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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"

23582 results found.

  1. EP260416a: KAIT optical upper limit
  2. EP260416a: COLIBRÍ confirmation of the optical rebrightening
  3. GRB 260415B: Glowbug gamma-ray detection
  4. GRB 260411B: Glowbug gamma-ray detection
  5. EP260416a: COLIBRÍ optical counterpart candidate
  6. COLIBRI optical observations of the transient GOTO26djh/AT2026jpw
  7. EP260416a: Einstein Probe detection of an X-ray transient
  8. GOTO discovery of fast-fading transient GOTO26djh/AT2026jpw, a candidate orphan afterglow
  9. GRB 260414A: Glowbug gamma-ray detection
  10. EP260321a: CMO SAI J,K observations
  11. GRB 260412A: Insight-HXMT/HE detection
  12. GRB 260410A: Glowbug gamma-ray detection of a short burst
  13. Konus-Wind detection of GRB 260410A (short/hard)
  14. GRB 260410A: CALET Gamma-Ray Burst Monitor detection
  15. GRB 260412A: GECAM-B observation of a long burst
  16. GRB 260411B: COLIBRÍ optical observations
  17. GRB 260411B: Ondrejov D50 optical afterglow detection
  18. GRB 260409A: Insight-HXMT/HE detection
  19. GRB 260411B: GOTO optical counterpart candidate
  20. GRB 260410A: COLIBRÍ optical upper limit
  21. EP-WXT01709259790: Optical Upper limits with kinder observations
  22. The EP-WXT trigger 01709259790 is likely a flaring star
  23. EP-WXT01709259790: Xinglong optical upper limit
  24. GRB 260310A/AT2026fgk: Kilonova-Catcher SN peak identification
  25. GRB 260407A: GECAM-A detection
  26. GRB 260407A: Insight-HXMT/HE detection
  27. EP260409a: COLIBRÍ optical upper limits
  28. GRB 260407A: CALET Gamma-Ray Burst Monitor detection
  29. EP260321a: VLA radio detection
  30. GRB 260407A: Glowbug gamma-ray detection
  31. GRB 260402A: SVOM/ECLAIRs refined analysis
  32. GRB 260310A: Continued VLA Multi-frequency Radio Observations
  33. GRB 260310A / AT2026fgk: X-ray rebrightening
  34. EP260402a / GRB 260402A: Mephisto optical upper limits
  35. EP-WXT01709259586: Xinglong optical upper limit
  36. EP260403a: Mephisto optical upper limits
  37. EP260402a/GRB 260402A: Xinglong optical upper limit
  38. EP260321a: Upper limits from VLA radio observations
  39. EP260405a / EP-WXT 11900672904: COLIBRÍ optical upper limits
  40. EP260324A / AT 2026hir: COLIBRÍ further optical observations
  41. GRB 260330B: SVOM/ECLAIRs refined analysis
  42. EP260403a: LCO optical observations of the counterpart
  43. GRB 260310A/AT2026fgk: Kilonova-Catcher long term optical monitoring
  44. EP260403a: LCO optical counterpart detection
  45. EP260403a: COLIBRÍ optical counterpart candidate
  46. GRB 260403A: AstroSat CZTI detection
  47. GRB 260402C: AstroSat CZTI detection of a long burst
  48. EP260324A / AT 2026hir: COLIBRÍ optical observations
  49. GRB 260402A: WINTER J-band upper limit
  50. GRB 260402A: Kilonova-Catcher optical upper limit
  51. GRB 260402A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  52. GRB 260402A: SVOM detection of a burst
  53. GRB 260401A: Fermi GBM Observation
  54. GRB 260401A: CALET Gamma-Ray Burst Monitor detection
  55. GRB 260401A: MAXI/GSC detection
  56. EP260329b: Mondy and Assy-Turgen optical upper limits
  57. EP260321a :Xinglong optical observations
  58. EP260327a: Xinglong optical upper limit
  59. EP260329b: GOTO detection of optical counterpart
  60. Konus-Wind detection of GRB 260320A
  61. Konus-Wind detection of GRB 260316B
  62. GRB 260321A: SVOM/ECLAIRs refined analysis
  63. EP260329b: J-band upper limits with WINTER
  64. EP260329a: J-band upper limit with WINTER
  65. GRB 260330A: Glowbug gamma-ray detection
  66. GRB 260310A: VLA Multi-frequency Radio Observations
  67. EP260329a: COLIBRÍ optical upper limit
  68. EP260329a: NOT optical counterpart candidate
  69. GRB 260327A: Insight-HXMT/HE detection
  70. EP260329b: Optical follow-up with Kinder observations
  71. EP 260329b: COLIBRÍ optical observations
  72. EP260329a: Optical upper limit with Kinder observations
  73. EP260329b: LCO optical observations of the counterpart
  74. EP-WXT trigger 01709259209: TRT optical counterpart detection
  75. The EP-WXT trigger 01709259209 (EP260329b?): Las Cumbres discovery of the optical counterpart
  76. GRB 260310A: Gemini-North Spectral Confirmation of Supernova Features
  77. EP260327a: WINTER J-band upper limit
  78. EP260327a: COLIBRÍ optical upper limits
  79. GRB 260327A: AstroSat CZTI detection of a long burst
  80. GRB 260310A / AT 2026fgk: COLIBRÍ photometric evidence of the emerging supernova
  81. GRB 260310A: OSIRIS+/GTC spectroscopic detection of the associated BL-Ic, SN 2026fgk
  82. GRB 260310A / AT2026fgk: Late-time infrared detection with MIRAGE on the MDM 1.3m telescope
  83. EP260321a: Upper limits from a neutrino search with IceCube
  84. GRB 260310A/AT2026fgk: Kilonova-Catcher late optical afterglow detection at about 15 days post trigger time
  85. IPN triangulation of GRB 260316B
  86. EP260321a: VLT/FORS2 spectroscopy confirmation of an associated type Ic-BL supernova SN 2026gzf
  87. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limits at the FXT positions
  88. EP-WXT trigger 01709259112: confirmation of a stellar flare by BOOTES-5 & BOOTES-7
  89. GRB 260316B: CALET Gamma-Ray Burst Monitor detection
  90. GRB 260310A/AT2026fgk: Detection of temporal steepening in Einstein Probe X-ray data
  91. GRB 260320A: Glowbug gamma-ray detection
  92. EP260321a: COLIBRÍ further optical observations and brightening
  93. EP260321a: Continued brightening from Kinder follow-up of the emerging supernova candidate
  94. EP260214b: ATCA 6 GHz detection
  95. EP260321a: Early TRT rising followed by JinShan decaying and then re-rising
  96. EP260321a: GOTO detection of blue variable source
  97. EP260321a: further Kinder optical observations
  98. GRB 260321A: SVOM/VT optical upper limits
  99. GRB 260321A: SVOM/COLIBRÍ (FM-GFT) optical upper limit
  100. EP260321a: COLIBRÍ optical upper limit on any supernova shock breakout emission

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