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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"

23153 results found.

  1. GRB 260407A: Glowbug gamma-ray detection
  2. GRB 260402A: SVOM/ECLAIRs refined analysis
  3. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  4. GRB 260310A / AT2026fgk: X-ray rebrightening
  5. EP260402a / GRB 260402A: Mephisto optical upper limits
  6. EP-WXT01709259586: Xinglong optical upper limit
  7. EP260403a: Mephisto optical upper limits
  8. EP260402a/GRB 260402A: Xinglong optical upper limit
  9. EP260321a: Upper limits from VLA radio observations
  10. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  11. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  12. GRB 260330B: SVOM/ECLAIRs refined analysis
  13. EP260403a: LCO optical observations of the counterpart
  14. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  15. EP260403a: LCO optical counterpart detection
  16. EP260403a: COLIBRÍ optical counterpart candidate
  17. GRB 260403A: AstroSat CZTI detection
  18. GRB 260402C: AstroSat CZTI detection of a long burst
  19. EP260324A / AT 2026hir: COLIBRÍ optical observations
  20. GRB 260402A: WINTER J-band upper limit
  21. GRB 260402A: Kilonova-Catcher optical upper limit
  22. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  23. GRB 260402A: SVOM detection of a burst
  24. GRB 260401A: Fermi GBM Observation
  25. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  26. GRB 260401A: MAXI/GSC detection
  27. EP260329b: Mondy and Assy-Turgen optical upper limits
  28. EP260321a :Xinglong optical observations
  29. EP260327a: Xinglong optical upper limit
  30. EP260329b: GOTO detection of optical counterpart
  31. Konus-Wind detection of GRB 260320A
  32. Konus-Wind detection of GRB 260316B
  33. GRB 260321A: SVOM/ECLAIRs refined analysis
  34. EP260329b: J-band upper limits with WINTER
  35. EP260329a: J-band upper limit with WINTER
  36. GRB 260330A: Glowbug gamma-ray detection
  37. GRB 260310A: VLA Multi-frequency Radio Observations
  38. EP260329a: COLIBRÍ optical upper limit
  39. EP260329a: NOT optical counterpart candidate
  40. GRB 260327A: Insight-HXMT/HE detection
  41. EP260329b: Optical follow-up with Kinder observations
  42. EP 260329b: COLIBRÍ optical observations
  43. EP260329a: Optical upper limit with Kinder observations
  44. EP260329b: LCO optical observations of the counterpart
  45. EP-WXT trigger 01709259209: TRT optical counterpart detection
  46. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  47. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  48. EP260327a: WINTER J-band upper limit
  49. EP260327a: COLIBRÍ optical upper limits
  50. GRB 260327A: AstroSat CZTI detection of a long burst
  51. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  52. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  53. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  54. EP260321a: Upper limits from a neutrino search with IceCube
  55. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  56. IPN triangulation of GRB 260316B
  57. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  58. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  59. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  60. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  61. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  62. GRB 260320A: Glowbug gamma-ray detection
  63. EP260321a: COLIBRÍ further optical observations and brightening
  64. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  65. EP260214b: ATCA 6 GHz detection
  66. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  67. EP260321a: GOTO detection of blue variable source
  68. EP260321a: further Kinder optical observations
  69. GRB 260321A: SVOM/VT optical upper limits
  70. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  71. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission
  72. GRB 260321A: SVOM detection of a burst
  73. EP260321a: Kinder observations detect a blue variable star and set limits on a source from the z =0.034 galaxy within the error circle
  74. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS new optical observations
  75. GRB 260318A: Glowbug gamma-ray detection
  76. GRB 260310A / AT 2026fgk: KAIT optical observations
  77. EP-WXT trigger 01709258989: KAIT confirmation of a stellar flare
  78. GRB 260310A / AT 2026fgk: COLIBRÍ evidence of a late rebrightening
  79. EP-WXT trigger 01709258989: confirmation of a stellar flare by BOOTES-7
  80. GRB 260316A / EP260316a: COLIBRÍ optical followup of counterpart candidate
  81. GRB 260310A / AT 2026fgk: radio detection with the VLA
  82. GRB 260310A / AT2026fgk: LCO optical observations
  83. EP260316a: COLIBRÍ faint optical counterpart candidate
  84. GRB 260316B: AstroSat CZTI detection
  85. EP260316a: Xinglong optical upper limit
  86. EP260316a: optical upper limit with Kinder observations
  87. EP260316a / GRB 260316A : Fermi-GBM Sub-Threshold Detection
  88. GRB 260314A: Glowbug gamma-ray detection
  89. IceCube-260315A: COLIBRÍ optical observations
  90. EP260314a: Xinglong optical upper limit
  91. EP260314a: optical upper limit with Kinder observations
  92. GRB 260310A / AT2026fgk: ABObservatory and NOCTIS optical observations
  93. GRB 260310A / AT 2026fgk: iTelescope optical observations
  94. EP260314a: COLIBRÍ optical upper limit
  95. EP260314a: BOOTES-6/DPR optical upper limits at early times
  96. GRB 260310A / AT2026fgk: SAO RAS optical observations
  97. GRB 260310A / AT2026fgk: TNG NIR detection
  98. GRB 260310A / AT2026fgk: OASDG optical observations
  99. GRB 260310A / AT2026fgk: Multiband optical follow-up with Kinder observations
  100. GRB 260310A / AT 2026fgk: COLIBRÍ continuing optical observations

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