSh R band observations
  49. GRB 260419A: AstroSat CZTI detection
  50. GRB 260421B: J-band upper limit with WINTER
  51. GRB 260421B: LCO optical counterpart detection
  52. GRB 260421A: AstroSat CZTI detection
  53. GRB 260412A: SVOM/ECLAIRs refined analysis
  54. GRB 260415A: CALET Gamma-Ray Burst Monitor detection
  55. GRB 260415B: CALET Gamma-Ray Burst Monitor detection
  56. GRB 260421B: BOOTES-7 early optical afterglow detection
  57. GRB 260421B: SVOM/COLIBRÍ (FM-GFT) optical detection of a candidate counterpart
  58. GRB 260421B: TRT optical counterpart detection
  59. EP260321a: VLA radio follow-up
  60. EP260416a: Optical follow-up observations with Kinder
  61. EP-WXT trigger 01709260303: KAIT optical observations
  62. EP260416a: 1.5m OSN and 2.2m CAHA optical monitoring
  63. EP260416a: Ondrejov D50 optical detection
  64. Konus-Wind detection of GRB 260411B
  65. GRB 260417A: AstroSat CZTI detection
  66. IPN triangulation of GRB 260411B
  67. EP260324a / AT2026hir: Further multiband optical follow-up with the PKU 60cm Telescope
  68. EP260417a: TRT optical counterpart detection
  69. EP260416a: refined analysis of the EP-WXT and autonomous EP-FXT observations
  70. EP-WXT trigger 01709259586: KAIT optical observations
  71. EP260416a: KAIT optical upper limit
  72. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  73. GRB 260415B: Glowbug gamma-ray detection
  74. GRB 260411B: Glowbug gamma-ray detection
  75. EP260416a: COLIBRÍ optical counterpart candidate
  76. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  77. EP260416a: Einstein Probe detection of an X-ray transient
  78. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  79. GRB 260414A: Glowbug gamma-ray detection
  80. EP260321a: CMO SAI J,K observations
  81. GRB 260412A: Insight-HXMT/HE detection
  82. GRB 260410A: Glowbug gamma-ray detection of a short burst
  83. Konus-Wind detection of GRB 260410A (short/hard)
  84. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  85. GRB 260412A: GECAM-B observation of a long burst
  86. GRB 260411B: COLIBRÍ optical observations
  87. GRB 260411B: Ondrejov D50 optical afterglow detection
  88. GRB 260409A: Insight-HXMT/HE detection
  89. GRB 260411B: GOTO optical counterpart candidate
  90. GRB 260410A: COLIBRÍ optical upper limit
  91. EP-WXT01709259790: Optical Upper limits with kinder observations
  92. The EP-WXT trigger 01709259790 is likely a flaring star
  93. EP-WXT01709259790: Xinglong optical upper limit
  94. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  95. GRB 260407A: GECAM-A detection
  96. GRB 260407A: Insight-HXMT/HE detection
  97. EP260409a: COLIBRÍ optical upper limits
  98. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  99. EP260321a: VLA radio detection
  100. GRB 260407A: Glowbug gamma-ray detection

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